The Preparation and Characterization of Highly Dispersed PdO over Alumina for Low‐temperature Combustion of Methane

PdO/Al₂O₃ catalysts prepared by glow discharge plasma treatment followed by thermal calcination show a much higher dispersion and a better catalytic activity for methane combustion at relatively low temperatures. The dispersion of palladium active species by such plasma prepared catalysts is 29.7%, 5.4 times higher than that of conventional catalysts. XPS analysis indicates that a surface enrichment of Pd active species (PdO) has been achieved after plasma treatment. The surface atomic composition of PdO of plasma prepared catalysts reaches 10.5%. XRD characterization also confirms a wellcrystallized PdO phase present on the plasma prepared catalyst. The lightoff temperature of the plasma prepared catalyst is 370°C, 50°C lower than that obtained from the conventional catalyst.     

BILDUNG UND SPALTUNG VON 3-THIETANON

Abstract

3-Thietanone (3a) reacts rapidly with methanolic sodium hydrogen sulfide to form a mixture of products wherein 2,4-dimethylthiophene-3-thiol (9), the corresponding disulfide (10) and 3,6-dimethyl-7-oxa-2,5-dithiabicyclc [2.2.1]-heptane (7) could be detected. These products are explained to be derived from the unstable 1-mercapto-2-propanone (5) formed by reductive cleavage of the thietanone ring. The cleavage is postulated to occur by attack of hydrogensulfide ion at the ring sulfur. 3-Thietanone can be synthesized from 3-thietanol by oxidation with dimethyl sulfoxide/benzoic acid anhydride.

3-Thietanon (3a) reagiert rasch mit methanolischem Natriumhydrogensulfid zu einem Produktgemisch, in dem 2,4-Dimethylthiophen-3-thiol (9), das entsprechende Disulfid (10) und 3,6-Dimethyl-7-oxa-2,5-dithiabicyclo [2.2.1]-heptan (7) nachgewiesen werden konnten. Diese Produkte lassen sich aus dem instabilen 1-Mercapto-2-propanon (5) ableiten, welches durch reduktive Spaltung des Thietanon-Ringes gebildet wird. Für die Spaltung wird ein Angriff des Hydrogensulfidions am Ringschwefel postuliert. 3-Thietanon kann aus 3-Thietanol durch Oxidation mit Dimethyl-sulfoxid/Benzoesäureanhydrid synthetisiert werden.     

Theory of cavitons in complex plasmas

Nonlinear coupling between Langmuir waves with finite amplitude dispersive dust acoustic perturbations is considered. It is shown that the interaction is governed by a pair of coupled nonlinear differential equations. Numerical results reveal the formation of Langmuir envelope solitons composed of the dust density depression created by the ponderomotive force of bell-shaped Langmuir wave envelops. The associated ambipolar potential is positive. The present nonlinear theory should be able to account for the trapping of large amplitude Langmuir waves in finite amplitude dust density holes. This scenario may appear in Saturn's dense rings, and the Cassini spacecraft should be able to observe fully nonlinear cavitons, as presented herein. Furthermore, we propose that new electron-beam plasma experiments should be conducted to verify our theoretical prediction.     

Application of microbioreactors in fermentation process development: a review

Biotechnology process development involves strain testing and improvement steps aimed at increasing yields and productivity. This necessitates the high-throughput screening of many potential strain candidates, a task currently mainly performed in shake flasks or microtiter plates. However, these methods have some drawbacks, such as the low data density (usually only end-point measurements) and the lack of control over cultivation conditions in standard shake flasks. Microbioreactors can offer the flexibility and controllability of bench-scale reactors and thus deliver results that are more comparable to large-scale fermentations, but with the additional advantages of small size, availability of online cultivation data and the potential for automation. Current microbioreactor technology is analyzed in this review paper, focusing on its industrial applicability, and directions for future research are presented.     

Design of donor–acceptor–donor (D–A–D) type small molecule donor materials with efficient photovoltaic parameters

Four Donor–Acceptor–Donor (D–A–D) type of donor molecules (M1‐M4) with triphenylamine (TPA) as donor moiety, thiophene as bridge, and thiazolothiazole as acceptor unit were designed and its photovoltaic parameters were equated with reference molecule “R.” DFT functional CAM‐B3LYP/6‐31G (d,p) was found best for geometry optimization and TD‐CAM‐B3LYP/6‐31G (d,p) was found suitable for excited state calculations. Among designed donor molecules, M4 manifests suitable lowest band gap of 4.73 eV, frontier molecular orbital energy levels as well as distinctive broad absorption of 455.3 nm due to the stronger electron withdrawing group. The electron‐withdrawing substituents contribute to red shifts of absorption spectra and better stabilities for designed molecules. The theoretically determined reorganization energies of designed donor molecules suggested excellent charge mobility property. The lower λ_e values in comparison with λ_h illustrated that these four donor materials would be ideal for electron transfer and M4 would be best amongst the investigated molecules with lowest λ_e of 0.0177. Furthermore, the calculated Voc of M4 is 2.04 V with respect to PC₆₀BM (phenyl‐C61‐butyric acid methyl ester). This study revealed that the designed donor materials are suitable and recommended for high performance organic solar cell devices.