Effect of surface roughness on the aerodynamics of a high-speed train subjected to crosswinds

Acta Mechanica Sinica - The irregularities on trains bodies are normally ignored or greatly simplified in studies concerned with aerodynamics. However, surface roughness is known to affect the flow...     

Experimental studies on solid state electrical double layer capacitors using activated charcoal powder electrodes and PVdF-HFP based gel electrolytes

Ion conducting polymeric gel electrolytes, based on poly vinylidine fluoride-co-hexafluropropylene (PVdF-HFP)-ethylene carbonate (EC)-propylene carbonate (PC)-salts, LiClO₄, NaClO₄ and (C₂H₅)₄NClO₄ (TEAClO₄), have been used in the fabrication of solid state electrical double layer capacitors (EDLCs) with activated charcoal powder electrodes. Comparative studies of different capacitor cells with different gel electrolytes have been carried out using a.c. impedance analysis, linear sweep-reversal voltammetry and galvanostatic charge-discharge techniques. The large values of overall capacitance of 50–100 mFcm⁻² (equivalent to single electrode specific capacitance 50–77 Fg⁻¹ of carbon) have been achieved. This corresponds to the energy density 1.6–2.7 Whkg⁻¹. The values of the capacitance have been found to be almost stable up to 5000 voltammetric cycles. The comparative studies of different capacitor cells indicate that the charging processes and hence the coulombic efficiencies are highly affected by the size of the ions, accumulated at the interfaces of EDLCs.     

Gold catalysis: efficient synthesis and structural assignment of jungianol and epi-jungianol

Starting from 2-methylfuran and crotonaldehyde, both jungianol and epi-jungianol were prepared by a six-step sequence including a gold-catalyzed arene synthesis and a photochemical S(N)2-like reduction with lithium aluminum hydride. Not a single protective group was needed in the entire synthesis. With both diastereomers in hand, the stereochemical assignment in the literature could be corrected by means of a thorough (1)H NMR spectroscopic analysis and an X-ray diffraction study on an epi-jungianol derivative.     

Paper chromatography of fatty acids and halogenated organic acids

A paper chromatographic method is described for the identification of the volatile fatty acids and some of their bromo- and iodo-derivatives. Some new spraying reagents are suggested which enable the different classes of acids to be detected in presence of one another.     

Microdetermination of ascorbic acid and tryptophan by colorimetry

Summary Ascorbic acid reacts with 2,3,5-triphenyltetrazolium chloride in alkaline medium giving pink color having 5g/ml as visual limit of identification. This color reaction has been utilized for the colorinietric determination of ascorbic acid from pharmaceutical preparations in minute quantities. The maximum tolerable amount of other vitamins, sugars and organic compounds during determination of ascorbic acid is reported.Tryptophan reacts with hexamine to give yellow color having 5g/ml as limit of identification. The color reaction provides the basis of a new method for colorimetric determination of tryptophan. The maximum tolerable amount of various amino acids and vitamins is reported. The mechanism of the color reaction is not clear.

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Zusammenfassung Ascorbinsäure reagiert mit 2,3,5-Triphenyrtetrazoliumchlorid in alkalischem Milieu unter Rosafärbung. Erfassungsgrenze: 5g/ml. Diese Farbreaktion wurde zur kolorimetrischen Bestimmung kleiner Mengen Ascorbinsäure in pharmazeutischen Präparaten verwendet. Die tolerierbare Höchstmenge an anderen Vitaminen, Zuckern und organischen Verbindungen wurde angegeben. Tryptophan reagiert mit Hexamin unter Gelbfärbung. Erfassungsgrenze: 5g/ml. Die Farbreaktion dient als neue Methode zur kolorimetrischen Tryptophanbestimmung. Die nicht störenden Höchstmengen an anderen Aminosäuren und Vitaminen sind angegeben. Der Reaktionsmechanismus ist nicht geklärt.