An observation on the origin of secondary flow in straight noncircular ducts

This note is concerned with the origin of secondary flow in straight noncircular ducts. A critical examination of the analytical expressions for the secondary flow production terms is made to show that the essential requirement for secondary flow is a finite gradient of the difference in the turbulent stresses in the plane of the duct cross section in a peripheral direction. This conclusion has been reached following an investigation of the turbulent stress distributions in unidirectional pipe flow and assumes that, in general, the normal stresses only are significant in secondary flow production. An observation is made on “vorticity reversal” in the immediate vicinity of the boundary of a noncircular duct.     

Standing wave treatment applied to 3-level bistable system

A c-number treatment for the standing (plane) wave effects in a bistable system placed in a Fabry-Perot cavity is employed without “truncation of hierarchy” or “spatial average” procedure. The specific example of the 3-level Lambda-shape (two-photon) system is illustrated.     

Mit Phosphorsäure behandelte natürliche Tonerdesilicate als Katalysatoren für das Alkylieren

Ohne Zusammenfassung     

Characterization and determination of benzalmalonitriles using infrared,nuclear magnetic resonance and mass spectrometry

Summary The stretching vibration of the CN groups at 2200–2240 cm^–1 and the singlet signal of the olefinic proton at 7–9 ppm in the IR and NMR spectra of benzalmalonitriles are correlated with Hammett sigma parameter of the substituents and the data obtained are used for their selective characterization. Using the base-line method and KBr technique or dimethylsulfoxide solvent and the integration method, 50–800g/250 mg KBr or 10–100 mg/ml of these compounds are quantitated by IR and NMR, respectively. The average recovery by both methods is 98.3% (st. dev. 1.6%). Fragmentation of these compounds using mass spectrometry gives common products that can be used for their characterization.

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Charakterisierung und Bestimmung von Benzalmalonitrilen mittels Infrarot-, Kernresonanz- und Massenspektrometrie

Zusammenfassung Die Valenzschwingung der CN-Gruppen bei 2200–2240 cm^–1 und das Singulettsignal des olefmischen Protons bei =7–9 ppm in den IR-bzw. NMR-Spektren von Benzalmalonitril wurden mit Hammett Sigma Parametern der Substituenten korreliert und die erhaltenen Daten zur selektiven Charakterisierung herangezogen. Unter Verwendung der Basislinien-methode und der Kaliumbromidtechnik bzw. Dimethylsulfoxid als Lösungsmittel und der Integrationsmethode wurden 50–800g/250 mg KBr bzw. 10–110 mg/ml dieser Verbindungen durch IR-bzw. NMR-Spektroskopie quantifiziert. Die durchschnittliche Wiedergewinnungsrate betrug bei beiden Methoden 98,3% (Standardabweichung 1,6%). Die Fragmentierung dieser Verbindungen mittels Massenspektrometrie ergibt Produkte, die zur weiteren Charakterisierung herangezogen werden können.

     

Determination of penicillins by desulphurization with lead and edta titration

A new, simple, accurate and rapid method is described for the determination of total penicillins in pharmaceutical preparations. The method is based on desulphurization with potassium plumbite whereby one mole of lead sulphide is formed per mole of penicillin. The excess of lead ions is titrated with EDTA at pH 4.5, with use of the lead ion-selective electrode. Results are reproducible within +/- 0.5% and compare favourably with those obtained by the procedures of the United States and British Pharmacopoeias.     

Reactivity of 6-anisyl-5-cyano-4-oxo-2-thioxo-1,2,3,4-tetrahydro-pyrimidine to wards some electrophiles and nucleophiles

The title compound was subjected to react with some electrophiles and nucleophiles, such as alkyl halides, ethyl chloroacetate or amines, hydrazines etc. The resulting compounds were used in further syntheses for the purpose of obtaining some new types of heterocycles with possible biological and pharmaceutical activities.     

The spectrum of combustion-generated noise

A calculation of the energy release rate resulting from the combustion of propane-air mixtures is presented and the result is used to calculate the far field noise spectrum for an open flame by using appropriate Fourier transform techniques. The results illustrate the broad band nature of combustion noise and show that, for the range of parameters indicated, the peak frequency in the $\text{1}\text{3}$ octave band is in the range 400–1000 Hz. The results also indicate that the shape of spectrum is influenced by the time history of the heat release rate and the turbulence intensity and length scales; on the other hand, the peak frequency is a function of the heat release per unit mass of fuel which is essentially the same for hydrocarbon fuels.