A numerical study of heat and momentum transfer for tube bundles in crossflow

A numerical scheme is developed to predict the heat transfer and pressure drop coefficients in flow through rigid tube bundles. The scheme uses the Galerkin finite element technique. The conservation equations for laminar steady-state flow are cast in the form of streamfunction and vorticity equations. A Picard iteration method is used for the solution of the resulting system of non-linear algebraic equations. Results for the heat transfer and pressure drop coefficients are obtained for tube arrays of pitch ratios of 1·5 and 2·0. Very good agreement of the present results and experimental data obtained in the past is observed up to Reynolds numbers of 1000. It is also observed that the results of the present method show better agreement with the experimental data and that they are applicable for higher Reynolds numbers than results of other studies.     

The preparation of triazines and benzimidazoles from 1- and 3-cyanoisoquinolines

The preparation from 1- and 3-cyanoisoquinolines of certain benzimidazoles and symmetrical triazines containing the ferroin group is described; also that of certain unsymmetrical triazines from 3-cyanoisoquinoline.     

Vinamidines and Vinamidinium Salts—Examples of Stabilized Push-Pull Alkenes

The name vinamidines has been proposed for 1,5-diazapentadienes: these compounds can be regarded as vinylogous amidines and at the same time as push-pull substituted (and thereby stabilized) alkenes. Vinamidine and vinamidinium structural elements may also form part of a ring system. Characteristic of this class of compounds are their reactivity toward electrophiles (at C_β) and nucleophiles (C_α) and their regenerative character, i.e. their tendency to undergo substitution instead of addition reactions. Reactions of vinamidinium salts with nucleophiles are of special preparative value: they lead e.g. to pyrazoles, oxazoles, pyrimidines, diazepines, quinolines, and quinolizines.     

Infrared spectra for a multi discipline spectroscopy system

Summary The infrared spectra quality requirements of the Spektrendatenbanken-Verbundsystem (SDVS) are reported with special reference to Expert System needs. Some of the potential benefits of the system are given. A Call for Spectra is made and the guidelines for submitting spectra to the database outlined.

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Infrarotspektren für ein multidisziplinäres Spektroskopie-System

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

Synthesis, characterization, and cytotoxicity of a novel highly charged trinuclear platinum compound. Enhancement of cellular uptake with charge

Charge delocalization (6+ to 8+) in "noncovalent" linear trinuclear platinum complexes produces compounds with cytotoxicity in some cases equivalent to cisplatin. The cellular uptake of a novel 8+ compound is greater than that of neutral cisplatin as well as other multinuclear Pt compounds.     

Enclathration of morpholinium cations by Dianin's compound: salt formation by partial host-to-guest proton transfer

In spite of partial deprotonation upon inclusion of morpholine, Dianin's compound maintains its well-known clathrate structure in the solid state.     

Organic crystals absorb hydrogen gas under mild conditions

We have studied the hydrogen sorption on three well-known organic hosts that possess vacant lattice voids large enough to accommodate H2 molecules.