Vacuum energies in dimensionally reduced supersymmetric theories

We demonstrate how supersymmetric theories cancel the appearance of unwanted cosmological constants that arise when considering the quantum behaviour of dimensionallu reduced theories. However the cancellation only works in standard supersymmetric theories if the dimensional reduction is over circular “extra” dimensions.     

Ag−Sn Alloys and dental amalgams: A119Sn Mössbauer,x-ray diffraction and scanning electron microscopy study

Examination has been made on aged and fresh Ag?Sn alloys and on commercial Cu?Ag?Sn dental alloys. Although x-ray diffractograms of aged Ag?Sn showed only λ Ag?Sn and free silver,¹¹⁹Sn Mössbauer spectra exhibited Sn(IV) oxide also. A low Debye temperature showed the oxide to be in intimate dynamical contact with the metallic matrix. Upon adding mercury, the phases λ₁ Ag?Hg and η′ Cu?Sn were observed in a commercial specimen. Conversion-electron spectra of a mercury-coated disk showed the presence of λ₂ Sn?Hg and a distribution of line positions smaller than that for particulate amalgams. Internal oxidation was found to prevent amalgamation.     

Hydrogen reduction of fine iron-oxide particles

Crystallographic, magnetic, and morphological changes induced by heating highly acicular -Fe₂O₃ particles (40 nm in diameter and an axial ratio of 8) under hydrogen have been observed. Reduction proceeds via a multi-phase process, and is not complete until 600°C. The -Fe particles produced are cylindrical in shape, 100 nm in diameter, and have an axial ratio of 1.7(3). Fourier analysis of x-ray profiles yielded a mean column length of 105(6) nm perpendicular to (110). Mössbauer spectra show two distinct hyperfine fields; at room temperature the values are 33.1(1) and 30.2(1)T. Evidence for diffusive particle motion is not present in 4.2–300 K spectra.     

4-(2-Pyridylazo)-resorcinol as a possible analytical reagent for the colorimetric estimation of cobalt,lead, and uranium ,

4-(2-Pyridylazo)-resorcinol has been synthesized, and its uses as an analytical reagent for the colorimetric estimation of cobalt, uranium and lead have been investigated. It has been shown to be the most sensitive reagent for the colorimetric estimation of cobalt, the most sensitive watersoluble reagent for the colorimetric estimation of uranium, and the first published water-soluble reagent for the colorimetric estimation of lead.     

A convenient preparation of thioether functionalized porphyrins

This paper describes a convenient and high yielding three-step approach for the synthesis of trans-tetraphenylporphyrins possessing two thioethers in the ortho positions, which will facilitate the synthesis of more elaborate and complex porphyrin architectures. Their synthesis is realized by a double nucleophilic aromatic substitution of 2 equiv of a thiolate on 2,6-dichlorobenzaldehyde to generate a bis-thioether substituted benzaldehyde. This aldehyde is then condensed with 2 equiv of pyrrole to give a dipyrromethane, which in the final step reacts with an aromatic aldehyde to give a series of thioether-substituted trans-tetraphenylporphyrins.     

Mercury exchange between diphenylmercury and bis(p-chlorophenyl)mercury

Experimental methods for investigating mercury exchange between diphenyl mercury and bis(p-chlorophenyl)mercury have been evaluated and kinetic parameters determined using a novel partition technique. An octahedral transition state has been proposed. The investigation was complicated by a relatively fast reaction rate, and the kinetic interference of impurities or hydrolysis products.     

The calibration of a micrometer eyepiece for the determination of 2 E

Summary A simple method for the determination of optic axial-angles of crystals and the determination of numerical aperture of dry objectives is described. It requires the use of graph paper and of a microscope equipped with aBertrand lens and an ocular micrometer.

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Zusammenfassung Eine einfache Methode für die Bestimmung optischer Achsenwinkel von Kristallen und der numerischen Öffnung von Trockenobjektiven wird beschrieben. Sie benötigt nur Millimeterpapier und ein mit einerBertrandschen Linse und einem Okularmikrometer versehenes Mikroskop.

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Résumé On décrit une simple méthode afin de déterminer d'angles axiaux optiques, ou d'ouvertures numériques d'òbjectifs secs. Elle inclut l'emploi de papier millimétré et d'un microscope fourni d'une linseBertrand et d'un micromètre oculaire.

     

Structural requirements for efficient photoinduced electron transfer (PET) quenching in 9-aminoalkylanthracenes

The structure-quenching relationship in 9-aminoalkylanthracenes is examined by the synthesis and fluorescence evaluation of five derivatives; it is observed that benzylic 2° and 3° amines lead to 95% quenching of anthracene fluorescence in water, while other amines afford substantially lower quenching efficiencies.