Kondo effect in a quantum antidot

We report Kondo-like behavior in a quantum antidot (a submicron depleted region in a two-dimensional electron gas) in the quantum-Hall regime. When both spins of the lowest Landau level are present all around the antidot, the resonances between extended edge states via antidot bound states show an abnormal feature in alternate Coulomb-blockaded regions. The feature becomes suppressed when the temperature or source-drain bias is raised as for Kondo resonances in quantum dots. Although the exact mechanism is unknown, Kondo-like correlated tunneling may arise from a Skyrmion-type edge reconstruction. This observation demonstrates the generality of the Kondo phenomenon.     

Achievement of a 920-MHz high resolution NMR

We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR.     

Masking effect of potassium iodide on the interferences in the atomic-absorption spectrophotometric determination of antimony utilizing stibine generation by sodium borohydride tablet reduction

Summary The masking effect of potassium iodide with or without hydroxylamine on the interferences in the atomic-absorption spectrophotometric determination of antimony via its hydride by sodium borohydride tablet reduction has been studied. It has been well known in the conventional colorimetric method [21] that both potassium iodide and stannous chloride completely suppress the evolution of stibine. However, in this sodium borohydride tablet reduction, potassium iodide plays a role in masking the interferences of not only stannous chloride but also other numerous ions. By the procedure established here, the calibration curve was linear up to a concentration of 0.04g/ml of antimony with the coefficient of variation of 2.4 %. The method was successfully applied to the determination of antimony in a river sediment.

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Maskierende Wirkung von Kaliumiodid auf Störungen bei der AAS-Bestimmung von Antimon durch Stibinerzeugung mit Hilfe der Natriumborhydridreduktion

Zusammenfassung Es ist bekannt, daß bei der colorimetrischen Bestimmungsmethode [21] sowohl KI als auch SnCl₂ die Entwicklung von Stibin vollständig verhindern. Bei der hier beschriebenen Reduktion mit Hilfe einer NaBH₄-Tablette maskiert jedoch KI (mit oder ohne Hydroxylaminzusatz) Störungen durch SnCl₂ sowie durch zahlreiche andere Ionen. Die Eichkurve verläuft bis zu 0,04 g Sb/ml linear. Der Variationskoeffizient beträgt 2,4 %. Als Anwendungsbeispiel wird die Antimonbestimmung in Flußsedimenten erwähnt.

     

New bis- and tris-annulation reagents for the syntheses of CD rings of steroids,bearing a functionalized 18-methyl group,by the palladium-catalyzed cyclization

2-Substituted 2-alkoxycarbonyl-3-vinylcyclopentanones (2), easily prepared by the palladium-catalyzed cyclization of 2-substituted 3-oxo-8-phenoxy-6-octenoates (1), are very suitable building blocks for CD rings of steroids, bearing particularly a functionalized 18-methyl group.     

Stereospecific photocyclization of α-bisulfenylated keto compounds. Cis-dihydrobenzothiophenes

Irradiation of α-bisulfenylated keto compounds in acetonitrile affords the cis-fused dihydrobenzothiophenes which are dehydrated to benzothiophenes in high yields.     

Prostaglandin analogs modified at the 10 and 11 positions

A simplified methodology for the building of prostaglandins substituted at the 10 and 11 positions is presented.