Penicillin-cephalosporin conversion X. New synthesis of dithioazetidinones from thiazoline-azetidinones

New ring-opening reaction of thiazoline-azetidinones 1 to dithioazetidinones 2 was achieved with 2-benzothiazolyl disulfide in aqueous acidic media and its potentiality for the preparation of a variety of cephalosporins 3 from various thiazoline-azetidinones 1 is demonstrated.     

A new synthesis of pyrroles by the condensation of cyclopropenes and nitriles mediated by gallium(III) and indium(III) salts

Gallium(III) and indium(III) halides were found to mediate the condensation of cyclopropenes and nitriles to give pyrrole derivatives in moderate yields. When excess nitrile was present, diazepine was also formed.     

Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.     

Photoluminescence of bis(8-hydroxyquinoline) zinc (Znq2) and magnesium (Mgq2)

Absorption and photoluminescence (PL) spectra, PL quantum efficiency, and PL lifetime have been investigated on bis(8-hydroxyquinoline) zinc (Znq₂) and magnesium (Mgq₂) in solutions and powder. Znq₂ and Mgq₂ have the lowest-energy absorption band at 376 and 396 nm in acetonitrile solution, respectively, and emission band with peak at 555 and 480 nm. The PL quantum efficiency is 0.03 and 0.45 for Znq₂ and Mgq₂ in the solution, respectively, while 0.45 and 0.36 in powder. Unlike the case of powders, two PL lifetimes are obtained in solutions. The longer lifetime is attributed to molecule having interaction with its neighboring molecule, while the shorter one to the isolated single molecule.     

The ASACUSA CUSP: an antihydrogen experiment

In order to test CPT symmetry between antihydrogen and its counterpart hydrogen, the ASACUSA collaboration plans to perform high precision microwave spectroscopy of ground-state hyperfine splitting of antihydrogen atom in-flight. We have developed an apparatus (“cusp trap”) which consists of a superconducting anti-Helmholtz coil and multiple ring electrodes. For the preparation of slow antiprotons and positrons, Penning-Malmberg type traps were utilized. The spectrometer line was positioned downstream of the cusp trap. At the end of the beamline, an antihydrogen beam detector was located, which comprises an inorganic Bismuth Germanium Oxide (BGO) single-crystal scintillator housed in a vacuum duct and surrounding plastic scintillators. A significant fraction of antihydrogen atoms flowing out the cusp trap were detected.     

Chemical properties of water-soluble,nonionic azo compounds as initiators for emulsion polymerization

Four kinds of water-soluble, nonionic azo compounds were studied in terms of their decomposition rate and initiator efficiency in radical polymerization, and then used for emulsion polymerization. They had relatively low initiator efficiency from 0.09 to 0.46. It was attributed to the susceptibility to a cage effect, depending on their molecular size and hydrophobicity. Four azo compounds initiated emulsion polymerization but nonionic latex particles were not obtained unexpectedly. Methanol-containing medium results in the formation of a bimodal particle size distribution as well as a bimodal molecular weight distribution. © 1996 John Wiley & Sons, Inc.     

Landau levels in a novel two-dimensional electron system interacting with charged quantum dots

Landau levels have been theoretically investigated in a two-dimensional electron gas near a quantum dot (QD) layer. By a diagrammatical method, we have formulated the self-energy for the Landau level and deduced its relation to the AC conductivity σ_loc(ω) in the QD layer. As an example, we have examined the density of states in the case where σ_loc(ω) is described by Aω^S(S=0.8). It is found that the Landau levels are broadened due to the interaction with the localized electrons in the QDs.