Photoluminescence excitation spectroscopy of GaP1−xNx alloys: conduction-band-edge formation by nitrogen incorporation

We have investigated the conduction-band-edge formation in GaP_1−xN_x alloys by nitrogen incorporation into GaP using photoluminescence excitation (PLE) spectroscopy. The PLE spectra of GaP_1−xN_x alloys with various nitrogen concentrations show that the absorption edge shifts to lower energies with increasing nitrogen concentration. From the nitrogen concentration dependence of the absorption edge energy we found that the conduction-band-edge formation in GaP_1−xN_x alloys originates from the formation of the A line.     

Spectrophotometric determination of nitrite produced by flow-electrolysis of nitrate

Summary The electrocatalytic reduction of nitrate to nitrite with a carbon column electrode in the presence of Cu²⁺ and Cd²⁺ was investigated in a flow system. Electrogenerated nitrite was mixed with colour-producing reagents and detected colorimetrically. In acetate and phosphate buffer solutions, the reduction of nitrate to nitrite or further reduction of nitrite was monitored by scanning the electrode potential. In phosphate buffer solution, the yield of nitrite went up to a maximum in the presence of Cu²⁺ and Cd²⁺ at about –1.1V. The electrocatalytic reduction method was applied to the determination of nitrate in river water instead of the conventional Cu-coated Cd column.

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Spektralphotometrische Bestimmung von Nitrit, das durch Durchfluß-Elektrolyse von Nitrat erzeugt wurde

Zusammenfassung Die elektrokatalytische Reduktion von Nitrat zu Nitrit mit Hilfe einer Kohlenstoff-Säulenelektrode in Gegenwart von Cu²⁺ und Cd²⁺ wurde in einem Durchflußsystem untersucht. Das erzeugte Nitrit wurde mit Farbreagentien versetzt und colorimetrisch bestimmt. In Acetat- und Phosphatpufferlösungen wurde die Reduktion von Nitrat zu Nitrit sowie dessen weitere Reduktion mit Hilfe des Elektrodenpotentials verfolgt. Bei –1,1 V in Phosphatpuffer erreicht die Ausbeute an Nitrit in Gegenwart von Cu²⁺ und Cd²⁺ ein Maximum. Die elektrokatalytische Reduktionsmethode wurde an Stelle des konventionellen Verfahrens mit einer Cd-Säule mit Cu-Überzug zur Nitratbestimmung in Flußwasser angewendet.

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This research was supported by Grant-in-Aid for Scientific Research No. 57740288 from the Ministry of Education, Science and Culture of Japan.     

Induced antiferroelectric smectic- C(*)(A) phase by doping ferroelectric- C* phase with bent-shaped molecules

Doping of the ferroelectric Sm-C(*) phase with bent-shaped molecules induces the antiferroelectric Sm-C(*)(A) phase. The effect was observed by means of electro-optic and dielectric measurements in systems with weak interlayer interactions in which the relative strength of anticlinic-synclinic order between molecules in adjacent layers is easily controlled by external factors. Fourier-transform infrared spectroscopy studies suggest that the bent-shaped molecules are not flat. They reorient upon the electric field-induced antiferroelectric-ferroelectric transition to adopt a position in which the average direction of the carbonyl groups is in the smectic plane and a bending tip along the C2 symmetry axis.     

Maskless microfabrication of thermosensitive gels using a microscope and application to a controlled release microchip

Here we show a simple and convenient method to prepare micropatterned gels by the use of a microscope, without large-scale or special-order experimental setup. UV light focused by an objective lens was locally irradiated to a pre-gel solution in a microchannel. This method would be useful for preparing microgels at target positions in microchips. A controlled drug-release microchip has actually been fabricated by utilizing this local photo-irradiation method, and pulsatile drug release in response to temperature changes was demonstrated.     

Copper-catalyzed carboxylation of alkylboranes with carbon dioxide: formal reductive carboxylation of terminal alkenes

Carboxylation of alkylboron compounds (alkyl-9-BBN) with CO(2) proceeded in the presence of catalytic amounts of CuOAc/1,10-phenanthroline and a stoichiometric amount of KO(t)Bu. The alkylboranes are easily and widely available through the alkene hydroboration, and thus the overall process represents a reductive carboxylation of alkenes with CO(2). The broad functional group compatibility and the inexpensiveness of the Cu/1,10-phenathoroline catalyst system are attractive features of this protocol.     

Preparation of titania particles utilizing the insoluble phase interface in a microchannel reactor

A stable interface between two insoluble currents in a microchannel reactor has been obtained by selecting the solvents and adjusting the flow rate; titania particles with a size of less than 10 nm could be prepared continuously on this interface; this new method shows great advantage for the control and measurement of particle sizes.     

Characteristic features in the collision of chemical waves depending on the aspect ratio of a rectangular field

The photosensitive Belousov-Zhabotinsky (BZ) reaction was investigated on a double rectangular field composed of two rectangular routes, which was drawn using computer software and then projected using a liquid-crystal projector on a filter paper soaked with BZ solution. When two chemical waves were generated on the rectangular routes as the initial condition, the nature of the collision of the waves could be theoretically classified into four categories depending on the initial phase difference between the two waves and the aspect ratio of the rectangular routes. The experimental results were consistent with the features of the theoretical prediction. These results suggest that the feature of wave propagation characteristically develops depending on the geometry of the excitable fields.     

Total syntheses of (-)- and (+)-goniomitine

The Stille coupling reaction of 3-(benzyloxymethyl)-1-(tert-butyldiphenylsiloxy)ethyl-1-(tributylstannyl)allene with N-(tert-butoxycarbonyl)-2-iodoaniline directly produced the corresponding 2-vinylindole derivative, which was independently transformed into natural (-)-goniomitine and unnatural (+)-goniomitine via the cross-metathesis with chiral oxazolopiperidone lactams. The antiproliferative activity of the synthesized natural (-)-goniomitine in Mock and MDCK/MDR1 cells showed them to be more potent to retard cell growth than unnatural (+)-goniomitine.