Reactions of 3-acetyltropolone and its methyl ethers with hydroxylamine. Formation of 8H-cyclohept[d]isoxazol-8-one and 8H-cyclohept[c]isoxazol-8-one

The reaction of 3-acetyltropolone ( 1 ) with hydroxylamine under the acidic condition gave 3-methyl-8H-cyclohept[d]isoxazol-8-one ( 4 ) and its oxime ( 5 ), and under the neutral condition gave 4 and 3-acetyltropolone oxime ( 6 ). The reaction of 3-acetyl-2-methoxytropone ( 2a ) with hydroxylamine under the acidic condition gave 4, 5 , and 4-methyl-1H-2,3-benzoxazin-1-one ( 7 ), and under the neutral condition gave 4, 7 , 3-methyl-8H-cyclohept[c]isoxazol-8-one ( 8 ), and its oxime ( 9 ). The reaction of 7-acetyl-2-methoxytropone ( 2b ) with hydroxylamine under the acidic condition gave 4 and 5 , and under the neutral condition gave 5, 7 , and 9 .     

Analysis of size-segregated aerosol-bound polycyclic aromatic hydrocarbons with high time resolution using two-step laser mass spectrometry

Polycyclic aromatic hydrocarbons are known for their mutagenic and carcinogenic properties. They are mainly emitted into the atmosphere by anthropogenic, incomplete combustion sources. Their trends over the course of a day are of interest in air quality management. A new combination of methods has been developed for the qualitative monitoring of polycyclic aromatic hydrocarbons in ambient aerosols with high time and size resolution. This has been accomplished by combining sampling with a rotating drum impactor and the analysis two-step laser mass spectrometry (L2MS). A validation for this method was carried out. Essential features of these combined techniques are (i) continuous, automatic sampling and (ii) selective as well as sensitive analysis due to the low detection limits which can be achieved with the L2MS analysis instrument. Analysis of a field sample taken in downtown Zurich, Switzerland, underlines the usefulness of this combined method, for example for following diurnal cycles of polycyclic aromatic hydrocarbons.     

Infrared electronic absorption in a single-component molecular metal

The infrared spectra of the crystal of transition metal complex molecules with extended-TTF ligands, Ni(tmdt)2, which is the first single-component molecular metal that has a stable metallic state even at low temperatures, exhibited an extremely low-energy electronic absorption around 2200 cm-1 (tmdt = trimethylenetetrathiafulvalenedithiolate). The systematic shift of the absorption peaks for molecules similar to Ni(tmdt)2, which range from metallic to semiconducting crystals, shows that the single-component molecular conductors are composed of molecules with unprecedentedly small HOMO-LUMO gaps.     

Second harmonic generation due to quadrupole interaction in a photonic crystal slab: angle dependence and symmetry of the unit cell

We investigate second harmonic generation (SHG) from a photonic crystal slab consisting of centrosymmetric materials. The SHG signal is observed in the transmission direction when the incident laser excites the quasiwaveguide mode. As the SHG frequency approaches the exciton level, the SHG intensity increases resonantly. When the incident angle is exactly 0, the SHG signal vanishes even if the transmission dip is excited. This fact is readily explained by a quadrupole theory based on the Lorentz oscillator model, where the source of the nonlinearity is the Lorentz force. When the unit cell in the photonic crystal lacks inversion symmetry, the SHG signal is expected even for the normal incidence. It is experimentally demonstrated for a square array of triangular semiconductor slabs.     

Determination of selenium in sediments by fluorimetry with 2,3-diaminonaphthalene after an improved pretreatment by tellurium coprecipitation

Summary An improved fluorimetric method for the determination of selenium in estuary sediments and sedimentary core samples is described. For the separation of selenium, coprecipitation with tellurium-ascorbic acid method gave satisfactory results. The status of the pollution caused by selenium in Nagoya area, which is one of the most industrially active areas in Japan, was estimated, based on the results obtained with this method. Several g/g of selenium were determined in the sediments. Interferences by foreign ions were eliminated by the coprecipitation procedure. Selenium added was recovered by 95–101%.

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Selenbestimmung in Sedimenten mit Hilfe der Fluorimetrie mit 2,3-Diaminonaphthalin nach einer verbesserten Vorbehandlung durch Tellur-Mitfällung

Zusammenfassung Gehalte bis zu mehreren g/g Selen wurden nach dem verbesserten Verfahren in den Sedimenten des Hafens von Nagoya bestimmt. Störungen durch Fremdionen wurden durch das Mitfällungsverfahren mit Tellur/Ascorbinsäure verhindert. Zugesetztes Selen wurde zu 95 bis 101% wiedergefunden.

     

Synthesis of 4-ylidenebutenolides from 2-trimethylsiloxyfuran

Dehydration or dealkoxylation of the reaction products of various aldehydes, ketones, and acetals with 2-trimethylsiloxyfuran gave corresponding 4-ylidenebutenolides in good to high overall yields.     

Separation and determination of selenium(IV) in environmental water samples by an anion-exchange resin modified with bismuthiol-II and diaminonaphthalene fluorophotometry

Summary Selenium(IV) in environmental water samples was determined fluorometrically following its collection by the use of a new functional resin. The resin was easily prepared from an anion-exchange resin by modification with bismuthiol II. A highly selective adsorption of selenium(IV) was achieved by the formation of stable selenotrisulfide from bismuthiol II and selenium(IV) on the resin. The method was successfully employed for the determination of Se in river water and waste water.

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Trennung und Bestimmung von Selen(IV) in Umwelt-Wasserproben mit Hilfe eines Bismuthiol II-modifizierten Anionenaustauschers und der Fluorophotometrie mit Diaminonaphthalin

Zusammenfassung Das Selen wurde mit Hilfe eines mit Bismuthiol II modifizierten Anionenaustauschers angereichert und fluorometrisch bestimmt. Die Adsorption, die auf der Bildung eines stabilen Selentrisulfids beruht, ist sehr selektiv. Das Verfahren wurde mit gutem Erfolg zur Selenbestimmung in Fluß- und Abwasser eingesetzt.

     

Fractional knapsack problems

The fractional knapsack problem to obtain an integer solution that maximizes a linear fractional objective function under the constraint of one linear inequality is considered. A modification of the Dinkelbach's algorithm [3] is proposed to exploit the fact that good feasible solutions are easily obtained for both the fractional knapsack problem and the ordinary knapsack problem. An upper bound of the number of iterations is derived. In particular it is clarified how optimal solutions depend on the right hand side of the constraint; a fractional knapsack problem reduces to an ordinary knapsack problem if the right hand side exceeds a certain bound.     

On the nature of thermal anomalies in aqueous systems

New experimental data put in evidence a time dependence of the “thermal anomalies” in aqueous heterogeneous systems and suggest a reexamination of their nature.