Study on crystalline properties of Er-Si-O compounds in relation to Er-related 1.54 μm photoluminescence and electrical properties

Er-Si-O crystalline compounds, which exhibit superlattice structures and sharp and strong Er-related 1.54 μm photoluminescence (PL) spectra at room temperature have been formed by self-assembling growth mechanism. Oxidation of the starting materials which have Si and Er at an atomic ratio of 2:1 are prepared and then oxidation and succeeding high-temperature annealing in Ar above 1250 °C cause a self-assembled superlattice-structured Er-Si-O crystalline compounds. The control of the ratio of Si and Er, as well as the following oxidation and annealing processes, is found to be sensitive to the crystalline properties, PL spectra and electrical properties. In this study, Er-Si-O crystalline thin films are formed on Si substrates by sol-gel and MOMBE methods, and their crystalline properties such as crystalline orientation and concentration ratio of Er, Si and O are investigated. Crystalline Er-Si-O films of high orientation are successfully grown on Si(1 0 0) and its inclined surface. The PL and excitation spectra, fluorescence decay and the electrical properties are found to be strongly related to the crystalline properties. Excess O causes a broader 1.54 μm PL spectra, slower fluorescence decay, lower carrier-mediated excitation and higher resistivity. A precise control of O is found to be necessary to grow superlattice-structured Er-Si-O compounds, which are semiconducting and are excitable via carrier-mediated excitation mechanism.     

Influence of the characteristics of soil and fly ash on the supercritical carbon dioxide extraction of dioxins.

Several investigations on the extraction of dioxins from soil and fly ash with supercritical fluid have been reported; however, few of them describe the influence of components on the extraction. We extracted dioxins from eight samples with different values of organic carbon content and surface area with supercritical CO(2) at a temperature of 463 K, a pressure of 40 MPa, and using 10% toluene as an entrainer. We researched the influence of the characteristics of soil and fly ash on supercritical CO(2) extraction of dioxins. The results revealed that the extraction efficiencies of PCDD/DFs and PCBs were high for all soil samples, while that of fly ash samples decreased with the increase in organic carbon content and surface area. The extraction efficiencies of dioxins from four standard samples, activated carbon, humic acid, alumina, and florisil, were also examined. The results revealed that the extraction efficiencies were strongly influenced by activated carbon like components present in the samples.     

Donaldson–Friedman construction and deformations of a triple of compact complex spaces,II

In a previous paper of the same title the author gave a generalization of the constrution of Donaldson–Friedman, to prove the existence of twistor spaces of n CP ² with a special kind of divisors. In the present paper, we consider its equivariant version. When n = 3, this gives another proof of the existence of degenerate double solid with C *–action, and we show that the branch quartic surface is birational to an elliptic ruled surface. In case n ≥ 4, this yields new Moishezon twistor spaces with C *–action, which is shown to be the most degenerate ones among twistor spaces studied by Campana and Kreußler.     

Improvement of gas meter performance using polymer materials

The measuring elements of both dry‐ and wet‐type gas meters are composed of a diaphragm and rotary drum. In this article an explanation on the principle of measuring and the structure of the gas meter for each of these two types was discussed. Such applications were made as follows: synthetic rubber was used for the measuring diaphragm, engineering plastic was employed instead of metal for the measuring drum, and poly(butylene terephthalate) (PBT) was used for the casing, respectively. As a result, an improvement in the gas resistance performance and productivity, which led to a lighter weight, more compactness and a lower cost of productions was achieved. Also the influence of the solubility of the measured gas to the plastic on the measured valve was discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Kinetic study of the crosslinking reaction of 1,2‐polybutadiene with dicumyl peroxide in the absence and presence of vinyl acetate

The crosslinking reaction of 1,2-polybutadiene (1,2-PB) with dicumyl peroxide (DCPO) in dioxane was kinetically studied by means of Fourier transform near-infrared spectroscopy (FTNIR). The crosslinking reaction was followed in situ by the monitoring of the disappearance of the pendant vinyl group of 1,2-PB with FTNIR. The initial disappearance rate (R₀) of the vinyl group was expressed by R₀ = k[DCPO]^0.8[vinyl group]^−0.2 (120 °C). The overall activation energy of the reaction was estimated to be 38.3 kcal/mol. The unusual rate equation was explained in terms of the polymerization of the pendant vinyl group as an allyl monomer involving degradative chain transfer to the monomer. The reaction mixture involved electron spin resonance (ESR)-observable polymer radicals, of which the concentration rapidly increased with time owing to a progress of crosslinking after an induction period of 200 min. The crosslinking reaction of 1,2-PB with DCPO was also examined in the presence of vinyl acetate (VAc), which was regarded as a copolymerization of the vinyl group with VAc. The vinyl group of 1,2-PB was found to show a reactivity much higher than 1-octene and 3-methyl-1-hexene as model compounds in the copolymerization with VAc. This unexpectedly high reactivity of the vinyl group suggested that an intramolecular polymerization process proceeds between the pendant vinyl groups located on the same polymer chain, possibly leading to the formation of block-like polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4437–4447, 2004     

Design and synthesis of labeling reagents (MS probes) for highly sensitive electrospray ionization mass spectrometry and their application to the detection of carbonyl, alcohol, carboxylic acid and primary amine samples.

Novel labeling reagents, called MS probes, which possess a positively charged quaternary amine moiety and can transform a neutral analyte into a charged compound by simply mixing with the analyte and allowing the mixture to stand from several minutes to 30 min at room temperature or while heating to 50 degrees C, were designed and synthesized for the highly sensitive detection of carbonyl, alcohol, carboxylic acid and primary amine samples by electrospray ionization mass spectrometry (ESI-MS). The positively charged products can be detected with high sensitivity in an ESI-MS system, which is the most popular liquid MS instrument. All of the labeled products showed a remarkably large increase in the molecular-ion peak abundance detection sensitivity of over 500-fold at picomolar concentration levels compared to that of unlabeled analytes in an ESI-MS system. These MS probes, used together with liquid MS detection, are widely applicable as a convenient method for the highly sensitive detection of less than picomolar levels of analytes, and therefore greatly enhance the power of ESI-MS analysis.     

Synthesis and structure-activity relationships of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines as a new class of gastric H+/K(+)-ATPase inhibitors.

A series of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines (3) was synthesized and evaluated for its biological activity against gastric H+/K(+)-ATPase prepared from rabbit stomach and gastric acid secretions in Heidenhain pouch dogs. Monoalkyl substituents on the nitrogen atom of the aniline moiety markedly inhibited the enzyme activity to the same degree as omeprazole, a representative H+/K(+)-ATPase inhibitor. Most of these compounds, administered at 3 mg/kg i.v. inhibited histamine-stimulated gastric acid secretion. The inhibitory activity of these derivatives on the enzymes at pH 6.0 was more potent than that at pH 7.4, and was distinctly correlated to stability in aqueous solution at pH 5.0.     

NDMAP: the best material to study the Haldane's prediction

As predicted by Haldane, spin, S=1 one-dimensional (1D) Heisenberg antiferromagnet (HAF) has an energy gap between the singlet ground state and first excited triplet. On application of magnetic field, the triplet state Zeeman splits and the energy of one of the triplet state becomes zero at a critical field, H_c. Above H_c the system recovers magnetism. Then, we expect that a quasi-1D HAF will show a magnetic long-range ordering (LRO) at low temperatures due to the inter-chain coupling. This field-induced LRO has not been observed before due to complication of the crystal structure in the materials studied so far and/or technical difficulty.From a heat capacity measurement on a single crystal of an S=1 quasi-Q1D HAF, Ni(C₅H₁₄N₂)₂N₃(PF₆), we found an anomaly at a temperature in finite fields indicating a field-induced phase transition. A magnetic LRO is confirmed by a neutron diffraction measurement on the same sample. The temperature versus magnetic field phase diagram of this compound is constructed and discussed.     

Measurement of intense microwave field patterns using a neon glow indicator lamp

A novel method using small neon glow lamps with electrodes is developed for measuring intense microwave field patterns. When the lamp axis coincide with the electric field direction, the lamp discharge starts at the feeblest microwave electric field strength. Therefore, the lamp axis shows the field direction and the discharge starting indicates the field strength. The field strength for starting the microwave discharge is less than the strength for AC discharge, because of its low loss discharge mechanism. In the experiments using a microwave oven, it has been demonstrated again comparing with the simulated results that the method is able to use for measuring the intense electric field strength and direction.     

Radical copolymerization of 2‐trifluoromethylacrylic monomers. II. Kinetics,monomer reactivities,and penultimate effect in their copolymerization with norbornenes and vinyl ethers

Radical copolymerizations of electron‐deficient 2‐trifluoromethylacrylic (TFMA) monomers, such as 2‐trifluoromethylacrylic acid and t‐butyl 2‐trifluoromethylacrylate (TBTFMA), with electron‐rich norbornene derivatives and vinyl ethers with 2,2′‐azobisisobutyronitrile as the initiator were investigated in detail through the analysis of the kinetics in situ with ¹H NMR and through the determination of the monomer reactivity ratios. The norbornene derivatives used in this study included bicyclo[2.2.1]hept‐2‐ene (norbornene) and 5‐(2‐trifluoromethyl‐1,1,1‐trifluoro‐2‐hydroxylpropyl)‐2‐norbornene. The vinyl ether monomers were ethyl vinyl ether, t‐butyl vinyl ether, and 3,4‐dihydro‐2‐H‐pyran. Vinylene carbonate was found to copolymerize with TBTFMA. Although none of the monomers underwent radical homopolymerization under normal conditions, they copolymerized readily, producing a copolymer containing 60–70 mol % TFMA. The copolymerization of the TFMA monomer with norbornenes and vinyl ethers deviated from the terminal model and could be described by the penultimate model. The copolymers of TFMA reported in this article were evaluated as chemical amplification resist polymers for the emerging field of 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1478–1505, 2004