Recent progress in the improvement of hydrothermal stability of zeolites

Zeolites have been successfully employed in many catalytic reactions of industrial relevance. The severe conditions required in some processes, where high temperatures are frequently combined with the presence of steam, highlight the need of considering the evolution of the catalyst structure during the reaction. This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.

This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.     

On-line purification for the determination of catecholamines by liquid chromatography

An on-line purification method for catecholamines was studied using a flow system equipped with an alumina microcolumn. The procedure involves catecholamine adsorption, column washing and catecholamine elution steps. The system is designed not to decompose catecholamines under alkaline conditions in the adsorption step. Flow-rates and times for different solutions delivered in each step (alkaline buffer for adsorption, water for washing and an acidic solution for elution), column length and sample volume to be loaded were systematically investigated by liquid chromatography. Under optimum conditions, norepinephrine, epinephrine, dopamine and 3,4- dihydroxybenzylamine (internal standard) can be purified with recoveries of ? 90% within 11 min with manual operation. This method was efficiently applied to urine samples and the results indicate the possibility that catecholamines in biological samples are automatically purified.     

Determination of 4-alkylphenols by novel derivatization and gas chromatography-mass spectrometry

A simple and sensitive method for the determination of alkylphenols in water samples has been developed using gas chromatography-mass spectrometry. Alkylphenols were determined after the extractive derivatization with pentafluoropyridine. The derivatization of alkylphenols efficiently proceeded to give the corresponding 4-tetrafluoropyridyl derivatives under the biphasic reaction system. The derivatization conditions including the phase-transfer catalyst, the amount of pentafluoropyridine, the reaction time, the concentration of NaOH and organic solvent were optimized. On the mass spectra of these derivatives, intense specific ion peaks were observed: m/z 256 for 4-n-alkylphenols and m/z 284 for 4-tert.-alkylphenols. Calibration curves were linear in the range of 20-1000 ng/l (200-10,000 ng/l for nonylphenol), and the detection limits varied between 6.93 and 15.7 ng/l (85.2 ng/l for nonylphenol). The average recoveries of the alkylphenols in a fortified river water sample (100 ng/l except for nonylphenol: 1000 ng/l) ranged from 91.1 to 112%. The relative standard deviations were found to be between 5.6 and 16%. This method was successfully applied to the determination of alkylphenols in river water.     

Synthesis of 1-arylacenaphtho[1,2-d]pyrazoles and 5,7-Dehydro-5H,7H-benzo[b]acenaphtho[1,2-e]-1,3a,6a-triazapentalenes

2-Benzoyl- 5 and 2-acetylacenaphthenone 6 , prepared from the corresponding 1-acyl-2-(1-pyrrolidinyl)-acenaphthylenes 2 and 3 , reacted with arylhydrazines 8 under acidic conditions to give the corresponding 1-arylacenaphtho[1,2-d]pyrazoles 9 and 10 . Novel heteropentalene mesomeric betaines, 5,7-dehydro-5H,7H-benzo[b]acenaphtho[1,2-e]-1,3a,6a-triazapentalenes 13 and 14 were prepared by reductive cyclization of 1-(o-nitrophenyl)acenaphtho[1,2-d]pyrazoles 9d and 10d , respectively.     

A unification of the existence theorems of the nonlinear complementarity problem

The nonlinear complementarity problem is the problem of finding a point x in the n-dimensional Euclidean space,R ⁿ , such that x ? 0, f(x) ? 0 and 〈x,f(x)～ = 0, where f is a nonlinear continuous function fromR ⁿ into itself. Many existence theorems for the problem have been established in various ways. The aim of the present paper is to treat them in a unified manner. Eaves's basic theorem of complementarity is generalized, and the generalized theorem is used as a unified framework for several typical existence theorems.     

A novel method for determination of inorganic oxyanions by electrospray ionization mass spectrometry using dehydration reactions

Novel methods for the determination of inorganic oxyanions by electrospray (ES) ionization mass spectrometry have been developed using dehydration reactions between oxyanions and carboxylic acids at the ES interface. Twelve oxyanions (VO₃^?, CrO₄^2?, MoO₄^2?, WO₄^2?, BO₃^3?, SiO₃^2?, SiO₄^4?, AsO₄^4?, AsO₂^?, SeO₄^2?, SeO₃^2? and NO₂^?), out of 16 tested, reacted with at least one of four aminopolycarboxylic acids, i.e. iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), trans‐1,2‐diaminocyclohexane‐N,N,N′,N′‐tetraacetic acid and triethylenetetramine‐N,N,N′,N″,N′″,N′″‐hexaacetic acid, at the ES interface to produce the dehydration products that gave intense mass ion responses, sufficient for trace analysis. As examples, trace determinations of Cr^VI and silica in water samples were achieved after online ion exchange chromatography, where the dehydration product of CrO₄^2? and NTA (m/z 290) and that of SiO₄^4? and IDA (m/z 192) were measured. The limits of detection of the respective methods were 17 nM (0.83 ng Cr/ml) for Cr^VI and 0.17 μM (4.8 ng Si/mL) for SiO₄^4?. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and properties of polyhydroxyurethane bearing silicone backbone

Polyhydroxyurethane bearing silicone backbone was prepared by polyaddition of silicone diamines with a bifunctional five‐membered cyclic carbonate prepared from the corresponding diepoxide and CO₂. Polymerization in propylene glycol methyl ether acetate proceeded smoothly, and polymers could be obtained in high yields under appropriate conditions. The introduced silicone moieties improved the hydrophobicity and lowered the glass transition temperature keeping thermal stability. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1113–1118     

Visible light-responsive cell scaffolds with bilayer structures for single cell separation

Collagen is a major component of the extracellular matrix, and collagen gels have been used as cell scaffolds. We previously prepared gold nanoparticle (AuNP)-embedded collagen gels (AuCol) to serve as cell scaffolds that were sensitive to visible light. We performed single cell detachment from this cell scaffold using a microscope equipped with a laser irradiation system. In the present study, we adjusted hydrogel thickness and AuNP concentration in AuCol, with a goal of improving cell detachment efficiency. Thin hydrogels became blackened after the laser irradiation, and thick hydrogels with high AuNP concentrations were not permeable to the laser light. We, therefore, prepared bilayer gels, composed of AuCol as the upper layer and intact collagen gel (Col) as the bottom layer. These bilayer gels allowed more effective cell detachment, because they were thick and optically transparent. Our results indicated that an AuCol/Col ratio of 2 enabled the highest cell detachment efficiency. Essentially, no cell damage was observed in our system, suggesting that this is a cell-friendly single cell separation system.     

Effect of C7-Substituent on Self-Assembly of Chlorosomal Chlorophylls

Abstract

Bacteriochlorophyll d analogues that possessed a series of bulky substituents of OMe, OCOMe, and OCO ^t Bu at the C7¹-position were synthesized (Zn-complexes of methyl 7¹-substituted-3-(1-hydroxy-methyl)pyropheophorbide a). Aggregation behavior of these pigments was examined in comparison with a natural-type compound (C7¹-H) to elucidate the effects of size of the C7¹-moiety on self-assembly of the chlorins. These C7¹-substituted Zn-chlorins formed self-aggregates in 1% THF/hexane. The aggregates gave almost the same visible absorption bands, especially a ca. 2000-cm^?1 red-shifted Q_y peak; the spectra were essentially similar to those of the natural-type Zn-chlorin (C7¹-H). All the aggregates of the C7¹-substituted compounds showed similar exciton-type CD couplets in the red-shifted Q_y region, which were different from the feature of the couplet of the C7¹-H Zn-chlorin aggregate. These spectral data suggested that the C7¹-moiety did not interrupt the intermolecular linkages between chlorin molecules but altered the supramolecular structure which influences the long-range chirality.