Improvement of the electrical properties of TiO2-doped Bi5Nb3O15 thin films by the addition of MnO2

The leakage current density of a 1.0 mol% TiO₂-doped Bi₅Nb₃O₁₅ (TB₅N₃) film was high, and the breakdown electric field was low. This could be attributed to the presence of intrinsic oxygen vacancies and free electrons. The electrical properties of the TB₅N₃ film improved upon the addition of MnO₂ because of the formation of extrinsic oxygen vacancies, which caused the number of intrinsic oxygen vacancies to decrease in order to maintain the equilibrium concentration of oxygen vacancies in the film. However, the electric properties degraded when the MnO₂ content exceeded 15.0 mol% because of the formation of interstitial oxygen ions and holes. The dielectric constant (?_r) of the TB₅N₃ film slightly decreased upon the addition of a small amount of MnO₂. The TB₅N₃ film with 15.0 mol% MnO₂, which exhibited a small leakage current density of 2.5 × 10^?11 A/cm² at 0.15 MV/cm and a high breakdown electric field of 0.47 MV/cm, still maintained a large ?_r of 118 with a small loss tangent of 2.0% at 100.0 kHz.     

A discontinuous solution for an evolution compressible stokes system in a bounded domain

An evolution compressible Stokes system is studied in a bounded cylindrical region . The initial datum of pressure is assumed to have a jump at a specified curve C₀ in Ω. As predicted by the Rankine-Hugoniot conditions, the pressure and velocity derivatives have jump discontinuities along the characteristic plane of the curve C₀ directed by an ambient velocity vector. An explicit formula for the jump discontinuity is presented. The jump decays exponentially in time, more rapidly for smaller viscosities. Under suitable conditions of the data, a regularity of the solution is established in a compact subregion of Q away from the jump plane.     

Synthesis and thermal behavior of poly(ethylene oxide) poly(N‐substituted urethane)

Poly(N‐substituted urethane)s with an alkyl or ligo(ethylene oxide) monomethyl ether side chain were synthesized by the reaction operating in the following two‐step process: first, by metalation of the starting polymer with potassium tertiary butoxide (t‐BuOK) and then by treatment of the obtained urethane polyanion with tosylate in dimethyl sulfoxide. The thermal properties of poly(ethylene oxide) poly(N‐substituted urethane) (N‐sub PEOPU) were investigated in view of the N‐substitution degree and properties of the substituent. The chemical structures were characterized by Fourier transform infrared, ¹H NMR, and ¹³C NMR spectroscopies. DSC and thermogravimetric analysis (TGA) were used to investigate the thermal properties of N‐sub PEOPUs. As the degree of N‐methylation increased, the glass‐transition temperature (T_g) of the N‐sub PEOPUs linearly decreased from 6 to ?29 °C, and the weight‐loss temperature of 5% (T) from TGA in air increased from 278 to 360 °C. In the fully N‐substituted PEOPUs, the behavior of the thermal decomposition of the PEOPU that was processed in two stages was changed to one‐step decomposition in the temperature range of 360–440 °C. The T_g was shifted to a lower temperature with an increasing length of the substituent in N‐sub PEOPU. Improvement of the thermal stability by N‐substitution was more significant in N‐alkyl PEOPU than in N‐ethoxylate PEOPU. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4129–4138, 2001     

Influence of Extracellular Polymeric Substances on Membrane Fouling and Cleaning in a Submerged Membrane Bioreactor

There is little information available on the correlation between the concentration of extracellular polymeric substances (EPS) and membrane fouling as well as cleaning efficiency. In this study, two lab-scale flat submerged membrane bioreactors (SMBRs) at sludge retention times (SRTs) of 25 and 250 days were operated at a constant permeate flux (12.5 l m⁻² h⁻¹). Samples of activated sludge were tested to quantify the concentration of extractable EPS using cation exchange resin. Batch filtration tests were also performed to determine the specific cake resistances and the flux recoveries. The extractable EPS and protein concentrations were relatively low at the prolonged SRT, leading to cake layers easily removable by the physical manual cleaning or the de-ionized water backwashing and the chemical cleaning with sodium hypochlorite methods. The extent of flux recoveries (both in SMBRs and batch filtration tests) and macroscopic as well as microscopic images indicated that the chemical cleaning could enhance the effectiveness of cleaning. The membrane fouling and cleaning mechanisms were also discussed.__________From Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 392–397.Original English Text Copyright © 2005 by Chackrit Nuengjamnong, Ji Hyang Kweon, Jinwoo Cho, Kyu-Hong Ahn, Chongrak Polprasert.This article was submitted by the authors in English.     

Grape extracts suppress the formation of preneoplastic foci and activity of fatty acid synthase in rat liver

This study was conducted to examine the effects of dietary grape extracts on preneoplastic foci formation in rat hepatocarcinogenesis, and related hepatic enzymes. Male Sprague-Dawley rats were fed basal diet or grape diet containing 15% concentrated grape extracts (68 bricks). The grape diet groups were divided into whole-period grape diet group (DEN-GW; grape diet group fed throughout experimental period) and postinitiation grape diet group (DEN-GP; grape diet group fed from post initiation stage) according to the starting time point of the grape diet. Hepatocarcinogenesis was induced by diethylnitrosamine (DEN; 200 mg/kg bw) and 2/3 partial hepatectomy (DEN-B; DEN-treated basal diet group, DEN-GW, and DEN-GP groups), while the control group treated with saline and sham operation (Control group). The formation of placental glutathione (GSH) S-transferase positive (GST-P+) foci in DEN-GW group was moderately but significantly suppressed, however, not in DEN- GP group. Thiobarbituric acid reactive substances content of DEN-GW group was significantly lower than that of DEN-B group. The activity of fatty acid synthase (FAS) in the grape diet groups was decreased about 1/2 of the DEN-B group. The content of GSH and GSH peroxidase activity were increased by carcinogen treatment, but not modulated by grape diet. The activities of GSH S-transferase, p-nitrophenol hydroxylase, and catalase were not affected by diet or treatment. Conclusively, the grape diet-induced reduction of FAS activity that was expressed highly in neoplastic tissues, might be one of the contributing mechanisms of hepatic cancer prevention.     

Retro-ene reaction. II. Reaction of 4,5-dichloro-1-hydroxy-methylpyridazin-6-one with alkyl halides and carboxylic acid chlorides

1-Alkyl-4,5-dichloropyridazin-6-oncs and (4,5-dichloro-6-oxopyridazin-1-yl)methylcarboxylates were synthesized from 4,5-dichloro-1-hydroxymethylpyridazin-6-one and the corresponding alkyl halides or carboxylic acid chlorides. Also the reaction mechanisms via a fragmentation of retro-ene type are discussed.     

Geometric Isomerisation of Bifunctional Alkenyl Fluoride Linchpins: Stereodivergence in Amide and Polyene Bioisostere Synthesis

Amide groups are pervasive across the chemical space continuum, where their structural and pharmacological importance, juxtaposed with the hydrolytic vulnerabilities, continues to fuel bioisostere development. Alkenyl fluorides have a venerable history as effective mimics (Ψ[CF=CH]) owing to the planarity of the motif and intrinsic polarity of the C(sp²)−F bond. However, emulating the s-cis to the s-trans isomerisation of a peptide bond with fluoro-alkene surrogates remains challenging, and current synthetic solutions only enable access to a single configuration. Through the design of an ambiphilic linchpin based on a fluorinated β-borylacrylate, it has been possible to leverage energy transfer catalysis to affect this unprecedented isomerisation process: this provides geometrically-programmable building blocks that can be functionalised at either terminus. Irradiation at λ_max=402 nm with inexpensive thioxanthone as a photocatalyst enables rapid, effective isomerisation of tri- and tetra-substituted species (up to E/Z 98 : 2 in 1 h), providing a stereodivergent platform for small molecule amide and polyene isostere discovery. Application of the methodology in target synthesis and initial laser spectroscopic studies are disclosed together with crystallographic analyses of representative products.     

Autoignition of varied cetane number fuels at low temperatures

The reactivity of six kerosene based control fuels, specifically formulated for cetane number variation, are investigated by measuring ignition delay time in a heated rapid compression machine. Cetane numbers vary from 30 to 55 (increment of 5) while holding other properties relatively constant by adjusting chemical group composition. Main cetane variation was controlled through the distribution of normal alkanes and isoalkanes, which was fine-tuned using additives. Other fuel properties such as density, viscosity, H/C ratio, etc. were balanced using cyclic compounds and aromatics. Fuels were tested in the RCM at compressed pressures of P_c=?10 and 20?bar, equivalence ratios of ??=?0.25, 0.5 and 1.0, in the low to intermediate temperature range (620?K?≤?T_c?≤?730?K). Relations between cetane number and ignition delay time have been evaluated at multiple test conditions, and further analysis on multistage ignition has been conducted. Ignition delay times of fuels with higher cetane numbers are shorter at these temperatures for most conditions. First stage ignition delay time measurements have been observed to be relatively insensitive to P_c, ?, and fuel type, while deviations in overall ignition delay times are mainly attributed to second stage ignition delay time, impacted by variations in the first stage temperature. Control fuels of this type offer an opportunity to be used in practical experiments to determine the impact of cetane number on combustion dynamics.     

Synthesis of 1‐[(pyrazol‐3‐yl)methyl]pyridazin‐6‐ones

This paper presents the synthesis of 1‐[(pyrazol‐3‐yl)methyl]pyridazin‐6‐ones from ethyl 4‐(4,5‐dichloro‐6‐oxopyridazin‐1‐yl)‐3‐oxobutanoate.