Modified polysulfone membranes. III. Pervaporation separation of benzene–cyclohexane mixtures through carboxylated polysulfone membranes*

Membranes prepared from carboxylated polysulfone permeated benzene preferentially from benzene–cyclohexane mixtures by pervaporation. Hydrophilic polysulfones containing carboxyl groups with degrees of substitution (DS) ranging from 0.46 to 1.90 groups per repeating unit were selected for this study. The membrane having a carboxyl group DS of 0.88 showed the best trade‐off between flux and permselectivity. The permselectivity towards benzene was 234 at the weight fraction of benzene in feed of 0.1. From pervaporation and sorption experiments, it was evident that permselectivity toward benzene was due to solubility selectivity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 407–412, 1999     

Effect of nitrogen-containing compounds on polychlorinated dibenzo-p-dioxin/dibenzofuran formation through de novo synthesis

An experimental study was conducted to clarify the suppression effect of nitrogen-containing compounds, that is, ammonia and urea, on the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) through the de novo synthesis reaction. In the experiment, graphite and copper chloride contained in a mixture were used as sources of carbon and chlorine, respectively. The granulated sample mixture was charged as a packed-bed in the glass tube and heated at 300 degrees C in the flow of Ar-O2 gas mixture. In some cases, urea was added as aqueous solution to the sample, while ammonia was added to the gas flowed through the sample bed. The amount of PCDD/Fs formed decreases significantly by the addition of both ammonia and urea. Particularly, the addition of urea reduces the amount of PCDD/Fs discharged in the outlet gas by approximately 90%. The oxidation rate of carbon in the early stage of the experiment, that is, the heating period, is promoted bythe addition of nitrogen-containing compounds. However, soon afterthe temperature reaches 300 degrees C, the formation rate becomes lower than that of the case without the addition of nitrogen-containing compounds. On the other hand, organic compounds containing amino (-NH2) or cyanide (-CN) groups and those containing nitrogen within the carbon ring frame were detected in the outlet gas in the case of urea addition. Typically observed aromatic compounds are chlorobenzonitriles, chlorobenzeneamines, and chloropyridines. This suggests a possibility that hydrogen and/or chlorine combined with PCDD/Fs are also substituted by such nitrogen-containing groups, and this decreases the formation rate of their frame of carbon rings. This phenomenon was also consistent with the fact that a significant reduction was observed in the amount of PCDD/Fs released to the outlet gas when urea was added.     

Chemical forms of the fluorine and carbon in fly ashes recovered from electrostatic precipitators of pulverized coal-fired plants

The functionalities of the fluorine and carbon present in fly ashes formed in pulverized coal combustion have been studied with X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) techniques. The ash samples include 20-130 μg/g-dry and 0.4-4.1 mass%-dry of fluorine and carbon elements, respectively, and these components are enriched at the outermost layer of the ash surface. The F consists of both inorganic and organic functionalities, and the proportion of the latter is as high as 84-98 mol%. The C has different types of surface oxygen species, such as carboxyl, lactone/acid anhydride and phenolic groups, and most of these groups decompose to CO₂ or CO up to 700 °C to yield carbon active sites. When the amount of the O-functional forms increases, the content of organic C-F forms tends to increase almost linearly. On the basis of the above results, it may be speculated as one possibility that the formation of covalent C-F bonds takes place mainly through secondary reactions between gaseous F-containing compounds (HF and/or F₂) in flue gas and carbon active sites produced below 700 °C downstream of coal-fired boilers.     

Electronic erasure of stored reference signals in a metal-ZnO-SiO2-Si induced junction storage correlator

The surface-acoustic-wave storage correlator is used to store a reference signal for subsequent correlation with an unknown signal. We describe and demonstrate a method for the electronic erasure of stored signals in the context of the MZOS-induced junction storage correlator.     

Synthesis and structure-activity relationships of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' or C-7 catechol or related aromatics

A series of cephalosporins, 2-isocephems, and 2-oxaisocephems with C-3' catechol-containing (pyridinium-4-thio)methyl groups and 2-isocephems with C-7 catechol related aromatics have been prepared and evaluated for antimicrobial activity. It turns out that these compounds have highly potent activity against Gram-negative bacteria, especially resistant pathogens such as Pseudomonas aeruginosa. The most active compound of the series was (6S,7S)-7-[2-(2-aminothiazol-4-yl)-2-[(Z)-[(1,5-dihydroxy-4-pyr idon-2-yl) methoxy]imino]acetamido]-3-[[[(4-methyl-5-carboxymethyl)thiazol-2- yl] thio]methyl]-8-oxo-1-aza-4-thiabicyclo [4.2.0] oct-2-ene-2-carboxylic acid which exhibited potent in vitro activity against clinically isolated P, aeruginosa and Acinetobacter baumanii which is also resistant to many anti-infectives, and good in vivo efficacy against clinically isolated P aeruginosa.     

Study on the fundamental molecular structures of synthetic traction fluids: Part 2

It is essential to obtain guidelines for molecular design through analysing quantitatively the correlation between molecular structures and traction coefficients of traction fluids for developing an excellent traction fluid with a high traction coefficient. Although it is well known that the hydrogenation of an aromatic compound greatly increases its traction coefficient there are few accounts explaining the reason. We have analysed the influence of the intermolecular force on traction, examined why aromatic and chlorinated compounds have low traction coefficients and obtained the following results. (1) Alicyclic compounds have high traction coefficients because they interlock with each other well under high pressure. (2) Aromatic compounds have low traction coefficients because it is difficult for them to get close to each other due to repulsion of π-electrons and they have little unevenness for interlocking. (3) Chlorocyclohexane has a low traction coefficient due to the repulsion of large chlorine atoms which have a negative charge. (4) The traction property is greatly influenced by intermolecular force and molecular size, and the influence of the molecular stiffness is even smaller.     

Blood flow patterns in the rat pancreas: a simulative demonstration by injection replication and scanning electron microscopy

Scanning electron microscopy of vascular casts prepared by arterial injections of intentionally reduced amounts of resin showed that in the rat pancreas, the casting medium fills blood capillaries in the endocrine islets more promptly than those in the exocrine lobules and secretory ducts. Furthermore, the exocrine lobules containing endocrine islets allowed a more rapid resin flow through the insulo-acinar portal route than those lobules lacking an islet. The capillaries of secretory ducts were the last portions to be filled with resin. Since the resin used in this study was as viscous as blood and injected under a physiological pressure, the microcirculatory patterns demonstrated by the present method reflect the physiological flow pattern of blood in the pancreas.     

Gammadelta T cell receptor repertoire in middle ear effusions in children

In order to elucidate the immune response in otitis media with effusion, polymerase chain reaction was employed to examine gammadelta T cell receptor repertoire in the middle ear effusions of patients with otitis media with effusion. RNAs were extracted from 13 middle ear effusions of 10 children with otitis media with effusion. Vgamma2 was the most frequently used Vgamma gene. As for Vdelta gene usage, Vdelta2 amplification gave the strongest signal in 10 out of 13 samples. The results suggest that gammadelta T cells bearing Vgamma2/Vdelta2 T cell receptors accumulate in the middle ear effusions in children, and that these T cells may respond to certain bacteria or bacterial products in the middle ear.     

Detection of early esophageal and gastric cancers by mass screening

The purpose of mass screening is to decrease the mortality rate of diseases which are fatal if advanced by detecting them at an early and curable stage. From this point of view, we describe here the present state of mass screening, its problems, and the future of mass screening for esophageal and gastric cancer in Japan. The conventional X-ray examination commonly used to detect esophageal cancer does not seem to be effective in detecting the malignancy at an early stage. Therefore, endoscopic examination with Lugol staining for high-risk groups is recommended for the purpose. In contrast, mass screening for gastric cancer by X-ray examination, which has been applied until now, has reduced the mortality rate of gastric cancer. At the same time, however, as various problems are pointed out, some additional investigations have been undertaken to further reduce the mortality rate of gastric cancer. As social circumstances change, and therapy as well as diagnosis for the disease improves, it is necessary to evaluate the accuracy, problems, and limits of the present system to conduct effective and functional mass screening program. The present system must be adapted it to reflect improvements and changes.     

Generation of 880 MHz surface acoustic wave by transduction from bulk wave using corrugation grating on GaAs

Efficient transduction from bulk to surface waves by a holographic grating on a GaAs crystal has been demonstrated. The beam profiles for 880 MHz surface waves propagating on the GaAs were measured by an optical probing method.