Oligomerization of isobutene over solid acid catalysts

Oligomerization of isobutene has been carried out in the liquid phase at mild conditions using n-butane as a diluent. The reaction was studied at low temperatures (30–70 °C) and at pressures high enough to ensure that the reaction takes place in the liquid phase. A number of different resins and zeolites were evaluated as catalysts for the dimerization. The best performance was obtained with Amberlyst 15 whereas the zeolites (H-ZSM5, H-Mordenite, β and Y) all showed very rapid deactivation.     

Cytology of bronchial biopsy rinse fluid to improve the diagnostic yield for lung cancer

Sampling techniques are combined during bronchoscopy to increase the diagnostic yield for endobronchial malignant tumours. Bronchial biopsy provides the definitive histological diagnosis in most cases, but accompanying cytological procedures such as washing, brushing, needle aspiration or imprint cytology can increase diagnostic yield. In this prospective study, a different cytological technique, that could enhance the diagnostic yield of bronchoscopy without increasing its time or cost, was tested. Flexible bronchoscopy was performed in 93 patients suspected of having pulmonary neoplasms. Bronchial biopsies were initially placed in a balanced salt solution. When bronchoscopy was finished, all visible tissue fragments were removed and placed in formalin to undergo histopathological examination and the rinse fluid was sent for cytological examination. Washing was performed routinely but no cytological brushing was employed. Eighty-two patients had final diagnoses of malignant neoplasm. In four (4.8%) of these patients, the only positive result came from the cytological examination of the bronchial biopsy rinse fluid. No false-positive results were found. The agreement with the histological results was 81.8%. The addition of bronchial biopsy rinse-fluid examination increased the sensitivity of bronchoscopy from 65.8% to 70.7% (McNemar's p=0.009). The cytological study of bronchial biopsy rinse fluid offers reliable positive results in an additional 4.8% of cases, thus enhancing bronchoscopic diagnostic yield for malignant endobronchial tumours while neither prolonging the procedure nor increasing costs.     

Electromyographic characteristics of postanesthetic tremor

Plant foods contain numerous non-nutritive substances which exert biological activity. Most attention has been focused on the anticarcinogenic effects of these compounds. Many of the mechanisms involved include induction or inhibition of biotransformation enzymes. Each individual has its own isoenzyme pattern for the various drug-metabolizing enzymes. The multiplicity of these enzymes results in differential responses to dietary constituents. A substance may increase the level of a certain P450, and decrease the level of another. Although this complicates matters considerably, it also offers the possibility of specifically influencing biotransformation directed at a particular compound, e.g., a cytostatic agent. Using the important class of the glutathione S-transferase (GST) as an example, the various phenotypic and genetic origins of interindividual variation are described. Genetic variation is especially important for the mu and thetra class enzymes. The induction of individual isoenzymes of the GST has been studied in man rat. It was shown that the changes in the GST isoenzyme pattern induced by Brussels sprouts in rat liver and intestine were very similar to that caused by administration of ally isothiocyanate, and not to that resulting from goitrin. In man Brussels sprouts led to induction of GST alpha only. A number of naturally occurring catechols, or more likely the quinones derived from them, are effective irreversible inhibitors of GST. Eugenol, for instance, lowers GST activity in man. A second class of compounds which shows promise are alpha, beta-unsaturated aldehydes and ketones. A number of naturally occurring representatives of this class inhibit GST pi irreversibly, and ethacrynic acid, a drug with a similar reactive moiety in its structure, has already been shown to be quite useful to inhibit GST activity in cellular systems. Several approaches for future studies on the effects of dietary constituents are indicated: 1) further studies on the mechanisms of induction and inhibition of biotransformation enzymes: 2) careful studies using human volunteers, where the effects can be studied in isolation as much as possible; 3) studies of the disposition and kinetics of the dietary constituents themselves, to assess the relevance of inducing agents in food for the day-to-day human situation.     

The role of surfactant adsorption during ultrasonication in the dispersion of single-walled carbon nanotubes

The ionic surfactant-assisted dispersion of single-walled carbon nanotubes in aqueous solution has been studied by Raman and fluorescent spectroscopy during ultrasonic processing. During the process, an equilibrium is established between free individuals and aggregates or bundles that limits the concentration of the former that is possible. This equilibrium is a function of free sodium dodecyl sulfate concentration. At surfactant concentrations below this value, fluorescence is shifted to a lower energy due to an increase in micropolarity from water association at the nanotube surface. The mechanism of dispersion is postulated as the formation of gaps or spaces at the bundle ends in the high shear environment of the ultrasonicated solution. Surfactant adsorption and diffusion then propagate this space along the bundle length, thereby separating the individual nanotube. The former is found to be controlling, with the use of a derived kinetic model for the dispersion process and extraction of the characteristic rate of nanotube isolation.     

Performance of the ±250 kV HVDC Skagerrak submarine cables.Further development of the HVDC paper-insulated, mass-impregnated (solidtype) submarine cable

A review is given of the performance of the ±250 kV HVDC mass-impregnated, solid-type submarine cables installed between Denmark and Norway. The cables, which have been partly overloaded, have successfully met all requirements. Three mechanical failures have occurred, two due to heavy beam trawls and the third during stormy weather. On two occasions the cables were repaired in stormy weather. They have been hit by a great number of trawlboards and fisherboats' anchors without any significant damage. Tests and investigations of the insulation have demonstrated that this type of cable can be used for far higher voltages than assumed before. Migration of the impregnant is of less significance than previously believed. The cable can tolerate very high mechanical strains, such as those arising during layering at very great sea depths. Bending tests were made on cable pieces at tensions up to 72 metric tons; the results of the subsequent electrical tests were excellent, and no visible traces of damage of the insulation were found. The design stresses are considered, and suggestions are made for the design of cable for very deep waters     

A model for nucleation and growth of single wall carbon nanotubes via the HiPcO process: a catalyst concentration study

Using the High Pressure carbon monoxide (HiPco) reactor we conducted an experiment on the effects of changing the catalyst concentration. With each catalyst concentration tested the resulting raw HiPco material was characterized for average SWNT lengths, SWNT diameters, residual iron particle size, and large fullerene content. We were able to determine trends in each of these characteristics as the catalyst concentration was changed. As the catalyst concentration was decreased SWNT lengths increased, SWNT diameters increased, the residual iron particle size increased, and the large fullerene content decreased. From these trends we have developed a Competitive Growth model for nucleation and growth of SWNTs via the HiPco process.     

MECHANICAL PROPERTIES AND б-PHASE EMBRITTLEMENT IN A FERRITE-AUSTENITE STAINLESS STEEL AT ELEVATED TEMPERATURES

研究了铁素体(F)-奥氏体(A)双相不锈钢在600—1100℃范围内的力学性能,其韧性-温度曲线在800-900℃之间有一极小值。阐述了σ相析出动力学及其对材料力学性能的影响,σ相严重损害合金塑性,其影响程度随σ相含量的增加而增高,并与试验温度有极大的关系,1000℃时σ相对拉伸性能影响消失。     

Cross-linking of 17 beta-estradiol to monoclonal antibodies by direct UV irradiation: application to an enzyme immunometric assay

Ultraviolet irradiation was used to cross-link 17 beta-estradiol directly to monoclonal anti-17 beta-estradiol antibodies coated on 96-well microtiter plates. Cross-linking efficiency was directly correlated with both irradiation energy and wave-length. The best results were obtained at 254 (10 J/cm2, 45-min irradiation) and 312 nm (40 J/cm2, 160-min irradiation). The irradiation fully denatured both individual molecules (i.e., 17 beta-estradiol and monoclonal anti-17 beta-estradiol antibody), but 17 beta-estradiol was at least partly protected when immunologically bound to the paratope of the antibody. Four different monoclonal anti-17 beta-estradiol antibodies yielded positive results, demonstrating that this photo-cross-linking has considerable potential. We used this original approach to develop a new enzyme immunometric assay of 17 beta-estradiol based on our previously described immunometric procedure, solid-phase immobilized epitope immunoassay, which uses chemical agents to cross-link haptens via amino groups to specific antibodies. The assay was specific (no cross-reactivity with other natural steroids), precise, and sensitive (detection limit of 38 pg/mL in human serum). It correlated well with two competitive commercial immunoassays when tested on 40 human sera.