PARTITION BETWEEN α-METHYL AND α-METHYLENE PROTONS IN 1H NMR SPECTRA OF COAL TARS

Cut-off points between protons in a-methyl and or-methylene groups were proposed for the evaluation of 'H NMR spectra of coal tars. The position of the cut-off points depended on the proton aromaticity and related structural features of the samples. Equations for the calculation of the cut-off points as a function of proton and carbon aromaticity, and atomic H/C ratio were proposed for the range of proton aromaticity between 0.2 and 0.6.     

ALIPHATIC C-H BOND RESPONSES IN THE 900-700 cm-1 REGION OF THE FTIR SPECTRA OF COAL TARS

Four bituminous coals were comprehensively separated by column chromatography into a number of fractions. Four aromatic hydrocarbon fractions of each tar were analyzed by FTIR spectroscopy, and the 900-700 cm^-1 spectral region was evaluated. This spectral region was found to be composed of at least 14 separate bands, which were resolved by using self-deconvolution and curve-fitting procedures. The bands near 821 cm^-1, 791 cm^-1, and 784 cm^-1 were proposed to originate from rocking vibrations of aliphatic C-H bonds. For the tar samples with a proton aromaticity between 0.21 and 0.37, these bands account for on average 12% of the total integral intensity of the 900-700 cm^-1 region. This percentage cannot likely be neglected in a correct quantitative evaluation of the region and calculation of the aromatic hydrogen concentration. However, a correct resolution of the bands can be very difficult in the FTIR spectra of a complex material, such as coal.     

Fractionation of a statistical copolymer in a demixing-solvent system: Theory and experiment

It has been shown that, under specific conditions, a demixing-solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol-gel) and demixing-solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing-solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2-methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc.     

Spherical steel containments of pressurized water reactors under accident conditions: Investigation program and first results

The investigations will deal with the mechanical behavior of a free standing spherical containment shell built for the latest type of a German pressurized water reactor. The diameter of the containment shell is 56 m. The wall thickness is 38 mm. The material used is the ferritic steel 15MnNi63.The investigation program includes theoretical as well as experimental activities and concerns four different accidents which are beyond the scope of the common design and licensing practice: containment behavior under quasi-static pressure increase up to containment failure; containment behavior under high transient pressures; containment vibrations due to earthquake loadings (consideration of shell imperfections); containment buckling due to earthquake loadings. First results concerning the containment behavior under quasi-static pressure increase are presented. It turns out that the mechanical failure of the containment shell is controlled by plastic instability. A computer program to describe this problem has been developed and membrane tests to check the computational methods have been carried out.     

Heat transfer evaluation of impingement cooling in hot rolling of shaped steels

The accuracy of mathematical modelling is strongly influenced by the boundary conditions assumed. A shape rolling mill was instrumented to provide on-line temperature measurements during hot rolling of steels. An inverse heat conduction technique was used to convert the measurement data to surface heat fluxes and heat transfer coefficients. The heat transfer coefficient or heat flux could then be used as the necessary boundary condition for the computation of temperature field in the entire roll and workpiece by means of conventional heat transfer analysis. The heat transfer phenomena involved and the influence of the major operating parameters on the heat transfer results have also been discussed. Finally, the paper has shown that the numerical evaluation procedure adopted has at least the same influence on the results as the accuracy of temperature sensors and the properness of experiment design.     

Polymerization of acrylamide in inverse microemulsion in the presence of mixtures of oleophilic and hydrophilic surfactants

The preparation of single-phase toluene/sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Φ_aw of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20°C three viscosity maxima are observed. At 50°C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5–8 mPa· s while the second, most prominent peak still marks the level of ca. 250 mPa· s. The polymerization of acrylamide in dispersion systems is initiated by water-soluble ammonium peroxodisulfate (APS) and oilsoluble dibenzoyl peroxide (DBP) at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Φ_aw values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Φ_aw value of ca. 30%, irrespective of the nature of initiator. For Φ_aw values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some sings of shallow minimum close to Φ_aw of 50%.     

Polychlorierte Biphenyle (PCB) im menschlichen Fettgewebe

Zusammenfassung Die vorliegende Arbeit beschreibt die Kontamination menschlichen Fettgewebes mit den sechs als Indikator-Kongeneren bekannten Polychlorbiphenylen, mit PCB Nr. 49 und den Mischinducern PCB Nr. 156, 170 und 189. Die niedrig chlorierten Biphenyle Nr. 28, 49 und 52 konnten nicht nachgewiesen werden, die Konzentration von PCB Nr. 101 betrug im Mittel 9 g/kg. Die Gehalte von PCB Nr. 138, 153 und 180 lagen geringfügig unter den von der DFG angegebenen Werten. Der Anteil der Mischinducer Nr. 138, 156, 170 und 189 machte nahezu 40% der Gesamtbelastung aus. Die Höhe der PCB-Kontamnation des Fettgewebes war altersabhängig, wobei für die Gruppe der 61-bis 70jährigen mit Ausnahme von PCB Nr. 101 ein sprunghafter Anstieg der Konzentrationen beobachtet wurde.

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Polychlorinated biphenyls in human adipose tissue

Summary This study describes the contamination of human adipose tissue with six selected polychlorinated biphenyls (PCB) known as indicator congeners, with PCB no. 49 and the mixed inducer PCB nos. 156, 170, and 189. The low chlorinated biphenyls nos. 28, 49, and 52 could not be found in the tissue samples, while the average concentration of PCB no. 101 was 9.0 g/kg. The content of PCB nos. 138, 153, and 180 was slightly below the values published by the Deutsche Forschungsgemeinschaft (DFG). The mixed inducer nos. 138, 156, 170, and 180 amounted to approximately 40% of all the PCBs measured. The PCB contamination was positively correlated with age: for the age group 61–70 years, with the exception of PCB no. 101, a distinct increase in the concentrations could be observed.

     

Calculation of countercurrent separation processes—III. Computation of two interlinked columns.

The relaxation procedure is used for solution of two interlinked distillation columns. Both approaches-sequential iterative method and the block relaxation technique are compared. A new algorithm making use of simultaneous solution of all equations is proposed.     

Improvement of vascular dysfunction and blood lipids of insulin-resistant rats by a marine oil-based phytosterol compound

The syndrome that is characterized by obesity, insulin resistance, and hyperlipidemia is increasingly prevalent in all prosperous societies. It is now recognized as a major contributor to cardiovascular disease. Vascular dysfunction in the form of hypercontractility and impaired nitric oxide-mediated relaxation is a significant component of cardiovascular disease, predisposing to ischemic events. The JCR:LA-cp strain of rats exhibits all major aspects of the obesity/insulin resistance syndrome, including vascular dysfunction and ischemic lesions of the heart. Dietary lipid intake may have a marked effect on plasma lipid levels and, potentially, on vascular disease. We have investigated the effects of a novel preparation, ONC101 (a phytosterol esterified with fish oil), on plasma lipids and vascular function in the insulin-resistant JCR:LA-cp rat. Treatment of obese male rats with ONC101 from 8 to 12 wk of age resulted in no change in plasma lipid concentrations at 0.5 g/kg body weight. At the higher dose of 2.6 g/kg, plasma TG fell 50% (1.26 vs. 2.59 mmol/L, P<0.002) and cholesterol esters were significantly reduced (1.34 vs. 1.61 mmol/l, P<0.002). Food intake and body weights were unaffected by ONC101 treatment. At the low dose of 86 mg/kg, the hypercontractility of aortic rings in response to phenylephrine was normalized and the relaxant response to acetylcholine was significantly improved. The results indicate that ONC101 at high doses has significant hypolipidemic effects and, at very low doses, has beneficial effects on endothelial and vascular smooth muscle cell function. Deceased, June 22, 2001.     

MEASUREMENT AND COMPUTATION OF PHYSICO-CHEMICAL PROPERTIES OF SUGAR SOLUTIONS

At the Department of Chemistry and Technology of Saccharides, Institute of Chemical Technology in Prague, we study technically important physical properties of sugar solutions. This paper deals with some results of measurement and correlation of boiling point elevation and density.

The present system of tables or nomograms of physical properties of sugar solutions is not satisfactory for automated data processing. In a critical analysis of the existing material it appears that physico-chemical data for sugar solutions were often compiled over ranges of variables which were interesting for laboratory control and not for engineering computations. That all calls for purposeful completion of data in the regions where they are lacking. Additionally, it calls for revision of tabulated values from the literature and for transformation of the tabulated data to functional relationships in order to make computation equations both precise and simple