Graft and crosslinked copolymers by nucleophilic reaction between maleic anhydride copolymers and carbanions

Summary Grafting of polystyryl and copoly(styrene-b-isopren)yl maorocarbanions onto ethylene-maleic anhydride alternating copolymer was carried out under reaction conditions such as to obtain copolymers with middle-low grafting degree and long lateral chains. In order to ascertain the absence of secondary reactions, the coupling of n-BuLi with succinic anhydride vas investigated, and no secondary reaction vas observed. The graft copolymers, wich have molecular weights and elemental composition in good agreement with those expected, were studied by IR spectroscopy and DSC. Both spectra and calorimetric curves confirm the structures assigned to the copolymers. The tensile properties of the copolymers with copoly(styrene-b-isoprene) lateral chains were also investigated, The properties appear very dependent on the degree of grafting, on the solvent (benzene or THF) from which the specimens were deposited, and on their thermal history.     

Quasi-convex programming revisited

Summary The paper by S. Mititelu [8] is revisited, giving correct proofs of both necessary and sufficient conditions for the existence of solutions to a quasi-convex mathematical programming problem. The usual constraint qualifications established for such a problem, are then further weakened. I thank two anonymous referees for some useful suggestions on the first version of the present paper; any responsibility is however solely mine.     

Percutaneous ethanol injection under general anesthesia for hepatocellular carcinoma: 3 year survival in 112 patients

OBJECTIVE: The aim of this study was to determine whether the expression of thymidine phosphorylase by ovarian cancer cells correlates with the density of microvessels within the tumor, and with ultrasound-derived indices of blood flow. METHODS: Transvaginal ultrasonography with color Doppler imaging and pulsed Doppler spectral analysis was used to scan patients with an overt ovarian mass immediately before laparotomy. Sections of malignant tumors were analyzed for the cellular expression of thymidine phosphorylase and the intratumoral density of microvessels by immunohistochemistry using monoclonal antibodies to thymidine phosphorylase and factor VIII-related antigen, respectively. The main outcome measures were the histological classification of the tumor, the stage of the disease, whether or not the tumor cells were positive or negative for thymidine phosphorylase, the microvessel count and the peak systolic velocity (PSV). RESULTS: Forty-two tumors were studied (three of low malignant potential, 29 epithelial, four granulosa cell, two germ cell and four metastatic); 18 were stage I, six stage II, 11 stage III and three stage IV. Twenty-seven tumors (64%) were classified as thymidine phosphorylase-positive. The proportion of stage I tumors that was thymidine phosphorylase-positive (44%) was significantly lower (p = 0.022) than the corresponding value for stages II-IV (85%), but the values for microvessel count and PSV were similar. The microvessel count in thymidine phosphorylase-positive tumors was significantly higher than in thymidine phosphorylase-negative tumors (p = 0.005). Similarly, the PSV was significantly higher in thymidine phosphorylase-positive tumors (p = 0.009). There was a significant correlation between the microvessel count and the PSV (r = 0.354, p = 0.022). CONCLUSIONS: The expression of thymidine phosphorylase by malignant tumor cells is associated with an increase in microvessel density and PSV in patients with ovarian cancer.     

Gas jets in fluidized beds and spouts: A comparison of experimental behavior and models

Experimental data reviewed include pressure profiles, gas and solids axial and radial velocity profiles, and solids concentration in the jet and spout. Similarities and differences from experimental evidence available for spouts in spouted beds and jets in fluidized beds are discussed. Modelling procedures are compared.     

Smoke suppression by ammonium polyphosphate in poly(acrylonitrile) combustion

The influence of ammonium polyphosphate (APP) on the smoke emission of poly(acrylonitrile) (PAN) has been examined, and its mechanism of action as a smoke suppressant agent has been investigated. Smoke density and corresponding residual char data, as a function of temperature, were obtained in order to characterize the smoke propensity of PAN. The amount of generated smoke, both in smoldering and flaming conditions, was considerably lowered by the presence of APP, and higher char yields were obtained. Beside the smoke suppression, flame inhibition effect of APP on PAN was evidenced. Thermogravimetry (TG), oxygen index (OI), and nitrous oxide index (NOI) experiments were also performed. On the basis of our data, APP appears to act as a char-forming agent in PAN combustion. Both smoke suppression and flame inhibition effects can be considered a consequence of this action.     

SCRUBBING OF NITROGEN OXIDES WITH NITRIC ACID SOLUTIONS

A mathematical model is developed for an equilibrium stage analysis of nitrogen oxides absorption in nitric acid solutions. Using equilibrium data available from the literature, the model demonstrates that 15-35 wt% nitric acid may be efficiently used to reduce pollutant emissions in NO_x-containing gases having low degree of oxidation. Lower oxides of nitrogen accumulate in the liquid as nitrous acid which is carried away by the nitric acid solution. The scrubbed gas contains a reduced concentration of nitrogen oxides and has a higher degree of oxidation than the feed gas.     

Colour prediction of organic dye molecules on a microcomputer—a readily available form of the PPP-MO method for teaching and research

The Pariser-Parr-Pople molecular orbital (PPP-MO) method, which provides a way of calculating electronic absorption spectroscopic properties of organic dye molecules, such as the position of the absorption maximum in the visible spectrum, its intensity and polarisation direction, has been implemented in PASCAL language on a 64 kB Apple 11 computer. The system consists of two modes: (1) Graphic mode and (2) PPP mode, which are controlled separately or successively. The system occupies up to 32 kB of memory, needs 1 minifloppy disk in the entire execution of the program, and handles up to 30 atoms routinely with configuration interaction.     

Purification and properties of three albumins from Triticum aestivum seeds

Three albumins were isolated from bread wheat seeds by gel filtration on Sephadex G-100 and differential preparative disc-electrophoresis on polyacrylamide gel. The proteins were obtained in sufficient yield and purity to carry out characterisation studies. The electrophoretic mobilities of the three albumins in polyacrylamide discs in glycine—Tris medium, pH 9·5, were 0·28, 0·34 and 0·39 (referred to that of bromophenol blue taken as 1). The isoelectric points were 6·40, 6·40 and 5·35 and the molecular weights 17, 700, 18, 200 and 18, 900, respectively. The amino acid compositions of the purified albumins were very similar. The correlation of the purified albumins with those isolated from bread wheats by other authors is discussed.