Synthesis of permselective membranes by radiation-induced grafting of N-vinylpyrrolidone onto poly(tetrafluoroethylene–hexafluoropropylene–vinylidene fluoride) (TFB) films

The radiation initiated grafting of N-vinylpyrrolidone (NVP) onto poly(tetrafluoroethylene–hexafluoropropylene–vinylidene fluoride) (TFB) films has been investigated using a direct radiation technique. Different solvents were used for diluting the monomer, and it was found that dioxane is suitable for this grafting system. The influence of other grafting parameters, such as inhibitor, monomer concentration and dose rate, on the rate and yield of grafting was studied. The dependence of the grafting rate on the monomer concentration was found to be of the 1.1 order. Some physicochemical properties, such as swelling, thermal behaviour, mechanical and electrical conductivity, were investigated. A study was made to gain a better understanding of the observed water uptake using IR spectroscopy and scanning electron microscope (SEM) analysis. The possibility of some practical uses, e.g. removal of heavy metals from solution by grafted membranes was investigated. © 1999 Society of Chemical Industry     

On the transport of a suspended particle in flow through the entrance region of a tube

The motion of a single, spherical particle, released at different radial positions at the inlet of the entrance region of a straight circular laminar flow tube (Re = 260), was studied theoretically. Radial migration of the particle, either toward the tube center or toward the tube wall, was predicted. Based on the hypothesis that the particle experienced a lift force which was produced by the vorticity in the boundary layer and a velocity difference between the center of the suspended particle and the fluid medium, an inertia-vorticity fluid dynamic model was formulated to analyze the particle radial motions. Computational flow dynamics (CFD) solutions obtained from a 9.8 mm diameter tube model included the resulting particle loci for three particle radii (a = 0.1 cm, 0.085 cm, 0.050 cm), with the particle entry at various radial positions. The computation also covered a range of different particle entry speeds. The results showed that the particle migrates toward the tube center if it lags behind the medium in the core region; otherwise, it migrates toward the tube wall. Additional flow experiments were conducted in a circular (2R = 10.2 mm), 300 mm long straight tube. A small polystyrene sphere (2a = 1.72 mm, density rho p = 1.014 g.cm-3) was released at the inlet (X = 0, eta/R = 0.48) with two dimesionless release velocities (omega p = 0, and omega p > 1.0). The recorded particle traces agree well with the computational model.     

Cerebral apoplexy in children

Stroke in children is rare. No really good studies of the incidence are available, an estimate, however, is 2-3/100,000 children per year. In this paper we discuss the pathophysiology and the many different causes of stroke in children. In many of the cases more than one prothrombotic condition exists. If the cause is not obvious an extensive programme of examinations is recommended. This is important not only in order to give the best individual treatment, but also necessary in order to decide whether the stroke has a genetic cause. Initially, the treatment is symptomatic, attaching importance to achieving good perfusion of the cerebrum and lowering the energy consumption of the cerebrum. The rational treatment might be prompt reperfusion by thrombolytic medicine: this regime has been tried in adults, but as yet no consensus about this treatment modality exists. In some cases causal treatment is possible. If the stroke has a genetic cause genetic consultation is important and prenatal investigations might be possible. Overall, the mortality in stroke in children is about 25%. About 25% will live without any sequelae and approximately 50% of the children will disabled to a greater or lesser extent.     

The effect of hole diameter on the torsional mechanical properties of the equine third metacarpal bone

The torsional monotonic structural material properties of equine metacarpi with or without, either a 5/16 inch or 3/8 inch diameter bicortical lateromedial middiaphyseal hole were assessed to determine the effect of a hole on metacarpal strength. Torsional stiffness was not significantly effected by the presence of a bicortical hole, whereas yield and failure angles, torques and energies of metacarpi with a hole were 51% to 97% of those of intact bones. Significant differences were not apparent for yield and failure mechanical properties between metacarpi with a 5/16 inch diameter hole and metacarpi with a 3/8 inch diameter hole; however, postyield mechanical properties were lower for metacarpi with a 3/8 inch hole. Whereas some metacarpi with a 5/16 inch hole were capable of plastic deformation before failure, metacarpi with a 3/8 inch diameter hole appeared to have sufficient stress concentration to propagate complete fracture on structural yield.     

Enzyme linked immunosorbent assay for detecting benzodiazepines in urine

A relatively simple ELISA technique was developed for the detection of a range of benzodiazepines (BZs) in urine. The assay employs a mouse anti-oxazepam antibody that is highly specific for the BZs. The limit of detection using 10 microliters samples of urine was 0.3 microgram ml-1 oxazepam. N-Desmethyldiazepam showed equal cross-reactivity to oxazepam, 11 BZs cross-reacted weakly and flurazepam and chlordiazepoxide did not cross-react at levels reported to be found in urine. No cross-reactivity was observed with drugs of abuse and a range of therapeutic drugs commonly found in urine. The assay was used as a screen to detect the presence of BZs in urine from 88 addicts that had been screened by the EMIT technique and a radioreceptor assay (RRA) for BZs. The ELISA produced two false negatives that were EMIT and RRA positive whereas the EMIT produced four different false negatives that were positive by both ELISA and RRA. Thirty-three positives were common to all three assays. The ELISA was also used to monitor nitrazepam-like activity in the urine of a greyhound receiving 5 mg oral medication and the results were compared with those obtained by RRA. Both assays were able to detect nitrazepam-like activity for up to 10 h post-administration.     

Hepatoprotection in ethinylestradiol-treated rats is provided by tauroursodeoxycholic acid, but not by ursodeoxycholic acid

Ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) have been suggested as potential treatments for drug-induced cholestasis. It was therefore decided to study the effects of administration of UDCA or TUDCA on individual serum bile acid concentration, conventional liver tests and associated hepatic ultrastructural changes in ethinylestradiol-treated (EE) rats mg/kg per day). Control rats were treated s.c. with propylene glycol. EE-treated rats were randomly assigned to receive daily i.p. injections of placebo, TUDCA or UDCA. Four rats in each group were treated for 4 consecutive days, and a second four for 14 days. After 4 days of treatment, the serum levels of cholic acid and taurocholic acid were significantly increased in EE-treated rats. None of the conventional liver tests were significantly different among the four groups. After 14 days of treatment the serum levels of cholic acid, chenodeoxycholic acid, glycocholic acid, glycochenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, bilirubin, alkaline phosphatase and gamma glutamyltransferase were significantly raised in EE and EE plus UDCA treated rats. EE plus TUDCA treated rats, however, had no significant changes in these individual serum bile acids or conventional liver tests. The ultrastructure of livers from EE plus TUDCA treated rats was similar to those of controls. On the other hand, EE and EE plus UDCA rats both showed a significant reduction in sinusoidal microvilli. These results show that treatment of rats for 4 days with EE induces significant rises in the serum concentrations of two individual bile acids and that TUDCA protects against this.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of gene organization in the zwf region of the genomes of the cyanobacteria Synechococcus sp. PCC 7942 and Anabaena sp. PCC 7120

The region of the genome encoding the glucose-6-phosphate dehydrogenase gene zwf was analysed in a unicellular cyanobacterium, Synechococcus sp. PCC 7942, and a filamentous, heterocystous cyanobacterium, Anabaena sp. PCC 7120. Comparison of cyanobacterial zwf sequences revealed the presence of two absolutely conserved cysteine residues which may be implicated in the light/dark control of enzyme activity. The presence in both strains of a gene fbp, encoding fructose-1,6-bisphosphatase, upstream from zwf strongly suggests that the oxidative pentose phosphate pathway in these organisms may function to completely oxidize glucose 6-phosphate to CO2. The amino acid sequence of fructose-1,6-bisphosphatase does not support the idea of its light activation by a thiol/disulfide exchange mechanism. In the case of Anabaena sp. PCC 7120, the tal gene, encoding transaldolase, lies between zwf and fbp.