Effect of the structure of cationic polysulfone on the flocculation of kaolinite

The behavior of polycations as flocculants for kaolinite was examined by means of turbidity measurement, with the use of the following four kinds of cationic polysulfones, with molecular weights ranging from 14,000 to 330,000; diallyldimethylammonium chloride SO₂ copolymer [P(DADMAmCl? SO₂)], diallyldiethylammonium chloride–SO₂ copolymer [P(DADEAmCl? SO₂)], diallylmethylamine hydrochloride–SO₂ copolymer [P(DAMA? HCl? SO₂)], diallylamine hydrochloride–SO₂ copolymer [P(DAAHCl? SO₂)]. The effect of the degree of polymerization on the flocculation was remarkable at low molecular weight range. The flocculation value, which is defined as the quantity of the polycation required to obtain 50% transparency at 660 mμ of the supernatant fluid of 2% kaolinite suspension, was inversely proportional to the degree of polymerization to the 0.734 power in the case of P(DADMAmCl? SO₂). This can be understood as the extension of Schulze-Hardy's law. The four different kinds of polysulfones having a similar molecular weight show almost the same capacity for flocculation in acidic or neutral solution. In alkaline solution, however, P(DAMAHCl? SO₂) and P(DAA? HCl? SO₂) are less effective and have higher flocculation values than P(DADMAmCl? SO₂) and P(DADEAmCl? SO₂), which are classified as polyquaternary ammonium chlorides. Moreover the difference increases with increasing pH. This may be attributable to the difference of the dissociability of the polycation. The degree of dissociation of P(DAMA? HCl? SO₂) or P(DAA? HCl? SO₂) decreases with increasing pH and more additive is required to neutralize negative charges on kaolinite. On the other hand, P(DADMAmCl? SO₂) and P(DADEAmCl? SO₂) are almost completely dissociated and are good flocculants over a wide range of pH.     

Short communication: Diurnal profiles of conjugated linoleic acids and trans fatty acids in ruminal fluid from cows fed a high concentrate diet supplemented with fish oil, linseed oil, or sunflower oil

Trans-18:1 and 18:2 isomer composition in ruminal fluid during the daily feeding cycle was examined in 3 cows fed a high concentrate diet (35:65) with 5% (DM basis) sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) in a 3 x 3 Latin square with 3 4-wk periods. Grass hay and concentrate mixtures were fed at 0900, 1300, and 1700 h daily. Ruminal fluid was collected at 0900, 1100, 1300, 1500, 1700, 2000, and 0000 h. Feeding SO resulted in the greatest mean concentrations (% of total fatty acids) of trans10,cis12-18:2 and cis9,trans11-18:2. In particular, trans10,cis12-18:2 with SO was greater at 1500 (0.29%), 2000 (0.34%), and 0000 h (0.25%) relative to 0900 h (0.07%). Cis9,trans11-18:2 concentration increased from 0.47% at 0900 h to a peak of 2.06% at 1100 h; it remained greater than the percentage determined at 0900 h at 1300 (1.4%) through 0000 h (1.1%). Concentration of trans11,cis15-18:2 was greatest with LO, ranging from 3.3% (0900 h) to a peak of 11.4% at 2000 h. Mean trans10-18:1 concentration ranked by diet was SO > FO > LO. Peak trans10-18:1 with SO was observed at 1700 h (14.9%) compared with 0900 h (5.1%). Trans11-18:1 did not differ with diet or time. Stearic acid decreased over time with all diets reaching minimum concentrations at 1700 to 2000 h relative to 0900 h. Feeding FO, however, decreased mean 18:0 concentration 4-fold compared with LO or SO. The moderate effect on concentration of trans-18:1 coupled with accumulation of 18:2 intermediates and the decrease of 18:0 over time suggest that oils reduced the biohydrogenation of 18:2 isomers to trans-18:1.     

Spreading depression elicited by thermal effects of ultrasonic irradiation of cerebral cortex in rats

Dysbaric osteonecrosis is a major hazard to compressed air workers and an increasing hazard to divers. Symptomless osteonecrosis is best recognised by radiology and it is of fundamental importance that interpretation be reliable and accurate. There is much controversy concerning the significance of bone islands and cystic areas; several authors report bone islands and cystic areas to be up to eight times more frequent in compressed air workers and divers and believe that these represent positive evidence of osteonecrosis. Skeletal radiographs of 100 Royal Navy divers, all of whom were at risk to osteonecrosis were matched for age and rank with 100 controls, none of whom had been exposed to high pressures. The radiographs were interpreted by three radiologists working independently without knowing whether the radiographs were in the diving or control group. It is concluded that bone islands, cystic areas and sclerotic areas, as described in this text, occur with equal frequency in divers as in the normal population and do not represent positive evidence of osteonecrosis. The report includes autopsy studies of the proximal femur and proximal humerus in six diving fatalities. Five bone islands in the proximal humerus and one in the femoral neck were studied in bones removed from five divers. In the sixth case a cyst was seen to develop radiologically in the femoral neck and then reduce in size over 3 years and 10 months. Slab radiographs and histological section in all cases show no evidence of osteonecrosis.     

Biodegradable polylactide/montmorillonite nanocomposites

Our continuing research on the preparation, characterization, materials properties, and biodegradability of polylactide (PLA)/organically modified layered silicate (OMLS) nanocomposites has yielded results on PLA/montmorillonite nanocomposites. Montmorillonite (mmt) modified with dimethyldioctadecylammonium cation was used as an OMLS for nanocomposite preparation. The internal structure of nanocomposites on the nanometer scale was established with the use of wide-angle X-ray diffraction patterns and transmission electron micrographic observation. All nanocomposites exhibited significant improvement in crystallization behavior, mechanical properties, flexural properties, heat distortion temperature, and O2 gas permeability when compared with pure PLA.     

Tunable Continuous-Wave Yb:YLF Laser Operation with a Diode-Pumped Chirped-Pulse Amplification System

We have demonstrated a diode-pumped Yb:LiYF(4) (Yb:YLF) laser oscillator for the first time to our knowledge. A wide tuning range of 25 nm and a high slope efficiency of 50% were obtained at a high laser-diode pump intensity of 100 kW/cm(2). Emission and absorption spectra of the Yb:YLF crystal at 8 K represent a wide laser gain width of 38 nm, indicating efficient laser operation similar to that of a four-level laser system with a reduced saturation fluence of 11 J/cm(2).     

Expression of a gene encoding chitinase (pCA 8 ORF) from Aeromonas sp. no. 10S-24 in Escherichia coli and enzyme characterization

A gene encoding chitinase from Aeromonas sp. no. 10S-24 was expressed using pTrc99A in Escherichia coli JM 105 which yielded a 5-fold higher activity than when pUC19 was used. Three different truncated enzymes (SA-1, SA-2 and SA-3) were obtained after purification. Their isoelectric points were 7.0, 6.9, and 6.7, respectively. The enzymes showed two optimum pHs, 4.0 and 7.0, when incubated with ethylene glycol chitin as the substrate, and were stable over a wide pH range (3.0-9.0). The optimum temperature was 60 degrees C and the enzymes were stable up to 50 degrees C. The chitinases exhibited wide substrate specificities for chitin-related compounds.     

Establishment of a simple system to analyse the molecular interaction in the agglutination of Saccharomyces cerevisiae

Saccharomyces cerevisiae a-agglutinin, which is involved in mating and covalently anchoring to the cell wall, consists of two components, Aga1p and Aga2p, whose syntheses are individually regulated. To facilitate the analysis of the protein-protein interaction on agglutination between a- and alpha-agglutinins, the construction of a yeast strain (MATa) with the functional protein prepared by genetic fusion of Aga1p- and Aga2p-encoding genes and by the expression system using the UPR-ICL promoter derived from the n-alkane-assimilating yeast, Candida tropicalis, which is functional under the condition of lower glucose concentration was tried and the agglutination ability of the constructed strain was evaluated with a yeast strain (MATa) which expressed AGalpha1 encoding alpha-agglutinin under the control of the same promoter. The genes were integrated into the yeast chromosomes. Cell agglutination between both (MATa) strains was observed microscopically when these two strains were mix-cultured to a glucose-decreased concentration. The agglutination was further confirmed by the sedimentation test and by the quantification using a filter. These results proved that the constructed Aga1p-Aga2p fusion protein was enoughly functional for the interaction with the Agalpha1 protein, and that this phenomenon occurred dependent on glucose concentration, but independent of the peptide pheromones secreted by the cells of the opposite mating types. Using this system, the role of two disulphide linkages between Aga1p and Aga2p on the binding activity between Aga2p and Aga1p was first evaluated. Under the treatment by the SH-compound (dithiothreitol), in which Agalpha2p is easily released into the medium from the intact cell surface, the Aga1p and Aga2p fusion protein was a good tool to make clear the role of the disulphide linkages. As a result, the linkages had a significant effect on not only the assembly but also the binding activity. The novel and simple system described here may further facilitate the study of molecular interaction in agglutination.     

TRANSIENT THERMAL SINGULAR STRESSES OF MULTIPLE CRACKING IN A W-Cu FUNCTIONALLY GRADED DIVERTOR PLATE

We consider the transient thermal singular stresses of multiple cracking in a functionally graded divertor plate due to a thermal shock. The plate is made of a graded layer bonded between a homogeneous substrate and a homogeneous coating, and it is subjected to a cycle of heating and cooling on the coating surface of the plate. The surface layer contains a parallel array of embedded or edge cracks perpendicular to the boundaries. The thermal and elastic properties of the material are dependent on the temperature and the position. Finite element calculations are carried out, and the transient thermal stress intensity factors are shown graphically.