Biodegradation study on poly(ε‐caprolactone) with bimodal molecular weight distribution

Poly(ε‐caprolactone) (PCL) of bimodal molecular weight distribution was exposed to the action of enzymes‐lipases from Aspergillus oryzae in phosphate buffer at pH 7 and 37°C, and those produced in situ by Bacillus subtilis in nutrient medium at 30°C for 42 days. The occurrence of biodegradation is proved on the basis of the weight loss, decrease of molecular weight, carbonyl index, crystallinity, and development of cracks on the PCL surfaces. In the case of Bacillus subtilis, the degradation (10 wt % loss of PCL) proceeds faster in comparison with lipase from Aspergillus oryzae (2.6 wt % loss of PCL), where the degradation process seems to stop during 14 days of experiment. The gel permeation chromatography results reveal that preferential degradation of lower molecular portion did not occur but it is assumed that PCL chains were cleaved in accordance with particular degradation mechanism that depends significantly on biological agent. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Computer-aided design and growth of single-walled carbon nanotubes on 4 in. wafers for electronic device applications

We have employed computer-aided furnace design and process simulation to optimize the conditions under which single-walled carbon nanotubes (SWCNTs) may be grown in high yields on 4 in. wafers for electronic device applications. Hydrokinetic simulations were performed to obtain optimized furnace structures and process conditions in terms of gas flow, temperature, and gas speed. Shower head structures and a flow isolation barrier were installed in an experimental 6 in. furnace, as suggested by the hydrokinetic simulations. To ensure clean surfaces and uniform catalyst islands, catalyst patterns were lifted off using Au films or polydimethylsiloxane. Photolithography was used to fabricate field-effect transistors with SWCNTs grown on 4 in. wafer substrates. The total yield of the nanotube devices increased from 30.5% to 96.4% after optimization.     

Changes in blood velocities of fetal circulation in association with fetal heart rate abnormalities: effect of sublingual administration of nifedipine

Nifedipine has been used to treat hypertension in pregnancy, and does not influence fetal or uteroplacental circulations in patients with preeclampsia. A 29-year-old multi-gravid woman presented at 32 weeks' gestation with significant elevation of her blood pressure. After sublingual administration of nifedipine, the blood pressure decreased from 208/122 to 136/96 mm Hg at 30 minutes. In her growth-retarded fetus with abnormal flow velocity waveforms, pulsatility index values for middle cerebral artery and umbilical artery did not change; however, peak systolic velocities, end-diastolic velocities, and time-averaged mean peak velocities for these arteries became significantly elevated. Simultaneously, severe variable decelerations and late decelerations occurred. The adverse effect of nifedipine on fetal circulation might occur in a growth-retarded fetus with abnormal flow velocity waveforms.     

Multiple wavelength bidirectional transmission for subscriber loop applications

A laboratory demonstration of two uniwavelength bidirectional transmission systems, one at 780 nm and another at 1300 nm, multiplexed on a standard single-mode fibre is described. Based on experimental results, a duplex-quadruplex system for the subscriber loop is possible, which again doubles the information carrying capacity of the fibre system.<>     

Plasma oxidation of Cu-Al alloy

Selective oxidation of Cu-1.0 wt % Al alloy was found to be achieved by using microwave plasma at 1073 K in a mixed gas of 10 % 0₂ and 90 % N₂ at a total pressure of 2 torr (∼266.644 Pa). The selective oxidation was confirmed by electron diffraction analysis of aluminium oxide particles, microstructural observations and hardness measurements of the internal oxidation layer. Electrical conductivity and the thermal expansion coefficient of the oxidized specimens were measured. The morphology and distribution of the aluminium oxide particles formed in the oxidized alloy is also discussed.     

Diamond deposition using anX-Y stage in a d.c. plasma jet chemical vapour deposition

Diamond was deposited using the substrate scanning mode in a d.c. plasma jet of the Ar-H₂-CH₄ system. Film thickness profiles, SEM and Raman spectra of the diamonds obtained revealed that uniformity of film thickness, crystal size and crystal quality was improved, but the deposition rate decreased with the scanning speed and the crystal quality was worse than that made in the centre of the flame without scanning.     

Posterior proctomucosectomy and ileal pull-through reconstruction: a new restorative procedure after total proctocolectomy

We reported a new method of restorative proctocolectomy using posterior approach and pull-through reconstruction. This method obviated transanal manipulation, a major factor causing damage to the internal sphincter, thus preventing fecal incontinence due to sphincter dysfunction. Also, temporary ileostomy was not necessary because the spout of an S-pouch was pulled down below the anal verge and its distal free end acted as a diverting stoma while the more proximal, healing zone (future anastomotic line) was kept from fecal contamination. This method was applied to a 32-year-old woman with familial polyposis coli and a 50-year-old woman with ulcerative colitis. Their bowel movements steadily decreased to three times and five times a day, respectively. There was no fecal leakage or perianal excoriation. The advantages as well as disadvantages of this method compared with the conventional techniques were discussed.     

Copper accumulation by a strain of Pseudomonas putida

A study on the copper accumulation by resting cells of copper-resistant bacteria, isolated from activated sludge and electroplating effluent, was conducted. The best selected strain, identified as Pseudomonas putida II-11, retained copper ions, Cu(II), as high as 6.5% of its dry weight. Bacterial cells grown in the sulphate-limiting medium had the highest copper removal capacity [RC, mg of Cu(II)/g of dry cells], while the presence of glucose or sodium azide did not affect Cu(II) RC of the bacterial cells. A possible mechanism of Cu(II) accumulation by this bacterium is suggested.