Effect of fillers on thermal and mechanical properties of polyurethane elastomer

The effects of five different types of fillers on the thermal and mechanical properties of hydroxyl-terminated polybutadiene-based polyurethane elastomers were explored to develop a filled polyurethane elastomeric Liner for rocket motors with hydroxyl-terminated polybutadiene-based composite propellants. Two types of carbon black, silica, aluminum oxide, and zirconium(III)oxide were used as filler. Based on the improvement in the tensile properties and the erosion resistance achieved in the first part of the study, an ISAF-type carbon black was selected to be used as the main filler in combination with an additional filler, The second part involves the investigation of polyurethane elastomers containing a second filler in various amounts in addition to the ISAF-type carbon black used as the main filler. In addition to the thermal and mechanical properties, the processability of the uncured polyurethane mixtures were also explored by measuring the viscosity in this second part of the study. The studied fillers do not considerably change the thermal degradation temperatures and the thermal conductivity of the polyurethane elastomers with a filler content up to 16 wt %. The best improvement in the erosion resistance and tensile strength of the polyurethane elastomers with additional fillers is also achieved when filled with the ISAF-type carbon black, whereas the use of zirconium(III) oxide as additional filler provides almost no improvement in these properties. Viscosity of the uncured polyurethane mixtures increases with the increasing filler content and with the decreasing particle size of the filler. Aluminum oxide-filled elastomers seem to be the most suitable compositions having sufficiently high thermal and mechanical properties, together with the processability of uncured mixtures. (C) 1998 John Wiley & Sons, Inc

Anomalous origin of the right vertebral artery from the ascending aorta in the presence of an aberrant right subclavian artery

We present a case of a 63-year-old man who was admitted to the hospital due to an acute coronary syndrome. Angiographic and magnetic resonance angiography examination showed an abnormal right vertebral artery originating from the ascending aorta, just above the left coronary sinus Valsalva in addition to aberrant retro-esophageal right subclavian artery. The variations and the incidence of various abnormal origins of the right vertebral artery are also reviewed

Modeling and rheology of HTPB based composite solid propellants

The propellant with the minimum viscosity required for a defect-free casting can be obtained by proper selection of the size and fractions of solid components leading to maximum packing density. Furnas' model was used to predict the particulate composition for the maximum packing density. Components with certain size dispersions were combined to yield a size distribution that is closest to the optimum one given by Furnas for maximum packing. The closeness of the calculated size distribution to the optimum one was tested by using the least square technique. The results obtained were experimentally confirmed by viscosity measurement of uncured propellants having HTPB binder and trimodal solid part accordingly prepared by using aluminum (volumetric mean particle diameter of 10.4 mu m) and ammonium perchlorate with four different sizes (volumetric mean particle diameters: 9.22, 31.4, 171, and 323 mu m). The experimental measurements showed that the compositions for the minimum viscosity are in good agreement with those predicted by using the model for maximum packing. The propellant consisting of particles with mean diameters of 10.4, 31.4, and 323 mu m was found to yield the minimum viscosity. This minimum viscosity was observed when the fraction of the sizes with respect to total solids was 0.141, 0.300, and 0.559, respectively

Comparative tear concentrations of topically applied ciprofloxacin, ofloxacin, and norfloxacin in human eyes

The tear pharmacokinetic profiles of 0.3% ciprofloxacin, 0.3% ofloxacin, and 0.3% norfloxacin ophthalmic solutions after a single drop topically administrations in the eyes of 30 healthy volunteers were evaluated. Tear samples collected at 30, 120, 180, and 240 minutes, were analyzed for drug concentrations by high performance liquid chromatography (HPLC) with fluorometric detection. Topically applied ciprofloxacin, ofloxacin, and norfloxacin achieved the mean tear concentrations (mean +/- SD) of 11.28 +/- 6.98, 6.52 +/- 4.06, and 13.28 +/- 8.78 mu g/g at 30 min, and then fell to 3.52 +/- 1.30, 4.82 +/- 1.80, and 5.79 +/- 4.80 mu g/g at 240 min, respectively. Topical norfloxacin achieved mean tear level significantly higher than ofloxacin at 30 min (p=0.031). There were no statistically significant differences in the mean tear levels of ciprofloxacin versus ofloxacin (at 30, 120, 180, and 240 min), ciprofloxacin versus norfloxacin (at 30, 120, 180, and 240 min) and ofloxacin versus norfloxacin (at 120, 180, and 240 min). However, the mean tear levels, 240 min after dosing ciprofloxacin and norfloxacin, fell to the statistically significant concentrations (p=0.02 and p=0.01, respectively). But, it is concluded that concentrations of ciprofloxacin, ofloxacin, and norfloxacin in tears were still significantly greater than the minumum inhibitory concentrations for the most sensitive organisms, 240 min after a single drop application

Penetration of topically applied ciprofloxacin, norfloxacin and ofloxacin into the aqueous humor of the uninflamed human eye

This study was undertaken to compare aqueous humor penetration of topical 0.3% ciprofloxacin, 0.3% norfloxacin and 0.3% ofloxacin in 63 patients undergoing cataract surgery. The patients were divided into two groups. Group 1 (long-term treatment) involved 30 patients undergoing cataract extraction who received either 0.3% ciprofloxacin, 0.3% norfloxacin or 0.3% ofloxacin topical drops. Each patient was preoperatively given a single drop per hour six times. At the time of surgery, 0.1 mi aqueous fluid was aspirated from the anterior chamber and immediately stored at -70 degrees C. Topically applied ciprofloxacin, ofloxacin and norfloxacin achieved mean aqueous humor levels of 2.80+/-1.07, 2.95+/-1.19 and 1.50+/-0.48 mu g/ml respectively. There was no statistically significant difference in intraocular mean aqueous levels of ciprofloxacin versus ofloxacin. Topical ciprofloxacin and ofloxacin achieved mean aqueous humor levels significantly higher than norfloxacin (p<0.001 and p<0.0008 respectively)

Proteasome Inhibitor Bortezomib Increases Radiation Sensitivity in Androgen Independent Human Prostate Cancer Cells

OBJECTIVES To investigate the effects of a strong proteasome inhibitor, bortezomib alone or in combination with radiotherapy on androgen-independent DU145 human prostate cancer cells. Proteasomes play important roles in cell cycle, proliferation, apoptosis, angiogenesis, and cellular resistance to chemotherapy and radiotherapy. METHODS Increasing concentrations of bortezomib alone or in combination with radiation were applied to DU145 cells and IC50 values that inhibited cell growth by 50% were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium- bromide assay. Apoptosis was determined using annexin V staining by flow cytometry. mRNA levels of proapoptotic caspase-3 and antiapoptotic Bcl-2 genes were examined by reverse transcriptase polymerase chain reaction. RESULTS The IC50 value of bortezomib was found to be 28 mu M although 400- and 800-cGy radiation decreased the cell proliferation by 14% and 28%, respectively. In 400- and 800-cGy radiation applied DU145 cells, IC50 value of bortezomib decreased to 23- and 12 mu M, respectively. Exposure to 5 mu M bortezomib for 48 hours caused apoptosis in 35% of the population whereas 800-cGy radiation resulted apoptosis in 14% of cells. However, 42% of DU145 cells that were exposed to 800 cGy and 5 mu M bortezomib underwent apoptosis. Reverse transcriptase polymerase chain reaction results showed a significant decrease in mRNA levels of antiapoptotic Bcl-2 gene and an increase in proapoptotic caspase-3 gene expression in the combination group compared to control group. CONCLUSIONS Bortezomib increases radiation sensitivity in androgen-independent human DU145 prostate cancer cells through inhibition of Bcl-2 and induction of caspase-3 genes. UROLOGY 75: 793-798, 2010. (C) 2010 Elsevier Inc.Wo