High-temperature and ageing properties of high-crystalline TOR-filled SBR vulcanizates

The influence of a co-cross-linkable processing aid, Trans-polyoctenylene (TOR), on hightemperature stress-strain properties and ageing of filled styrene butadiene rubber (SBR) vulcanizates, was studied. Three different cross-linking systems, conventional (CV), semiefficient (SEV) and efficient (EV), with respect to SBR were included. A linear regression equation has been obtained between vulcanizate modulus (200%), TOR dosage and sulphur/accelerator ratio at different test temperature. A similar equation has also been found with tensile strength at 120 °C. Thermal analysis, Fourier transform-infrared spectroscopy and a few solid-state ¹³Carbon nuclear magnetic resonance spectroscopic techniques were performed to get insight into the structural changes that occur between TOR and SBR during cross-linking. A plausible mechanism of the interaction between TOR and SBR has been suggested. Based on the property retention of the vulcanizates at room as well as at high working temperature, an optimization of properties between the CV and EV systems has been attempted by the modification of the CV system using TOR.     

Effect of testosterone replacement on whole body glucose utilisation and other cardiovascular risk factors in males with idiopathic hypogonadotrophic hypogonadism

BACKGROUND: Excessive testosterone in males or estrogens in females could explain their differences in coronary heart disease event rates. As a contraceptive testosterone is likely to be used at large scale the role of testosterone in increasing the risks of coronary heart disease needs investigation. AIM: To look at the role of testosterone in development of insulin resistance and other cardiovascular risk factors. DESIGN: Prospective, before-after study on ten male subjects with idiopathic hypogonadotrophic hypogonadism pre- and post-testosterone replacement therapy; outcome measures: anthropometry, lipoprotein profile and M value (whole body glucose disposal rates on standard hyperinsulinemic euglycemic clamp; at insulin infusion rate: 40 mU x (m-2)). RESULTS: Pre-treatment serum testosterone was 0.43 (0.515) ng x mL(-1), LH was 1.29 (0.08) IU x L(-1), and FSH was 1.54 (0.08) IU x L(-1). None had glucose intolerance. After replacement testosterone levels increased to 9.4 ng x mL(-1) (p=0.0005); weight increase of 5.0 kg (p=0.140), body mass index increase of 1.2 kg x m(-2) (p=0.28), and the change in waist to hip ratio (p=0.31) were not statistically significant. M-value (mg x kg x min(-1)) did not change after testosterone therapy (5.86 [0.72] vs 5.29 [0.82], p=0.62). Insulin levels (mU x L(-1)) achieved during the clamps were 89.5 (14.2) before and 146 (32.2) after androgen therapy (p=0.127). There was no change in glucose area under curve (mg x min x dL(-1)) (14406 [502.2] vs 12557 [826.5], p=0.312). On testosterone replacement therapy total and LDL cholesterol levels (mg x dL(-1)) declined (122.5 [13.4] vs 91.6 [5.0], p=0.04; 65.9 [9.9] vs 39.4 [7.3], p=0.05); Ratio of total cholesterol to HDL ratio also decreased significantly (p=0.05). Changes of serum triglycerides (p=0.25) and HDL cholesterol (p=0.19) did not attain statistical significance. CONCLUSIONS: Insulin sensitivity does not decrease on testosterone replacement therapy of male subjects with idiopathic hypogonadotrophic hypogonadism. Testosterone replacement was associated with decrease in other cardiovascular risk factors.     

Pulmonary arteriovenous fistula with cerebral arteriovenous malformation without hereditary hemorrhagic telangiectasia. Unusual case report and literature review

An unusual and rare case of a central pulmonary arteriovenous fistula (PAVF) with concomitant cerebral arteriovenous malformation (CAVM) in the absence of hereditary hemorrhagic telangiectasia is reported. Presentation was in the form of a cerebrovascular accident (CVA). Clinical presentations and management strategies of PAVF with associated CAVM are broadly discussed along with a pertinent literature review.     

Decentralized suboptimal load-frequency control of a hydro-thermal power system using the state variable model

State space modelling and synthesis of decentralized suboptimal load-frequency control for hydro-thermal power systems are described in this paper. The state space models are derived by the partial fraction technique for reheat steam turbines, hydro turbines and hydro governors having numerator dynamics. Decentralized suboptimal load-frequency controls are synthesized by using the method of minimum error excitation and their performance is analysed as a function of tie-line power level. It is shown that the suboptimal control with feedback of some, but not all, of the remote area state variables is a feasible alternative to the optimal control, whereas local control without feedback of any remote state variable is inadequate for stabilizing the system.     

Long-term erythropoietin expression in rodents and non-human primates following intramuscular injection of a replication-defective adenoviral vector

Erythropoietin (Epo)-responsive anemia is a debilitating complication of chronic renal failure and human immunodeficiency virus (HIV) infection that effects more than 150,000 Americans. Patients with Epo-responsive anemias are currently treated with repeated injections of recombinant human Epo. In the studies described in this report, we have examined the safety and efficacy of using a single intramuscular (i.m.) injection of replication-defective adenoviral vectors (RDAd) encoding Epo for the treatment of Epo-responsive anemias in both mice and non-human primates. Our results demonstrate that there is a threshold dose of virus (2.5-8 x 10(7) pfu/gram of body weight) which is required to obtain long-term Epo expression and polycythemia in both species. A single i.m. injection of mice with 10(9) pfu of an RDAd encoding murine Epo (AdmEpo) resulted in elevations in hematocrits from control values of 49 +/- 0.9% to treated values of 81 +/- 3%, which were stable for more than 1 year. Similarly, a single i.m. injection of a monkey with 4 x 10(11) pfu of an RDAd-encoding simian Epo (AdsEpo) resulted in elevations of hematocrits from control levels of 40% to treated levels of > or =70%, which were stable for 84 days. Intramuscular injection of monkeys with AdsEpo appeared to be safe in that we did not detect abnormalities in chest X-rays, serum chemistries, hematologic, or clotting profiles (apart from elevated hematocrits) or organ histologies during the 84-day time course of the experiment. Taken together, these results suggest the feasibility of using i.m. injection of RDAd for the treatment of Epo-responsive anemias in humans.     

Multispectral and joint colour-texture feature extraction for ore-gangue separation

Ore sorting is a useful tool to remove gangue material from the ore and increase the quality of the ore. The vast developments in the area of artificial intelligence allow fast processing of full color digital images for the preferred investigations. Three different approaches to color texture analysis were used for the classification of associated gangue from limestone and iron ore. All the methods were based on extensions of the co-occurrence matrix method. The first approach was a correlation method, in which co-occurrence matrices are computed both between and within the color bands. In the second approach, joint color-texture features, where color features were extracted from chrominance information and texture features were extracted from luminance information of the color bands. The last approach used grey scale texture features computed on a quantized color image. Results showed that the joint color-texture method was 98% accurate for limestone and 98.4% for iron ore gangue classification. It was further observed that the features showed better accuracy with 64 grey levels quantization.     

Removal of fluoride from drinking water by adsorption onto alum-impregnated activated alumina

The ability of the alum-impregnated activated alumina (AIAA) for removal of fluoride from water through adsorption has been investigated in the present study. All the experiments are carried out by batch mode. The effect of various parameters viz. contact time, pH effect (pH 2–8), adsorbent dose (0.5–16 g/l), initial fluoride concentration (1–35 mg/l) has been investigated to determine the adsorption capacity of AIAA. The adsorbent dose and isotherm data are correlated to the Bradley equation. The efficacy of AIAA to remove fluoride from water is found to be 99% at pH 6.5, contact time for 3 h, dose of 8 g/l, when 20 mg/l of fluoride is present in 50 ml of water. Energy-dispersive analysis of X-ray shows that the uptake of fluoride at the AIAA/water interface is due to only surface precipitation. The desorption study reveals that this adsorbent can be regenerated following a simple base–acid rinsing procedure, however, again impregnation of the regenerated adsorbent (rinsed residue) is needed for further defluoridation process.     

Deformation and energy absorption characteristics of microcellular ethylene‐octene copolymer vulcanizates

Compressive stress‐strain properties of unfilled, CaCO₃, silica and aluminum silicate filled closed‐cell microcellular ethylene‐octene co‐polymer vulcanizates were studied with variation of blowing agent loading (density). With decrease in density, the compressive stress‐strain curves for microcellular vulcanizates behave differently from those of the solid vulcanizates. The stress‐strain properties are found to be strain rate dependent. The log‐log plots of relative compressive moduli versus relative density of the microcellular vulcanizates show a fairly linear correlation. The energy absorption behavior was also studied from the stress‐strain properties. The efficiency, E, and Ideality parameter, I, were evaluated. These parameters were plotted against stress to find the maximum efficiency and maximum ideality region, which will make these materials suitable for cushioning and packaging applications. The cushioning factor, C, for microcellular vulcanizates has also been evaluated for various systems.     

Effect of fillers on the relaxation behavior of chlorobutyl vulcanizates

The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been studied. The primary relaxation (α‐transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (?60 to +100°C) and positron annihilation life time spectroscopy (?70 to +110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of –29 to –33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–10⁶ Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07–5%. The nonlinearity in tan δ and storage modulus has been explained on the concept of filler–polymer interactions and the interaggregate attraction (filler networking). The “percolation limit” of the fillers in the composites has been studied by DC conductivity measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3161–3173, 2006