Electrochemical polymerization of aniline on carbon fibers in aqueous toluene sulfonate solution

Polyaniline has been successfully formed by aqueous electrochemical polymerization on carbon fibers. The coatings were formed under potentiostatic conditions with toluene‐4‐sulphonic acid sodium salt as the electrolyte. The effect of monomer concentration, electrolyte concentration, and the applied potential on the rate of polymerization were studied. The amount of polyaniline coatings formed on carbon fibers increased with increased aniline and electrolyte concentration. Increasing the applied potential also increased the weight of coatings formed on the fibers. The presence of positive y‐intercept in the weight gain plots are attributed to the adsorption of the electrolyte on the fibers before electropolymerization. The effect of the electrochemical parameters on the degradation of the polymer has been analyzed using infrared spectroscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1503–1509, 2000     

Materials research at national aeronautical laboratory (contributions of S Ramaseshan)

Materials research programmes of the National Aeronautical Laboratory and Prof. Ramaseshan’s contributions to these are presented in this article.     

Optimal blood pressure control in treated hypertensive patients. Report from the Department of Health Hypertension Care Computing Project (DHCCP)

BACKGROUND: We wished to determine the range of treated systolic (SBP) and diastolic blood pressure (DBP) associated with the best survival in hypertensive patients. METHODS AND RESULTS: We conducted a cohort study of patients enrolled in the DoH Hypertension Care Computer Project. Five specialist hypertension clinics (95% of patients) and general practitioners (5%) followed 6214 patients (3070 men and 3144 women) with an average age of 52 years for a mean of 107 months. Total, cardiovascular, ischemic heart disease, (IHD) and stroke mortality were the outcome measures. Age-adjusted relative hazard rates were calculated giving the effect on mortality of systolic or diastolic pressure being higher by 1 mm Hg. In men the optimal level of SBP for all four measures of mortality was the lowest pressure range observed, 92 to 133 mm Hg (median 127). For women the treated SBP range of 96 to 148 mm Hg (median 137) was associated with a low total mortality and also with low to moderate rates for IHD and stroke mortality. Relative hazard rates (P < .001) for IHD mortality were 1.010 for men and 1.013 for women and for stroke mortality were 1.018 and 1.021, respectively. The results were similar in men under and over the age of 60. SBP and DBP tended to be more important in younger than older women. For treated DBP in men, a pressure of 55 to 94 mm Hg (median 87) was associated with a low total mortality. The lowest stroke mortality in men was observed for a DBP range of 55 to 83 mm Hg (median 80) but with a tendency for an increase in IHD mortality. For women DBP < 95 mm Hg (range 55 to 94, median 87) also was associated with a low total mortality. IHD mortality in women was not closely related to treated DBP, relative hazard rate = 1.003, [95% confidence index (CI); 0.990,1.017] but the relative hazard rate for men was 1.011, (95% CI; 1.000, 1.022). The relative hazard rates for treated DBP and stroke were high at 1.035 and 1.028 for men and women, respectively (P < .001). IHD mortality increased in the one third of patients with the greatest fall in DBP on treatment, provided they were not initially in the one-third group with highest untreated DBP. CONCLUSIONS: The best overall survival was associated with a treated SBP of < 134 mm Hg in men and < 149 mm Hg in women and a treated DBP of < 95 mm Hg.     

Starch urea-formaldehyde matrix encapsulation. IV. Influence of solubility and physical state of encapsulant on rate and mechanism of release

The influence of the physical state and solubility of the encapsulant on the rate and mechanism of release and swelling of the cross-linked starch-urea formaldehyde (St-UF) matrix has been studied by encapsulating model organic compounds. The release and swelling data have been analyzed in terms of the generalized equation M_t/M_∞ = ktⁿ applicable for swellable controlled-release systems. This matrix system shows and an inverse relationship of release rate with the cross-link ratio for all the encapsulants studied. The solid encapsulants have n values in the range of 0.22–0.41, indicating a Fickian or anomalous mechanism. Further, the release rate increases with solubility of the encapsulant. The liquid encapsulants have n values in the range of 0.5–1.5, indicating Case II transport mechanism. The release rates for liquid encapsulants are lower by one to three orders of magnitude than those for solid encapsulants and are not influenced by encapsulant solubility. This indicates a polymer chain relaxation-controlled mechanism of release for liquid encapsulants. © 1993 John Wiley & Sons, Inc.     

Growth of hexagonal selenium crystals: Observation of new growth morphologies

In this communication, we report the single crystal growth of selenium by the solution method. We have observed a new mesh-like growth pattern in hexagonal selenium for the first time. Crystals having hexagonal morphology are packed together like hay stick bunches.