01 to 0.1.
An abrupt increase in the electrical conductivity and of the carrier concentration with x is observed in the monophasic region (x < x(l)), whereas in the biphasic region (x>x(l)) these values do not vary significantly. These results show that the valence of the doping element plays a crucial role in such properties, similar to degenerated semiconductors. Similarly, the thermopower vertical bar S vertical bar value is correlated with this evolution decreasing as x increases for x < x(l). For the Sn doped samples, the maximum carrier concentration n=10.8×10(20) cm(-3) and electrical conductivity sigma=5×10(3) S cm(-1) are Selleck MK5108 click here both achieved at x=0.06-0.1 (similar to
3-5 at. %) for a thermopower S of -20 mu V/K at room temperature. In comparison, the minimum vertical bar S vertical bar and maxima sigma and n of In2O3 compounds doped with the other cations occur at lower doping levels, e.g., x(l)similar to 0.02 and x(l)similar to 0.015 for Ti and Zr/Nb/Ta doped In2O3, respectively. The relationship between the values of room temperature Hall mobility and carrier concentration shows that numbers and/or effects of multicharged scattering centers of electrons are different depending on the doping element. In2O3 doped with M(IV) elements shows maximum values of mobility close to x=0.006, whereas the doping with M(V) cations induces a decrease in the Hall mobility even for small doping levels. The thermoelectric performances are significantly improved at these low doping levels, with ZT values close to
0.3 at 1000 K in the doped materials against 0.1 mW/mK(2) for the undoped phase.”
“Chitosan has become a focus of major interest in recent years due to its excellent biocompatibility, biodegradability and non-toxicity. Although this material has already been extensively investigated in the design of Cyclopamine in vivo different types of drug delivery systems, it is still little explored for stomach specific drug delivery systems. The objective of the present investigation was to explore the potential of low molecular mass chitosan (LMCH) as carrier for a hydrodynamically balanced system (HBS) for sustained delivery of water soluble drug ciprofloxacin hydrochloride (CP). Various formulations were prepared by physical blending of drug and polymer(s) in varying ratios followed by encapsulation into hard gelatin capsules. All the formulations remained buoyant in 0.1 mol L-1 HCl (pH 1.2) throughout the experiment. Effect of addition of xanthan gum (XG) or ethyl cellulose (EC) on drug release was also investigated. Zero order drug release was obtained from the formulations containing LMCH alone or in combination with XG, and in one instance also with EC.