We investigated the electrical and optical properties of InGaAs self-assembled quantum dots grown using the atomic layer epitaxy (ALE) technique. Dots–in–a–well structures were grown by alternately supplying InAs and GaAs sources on an InGaAs layer and covering with another InGaAs layer. Three samples produced with different numbers of cycles of alternate InAs/GaAs supply were characterized by capacitance-voltage and photoluminescence (PL) measurements. For the ten cycle dots–in–a–well structure, a strong zero-dimensional electron confinement was observed even at room temperature. On the other hand, for the five-cycle structure, the PL results indicate that the InGaAs quantum well structure coexists unstably with premature quantum dots. By comparing the results for samples with different numbers of cycles, we suggest that an ALE dots–in–a–well structure can be formed by the aggregation of In and Ga atoms incorporated into the InGaAs quantum well layer when the number of cycles exceeds the critical number of seven cycles.

The purpose of this study was to investigate the effect of bile salts on gastrointestinal absorption and the plasma second peak phenomenon of roxithromycin in rats. The pharmacokinetic parameters of roxithromycin were calculated after single oral administration at a dose of 20 mg/kg in sham-operated (control), bile duct cannulated (BDC) and bile salt co-administered bile duct cannulated (BSBDC) rats. In BDC rats, the total area under the plasma concentration-time curve from time zero to time infinity (AUC0-∞) and the peak plasma concentration (Cmax) were significantly smaller (0.572-fold) and lower (0.412-fold), respectively, than those in the control rats. These values were recovered by co-administration of bile salt (0.831- and 0.828-fold for AUC0-∞ and Cmax compared with the control, respectively). Thus, the decreased absorption of roxithromycin in BDC rats could be due to a depletion of bile. The solubility of roxithromycin was 3.09-fold increased at 30 mm of sodium taurocholate. The oral dosage regimen of roxithromycin could be changed in patients with bile deficiency or when the drug is administered to individuals on a high-fat diet, if the present rat data can be extrapolated to humans.