We studied using dynamic Monte Carlo (DMC) models the size-selective kinetic characteristics of CO monolayer oxidation (CO stripping) on multiscale nanostructured Pt/GC model electrodes comprising nanodisks with diameters of 120 nm and nanoparticles with diameters of 6 nm. We used the DMC models to simulate preadsorbed CO (CO ad ) oxidation peaks and voltammetry responses for the two types of nanostructures and compared them to experiments. Our DMC simulations showed that the different CO stripping voltammetry peaks for the nanodisks and the nanoparticles observed in experiments result from different surface motilities of the CO ad molecules on the catalyst surfaces and from different initial CO ad configurations.
Solid dispersions (SD) were prepared with naringenin and mannitol by the solvent evaporation method with three drying methods (vacuum drying, VD; microwave-vacuum drying, MVD; and spray drying, SPD). The SD was characterized by Differential Scanning Calorimetry (DSC), Powder X-ray Diffractometry (PXRD), Scanning Electronic Microscope (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR).In vitrodissolution of naringenin and physical stability was investigated, and the energy consumption of different processing methods was measured. The results showed that the vitro dissolution rate and extent of naringenin was significantly improved by SD prepared with different drying methods compared to that of the pure drug and physical mixture (PM), and the dissolution rate of SD-SPD and SD-MVD was much higher than the SD-VD. The results of FT-IR showed that naringenin is possibly interacted with mannitol via intermolecular hydrogen bond; The PXRD showed that the crystallinity of the SD prepared with three drying methods was reduced sharply as compared with pure naringenin and PM. There results showed that the physical state of SD-MVD was more stable than SD-SPD and SD-VD that stored in the 40 °C/75% RH chamber in three month. Compared with other drying methods, the MVD method can save time and energy. These results suggest that MVD is feasible to replace the traditional time-consuming and low efficiency drying procedure for preparation of solid dispersions.
Solid dispersions (SD) were prepared with naringenin and polyvinyl pyrrolidone k-30 (PVP k-30) by the solvent evaporation method with three drying methods (microwave-vacuum drying, MVD; and spray drying, SPD; vacuum drying, VD). The physical state was characterized by DSC, PXRD, SEM, and FT-IR. The results showed that the vitro dissolution rate and extent of naringenin was improved significantly by SD as compared with the pure drug and physical mixtures (PM). The results of FT-IR showed that naringenin is possibly interacted with PVP k-30 via intermolecular hydrogen bond, the results of DSC and PXRD showed that all of the SD prepared with three drying methods was completely amorphous. Compared with other drying methods, the MVD method can save time and energy. The physical state of SD prepared with the three drying methods that stored in the 40 °C/75% RH chamber was stable in three month. These results suggest that MVD is feasible to replace the traditional time-consuming and low efficiency drying procedure for preparation of SD.
Microcrystalline Cellulose and Sarcandrae extract powder were used to study the relationships of pharmaceutical properties of powders before and after mixing operation. The theoretical values of the physical quantities of the binary mixture were calculated based on the random mixing theory. The measured values of angle of repose, hygroscopicity of binary mixture were larger than that of theoretical calculations. The effective Kawakita a and b for the MCC had changed by mixing operation. The parameters of blend powder reduced compared with MCC except D-1. The results suggested that the mixing behavior was not a complete random or simple superposition operation for the rough and sticky particles. The mixing process would create novel particles and the physical quantities of novel particles would changes regularly.
Microcrystalline Cellulose andHerba Sarcandraewere used to study the properties and relationship of powders before and after blending. The theoretical values of the physical quantities of the binary mixture were calculated based on the random mixing theory, The measured values of particle size specific surface area, pore volume and angle of repose of binary mixture had larger values than that of theoretical calculations. Whereas, tapped density and bulk density had a smaller value. The results suggested that the mixing behavior was not a complete random, arbitrary or simple superposition of the operation for coarse and sticky particles. The mixing process would create novel particles and physical quantities of novel particles exist regular changes.
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