Prominent Diffraction Peak Research Articles

Temperature effect on the thermal characteristics and drug penetrability of the thermally on-off switching membrane

The aim of this study was to investigate the effects of manufacturing temperature and storage conditions on the thermal properties and drug penetrability of cholesteryl oleyl carbonate (COC)-embedded membranes. The COC-embedded membranes were prepared by a vacuum filtration method at different manufacturing temperatures and then stored at different temperatures. Salbutamol sulphate was used as a model drug across this COC-embedded membrane. It was evident that both manufacturing and storage temperatures significantly affected the characteristics of the membranes. The higher the manufacturing and storage temperatures, especially at 37°C, the greater was the penetration of salbutamol sulphate across the membranes. This phenomenon might due to the smectic-cholesteric phase transition of COC, since crystal fluidity will change in the COC-embedded membranes as a consequence of temperature changes. On the other hand, orientation was also observed to enhance the transport of the molecule at temperatures up the phase transition temperature ( T SC) of COC. X-ray diffraction was used to examine the orientation of COC and it was indicated that the intensity of the two most prominent diffraction peaks of COC disappeared as a result of manufacturing and storage temperature below the phase transition temperature of COC. The effect of temperature fluctuation (10 → 25 → 10 → 25°C) on the penetrability changes of salbutamol sulphate was investigated using the COC-embedded membranes. The penetration of salbutamol sulphate at 10°C was initially negligible. When the temperature was changed from 10 to 25°C, increased penetrability of drug was observed. Furthermore, the penetration of drug was further reduced when the temperature was lowered from 25 to 10°C. The penetration rate of salbutamol sulphate was reversibly regulated in response to a step-wise temperature change between 10 and 25°C. In addition, the higher the manufacturing or storage temperature, the better was the alignment of COC in the membranes, making superior regularity for salbutamol sulphate across the membranes. Whether COC-embedded membranes will be capable of controlling the penetrability of salbutamol sulphate during temperature change depends on the manufacturing temperature and storage conditions. Thermally on-off switching membranes can easily be manufactured by the vacuum filtration method at temperatures above the T SC, and achieve high thermo-responsive efficacy.

X-ray photoelectron diffraction studies of Bi 2Sr 2CaCu 2O 8+ x

A single crystal Bi 2Sr 2CaCu 2O 8+ x ( T 0=84 K has been studied by X-ray photoelectron diffraction (XPD). Nearly full-solid-angle intensity distributions of Bi4f, Sr3d, Ca2p, Cu2p and O 1s emission from a (001)-terminated surface (= c plane) show twofold symmetric patterns with mirror planes along the a and b crystal axes, although the directions of several dominant forward scattering peaks are positioned in a fourfold symmetric way. The results are consistent with the pseudotetragonal structure with a periodically modulated lattice along the b-axis. All diffraction patterns are very different from other, reflecting the different local geometries around different types of emitter atoms. Basically, the positions of the prominent diffraction peaks are well described by single scattering clusters (SSC) calculations with a tetragonal cluster which is terminated by a Bi-O layer. The discrepancy between the experiment and the simulation gives information about the interlayer mixing of atoms.