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This present study was aimed at investigating the effect of the crystallinity of cetyl palmitate based solid lipid nanoparticles (SLNs) on the physical properties of γ-oryzanol-loaded SLNs. SLNs consisting of varying ratios of cetyl palmitate and γ-oryzanol were prepared. Their hydrodynamic diameters were in the range 210-280 nm and the zeta potentials were in the range -27 to -35 mV. The size of SLNs increased as the amount of cetyl palmitate decreased whereas no significant change of zeta potentials was found. Atomic force microscopy pictures indicated the presence of disc-like particles. The crystallinity of SLNs, determined by differential scanning calorimetry and powder x-ray diffraction, was directly dependent on the ratio of cetyl palmitate to γ-oryzanol and decreased with decreasing cetyl palmitate content in the lipid matrix. Varying this ratio in the lipid mix resulted in a shift in the melting temperature and enthalpy, although the SLN structure remained unchanged as an orthorhombic lamellar lattice. This has been attributed to a potential inhibition by γ-oryzanol during lipid crystal growth as well as a less ordered structure of the SLNs. The results revealed that the crystallinity of the SLNs was mainly dependent on the solid lipid, and that the crystallinity has an important impact on the physical characteristics of active-loaded SLNs.

This research focuses on understanding the nature of the Fe ions substituted in hydroxyapatite ((HAP) Ca 10-x Fe x( PO 4)6( OH )2-xÿx: x = 0, 0.2 and 0.4) powder synthesized at temperatures between 500°C and 1000°C and their crystallization. The DSC scan indicates a solid state phase transition at about 757°C for the as-prepared powder HAP. The transformation of HAP to β-tricalcium phosphate (β- TCP , β- Ca 3( PO 4)2) is seen when the powder were heated to 750°C. The sizes of the crystallites were determined to be about 46–51 nm, 33–40 nm and 33–59 nm for Fe content of 0, 0.2 and 0.4 mol%, respectively. The ESR parameters for the Fe 3+ ions, g = 4.23 and 8.93 indicated that the ions were subjected to a rhombic ion crystal field within the HAP structures. The g values of ~2.01 indicated that the particles were super-paramagnetic and ferromagnetic iron nanoparticles, having an average size about 0.2–0.5 μm in length.

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COVER PICTUREThe cover picture shows the underlying mechanism and one of the applications of the photorefractive effect, which produces a spatial modulation of the refractive index of a material under nonuniform illumination. As illustrated on the right side, the photorefractive effect begins with light and dark fringes produced by intersecting laser beams, which, in the presence of an applied electric field E 0 , produce charge separation. The mobile charges (primarily holes) move and eventually trap in dark regions, leading to a space ± charge electric field (green). This field produces a refractive index change, that is, a hologram that can diffract light. A key feature of the effect is that it leads to asymmetric energy transfer between the two beams incident on the material. An application of this effect is image amplification, which is demonstrated on the top left side of the picture where the image of the number 5, carried by a weak beam, is amplified in the presence of a strong beam. Among the best photorefractive materials developed thus far are organic, amorphous glasses, the properties of which depend critically on the glass transition temperature (T g ) and photoconductivity (s ph ), as well as polarizability anisotropy (Da) and hyperpolarizability (b) of the molecules. The picture shows the structure of the photoconductive, nonlinear optical chromophore DCDHF-6 that forms a high-performance low-molecular weight photorefractive glass. The detailed properties of several photorefractive glasses containing DCDHF derivatives are described in the article by Ostroverkhova et al. on page 732.ChemPhysChem is a European journal of chemical physics and physical chemistry; its publication was made possible by important contributions from the Socie ¬te ¬ Franc OEaise de Chimie (SFC) and the Gesellschaft Deutscher Chemiker (GDCh), and the Hungarian, Austrian, French Belgian and Flemish Belgian, Czech, Portuguese, and Greek chemical societies are further co-owners. Contributions in ChemPhysChem cover a wide range of topics including atmospheric science, hard and soft condensed matter, femtochemistry, nanotechnology, complex biological systems, single molecule research, clusters, colloids, catalysis, and surface science; namely, research in the overlapping areas between chemistry, physics,

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