Recent Advances in the Application of Characterization Techniques for Studying Physical Stability of Amorphous Pharmaceutical Solids

The amorphous form of a drug usually exhibits higher solubility, faster dissolution rate, and improved oral bioavailability in comparison to its crystalline forms. However, the amorphous forms are thermodynamically unstable and tend to transform into a more stable crystalline form, thus losing their advantages. In order to investigate and suppress the crystallization, it is vital to closely monitor the drug solids during the preparation, storage, and application processes. A list of advanced techniques—including optical microscopy, surface grating decay, solid-state nuclear magnetic resonance, broadband dielectric spectroscopy—have been applied to characterize the physicochemical properties of amorphous pharmaceutical solids, to provide in-depth understanding on the crystallization mechanism. This review briefly summarizes these characterization techniques and highlights their recent advances, so as to provide an up-to-date reference to the available tools in the development of amorphous drugs.

Study of an Integration Platform Based on an Adiabatic Active-Layer Waveguide Connection for InP Photonic Device Integration Mirroring That of Heterogeneous Integration on Silicon

In this work, a photonic device integration platform capable of integration of active-passive InP-based photonic devices without the use of material regrowth is introduced. The platform makes use of an adiabatic active-layer waveguide connection (ALWC) to move an optical beam between active and passive devices. The performance of this platform is analyzed using an example made up of four main sections: (1) a fiber coupling section for enabling vertical beam coupling from optical fiber into the photonic chip using a mode-matched surface grating with apodized duty cycles; (2) a transparent waveguide section for realizing passive photonic devices; (3) an adiabatic mode connection structure for moving the optical beam between passive and active device sections; and (4) an active device section for realizing active photonic devices. It is shown that the coupled surface grating, when added with a bottom gold reflector, can achieve a high chip-to-fiber coupling efficiency (CE) of 88.3% at 1550 nm. The adiabatic active-layer mode connection structure has an optical loss of lower than 1% (CE > 99%). The active device section can achieve an optical gain of 20 dB/mm with the use of only 3 quantum wells. The optimized structural parameters of the entire waveguide module are analyzed and discussed.

The Effect of Temperature Variance with Different Surface Shapes on Efficiency of Silicon Thin Film Solar Cell

In this work, the temperature effects on the PV’s electrical and optical parameters of different surface gratings are studied. A 3D simulation is introduced for studying the PV’s electrical parameters such as short circuit current, open circuit voltage and efficiency at different levels of temperature with and without surface’s gratings. We observed that the efficiency is increased for PV of surface grating by about 4.87% compared to the free grating surface’s PV. The efficiency of the PV efficiency is degraded as we increased the temperature above 300K. The solar cell efficiency of gratings free is aggressively degraded compared to the solar cell that includes gratings by about 4.89% at 360K. The electrical parameters such as the open circuit voltage and short circuit current are enhanced compared to the PV of surface grating free. Also, we observed that the triangle grating geometry of dimensions about 10×10 nm produced a higher efficiency compared to the other PV of other grating geometries of same dimensions.