The aim of the current study was to design an oral sustained release matrix tablet of metformin HCl and to optimize the drug release proˆle using response surface methodology. Tablets were prepared by non-aqueous wet granulation method using HPMC K 15M as matrix forming polymer. A central composite design for 2 factors at 3 levels each was employed to systematically optimize drug release proˆle. HPMC K 15M (X 1 ) and PVP K 30 (X 2 ) were taken as the independent variables. The dependent variables selected were ％ of drug released in 1 hr (rel 1 hr ), ％ of drug released in 8 hrs (rel 8 hrs ) and time to 50％ drug release (t 50％ ). Contour plots were drawn, and optimum formulations were selected by feasibility and grid searches. The formulated tablets followed Higuchi drug release kinetics and diŠusion was the dominant mechanism of drug release, resulting in regulated and complete release within 8 hrs. The polymer (HPMC K 15M) and binder (PVP K 30) had signiˆcant eŠect on the drug release from the tablets ( p＜0.05). Polynomial mathematical models, generated for various response variables using multiple linear regression analysis, were found to be statistically signiˆcant ( p＜0.05). Validation of optimization study, performed using 8 conˆrmatory runs, indicated very high degree of prognostic ability of response surface methodology, with mean percentage error (±S.D.) 0.0437± 0.3285. Besides unraveling the eŠect of the 2 factors on the in vitro drug release, the study helped inˆnding the optimum formulation with sustained drug release.

Synthesis of nano-BaWO4by a modified combustion technique and its suitability for various applications are reported. The structure and phase purity of the sample analyzed by X-ray diffraction, Fourier transform Raman, and infrared spectroscopy show that the sample is phase pure with tetragonal structure. The particle size from the transmission electron microscopy is 22 nm. The basic optical properties and optical constants of the nano BaWO4are studied using UV-visible absorption spectroscopy which showed that the material is a wide band gap semiconductor with band gap of 4.1 eV. The sample shows poor transmittance in ultraviolet region while maximum in visible-near infrared regions. The photoluminescence spectra show intense emission in blue region. The sample is sintered at low temperature of 810°C, without any sintering aid. Surface morphology of the sample is analyzed by scanning electron microscopy. The dielectric constant and loss factor measured at 5 MHz are 9 and1.56×10-3. The temperature coefficient of dielectric constant is −22 ppm/°C. The experimental results obtained in the present work claim the potential use of nano BaWO4as UV filters, transparent films for window layers on solar cells, antireflection coatings, scintillators, detectors, and for LTCC applications.

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a b s t r a c tThe optical properties of nanocrystalline HfO 2 synthesized using a single-step auto-igniting combustion technique is reported. Nanocrystalline hafnium oxide having particle size of the order 10-15 nm were obtained in the present method. The nanopowder was characterized using X-ray diffraction, Fourier transform infrared and Fourier transform Raman spectroscopic studies. All these studies confirm that the phase formation is complete in the combustion synthesis and monoclinic phase [P2 1 /c (14)] of HfO 2 is obtained without the presence of any impurities or additional phases. The powder morphology of the as-prepared sample was studied using transmission electron microscopy and the results were in good agreement with that of the X-ray diffraction studies. The optical constants such as refractive index, extinction coefficient, optical conductivity and the band gap were estimated from UV-vis spectroscopic techniques. The band gap of nanocrystalline HfO 2 was found to be 5.1 eV and the sample shows a broad PL emission at 628 nm. It is concluded that the transitions between intermediate energy levels in the band gap are responsible for the interesting photoluminescent properties of nanocrystalline HfO 2 .

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