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- SourceAvailable from: M. L. N. Madhu Mohan[Show abstract] [Hide abstract]
ABSTRACT: A novel series of linear supramolecular hydrogen bonded liquid crystals (SMHBLC) has been investigated. Complimentary hydrogen bonds are formed between various alkyloxy benzoic acids. Formation of hydrogen bond is confirmed by FTIR spectroscopic studies. These homologs exhibit rich phase variance as evinced by various textures by polarizing optical microscopic (POM) studies. DSC studies revealed the transition temperatures and corresponding enthalpy values which are elucidated from the DSC thermograms. Phase diagram has been constructed through POM and DSC data. An interesting finding is the observation of a new smectic ordering labeled as smectic X. This phase has been characterized by various techniques which includes XRD. Optical tilt angle in smectic C and smectic X phases of various homologs has been measured and fitted to a power law. Dielectric relaxations have been carried out in nematic and smectic C phases of different mesogens and their activation energies are calculated. An interesting observation is the optical shuttering action of the mesogens in the nematic phase. In addition to the above phenomenon the light filtering action of these mesogens in the nematic phase has been studied.Journal of Molecular Liquids 06/2013; 182:79–90. DOI:10.1016/j.molliq.2013.03.014
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ABSTRACT: In this paper, Barium Strontium Tungstate (Ba1−xSrx)WO4 crystals with (x = 0; 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0) were prepared by standard wet milling ceramic preparation method. These crystals were structurally characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman) and Fourier transform infrared (FT-IR) spectroscopic techniques. The shape, growth and average crystal size distribution of these crystals were investigated by a scanning electron microscope (SEM). Their optical properties were investigated by ultraviolet visible (UV–vis) absorption and photoluminescence (PL) measurements. XRD patterns, Rietveld refinements data, FT-Raman and FT-IR spectroscopies indicate that all the crystals present a scheelite-type tetragonal structure without deleterious phases. FT-Raman spectra exhibited 6 Raman active modes in range from 100 to 1000 cm−1, while the FT-IR spectra presented 2 infrared active modes in range from 500 to 1000 cm−1. SEM micrographs showed well sintered BaWO4 grains, while the substitution of Sr induced modifications in the shape and reduction in the grain size. UV–vis absorption measurements evidenced an increase in the values of the optical band gap (from 4.36 to 4.53 eV) with the increase of Sr into BaWO4 lattice. Dielectric constant, temperature coefficient of resonant frequency (τf), quality factors were measured with Hakki–Coleman technique. The value of τf found −43.68 ppm/°C for BaWO4 which increased to −21.40 ppm/°C for the SrWO4.Ceramics International 06/2013; 20(8):40–45. DOI:10.1016/j.solidstatesciences.2013.03.002
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ABSTRACT: Designing an ophthalmic drug delivery system is one of the most difficult challenges for the researchers. The anatomy and physiology of eye create barriers like blinking which leads to the poor retention time and penetration of drug moiety. Some conventional ocular drug delivery systems show shortcomings such as enhanced pre-corneal elimination, high variability in efficiency, and blurred vision. To overcome these problems, several novel drug delivery systems such as liposomes, nanoparticles, hydrogels, and in situ gels have been developed. In situ-forming hydrogels are liquid upon instillation and undergo phase transition in the ocular cul-de-sac to form viscoelastic gel and this provides a response to environmental changes. In the past few years, an impressive number of novel temperature, pH, and ion-induced in situ-forming systems have been reported for sustain ophthalmic drug delivery. Each system has its own advantages and drawbacks. Thus, a combination of two drug delivery systems, i.e., nanoparticles and in situ gel, has been developed which is known as nanoparticle laden in situ gel. This review describes every aspects of this novel formulation, which present the readers an exhaustive detail and might contribute to research and development.03/2013; 4(1):9-17. DOI:10.4103/2231-4040.107495
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