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Investigations on photo and electrically switchable asymmetric bent-core liquid crystals
No full textRestricted Access.New series of bent-core liquid crystals (8a–8d) synthesized and their photo and electrical switching properties were investigated. The homologous series of liquid crystals was constructed with five-ring system using structurally non-symmetrical rod-like mesogens connected with 1, 3-phenylene unit. The synthesized precursor and bent-core liquid crystals were characterized by FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The mesophase characterization of the asymmetric bent-core liquid crystals was carried out using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction studies. The significance of tail length (alkyl chain) and nature of mesogen was explored; shorter alkyl chains bent-core compounds exhibited non-switchable rectangular columnar B1 phase. Whereas longer alkyl chain induces switchable lamellar B2 phase, which was further confirmed by electro-optical methods. This lamellar B2 phase exhibits antiferroelectric–anticlinic organization (SmCAPA) of the molecules in the layers. The photo-switching properties of bent-core azo molecules were investigated using UV–Vis spectroscopy, the trans to cis photoisomerization was observed at 30 s, whereas reverse processes take place in 40 s in chloroform
4'-Cyanobiphenyl-4-yl 7-diethylamino-2-oxo-2H-chromene-3-carboxylate
No full textOpen Access.In the title compound, C27H22N2O4, the dihedral angles between the central benzene ring and the cyanobenzene ring and the 2H-coumarin ring system (r.m.s. deviation = 0.014 Å) are 22.95 (11) and 75.59 (8)°, respectively. Both terminal C atoms of the pendant diethylamino group lie to the same side of the coumarin ring system [deviations = 1.366 (2) and 1.266 (2) Å]. In the crystal, molecules are linked by C-H...O and C-H...N hydrogen bonds and a C-H...[pi] interaction, generating a three-dimensional network
Measurement of collisions between rubidium atoms and optically dark rubidium ions in trapped mixtures
No full textOpen AccessWe measure the collision-rate coefficient between laser-cooled rubidium (Rb) atoms in a magneto-optical trap (MOT) and optically dark Rb+ ions in an overlapping Paul trap. In such a mixture, the ions are created from the MOT atoms and allowed to accumulate in the ion trap, which results in a significant reduction in the number of steady-state MOT atoms. A theoretical rate-equation model is developed to describe the evolution of the MOT atom number due to ionization and ion-atom collisions, and we derive an expression for the ion-atom collision-rate coefficient. The loss of MOT atoms is studied systematically by sequentially switching on the various mechanisms in the experiment. Combining the measurements with the model allows the direct determination of the ion-atom collision-rate coefficient. Finally, the scope of the experimental technique developed here is discussed
Simultaneous optical and photoacoustic measurement of nonlinear absorption
No full textOpen AccessA measurement technique to perform optical Z-scan and photoacoustic Z-scan simultaneously called OPAZ-scan is demonstrated. It is found that the simultaneous measurement of the optical and photoacoustic Z-scan signals provides substantially better insight into the mechanism of optical nonlinearity. The system is able to identify mixed nonlinear processes within a mixture of nonlinear scattering species and nonlinear absorbers
Methods to reduce power consumption of liquid crystal displays
No full textRestricted Access. Book Chapter from Progress In Liquid Crystal science and Technology Edited by Hoi-Sing Kwok et al 2013
RRI takes first step to view birth of universe
No full textOpen AccessThe RRI, in partnership with US Universities, Harvard and MIT, and the Universities of Australia and New Zealand successfully built and commissioned the MWA, a radio telescope that is a precursor to the international Square Kilometre Array (SKA), a next generation new-technology radio telescope being built across Australia and South Africa
Raman spectroscopy for broader medical research
No full textOpen AccessScientists have modulated Indian Nobel laureate C V Raman’s spectroscopy signals, opening the door to wider biomedical and clinical applications such as real-time assessment of tissues during surger
