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Planetarium will be inaugurated today
No full textOpen AccessJnanadeepa School has built a Planetarium in collaboration with Raman Research Institute, Bangalore. The Planetarium has been built by the materials used by Nobel Laureat Sir. C.V.Raman
Inversion of moments to retrieve joint probabilities in quantum sequential measurements
No full textOpen Access.A sequence of moments obtained from statistical trials encodes a classical probability distribution. However, it is well known that an incompatible set of moments arises in the quantum scenario, when correlation outcomes associated with measurements on spatially separated entangled states are considered. This feature, viz., the incompatibility of moments with a joint probability distribution, is reflected in the violation of Bell inequalities. Here, we focus on sequential measurements on a single quantum system and investigate if moments and joint probabilities are compatible with each other. By considering sequential measurement of a dichotomic dynamical observable at three different time intervals, we explicitly demonstrate that the moments and the probabilities are inconsistent with each other. Experimental results using a nuclear magnetic resonance system are reported here to corroborate these theoretical observations, viz., the incompatibility of the three-time joint probabilities with those extracted from the moment sequence when sequential measurements on a single-qubit system are considered
New pyrimidine-based photo-switchable bent-core liquid crystals
No full textRestricted Access.The first examples of liquid crystalline pyrimidine-based photo-switchable bent-core monomers incorporating azobenzene as side arms linked with terminal double bonds as polymerizable functional groups are synthesized and characterized. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction analysis reveal that the bent-shaped lower homologue compounds are crystalline in nature whereas higher homologue compounds display the stable enantiotropic B6 phase. They exhibit fast photoisomerization effects in solution and relatively slow photoisomerization effects in liquid crystal cells. In solution both trans–cis and cis–trans occur at around 3 s and 200 s, respectively, whereas in solids they occur at around 10 s to 200 min. These are some of the first examples of azobenzene liquid crystals which exhibit very fast switching properties in solutions
Macrorealism from entropic Leggett-Garg inequalities
No full textOpen AccessWe formulate entropic Leggett-Garg inequalities, which place constraints on the statistical outcomes of temporal correlations of observables. The information theoretic inequalities are satisfied if macrorealism holds. We show that the quantum statistics underlying correlations between time-separated spin component of a quantum rotor mimics that of spin correlations in two spatially separated spin-s particles sharing a state of zero total spin. This brings forth the violation of the entropic Leggett-Garg inequality by a rotating quantum spin-s system in a similar manner as does the entropic Bell inequality [ S. L. Braunstein and C. M. Caves Phys. Rev. Lett. 61 662 (1988)] by a pair of spin-s particles forming a composite spin singlet state
Superlattice structures observed in the extraordinary phase sequence and analyzed by the phenomenological Landau model and the partially molecular model
No full textOpen AccessWe draw several electric-field–temperature (E-T) phase diagrams with electric-field-induced birefringence contours in the nOHFBBB1M7 (n=10) and nOTBBB1M7 (n=11) (C11) mixture system by changing the C11 concentration carefully; some of the mixtures show the unusual extraordinary phase sequence where subphases with the four-, five-, and six-layer superlattice structures emerge above the smectic-C* main phase. We try to understand the results in terms of two complementary models that have so far been proposed: the phenomenological Landau model of phase transitions by Dolganov et al. [ P. V. Dolganov et al. Phys. Rev. E 86 020701 (2012)] and the partially molecular Emelyanenko-Osipov model [ A. V. Emelyanenko and M. A. Osipov Phys. Rev. E 68 051703 (2003)]. The observed E-T phase diagram can be well reproduced by the phenomenological model. An emergence of the subphase with the four-layer superlattice structure above smectic-C* is also understandable in terms of the partially molecular model. We discuss the pros and cons of the two models as well
High-temperature chiral nematic phase in naphthalene and cholesterol derivative liquid crystal: characterisation and dielectric relaxation study
No full textRestricted Access.In this article, we report the synthesis of the naphthalene and cholesterol derivative 2-(cholesterol-n-decanoate)-6-(heptyloxy benzoate) naphthalene (2CD6HBN) liquid crystal (LC) having chiral nematic (N*) mesophase. The synthesised mesophase has been characterised using polarising optical microscopy (POM) and differential scanning calorimetric (DSC) study. The presence of the rigid and less polarisable cores causes a higher N*-Iso transition temperature. The relaxation phenomenon of the present LC sample was analysed by the dielectric relaxation spectroscopic study. The dielectric properties, electrical conductivity and the relaxation time were observed as a function of the temperature. The relaxation time follows the first-order exponential decay–type equation. The properties of the LC sample have also been correlated with the structure of the compound
Emission dynamics of an expanding ultrafast-laser produced Zn plasma under di erent ambient pressures
No full textOpen AccessWe report time and space resolved spectral measurements of neutral Zn emission from an ultrafast laser produced plasma, generated by the irradiation of a Zn target with laser pulses of 100 femtoseconds duration, carried out in a broad ambient pressure range of 0.05 to 100 Torr. The measurement is done for three different axial positions in the expanding plume. The spectra are rich in neutral Zn (Zn I) emissions at 334.5 nm, 468 nm, 472 nm, 481 nm, and 636 nm, respectively, depicting the characteristic triplet structure of Zn. Fast as well as slow peaks are observed in the time of flight data of 481 nm emission, which arise from recombination and atomic contributions, respectively, occurring at different time scales. Average speeds of the fast atomic species do not change appreciably with ambient pressure. The plasma parameters (electron temperature and number density) are evaluated from the measured optical emission spectra. The rates of ionization and recombination can be enhanced by a double-pulse excitation configuration in which optical energy is coupled to the ultrafast plasma through a delayed laser pulse
Triphenylene-based discotic liquid crystals : recent advances Invited article
No full textRestricted Access. Invited articleSince the early work of Chandrasekhar and his co-workers on hexaesters of benzene published in 1977, discotic liquid crystals (DLCs), in particular, triphenylene-based DLC materials have been investigated intensively, especially over the last decade. The first successful commercialisation of triphenylene-based DLCs has been accomplished in Fuji ‘Wide-View’ optical compensation films. DLCs represent a broad well understood class of soft matter which possess the ability to self-organise into highly anisotropic and ordered structures such as columns that function not only as organic anisotropic semiconductors, but also contribute to the development of new smart materials in the field of organic electronics for many device applications such as photovoltaic devices, light-emitting diodes, field-effect transistors, memory elements, and sensors. Over the last 35 years, more than 1000 triphenylene derivatives have been synthesised and investigated starting from structure-properties to structure-device performance relationships. The very first review by Cammidge and Bushby followed by Kumar summarised the chemistry and physical properties of triphenylene-based discotics up to 2003. In this review, progress in the research of triphenylene DLC materials since 2004 is comprehensively outlined
Ultrafast optical nonlinearity in nanostructured selenium allotropes
No full textRestricted Access.In this letter we investigate nonlinear optical properties of amorphous selenium (a-Se) nanoparticles and trigonal selenium (t-Se) nanowires using the open aperture Z-scan, employing 100 fs and 5 ns laser pulses, at 800 nm and 532 nm, respectively. In the former case (ultrafast excitation) optical nonlinearity arises largely from absorption saturation and three-photon absorption, whereas in the latter (short-pulse excitation) it occurs mostly due to excited state absorption. Nonlinearity parameters for both regimes have been numerically evaluated from experimental data. Both allotropes are found to be efficient optical limiters, particularly for short-pulse excitation, with potential applications in laser safety device