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A 151.5 MHz southern sky survey covering the RA range 0h < RA < 6h and the declination range −70 DEC −10
No full text19th Conference on liquid crystals
No full textRestricted Access. Paper presented at XIX CONFERENCE ON Liquid crystals
Chemistry, Physics and Applications
18–23 September 2011, Międzyzdroje, Polan
Phase behavior of two-component lipid membranes: Theory and experiments
No full textOpen AccessThe structure of the ripple phase of phospholipid membranes remains poorly understood in spite of a large number of theoretical studies, with many experimentally established structural features of this phase unaccounted for. In this article we present a phenomenological theory of phase transitions in single- and two-component achiral lipid membranes in terms of two coupled order parameters: a scalar order parameter describing lipid chain melting, and a vector order parameter describing the tilt of the hydrocarbon chains below the chain-melting transition. This model reproduces all the salient structural features of the ripple phase, providing a unified description of the phase diagram and microstructure. In addition, it predicts a variant of this phase that does not seem to have been experimentally observed. Using this model we have calculated generic phase diagrams of two-component membranes. We have also determined the phase diagram of a two-component lipid membrane from x-ray diffraction studies on aligned multilayers. This phase diagram is found to be in good agreement with that calculated from the model
Functional discotic liquid crystals
No full textRestricted Access.This review article provides a birds-eye view on discotic liquid crystals and their potential applications. Design principles, synthesis, modification of physical properties and potential applications of some common discotic liquid crystals have been briefly summarized
Understanding the fanaroff-riley radio galaxy classification
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)A simple, yet profoundly far-reaching classification scheme based on extended radiomorphologies of radio galaxies, the Fanaroff-Riley (FR) classification has been a cornerstone in our understanding of radio galaxies. Over the decades since the recognition that there are two basic types of radio galaxy morphologies, there have been several findings in different wavebands that have reported properties on different scales. Although it is realized that there may be intrinsic as well as external causes, an overarching view of how we may understand the two morphological types is missing. With the radio-power-absolute-magnitude relation (the Owen-Ledlow diagram) as a backdrop, we review and develop an understanding of the two radio galaxy types in light of what is known about them. We have for the first time included the dust properties of the two FR classes together with the relative orientations of dust, host major axis, and the radio axis to present a qualitative framework within which to understand the conditions under which they form. We discuss how the host elliptical and its history can explain the distribution of radio galaxies in the Owen-Ledlow diagram. The mass of the host elliptical galaxy is a crucial player in deciding what type of a radio galaxy it can host in what conditions. Benign conditions, characterized by natural evolutionary processes, most easily give rise to FR-I-type sources in ellipticals of all mass regimes, whereas with FR-IIs we reason that it is hard to form them without mergers. In undisturbed conditions elliptical galaxies appear to acquire stable states where the black hole axis settles along the host minor axis. With the steady conditions and the continuous supply of ambient gas, the FR-Is in principle may be powered for a long time. Aided by mergers and interactions, low-mass ellipticals more easily form FR-II-type sources than more massive hosts. LEG FR-IIs may include dying as well as restarted FR-II radio galaxies
Survey of radio recombination lines using the Ooty radio telescope at 328 MHz in the inner galaxy
No full textRestricted Access An open-access version is available at arXiv.org (one of the alternative locations)A survey of radio recombination lines in the Galactic plane with longitude -32° < l < +80° and latitude b < ±3° using Ooty Radio Telescope (ORT) at 328 MHz is reported. ORT observations were made using a New Digital Backend (NDB) recently added to the telescope. With the NDB ORT had a beam of 2fdg3 × 2fdg2 sec(δ) and a passband of ~1 MHz in the spectral line mode. The above-mentioned Galactic region was divided into ~2° × 2° patches with the ORT beam pointed to the center. The ORT observations form a study of the distribution of extended low-density warm-ionized medium (ELDWIM) in the inner Galaxy using H271α RLs. By obtaining kinematical distances using V LSR of the H271α RLs, the distribution of ELDWIM clouds within the inner Galaxy has been deduced for the region given above
Ehrenfest’s theorem and nonclassical states of light: 2. Dynamics of nonclassical states of light
No full textOpen AccessThe states of radiation of a single frequency and polarization propagating in free space are very conveniently represented by those of a quantum mechanical simple harmonic oscillator. This fact is exploited, together with the Ehrenfest theorem, to map the time evolution of the radiation to the dynamics of the oscillator. This enables a graphical comparison of the behaviour of classical and nonclassical states of radiation
Synthesis, characterization, and nonlinear optical properties of donor-acceptor conjugated polymers and polymer/Ag nanocomposites
No full textRestricted Access.Two new donor–acceptor (D–A) conjugated polymers P1 and P2 containing 3,4-didodecyloxythiophene and 1,3,4-oxadiazole units are synthesized via Wittig reaction methodology. Cyclic voltammetry studies reveal that the polymers are both p and n dopable, and possess low-lying LUMO energy levels (−3.34 eV for P1 and −3.46 eV for P2) and high-lying HOMO energy levels (−5.34 eV for P1 and −5.27 eV for P2). The optical band gap of the polymers is in the range of 2.25–2.29 eV, calculated from the onset absorption edge. The polymers emit orange to yellow light in the film state when irradiated with a UV light. The synthesized polymers are used to prepare polymer nanocomposites with different wt% of silver nanoparticles. The polymer nanocomposites are characterized by UV–Vis absorption spectroscopy, field emission scanning electron microscopy, and thermogravimetric analysis. Both polymers and polymer/Ag nanocomposites show good thermal stability with onset decomposition temperature around 300 °C under nitrogen atmosphere. The nonlinear optical properties of polymers and polymer/Ag nanocomposites are measured by Z-scan technique. Both polymers and polymer nanocomposites show a good optical limiting behavior. Nearly five times enhancement in the nonlinear optical properties is observed for polymer/Ag nanocomposites. The value of effective two-photon absorption coefficient (β) is in the order of 10−10–10−11 m/W. These results indicate that the synthesized polymers (P1 and P2) and their Ag nanocomposites are expected to be good candidates for application in photonic devices
Density and temperature effects on Compton scattering in plasmas
No full textopen Access.We study the effect of the density and temperature on Compton scattering in a plasma, with particular emphasis on the quality of the scattered electron beam. We find that the longitudinal mode in the plasma plays a dominant role in producing collimated and mono-energetic electron spectrum. The beam profile is, however, sensitive to the plasma parameters such as its density and temperature. We make a careful study of this sensitivity and distinguish regions in the parameter space in which the quality of the beam profile is good from the regions in which it is poor. These findings are potentially useful in understanding the physics of laser plasma accelerators