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Galactic PeV Neutrinos
No full textRestricted Access. An open-access version is available at arXiv.org (one of the alternative locations)The IceCube experiment has detected two neutrinos with energies between 1 and 10 PeV. They might have originated from Galactic or extragalactic sources of cosmic rays. In the present work we consider hadronic interactions of the diffuse very high energy cosmic rays with the interstellar matter within our Galaxy to explain the PeV neutrino events detected in IceCube. We also expect PeV gamma ray events along with the PeV neutrino events if the observed PeV neutrinos were produced within our Galaxy in hadronic interactions. PeV gamma rays are unlikely to reach us from sources outside our Galaxy due to pair production with cosmic background radiation fields. We suggest that in future with simultaneous detections of PeV gamma rays and neutrinos it would be possible to distinguish between Galactic and extragalactic origins of very high energy neutrinos
Azo functionalised achiral bent-core liquid crystals: observation of photo-induced effects in B7 and B2 mesophases
No full textRestricted Access.Three structural variants of azo substituted achiral bent-core compounds are reported. Here, the effect of symmetrical and non-symmetrical arms at 1,3-positions of the central phenyl ring on the mesogenic properties of the resulting bent-core azo compounds is studied. The structures of all the compounds synthesised are confirmed by the organic spectroscopic methods. The liquid crystalline properties are investigated using polarising optical microscopy, differential scanning calorimetry and X-ray diffraction studies. It was found that the non-symmetrical molecules are more conducive to mesomorphism than the symmetrical ones. We observed B1 (Colr), B2 (SmCAPA) and B7 mesophases in these compounds. The B7 mesophase was found to have a modulated layer structure. Interestingly, a reversible field-induced transition from the B7-like structure to the racemic SmCAPF was also observed. We also report the photo-induced studies in the B7 mesophase and make a comparison of these results with those obtained in a B2 mesophase. From our studies, we observed that these effects are more profound in the case of B7 mesophase when compared to the B2 mesophase in such systems
New perylene-based non-conventional discotic liquid crystals
No full textOpen Access.The synthesis, optical properties and thermal behaviour of three novel non-conventional 3,4,9,10-tetrasubstituted perylene-based discotic oligomers are reported for the first time consisting of a perylene core attached to which are four 4-cyanobiphenyl, triphenylene and cholesteryl units via flexible alkyl spacers. All the oligomers self-assemble into a mesophase and exhibit excellent fluorescence emission properties making them suitable for various opto-electronic applications
H-Index of Astrophysicists at Raman Research Institute: Performance of different calculators.
No full textRestricted AccessH-index, a single number proposed by J. E. Hirsch in 2005 has gained popularity as an
index number to measure the research performance of individuals, institutions, universities, etc. There are many calculators to derive the h-index number, such as Google Scholar, Web of
Science, Scopus, etc. However, h-index can be calculated manually, provided we have access to a complete list of publications of a scientist and the number of citations received by them. It is
observed that h-index for a given scientist at any given point of time differs from one calculator to the other. Here is an attempt to calculate the H-index of scientists of the Astronomy and Astrophysics Group at Raman Research Institute using Google Scholar Free calculator, Web of
Science Paid calculator and The SAO/NASA Astrophysics Data System manual calculation and comparison of the results. Application of this h-index phenomenon to the research output of RRI scientists in a group is done while keeping in mind Hirsch’s systematic investigation to predict the position of a scientist using h-index in physics.
It is believed that the higher the academic age of a scientist, the higher will be the h-index. An attempt is made to find whether this assumption is true with respect to the sample studied by including the superannuated scientists from Astronomy and Astrophysics Group at Raman Research Institute under the purview of this study
Single step synthesis and optical limiting properties of Ni-Ag and Fe-Ag bimetallic nanoparticles
No full textRestricted Access.Magnetic nanoparticles have several applications in biology and medicine, and recently, their use for optical applications is gaining substantial attention. In this paper we report a single step solution based synthesis of Ni–Ag and Fe–Ag bimetallic nanoparticles using hydrazine hydrate as the reducing agent. Structural, plasmonic, and nonlinear optical properties of the prepared nanoparticles are investigated using X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV–Vis absorption spectroscopy and Z-scan. UV–Vis absorption studies reveal surface plasmon resonance (SPR) absorption at 400 nm which exhibits a small red shift with particle size due to scattering. XRD, EDS, HRTEM and SPR absorption confirm the presence of Ni–Ag and Fe–Ag nanoparticles. Nonlinear optical studies are carried out using the open aperture Z-scan technique employing 5 ns as well as 100 fs laser pulses. The nonlinearity is found to have contributions from absorption saturation, two-photon absorption, excited state absorption and induced thermal scattering of light. The effective nonlinear absorption in Ni–Ag and Fe–Ag nanoparticles is found to be higher than that of pristine Ag nanoparticles. The potential of these materials for optical limiting and photonic applications is discussed
Impact of consortia on usage pattern of information resources: A study at Raman research institute
No full textRestricted AccessThe concept of consortia has been in vogue in library profession for quite some time. It has taken firm root
in librarianship due to the evolution and revolution of “Digital Information”. Shrinking budget and the rate
of growth of publications in digital format has encouraged librarians to view consortia as their friend. CSIRDST
consortium re-designated as National Knowledge Resource Consortia (NKRC) had its beginning in
2009. Since then, Raman Research Institute is an active partner and a stake holder of this consortium.
The benefits of consortia can best be assessed either by usage statistics or by analyzing the cited references
of the research papers published by the scientists of an institute. In this study, the later method has been
adopted to study the impact of consortium at Raman Research Institute. Cited references of the papers
published prior to consortia are compared against the papers published three years after joining the consortia.
It is envisaged that this study will throw light on the usage pattern of information resources with respect to
subscribed content and shared content through consortia
An octave bandwidth frequency independent dipole antenna
No full textRestricted AccessPrecision measurements of the spectrum of the cosmic radio background require frequency independent antennas of small electrical dimensions. We describe the design of a wide-band fat-dipole antenna with a sinusoidal profile having a frequency independent performance over the octave band 87.5 to 175 MHz. The input return loss exceeds 15 dB and the radiation power pattern is frequency invariant and close to cosine square over the octave bandwidth. The structure has been optimized using electromagnetic modeling, and the design has been validated by constructing a prototype
Controlling the thermodynamic stability of intermediate phases in a cationic-amphiphile-water system with strongly binding counterions.
No full textOpen Access.We have studied the influence of two structurally isomeric organic salts, namely, 2-sodium-3-hydroxy naphthoate (SHN) and 1-sodium-2-hydroxy naphthoate (SHN1), on the phase behavior of concentrated aqueous solutions of the cationic surfactant cetylpyridinium chloride (CPC). Partial phase diagrams of the two systems have been constructed using polarizing optical microscopy and x-ray diffraction techniques. A variety of intermediate phases is seen in both systems for a range of salt concentrations. The CPC-SHN-water system exhibits the rhombohedral and tetragonal mesh phases in addition to the random mesh phase, whereas the CPC-SHN1-water system shows only the tetragonal and random mesh phases. The CPC-SHN-water system also exhibits two nematic phases consisting of cylindrical and disk-like micelles at relatively low and high salt concentrations, respectively. These results show that the concentration of the strongly bound counterion provided by the organic salt can be used as a control parameter to tune the stability of different intermediate phases in amphiphile-water systems
Hydrodynamics of soft active matter
No full textOpen AccessThis review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized
Comparison of post-Newtonian templates for extreme mass ratio inspirals
No full textOpen AccessExtreme mass ratio inspirals (EMRIs), the inspirals of compact objects into supermassive black holes, are important gravitational wave sources for the Laser Interferometer Space Antenna (LISA). We study the performance of various post-Newtonian (PN) template families relative to the waveforms that are high-precision numerical solutions of the Teukolsky equation in the context of EMRI parameter estimation with LISA. Expressions for the time-domain waveforms TaylorT1, TaylorT2, TaylorT3, TaylorT4 and TaylorEt are derived up to 22 PN order, i.e. O(v44) (v is the characteristic velocity of the binary) beyond the Newtonian term, for a test particle in a circular orbit around a Schwarzschild black hole. The phase difference between the above 22 PN waveform families and numerical waveforms are evaluated during two-year inspirals for two prototypical EMRI systems with mass ratios 10-4 and 10-5. We find that the dephases (in radians) for TaylorT1 and TaylorT2, respectively, are about 10-9 (10-2) and 10-9 (10-3) for mass ratio 10-4 (10-5). This suggests that using 22 PN TaylorT1 or TaylorT2 waveforms for parameter estimation of EMRIs will result in accuracies comparable to numerical waveform accuracy for most of the LISA parameter space. On the other hand, from the dephase results, we find that TaylorT3, TaylorT4 and TaylorEt fare relatively poorly as one approaches the last stable orbit. This implies that, as for comparable mass binaries using the 3.5 PN phase of waveforms, the 22 PN TaylorT3 and TaylorEt approximants do not perform well enough for the EMRIs. The reason underlying the poor performance of TaylorT3, TaylorT4 and TaylorEt relative to TaylorT1 and TaylorT2 is finally examined