53Rd Annual to an Assembly of Topological Defects
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January 1988 No.16 Newsletter of the Indian Academy of Sciences characteristic optical patterns called textures, due 53rd Annual to an assembly of topological defects. Such defect states are also found in supertluids, magnetic spin Meeting systems, crystals etc. but in liquid crystal systems topological defects can be studied with a simple optical technique. At the invitation of the Regional Research The evening lecture that day was given by KG laboratory, Hyderabad, the Academy held its 53rd Ramanathan of the Tata Institute of Fundamental Annual Meeting at RRl from Saturday 7 November Research on "The life and work of Srinivasa to Monday 9 November 1987. Ramanujan". A summary of this lecture is given in The meeting began with the inaugural function this issue. in the RRl Auditorium at 0930 hours on Saturday 7 November. Dr A V Rama Rao, Director, RRL, The first symposium on High temperature welcomed the delegates on behalf of the local superconductivity was held in the RRL auditorium Organizing Committee. He traced the history of in the forenoon of Sunday 8 November, under the the RRL, wnich was established by the chairmanship of Prof. TV Ramakrishnan. Five Government of Hyderabad in 1944 and which scientists, actively engaged in research in this later in 1952, became a part of the CSIR national important area, took part in the symposium. After a chain of laboratories, under the Department of brief introduction by Prof. TV Ramakrishnan, E V Scientific and Industrial Research, with accent on Sampathkumaran of the Tata Institute of research in chemistry and chemical technology. Fundamental Research gave the first talk on an "Overview of high temperature superconductors - Prof. 0 Siddiqi, President, introduced the expe!imental status". High temperature Fellows and Associates present. He then gave his superconducting oxides can be broadly classified Presidential address on the organization of higher into two families. He showed that the temperature of nervous systems and the nature of visual and other these compounds at which they become types of perception. superconducting is a very sensitive function of the This was followed by a Business Meeting of the oxygen content, and the position of the oxygen Fellows. vacancy, in the second family of compounds. There were two short specialized syn:posia A V Narlikar of the National Physical and fourteeen lecture presentations by new Laboratory, New Delhi next spoke on "High Fellows and Associates during the Meeting. temperature superconductivity studies at NPL". The first series of lectures by Fellows and Studies On high temperature Tc superconductors at Associates, under the chairmanship of Prof. 0 NPl are on the substitution effects on Te- the Siddiqi, was held in the afternoon of 7 November mechanism of superconductivity through various in the auditorium of the National Institute of characterization techniques like Hall effect studies, Nutrition. The first talk was by D Mukherjee of the Mossabauer spectroscopy, EPR etc, both quasi Indian Association for the Cultivation of Science, particle and Josephson tunnelling and the nature Calcutta "On the use of size-extensive and size of flux pinning and factors influencing the critical consistent models in quantum chemistry". current density. This was followed by a talk on "Defects in G Baskaran of the Institute of Mathematical liquid crystals" by G 5 Ranganath of the Raman Sciences, Madras spoke next on "The resonating Research Institute, Bangalore. Under a polarising valence bond state and high temperature microscope liquid crystals exhibit beautiful superconductivity" . P G3nguly of the Indian Institute of Science, temperatures below 1 K controls the areal density Bangalore spoke on the "Physico-chemical of electrons, which float about 70 A above the properties of copper oxides and high temperature helium surface. Such an electron system is an superconductivity". He reported on his studies of almost ideal2D system, and has a very smooth magnetic susceptibility, EPR and optical spectra in substrate with no impurities. The electrons the visible and infra-red regions, of some ternary crystallize into a triangular solid below a certain copper oxides. temperature, the only Wigner solid known The last talk in the symposium-was.by G V experimentally. One important advantage of this Subba Rao of the Indian Institute ofTechnology, system is bhat the probe with which the electron Madras on "High te(Tlperature superconductivity layer is studied experimentally exists within the in rare earth-barium-copper-oxygen system of system, viz, by the ripplons (quantized capillary compounds". The high Tc ceramic oxide gravity waves) on the liquid helium surface. If the superconductor is amenable to chemical motion of electrons is restricted in one of the two substitution and hence fine tuning of some of the dimensions, it sh~uld be possible to reduce the superconducting properties, including To is dimensionality of this system from two to one. possible. He reported the synthesis of a large The last talk was by A K Raychaudhuri of the number of well-defined single phase materials. Indian Institute of Science, Bangalore on "New There were five lecture presentations in the dynamical experiments with spin-glasses". He afternoon of 8 November, under the chairmanship presented measurements of dynamic susceptibility of Prof. S Dhawan. N Viswanadham of the Indian and dynamic elastic properties in the audio Institute of Science, Bangalore spoke first on frequency range made on a spin glass. They "Modelling and control of automated establisb. the importance of dynamic elastic manufacturing systems". measurements on spin-glasses as a new tool in the He was followed by J Chandrasekhar, also of the study of the dynamics of spin-freezing. Indian Institute of Science, Bangalore, on "Novel The evening lecture on 8 November was by electronic effects in radicals and radical ions". He Madhav Gadgil on "Bird life of India: In homage to spoke of the use of ab initio and semi-empirical Dr Salim Ali". molecular orbital methods to make several The second symposium on predictions concerning unusual structural and Frontiers in Sciences was held in the forenoon of electronic features associated with radicals and Chemical Monday 9 November. There were five speakers. radical ions. A few representative examples were After a brief introduction by the chairman of the described. session Dr A V Rama Rao, G Mehta of the The next speaker was A K Susheela of the All University of Hyderabad, spoke on "New India Institute of Medical Sciences, New Delhi. She strategies in organic synthesis" . He was followed spoke on the "Emerging concepts in fluorosis by P Balaram of the Indian Institute of Science, research". Dental and skeletal fluorosis is a serious Bangalore, who spoke on "Approaches to the health problem in most states in the country, the chemical synthesis of an artificial protein". main cause being ingestion/inhalation of fluoride in excess, through water, food, toothpaste, drugs The next speaker was K N Ganesh of the and air. In dental fluorosis, the teeth become National Chemical Laboratory, Pune, who spoke on discoloured, with pitting and perforation, while in "Synthesis, spectroscopic and structural studies of skeletal fluorosiS, the clinical manifestations begin short DNA fragments". Protein-nucleic acid with pain in the neck, backbone and hip region interaction is the single most important recognition and culminate in stiff, immobile and painful joints. system, crucial to most biological processes. In his Paralysis is a common occurrence in the late talk he discussed new strategies for large scale stage!>. Valuable information in understanding the synthesis of short DNA fragments. pathogenesis of the disease and the nature of its B Venkataraman of the Tata Institute of affliction has now been collected as a result of the Fundamental Research spoke on "Study of fast studies conducted at the AIIMS. chemical reactions". The time scale of chemical Ravi Mehrotra of the National Physical reactions is known to spread over many orders of Laboratory, New Delhi spoke next on magnitude. A new scale, the pT scale, has been "Experiments on a single layer of electrons". He defined. With the advent of lasers, fast detectors described a novel system, consisting of a single and computers, it has become possible to probe layer of electrons floating above a liquid helium directly into events which take place in time scales surface between two horizontal metal plates of the order or 10-13 seconds. In essence it is now forming a parallel plate capacitor. A positive possible to probe the details of a chemical reaction voltage applied to the plate inside liquid helium at at its most fundamental level. He was followed by Biman Bagchi of the Indian minute of arc, has been used by TIFR for mapping Institute of Science, Bangalore on the "Theory of the emission of several star-forming regions in the chemical reactions in the absence of a barrier". 120-300 fLm wavelength band. In the Carina Recent picosecond and sub-picosecond laser Nebula, for example, where about one third of a spectroscopy experiments have revealed several square degree was mapped by the telescope, more chemically and biologically important reactions in than twenty clumps were detected near the solution, in which the reaction potential surface does boundaries of the ionised hot gas, each having a not present a barrier to the motion along the reaction luminosity more than a thousand times that of the coordinate. He reported recent developments in the Sun. This region, situated about eight thousand theoretical description of activation less processes in light years away, appears to be forming a relatively solution and the available experimental results. larger proportion of heavy stars. Other clusters of The last series of seven lecture presentations was young stars also show a relative deficiency of stars held in the afternoon of 9 November, under the with masses less than a few solar masses.