• Volume 8, Issue 1

      January 1977,   pages  1-97

    • Amplitude scintillations of ATS-6 radio beacon signals within the equatorial electrojet region (Ootacamund, dip 4° N)

      R G Rastogi M R Deshpande Hari Om Vats K Davies R N Grubb J E Jones

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      The recordings of the amplitudes of radio beacon signals on 40, 140 and 360 MHz from ATS-6 (at 34° E longitude) recorded at Ootacamund, India (11.43° N, 76.70°E, dip 4°N, elevation angle 41°) have revealed largest occurrence of scintillations for about 60% of cases around 2200 hr during the nighttime, and two secondary peaks (25% of cases) around 0900 hr and 1400 hr during the daytime.

      During the daytime, the scintillation decreases approximately as the inverse of the frequency for higher frequencies while for lower frequencies the law is valid till scintillation index at 40 MHz does not exceed 0.9. The temporal variation of daytime scintillation shows impulsive character, the duration of activity lasts for 1–2 hours at a time.

      During the nighttime, the scintillation decreases inversely with frequency for weak and moderate scintillation activity. The scintillation index at 360 MHz becomes independent of that at 140 MHz when the index at 140 MHz exceeds 0.85. For the set of frequencies 40–140 MHz, on some occasions scintillation index at 40 MHz is seen to be less than that at 140 MHz. The nighttime scintillations are in general stronger and remain so for extended length of time.

      The daytime scintillations are suggested to be due to blanketing or some other non-q type of sporadicE layer. The nighttime scintillations are most probably due to spreadF condition and the abnormal frequency variation of the scintillations may be due to multiple scattering layer during periods of intense spreadF.

    • Spectral features of radiation from Nordström and Kerr-Newman white holes

      Naresh Dadhich

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      Unlike the Schwarzschild white hole, Nordström and Kerr-Newman white holes cannot explode right down from the space time singularityR=0. For example a charged white hole has to commence explosion (i.e., comes into existence) with a radiusR0=Rc(2−Rc/Rb)−1 whereRc is the ‘classical radius’ andRb is the final radius attained when the stationary state is reached. That means charged and rotating black holes also cannot hit the singularityR=0 and perish.

      Here the explosion is decelerated by the presence of charge and rotation and hence the radiation emitted would be not as energetic as in the Schwarzschild case where its energy is infinitely large for emission fromR=0.

    • Short range orientational order in nematic liquid crystals

      N V Madhusudana K L Savithramma S Chandrasekhar

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      The different approximations that have been used in applying Bethe’s cluster model to the nematic-isotropic phase transition are examined. It is shown that the introduction of a higher order term in the mean field potential of an outer molecule of the cluster improves the consistency of the theory considerably. In particular, the importance of satisfying Chang’s relation is emphasized. Calculations are presented of the long and short range order parameters, heat of transition and specific heat for different values ofz, the number of nearest neighbours around any given molecule, for both nonpolar and antiparallel near neighbour correlations. Even the new mean field potential appears to be inadequate forz=3.

    • Electron diffraction data as a constraint in the determination of force field of thallous halide dimers

      D K Sharma U P Verma A N Pandey V Kumar

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      Electron diffraction data have been used as a constraint in the determination of force field for Tl2F2 having planar rhombic structure. The L-F approximation method, recently given by us, has also been applied to evaluate force constants for thallous halide dimers,e.g. T12F2 and T12Cl2. The results have been compared with the available experimental data in order to check the validity of the present work. It is concluded that non-bond experimental mean amplitudeU1...Tl for Tl2F2 is capable of fixing the force field and L-F approximation gives reasonably good force fields for the two thallous halide dimers now under study.

    • The dynamics of tetrahedral XY4 molecules

      P Thirugnanasambandam S Mohan

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      A physical understanding of the nature of the force constants and kinetic constants in molecules leads to a stringent application of the provisions of the group theoretical techniques introduced by Wilson in the study of molecular vibrations. This procedure is applied here to the evaluation of force constants and the mean amplitudes of eighteen tetrahedral XY4 molecules with highly satisfactory results.

    • Search for heavy mass particles in extensive air showers

      S C Tonwar B V Sreekantan R H Vatcha

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      A large multiplate cloud chamber with fast timing scintillators inside is being operated with the extensive air shower array at Ootacamund to further elucidate the time structure of high energy hardons in air showers. The major interest in the present investigation is to understand the nature of the large delay (>20 ns) high energy (>40 GeV) events that appeared as strong cndidates for heavy mass particles in an earlier experiment carried out with a total absorption spectrometer. Two events observed during one year’s operation of the experiment are discussed.

    • Parity violating non-leptonic decays of hyperons and of charmed baryons in SU (8)

      Ramesh C Verma M P Khanna

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      The parity violating non-leptonic decays of hyperons and of charmed baryons are discussed in the framework of SU (8) symmetry. Several relations in addition to the ones obtained earlier by using SU (4) symmetry and20″-dominance, are obtained. The assumption of20″-dominance at the SU (4) level is no longer required for explaining the non-leptonic decays of 1/2+ baryons.

    • Weak neutral currents in the U3(W)-gauge theory of weak and electromagnetic interactions

      L K Pandit

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      A discussion is given of the implications of the recently proposed U3(W)-gauge theory of weak and electromagnetic interactions (Pandit 1976) for some phenomena resulting from its weak neutral currents: (1) neutrino-electron scattering, (2) neutrino-nucleon elastic and inelastic scattering, (3) coherent neutrino-nucleus scattering (4) weak interaction effects ine+e→μ+μ and (5) parity-violation in atomic physics. The theory agrees quite well with the available experimental results on neutrino processes. We find the coherent neutrino-nucleus cross-section for Fe56 to be about 6 times larger than that in the WS-GIM theory giving some hope of accounting for supernova explosion by the resulting neutrino-radiation pressure.

    • Anomalous conversion in the decay of197mHg

      S Bhuloka Reddy D Sudhakara Reddy K L Narasimham B V Thirumala Rao V Lakshminarayana

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      The total andK-shell conversion coefficients of the 165 keV transition in the decay of197mHg are determined from intensity balance considerations and a coincidence technique using a Ge(Li)—NaI (Tl) system respectively. The resultant values areaT=274.8±19.2 andaK=47±12, whil the corresponding theoretical values are 344 and 77 respectively, indicating anomalous conversion. The gamma ray transition probability however, shows a hindrance of only about 6 and cannot be correlated with the present anomalous conversion data. TheK/L ratio of the 130 keV transition, determined using a summing method with a Ge(Li) detector, yielded 0.090±0.012, while the corresponding theoretical value is 0.048, indicating anomalous conversion. The corresponding gamma transition probability shows a hindrance of about 3000, in correlation with anomalous conversion.

    • Beta-gamma-gamma directional correlation in103Rh

      IVS Rathore B P Singh

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      β-γ-γ directional correlation studies for the cascades (i)β-rays ofEmax=0.12 MeV,γ-rays of 557 keV andγ-rays of 53 keV and (ii)β-rays ofEmax=0.21 MeV,γ-rays of 444 keV andγ-rays of 53 keV have been made. The triple correlation functionsW(θ) were obtained to beW(θ)=1+(−0.153±0.031)P2(cosθ)+(0.004±0.035)P4(cosθ) forβ-rays ofEmax 0.12 MeV→557→53 keV cascade andW(θ)=1+(0.163±0.042)P2(cosθ)+(−0.035±0.058)P4(cosθ) forβ rays ofEmax=0.21 MeV→444 keV→53 keV cascade.

      Spins and parities of the 650, 537 and 93 keV levels of103Rh are deduced by triple angular correlation and the internal conversion coefficient studies. Multipolarities of the transitions are also determined.

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