Ionization states of cosmic rays:Anuradha (IONS) experiment in Spacelab-3

The measurements of the ionization states, composition, energy spectra and spatial distribution of heavy ions of helium to iron of energies 10–100 MeV/amu in the anomalous cosmic rays are of major importance in understanding their origin which is unknown at present.Anuradha (IONS) cosmic ray experiment in Spacelab-3 was designed to determine the above properties in near earth space and this had a highly successful flight and operations aboard the shuttle Challenger at an orbital altitude of 352 km during 29 April to 6 May 1985. The instrument employs solid state nuclear track detectors (CR-39) of high sensitivity and large collecting area of about 800 cm² and determines the arrival time information of particles with active elements. Experimental methods, flight operations and preliminary results are briefly described. Initial results indicate that relatively high fluxes of low energy cosmic ray α-particles, oxygen group and heavier ions were obtained. The flight period corresponded to that of quiet Sun and the level of solar activity was close to solar minimum. It is estimated that about 10,000 events of low energy cosmic ray alpha particles with time annotation are recorded in the detector together with similar number of events of oxygen and heavier ions of low energy cosmic rays. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Unequal connections

Empirical work suggests that social and economic networks are characterized by an unequal distribution of connections across individuals. This paper explores the circumstances under which networks will or will not exhibit inequality. Two specific models of network formation are explored. The first is a playing the field game in which the aggregate payoffs of an individual depend only on the number of his links and the aggregate number of links of the rest of the population. The second is a local spillovers game in which the aggregate payoffs of an individual depend on the distribution of links of all players and the identity of neighbors. For both class of games we develop results on existence and characterize equilibrium networks under different combinations of externalities/spillovers. We also examine conditions under which having more connections implies a higher payoff.     

Mechanical breakdown of trabecular bone: Dependence on microstructure

Experiment on mechanical strength of porous trabecular bone shows power law dependence on the density of the structure. Physical structure and mechanical properties of the trabecular network are modelled here with a fractal lattice network of elastic springs having a strain based fracture criteria. An analysis of the model system supports the power law and shows that lacunarity is an important parameter in differentiating the mechanical strength of trabecular bones of same density.     

Energy levels of λx 2k anharmonic oscillators using the quantum normal form

The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the HamiltonianH=–d ²/dx ²+x ²+x ^2k (k=3, 4,...) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.     

Ring-chain isomerism in conjugated guanylhydrazones: Experimental and theoretical study

Treatment of 1,3-diaryl-propene-2-one with aminoguanidine under acidic conditions for a short reaction period (1?h) delivers - in accordance with a literature report - the corresponding guanylhydrazones. However, when the reaction time was increased to 12?h, formation of the ring annulated product 4,5-dihydro-1H-pyrazole-1-carboximidamide was observed. This is the first case of ring-chain isomerism in conjugated guanylhydrazones. The acyclic conjugated guanylhydrazone and the corresponding annulated product (4,5-dihydro-1H-pyrazole-1-carboximidamide) could be clearly distinguished by means of UV and NMR spectroscopy. The formation of the ring isomer was further confirmed by single crystal XRD analysis. The time-dependent ¹H NMR study indicated the gradual transformation of the open-chain compound into the cyclic one. The mechanistic insights into the formation of these two products were explored using quantum chemical methods which revealed that the ring isomer is thermodynamically more stable than the open-chain isomer by 6–11?kcal/mol and the barrier for cyclization was found to be 31.37?kcal/mol.