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Zecca A.,University of Trento | Chiari L.,University of Trento | Chiari L.,Flinders University | Sarkar A.,Bangabasi Morning College | And 2 more authors.
New Journal of Physics

We report our results on the experimental total cross sections (TCSs) for positron scattering from the isoelectronic molecules N2, CO and C2H2. Where possible, for each species, comparison is made between the present results and those from earlier measurements and calculations. The agreement between the present and earlier experimental results, within the overall uncertainties on the data, is typically satisfactory for energies greater than about 8 eV, but is only marginal at lower positron impact energies. While N2, CO and C2H2 possess 14 electrons each, we find significant differences in the magnitudes of their respective TCSs and subtle differences in the energy dependence of these TCSs. These details are discussed in depth in this paper. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source

Neogi S.K.,University of Calcutta | Chattopadhyay S.,University of Calcutta | Chattopadhyay S.,Calcutta Institute of Engineering and Management | Banerjee A.,University of Calcutta | And 3 more authors.
Journal of Physics Condensed Matter

The present work aims to study the effect of ion irradiation on structural and electrical properties and their correlation with the defects in the Zn 1 - xMnxO-type system. Zn1 - xMnxO (x = 0.02, 0.04) samples have been synthesized by the solid-state reaction method and have been irradiated with 50MeV Li3+ ions. The concomitant changes have been probed by x-ray diffraction (XRD), temperature-dependent electrical resistivity and positron annihilation lifetime (PAL) spectroscopy. The XRD result shows a single-phase wurtzite structure for Zn 0.98Mn0.02O, whereas for the Zn0.96Mn 0.04O sample an impurity phase has been found, apart from the usual peaks of ZnO. Ion irradiation removes this impurity peak. The grain size of the samples is found to be uniform. For Zn0.98Mn0.02O, the observed sharp decrease in room temperature resistivity (ρRT) with irradiation is consistent with the lowering of the full width at half maximum of the XRD peaks. However, for Zn0.96Mn0.04O, ρRT decreases for the initial fluence but increases for a further increase in fluence. All the irradiated Zn0.98Mn0.02O samples show a metal-semiconductor transition in temperature-dependent resistivity measurements at low temperature. But all the irradiated Zn 0.96Mn0.04O samples show a semiconducting nature in the whole range of temperatures. Results of room temperature resistivity, XRD and PAL measurements are consistent with each other. © 2011 IOP Publishing Ltd. Source

Zecca A.,University of Trento | Chiari L.,University of Trento | Chiari L.,Flinders University | Trainotti E.,University of Trento | And 7 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics

We report on measurements of total cross sections for positron scattering from the fundamental organic molecule methane (CH 4). The energy range of these measurements was 0.1-50 eV, whereas the energy resolution was ∼100 meV when our Ni moderator was used and ∼260 meV when the W moderator was employed. To assist us in interpreting these data, Schwinger multichannel calculations were performed at both static and static plus polarization levels of approximation for elastic positron scattering from 0.001 to 10 eV. These calculations are found to be in quite good qualitative agreement with our measured data, and they clearly educe the crucial role played by the target polarization in the low energy positron-CH 4 scattering dynamics. © 2012 American Physical Society. Source

Sinha Babu S.,Bangabasi Morning College | Datta S.K.,University of Burdwan
Environment, Development and Sustainability

The link between economic, social, and environmental indicators is often complex and requires a detailed analysis for its understanding. The economy is dependent on the society and the environment, while the very existence of human race and society depends on and within the environment. Thus, these three entities are intricately interconnected, and it is therefore important to understand that any individual group of economic, social or environmental indicators must always be interpreted in connection with the other two groups, since only in this way, an integrated view of the functioning of an economy can be ensured. For the system to be sustainable, the different forces that act on this particular system of interaction must be in balance. Hence, a detailed analysis of selected economic, social, and environmental aspects of development and their linkages is a matter of utmost significance. The objective of this study is to identify an endogenously integrated relationship where economic factor such as gross domestic product per capita influences both qualitative and quantitative factors in social and environmental dimensions and vice versa and to focus on possible correlation between a set of ambient environmental aspects and a set of socio-economic dimensions that influence human well-being and sustainability. The results of the empirical analysis emphasise the fact that there exists bi-directional relationship between different developmental and environmental aspects in the developing countries. The study further argues that without consideration of depreciation/depletion charges for the environmental capital, this relation will not reflect the true interdependence. © 2014, Springer Science+Business Media Dordrecht. Source

Sarkar A.,Bangabasi Morning College | Chakrabarti M.,University of Calcutta | Ray S.K.,Indian Institute of Technology Kharagpur | Bhowmick D.,Variable Energy Cyclotron Center | Sanyal D.,Variable Energy Cyclotron Center
Journal of Physics Condensed Matter

The room temperature positron annihilation lifetime for single crystalline ZnO has been measured as 164 ± 1ps. The single component lifetime value is very close to but higher than the theoretically predicted value of ∼ 154 ps. Photoluminescence study (at 10K) indicates the presence of hydrogen and other defects, mainly acceptor related, in the crystal. Defects related to a lower open volume than zinc vacancies, presumably a complex with two hydrogen atoms, are the major trapping sites in the sample. The bulk positron lifetime in ZnO is expected to be a little less than 164ps. © 2011 IOP Publishing Ltd. Source

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