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Ghosh O.,Seth Anandram Jaipuria College | Ghosh T.,Maharaja Manindra Chandra College | Chatterjee T.N.,Dinabandhu Andrews College
Solar Physics | Year: 2014

We studied the predictability of the 10.7 cm solar radio flux by using stationary and non-stationary time-series analysis techniques of fractal theory to find the correlation exponent, the spectral exponent, the Hurst exponent, and the fluctuation exponent of the time series. The Hurst exponent was determined, from which the fractal dimension and consequently the predictability was evaluated. The results suggest that stationary methods of analysis yield inconsistent result, that is, amongst the four techniques used, the values of the exponents show great disparity. While two of the techniques, namely the auto-correlation function analysis and the spectral analysis, indicate long-term positive correlation, the other two methods, specifically the Hurst rescaled range-analysis and the fluctuation analysis, clearly exhibit the anti-correlated nature of the time series. The two non-stationary methods, that is, the discrete wavelet transform and the centered moving-average analysis, yielded values of the Hurst exponent that are indicative of positive correlation, of persistent behavior, and also showed that the time series is predictable to a certain extent. © 2013 Springer Science+Business Media Dordrecht.

Bhattacharya U.,Indian Institute of Chemical Technology | Adak S.,Seth Anandram Jaipuria College | Majumder N.S.,Indian Institute of Chemical Technology | Bera B.,Tea Board | Giri A.K.,Indian Institute of Chemical Technology
BMC Complementary and Alternative Medicine | Year: 2014

Background: Darjeeling tea, a most popular variety of black tea, though consumed by the people in different parts of world but its beneficial health effects have not been investigated in details. In this study, the antimutagenic and anticancer effect of Darjeeling tea extract (DTE) has been evaluated. Methods: Antimutagenic activity of the DTE was carried out in two different strains of Salmonella typhimurium by AMES test against a known mutagen benzo[a]pyrene (B[a]P) with S9 activation. Moreover, anticlastogenic property of DTE was also measured by micronuclei formation (MN) against B[a]P with S9 activation in human lymphocytes. The anticancer activity of the same was studied on U937 cell line. Here, Human PBMCs were used as the normal cell control to identify selective anticancer activity of the extract against U937 cells. Results: The results showed significant antimutagenic activity on bacterial strains. A significant decrease in MN was also observed in the DTE treated human lymphocyte cultures pretreated with B[a]P when compared with B[a]P treated cultures alone. The study clearly exhibited anticancer activity of the extract on U937 cell line. Further studies also revealed that apoptosis induction is an important mechanism behind the anticancer effect of DTE. Conclusion: Overall, this study indicates that DTE has significant antimutagenic and anticancer activities on bacterial and mammalian cells respectively. © 2014 Bhattacharya et al.

Ghosh O.,Seth Anandram Jaipuria College | Chatterjee T.N.,Dinabandhu Andrews College
Solar Physics | Year: 2015

We examine the properties of the time-series of daily values of the 10.7-cm solar radio flux and sunspot-number activity indices, and their relative behavior. The analysis and the comparisons are based upon the estimation of the embedded dimension and the use of recurrence plots. The result shows higher-order chaos in 10.7-cm radio flux, and a similar but not identical chaotic nature in the sunspot number indicative of a change in the phase space of the Sun. Both data series show a stochastic behavior only during the rising and peak phase of Solar Cycle 23. © 2015, Springer Science+Business Media Dordrecht.

Chanda A.,Jadavpur University | Akhand A.,Jadavpur University | Manna S.,Jadavpur University | Das S.,Jadavpur University | And 6 more authors.
Wetlands Ecology and Management | Year: 2015

Mangrove species are broadly classified as ‘true mangroves’ and ‘mangrove associates’. We hypothesized that the leaf litter decomposition rates of true mangroves differ significantly from the mangrove associates under the same ecological and bio-climatic conditions. In order to test this hypothesis, the leaf litter decay rates of 24 true mangrove species and 10 mangrove associates along with the concomitant carbon and nitrogen dynamics of the litters were studied in the tropical mangrove forest of Sundarban by means of litter bags. The decomposition was monitored for six consecutive weeks in the pre-monsoon, monsoon and post-monsoon season. All the species in general went through a rapid decay phase in the first 2 weeks, however, the rate substantially decreased in the following 4 weeks. Most of the species studied had significant seasonal variability (p < 0.05) in the decay rate. Species-specific decay was highest throughout the monsoon and least during the post-monsoon season. The mean dry weight composition (i.e. percentage of dry weight of the leaf litters remaining at the end of weekly intervals) of the true mangroves was 10–12 % higher than the mangrove associates throughout the sampling period. The mean decay constants (K in week−1) of the true mangroves were 0.15 ± 0.05, 0.20 ± 0.06 and 0.16 ± 0.05 in the pre-monsoon, monsoon and post-monsoon season respectively. The mangrove associates had significantly higher decay constants in the respective seasons that followed the order 0.23 ± 0.09, 0.25 ± 0.06 and 0.24 ± 0.09. As a consequence, the computed mean half-life period of the true mangrove litters (32 ± 11 days) was much higher than the mangrove associates (23 ± 11 days). This showed that collectively the leaf litters of mangrove associates degraded at a much faster rate than the true mangroves throughout the annual cycle and thus our hypothesis was justified. © 2015 Springer Science+Business Media Dordrecht

Pasquali L.,University of Modena and Reggio Emilia | Pasquali L.,CNR Institute of Materials | Terzi F.,University of Modena and Reggio Emilia | Seeber R.,University of Modena and Reggio Emilia | And 8 more authors.
Langmuir | Year: 2011

We report a study of the self-assembly of 1,4-benzenedimethanethiol monolayers on gold formed in n-hexane solution held at 60 °C for 30 min and in dark conditions. The valence band characteristics, the thickness of the layer, and the orientation of the molecules were analyzed at a synchrotron using high resolution photoelectron spectroscopy and near edge X-ray adsorption spectroscopy. These measurements unambiguously attest the formation of a single layer with molecules arranged in the upright position and presenting a free -SH group at the outer interface. Near edge X-ray absorption fine structure (NEXAFS) measurements suggest that the molecular axis is oriented at 24° with respect to the surface normal. In addition, valence band features could be successfully associated to specific molecular orbital contributions thanks to the comparison with theoretically calculated density of states projected on the different molecular units. © 2011 American Chemical Society.

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