Rainfall trends in India and their impact on soil erosion and land management

Under the threat of global warming it is vital to determine the impact that future changes in climate may have on the environment and to what extent any adverse effects can be mitigated. In this research an assessment was carried out on the impact that climate trends may have on soil erosion and contaminant transport in India and examined the potential for top soil management practices to improve or maintain soil quality. Historical rainfall data from 50-135 years and extreme temperature data for 103 years were analysed and long term trends were assessed for various aspects of Indian climates using suitable statistical techniques. Results indicated that intra-region variability for extreme monsoon seasonal rainfall is large and mostly exhibited a negative tendency leading to increasing frequency and magnitude of monsoon rainfall deficit and decreasing frequency and magnitude of monsoon rainfall excess everywhere in India except in the peninsular Indian region. This is further exacerbated by increased and more variable extreme temperatures. Intra-region rainfall variability in India is linked to the pacific Southern Oscillation, where the associations of monsoon drought and El-Niño Southern Oscillation (ENSO) in the regions near to coast are greatest. 50-years high resolution daily gridded rainfall data was analysed to set up certain indices for the extreme daily rainfalls to assess their changes for the six gridded regions of Kerala, the extreme south western state of India where monsoon rainfall initiates every year. This was also done for two study sites, namely Bhoj wetland area of west central India and Sukinda chromite mining site of central north east India. Significant decrease was found in monsoon and spring rainfall extremes and increase in winter and autumn rainfall extremes in Kerala that would affect the tendency of change in seasonal total rainfall as well. Decrease in monsoon rainfall in Kerala also indicate that monsoon rainfall is decreasing in India as a whole, increased occurrence of floods is expected in winter and autumn seasons, together with water scarcity are expected to be felt both in spring and monsoon seasons with a delaying monsoon onset in Kerala. Soil erosion studies were conducted for two northern most gridded regions of Kerala as an extended work of the related MPhil study, and contaminant transport with eroded sediments was looked at for the Bhoj and Sukinda sites using RUSLE2 model software and other suitable numerical methods. It was found that soil erosion depended on a complex interaction of climate, soil properties, topography, and cover management. An assessment on extreme climate patterns for Bhoj and Sukinda showed an increasing tendency of seasonal and annual rainfall extremes and temperatures leading to an increasing pattern of soil erosion at both the sites. However, a certain consensus was difficult to reach because of the complex interaction of climate and soil carbon that is a very important deciding factor for soil erosion potential. Vegetative cover and plant residue was found providing essential soil nutrients, enhancing soil properties and retarding rainfall impact on bare top soil leading to reduction of soil erosion. Therefore, a soil erosion and contaminant transport prevention plan should take care of the top soil such that it is not kept bare especially when rainfall intensity is high in a given year. This work as a whole has highlighted the importance of regional climatological analysis with the large scale spatial averages especially at local decision making level, which is very useful for the broad scenarios such as climatological and ecological risk management

Noise-induced Regime Shifts: A Quantitative Characterization

Diverse complex dynamical systems are known to exhibit abrupt regime shifts at bifurcation points of the saddle-node type. The dynamics of most of these systems, however, have a stochastic component resulting in noise driven regime shifts even if the system is away from the bifurcation points. In this paper, we propose a new quantitative measure, namely, the propensity transition point as an indicator of stochastic regime shifts. The concepts and the methodology are illustrated for the one-variable May model, a well-known model in ecology and the genetic toggle, a two-variable model of a simple genetic circuit. The general applicability and usefulness of the method for the analysis of regime shifts is further demonstrated in the case of the mycobacterial switch to persistence for which experimental data are available.Comment: 10 Pages, 9 figures, revtex4-1, published versio

Search for coronal temperature variation in Seyfert galaxies

While the temperature of the X-ray corona ($\rm{kT_e}$) in active galactic nuclei (AGN) are known for many sources, its variation, if any, is limited to a handful of objects. This is in part due to the requirement of good signal-to-noise X-ray spectra covering a wide range of energies. We present here results on the X-ray spectral analysis of 18 Seyferts, having more than one epoch of observations to look for variation in $\rm{kT_e}$. The data for a total of 52 epochs on these 18 AGN were taken from observations carried out by NuSTAR in the 3$-$79 keV energy band. From phenomenological and physical model fits to the multi-epoch data on these 18 sources from {\it NuSTAR}, we could constrain the cut-off energy ($E_{cut}$) in a large fraction of the sources. Also, from Comptonized model fits, we could obtain $\rm{kT_e}$ for our sample. Of the 18 sources, at the 90 per cent confidence level, evidence for variation in $\rm{kT_e}$ was found for only one source, namely MCG+08-11-011. For this source, between two epochs, separated by about five years, we found $\rm{kT_e}$ to decrease from 57$^{+29}_{-16}$ keV to 30$^{+11}_{-7}$ keV. During the same period, the flux decreased from (12.60 to 14.02) $\times$ 10$^{-11}$ erg cm$^{-2}$ s$^{-1}$ and the optical depth increased from 1.68 to 2.73. We thus found a positive correlation between flux and coronal temperature with a reduction of about 40 per cent in optical depth. Our observations tend to favour the vertically outflowing corona scenario for the observed variation in $\rm{kT_e}$ in MCG+08-11-011.Comment: 17 pages, 7 figuers, accepted for publication in MNRAS-M

Thiosemicarbazone complexes of the platinum metals. A story of variable coordination modes

Salicylaldehyde thiosemicarbazone (H2saltsc) reacts with [M(PPh3)3X2] (M = Ru, Os; X = Cl, Br) to afford complexes of type [M(PPh3)2(Hsaltsc)2], in which the salicylaldehyde thiosemicarbazone ligand is coordinated to the metal as a bidentate N,S-donor forming a four-membered chelate ring. Reaction of benzaldehyde thiosemicarbazones (Hbztsc-R) with [M(PPh3)3X2] also affords complexes of similar type, viz. [M(PPh3)2(bztsc-R)2], in which the benzaldehyde thiosemicarbazones have also been found to coordinate the metal as a bidentate N,S-donor forming a four-membered chelate ring as before. Reaction of the Hbztsc-R ligands has also been carried out with [M(bpy)2X2] (M = Ru, Os; X = Cl, Br), which has afforded complexes of type [M(bpy)2(bztsc-R)]+, which have been isolated as perchlorate salts. Coordination mode of bztsc-R has been found to be the same as before. Structure of the Hbztsc-OMe ligand has been determined and some molecular modelling studies have been carried out determine the reason for the observed mode of coordination. Reaction of acetone thiosemicarbazone (Hactsc) has then been carried out with [M(bpy)2X2] to afford the [M(bpy)2(actsc)]ClO4complexes, in which the actsc ligand coordinates the metal as a bidentate N,S-donorformingafive-membered chelate ring. Reaction of H2saltsc has been carried out with [Ru(bpy)2Cl2] to prepare the [Ru(bpy)2(Hsaltsc)]ClO4 complex, which has then been reacted with one equivalent of nickel perchlorate to afford an octanuclear complex of type [Ru(bpy)2(saltsc-H)4Ni4](ClO4)4

QSPR Modeling of Odor Threshold of Aliphatic Alcohols Using Extended Topochemical Atom (ETA) Indices

The present work establishes a quantitative structure-property relationship (QSPR) between top¬ochemical features and odor threshold (OT) of aliphatic alcohols. A data set of 53 aliphatic alcohols was chosen for the analysis employing different chemometric techniques, among which, genetic function ap¬proximation with spline option (GFA-spline) showed the most acceptable results in terms of internal and external validation metric values. The extended topochemical atom (ETA) indices, developed by the pre¬sent authors’ group, were considered as descriptors for model development. Additionally, selected non-ETA descriptors were also tried for model development. It was observed that the models with ETA indi¬ces significantly surpass the predictive ability of the models developed using other descriptors. The final model suggests that molecular branching and electronic parameters significantly influence the odor poten-cy of the molecules. Additionally, increased lipophilicity and reduced electronegativity increase the odor-ant property. The model thus developed may effectively be used for prediction of odor threshold of any untested aliphatic alcohols. (doi: 10.5562/cca2284