Adsorption Kinetic Modeling of Safranin onto Rice Husk Biomatrix Using Pseudo‐first‐ and Pseudo‐second‐order Kinetic Models: Comparison of Linear and Non‐linear Methods

Batch kinetic studies were carried out for the removal of safranin from aqueous solution using a biomatrix prepared from rice husk. The adsorption kinetic data were modeled using the pseudo‐first‐order and pseudo‐second‐order kinetic equations. The linear and non‐linear forms of these two widely used kinetic models were compared in this study. In order to determine the best‐fitting equation, the coefficient of determination (r²), the sum of the squares of the errors (SSE), sum of the absolute errors (SAE), average relative error (ARE), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), and the Chi‐squared test (χ²) were used as error analysis methods. Results showed that the non‐linear forms of pseudo‐first‐order and pseudo‐second‐order models were more suitable than the linear forms for fitting the experimental data. Non‐linear method is thus more appropriate for estimating the kinetic parameters and should primarily be used to describe adsorption kinetics.     

Influence of Eurasian snow on Indian summer monsoon in NCEP CFSv2 freerun

The latest version of the state-of-the-art global land–atmosphere–ocean coupled climate forecast system of NCEP has shown considerable improvement in various aspects of the Indian summer monsoon. However, climatological mean dry bias over the Indian sub-continent is further increased as compared to the previous version. Here we have attempted to link this dry bias with climatological mean bias in the Eurasian winter/spring snow, which is one of the important predictors of the Indian summer monsoon rainfall (ISMR). Simulation of interannual variability of the Eurasian snow and its teleconnection with the ISMR are quite reasonable in the model. Using composite analysis it is shown that a positive snow anomaly, which is comparable to the systematic bias in the model, results into significant decrease in the summer monsoon rainfall over the central India and part of the Equatorial Indian Ocean. Decrease in the summer monsoon rainfall is also found to be linked with weaker northward propagation of intraseasonal oscillation (ISO). A barotropic stationary wave triggered by positive snow anomaly over west Eurasia weakens the upper level monsoon circulation, which in turn reduces the zonal wind shear and hence, weakens the northward propagation of summer monsoon ISOs. A sensitivity experiment by reducing snow fall over Eurasian region causes decrease in winter and spring snow depth, which in turn leads to decrease in Indian summer monsoon rainfall. Results from the sensitivity experiment corroborate with those of composite analysis based on long free run. This study suggests that further improvements in the snow parametrization schemes as well as Arctic sea ice are needed to reduce the Eurasian snow bias during winter/spring, which may reduce the dry bias over Indian sub-continent and hence predictability aspect of the model.     

Tectono-magmatic evolution of Tethyan oceanic lithosphere in supra subduction zone fore arc regime: Geochemical fingerprints from crust-mantle sections of Naga Hills Ophiolite

The Naga Hills Ophiolite(NHO) belt in the Indo-Myanmar range(IMR) represents a segment of Tethyan oceanic crust and upper mantle that was involved in an eastward convergence and collision of the Indian Plate with the Burmese Plate during the Late Cretaceous-Eocene.Here, we present a detailed petrological and geochemical account for the mantle and crustal sections of NHO, northeastern India to address(i) the mantle processes and tectonic regimes involved in their genesis and(ii) their coherence in terms of the thermo-tectonic evolution of Tethyan oceanic crust and upper mantle.The NHO suite comprises well preserved crustal and mantle sections discretely exposed at Moki, Ziphu, Molen, Washelo and Lacham areas.The ultramafic-mafic lithologies of NHO are mineralogically composed of variable proportions of olivine, orthopyroxene, clinopyroxene and plagioclase.The primary igneous textures for the mantle peridotites have been overprinted by extensive serpentinisation whereas the crustal section rocks reflect crystal cumulation in a magma chamber.Chondrite normalised REE profiles for the cumulate peridotite-olivine gabbro-gabbro assemblage constituting the crustal section of NHO show flat to depleted LREE patterns consistent with their generation from depleted MORB-type precursor melt in an extensional tectonic setting, while the mantle peridotites depict U-shaped REE patterns marked by relative enrichment of LREE and HREE over MREE.These features collectively imply a dual role of depleted MORB-type and enriched arc-type mantle components for their genesis with imprints of melt-rock and fluid-rock interactions.Tectonically, studied lithologies from NHO correspond to a boninitic to slab-proximal Island Arc Tholeiite affinity thereby conforming to an intraoceanic supra subduction zone(SSZ) fore-arc regime coherent with the subduction initiation process.The geochemical attributes for the crustal and mantle sections of NHO as mirrored by Zr/Hf, Zr/Sm, Nb/Ta, Zr/Nb, Nb/U, Ba/Nb, Ba/Th, Ba/La and Nd/Hf ratios propound a two-stage petrogenetic process:(i) a depleted fore arc basalt(FAB) type tholeiitic melt parental to the crustal lithologies was extracted from the upwelling asthenospheric mantle at SSZ fore-arc extensional regime thereby rendering a refractory residual upper mantle;(ii) the crust and upper mantle of the SSZ fore arc were progressively refertilised by boninitic melts generated in response to subduction initiation and slab-dehydration.The vestiges of Tethyan oceanic lithosphere preserved in NHO represent an accreted intra-oceanic fore arc crust and upper mantle section which records a transitional geodynamic evolution in a SSZ regime marked by subduction initiation, fore arc extension and arc-continent accretion.     

Development of a Speckle Interferometer and the Measurement of Fried's Parameter (ro) at the Telescope Site

A new optical speckle interferometer for use at the 2.34 meter Vainu Bappu Telescope (VBT), at Vainu Bappu Observatory (VBO), Kavalur, India, has been designed and developed. Provisions have been made for observation both at the prime focus (f/3,25), as well as at the Cassegrain focus (f/13) of the said telescope. The technical details of this sensitive instrument and the design features are described. An interface between the telescope and the afore-mentioned interferometer is made based on a concept of eliminating the formation of eddies due to the hot air entrapment. The performances of this instrument has been tested both at the laboratory, as well as at the Cassegrain end of the telescope. It is being used routinely to observe the speckle-grams of close-binary (separation < 1 arc second) stars. The size of the Fried's parameter, r_o, is also measured.     

Mass accretion by the nuclei of disk galaxies,II

Repeated explosions in the nuclei of galaxies are now accepted as observationally established phenomena. Each explosion leads to the ejection of gas from the central region of a galaxy with velocities depending on the strength of the explosive event. In the process the nucleus temporarily becomes gas-deficient. It is suggested that the mass los is replenished by the accretion of the mass which is shed by those evolved stars in the galactic bulge that possess relatively low rotational velocities. The gas to be accreted is assumed to be magnetized. In the present model, the accretion rate has been assumed to be a function of both radial distance and time. The cross-radial equation of motion has been solved to derive the expression for the rotational velocity which is found to bealmost linear with the radial distance from the centre. The radial equation has been solved to calculate the time-scale over which the nucleus accumulates sufficient mass to undergo instability and suffer explosion. The calculated time-scale range from few multiples of 10⁷ to a few multiples of 10⁸ yr. This range agrees very well with that as has been suggested on the basis of observation in the case of our own Galaxy.     

Multistage melt impregnation in Tethyan oceanic mantle: Petrochemical constraints from channelized melt flow in the Naga Hills Ophiolite

Ophiolitic sequences obducted onto continental margins allow field based observations coupled with petrochemical interrogations of upper mantle lithologies thereby aiding evaluation of compositional heterogeneity of oceanic mantle, depletion-enrichment events and geodynamic conditions governing oceanic lithosphere formation. The Naga Hills Ophiolite (NHO) suite preserves a segment of the Neotethyan oceanic lithosphere encompassing a package of mantle and crustal lithologies. This paper for the first time reports the occurrence of melt flow channels traversing the mantle section near Molen of the NHO and presents a comprehensive study involving chromite-spinel chemistry, bulk rock major, trace and PGE geochemistry to understand the petrogenesis and evolution in a geodynamic transition from mid oceanic ridge (MOR) to suprasubduction zone (SSZ). The spinel chemistry of peridotitic melt channels depicts both MOR-type and SSZ signatures underlining a transitional tectonic frame. Chromite chemistry and high Al₂O₃/TiO₂ ranging from 15.98–35.70 in concurrence with low CaO/Al₂O₃ ranging from 0.03–0.53; and chondrite normalised LREE > MREE < HREE patterns confirm the influx of boninitic melts into the refractory mantle. The boninitic signature shared by melt channels and host rock invokes a geochemical and geodynamic transition from anhydrous melting of depleted mantle to hydrated fluid flux melting resulting in boninitic melts, that subsequently impregnate and refertilise the fore arc mantle wedge in a SSZ regime at the nascent stage of subduction. The high Ba/Nb, Ba/Th, and Ba/La for the studied peridotites highlight the influx of subduction derived fluids in the supra subduction mantle. Further higher Zr/Hf and Nd/Hf with respect to primitive mantle values in concurrence with lower Nb/Ta suggest progressive refertilisation due to fluid- and melt-driven metasomatism of the refractory fore arc mantle wedge. The chondrite normalised PGE patterns suggest positive Ir and Ru anomalies stipulating the source to be refractory while enriched Pt and Pd underpins the mobilisation of these elements by subduction derived fluids and melts. The elevated abundances of PPGEs than IPGEs as cited by PPGE/IPGE > 1; and Pd/Pt avg. 0.85 for melt channels and 0.84 for host peridotites indicate fluid-fluxed metasomatism of fore arc mantle wedge with a S-undersaturated trend coupled with boninitic affinity. The mineral, trace, REE and PGE chemistry collectively emphasizes that the mantle peridotites of the NHO formed in a transitional geodynamic tectonic setting caused by fore arc extension during subduction initiation followed by rejuvenation by subduction derived fluids and boninitic melts, which typically are of the SSZ tectonic regime. The harzburgitic melt channels and host rock are refractory in nature, reflecting multiple episodes of melt extraction of about 5–15% and ~10–20% respectively from a spinel peridotite mantle source. The occurrences of these melt channels indicate segregation and percolation of melt through porous and channelized network in upper mantle peridotites.     

Bifurcations of dust acoustic solitary waves and periodic waves in an unmagnetized plasma with nonextensive ions

Bifurcations of dust acoustic solitary waves and periodic waves in an unmagnetized plasma with q-nonextensive velocity distributed ions are studied through non-perturbative approach. Basic equations are reduced to an ordinary differential equation involving electrostatic potential. After that by applying the bifurcation theory of planar dynamical systems to this equation, we have proved the existence of solitary wave solutions and periodic wave solutions. Two exact solutions of the above waves are derived depending on the parameters. From the solitary wave solution and periodic wave solution, the effect of the parameter (q) is studied on characteristics of dust acoustic solitary waves and periodic waves. The parameter (q) significantly influence the characteristics of dust acoustic solitary and periodic structures.     

Aquifer system response to intensive pumping in urban areas of the Gangetic plains,India: the case study of Patna

A significant component of domestic demand for water of urban areas located in the Gangetic plains is met by heavy pumping of groundwater. The present study is focused on the Patna municipal area, inhabited by 17 million people and spanning over 134 km², where entire urban water demand is catered from pumping by wells of various capacities and designs. The present study examines the nature of the aquifer system within the urban area, the temporal changes in the water/piezometric level and the recharge mechanism of the deeper aquifers. The aquifer system is made up of medium-to-coarse unconsolidated sand, lying under a ~40-m-thick predominantly argillaceous unit holding 8- to 13-m-thick localised sand layers and continues up to 220 m below ground. Groundwater occurs under semi-confined condition, with transmissivity of aquifers in 5,500–9,200 m² day^?1 range. Hydraulic head of the deeper aquifer remains in 9–19 m range below ground, in contrast to 1–9 m range of that of the upper aquitard zone. The estimated annual groundwater extraction from the deeper aquifer is ~212.0 million m³, which has created a decline of 3.9 m in the piezometric level of the deeper aquifer during the past 30 years. Unregulated construction of deep tube wells with mushrooming of apartment culture may further exacerbate the problem. The sand layers within the aquitard zone are experiencing an annual extraction of 14.5 million m³ and have exhibited stable water level trend for past one and half decades. This unit is recharged from monsoon rainfall, besides contribution from water supply pipe line leakage and seepage from unlined storm water drains.     

Streamflow modeling in a fluctuant climate using SWAT: Yass River catchment in south eastern Australia

Hydrological models play vital roles in understanding and management of surface water resources. The physically based distributed model Soil and Water Assessment Tool (SWAT) was applied to a small catchment in south eastern Australia to determine its ability to mimic low and high streamflows. The model was successfully calibrated using 1993–2002 streamflow data and validated using 2003–2011 data with a combination of manual and auto-calibration techniques for both monthly and daily time steps. Sensitivity analysis indicated that curve number for moisture condition II (CN2) is the most sensitive parameter for both time steps. In general, the model performance statistics indicated “very good” agreement between measured and simulated discharges for both calibration and validation periods. The model was able to satisfactorily simulate both low and high flows of the Yass River. Analysis of water balance components indicated that more than 90 % of the rainfall is lost as evapotranspiration and about 45 % of the streamflow is base flow. The calibrated and validated SWAT model can be used to analyze the effect of climate and land use changes on catchment wide hydrologic process.