[en] Electron spin resonance (ESR) is one of the modern techniques useful in dating events that are up to 1 million years old and hence very useful in understanding various geological events. A preliminary attempt has been made to date fossil teeth found in Perur, a historical town in Coimbatore district in Tamilnadu. This sample for dating was collected at 1.3m below the surface of the land. The sample was divided into six sets and five of which were given an additive dose (AD) by using γ rays of 405 Gy, 810 Gy, 1620 Gy, 2340 Gy and 3240 Gy respectively. The sample shows similar ESR spectra having g value 2.0045. The absorption lines at this 'g' value has been used to estimate the age, assuming the external dose rate to be 1.12mGy/a. The calculated age of the sample is 2102.67 years old, and the result is good agreement with the reference data. (author)

[en] Visual MODLOW is a Graphical User Interface for the USGS MODFLOW. It is a commercial software that is popular among the hydrogeologists for its user-friendly features. The software is mainly used for Groundwater flow and contaminant transport models under different conditions. This article is intended to review the versatility of its applications in groundwater modelling for the last 22 years. Agriculture, airfields, constructed wetlands, climate change, drought studies, Environmental Impact Assessment (EIA), landfills, mining operations, river and flood plain monitoring, salt water intrusion, soil profile surveys, watershed analyses, etc., are the areas where the software has been reportedly used till the current date. The review will provide a clarity on the scope of the software in groundwater modelling and research. (paper)

[en] Groundwater contamination has become so alarming that the existing valuable freshwater resources are at stake. Landfilling of solid refuse without pre-emptive measures, over the years, leads to the utter depletion of the groundwater quality in its vicinity. The Kodungaiyur landfill at the Perambur taluk located in the northernmost region of the Chennai metropolitan, is such a poorly managed landfill. This research article is intended to exhibit a detailed study report on the physicochemical and bacteriological parametric analyses of the currently available subsurface water in and around the landfill area. Besides being evident from the faecal coliform test that the water is not potable, the chief objective was to investigate the suitability of groundwater for irrigation. Representative samples of groundwater were collected from inside the landfill site, and the residential areas located within 2 km from the site and analysed using standard methods. The test results were interpreted by employing exhaustive statistical approaches. It is evident to the interpretations that, out of the nine sampled locations, seven were found to be endowed with a groundwater quality fit enough for irrigation. (paper)

[en] Hydrated tungsten oxide (WO₃·H₂O)-based nanoparticles were synthesized using a simple and inexpensive facile microwave irradiation process, by doping chromium (2 wt%, 3 wt%, 5 wt% and 7 wt%) at 2.45 GHz with the power of 180 W for 10 min for gas sensor application. The resultant products were annealed at 600 °C at the ambient atmosphere in order to improve the crystallinity and to remove the impurities. The products were characterized by using powder XRD which confirmed the formation of orthorhombic and monoclinic structure of both as-prepared and annealed samples, respectively. Atomic force microscope shows the role of chromium in determining the surface morphology of the resultant products at microscopic level, Fourier transform infrared spectroscopic analysis confirmed the presence of essential functional groups formed through chemical bonds of the end products, room temperature UV–VIS DRS studies showed the optical behavior of the samples through emissions and band gap energy of the respective materials. Cyclic voltammetry study confirmed the suitability of the prepared chromium-doped tungsten oxide (WO₃) materials through electrochemical property for photocatalytic and sensor applications.

[en] Tin oxide hexagonal-shaped nanodiscs (SnO) and spherical nanoparticles (SnO₂) have been prepared by using a simple household microwave irradiation method with an operating frequency of 2.45 GHz. This technique permits us to produce gram quantity of homogeneous nanoparticles in just 10 min. The crystallite size was evaluated from powder X-ray diffraction (XRD) studies and was in the 20 to 25 nm range. Transmission electron microscopy (TEM) analysis showed that the as prepared SnO form as hexagonal-shaped nanodiscs and upon subsequent annealing at 500 deg. C for 5 h in air, the SnO gets converted to spherical-shaped nanoparticles of SnO₂. The SnO₂ sample shows good sensitivity towards the relative humidity. The calculated response and recovery time were found to be 32 s and 25 s respectively. These results indicate promising applications of SnO₂ nanoparticles in a highly sensitive environmental monitoring and humidity controlled electronic devices. The samples were further subjected to thermal analyses (TG-DTA) and UV-VIS diffusion reflectance spectroscopy (DRS) studies.

[en] Research highlights: → We have synthesized tungsten oxide (WO_3-δ) nanoparticles by microwave irradiation method for the first time using EDTA as surface modulator. The variation in stoichiometric oxygen content of the annealed samples clearly indicates the role of EDTA in reaction medium. The variation in oxygen content also modified the transparency of the end product confirming the change in optical conductivity. - Abstract: We report the synthesis of crystalline W₁₈O₄₉ with nanosheet like morphology by low cost microwave irradiation method without employing hydrothermal process for the first time. Initially, WO₃.H₂O was synthesized using ethylenediaminetetraacetic acid (EDTA) as surface modulator. The product was annealed at 600 ^oC for 6 h in ambient atmosphere in order to obtain anhydrous tungsten oxide W₁₈O₄₉. Powder X-ray diffraction results confirmed the as prepared WO₃.H₂O to be orthorhombic and W₁₈O₄₉ to be monoclinic phase, respectively. Transmission electron micrographs (TEM) revealed that the W₁₈O₄₉ nanosheets have the average dimensions of the order of 250 nm in length and around 150 nm in width. UV-visible diffusion reflectance spectroscopic (DRS) studies revealed the band gap energies to be 3.28 and 3.47 eV for WO₃.H₂O and W₁₈O₄₉ samples, respectively. The growth mechanism of two dimensional W₁₈O₄₉ nanosheets is discussed.

[en] Hydrated tungsten oxide (WO₃·H2_O)-based nanoparticles were synthesized using a simple and inexpensive facile microwave irradiation process, by doping chromium (2 wt%, 3 wt%, 5 wt% and 7 wt%) at 2.45 GHz with the power of 180 W for 10 min for gas sensor application. The resultant products were annealed at 600 °C at the ambient atmosphere in order to improve the crystallinity and to remove the impurities. The products were characterized by using powder XRD which confirmed the formation of orthorhombic and monoclinic structure of both as-prepared and annealed samples, respectively. Atomic force microscope shows the role of chromium in determining the surface morphology of the resultant products at microscopic level, Fourier transform infrared spectroscopic analysis confirmed the presence of essential functional groups formed through chemical bonds of the end products, room temperature UV–VIS DRS studies showed the optical behavior of the samples through emissions and band gap energy of the respective materials. Cyclic voltammetry study confirmed the suitability of the prepared chromium-doped tungsten oxide (WO₃) materials through electrochemical property for photocatalytic and sensor applications. (author)