Imprints of Archean to Neoproterozoic crustal processes in the Madurai Block, Southern India

Madurai Block, the largest crustal block in the Southern Granulite Terrane (SGT) of Peninsular India, preserves the imprints of multistage tectonic evolution. Here, we present U-Pb and Hf isotope data on zircons from a charnockite-granite suite in the north-western part of this block. The oscillatory zoning, and the LREE to HREE enriched patterns of the zircons with positive Ce and negative Eu anomalies suggest that the zircon cores are of magmatic origin, with ages in the range of 2634-2435 Ma implying Neoarchean-Paleoproterozoic magmatism followed by subsequent metamorphism and protocontinent formation in the north-western part of the Madurai Block. A regional 550-500 Ma metamorphic overprint is also preserved in the zircons coinciding with the final amalgamation of the Gondwana supercontinent. The Hf isotopic data suggest that the granite and charnockite were derived from isotopically heterogeneous juvenile crustal domains and the charnockites show a significant contribution of mantle-derived components. Therefore, the Hf isotopic data reflect mixing of crustal and mantle-derived sources for the generation of Neoarchean crust in the north-western Madurai Block, possibly in a suprasubduction zone setting during continent building processes. (c) 2014 Elsevier Ltd. All rights reserved.

Community-managed forests and wildlife-friendly agriculture play a subsidiary but not substitutive role to protected areas for the endangered Asian elephant

Global conservation policy is increasingly debating the feasibility of reconciling wildlife conservation and human resource requirements in land uses outside protected areas (PAs). However, there are few quantitative assessments of whether or to what extent these `wildlife-friendly' land uses fulfill a fundamental function of PAs-to separate biodiversity from anthropogenic threats. We distinguish the role of wildlife-friendly land uses as being (a) subsidiary, whereby they augment PAs with secondary habitat, or (b) substitutive, wherein they provide comparable habitat to PAs. We tested our hypotheses by investigating the influence of land use and human presence on space-use intensity of the endangered Asian elephant (Elephas maximus) in a fragmented landscape comprising PAs and wildlife-friendly land uses. We applied multistate occupancy models to spatial data on elephant occurrence to estimate and model the overall probability of elephants using a site, and the conditional probability of high-intensity use given that elephants use a site. The probability of elephants using a site regardless of intensity did not vary between PAs and wildlife-friendly land uses. However, high-intensity use declined with distance to PM, and this effect was accentuated by an increase in village density. Therefore, while wildlife-friendly land uses did play a subsidiary conservation role, their potential to substitute for PAs was offset by a strong human presence. Our findings demonstrate the need to evaluate the role of wildlife-friendly land uses in landscape-scale conservation; for species that have conflicting resource requirements with people, PAs are likely to provide crucial refuge from growing anthropogenic threats. (C) 2014 Elsevier Ltd. All rights reserved.

Highly Sensitive Carbon Nanotubes Coated Etched Fiber Bragg Grating Sensor for Humidity Sensing

The sensing of relative humidity (RH) at room temperature has potential applications in several areas ranging from biomedical to horticulture, paper, and textile industries. In this paper, a highly sensitive humidity sensor based on carbon nanotubes (CNTs) coated on the surface of an etched fiber Bragg grating (EFBG) sensor has been demonstrated, for detecting RH over a wide range of 20%-90% at room temperature. When water molecules interact with the CNT coated EFBG, the effective refractive index of the fiber core changes, resulting in a shift in the Bragg wavelength. It has been possible to achieve a high sensitivity of similar to 31 pm/% RH, which is the highest compared with many of the existing FBG-based humidity sensors. The limit of detection in the CNT coated EFBG has been found to be similar to 0.03 RH. The experimental data shows a linear response of Bragg wavelength shift with increase in humidity. This novel method of incorporating CNTs on to the FBG sensor for humidity sensing has not been reported before.

Monitoring urbanization and its implications in a mega city from space: Spatiotemporal patterns and its indicators

Rapid and invasive urbanization has been associated with depletion of natural resources (vegetation and water resources), which in turn deteriorates the landscape structure and conditions in the local environment. Rapid increase in population due to the migration from rural areas is one of the critical issues of the urban growth. Urbanisation in India is drastically changing the land cover and often resulting in the sprawl. The sprawl regions often lack basic amenities such as treated water supply, sanitation, etc. This necessitates regular monitoring and understanding of the rate of urban development in order to ensure the sustenance of natural resources. Urban sprawl is the extent of urbanization which leads to the development of urban forms with the destruction of ecology and natural landforms. The rate of change of land use and extent of urban sprawl can be efficiently visualized and modelled with the help of geo-informatics. The knowledge of urban area, especially the growth magnitude, shape geometry, and spatial pattern is essential to understand the growth and characteristics of urbanization process. Urban pattern, shape and growth can be quantified using spatial metrics. This communication quantifies the urbanisation and associated growth pattern in Delhi. Spatial data of four decades were analysed to understand land over and land use dynamics. Further the region was divided into 4 zones and into circles of 1 km incrementing radius to understand and quantify the local spatial changes. Results of the landscape metrics indicate that the urban center was highly aggregated and the outskirts and the buffer regions were in the verge of aggregating urban patches. Shannon's Entropy index clearly depicted the outgrowth of sprawl areas in different zones of Delhi. (C) 2014 Elsevier Ltd. All rights reserved.

Metal-organic chemical vapor-deposited cobalt oxide films as negative electrodes for thin film Li-ion battery

In this study, thin films of cobalt oxide (Co3O4) have been grown by the metal-organic chemical vapor deposition (MOCVD) technique on stainless steel substrate at two preferred temperatures (450 degrees C and 500 degrees C), using cobalt acetylacetonate dihydrate as precursor. Spherical as well as columnar microstructures of Co3O4 have been observed under controlled growth conditions. Further investigations reveal these films are phase-pure, well crystallized and carbon-free. High-resolution TEM analysis confirms that each columnar structure is a continuous stack of minute crystals. Comparative study between these Co3O4 films grown at 450 degrees C and 500 degrees C has been carried out for their application as negative electrodes in Li-ion batteries. Our method of electrode fabrication leads to a coating of active material directly on current collector without any use of external additives. A high specific capacity of 1168 micro Ah cm(-2) mu m(-1) has been measured reproducibly for the film deposited at 500 degrees C with columnar morphology. Further, high rate capability is observed when cycled at different current densities. The Co3O4 electrode with columnar structure has a specific capacity 38% higher than the electrode with spherical microstructure (grown at 450 degrees C). Impedance measurements on the Co3O4 electrode grown at 500 degrees C also carried out to study the kinetics of the electrode process. (C) 2014 Published by Elsevier B.V.

Cryogenian magmatism and crustal reworking in the Southern Granulite Terrane, India

Understanding Neoproterozoic crustal evolution is fundamental to reconstructing the Gondwana supercontinent, which was assembled at this time. Here we report evidence of Cryogenian crustal reworking in the Madurai Block of the Southern Granulite Terrane of India. The study focuses on a garnet-bearing granite-charnockite suite, where the granite shows in situ dehydration into patches and veins of incipient charnockite along the contact with charnockite. The granite also carries dismembered layers of Mg-Al-rich granulite. Micro-textural evidence for dehydration of granite in the presence of CO2-rich fluids includes the formation of orthopyroxene by the breakdown of biotite, neoblastic zircon growth in the dehydration zone, at around 870 degrees C and 8kbar. The zircon U-Pb ages suggest formation of the granite, charnockite, and incipient charnockite at 836 +/- 73, 831 +/- 31, and 772 +/- 49Ma, respectively. Negative zircon epsilon Hf (t) (-5 to -20) values suggest that these rocks were derived from a reworked Palaeoproterozoic crustal source. Zircon grains in the Mg-Al-rich granulite record a spectrum of ages from ca. 2300 to ca. 500Ma, suggesting multiple provenances ranging from Palaeoproterozoic to mid-Neoproterozoic, with neoblastic zircon growth during high-temperature metamorphism in the Cambrian. We propose that the garnet-bearing granite and charnockite reflect the crustal reworking of aluminous crustal material indicated by the presence of biotite+quartz+aluminosilicate inclusions in the garnet within the granite. This crustal source can be the Mg-Al-rich layers carried by the granite itself, which later experienced high-temperature regional metamorphism at ca. 550Ma. Our model also envisages that the CO2 which dehydrated the garnet-bearing granite generating incipient charnockite was sourced from the proximal massive charnockite through advection. These Cryogenian crustal reworking events are related to prolonged tectonic activities prior to the final assembly of the Gondwana supercontinent.

Effect of radio frequency power and thickness on the electrochemical properties of Li2-x MnO3-y thin films

In the present work, Li2-x MnO3-y (LMO) thin films have been deposited by radio frequency (RF) reactive magnetron sputtering using acid-treated Li2MnO3 powder target. Systematic investigations have been carried out to study the effect of RF power on the physicochemical properties of LMO thin films deposited on platinized silicon substrates. X-ray diffraction, electron microscopy, surface chemical analysis and electrochemical studies were carried out for the LMO films after post deposition annealing treatment at 500 A degrees C for 1 h in air ambience. Galvanostatic charge discharge studies carried out using the LMO thin film electrodes, delivered a highest discharge capacity of 139 mu Ah mu m(-1) cm(-2) in the potential window 2.0-3.5 V vs. Li/Li+ at 100 W RF power and lowest discharge capacity of 80 mu Ah mu m(-1) cm(-2) at 75 W RF power. Thereafter, the physicochemical properties of LMO films deposited using optimized RF power 100 W on stainless steel substrates has been studied in the thickness range of 70 to 300 nm as a case study. From the galvanostatic charge discharge experiments, a stable discharge capacity of 68 mu Ah mu m(-1) cm(-2) was achieved in the potential window 2.0-4.2 V vs. Li/Li+ tested up to 30 cycles. As the thickness increased, the specific discharge capacity started reducing with higher magnitude of capacity fading.

Nanomaterials coated multiplexed fiber Bragg grating for multiparameter sensing

Fiber Bragg Grating (FBG) sensors have been extensively used for strain and temperature sensing. However, there is still a need to measure multiple environmental parameters with a single sensor system. We demonstrate a multiplexed FBG sensor with various nano materials (polyallylamine-amino-carbon-nanotube, carbon nanotubes, polyelectrolyte and metals) coated onto the surface of the core/cladding FBG for sensing multiple environmental parameters such as pH (64 pm/pH), protein concentration (5 pm/mu g/ml), temperature (15 pm/degrees C), humidity (31 pm/% RH), gas concentration (7 pm/1000 ppm), and light intensity (infrared: 33 pm/mW, visible: 12 pm/mW and UV: 1 pm/mW) utilizing the same FBG based platform.

Metastable monoclinic and orthorhombic phases and electric field induced irreversible phase transformation at room temperature in the lead-free classical ferroelectric BaTiO3

For decades it has been a well-known fact that among the few ferroelectric compounds in the perovskite family, namely, BaTiO3, KNbO3, PbTiO3, and Na1/2Bi1/2TiO3, the dielectric and piezoelectric properties of BaTiO3 are considerably higher than the others in polycrystalline form at room temperature. Further, similar to ferroelectric alloys exhibiting morphotropic phase boundary, single crystals of BaTiO3 exhibit anomalously large piezoelectric response when poled away from the direction of spontaneous polarization at room temperature. These anomalous features in BaTiO3 remained unexplained so far from the structural standpoint. In this work, we have used high-resolution synchrotron x-ray powder diffraction, atomic resolution aberration-corrected transmission electron microscopy, in conjunction with a powder poling technique, to reveal that at 300 K (i) the equilibrium state of BaTiO3 is characterized by coexistence of metastable monoclinic Pm and orthorhombic (Amm2) phases along with the tetragonal phase, and (ii) strong electric field switches the polarization direction from the 001] direction towards the 101] direction. These results suggest that BaTiO3 at room temperature is within an instability regime, and that this instability is the fundamental factor responsible for the anomalous dielectric and piezoelectric properties of BaTiO3 as compared to the other homologous ferroelectric perovskite compounds at room temperature. Pure BaTiO3 at room temperature is therefore more akin to lead-based ferroelectric alloys close to the morphotropic phase boundary where polarization rotation and field induced ferroelectric-ferroelectric phase transformations play a fundamental role in influencing the dielectric and piezoelectric behavior.

Piezoelectric properties of individual nanocrystallites of Ba0.85Ca0.15Zr0.1Ti0.9O3 obtained by oxalate precursor route

Nanocrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powder was synthesized via the complex oxalate precursor route at a relatively low temperature (800 degrees C/5 h). The phase formation temperature of BCZT at nanoscale was confirmed by thermogravimetric (TG), differential thermal analysis (DTA) followed by X-ray powder diffraction (XRD) studies. Fourier transform infrared (FTIR) spectroscopy was carried out to confirm the complete decomposition of oxalate precursor into BCZT phase. The XRD and profile fitting revealed the coexistence of cubic and tetragonal phases and was corroborated by Raman study. Transmission electron microscopy (TEM) carried out on 800 degrees C and 1000 degrees C/5 h heat treated BCZT powder revealed the crystallite size to be in the range of 20-50 nm and 40-200 nm respectively. The optical band gap for BCZT nanocrystalline powder was obtained using Kubelka Munk function and was found to be around 3.12 +/- 0.02 eV and 3.03 +/- 0.02 eV respectively for 800 degrees C (20-50 nm) and 1000 degrees C/5 h (40-200 nm) heat treated samples. The piezoelectric properties were studied for two different crystallite sizes (30 and 70 nm) using a piezoresponse force microscope (PFM). The d(33) coefficients obtained for 30 nm and 70 nm sized crystallites were 4 pm V-1 and 47 pm V-1 respectively. These were superior to that of BaTiO3 nanocrystal (approximate to 50 nm) and promising from a technological/industrial applications viewpoint.

Chemical-free graphene by unzipping carbon nanotubes using cryo-milling

Current paper reports synthesis of chemical free graphene by unzipping of the carbon nanotubes (CNTs) using high strain rate deformation at 150K. A specially designed cryomill operating at 150 K was used for the experiments. The mechanism of unzipping was further explored using molecular dynamics (MD) simulations. Both experimental and simulation results reveal two modes of unzipping through radial and shear loading. (C) 2015 Elsevier Ltd. All rights reserved.

Rapid and facile one-step synthesis of LiTaO3 nanorods

Single crystalline LiTaO3 nanorods (length of 2.5-6 mu m and diameter of 200-500 nm) were synthesized via a facile molten-salt technique. An individual single crystalline nanorod exhibited a piezoelectric coefficient of 8 pm V-1. An improved optical frequency-doubling efficiency was observed in the case of LiTaO3 nanorods as compared to that of cubic crystallites of similar size.

Strengthening and weakening by repeated dynamic impact in microcrystals and nanocrystals

Experiments on micrograined (mg) and nanocrystalline (nc) Ni revealed strengthening and weakening following repeated dynamic impact. The strengthening in mg-Ni arises from intragranular dislocations without a significant change in grain size, whereas the weakening in nc-Ni is due to concurrent grain growth. The strength of mg and nc-Ni samples after deformation settles at similar to 900 MPa, with differing contributions from intragranular dislocations and grain sizes. (C) 2015 Elsevier B.V. All rights reserved.