The April 2012 Indian Ocean earthquakes: Seismotectonic context and implications for their mechanisms

The 11 April 2012 earthquakes (M-w 8.6 and M-w 8.2) were sourced within the Northern Wharton Basin in the northeastern part of the Indo-Australian diffuse plate boundary. This unusually active oceanic intraplate region has generated many large earthquakes in the past, most of which are believed to have occurred by strike-slip motion, triggered by the NW-SE oriented compressional stresses acting across the Indian and Australian plates. In the aftermath of the 2004 megathrust earthquake along the nearby Sunda Trench, increased seismicity in the Northern Wharton Basin is attributed to the stress transfer from the Sumatra-Andaman plate boundary. Models proposed for the April 2012 earthquakes differ somewhat in details but partly attribute their complex rupture to the reactivation of pre-existing structures. These structures include previously mapped N-S trending fracture zones within the Northern Wharton Basin and E-W lineations across the Ninetyeast Ridge. In this paper, we review the regional tectonics and past seismicity on the Indo-Australian Plate in order to understand the seismotectonic setting of the April 2012 Indian Ocean earthquakes. (c) 2014 Elsevier B.V. All rights reserved.

Post-absorptive glucose lowering in normal healthy individuals: An epidemiological observation

Post-absorptive glucose lowering (PALG) is observed in individuals with glucose intolerance and in healthy individuals. We report a prevalence of about 23% among healthy Asian Indians. Individuals with PALG are characterized by leaner phenotype, low body fat percentage, increased insulin sensitivity and higher fasting glucose levels. (C) 2014 Elsevier Ireland Ltd. All rights reserved.

Density Functional Theoretical Modeling, Electrostatic Surface Potential and Surface Enhanced Raman Spectroscopic Studies on Biosynthesized Silver Nanoparticles: Observation of 400 pM Sensitivity to Explosives

Interaction of adsorbate on charged surfaces, orientation of the analyte on the surface, and surface enhancement aspects have been studied. These aspects have been explored in details to explain the surface-enhanced Raman spectroscopic (SERS) spectra of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW or CL-20), a well-known explosive, and 2,4,6-trinitrotoluene (TNT) using one-pot synthesis of silver nanoparticles via biosynthetic route using natural precursor extracts of clove and pepper. The biosynthesized silver nanoparticles (bio Ag Nps) have been characterized using UV-vis spectroscopy, scanning electron microscopy and atomic force microscopy. SERS studies conducted using bio Ag Nps on different water insoluble analytes, such as CL-20 and TNT, lead to SERS signals at concentration levels of 400 pM. The experimental findings have been corroborated with density functional computational results, electrostatic surface potential calculations, Fukui functions and potential measurements.

Morphology controlled synthesis of wurtzite ZnS nanostructures through simple hydrothermal method and observation of white light emission from ZnO obtained by annealing the synthesized ZnS nanostructures

A controllable synthesis of phase pure wurtzite (WZ) ZnS nanostructures has been reported in this work at a low temperature of similar to 220 degrees C using ethylenediamine as the soft template and by varying the molar concentration of zinc to sulphur precursors as well as by using different precursors. A significant reduction in the formation temperature required for the synthesis of phase pure WZ ZnS has been observed. A strong correlation has been observed between the morphology of the synthesized ZnS nanostructures and the precursors used during synthesis. It has been found from Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) image analyses that the morphology of the ZnS nanocrystals changes from a block-like to a belt-like structure having an average length of similar to 450 nm when the molar ratio of zinc to sulphur source is increased from 1 : 1 to 1 : 3. An oriented attachment (OA) growth mechanism has been used to explain the observed shape evolution of the synthesized nanostructures. The synthesized nanostructures have been characterized by the X-ray diffraction technique as well as by UV-Vis absorption and photoluminescence (PL) emission spectroscopy. The as-synthesized nanobelts exhibit defect related visible PL emission. On isochronal annealing of the nanobelts in air in the temperature range of 100-600 degrees C, it has been found that white light emission with a Commission Internationale de I'Eclairage 1931 (CIE) chromaticity coordinate of (0.30, 0.34), close to that of white light (0.33, 0.33), can be obtained from the ZnO nanostructures obtained at an annealing temperature of 600 degrees C. UV light driven degradation of methylene blue (MB) dye aqueous solution has also been demonstrated using as-synthesized nanobelts and similar to 98% dye degradation has been observed within only 40 min of light irradiation. The synthesized nanobelts with visible light emission and having dye degradation activity can be used effectively in future optoelectronic devices and in water purification for cleaning of dyes.

Slow Slip Acceleration beneath Andaman Islands Triggered by the 11 April 2012 Indian Ocean Earthquakes

The M-w 8.6 and 8.2 strike-slip earthquakes that struck the northeast Indian Ocean on 11 April 2012 resulted in coseismic deformation both at near and distant sites. The slip distribution, deduced using seismic-wave analysis for the orthogonal faults that ruptured during these earthquakes, is sufficient to predict the coseismic displacements at the Global Positioning System (GPS) sites, such as NTUS, PALK, and CUSV, but fall short at four continuous sites in the Andaman Islands region. Slip modeling, for times prior to the events, suggests that the lower portion of the thrust fault beneath the Andaman Islands has been slipping at least at the rate of 40 cm/yr, in response to the 2004 Sumatra-Andaman coseismic stress change. Modeling of GPS displacements suggests that the en echelon and orthogonal fault ruptures of the 2012 intraplate oceanic earthquakes could have possibly accelerated the ongoing slow slip, along the lower portion of the thrust fault beneath the islands with a month-long slip of 4-10 cm. The misfit to the coseismic GPS displacements along the Andaman Islands could be improved with a better source model, assuming that no local process contributed to this anomaly.

Three-dimensional localization of multiple acoustic sources in shallow ocean with non-Gaussian noise

In this paper, a low-complexity algorithm SAGE-USL is presented for 3-dimensional (3-D) localization of multiple acoustic sources in a shallow ocean with non-Gaussian ambient noise, using a vertical and a horizontal linear array of sensors. In the proposed method, noise is modeled as a Gaussian mixture. Initial estimates of the unknown parameters (source coordinates, signal waveforms and noise parameters) are obtained by known/conventional methods, and a generalized expectation maximization algorithm is used to update the initial estimates iteratively. Simulation results indicate that convergence is reached in a small number of (<= 10) iterations. Initialization requires one 2-D search and one 1-D search, and the iterative updates require a sequence of 1-D searches. Therefore the computational complexity of the SAGE-USL algorithm is lower than that of conventional techniques such as 3-D MUSIC by several orders of magnitude. We also derive the Cramer-Rao Bound (CRB) for 3-D localization of multiple sources in a range-independent ocean. Simulation results are presented to show that the root-mean-square localization errors of SAGE-USL are close to the corresponding CRBs and significantly lower than those of 3-D MUSIC. (C) 2014 Elsevier Inc. All rights reserved.

Observation of Combined Effect of Temperature and Pressure on Cubic to Hexagonal Phase Transformation in ZnS at the Nanoscale

The temperature of allotropic phase transformation in ZnS (cubic to wurtzite) changes with pressure and particle size. In this paper we have explored the interrelation among these through a detailed study of ZnS powders obtained by a temperature-controlled high energy milling process. By employing the combined effect of temperature and pressure in an indigenously built cryomill, we have demonstrated a large-scale, low-temperature synthesis of wurtzite ZnS nanoparticles. The synthesized products have been characterized for their phase and microstructure by the use of X-ray diffraction and transmission electron microscopic techniques. Further, it has been demonstrated that the synthesized materials exhibit photoluminescence emissions in the UV-visible region with an unusual doublet pattern due to the presence of both cubic and hexagonal wurtzite domains in the same particles. By further fine-tuning the processing conditions, it may be possible to achieve controlled defect related photoluminescence emissions from the ZnS nanoparticles.

Observation of magnetically hard grain boundaries in double-perovskite Sr2FeMoO6

Unusual low-temperature magneto-resistance (MR) of ferromagnetic Sr2FeMoO6 polycrystals has been attributed to magnetically hard grain boundaries which act as spin valves. We detected the different magnetic hysteresis curves for the grains and the grain boundaries of polycrystalline Sr2FeMoO6 by utilizing the different probing depths of the different detection modes of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), namely, the total electron yield (TEY) mode (probing depth similar to 5 nm) and the total fluorescence yield (TFY) mode (probing depth similar to 100 nm). At 20 K, the magnetic coercivity detected in the TEY mode (H-c,H- TEY) was several times larger than that in the TFY mode (H-c,H- TFY), indicating harder ferromagnetism of the grain boundaries than that of the grains. At room temperature, the grain boundary magnetism became soft and H-c,H- TEY and H-c,H- TFY were nearly the same. From the line-shape analysis of the XAS and XMCD spectra, we found that in the grain boundary region the ferromagnetic component is dominated by Fe2+ or well-screened signals, while the non-magnetic component is dominated by Fe3+ or poorly screened signals. Copyright (C) EPLA, 2014

Sheltered coastal environments as archives of paleo-tsunami deposits: Observations from the 2004 Indian Ocean tsunami

The 2004 earthquake left several traces of coseismic land deformation and tsunami deposits, both on the islands along the plate boundary and distant shores of the Indian Ocean rim countries. Researchers are now exploring these sites to develop a chronology of past events. Where the coastal regions are also inundated by storm surges, there is an additional challenge to discriminate between the deposits formed by these two processes. Paleo-tsunami research relies largely on finding deposits where preservation potential is high and storm surge origin can be excluded. During the past decade of our work along the Andaman and Nicobar Islands and the east coast of India, we have observed that the 2004 tsunami deposits are best preserved in lagoons, inland streams and also on elevated terraces. Chronological evidence for older events obtained from such sites is better correlated with those from Thailand, Sri Lanka and Indonesia, reiterating their usefulness in tsunami geology studies. (C) 2014 Elsevier Ltd. All rights reserved.

Observation of a reversible isomorphous phase transition and an interplay of ``sigma-holes'' and ``pi-holes'' in Fmoc-Leu-psiCH2-NCS]

Fmoc-Leu-psiCH2NCS] undergoes a reversible isomorphous phase transition upon cooling. The crystal structure at 100 K displays a short N=C=S center dot center dot center dot N=C=S intermolecular interaction, which has been characterized based on experimental charge density analysis, as a stabilizing interaction with both sigma-holes and pi-holes acting cooperatively.

Observation of Room Temperature Ferromagnetism in InN Nanostructures

The room temperature ferromagnetic behavior of InN nanosfructures grown by molecular beam epitaxy (MBE) is explored by means of magnetization measurements. The saturation magnetization and remanent magnetization are found to be strongly dependent on the size of the nanostructures. This suggests that the ferromagnetism is essentially confined to the surface of the nanostructures due to the possible defects. Raman spectroscopy shows the existence of indium vacancies which could be the source of ferromagnetic ordering in InN nanostructures.

Simple chemical aqueous synthesis of dahlia nanoflower consisting of finger-like ZnO nanorods and observation of stable ultraviolet photoluminescence emission

In this work, we have reported the synthesis of dahlia flower-like ZnO nanostructures consisting of human finger-like nanorods by the hydrothermal method at 120 degrees C and without using any capping agent. Optical properties of the samples, including UV-vis absorption and photoluminescence (PL) emission characteristics are determined by dispersing the samples in water as well as in ethanol media. The quenching of PL emission intensity along-with the red shifting of the PL emission peak are observed when the samples are dispersed in water in comparison to those obtained after dispersing the samples in ethanol. It has been found that PL emission characteristic, particularly the spectral nature of PL emission, of the samples remains almost unaltered (except some improvement in UV PL emission) even after thermally annealing it for 2 h at the temperature of 300 degrees C. Also the synthesized powder samples, kept in a plastic container, showed a very stable PL emission even after 15 months of synthesis. Therefore, the synthesized samples might be useful for their applications in future optoelectronics devices. (C) 2014 Elsevier Ltd. All rights reserved.

Kaiser effect observation in reinforced concrete structures and its use for damage assessment

Reinforced concrete (RC) beams of span 3 m were tested under incremental cyclic load at different loading rates and simultaneously during the fracture process in the RC beams acoustic emissions (AE) were recorded. An attempt has been made to study the Kaiser effect as a measure of damage in RC beams. It was observed that RC beams made with high strength concrete under incremental cyclic loading showed an obvious Kaiser effect before the failure load. The results may be useful to study the damage in concrete structures and provide a reference for the application of Kaiser effect in engineering practice. (C) 2014 Politechnika Wroclawska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved.

Observation of coherent population trapping in a V-type two-electron system

We observe coherent population trapping (CPT) in a two-electron atom-Yb-174-using the S-1(0), F= 0 -> P-3(1), F `= 1 transition. CPT is not possible for such a transition according to one-electron theory because the magnetic sublevels form a V-type system, but in a two-electron atom like Yb, the interaction of the electrons transforms the level structure into a V-type system, which allows the formation of a dark state and hence the observation of CPT. Since the two levels involved are degenerate, we use a magnetic field to lift the degeneracy. The single fluorescence dip then splits into five dips-the central unshifted one corresponds to coherent population oscillation, while the outer four are due to CPT. The linewidth of the CPT resonance is about 300 kHz and is limited by the natural linewidth of the excited state, which is to be expected because the excited state is involved in the formation of the dark state.

Observation of photobleaching and intensity dependent kinetics in Ge22As22Se56 thin films under sub-bandgap light illumination

We experimentally demonstrate photobleaching (PB) in Ge22As22Se56 thin films, when illuminated with a diode pumped solid state laser (DPSSL) of wavelength 671 nm, which is far below the optical bandgap of the sample. Interestingly, we found that PB is a slow process and occurs even at moderate pump beam intensity of 0.2 W/cm(2), however the kinetics remain rather different.