A comparative study of erbium oxide and gadolinium oxide high-k dielectric thin films grown by low-pressure metalorganic chemical vapour deposition (MOCVD) using beta-Diketonates as precursors

In this paper, a comparative study of thin films of Er2O3 and Gd2O3 grown on n-type Si(100) by low-pressure metalorganic chemical vapour deposition (MOCVD) under the identical conditions has been presented. beta-Diketonate complex of rate earth metals was used as precursor. Description on the evolution of the morphology, structure, optical, and electrical characteristics of films with respect to growth parameters and post-deposition annealing process has been presented. As-gown Gd2O3 films grow with <111> texture, whereas the texture of Er2O3 films strongly depends on the growth temperature (either <100> or <111>). Compositional analysis reveals that the Gd2O3 films grown at or above 500degreesC are carbon free whereas Er2O3 films at upto 525degreesC show the presence of heteroatoms and Er2O3 films grown above 525degreesC are carbon five. The effective dielectric constant is in the range of 7-24, while the fixed charge density is in the range - 10(11) to 10(10) CM-2 as extracted from the C-V characteristics. DC I-V study was carried out to examine the leakage behaviour of films. It reveals that the as-grown Gd2O3 film was very leakey in nature. Annealing of the films in oxidizing ambient for a period of 20 min results in a drastic improvement in the leakage behaviour. The presence of heteroatoms (such as carbon) and their effect on the properties of films are discussed.

Effect of dehydration on the mechanical properties of sodium saccharin dihydrate probed with nanoindentation

Nanoindentation is used to explore the variation of mechanical properties associated with the dehydration process in sodium saccharin dihydrate. Upon indenting using a Berkovich tip, (011) and (101) faces exhibit explicit mechanical anisotropy that is consistent with the underlying crystal structure and intermolecular interactions. For freshly grown crystals, (011) is stiffer than (101) by 14%, while (101) is harder than (011) by 8%. Being a heavily hydrated system, the measured mechanical responses contain information pertinent to the fluidity associated with lattice water. Indentation on (011) with a sharp cube-corner tip induces a fluid flow; this observation is uncommon in molecular crystals. The crystals effloresce over a period of time with the generation of a more compact crystal structure and consequently increasing H and E.

Impact of Disturrance on Composition, Structure, And Floristics of Tropical Moist Forests in Uttara Kannada District, Western Ghats, India

Impact of disturbance on forest stand density, basal area, dbh class distribution of density and basal area, species richness, species diversity and similarity index was assessed through monitoring six, one-hectare, permanent forest plots after a period of 24 years in tropical moist forests of Uttara Kannada district, Western Ghats, India. It was observed that all sites lost trees due to removal by people and mortality. Loss of trees was more in sites that are easily accessible and closer to human habitation. In spite of a decrease in tree density, an increase in basal area was observed in some forest plots, which could be on account of stimulatory growth of surviving trees. Decrease in basal area in other sites indicates greater human pressure and overexploitation of trees. Preponderance of lower girth class trees, and a unimodal reverse `J-shaped' curve of density distribution as observed in majority of the sites in the benchmark year, was indicative of regenerating status of these forests. The decrease in number of species in all forest sites was due to indiscriminate removal of trees by people, without sparing species with only a few individuals, and also due to mortality of trees of rare species. Higher species richness and diversity in the lowest dbh class in most of the sites in the benchmark year is indicative of the existence of favorable conditions for sylvigenesis. The decrease in the similarity index suggests extirpation of species, favoring invasion and colonization by secondary species. To minimize human pressure on forests and to facilitate regeneration and growth, proper management planning and conservation measures are needed.

Multi-decadal variation of the net downward shortwave radiation over south Asia: The solar dimming effect

The solar radiation flux at the earth's surface has gone through decadal changes of decreasing and increasing trends over the globe. These phenomena known as dimming and brightening, respectively, have attracted the scientific interest in relation to the changes in radiative balance and climate. Despite the interest in the solar dimming/brightening phenomenon in various parts of the world, south Asia has not attracted great scientific attention so far. The present work uses the net downward shortwave radiation (NDSWR) values derived from satellites (Modern Era Retrospective-analysis for Research and Applications, MERRA 2D) in order to examine the multi-decadal variations in the incoming solar radiation over south Asia for the period of 1979-2004. From the analysis it is seen that solar dimming continues over south Asia with a trend of -0.54 Wm(-2) yr(-1). Assuming clear skies an average decrease of -0.05 Wm(-2)yr(-1) in NDSWR was observed, which is attributed to increased aerosol emissions over the region. There is evidence that the increase in cloud optical depth plays the major role for the solar dimming over the area. The cloud optical depth (MERRA retrievals) has increased by 10.7% during the study period, with the largest increase to be detected for the high-level (atmospheric pressure P < 400 hPa) clouds (31.2%). Nevertheless, the decrease in solar radiation and the role of aerosols and clouds exhibit large monthly and seasonal variations directly affected by the local monsoon system, the anthropogenic and natural aerosol emissions. All these aspects are examined in detail aiming at shedding light into the solar dimming phenomenon over a densely populated area. (C) 2011 Elsevier Ltd. All rights reserved.

Bimodal distribution of motility and cell fate in Dictyostelium discoideum

Pre-starvation amoebae of Dictyostelium discoideum exhibit random movements. Starved cells aggregate by directed movements (chemotaxis) towards cyclic AMP and differentiate into live spores or dead stalk cells. Many differences between presumptive spore and stalk cells precede differentiation. We have examined whether cell motility-related factors are also among them. Cell speeds and localisation of motility-related signalling molecules were monitored by live cell imaging and immunostaining (a) in nutrient medium during growth, (b) immediately following transfer to starvation medium and (c) in nutrient medium that was re-introduced after a brief period of starvation. Cells moved randomly under all three conditions but mean speeds increased following transfer from nutrient medium to starvation medium; the transition occurred within 15 min. The distribution of speeds in starvation medium was bimodal: about 20% of the cells moved significantly faster than the remaining 80%. The motility-related molecules F-actin, PTEN and PI3 kinase were distributed differently in slow and fast cells. Among starved cells, the calcium content of slower cells was lower than that of the faster cells. All differences reverted within 15 min after restoration of the nutrient medium. The slow/fast distinction was missing in Polysphondylium pallidum, a cellular slime mould that lacks the presumptive stalk and spore cell classes, and in the trishanku (triA(center dot)) mutant of D. discoideum, in which the classes exist but are unstable. The transition from growth to starvation triggers a spontaneous and reversible switch in the distribution of D. discoideum cell speeds. Cells whose calcium content is relatively low (known to be presumptive spore cells) move slower than those whose calcium levels are higher (known to be presumptive stalk cells). Slow and fast cells show different distributions of motility-related proteins. The switch is indicative of a bistable mechanism underlying cell motility.

Enhanced Raman Spectroscopy of Molecules Adsorbed on Carbon-Doped TiO2 Obtained from Titanium Carbide: A Visible-Light-Assisted Renewable Substrate

Titanium carbide (TiC) is an electrically conducting material with favorable electrochemical properties. In the present studies, carbon-doped TiO2 (C-TiO2) has been synthesized from TiC particles, as well as TiC films coated on stainless steel substrate via thermal annealing under various conditions. Several C-TiO2 substrates are synthesized by varying experimental, conditions and characterized by UV-visible spectroscopy, photoluminescence, X-ray diffraction and X-ray photoelectron spectroscopic techniques. C-TiO2 in the dry state (in powder form as well as in film form) is subsequently used as a substrate for enhancing Raman signals corresponding to 4-mercaptobenzoic acid and 4-nitrothiophenol by utilizing chemical enhancement based on charge-transfer interactions. Carbon, a nonmetal dopant in TiO2, improves the intensities of Raman signals, compared, to undoped TiO2. Significant dependence of Raman intensity on carbon doping is observed. Ameliorated performance obtained using C-TiO2 is attributed to the presence of surface defects that originate due to carbon as a dopant, which, in turn,, triggers charge transfer between TiO2 and analyte. The C-TiO2 substrates are subsequently regenerated for repetitive use by illuminating an analyte-adsorbed substrate with visible light for a period of 5 h.

Variation of Snowline and Mass Balance of Glaciers of Warwan and Bhut Basins of Western Himalaya Using Remote Sensing Technique

Glaciers are natural reservoirs of fresh water in frozen state and sensitive indicators of climate change. Among all the mountainous glaciated regions, glaciers of Himalayas form one of the largest concentrations of ice outside the Polar Regions. Almost all the major rivers of northern India originate from these glaciers and sustain perennial flow. Therefore, in view of the importance and role of the glaciers in sustaining the life on the Earth, monitoring the health of glaciers is necessary. Glacier's health is monitored in two ways (i) by mapping the change in extent of glaciers (ii) by finding variation in the annual mass balance. This paper has been discussed the later approach for monitoring the health of glaciers of Warwan and Bhut basins. Mass balance of glaciers of these two basins was determined based on the extraction of snow line at the end of ablation season. A series of satellite images of AWiFS sensor were analysed for extraction of snowline on the glaciers for the period of 2005, 2006 and 2007. The snow line at the end of ablation season is used to compute accumulation area ratio (AAR = Accumulation area/Glacier area) for each glacier of basins. An approach based on relationship of AAR to specific mass balance (computed in field) for glaciers of Basapa basin was employed in the present study. Mean of specific mass balance of individual glacier for the year 2005, 2006 and 2007 of Warwan basin was found to be -ve 0.19 m, -ve 0.27 m and -ve 0.2 m respectively. It is 0.05 m, -ve 0.11 m and -ve 0.19 m for Bhut basin. The analysis suggests a loss of 4.3 and 0.83 kmA(3) of glacier in the monitoring period of 3 years for Warwan and Bhut basins respectively. The overall results suggest that the glaciers of Warwan basin and Bhut basins have suffered more loss of ice than gain in the monitoring period of 3 years.

The hazard potential of the western segment of the Makran subduction zone, northern Arabian Sea

Evaluating the hazard potential of the Makran subduction zone requires understanding the previous records of the large earthquakes and tsunamis. We address this problem by searching for earthquake and tectonic proxies along the Makran Coast and linking those observations with the available constraints on historical seismicity and the tell-tale characteristics of sea floor morphology. The earthquake of Mw 8.1 of 1945 and the consequent tsunami that originated on the eastern part of the Makran are the only historically known hazardous events in this region. The seismic status of the western part of the subduction zone outside the rupture area of the 1945 earthquake remains an enigma. The near-shore shallow stratigraphy of the central part of Makran near Chabahar shows evidence of seismically induced liquefaction that we attribute to the distant effects of the 1945 earthquake. The coastal sites further westward around Jask are remarkable for the absence of liquefaction features, at least at the shallow level. Although a negative evidence, this possibly implies that the western part of Makran Coast region may not have been impacted by near-field large earthquakes in the recent past-a fact also supported by the analysis of historical data. On the other hand, the elevated marine terraces on the western Makran and their uplift rates are indicative of comparable degree of long-term tectonic activity, at least around Chabahar. The offshore data suggest occurrences of recently active submarine slumps on the eastern part of the Makran, reflective of shaking events, owing to the great 1945 earthquake. The ocean floor morphologic features on the western segment, on the contrary, are much subdued and the prograding delta lobes on the shelf edge also remain intact. The coast on the western Makran, in general, shows indications of progradation and uplift. The various lines of evidence thus suggest that although the western segment is potentially seismogenic, large earthquakes have not occurred there in the recent past, at least during the last 600 years. The recurrence period of earthquakes may range up to 1,000 years or more, an assessment based on the age of the youngest dated coastal ridge. The long elapsed time points to the fact that the western segment may have accumulated sufficient slip to produce a major earthquake.

Synthesis of zero valent iron nanoparticles and application to removal of arsenic(III) and arsenic(V) from water

Recently nano scale zero valent iron particles (nZVI) have been considered as smart adsorbent for environmental and groundwater remediation. Although several synthetic methods are available for the preparation of nZVI, air stable nZVI are not available for remediation works. Further, challenges demand synthesis of nZVI without stabilizers and capping agents. A modified methodology for the synthesis of air stable nZVI has been developed without any capping agents and characterized by powder X-Ray Diffraction (XRD), Scanning Electron Microscopy Energy-dispersive X-Ray (SEM-EDS), Transmission Electron Microscopy (TEM) and X-Ray Photoelectron Spectroscopy (XPS). The results of the present study suggest that the synthetic nZVI are air-stable over a period of one year and consists of particles of 30-40 nm in diameter. Although a layer of less than 3 am thick oxide/hydroxide is observed by TEM and XPS, it appears to be due to oxidation of outer surface during analysis. Adsorption study has shown that the synthetic nZVI are more effective adsorbent than the commercial nZVI and can remove simultaneously arsenite As-III] and arsenate As-V] from water without prior reduction of As-V to As-III. The removal process is adsorptive rather than precipitative and the removal of As-III is greater than that of As-V.

Microearthquake activity near the Idukki Reservoir, south India: A rare example of renewed triggered seismicity

Earthquakes triggered by artificial reservoirs have been documented for more than seven decades and the processes leading to this phenomenon are fairly well understood. Larger among such earthquakes are known to occur within a few years of reservoir impoundment and usually the activity decreases with time. A documented example of Reservoir Triggered Seismicity (RTS), the Idukki Reservoir in Kerala, south India, impounded in 1975, is an exception wherein the triggered activity has been revived in 2011, nearly 35 years after the initial burst of activity in 1977, two years after the dam was filled. The magnitude of the largest shock in the 2011 sequence exceeded that of the previously documented largest microearthquake. Presence of faults that are close to failure and vulnerable to increase in pore pressure due to reservoir loading or increased rainfall, or a combination of both seems to trigger shocks in this area. The renewed burst of earthquakes after a prolonged period of reduced activity at the Idukki Reservoir is a rare example of RTS. (C) 2012 Elsevier B.V. All rights reserved.

Study of thermal relaxation of Poly (HDDA-co-MMA) by temperature modulated DSC and dielectric spectroscopy

The thermal transitions in the copolymer of 1,6-hexanediol diacrylate (HDDA) and methyl methacrylate (MMA) was investigated to understand its use in microstereolithography. The glass transition temperature and the effect of interaction on this transition process was investigated by means of temperature modulated differential scanning calorimetry (TMDSC). The heat capacities were determined and PHDDA rich phases showed lower heat capacity than PMMA rich phases. The frequency dependence of glass transitions were studied by varying the modulation period of TMDSC and confirmed by dielectric relaxation spectroscopy. Vogel Fulcher Tammann Hesse (VFTH) parameters of homo and copolymers have also been reported.

Performance evaluation of chemistry transport models over India

Using continuous and near-real time measurements of the mass concentrations of black carbon (BC) aerosols near the surface, for a period of 1 year (from January to December 2006) from a network of eight observatories spread over different environments of India, a space-time synthesis is generated. The strong seasonal variations observed, with a winter high and summer low, are attributed to the combined effects of changes in synoptic air mass types, modulated strongly by the atmospheric boundary layer dynamics. Spatial distribution shows much higher BC concentration over the Indo-Gangetic Plain (IGP) than the peninsular Indian stations. These were examined against the simulations using two chemical transport models, GOCART (Goddard Global Ozone Chemistry Aerosol Radiation and Transport) and CHIMERE for the first time over Indian region. Both the model simulations significantly deviated from the measurements at all the stations; more so during the winter and pre-monsoon seasons and over mega cities. However, the CHIMERE model simulations show better agreement compared with the measurements. Notwithstanding this, both the models captured the temporal variations; at seasonal and subseasonal timescales and the natural variabilities (intra-seasonal oscillations) fairly well, especially at the off-equatorial stations. It is hypothesized that an improvement in the atmospheric boundary layer (ABL) parameterization scheme for tropical environment might lead to better results with GOCART.

Euglena sp as a suitable source of lipids for potential use as biofuel and sustainable wastewater treatment

Prolific algal growth in sewage ponds with high organic loads in the tropical regions can provide cost-effective and efficient wastewater treatment and biofuel production. This work examines the ability of Euglena sp. growing in wastewater ponds for biofuel production and treatment of wastewater. The algae were isolated from the sewage treatment plants and were tested for their nutrient removal capability. Compared to other algae, Euglena sp. showed faster growth rates with high biomass density at elevated concentrations of ammonium nitrogen (NH4-N) and organic carbon (C). Profuse growth of these species was observed in untreated wastewaters with a mean specific growth rate (mu) of 0.28 day(-1) and biomass productivities of 132 mg L-1 day(-1). The algae cultured within a short period of 8 days resulted in the 98 % removal of NH4-N, 93 % of total nitrogen 85 % of ortho-phosphate, 66 % of total phosphate and 92 % total organic carbon. Euglenoids achieved a maximum lipid content of 24.6 % (w/w) with a biomass density of 1.24 g L-1 (dry wt.). Fourier transform infrared spectra showed clear transitions in biochemical compositions with increased lipid/protein ratio at the end of the culture. Gas chromatography and mass spectrometry indicated the presence of high contents of palmitic, linolenic and linoleic acids (46, 23 and 22 %, respectively), adding to the biodiesel quality. Good lipid content (comprised quality fatty acids), efficient nutrient uptake and profuse biomass productivity make the Euglena sp. as a viable source for biofuel production in wastewaters.

Antioxidant and oxidative stress parameters in brain of Heteropneustes fossilis under air exposure condition; role of mitochondrial electron transport chain

Many fishes are exposed to air in their natural habitat or during their commercial handling. In natural habitat or during commercial handling, the cat fish Heteropneustes fossilis is exposed to air for > 24 h. Data on its oxidative metabolism in the above condition are not available. Oxidative stress (OS) indices (lipid and protein oxidation), toxic reactive oxygen species (ROS: H2O2) generation, antioxidative status (levels of superoxide dismutase, catalase, glutathione peroxidase and reductase, ascorbic acid and nonprotein sulfhydryl) and activities of electron transport chain (ETC) enzymes (complex I-IV) were investigated in brain tissue of H. fossilis under air exposure condition (0, 3, 6, 12 and 18 h at 25 degrees C). Decreased activities of antioxidant (except catalase) and ETC enzymes (except complex II) with increased H2O2 and OS levels were observed in the tissue under water deprivation condition. Positive correlation was observed for complex II activity and non-protein thiol groups with time period of air exposure. The critical time period to induce OS and to reduce most of the studied antioxidant level in brain was found to be 3-6 h air exposure. The data can be useful to minimize the stress generated during commercial handling of the live fishes those exposed to air in general and H. fossilis in particular. (C) 2013 Elsevier Inc. All rights reserved.

Constraints on Be-10 and Ca-41 distribution in the early solar system from Al-26 and Be-10 studies of Efremovka CAIs

Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live Ca-41, were studied by ion microprobe for their Al-26-Mg-26 and Be-10-B-10 systematic in order to better understand the origin of Be-10. The high precision Al-Mg data and the inferred Al-26/Al-27 values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting-crystallization events. The initial Be-10/Be-9 ratios and delta B-10 values defined by the Be-10 isochrons for the three Efremovka CAIs are similar within errors. The CAI Be-10 abundance in published data underscores the large range for initial Be-10/Be-9 ratios. This is contrary to the relatively small range of Al-26/Al-27 variations in CAIs around the canonical ratio. Two models that could explain the origin of this large Be-10/Be-9 range are assessed from the collateral variations predicted for the initial delta B-10 values: (i) closed system decay of Be-10 from a ``canonical'' Be-10/Be-9 ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of Be-10 in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for Be-10 production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for Ca-41 because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. Be-10 production by irradiation from solar energetic particles requires high Ca-41 abundance in early solar system, however, this is not observed in CAIs. (C) 2013 Elsevier B.V. All rights reserved.