Catalytic performance of highly dispersed Ni/TiO2 for dry and steam reforming of methane

The present study reports a sonochemical-assisted synthesis of a highly active and coke resistant Ni/TiO2 catalyst for dry and steam reforming of methane. The catalyst was characterized using XRD, TEM, XPS, BET analyzer and TGA/DTA techniques. The TEM analysis showed that Ni nanoparticles were uniformly dispersed on TiO2 surface with a narrow size distribution. The catalyst prepared via this approach exhibited excellent activity and stability for both the reactions compared to the reference catalyst prepared from the conventional wet impregnation method. For dry reforming, 86% CH4 conversion and 84% CO2 conversion was obtained at 700 degrees C. Nearly 92% CH4 conversion and 77% CO selectivity was observed under a H2O/CH4 ratio of 1.2 at 700 degrees C for the steam reforming reaction. In particular, the present catalyst is extremely active and resistant to coke formation for steam reforming at low steam/carbon ratios. There is no significant modification of Ni particles size and no coke deposition, even after a long term reaction, demonstrating its potential applicability as an industrial reformate for hydrogen production. The detailed kinetic studies have been presented for steam reforming and the mechanism involving Langmuir-Hinshelwood kinetics with adsorptive dissociation of CH4 as a rate determining step has been used to correlate the experimental data.

Characterising weather patterns associated with fire in a seasonally dry tropical forest in southern India

Anthropogenic fires in seasonally dry tropical forests are a regular occurrence during the dry season. Forest managers in India, who presently follow a fire suppression policy in such forests, would benefit from a system of assessing the potential risk to fire on a particular day. We examined the relationship between weather variables (seasonal rainfall, relative humidity, temperature) and days of fire during the dry seasons of 2004-2010, based on MODIS fire incident data in the seasonally dry tropical forests of Mudumalai in the Western Ghats, southern India. Logistic regression analysis showed that high probabilities of a fire day, indicating successful ignition of litter and grass fuel on the forest floor, were associated with low levels of early dry season rainfall, low daily average relative humidity and high daily average temperatures. These weather conditions are representative of low moisture levels of fine fuels, suggesting that the occurrence of fire is moderated by environmental conditions that reduce the flammability of fine fuels in the dry tropics. We propose a quantitative framework for assessing risk of a fire day to assist forest managers in anticipating fire occurrences in this seasonally dry tropical forest, and possibly for those across South Asia.

Cryptic species and Miocene diversification of Palaearctic naked-toed geckos (Squamata: Gekkonidae) in the Indian dry zone

We sampled Palaearctic naked-toed geckos from across their range in India and used two mitochondrial and two nuclear genes to reconstruct relationships within a global phylogeny. Published sequences of Peninsular Indian Hemidactylus allow us to contrast these two groups in dating analyses - providing insights into the history of the Indian dry zone. Palaearctic naked-toed geckos first moved onto the Indian Plate in the Oligocene, with higher-level diversification probably linked to collision of the Indian and Eurasian plates, and subsequent dispersal into-India and diversification with increasing Miocene aridity. An independent gekkonid radiation with species in the dry zone, Hemidactylus diversified during the same period in Peninsular India. Our results demonstrate that dry zone taxa across India may date back to at least the Miocene, with a potential historical climatic barrier between the Indus and Peninsular Indian Divisions. `Cyrtopodion' aravallense is revealed to be a complex with seven genetically and environmentally divergent lineages that began diversifying in the late Miocene, congruent with increased aridity in north-western India. This discovery of cryptic diversity in the Indian dry zone represents the first terrestrial vertebrate radiation from north-western central India and highlights how little we understand of the regions' biodiversity, emphasizing the need for systematic geographic sampling and multiline evidence to reveal true patterns of diversity. The ancestor of `Cyrtopodion' aravallense came into the nascent Indian dry zone in the Miocene and has since diversified, potentially in the absence of any sympatric scansorial rupicolous geckos. Cyrtopodion scabrum represents a unique case of commensalism and shows phylogeographic structure in its presumed native range. The taxonomic implications of our study include a number of undescribed species, recognition of `Cyrtopodion' as a distinct lineage and the non-monophyly of Altiphylax.

Fire and soil temperatures during controlled burns in seasonally dry tropical forests of southern India

Fire and soil temperatures were measured during controlled burns conducted by the Forest Department at two seasonally dry tropical forest sites in southern India, and their relationships with fuel load, fuel moisture and weather variables assessed using stepwise regression. Fire temperatures at the ground level varied between 79 degrees C and 760 degrees C, with higher temperatures recorded at high fuel loads and ambient temperatures, whereas lower temperatures were recorded at high relative humidity. Fire temperatures did not vary with fuel moisture or wind speed. Soil temperatures varied between <79 degrees C and 302 degrees C and were positively correlated with ground-level fire temperatures. Results from the study imply that fuel loads in forested areas have to be reduced to ensure low intensity fires in the dry season. Low fire temperatures would ensure lower mortality of above-ground saplings and minimal damage to root stocks of tree species that would maintain the regenerative capacity of a tropical dry forest subject to dry season wildfires.

PECVD grown SiC cantilevers with Dry and Wet Release

Cantilevers made out of PECVD grown SiC films are reported here. The cantilevers were realized in two different methods isotropic etch (Dry release) and combination of wet etch and critical point dry release. The dry release process for Silicon isotropic etch results in excellent etch selectivity against SiC, to provide released structures. The optimized wet release process is able to overcome stiction issues to provide excellent SiC cantilevers.

Regeneration of Juvenile Woody Plants after Fire in a Seasonally Dry Tropical Forest of Southern India

Woody tree species in seasonally dry tropical forests are known to have traits that help them to recover from recurring disturbances such as fire. Two such traits are resprouting and rapid post-fire growth. We compared survival and growth rates of regenerating small-sized individuals (juveniles) of woody tree species after dry season fire (February-March) at eight adjacent pairs of burnt and unburnt transects in a seasonally dry tropical forest in southern India. Juveniles were monitored at 3-mo intervals between August 2009 and August 2010. High juvenile survivorship (>95%) was observed in both burnt and unburnt areas. Growth rates of juveniles, analyzed at the community level as well as for a few species individually (especially fast-growing ones), were distinctly higher in burnt areas compared to unburnt areas after a fire event, particularly during the pre-monsoon season immediately after a fire. Rapid growth by juveniles soon after a fire may be due to lowered competition from other vegetative forms such as grasses, possibly aided by the availability of resources stored belowground. Such an adaptation would allow a juvenile bank to be retained in the understory of a dry forest, from where individuals can grow to a possible fire-tolerant size during favorable conditions.

Nest site characterization of sympatric hornbills in a tropical dry forest

Hornbills, among the largest and most threatened tropical frugivores, provide important seed dispersal services. Hornbill nest site characteristics are known primarily from wet tropical forests. Nests of the Indian grey hornbill Ocyceros birostris and Oriental pied hornbill Anthracoceros albirostris were characterized in a tropical dry forest. Despite A. albirostris being twice the size of O. birostris, few of the nest cavity attributes were different. A. albirostris nests were surrounded by higher proportion of mixed forest and lower sal forest compared to O. birostris. In this landscape, the larger A. albirostris may prefer to nest in sites with more food plants compared to the smaller O. birostris.

Dry sliding wear of epoxy/cenosphere syntactic foams

Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 wt% fly ash cenosphere is reported based on response surface methodology. Empirical models are constructed and validated based on analysis of variance. Results show that syntactic foams have higher wear resistance than the matrix resin. Among the parameters studied, the applied normal load (F) had a prominent effect on wear rate, specific wear rate (w(s)) and coefficient of friction (mu). With increasing F, the wear rate increased, whereas ws and mu decreased. With increase in filler content, the wear rate and w(s) decreased, while the mu increased. With increase in sliding velocity as well as sliding distance, the wear rate and ws show decreasing trends. Microscopy revealed broken cenospheres forming debris and extensive deformation marks on the wear surface. (C) 2015 Elsevier Ltd. All rights reserved.