Formation of silver nanorod arrays in an anodised aluminium oxide membrane

A highly ordered silver nanorod array (AgNRs) with a diameter of 90?nm has been prepared by chemical reduction from silver nitrate in a porous anodic aluminium oxide (AAO) membrane. The AAO membrane was fabricated electrochemically in an oxalic acid solution via a one-step anodisation process, followed by the growth of silver NR in the long-range ordered nanochannels of the AAO membrane via chemical reduction. The morphologies of AAO membrane and AgNRs with periodic rows of air-pockets encapsulated in the AAO membrane have been investigated using TEM. The crystalline structure and chemical composition have been confirmed by XRD, TEM and EDX techniques. The process, which has three stages, namely, (1) anodising of aluminium foil to form a mesoporous membrane, (2) adsorption of metal ions, then (3) chemical reduction of the adsorbed metal ions to form the nanorod array of AgNRs in the pores of AAO membrane, has not, to the authors’ knowledge, been reported to date.     

Nutrient content,in vitro ruminal fermentation characteristics and methane reduction potential of tropical tannin‐containing leaves

BACKGROUND: Plant tannins as rumen modifiers are better than chemicals or antibiotic‐based modifiers since these compounds are natural products which are environmentally friendly and therefore have a better acceptance with regard to feed safety issues. Tropical plants containing phenols such as tannins were found to suppress or eliminate protozoa from the rumen and reduce methane and ammonia production. The screening of these plants is an important step in the identification of new compounds and feed additives which might contribute to mitigate rumen methanogenesis. The present study was carried out to determine the efficacy of tannins from tropical tree leaves for their methane reduction properties. RESULTS: Activity of tannins, as represented by the increase in gas volume with the addition of polyethylene glycol (PEG)‐6000 as a tannin binder (tannin bioassay) was highest in Ficus bengalensis (555%), followed by Azardirachta indica (78.5%). PEG addition did not alter (P > 0.05) methane percentage in Ficus racemosa, Glyricidia maculata, Leucena leucocephala, Morus alba and Semaroba glauca, confirming that tannins in these samples did not affect methanogenesis. The increase (P < 0.05) in protozoa population with PEG was maximal in Ficus religiosa (50), followed by Moringa oleifera (31.2), Azardirachta indica (29.9) and Semaroba glauca (27.5). There was no change (P > 0.05) in the protozoa population in Autocarpus integrifolia, Ficus bengalensis, Jatropha curcus, Morus alba and Sesbania grandiflora, demonstrating that methane reduction observed in these samples per se was not due to defaunation effect of the tannin. The increase in total volatile fatty acid concentration in samples with PEG ranged from 0.6% to > 70%. The highest increase (%) in NH₃‐N was recorded in Azardirachta indica (67.4), followed by Ficus mysoriensis (35.7) and Semaroba glauca (32.6) leaves, reflecting strong protein binding properties of tannin. CONCLUSION: The results of our study established that in vitro methanogenesis was not essentially related to the density of protozoa population. Tropical tree leaves containing tannins such as Autocarpus integrifolia, Jatropha curcus and Sesbania grandiflora have the potential to suppress methanogenesis. Therefore tannins contained in these plants could be of interest in the development of new additives in ruminant nutrition. Copyright © 2012 Society of Chemical Industry     

Comparison of electronic structure of as grown and solar grade silicon samples

A comparison of the electronic structure of two different types of silicon materials viz., (i) as grown silicon and (ii) solar silicon has been carried out utilizing maximum entropy method and pair distribution function using powder X-ray data sets. The precise electron density maps have been elucidated for the two samples. The covalent nature of the bonding between atoms in both the samples is found to be well pronounced and clearly seen from the electron density maps. The electron densities at the middle of the Si-Si bond are found to be 0.47 and 0.45 e/ų for as grown silicon and solar silicon respectively. In this work, the local structural information has also been obtained by analyzing the atomic pair distribution functions of these two samples.     

Synthesis and morphological control of europium doped cadmium sulphide nanocrystals

Europium doped cadmium sulphide (Cd(0.98)Eu(0.2)S) nanostructures were synthesised by chemical co-precipitation method using ethylene glycol (EG) and deionized water (Eu:CdS-1), and isopropyl alcohol (IPA) and deionized water (Eu:CdS-2) as mixed solvents. It has been found that the nanostructure of the europium doped CdS can be controlled by simply varying the mixed solvent system. Powder XRD pattern reveals the formation of hexagonal (wurtzite) and cubic (zinc blende) structure for Eu:CdS-1, and Eu:CdS-2, respectively. The crystallite size of the sample prepared using IPA and deionized water was measured to be 2.64 nm which is much smaller than that of the sample prepared using EG and deionized water as mixed solvent (3.65 nm). Morphology of the materials can also be changed from flower shaped crystals to paddy like structures by varying the mixed solvents. Band gap values of Eu3+ doped CdS nanocrystals synthesized from two different solvents were estimated using UV-reflectance spectra. The size and crystallinity of the samples were confirmed by HRTEM and SAED analysis. A significant change in the PL emission of the CdS nanocrystals was observed for the europium doped CdS which is mainly due to the presence of EU3+ ions which also play a significant role in the energy transfer process. It was also observed that the shift in the emission and efficiency depends on size and shape of the synthesised nanoparticles.     

Synthesis and evaluation of trimethylolpropane triacrylate crosslinked superabsorbent polymers for conserving water and fertilizers

A series of superabsorbent polymers (SAP) were synthesized by free radical thermal copolymerization of acrylic acid and N‐isopropyl acrylamide monomers using trimethylolpropane triacrylate as crosslinker. They were characterized by FT‐IR and thermal stability (TGA/DTG), and evaluated for their water and fertilizer uptake and release characteristics under different crosslinker levels, temperature, pressure, and pH. The observed maximum absorption of water by the SAP was 1130 g/g of polymer. The release was modeled which showed a non‐Fickian mechanism. The water uptake of SAP was correlated with the average molecular weight between the crosslinks and crosslink density. Analysis of the weight loss data from TG in air revealed a zero order kinetics for the initial degradation step with an activation energy (AE) of 70.8 kJ/mol. The AEs for water uptake and release for thermal degradation were also determined through Arrhenius plots. The results inferred that the synthesized SAP can be exploited for commercial agricultural applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Combined effect of injection timing,EGR and injection pressure in reducing the NOx emission of a biodiesel blend

In this study, an attempt was made to reduce the higher oxides of nitrogen (NO_x) emission of a crude rice bran oil methyl ester (CRBME) blend through modification of combustion process by retarding fuel injection timing and exhaust gas recirculation at an increased fuel injection pressure. At modified condition, delay period and peak pressure of CRBME blend were lower than those at normal condition. The occurrence of maximum heat release rate retarded with a higher magnitude when compared with normal condition. Experimental results show that as a result of combustion modification, NO_x and carbon monoxide emissions were reduced significantly with marginal increase in smoke density. Brake thermal efficiency and unburnt hydrocarbon emissions of the engine were increased significantly as a result of this modification process. This investigation shows that the NO_x emission of a biodiesel blend can be reduced with less sacrifice on smoke density and increase in the brake thermal efficiency by modifying the combustion process.     

Human-Centric Composite-Quality Modeling and Assessment for Virtual Desktop Clouds

There are several motivations, such as mobility, cost, and security, that are behind the trend of traditional desktop users transitioning to thin-client-based virtual desktop clouds (VDCs). Such a trend has led to the rising importance of human-centric performance modeling and assessment within user communities that are increasingly making use of desktop virtualization. In this paper, we present a novel reference architecture and its easily deployable implementation for modeling and assessing objective user quality of experience (QoE) in VDCs. This architecture eliminates the need for expensive, time-consuming subjective testing and incorporates finite-state machine representations for user workload generation. It also incorporates slow-motion benchmarking with deep-packet inspection of application task performance affected by QoS variations. In this way, a "composite-quality" metric model of user QoE can be derived. We show how this metric can be customized to a particular user group profile with different application sets and can be used to a) identify dominant performance indicators and troubleshoot bottlenecks and b) obtain both absolute and relative objective user QoE measurements needed for pertinent selection of thin-client encoding configurations in VDCs. We validate our composite-quality modeling and assessment methodology by using subjective and objective user QoE measurements in a real-world VDC called VDPilot, which uses RDP and PCoIP thin-client protocols. In our case study, actual users are present in virtual classrooms within a regional federated university system.     

Floquet instability of a gravity modulated Rayleigh–Benard problem in an anisotropic porous medium

This work deals with the effect of gravity modulation on the onset of convection in a horizontal porous layer subjected to an adverse temperature gradient. Low amplitude gravity modulations are considered. The analysis is linear and specific attention is paid to the boundary effects of Brinkman's model and anisotropies of the porous medium in permeability and thermal conductivity. A Floquet analysis is applied and critical values of the parameters are found analytically using stability charts. The emergence of instability through the synchronous and subharmonic modes, transition between them and their dependence discussed for physically realistic values of control parameters. The findings of this analysis may be useful in controlling convective plumes during fabrication which develop into freckles in the ground grown crystals.     

An experimental investigation on DI diesel engine with hydrogen fuel

The internal combustion engines have already become an indispensable and integral part of our present day life style, particularly in the transportation and agricultural sectors [Nagalingam B. Properties of hydrogen. In: Proceedings of the summer school of hydrogen energy, IIT Madras, 1984]. Unfortunately the survival of these engines has, of late, been threatened due to the problems of fuel crisis and environmental pollution. Therefore, to sustain the present growth rate of civilization, a nondepletable, clean fuel must be expeditiously sought. Hydrogen exactly caters to the specified needs. Hydrogen, even though “renewable” and “clean burning”, does give rise to some undesirable combustion problems in an engine operation, such as backfire, pre-ignition, knocking and rapid rate of pressure rise [Srinivasa Rao P. Utilization of hydrogen in a dual fueled engine. In: Proceedings of the summer school of hydrogen energy, IIT Madras, 1984; Siebers DL. Hydrogen combustion under diesel engine conditions. Hydrogen Energy 1998;23:363–71]. The present investigation compares the performance and emission characteristics of a DI diesel engine with gaseous hydrogen as a fuel inducted by means of carburation technique and timed port injection technique (TPI) along with diesel as a source of ignition [Swain N, Design and testing of dedicated hydrogen-fueled engine. SAE 961077, 1996]. In the present study the specific energy consumption, NO_x emission and the exhaust gas temperature increased by 6%, 8% and 14%, respectively, and brake thermal efficiency and smoke level reduced by 5% and 8%, respectively, using carburation technique compared to baseline diesel. But in the TPI technique, the specific energy consumption, exhaust gas temperature and smoke level reduced by 15%, 45% and 18%, respectively. The brake thermal efficiency and NO_x increased by 17% and 34%, respectively, compared to baseline diesel. The emissions such as HC, CO, and CO₂ is very low in both carburation and TPI techniques compared baseline diesel.