High precision Mg isotope measurements of meteoritic samples by secondary ion mass spectrometry

The possibility of establishing an accurate relative chronology of the early solar system events based on the decay of short-lived Al-26 to Mg-26 (half-life of 0.72 Myr) depends on the level of homogeneity (or heterogeneity) of Al-26 and Mg isotopes. However, this level is difficult. to constrain precisely because of the very high precision needed for the determination of isotopic ratios, typically of +/- 5 ppm. In this study, we report for the first time a detailed analytical protocol developed for high precision in situ Mg isotopic measurements ((25)mg/(24)mg and (26)mg/Mg-24 ratios, as well as Mg-26 excess) by MC-SIMS. As the data reduction process is critical for both accuracy and precision of the final isotopic results, factors such as the Faraday cup (FC) background drift and matrix effects on instrumental fractionation have been investigated. Indeed these instrumental effects impacting the measured Mg-isotope ratios can be as large or larger than the variations we are looking for to constrain the initial distribution of Al-26 and Mg isotopes in the early solar system. Our results show that they definitely are limiting factors regarding the precision of Mg isotopic compositions, and that an under- or over-correction of both FC background instabilities and instrumental isotopic fractionation leads to important bias on delta Mg-25, delta(26)mg and Delta Mg-26 values (for example, olivines not corrected for FC background drifts display Delta Mg-26 values that can differ by as much as 10 ppm from the truly corrected value). The new data reduction process described here can then be applied to meteoritic samples (components of chondritic meteorites for instance) to accurately establish their relative chronology of formation.

Tunability of monodispersed intermetallic AuCu nanoparticles through understanding of reaction pathways

Synthesis of size selective monodispersed nanoparticles particularly intermetallic with well-defined compositions represents a challenge. This paper presents a way for the synthesis of intermetallic AuCu nanoparticles as a model system. We show that reduction of Au and Cu precursors is sensitive to the ratio of total molar concentrations of surfactant to metal precursors. A careful design of experiments to understand the kinetics of the reduction process reveals initial formation of seed nanoparticles of pure Au. Reduction of Cu occurs on the surface of the seed followed by diffusion to yield AuCu. This understanding allows us to develop a two step synthesis where the precise size controlled seed of Au nanoparticles produced in the first step is used in the second step reaction mixture as an Au precursor to allow deposition and interdiffusion of Cu that yields size selected AuCu intermetallics of sub 10 nm sizes.

Electrochemical deposition of manganese oxide-phosphate-reduced graphene oxide composite and electrocatalysis of the oxygen evolution reaction

A composite of manganese oxide and reduced graphene oxide (rGO) is prepared in a single step electrochemical reduction process in a phosphate buffer solution for studying as an electrocatalyst for the oxygen evolution reaction (OER). The novel composite catalyst, namely, MnOx-Pi-rGO, is electrodeposited from a suspension of graphene oxide (GO) in a neutral phosphate buffer solution containing KMnO4. The manganese oxide incorporates phosphate ions and deposits on the rGO sheet, which in turn is formed on the substrate electrode by electrochemical reduction of GO in the suspension. The OER is studied with the MnOx-Pi-rGO catalyst in a neutral phosphate electrolyte by linear sweep voltammetry. The results indicate a positive influence of rGO in the catalyst. By varying the ratio of KMnO4 and GO in the deposition medium and performing linear sweep voltammetry for the OER, the optimum composition of the deposition medium is obtained as 20 mM KMnO4 + 6.5% GO in 0.1 M phosphate buffer solution of pH 7. Under identical conditions, the MnOx-Pi-rGO catalyst exhibits 6.2 mA cm(-2) OER current against 2.9 mA cm(-2) by MnOx-Pi catalyst at 2.05 V in neutral phosphate solution. The Tafel slopes measured for OER at MnOx-Pi and MnOx-Pi-rGO are similar in magnitude at about 0.180 V decade(-1). The high Tafel slopes are attributed to partial dissolution of the catalyst during oxygen evolution. The O-2 evolved at the catalyst is measured by the water displacement method and the positive role of rGO on catalytic activity of MnOx-Pi is demonstrated.

Metal and Alloy Nanoparticles by Amine-Borane Reduction of Metal Salts by Solid-Phase Synthesis: Atom Economy and Green Process

A new solid state synthetic route has been developed toward metal and bimetallic alloy nanoparticles from metal salts employing amine-boranes, as the reducing agent. During the reduction, amine-borane plays a dual role: acts as a reducing agent and reduces the metal salts to their elemental form and simultaneously generates a stabilizing agent in situ which controls the growth of the particles and stabilizes them in the nanosize regime. Employing different amine-boranes with differing reducing ability (ammonia borane (AB), dimethylamine borane (DMAB), and triethylamine borane (TMAB)) was found to have a profound effect on the particle size and the size distribution. Usage of AB as the reducing agent provided the smallest possible size with best size distribution. Employment of TMAB also afforded similar results; however, when DMAB was used as the reducing agent it resulted in larger sized nanoparticles that are polydisperse too. In the AB mediated reduction, BNHx polymer generated in situ acts as a capping agent whereas, the complexing amine of the other amine-boranes (DMAB and TMAB) play the same role. Employing the solid state route described herein, monometallic Au, Ag, Cu, Pd, and Ir and bimetallic CuAg and CuAu alloy nanoparticles of <10 nm were successfully prepared. Nucleation and growth processes that control the size and the size distribution of the resulting nanoparticles have been elucidated in these systems.

Calciothermic reduction of TiO2: A diagrammatic assessment of the thermodynamic limit of deoxidation

Calciothermic reduction of TiO2 provides a potentially low-cost route to titanium production. Presented in this article is a suitably designed diagram, useful for assessing the degree of reduction of TiO2 and residual oxygen contamination in metal as a function of reduction temperature and other process parameters. The oxygen chemical potential diagram à la Ellingham-Richardson-Jeffes is useful for visualization of the thermodynamics of reduction reactions at high temperatures. Although traditionally the diagram depicts oxygen potentials corresponding to the oxidation of different metals to their corresponding oxides or of lower oxides to higher oxides, oxygen potentials associated with solution phases at constant composition can be readily superimposed. The usefulness of the diagram for an insightful analysis of calciothermic reduction, either direct or through an electrochemical process, is discussed. Identified are possible process variations, modeling and optimization strategies.

Highly biocompatible and water-dispersible, amine functionalized magnetite nanoparticles, prepared by a low temperature, air-assisted polyol process: a new platform for bio-separation and diagnostics

A low temperature polyol process, based on glycolaldehyde mediated partial reduction of FeCl3 center dot 6H(2)O at 120 degrees C in the presence of sodium acetate as an alkali source and 2,2'-(ethylenedioxy)-bis-(ethylamine) as an electrostatic stabilizer has been used for the gram-scale preparation of biocompatible, water-dispersible, amine functionalized magnetite nanoparticles (MNPs) with an average diameter of 6 +/- 0.75 nm. With a reasonably high magnetization (37.8 e.m.u.) and amine groups on the outer surface of the nanoparticles, we demonstrated the magnetic separation and concentration implications of these ultrasmall particles in immunoassay. MRI studies indicated that these nanoparticles had the desired relaxivity for T-2 contrast enhancement in vivo. In vitro biocompatibility, cell uptake and MR imaging studies established that these nanoparticles were safe in clinical dosages and by virtue of their ultrasmall sizes and positively charged surfaces could be easily internalized by cancer cells. All these positive attributes make these functional nanoparticles a promising platform for further in vitro and in vivo evaluations.

The process of technological innovations in small enterprises: the Indian way

This paper probes how two small foundries in Belgaum, Karnataka State, India, have achieved technological innovations successfully based on their technological capability and customer needs, enabling them to sail through the competitive environment. This study brought out that technically qualified entrepreneurs of both the foundries have carried out technological innovations, mainly due to their self-motivation and self-efforts. Changing product designs, as desired or directed by the customers, cost reduction, quality improvement and import substitution through reverse engineering are the characteristics of these technological innovations. These incremental innovations have enabled the entrepreneurs of the two foundries to enhance competitiveness, grow in the domestic market and penetrate the international market and grow in size over time.

The process of technological innovations in small enterprises: the Indian way

This paper probes how two small foundries in Belgaum, Karnataka State, India, have achieved technological innovations successfully based on their technological capability and customer needs, enabling them to sail through the competitive environment. This study brought out that technically qualified entrepreneurs of both the foundries have carried out technological innovations, mainly due to their self-motivation and self-efforts. Changing product designs, as desired or directed by the customers, cost reduction, quality improvement and import substitution through reverse engineering are the characteristics of these technological innovations. These incremental innovations have enabled the entrepreneurs of the two foundries to enhance competitiveness, grow in the domestic market and penetrate the international market and grow in size over time.

Evolution of polyandry by reduction in progeny number variance in structured populations

When there is a variation in the quality of males in a population, multiple mating can lead to an increase in the genetic fitness of a female by reducing the variance of the progeny number. The extent of selective advantage obtainable by this process is investigated for a population subdivided into structured demes. It is seen that for a wide range of model parameters (deme size, distribution of male quality, local resource level), multiple mating leads to a considerable increase in the fitness. Frequency-dependent selection or a stable coexistence between polyandry and monandry can also result when the possible costs involved in multiple mating are taken into account.

An efficient reduction algorithm for computation of interconnect delay variability for statistical timing analysis in clock tree planning

In this paper, we propose a novel and efficient algorithm for modelling sub-65 nm clock interconnect-networks in the presence of process variation. We develop a method for delay analysis of interconnects considering the impact of Gaussian metal process variations. The resistance and capacitance of a distributed RC line are expressed as correlated Gaussian random variables which are then used to compute the standard deviation of delay Probability Distribution Function (PDF) at all nodes in the interconnect network. Main objective is to find delay PDF at a cheaper cost. Convergence of this approach is in probability distribution but not in mean of delay. We validate our approach against SPICE based Monte Carlo simulations while the current method entails significantly lower computational cost.

Plasma diagnostics of the high pressure oxygen-sputtering process

The characteristics of the high pressure oxygen-sputtering plasma in the pressure range 0.8–2.4 mbar have been studied using the Langmuir probe technique. The variation in plasma parameters such as positive ion density, electron density, mean electron energy and floating potential with pressure and temperature has been investigated. It has been observed that the positive ion density increases at high substrate temperatures whereas the negative ion density decreases. The study of the variation in mean electron energy and floating potential also indicated the possibility that the number of negative ions is less when the substrates are at elevated temperatures. Since the negative ions are supposed to cause re-sputtering and make the films off-stoichiometric, the reduction in the negative ion density as observed at elevated substrate temperatures is better suited for depositing stoichiometric YBa2Cu3O7−δ superconducting thin films.

Kinetic evolution studies of silver nanoparticles in a bio-based green synthesis process

Silver nanoparticles are being extensively studied due to their widespread applications and unique properties. In the present study, the growth kinetics of silver nanoparticles as synthesized on reduction of silver nitrate solution by aqueous extract of Azadirachta indica leaves was investigated. The formation of silver nanoparticles was preliminarily monitored by measuring the absorption maxima at different time intervals after adding the reducing agent to the silver salt solution (0.5, 1, 1.5, 2, 2.5, 3, 3.5 and 4 h). At different time points characterization studies were conducted using X-ray diffraction studies, FT-IR techniques, zeta potential studies and transmission electron microscopy. The total available silver in the reaction medium was determined at different durations using ICP-OES. The changes in reduction potential in the medium were also monitored using potentiometric analysis. The results confirm a definite change in the medium pertaining to formation of the stable nanoparticles after 2 h, and a significant increase in the agglomeration tendency after 4 h of interaction. The growth kinetic data of the nanoparticles till 3.5 h was found to fit the LSW model confirming diffusion limited growth. (C) 2011 Elsevier B.V. All rights reserved.

Development of a clean bioelectrochemical process for leaching of ocean manganese nodules

Through the application of negative reduction potential significant reduction of manganic and iron oxides in the ocean manganese nodules can be achieved, liberating the occluded copper, nickel and cobalt for easy dissolution in an acid medium. Electroleaching and electrobioleaching of ocean manganese nodules in the presence of Thiobacillus ferrooxidans and Thiobacillus thiooxidans at the above negative applied dc potentials resulted in significant dissolution of copper, nickel and cobalt in 1 M H2SO4. The role of galvanic interactions in the bioleaching of ocean manganese nodules in the presence of T thiooxidans is also discussed, (C) 2002 Published by Elsevier Science Ltd.

Pulsed plasma treatment for NOx reduction from filtered/unfiltered stationary diesel engine exhaust

A detailed study on the removal of oxides of nitrogen (NOx) from the filtered/unfiltered exhaust of a stationary diesel engine was carried out using non-thermal plasma (pulsed electrical discharge plasma) process and cascaded processes namely plasma- adsorbent and plasma-catalyst processes. The superior performance of discharge plasma with regard to NOx removal, energy consumption and formation of by-products in unfiltered exhaust environment is identified. In the cascaded plasma-adsorbent process, the plasma was cascaded with adsorbents (MS13X/Activated alumina/Activated charcoal). The cascaded process treating unfiltered exhaust exhibits a very high NOx removal compared to the individual processes and further, the cascaded process gives almost the same NOx removal efficiency irrespective of type of adsorbent used. In the cascaded plasma- catalyst process, the plasma was cascaded with activated alumina catalyst at high temperature. The synergy effect and improved performance of the cascaded process are explained. Further, experiments were conducted at room temperature as well as at higher temperatures.

Corona treatment for NOx reduction from stationary diesel engine exhaust: Impact of nature of energization and exhaust composition

A detailed study on the removal of oxides of nitrogen (NOx) from the exhaust of a stationary diesel engine was carried out using non-thermal plasma (dielectric barrier discharge) process. The objective of the study was to explore the effect of different voltage energizations and exhaust composition on the NOx removal process. Three types of voltage energizations, namely AC, DC and Pulse were examined. Due to the ease of generation of high voltage AC/DC electrical discharges from automobile/Vehicular battery supply for possible retrofitting in exhaust cleaning circuit, it was found relevant to investigate individual energisation cases in detail for NOx removal. AC and Pulse energisations exhibit a superior NOx removal efficiency compared to DC energisation. However,Pulse energisation is found to be more energy efficient. Experiments were further carried out with filtered/ unfiltered (raw) exhaust under pulse energisations. The results were discussed with regard to NOx removal, energy consumption and formation of by-products.