Indian Institute of Technology Guwahati

About: Indian Institute of Technology Guwahati is a education organization based out in Guwahati, Assam, India. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 6933 authors who have published 17102 publications receiving 257351 citations.

Starch-mediated shape-selective synthesis of Au nanoparticles with tunable longitudinal plasmon resonance.

Abstract: We report the synthesis ofAu nanoparticles, with tunable longitudinal plasmon band and shape selectivity, mediated by starch in the presence of ultrasonic waves. The synthesis was carried out by reduction of HAuCl4, at various concentrations, using H2O2 as the reducing agent. When the reactions were carried out in the absence of ultrasonic waves, there was no occurrence of the longitudinal resonance band, while the transverse plasmon resonance band shifted toward a higher wavelength. Transmission electron microscopic measurements revealed an increase in particle sizes with increasing higher initial HAuCl4 concentration. On the other hand, in the presence of ultrasonic waves, as the initial concentration of HAuCl4 was increased, while the transverse plasmon resonance band remained the same, the longitudinal plasmon resonance band increasingly shifted toward a higher wavelength. Transmission electron microscopic measurements revealed the change in shape from spherical to triangular to hexagonal particles with increasing initial HAuC14 concentration. We also report that the starch-stabilized nanoparticles could be precipitated from the solution by a starch digesting enzyme which also binds with the particles resulting in its precipitation.

Copper(I)-catalyzed synthesis of substituted 2-mercapto benzimidazoles.

Abstract: An efficient method for the preparation of various substituted 2-mercapto benzimidazoles from their corresponding thioureas has been developed. S-Alkylation of thioureas followed by Cu-catalyzed intramolecular N-arylation furnished substituted 2-mercapto benzimidazoles in high yields and short reaction times. Furthermore, 2-mercapto benzimidazoles substituted with a p-methoxybenzyl group allowed access to benzimidazole thiones.

Effectiveness of Some Strengthening Options for Masonry-Infilled RC Frames with Open First Story

Abstract: Strengthening of masonry-infilled reinforced concrete (RC) frame buildings with an open first story is needed because of the inherent irregularity in such buildings resulting in their poor performance as observed during several past earthquakes. In the present study, several strengthening schemes were evaluated for their effectiveness in improving the performance of such buildings, based on nonlinear analyses of typical RC frames. Instead of using predetermined multiplying factors for designing the first-story members for higher forces as recommended in some national codes, a rational method was developed for the calculation of the required increase in strength of open first-story columns. Other strengthening schemes studied were providing additional columns, diagonal bracings, and lateral buttresses in the open first story. Code methods were found to increase only lateral strength (and not the ductility) of such frames; whereas, some of the alternate schemes studied were found to improve both lateral strength and ductility for improved seismic performance.

Significance of PM2.5 Air Quality at the Indian Capital

Abstract: In New Delhi, the capital city of India, concentrations of regulated air pollutants often exceed the Indian national ambient air quality standards (INAAQS). As the sources of these pollutants differ, it is of utmost priority to understand the most dangerous air pollutant to formulate better control strategies in the city. In this study, regulated air pollutant concentrations in New Delhi during 2011 to 2014 were collected. Compared to other pollutants, PM2.5 concentrations exceeded the INAAQS quite often. While PM2.5 exceeded INAAQS during 85% of the days, NO2, O3, CO and SO2 exceeded only on 37, 14, 11 and 0% of the days, respectively. Using air quality index approach, the most dominant pollutant was identified as PM2.5, for 75 to 90% of the days. However, a seasonal variation in the percentage dominance of PM2.5 was observed. For example, PM2.5 was dominant during 95% of the winter and 68% of monsoon days. In addition to absolute concentrations, pollutants can also be ranked by studying their associated short term mortality impacts. However, such studies are rare in India. For the first time, the short term impact of PM2.5 concentrations on non-disease specific mortality in New Delhi was assessed using Poisson regression models. Results indicated that the excessive risk associated with PM2.5 estimated was 0.57, which was higher than the other regulated pollutants. This indicates a projected 6.2 and 6.5% decrease in mortality by meeting the PM2.5 Indian standards and WHO set limits, respectively.