Effect of sonication on the reactivity of silica fume in portland cement mortars

Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.Currently, the use of silica fume for the production of mortars and high-performance concrete is of great importance to the construction materials sector. Different applications of silica fume have generated extensive studies about its high reactivity as a pozzolanic material, in addition to its effect on the properties of some materials within which it is incorporated. In this study a sonication process was applied by means of which the deagglomeration of the larger particles of densi¿ed silica fume (CSF) was achieved. The result is a CSF treated with the ultrasound probe, which is obtained for different tests where the parameters of sonication such as sonication power level and sonication time are varied. This treatment makes it possible to increase the quantity of submicrometric particles in the sample. The effect of sonication process on CSF produces a greater quantity of very ¿ne particles, which improve the pozzolanic reactivity of silica fume and increase the ¿xation of hydrated lime. This behaviour also produces higher mechanical strength in mortars manufactured with sonicated silica fume (SSF). The mechanical strengths of SSF mortars were greater than those for control and CSF mortar. Different percentages of cement were substituted (between 0 and 15% by weight), and in all cases the SSF mortars showed important differences from the CSF mortar. It was observed that for the longest sonication times and highest sonication power levels, mechanical strengths were increased.The authors are grateful to the Spanish company Ferroatlantica S.L. for their financial support; to the Spanish Agency of International Cooperation and Development (AECID) for the doctorate grant to D.M.-V.; to the Spanish government for their support to the project BIA 2007-63252; and to FEDER for its financial support to our research projects.Martínez Velandia, DA.; Paya Bernabeu, JJ.; Monzó Balbuena, JM.; Borrachero Rosado, MV. (2011). Effect of sonication on the reactivity of silica fume in portland cement mortars. Advances in Cement Research. (1):23-31. https://doi.org/10.1680/adcr.8.00027S2331

Augmenting the pearl millet core collection for enhancing germplasm utilization in crop improvement

Developing a core collection that represents the diversity of entire collection is an efficient approach to enhance the use of germplasm in crop improvement. Core collections are dynamic and need to be revised when additional germplasm and information become available. In the present study, the pearl millet [Pennisetum glaucum (L.) R. Br.] core collection, consisting of 1600 accessions selected from about 16,000 accessions characterized at the International Crops Research Institute for the Semi-Arid Tropics Genebank by 1998, was augmented by adding 501 accessions representing 4717 accessions assembled and characterized in the past 9 yr. The revised core consists 2094 accessions. (Five duplicate and two male sterile accessions were deleted from original core collection.) A comparison of mean data using Newman-Keuls test, variance using Levene's test, and distribution using χ2 test indicated that the variation in the entire collection of 20,766 accessions was preserved in the revised core collection. A few important phenotypic correlations that may be under coadapted gene complexes were preserved in the revised core collection. The Shannon-Weaver diversity index for different traits was similar in the revised core and entire collection. The revised core collection was observed to be more valuable than the original core as it has sources of resistance for important diseases such as downy mildew. The revised core collection could be a point of entry to the proper exploitation of pearl millet genetic resources for crop improvement

Bacillus sonorensis, a novel plant growth promoting rhizobacterium in improving growth, nutrition and yield of chilly (Capsicum annuum L.)

Plant growth promoting rhizomicroorganisms (PGPR) play an important role in improving plant growth, nutrition and yield of different crops. Chilly is one of the major commercial crops of India with large export potential. The first experiment was conducted with 10 PGPR to investigate their effects on growth and yield of chilly. Although most of the plant parameters studied were statistically not significant, 2 PGPR viz. Paenibacillus polymyxa and Pantoea dispersa showed agronomic improvement in plant growth as compared to control and other treatments. The second experiment was conducted with these 2 PGPR plus 8 more PGPR in order to select the best PGPR for inoculating chilly. Inoculation significantly improved the growth, nutrition and fruit yield as compared to uninoculated control. Considering plant dry biomass and fruit yield, Methylobacterium radiotolerans proved to be the best PGPR. Further screening with M. radiotolerans plus 2 more PGPR viz. Bacillus sonorensis and Paenibacillus elgii on 2 common varieties of chilly resulted in enhanced plant dry biomass, nutrition and fruit yield. The results clearly brought out that B. sonorensis is the most promising PGPR inoculant for chilly. The plant growth promoting traits revealed that B. sonorensis is a P-solubilizer and able to produce indole acetic acid, siderophore, chitinase, hydrogen cyanide and good in biofilm formation

Research Letter - Pharmacological investigation of prunin-6"-O-p-coumarate: A flavonoid glycoside

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