Abstract: The work on indigenous binders in this paper focused on the following indigenous raw materials: red clay, red lava and pumice (as primary aluminosilicate precursors), wood ash and gypsum (as supplementary minerals), and sodium sulfate and lime (as alkali activators). The experimental methods used for evaluation of these indigenous raw materials included laser granulometry, x-ray fluorescence (XRF) spectroscopy, and chemical reactivity. Formulations were devised for transforming these raw materials into alkali aluminosilicate-based hydraulic cements. These formulations were processed into hydraulic cements via simple heating and milling actions to render thermal activation, mechanochemical and size reduction effects. The resulting hydraulic cements were subjected to laser granulometry, heat of hydration and reactivity tests. These cements were also used to prepare mortar mixtures, which were evaluated via performance of compressive strength tests. The measured values of strength were correlated with the reactivity, size distribution and microstructural features of raw materials. Some of the indigenous hydraulic cements produced in this reporting period yielded viable levels of compressive strength. The correlation trends established in this work are being evaluated for development of simple and thorough methods of qualifying indigenous raw materials for use in production of indigenous hydraulic cements.
Abstract: In order to face current compelling environmental problems affecting the planet, the construction industry needs to adapt. It is widely acknowledged that there is a need for durable, high-performance, low-greenhouse gas emission binders that can be used as an alternative to Portland cement (PC) to lower the environmental impact of construction. Alkali activated materials (AAMs) are considered a more sustainable alternative to PC materials. The binders of AAMs result from the reaction of an alkali metal source and a silicate powder or precursor which can be a calcium silicate or an aluminosilicate-rich material. This paper evaluates the particle size, specific surface area, chemical and mineral composition and amorphousness of silicate materials (most industrial waste locally produced in Ireland and Saudi Arabia) to develop alkali-activated binders that can replace PC resources in specific applications. These include recycled ceramic brick, bauxite, illitic clay, fly ash and metallurgical slag. According to the results, the wastes are reactive and comply with building standards requirements. The study also evidenced that the reactivity of the Saudi bauxite (with significant kaolinite) can be enhanced on thermal activation; and high calcium in the slag will promote reaction; which should be possible with low alkalinity activators. The wastes evidenced variable water demands that will be taken into account for mixing with the activators. Finally, further research is proposed to further determine the reactive fraction of the clay-based precursors.
Abstract: The main objective of the study is focused in
producing slag based geopolymer concrete obtained with the addition
of alkali activator. Test results indicated that the reaction of silicates
in slag is based on the reaction potential of sodium hydroxide and the
formation of alumino-silicates. The study also comprises on the
evaluation of the efficiency of polymer reaction in terms of the
strength gain properties for different geopolymer mixtures.
Geopolymer mixture proportions were designed for different binder
to total aggregate ratio (0.3 & 0.45) and fine to coarse aggregate ratio
(0.4 & 0.8). Geopolymer concrete specimens casted with normal
curing conditions reported a maximum 28 days compressive strength
of 54.75 MPa. The addition of glued steel fibres at 1.0% Vf in
geopolymer concrete showed reasonable improvements on the
compressive strength, split tensile strength and flexural properties of
different geopolymer mixtures. Further, comparative assessment was
made for different geopolymer mixtures and the reinforcing effects of
steel fibres were investigated in different concrete matrix.
Abstract: This paper presents a study on use of alkali activated bottom ash (BA) and ground granulated blast furnace slag (GGBS) blend in paver blocks. A preliminary effort on alkali-activated bottom ash, blast furnace slag based geopolymer (BA-GGBS-GP) mortar with river sand was carried out to identify the suitable mix for paver block. Several mixes were proposed based on the combination of BA-GGBS. The percentage ratio of BA: GGBS was selected as 100:0, 75:25, 50:50, 25:75 and 0:100 for the source material. Sodium based alkaline activators were used for activation. The molarity of NaOH was considered as 8M. The molar ratio of SiO2 to Na2O was varied from 1 to 4. Two curing mode such as ambient and steam curing 60°C for 24 hours were selected. The properties of paver block such as compressive strength split tensile strength, flexural strength and water absorption were evaluated as per IS15658:2006. Based on the preliminary study on BA-GGBS-GP mortar, the combinations of 25% BA with 75% GGBS mix for M30 and 75% BA with 25% GGBS mix for M35 grade were identified for paver block. Test results shows that the combination of BA-GGBS geopolymer paver blocks attained remarkable compressive strength under steam curing as well as in ambient mode at 3 days. It is noteworthy to know BA-GGBS-GP has promising future in the construction industry.
Abstract: The present study has been conducted to characterize
the prophenoloxidase (PPO) system of the desert locust, Schistocerca
gregaria following injection of Bacillus thuringiensis kurstaki (Bt).
The bulk of PPO system was associated with haemocytes and a little
amount was found in plasma. This system was activated by different
activators such as laminarin, lipopolysaccharide (LPS) and trypsin
suggesting that the stimulatory mechanism may involve an enzyme
cascade of one or more associated molecules. These activators did
not activate all the molecules of the cascade. Presence of
phenoloxidase activity (PO) coincides with the appearance of protein
band with molecular weight (MW) 70.154 KD (Kilo Dalton).
Abstract: Glutathione S-transferase was purified from human
erythrocytes and effects of some polyphenols were investigated on
the enzyme activity. The purification procedure was performed on
Glutathione-Agarose affinity chromatography after preparation of
erythrocytes hemolysate with a yield of 81%. The purified enzyme
showed a single band on the SDS-PAGE. The effects of some
poliphenolic compounds such as catechin, dopa, dopamine, progallol
and catechol were examined on the in vitro GST activity. Catechin
was determined to be inhibitor for the enzyme, but others were not
effective on the enzyme as inhibitors or activators. IC50 value -the
concentration of inhibitor which reduces enzyme activity by 50%-
was estimated to be 10 mM. Ki constants were also calculated as 6.38
± 0,70 mM with GSH substrate, and 3.86 ± 0,78 mM with CDNB
substrate using the equations of graphs for the inhibitor, and its
inhibition type was determined as non-competitive.
Abstract: Despite of the preponderant role played by cement among the construction materials, it is today considered as a material destructing the environment due to the large quantities of carbon dioxide exhausted during its manufacture. Besides, global warming is now recognized worldwide as the new threat to the humankind against which advanced countries are investigating measures to reduce the current amount of exhausted gases to the half by 2050. Accordingly, efforts to reduce green gases are exerted in all industrial fields. Especially, the cement industry strives to reduce the consumption of cement through the development of alkali-activated geopolymer mortars using industrial byproducts like bottom ash. This study intends to gather basic data on the flowability and strength development characteristics of alkali-activated geopolymer mortar by examining its FT-IT features with respect to the effects and strength of the alkali-activator in order to develop bottom ash-based alkali-activated geopolymer mortar. The results show that the 35:65 mass ratio of sodium hydroxide to sodium silicate is appropriate and that a molarity of 9M for sodium hydroxide is advantageous. The ratio of the alkali-activators to bottom ash is seen to have poor effect on the strength. Moreover, the FT-IR analysis reveals that larger improvement of the strength shifts the peak from 1060 cm–1 (T-O, T=Si or Al) toward shorter wavenumber.
Abstract: A gene network gives the knowledge of the regulatory
relationships among the genes. Each gene has its activators and
inhibitors that regulate its expression positively and negatively
respectively. Genes themselves are believed to act as activators and
inhibitors of other genes. They can even activate one set of genes and
inhibit another set. Identifying gene networks is one of the most
crucial and challenging problems in Bioinformatics. Most work done
so far either assumes that there is no time delay in gene regulation or
there is a constant time delay. We here propose a Dynamic Time-
Lagged Correlation Based Method (DTCBM) to learn the gene
networks, which uses time-lagged correlation to find the potential
gene interactions, and then uses a post-processing stage to remove
false gene interactions to common parents, and finally uses dynamic
correlation thresholds for each gene to construct the gene network.
DTCBM finds correlation between gene expression signals shifted in
time, and therefore takes into consideration the multi time delay
relationships among the genes. The implementation of our method is
done in MATLAB and experimental results on Saccharomyces
cerevisiae gene expression data and comparison with other methods
indicate that it has a better performance.