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      • KCI등재

        Effect of accelerators with waste material on the properties of cement paste and mortar

        Kiran Devi,Babita Saini,Paratibha Aggarwal 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.2

        Accelerators are used to speed up the construction by accelerating the setting time which helps in early removal of formwork thus leading to faster construction rate. Admixtures are used in mortar and concrete during or after mixing to improve certain properties of material which cannot be achieved in conventional cement mortar and concrete. The various industrial by products make nuisance and are hazardous to ecosystem as well. These wastes can be used in the construction industries to reduce the consumption of cement/aggregates, cost; and save the energy and environment by utilising waste and eliminate their disposal problem as well. The effect of calcium nitrate and triethanolamine (TEA) as accelerators and marble powder (MP) as waste material on the various properties of cement paste and mortar has been studied in the present work. The replacement ratio of MP was 0-10% @ 2.5% by weight of cement. The addition of calcium nitrate was 0% and 1%; and variation of addition of TEA was 0-0.1@ 0.025% and 0.1-1.0@ 0.1% by weight of cement. On the basis of setting time, some mix proportions were selected and further investigated. Setting time and soundness of cement paste; compressive strength and microstructure of mortar mix of selected mix proportions were studied experimentally at 3, 7 and 28 days aging. Results showed that use of MP, calcium nitrate, TEA and their combination reduced setting time of cement paste for all the mixes. Addition of calcium nitrate increased the compressive strength at all curing ages while MP and TEA decreased the compressive strength. The mechanism of additives was discussed through scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis of the specimens.

      • KCI등재

        Utilization of Kota stone slurry powder and accelerators in concrete

        Kiran Devi,Babita Saini,Paratibha Aggarwal 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.23 No.3

        Recent advances in the concrete technology are aiding in minimizing the use of conventional materials by substituting by-products of various industries and energy sources. A large amount of stone waste i.e., dust and slurry form both are being originated during natural stone processing and causing deadily effects on the environment. The disposal problem of stone waste can be resolved effectively by using waste in construction industries. In present work, Kota stone slurry powder, as a substitution of cement was used along with accelerators namely calcium nitrate and triethanolamine as additives, to study their impact on various properties of the concrete mixtures. Kota stone slurry powder (7.5%), calcium nitrate (1%) and triethanolamine (0.05%) were used separately as well in combination in different concrete mixtures. Mechanical Strength, modulus of elasticity and electrical resistivity of concrete specimens of different mix proportions under water curing were studied experimentally. The durability properties in terms of strength and electrical resistivity against sulphate and chloride solution attack at various curing ages were also studied experimentally. Results showed that accelerators and Kota stone slurry powder separately enhanced the mechanical strength and electrical resistivity; but, their combination decreased strength at all curing ages. The durability of concrete specimens was also affected under the exposure to chemical attack too. Kota stone slurry powder found to be the most effective material among all materials. Material characterization was also done to study the microstructural properties.

      • KCI등재후보

        Vasculosyncytial membrane in relation to syncytial knots complicates the placenta in preeclampsia

        K. Devi Sankar,P. Sharmila Bhanu,Sujatha Kiran,B. A. Ramakrishna,V. Shanthi 대한해부학회 2012 Anatomy & Cell Biology Vol.45 No.2

        The vasculosyncytial membrane (VSM), primary site of fetomaternal exchange is formed when syncytiotrophoblast surrounds the terminal villi and make a close contact with capillaries. Some syncytiotrophoblast forms thin single layer of villous and some syncytial nuclei become piled up to form the syncytial knots (SKs). Undoubtedly there is a clear-cut inverse relation between villous VSM and fetal hypoxia. In preeclampsia (PE) the hypoxia injury disrupts the syncytial architecture which in turn initiates other complications of PE. Present study was designed to observe the morphological and histomorphometric features of 84 placentas from control and PE (42 each) collected from Department of Obstetrics and Gynecology. Neonatal weight and placental weight were reduced in PE than the controls but the feto-placental index did not differ. The SK density and VSM thickness was found to be increased and was statistically significant in PE cases. In relation to SKs, the VSM thickness was twofold increased than the controls and was statistically significant. The SKs in the present study were classified as type-1, 2a, 2b, and 3. Type 1 was found to be 62% in control and 47% in PE, type 2a and 2b were 38% in control and 37% in PE, and type 3 was in 8% of PE cases. All the parameters of present study reveal the adverse effects of PE influencing on both morphological and microscopical features of the placenta resulting in fetal hypoxia.

      • KCI등재

        Histomorphological and morphometrical changes of placental terminal villi of normotensive and preeclamptic mothers

        K. Devi Sankar,P. Sharmila Bhanu,K. Ramalingam,Sujatha Kiran,B. A. Ramakrishna 대한해부학회 2013 Anatomy & Cell Biology Vol.46 No.4

        Placental morphology and cellular arrangement are altered in maternal diseases such as preeclampsia (PE) in which oxygen delivery from the mother to the fetus is greatly disturbed, ultimately resulting in cellular oxidative stress. The present study was conducted at the Department of Anatomy and included 112 placentas (56 each from mothers with and without PE [controls]) collected at the Department of Obstetrics and Gynecology. A histological study was performed using hematoxylin and eosin staining. The morphology of stem and terminal villi (TV) was studied, and the surface area and diameter of TV and capillaries were measured. The gross placental morphometrical study revealed that the mean placental weight, thickness, diameter, and surface area were significantly lower in placentas with PE than in controls. The histomorphometrical findings of the villous surface area and diameter were lower in placentas with PE, whereas the TV density was higher in placentas with PE than in controls, and the differences were significant (P<0.0001). In these TV, the diameter and density of fetal blood vessels of placentas with PE were significantly lower than those of controls (P<0.05). In conclusion, the both morphological and histological changes in PE placentas are indicative of the pathogenesis of maternal and fetal morbidity and mortality in women with PE. The observed and comparative histomorphometrical changes indicate a decline in all aspects of the PE placenta, except the number of TV.

      • Agrobacterium tumefaciens Mediated Genetic Transformation of Pigeonpea [Cajanus cajan (L.) Millsp.]

        Kumar, S.Manoj,Syamala, D.,Sharma, Kiran K.,Devi, Prathibha The Korean Society of Plant Biotechnology 2004 Plant molecular biology and biotechnology research Vol.6 No.2

        Optimal protocol for efficient genetic transformation has been defined to aid future strategies of genetic engineering in pigeon pea with agronomically important genes. Transgenic pigeonpea plants were successfully produced through Agrobacterium tumefaciens-mediated genetic transformation method using cotyledonary node explants by employing defined culture media. The explants were co-cultivated with A. tumefaciens strain C-58 harboring the binary plasmid, pCAMBIA-1301 [con-ferring $\beta$-glucuronidase(GUS) activity and resistance to hygromycin] and cultured on selection medium (regeneration medium supplemented with hygromycin) to select putatively transformed shoots. The shoots were then rooted on root induction medium and transferred to pots containing sand and soil mixture in the ratio of 1:1. About 22 putative TO transgenic plants have been produced. Stable expression and integration of the transgenes in the putative transgenics were confirmed by GUS assay, PCR and Southern blot hybridization with a transformation efficiency of over 45%. Stable integration and expression of the marker gene has been confirmed in the TO and T1 transgenics through PCR, and Southern hybridization.

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