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D. Gopi,P.R. Bhalaji,V.C.A. Prakash,A.K. Ramasamy,L. Kavitha,J.M.F. Ferreira 한국물리학회 2011 Current Applied Physics Vol.11 No.3
A method to synthesize hydroxyapatite (HAP) ceramic powders using a metal-oxalate route with calcium chloride and phosphoric acid as calcium and phosphorus precursors respectively is described. Ethylene glycol was used as a reaction medium and oxalic acid as a chelating agent. The resulting HAP powders were calcined at 600 ℃ for 6 h and subsequently sintered at 900 ℃ for 2 h. FT-IR, XRD and SEM techniques were employed for the characterization of the synthesized particles. Moreover, the influence of reaction temperature on the HAP formation was also studied. The results have shown successful formation of the crystalline, uniform sized, uniform shaped and stoichiometric HAP powders at a reaction temperature of 75 ℃ which was found to be the optimum temperature for the preparation. The grain size of the synthesized sample was 680 nm in length and 440 nm in width.
M.R.A. Hassan,I.A. Azid,M. Ramasamy,J. Kadesan,K.N. Seetharamu,A.S.K. Kwan,P. Arunasalam 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.1
In this paper, the mass optimization of four bar linkages is carried out using genetic algorithms (GA) with single and dual constraints. The single constraint of bending stress and the dual constraints of bending and buckling stresses are imposed. From the movement response of the bar linkage mechanism, the analysis of the mechanism is developed using the combination of kinematics, kinetics, and finite element analysis (FEA). A penalty-based transformation technique is used to convert the constrained problem into an unconstrained one. Lastly, a detailed comparison on the effect of single constraint and of dual constraints is presented.
Hassan, M.R.A.,Azid, I.A.,Ramasamy, M.,Kadesan, J.,Seetharamu, K.N.,Kwan, A.S.K.,Arunasalam, P. Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.1
In this paper, the mass optimization of four bar linkages is carried out using genetic algorithms (GA) with single and dual constraints. The single constraint of bending stress and the dual constraints of bending and buckling stresses are imposed. From the movement response of the bar linkage mechanism, the analysis of the mechanism is developed using the combination of kinematics, kinetics, and finite element analysis (FEA). A penalty-based transformation technique is used to convert the constrained problem into an unconstrained one. Lastly, a detailed comparison on the effect of single constraint and of dual constraints is presented.
Histopathology and Ultrastructural Findings of Fatal COVID-19 Infections on Testis
Achua Justin K.,Chu Kevin Y.,Ibrahim Emad,Khodamoradi Kajal,Delma Katiana S.,Iakymenko Oleksii A.,Kryvenko Oleksandr N.,Arora Himanshu,Ramasamy Ranjith 대한남성과학회 2021 The World Journal of Men's Health Vol.39 No.1
Purpose: To evaluate the presence and analyze the pathological changes within the testes of patients who died or recovered from severe acute respiratory syndrome coronavirus 2 (COVID-19) complications. Materials and Methods: Testis tissue was collected from autopsies of COVID-19 positive (n=6) and negative men (n=3). Formalin-fixed paraffin-embedded tissues were stained with hematoxylin and eosin (H&E) and subjected to immunofluorescence for angiotensin-converting enzyme 2 (ACE-2) expression. Fluorescent-labeled tissue slides were imaged on a quantitative pathology scope with various zoom levels allowing for qualitative and quantitative interpretation. Tissue from four COVID- 19 positive autopsy cases and a live seroconverted patient was imaged with transmission electron microscopy (TEM). Results: H&E histomorphology showed three of the six COVID-19 biopsies had normal spermatogenesis while the remaining three had impaired spermatogenesis. TEM showed the COVID-19 virus in testis tissue of one COVID-19 positive autopsy case and the live biopsy, H&E stain on the same autopsy case demonstrated interstitial macrophage and leukocyte infiltration. Immunofluorescent stained slides from six COVID-19 positive men demonstrated a direct association between increased quantitative ACE-2 levels and impairment of spermatogenesis. Conclusions: The novel COVID-19 has an affinity for ACE-2 receptors. Since ACE-2 receptor expression is high in the testes, we hypothesized that COVID-19 is prevalent in testes tissue of infected patients. This study suggests the male reproductive tract, specifically the testes, may be targets of COVID-19 infection. We found an inverse association between ACE-2 receptor levels and spermatogenesis, suggesting a possible mechanism of how COVID-19 can cause infertility.
Isolation of Nitrogen Fixing Bacteria from Fungus Termites
GOMATHI, V.,A. RAMALAKSHMI,K. RAMASAMY 한국곤충학회 2005 Entomological Research Vol.35 No.2
Biological nitrogen fixation by the microorganisms in the gut of termites is one of the singularly important symbiotic processes, since termites invariably thrive on nitrogen poor diet. Two isolates of free living aerobic and facultative anaerobic N fixing bacteria were obtained from the guts of fungus cultivating termite, Macrotermes sp. Among the total bacterial isolates from termite gut, the per cents of N fixing aerobes viz., Azotobacter and Beijerinckia spp were 49% and 37% from the salivary gland while facultative N fixing anaerobe viz., Klebsiella and Clostridium contributed (51% and 93%). The free living aerobic bacteria were identified as Azotobacter spp (19×104 CFU mL-1) and Beijerinckia (13.2×104 CFU mL-1) from the salivary gland of the termite; interestingly, foregut, mid gut and hind gut registered a low population of these bacteria. The isolates of Azotobacter were smooth, glistening, vicid in nature, rods, gram negative and cyst forming. Isolates of Beijerinckia sp. produced copious slime, tenacious, rods, gram negative with no cyst formations. Both the isolates emitted green fluorescence and produced acid. Facultative N fixing anaerobes were harbored in the hind gut. The isolates were identified as Klebsiella (20×104 CFU mL-1) and Clostridium pasteurianum 39.1×104 CFU mL-1. Klebsiella were straight rods arranged singly or in pairs, non-motile, gram negative, whereas Clostridium pasteurianum was viscoid, motile with terminal spores. A positive correlation was observed between the extractable of these isolates and soil aggregation. The aggregates formed by the isolates increased soil aeration, porosity, water holding capacity and helped in better plant growth. Thus, the gut microflora of termite, apart from harnessing nitrogen from the atmosphere, also helps improving soil fertility.
M. Srinivasan,P. Karuppasamy,P. Ramasamy,A. K. Barua 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4
Numerical modelling has emerged as a powerful tool for the development andoptimization of directional solidification process for mass production of multicrystallinesilicon. A transient global heat transfer model is performed to investigate theeffect of bottom grooved furnace upon the directional solidification (DS) process ofmulti-crystalline silicon (mc-Si). The temperature distribution, von Mises stress,residual stress and dislocation density rate in multi-crystalline silicon ingots grown bymodified directional solidification method have been investigated for five growth stagesusing finite volume method at the critical Prandtl number, Pr = 0.01. This paperdiscusses bottom groove furnace instead of seed crystal DS method. It achieves anadvanced understanding of the thermal and mechanical behaviour in grown multicrystallineingot by bottom grooved directional solidification method. The von Misesstress and dislocation density were reduced while using the bottom grooved furnace. This work was carried out in the different grooves of radius 30 mm, 60 mm and 90 mmof the heat exchanger block of the DS furnace. In this paper, the results are presented for60 mm radius groove only because it has got better results compared to the othergrooves. Also, the computational results of bottom grooved DS method show betterperformance compared the conventional DS method for stress and dislocation densityin grown ingot.