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Articles by P. Ramasamy
Total Records ( 6 ) for P. Ramasamy
  P. Srinivasan , P. Ramasamy , G. P. Brennan and R.E.B. Hanna
  Bacteriophages of Vibrio harveyi from a shrimp farm located at Tuticorin, Tamilnadu, India, were isolated, characterized and identified. The phages, when examined by electron microscopy, were found to have icosahedral morphology. The phages belong to the Siphoviridae family and were designated VH1 to VH8. They produced circular clear plaques of growth inhibition on Vibrio sp., plate cultures. The growth inhibitory effects of the bacteriophages on isolates of V. harveyi were screened by a one-step agar bioassay method and the results suggest that the infectivity of the V. harveyi phages was not affected by ribonuclease, protease, trypsin, chloroform, acetone, ethyl alcohol, methyl alcohol and Triton-X100 treatment at 37°C. Even after their storage in chloroform or DMSO (dimethyl sulfoxide, 7%) at -40°C. They showed 100% infectivity and plaque-forming ability. In contrast, Infectivity of the V. harveyi phages was affected by lysozyme and SDS and in these cases; plaques were not formed on agar plate assays. The phages were found to be stable over the pH range 6-11 and exhibited optimal survival at 37°C while complete inactivation occurred at temperatures exceeding 55°C. All the isolates of bacteriophage (VH1-VH8) initiated an infection cycle and caused lysis of the host bacterial cells within 2 h from the start of incubation. The propagation curve for each phage shows a burst time started from 1-10 h. The results suggest that bacteriophages of Vibrio sp., might be effectively used in vivo as biological agents to control these pathogenic bacteria in aquaculture systems.
  A. Claude , V. Vaithianathan , R. Bairava Ganesh , R. Sathyalakshmi and P. Ramasamy
  Potassium Di-hydrogen Phosphate (KDP), crystal is a good nonlinear optic material having Second Harmonic Generation property (SHG). These KDP crystal is grown with bimetallic dopants Nikel-Magnesium (Ni3+, Mg2+) to form Nikel-Magnesium Di-hydrogen Phosphate (NMKDP). The grown crystals were analysed for structural and optical characteristics and compared with pure KDP. FTIR analysis explains the inclusion of the metallic impurities which extends the transmission region visibly. High resolution XRD confirms the order of crystallinity of the material which is found to be superior in the pure form than the bimetallic form thereby conforming the inclusion of the bimetals. The conversion efficiency and verification of SHG generation of the grown crystals were also confirmed by Kurtz method.
  G. Anandha Babu , R. Perumal Ramasam , P. Ramasamy and S. Natarajan
  Single crystals of benzophenone hydrazone (BH) were successfully grown by slow evaporation method at constant temperature, 30 °C. The crystal structure of BH has been determined, and it belongs to the noncentrosymmetric space group P21. The grown crystal has been characterized by FT-IR). The optical transition and the lower cutoff wavelength of the BH have been identified by UV–vis–NIR studies. Thermo gravimetric analysis and differential thermal analysis have been carried out; the BH was found to be thermally stable up to 104 °C. Powder second harmonic generation (SHG) was investigated to explore its nonlinear optical (NLO) properties. The high SHG is due to one dimensional charge transfer between amine and phenyl group. Both the real εr and imaginary εi components of the dielectric constant have been calculated as functions of photon energy.
  P. Rajesh and P. Ramasamy
  Single crystals of DL-malic acid-doped ammonium dihydrogen phosphate have been grown using slow evaporation method and also by Sankaranarayanan–Ramasamy (SR) method with the vision to improve the properties of the ADP crystals. The characterization of grown crystals was made by single-crystal X-ray diffraction, powder X-ray diffraction, UV–vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Vicker's microhardness, dielectric measurements, high-resolution X-ray diffraction (HRXRD) and second-harmonic studies. Structural difference between pure and doped crystal has been studied by XRD analysis. Functional groups were identified by FTIR spectroscopy. The grown crystals were found to be transparent in the entire visible region. Decomposition temperatures of the grown crystals were measured by DTA. Vicker's hardness study carried out on (0 0 1) face at room temperature shows increased hardness of the doped crystals and SR-method-grown crystals. Dielectric measurements reveal that SR-method-grown DLM-doped ADP crystals have low dielectric loss. Crystalline perfection of the grown crystals is analyzed using HRXRD. Preliminary measurements indicate that the second harmonic generation efficiency of the doped crystals at a fundamental wavelength of 1064 nm is roughly 1.5 times greater than that of pure ADP.
  A. Krishnika and P. Ramasamy
  The present study was initiated to assess the occurrence, distribution and composition of Vibrio sp. and to evolve management strategy in the live feed Artemia franciscana. The occurrence of total heterotrophic bacteria was observed in the cysts of A. franciscana whereas, the Vibrio sp. appeared only at the 16th h A. franciscana nauplii. In 24th h A. franciscana nauplii, the bacterial counts remained very high and all these indicate that the live feed organism is yet another source of bacterial entry into the hatchery system and can be a serious problem in the culture system unless remedial measures are taken. In order to reduce the bacterial counts in the larval rearing tank water, water was exchanged (100%) after 18th h of A. franciscana hatching. The current study also revealed that the continuous exchange of A. franciscana rearing tank water for an interval of every two hours will be an effective method to reduce the bacterial counts and may help to avoid subsequent disease problem.
  S. Vairamani , N. Subhapradha , P. Ramasamy , A. Barwin Vino , S. Raveendran and A. Shanmugam
  Marine animals have great potential for providing novel drug leads with novel mechanism of action. The aim of the present study was to evaluate the antimicrobial potency of methanolic extract of whole body tissue of Sepiella inermis and Ethylene Diamine Tetra Acetate (EDTA) extract of cuttlebone (polysaccharides) against ten human pathogens. S. inermis tissue was extracted with 100% methanol for about 48 h, centrifuged and supernatant was concentrated under vacuum in desiccator. The polysaccharide extract was obtained from the internal shell using 10 mM hot EDTA. The final product was used for assaying the antibacterial activity by disc diffusion method in different concentrations. In 100% concentration, the highest inhibition zone of 12 mm was observed against Klebsiella pneumoniae and Staphylococcus aureus in methanolic extract of whole body tissue and Staphylococcus aureus alone in EDTA extract from cuttlebone. In 75% concentration, methanolic extract showed highest activity of 9 mm against K. pneumoniae, Staphylococcus aureus and Staphylococcus pneumoniae whereas the EDTA extract showed highest activity 8 mm against Vibrio cholerae, Klebsiella pneumoniae and Vibrio alginolyticus. In 50% concentration, the maximum activity of 9 mm was recorded against Klebsiella pneumoniae and Staphylococcus aureus in methanolic extract; whereas maximum activity (11 mm) was recorded against E. coli in EDTA extract. In 25% concentration, the both maximum and minimum activity 7 mm was recorded against Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus aureus in methanolic extract; Vibrio alginolyticus in EDTA extract. This study reveals that both the methanolic extract of the whole body tissue and EDTA extract of cuttlebone have good antimicrobial activity depending on the concentration.
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