Papers

Phytochemical study on the rhizomes of Kaempferia rotunda originated from Yogyakarta, Indonesia has led to the isolation of crotepoxide, benzoic acid, tetracosanoic acid, b-sitosterol and stigmasterol. Tetracosanoic acid and benzoic acid have never been reported for this species previously. Bioactivity studies on the extracts and isolated compound (crotepoxide) were carried out. Extracts and crotepoxide from K. rotunda were not active against HL-60 (human promyelocytic leukemic) cell line in cytotoxic testing. However, the non-polar extract demonstrated moderate inhibition in antimicrobial assay whereas in FTC antioxidant testing, all extracts exhibited strong activity as compared to vitamin E.

In the present investigation, an attempt has been made to examine the effect of different concentrations of sodium hydroxide and sodium chloride on the corrosion properties of zircon reinforced Al 6061 metal matrix composites. Zircon particles with size 50-80µm have been introduced into the Al alloy by vortex technique. The alloy and the composite were subjected to weight loss corrosion test. The corrosion rate of the alloy is found to be higher than the composites. It has been further noticed that corrosion rate of composite decreases with increase in zircon particle content.

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Phytochemical studies on rhizomes of Zingiber cassumunar have yielded one phenylbutenoid, (E) - 4 - (3', 4'-dimethoxyphenyl) but-3-en-1-yl acetate (1) and 3, 4-dimethoxybenzoic acid (2). The compounds were elucidated by spectroscopic techniques including Infrared Spectroscopy (IR), 1D and 2D Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).

Dielectric materials like Alumina (Al₂O₃) have been used for design of microwave antennas. However, due to material properties and difficulty in fabrication, it is not suitable for L, C, X and Ku-Band frequencies applications between 1-15 GHz. Polymer materials like Nylon, Teflon, polyacetal, polypropylene etc., however, have shown good gain and radiation characteristics at these frequencies and are easily fabricated with different design profiles. The polymer materials considered suitable for microwave antennas should have fairly large dielectric constant e_r (between 1.5-10) and relatively small tan d loss factor (< 0.001) at these frequencies. The paper presents material characteristics, antenna profiles and gain-radiation characteristics of some important polymer microwave antennas that have found wide acceptance in the industry.