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"This book offers a comprehensive analysis of irons’ various roles in the plant-microbial associations. The introductory chapter stresses the essentiality of iron in biological systems. The second chapter surveys the abundance of information on iron’s pivotal role in microbial plant pathogenesis and defence. Finally, the third chapter reviews the advances in our understanding of iron metabolism in the rhizobia, soil bacteria able to establish a symbiotic association with legumes and carry out nitrogen fixation. "

"The endophytic fungi Aspergillus fumigatus was isolated from the tissues of the fruits of Garcinia griffithii. The fungal strain was identified from the colony, and it was characteristic of cell morphol ogy. The ethyl acetate extracts derived from fungus cultures showed major spots on TLC under UV light, which was continued to the isolation of the secondary metabolites. The structure of the isolated compound was elucidated on the basis of NMR analyses (1H-NMR, 13C-NMR, HMQC, HMBC and H-H COSY). The compounds were identified as: 4,6-dihydroxy, 3,8a-dimethyl-1-oxo-5-(3?-oxobutan-2?-yl)-1,4,4a,5,6,8a-hexahydronaphthalen-2-yl-1?,2?-dimethyl-5?-(2??-methylprop-1??-enyl)cyclopentane-carboxylate."

"ABSTRAKPenelitian ini difokuskan pada studi degradasi material tube boiler secondary superheater (SSH) pada pembangkit listrik. Material baja karbon rendah 2.25Cr-1Mo mengalami kerusakan retak terbuka selang 26 jam setelah tes ujicoba. Material yang mengalami kerusakan, dianalisis secara fisik dan mekanik menggunakan uji metalografi, uji komposisi kimia, Scanning electon microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDX), uji kekerasan dan uji tarik, kemudian dibandingkan dengan material baru dan lama. Struktur mikro tube rupture mengalami elongasi searah keliling lingkaran tube dan retak mikro pada batas butir mengindikasikan adanya tegangan yang melebihi kemampuan material.Hasil perhitungan tegangan (hoop stress) sebesar 42,47 MPa, melebihi nilai yang diijinkan sebesar 23,5 MPa pada maksimum temperatur metal tube 605 °C. Material mengalami degradasi saat tercapai temperatur tertinggi (overheating), dan terjadi dalam waktu singkat. Pada tube lama, degradasi terjadi karena perubahan struktur mikro perlit menjadi speroidisasi karbida yang terdekomposisi dan terdispersi pada matrik ferit. Perubahan ini terjadi karena material terekspos dalam rentang waktu lama pada lingkungan temperatur tinggi.

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ABSTRACT

This research focused on the study of material degradation of tube boiler secondary superheater (SSH) in power plant. Low carbon steel 2.25Cr-1Mo are wide open ruptured in 26 hours after the running test. Samples were analyzed with physical and mechanical tests using metallographic, chemical composition, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX), hardness and tensile test and compared with virgin and old tube. Microstructure of rupture tube undergo elongation direction of the circumference tube and micro cracks at grain boundaries indicates a stress that exceeds the ability of the material.

The stress calculations (hoop stress) of 42.47 MPa, exceeding the allowable stress of 23.5 MPa at maximum metal tube temperature of 605 °C. In the old tube, degradation occurs due to changes in the microstructure into pearlite spheroidizing carbides are decomposed and dispersed in the ferrite matrix. This change occurs because the material is exposed in a long time at high temperature environment."