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  • Author or Editor: M. R. Chakraborty x
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Abstract  

Several parts of plants are used in herbal and Ayurvedic medicines of India. The different elemental constituents at trace levels of these plant parts play an effective role in the medicines prepared. Elemental composition of different parts (root, bark, leaf, seed) of some medicinal plants of North Eastern India has been determined by using proton induced X-ray emission (PIXE). A total of 14 elements, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Br, Rb, Sr, Y, Zr and Pb have been measured. Their concentrations were found to vary in different samples. Medicinal properties of these plant samples and their elemental distribution have been correlated.

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Biological control of die-back of bottle brush (Callistemon citrinus) caused by Botryodiplodia theobrome was made with the application of antagonistic agents like Trichoderma viride, T. lignorum, T. harzianum, Aspergillus niger and Penicillium citrinum. The effect of volatile and non-volatile antibiotics of Trichoderma origin on growth inhibition of the die-back pathogen was studied. T. harzianum showed maximum growth inhibition (75.33%) of the pathogen through mycoparasitism and the non-volatiles produced by the same agent exhibited its excellent antagonism to the growth of the pathogen (91.11%) under in vitro condition and that the effect was also proved to be durable.

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Siderophores are low molecular weight (<1000 D) iron chelating compounds produced by microorganisms. Production of siderophore is a device of antagonism as by virtue of the capacity of siderophore production, a microorganism competes for Fe (III) with the others. Production of siderophores by 9 different soil fungi and wood-decay fungi was studied following CAS - assay and CAS - agar plate assay. Optimization for the production of siderophores was done by varying the levels of pH and Fe (III) concentrations in the low nutrient medium. All the test fungi could produce siderophores, though the degree of production recorded to be very low both in Botryodiplodia theobromae and in Fusarium spp. On the other hand, all the species of Trichoderma showed their excellency in siderophore production. The optimum pH for production of siderophores remained at neutral pH level though the range varied from pH 6.0-8.0. The optimum range of the concentration of Fe (III) required for siderophore production was recorded to be 1.5-21.0 µM. However, the stress condition of iron might be a decisive factor for siderophore production.

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Abstract

The study deals with the morphological and thermal analysis of binary rubber blends of acrylonitrile-co-butadiene rubber (NBR) with another polymer. Either ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA), chlorosulphonated polyethylene (CSM), or polyvinyl chloride (PVC) has been selected for the second phase. Depending on the relative polarity and interaction parameter of the components, the binary blends showed development of a bi-phasic morphology through scanning electron microscopy (SEM). Use of different types of thermal analysis techniques revealed that these blends are generally incompatible excepting one of NBR and PVC. Derivative differential scanning calorimetry (DDSC), in place of conventional DSC, has been used to characterize the compatibility behavior of the blends. NBR–PVC shows appearance of only one glass transition temperature (T g) averaging the individual T g’s of the blend components. The partially missible blend of NBR and CSM shows a broadening of T g interval between the phase components, while the immiscible blends of either NBR–EPDM or NBR–EVA do not show any change in T g values corresponding to the individual rubbers of their blend. The experimental T g values were also compared with those calculated theoretically by Fox equation and observed to match closely with each other. Studies have also been made to evaluate the thermal stability of these blends by thermo-gravimetric analysis (TG) and evaluation of activation energy of respective decomposition processes by Flynn and Wall method. Thermo-mechanical analysis (TMA) was found to be effective for comparison of creep recovery and dimensional stability of the blends both at sub-ambient as well as at elevated temperatures.

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