Defects induced ferromagnetism in Mn doped ZnO

Single phase Mn doped (2 at %) ZnO samples have been synthesized by solid-state reaction technique. Before the final sintering at 500 C, the mixed powders have been milled for different milling periods (6, 24, 48 and 96 hours). The grain sizes of the samples are very close to each other (~ 32 \pm 4 nm). However, the defective state of the samples is different from each other as manifested from the variation of magnetic properties and electrical resistivity with milling time. All the samples have been found to be ferromagnetic with clear hysteresis loops at room temperature. The maximum value for saturation magnetization (0.11 {\mu}_B / Mn atom) was achieved for 96 hours milled sample. Electrical resistivity has been found to increase with increasing milling time. The most resistive sample bears the largest saturation magnetization. Variation of average positron lifetime with milling time bears a close similarity with that of the saturation magnetization. This indicates the key role played by open volume vacancy defects, presumably zinc vacancies near grain surfaces, in inducing ferromagnetic order in Mn doped ZnO. To attain optimum defect configuration favorable for ferromagnetism in this kind of samples proper choice of milling period and annealing conditions is required.Comment: Accepted in Journal of Magnetism and Magnetic Material

Recycling municipal solid wastes

Municipal refuse contains recoverable materials. It is valued in terms of savings of energy and resources. The percentage of recoverable materials varies in different countries, in different socio-economic compositions and in different seasons. The purpose of recycling is not only to reduce the Waste load in the dumping ground but more to extract some values that we otherwise achieve through the production processes of agriculture, mining and manufacture. Recycling thus supports the slogan of sustainable development. Recycling of wastes is an old practice. But due to many factors recycling is not practiced to its fullest potential. Many formal and informal organisations or individuals are involved in the work of recycling of wastes. Refuse composition is a function of levels of consumption, which is again related to the economic level of the Society. Waste is waste until the recycled and recovered value is more than the cost and labour for recovery. Municipal waste, once thrown out of the individual premises, is the property of the municipal bodies – a burden to the municipal bodies

Hydrophytes in municipal wastewater treatment and limitation

Off-site wastewater treatment at low cost is a burning issue in developing countries. Use of water hyacinth and duckweed have been tried world wide and the findings of its efficiency have been found promising. The concept has become old but the work with duckweed is still continuing at different levels. Time has come to arrive at a conclusive policy/decision to the extent this water hyacinth (Eichhorina crassipes) or duckweed (Lemna) may be utilised. The guidelines in respect of the design parameter and Operation – Maintenance schedule should be available to the community. For the strategy of wide scale success of such system the involvement of NGO’s and community participantion should be inducted from the initial stage. Different aspects have been discussed in the text to arrive at a conclusion upto what extent and at what level the system of hydrophyte based waste-water treatment will have wider use by the community

Evidence for structural discordance in the inverted metamorphic sequence of Sikkim himalaya: Towards resolving the main central thrust controversy

Inverted, metamorphism in the Himalayas is closely associated with the Main Central Thrust (MCT). In the western Himalayas, the Main Central Thrust conventionally separates high grade metamorphic rocks of the Higher Himalayan Crystalline Sequence (HHCS) from unmetamorphosed rocks of the Inner sedimentary Belt. In the eastern Himalayas, the Inner sedimentary Belt is absent, and the HHCS and meta-sedimentary Lesser Himalayan Sequence (LHS) apparently form a continuous Barrovian metamorphic sequence, leading to confusion about the precise location of the MCT. In this study, it is demonstrated that migmatitic gneisses of the sillimanite zone in the higher structural levels of the HHCS are multiply deformed, with two phases of penetrative fabric formation (S 1HHCS and S2HHCS) followed by third folding event associated with a spaced, NW-SE trending, north-east dipping foliation (S 3HHCS). The underlying LHS schists (kyanite zone and lower) are also multiply deformed, with the bedding S0 being isoclinally folded (F1LHS), and subsequently refolded (F2LHS and F 3LHS). The contact zone between, the HHCS and LHS is characterized by ductile, top-to-the southwest shearing and stabilization of a pervasive foliation that is consistently oriented NW-SE and dips northeast. This foliation is parallel to the S3HHCS foliation in the HHCS, and the S 2LHS in the LHS. Early lineations in the HHCS and LHS also show different dispersions across the contact shear zone, implying that pre-thrusting orientations of the two units were distinct. The contact shear zone is therefore interpreted to be a plane of structural discordance, shows a shear sense consistent with thrust movement and is associated with mineral growth during Barrovian metamorphism. It may well be considered to represent the MCT in this region