Comparative microstructural and elemental analysis of iron artefacts from Kaveri valley archaeological sites

Iron has been one of the most critical technotraditions that had lasting impact on social formation throughout the Iron Age and historical period. Iron was used in warfare and subsistence economy. Our knowledge on ancient iron smelting and working have generally been derived from ethnography and ethnohistory, which is by all means, time, region, and raw material specific. Scientific analyses of ancient iron have contributed in understanding this heritage to a respectable extent, yet a comprehensive knowledge about the evolution of iron making through time and space in India eludes us. In this work, a comparative study of iron artefacts from two Iron Age/Megalithic-Early Historic sites of Tamil Nadu, south India, that is, Mangadu (burial site) and Ambal (habitation-cum-burial site) is carried out to understand the iron thermal-processing capabilities. The retrieved artefacts were examined using X-ray fluorescence (XRF) for elemental composition. The imaging of the artefacts was done using Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), and Optical Microscopy (OM). In addition, phase identification was performed using X-ray diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS). Combination of these analyses illustrates that inhabitants of Mangadu and Ambal were aware of the iron alloy manufacturing/processing techniques such as forging and hammering.     

Fluid chemistry in the Solitaire and Dodo hydrothermal fields of the Central Indian Ridge

Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion (489 mm ), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 μm and Mn = 78 μm ). Chloride depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than ~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with an off‐spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalt‐hosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the spreading axis, was characterized by high H₂ concentration of 2.7 mm . The H₂ enrichment was likely attributable to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents. Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced the H₂ enrichment. The quantitative cultivation test revealed that the microbial community associated with the hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around the H₂‐enriched hydrothermal fluid flows was also inferred from the ¹³C‐ and D‐depleted signature of CH₄ in the collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013.     

Democratic Assertions: The Making of India's Recognition of Forest Rights Act

Inclusion of marginalized sections and minorities remains one of the most vexing problems for democratic politics. This article discusses the enactment of a recent Indian law, ‘The Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Rights) Act, 2006’, as exemplifying the possibilities of inclusion of marginalized groups in democratic processes. The law was enacted in response to a nationwide mobilization of marginalized forest dwellers and their advocates demanding rights over forests. Grassroots‐level formations representing forest dwellers came together across scales and spaces to form a network that successfully negotiated India's democratic politics to achieve the passage of the law. The case illustrates the role of grassroots mobilizations in creating alternate discourses of legitimacy, networking across scales and locations, and using spaces provided by representative democracy to include the voices and demands of the marginalized in democracies.     

Mothers and Non‐Mothers: Gendering the Discourse of Education in South Asia

This essay brings together and complicates three stories within South Asian education history by gendering them. Thus modern education was actively pursued by mothers for their sons; indigenous education should be understood as continuing at home; and women were crucial actors in men's reform and nationalism efforts through both collaboration and resistance. Gendered history should go beyond the separate story of girls and women, or the understanding of women as mothers and mothers as the nation, to see these three processes as gendered. The paper argues for the coming together of historical and anthropological arguments and for using literature imaginatively.     

Transient Response of Concrete Gravity Dam Considering Dam-Reservoir-Foundation Interaction

This article deals with the finite element analysis of dam with and without fluid-structure, soil-structure and soil-structure-fluid interaction. A two-dimensional direct coupling methodology is proposed to obtain the response of dam-reservoir-foundation system considering fluid-structure and soil-structure interaction simultaneously. The displacement based finite element technique is used to formulate the dam and foundation. The reservoir is modeled by pressure based finite element to reduce the degree of freedoms and there by the computational cost. The responses of dam, reservoir, and foundation with and without fluid-structure, soil-structure and soil-structure-fluid interaction are compared to study the influence of reservoir and soil foundation on the behavior of these respective sub systems. The fundamental frequency of individual sub system decreases with the consideration of coupling effect among these sub systems. On the comparison of the responses of dam, it is observed that the displacement and principal stresses are increased if the effect of reservoir and foundation are considered and the worst responses were observed when both the fluid-structure and soil-structure interaction effects are considered simultaneously. The magnitude and distribution of stresses within the foundation change with the consideration of soil-structure-fluid interaction. Similar to wstresses in the foundation, the hydrodynamic pressure within the reservoir also gets magnified due to interaction effects. The velocity distribution within the reservoir becomes distorted when the fluid-structure and soil-structure-fluid interaction are considered.     

Anomalous fading and crystalline structure: Studies on individual chondrules from the same parent body

Plagioclase feldspar is the major luminescent mineral in meteorites. Thermoluminescence (TL) characteristics, peak temperature (T_m), full width at half maximum (FWHM), ratio of high (HT) to low temperature (LT) peak, and TL sensitivity (TL/dose/mass) to an extent reflect degree of crystallinity of the mineral. The present study explores and establishes a correlation between quantum mechanical anomalous (athermal) fading and structural state by examining TL of individual chondrules. Chondrules were separated using freeze-thaw technique from a single fragment of Dhajala meteorite. The results show large variation in T_m (155?230°C), FWHM (80?210°C) and HT/LT (0.07–0.47) and seem to be positively correlated. TL sensitivity (ranging from 14 to 554 counts/s/Gy/mg) decreases with increasing T_m and FWHM. Large variations in TL parameters (Tm, FWHM, HT/LT, and Sensitivty) suggest that individual chondrules had different degree of crystallization. Thermal annealing experiments suggest that comparatively ordered form of feldspar can be converted to a disordered form by annealing the sample at high temperatures (1000°C) for long time (10 hr) in vacuum (1 mbar pressure) condition and rapidly cooling it. Measured anomalous fading suggest that fading rate increases as the crystal form changes from an ordered state to a disordered state. However, the fading rate becomes nearly negligible for the most disordered feldspars.