Spectral signatures of dissipative standing shocks and mass outflow in presence of Comptonization around a black hole

Accretion flows having positive specific energy are known to produce outflows and winds which escape to a large distance. According to Two Component Advective Flow (TCAF) model, centrifugal pressure dominated region of the flow just outside the black hole horizon, with or without shocks, acts as the base of this outflow. Electrons from this region are depleted due to the wind and consequently, energy transfer rate due to inverse Comptonization of low energy photons are affected. Specifically, it becomes easier to cool this region and emerging spectrum is softened. Our main goal is to show spectral softening due to mass outflow in presence of Compton cooling. To achieve this, we modify Rankine-Hugoniot relationships at the shock front when post-shock region suffers mass loss due to winds and energy loss due to inverse Comptonization. We solve two-temperature equations governing an accretion flow around a black hole which include Coulomb exchange between protons and electrons and other major radiative processes such as bremsstrahlung and thermal Comptonization. We then compute emitted spectrum from this post-shock flow. We also show how location of standing shock which forms outer boundary of centrifugal barrier changes with cooling. With an increase in disc accretion rate \((\dot{m}_{d})\) , cooling is enhanced and we find that the shock moves in towards the black hole. With cooling, thermal pressure is reduced, and as a result, outflow rate is decreased. We thus directly correlate outflow rate with spectral state of the disc.     

Evolution of the Archean-Palaeoproterozoic Bundelkhand Massif, central India—evidence from granitoid geochemistry

The Bundelkhand massif of Archean-Palaeoproterozoic age is primarily a granite-gneiss complex. Three distinct granitoid suites have been identified within the massif hornblende granitoids, biotite granitoids and leucogranitoids, in order of decreasing age. These granitoids were emplaced in previously deformed basement consisting of gneisses, banded iron formations and other metasediments, mafic to felsic volcanics.
The granitoids exhibit a large compositional range from quartz diorite to syenogranite and show a calc-alkaline trend. They are metaluminous to peraluminous and have I-type characteristics. The SiO₂ content ranges from 49 to 77 wt%. Low K₂O/Na₂O characterizes the granitoids. The oldest hornblende granitoids have low Rb and Yb contents compared to the younger biotite granitoids and leucogranitoids. Rb/Sr values for most of the granitoids are low (< 1). K/Rb ratios range from 95 to 373 which is, in general, comparable with other calc-alkaline suites. Y/Nb ratios of the granitoids are > 1.2 which is a characteristic feature of magmas derived from sources chemically similar to island arc or continental margin basalts.
The features mentioned above coupled with concentrations of Rb, Y, Nb, Yb, Ta and Th indicate a volcanic-arc tectonic setting for the granitoids. It is proposed that the massif represents subduction-related magmatism of an ocean in the southern part of the massif (an Andean plate margin).     

Battered minipile response to low-frequency cyclic lateral loading in very dense sand

Acta Geotechnica - This experimental study investigates the response of vertical and battered minipiles to two-way symmetrical low-frequency (0.1&nbsp;Hz) cyclic lateral loading. Laboratory...     

Monitoring dual-season hydrological dynamics of seasonally flooded wetlands in the lower reach of Mayurakshi River,Eastern India

The seasonally flooded wetlands are often neglected due to their ephemeral and erratic appearance and small size, however, their hydro-ecological importance, socio-economic values are equivalent to the permanent wetlands. Using dual-season Landsat multi-spectral imagery, this study highlights a comprehensive monitoring of the hydrological dynamics of wetlands in the lower reach of the Mayurakshi River at a 14-year temporal resolution with the seasonal mode of 1987–2014 time frames. Our results demonstrate the seasonal and periodic hydrological variability of water presence frequency (WPF) in six wetland complexes defined for this study. The Hijal, Ghambira and Maldah wetland complexes are highly affected by the change of WPF, while Dwarka complex is relatively stable. The assessment of WPF change analysis showed that the method is proficient in identifying stable and physically vulnerable wetland patches and absolute loss of wetland inundation frequency resulting from various anthropogenic causes like regulation of river, dry farming practices and other integrated developmental works. The outcome of our study provides a robust basis for the fundamental hydrological and ecological studies and helpful for the conservation and management of seasonally flooded wetland resources in the tropical monsoon climate.     

Palaeocene–Eocene carbon isotopic excursion from the shallow-marine-carbonate sequence of northeast India: Implications on the CIE magnitude and geometry

The exact magnitude of the carbon isotopic excursion (CIE) for the Palaeocene–Eocene Thermal Maximum (PETM) is essential for our understanding of the carbon cycle perturbation. Global compilation of the PETM CIE magnitudes indicates that the shallow-marine inorganic carbonate could be a potential candidate to decipher the actual CIE magnitude. The present study, therefore, made an attempt to explore the thick Palaeogene shallow-marine carbonate sequence of the Sylhet Limestone exposed in the Jaintia Hills of northeast (NE) India, in terms of the preservation and magnitude of the PETM CIE. Exploratory sampling carried out across the Sylhet Limestone suggests that this sequence was deposited during the Late Palaeocene and Early Eocene, as evident from the age-diagnostic foraminifera. The observed \({\sim }3.4\permille \) CIE at the top of the Lakadong Limestone, resting above the Miscellanea miscella and Ranikothalia nuttalli foraminifera-bearing horizon, can, therefore, be correlated with the PETM CIE. Although the magnitude of the CIE from our limited data set agrees well with the global compilation, the absence of a stepped profile questions the preservation of the CIE reported elsewhere from the Tethyan sequence. Further work is needed for a better understanding of the PETM interval in NE India.     

Role of panchayat (Local self-government) in managing disaster in terms of reconstruction,crop protection,livestock management and health and sanitation measures

The Panchayati Raj Institution is a statutory body elected by the local people through a well defined democratic process with specific responsibilities and duties. It is the most appropriate institution from village to the district level. The role of Panchayats (local self governing institutions) is important in view of their proximity to the local community, universal coverage and enlisting people’s participation on an institutionalized basis. Panchayat and municipalities are local governing institutions in countries like India, have a constitutional mandate under the 73rd and 74th constitutional amendments Act. Apart from the proper implementation of different ongoing developmental programmes, the panchayat system has to play pivotal roles in respect of natural as well as man-made disaster management. In India, Particularly in West Bengal the village level Disaster Management Committee is headed by ward members of gram panchayat. The Panchayati Raj Institutions provide adequate space to the weaker section of the communities at its three levels, i.e. village, block and district. Good governance can be an instrumental feature in poverty reduction. This study was undertaken in cyclone affected areas in West Bengal to assess the role of panchayat in disaster management. The empirical study revealed that main role performed by the panchayat in respect of disaster was reconstruction of damaged houses, crop protection measures, livestock management, health and sanitation measures. Besides these broad aspects, the panchayats officials also organized health camp, involved in rescue operation, arranging temporary shelters and so on as disaster management operation. Total 60 gram panchayat officials and 150 villagers were selected randomly as respondents for the present investigation. The data were analysed into mean score, rank position and spearman correlation coefficient to achieve the objectives. The findings of the study indicated that significant differences were observed on the opinion of the villagers and officials on reconstruction of houses and health and sanitation measures. The roles performed by the local self-government in disaster management were very poor. There was absolutely lack of involvement of people’s representative. Therefore, adequate supports are suggested on these aspects from the representatives in association with higher authorities.     

Palaeocurrent and environmental implications from anisotropy of magnetic susceptibility (AMS): a case study from Talchir and Barakar formations,Raniganj Basin,West Bengal,India

Oriented cylindrical cores of rock samples were collected from the Talchir and Barakar formations of the Lower Gondwana Supergroup of the Raniganj Basin exposed in and around Kalyaneshwari and Maithon areas. The cores (2.54 cm diameter and 2.2 cm height) were studied in the low field anisotropy of magnetic susceptibility (AMS) measurement to determine the nature of magnetic fabrics, to correlate it with the sedimentological characteristics and to determine the palaeocurrent patterns. The results derived from the statistical parameters (especially the q-factor), the shapes of the susceptibility ellipsoids and directional data of the AMS indicate that the magnetic fabrics within the studied units are primary (depositional) and are correlatable form the palaeoenvironmental features. The orientation of the maximum (K₁), intermediate (K₂) and minimum (K₃) susceptibility axes is dispersed on the lower hemisphere equal area diagram rather than strong clusters which is not because of secondary (tectonic) influence but due to the moderate to high-energy environment of deposition of the sediments in the studied units. Based on the q-factor (which is 0.581 for Barakar Formation and 0.565 for Talchir Formation which are both <?0.7), it is suggested the AMS indicates that the imbrication of the K₁ axis is the indicator of palaeocurrent. Also, the magnetic foliation (average value?=?1.255) exceeds the magnetic lineation (average value?=?1.107) and the shape parameter exceeds 0 in most cases pointing towards an oblate fabric. The palaeocurrent in the present study as indicated by the K₁ axis imbrication is very similar in both the units under study and is due SW. However, apart from this precise palaeocurrent direction, there exists a certain degree of randomness of the susceptibility axes which are very clear indication of corresponding depositional environments.     

Thin Domain Walls in Lyra Geometry

This paper studies thin domain walls within the frame work of Lyra Geometry. We have considered two models. First one is the thin domain wall with negligible pressures perpendicular and transverse direction to the wall and secondly, we take a particular type of thin domain wall where the pressure in the perpendicular direction is negligible but transverse pressures are existed. It is shown that the thin domain walls have no particle horizon and the gravitational force due to them is attractive.     

Winter crop sensitivity to inter-annual climate variability in central India

India is predicted to be one of the most vulnerable agricultural regions to future climate changes. Here, we examined the sensitivity of winter cropping systems to inter-annual climate variability in a local market and subsistence-based agricultural system in central India, a data-rich validation site, in order to identify the climate parameters to which winter crops – mainly wheat and pulses in this region – might be sensitive in the future. We used satellite time-series data to quantify inter-annual variability in multiple climate parameters and in winter crop cover, agricultural census data to quantify irrigation, and field observations to identify locations for specific crop types. We developed three mixed-effect models (250 m to 1 km scale) to identify correlations between crop cover (wheat and pulses) and twenty-two climate and environmental parameters for 2001-2013. We find that winter daytime mean temperature (November–January) is the most significant factor affecting winter crops, irrespective of crop type, and is negatively associated with winter crop cover. With pronounced winter warming projected in the coming decades, effective adaptation by smallholder farmers in similar landscapes would require additional strategies, such as access to fine-scale temperature forecasts and heat-tolerant winter crop varieties.     

RETRACTED ARTICLE: Development prospects of groundwater resources in an elliptical shape island,Union Territory of Lakshadweep,India

A major problem of the islanders is the availability of fresh water for drinking purpose. Groundwater is the only source of fresh water for the islanders. The demand for groundwater is increasing very year due to growing population and urbanization. A proper understanding of the groundwater condition is important in order to meet this increasing demand and to formulate future development and management strategies. It is in this context, principal hydrogeologic units; water table fluctuation pattern, general groundwater potential, existing groundwater withdrawal structures and draft, water quality, etc. have been studied in an elliptical shape Andrott Island of Union Territory of Lakshadweep, India, through field investigation and secondary data collection. Groundwater occurs under phreatic condition and seawater is in hydraulic continuity with the groundwater as evidenced by the tidal influence in almost all the wells. Groundwater level fluctuation due to seasonal variation varies from 0 to 0.542 m depending on the distance of the well from the coast. Depth to groundwater level varies from less than 1.234 to 3.520 m depending on the topography. Groundwater level fluctuation is due to the combination of factors like rainfall, tidal activities, sub-surface runoff, and draft. Large diameter dug wells are the main groundwater extraction structures in this island. There are 2,143 dug wells with almost each family having its own well and the density of the dug wells is about 437/km². The stage of groundwater development is estimated as 37% and hence “Safe” for further groundwater development in this island. However, considering the very limited fresh-water resources and also the growing demand for groundwater, various management strategies such as rainwater harvesting, artificial recharge of groundwater, public participation in water conservation and wise use of groundwater, etc., have been suggested.