Thermodynamic studies of different black holes with modifications of entropy

In recent years, the thermodynamic properties of black holes are topics of interests. We investigate the thermodynamic properties like surface gravity and Hawking temperature on event horizon of regular black holes viz. Hayward Class and asymptotically AdS (Anti-de Sitter) black holes. We also analyze the thermodynamic volume and naive geometric volume of asymptotically AdS black holes and show that the entropy of these black holes is simply the ratio of the naive geometric volume to thermodynamic volume. We plot the different graphs and interpret them physically. We derive the ‘cosmic-Censorship-Inequality’ for both type of black holes. Moreover, we calculate the thermal heat capacity of aforesaid black holes and study their stabilities in different regimes. Finally, we compute the logarithmic correction to the entropy for both the black holes considering the quantum fluctuations around the thermal equilibrium and study the corresponding thermodynamics.     

Distinguishing Developing Versus Non-Developing African Easterly Waves Using Adaptive Observational Strategies

The impacts of dust loaded, Saharan Air Layer (SAL) during the life cycle of African Easterly Waves (AEWs) is a many-faceted scientific problem. It entails possible radiative effects of dust aerosols, impacts of dust on cloud physics, and the cloud nuclei of condensation, advective effects, that is, intrusions of dry dusty air versus humid air into the interior of storms. This paper addresses several such AEWs of the eastern Atlantic Ocean, where we have made use of special aircraft reconnaissance data sets that include wind and humidity profiles in the vertical. Using what are called adaptive observational strategies within a mesoscale model, we show the impacts of adding such observations in the analysis and in short-range forecasts of several AEWs. We do not have the direct and indirect effects of aerosols, but we do include the advective component. Our results show that the inclusion of humidity profiling distinguishes between developing versus nondeveloping AEWs from the use of these additional data sets via the adaptive observational strategies.     

Universe bounded by event horizon: a non equilibrium thermodynamic prescription

The present work deals with universe bounded by the cosmological event horizon as a thermodynamical system which is irreversible in nature. Using non equilibrium thermodynamical approach the entropy variation on the event horizon has been evaluated. The additional term in the entropy variation depends on the irreversible process parameter. Finally, two dark energy models are presented and results are analyzed.     

Seasonal distribution of cadmium among components of sewage treatment ponds: an eco-tech for heavy metal remediation

The study was designed to quantify cadmium accumulation in different components of sewage treatment ponds during different seasons and to assess risk for human consumption perspective. The study estimated cadmium concentration in water, sludge, Eichhornia, plankton and tilapia fish from anaerobic, facultative, maturation-1 and -4 ponds during pre-monsoon, monsoon and post-monsoon periods. It resulted that cadmium accumulated among different components of anaerobic, facultative, maturation-1 and -4 ponds ranging 0–18, 0–10, 0–7 and 0–15.4 ppb, respectively. During monsoon, highest accumulation was observed in tilapia in both facultative and maturation ponds, but during post-monsoon, plankton community showed highest value in all. The highest bio-magnification of cadmium was recorded during monsoon with varying degrees (facultative pond: 4.39, maturation pond-1: 3.03 and maturation pond-4: 7.08). Cadmium concentration in tilapia lied within WHO’s safe level and may be recommended for human consumption. The concentration of cadmium was estimated by Flame Atomic Absorption Spectrophotometer. The above findings occurred due to chelation, adsorption and sedimentation, absorption and bio-accumulation, ionization, leaching through sediment and rainfall. Water pH (6.7–8.8), dissolved oxygen (0–17 mg L^?1), total solids (251–650 mg L^?1), iron (Fe²⁺) concentration (0.61–4.87 mg L^?1) and sedimentation rate (278.9–2,409.6 g day^?1 m^?3) were conducive for the distribution of cadmium into different ecosystem components of treatment ponds. These ponds reclaimed 28.57–61.11 % of sewage-cadmium and may be promoted as a low-cost eco-tech for sewage treatment.     

Groundwater chemistry and redox processes: Depth dependent arsenic release mechanism

Patchy occurrences of elevated As are often encountered in groundwater from the shallow aquifers (<50 m) of the Bengal Delta Plain (BDP). A clear understanding of various biogeochemical processes, responsible for As mobilization, is very important to explain this patchy occurrence and thus to mitigate the problem. The present study deals with the periodical monitoring of groundwater quality of five nested piezometeric wells between December 2008 and July 2009 to investigate the temporal changes in groundwater chemistry vis-a-vis the prevalent redox processes in the aquifer. Geochemical modeling has been carried out to identify key phases present in groundwater. A correlation study among different aqueous redox parameters has also been performed to evaluate prevailing redox processes in the aquifer. The long term monitoring of hydrochemical parameters in the multilevel wells together with hydrogeochemical equilibrium modeling has shown more subtle differences in the geochemical environment of the aquifer, which control the occurrence of high dissolved As in BDP groundwater. The groundwater is generally of Ca-HCO₃ type. The dissolved As concentration in groundwater exceeded both WHO and National drinking water standard (Bureau of Indian Standards; BIS, 10 μg L⁻¹) throughout the sampling period. The speciation of As and Fe indicate persistent reducing conditions within the aquifer [As(III): 87-97% of As_T and Fe(II): 76-96% of Fe_T]. The concentration of major aqueous solutes is relatively high in the shallow aquifer (wells A and B) and gradually decreases with increasing depth in most cases. The calculation of SI indicates that groundwater in the shallow aquifer is also relatively more saturated with carbonate minerals. This suggests that carbonate mineral dissolution is possibly influencing the groundwater chemistry and thereby controlling the mobilization of As in the monitored shallow aquifer. Hydrogeochemical investigation further suggests that Fe and/or Mn oxyhydroxide reduction is the principal process of As release in groundwater from deeper screened piezometric wells. The positive correlations of U and V with As, Fe and Mn indicate redox processes responsible for mobilization of As in the deeper screened piezometric wells are possibly microbially mediated. Thus, the study advocates that mobilization of As is depth dependent and concentrations of As in groundwater depends on single/combined release mechanisms.     

Estimation of crustal discontinuities from reflected seismic waves recorded at Shillong and Mikir Hills Plateau,Northeast India

In this study, an attempt is made to determine seismic velocity structure of the crust and upper mantle beneath the Shillong-Mikir Hills Plateau in northeast India region. The principle of the technique is to relate seismic travel times with crustal thickness above the Conrad and Moho discontinuities. Broadband digital waveforms of the local earthquakes make a precise detection of the seismic phases possible that are reflected at these discontinuities. The results show that the Conrad discontinuity is at 18–20 (±0.5) km beneath the Shillong-Mikir Hills Plateau and the Moho discontinuity is at 30 ± 1.0 km beneath the Shillong Plateau and at 35 ± 1.0 km beneath the Mikir Hills.     

Resolution of multiple sheet-type structures in self-potential measurement

The resolution of self-potential anomalies due to closely spaced multiple sheet-like bodies by the potential difference and potential gradient is studied in this paper. Self-potential anomalies due to several synthetic models were inverted through a very fast simulated annealing (VFSA) global optimization. Increase in depth to the top, polarization constant and depth extent of the body decreases resolution at a particular target separation. It has been observed that depth to the top and separation between two targets play an important role in the resolution. Vertical sheets at equal depth can be resolved in the potential difference measurement only if they are separated by at least four times their depth, while they can be resolved in the gradient method, if they are separated by twice the depth. Resolution using potential difference becomes more difficult for dipping sheets, although the potential gradient method can resolve them efficiently. Efficacy of potential gradient data in the inversion is demonstrated in the study using synthetic data as well as field measurement from South Purulia Shear Zone related with uranium investigation.     

An approach to an integrated micro-watershed management plan of outer Himalayan range of Himachal Pradesh, India

Due to the ever-increasing demand on water resource, the pressure on its judicious utilization is also increasing. Besides being precious, this resource is also complex to manage on account of its dynamic behaviour. In India emphasis is being placed on making the local-level users participate in the management of natural resources at the watershed level. Therefore, it is imperative that local-level organizations be strengthened by providing the integrated watershed management tools which are user-friendly, but still use all the scientific knowledge to arrive at the appropriate decisions. This paper demonstrates the use of GIS-based overlay method for local-level planning, incorporating the sustainability aspects of watershed development. A case study has been taken in the Lower Bhangal Micro-watershed of the outer Himalayan range to demonstrate the approach of matrix/ranking and overlay methods to delineate priority areas for watershed management plan.     

Subcrop Gondwana of Bengal basin and their reservoir characteristics

In Bengal basin the subcrop Gondwana sediments occur in N-S trending elongated grabens originated largely by the graben forming tectonisms of the Gondwanaland which overlie the crystalline basement in the sub-surface in an intra-cratonic setup. So far five wells in shelf part of Bengal Basin have penetrated Gondwana sediments, out of which three wells i.e.,G1, G3 and G2 have been drilled up to Precambrian basement. In subcrop Gondwana graben, glacial to glacio-fluvial Talchir Formation of Early Permian age was deposited above the basement. Early Permian Barakar Formation overlies Talchir Formaion. Flood basin model of deposition is postulated for this coal rich unit. In the absence of Barren Measure Formation, coal bearing Raniganj Formation overlies Barakar Formation. The fluvial set up changed over to arid environment during deposition of Panchet/Supra Panchet Formation (undifferentiated). The deposition of Panchet Formation is followed by eruption of doleritic rocks in both subcrop and outcrop Bengal Gondwana whereas lamprophyres are absent in subcrop of Bengal Gondwana. Rifting as well as pull-apart basin model due to transtensional movement is postulated for Gondwana basins. Detailed lithostratigraphic analysis of the core / cutting samples of the Gondwana sediments reveal that the sediments are mainly fine to coarse grained, poorly sorted sandstone. These sediments are characterized as poor reservoir and needs some treatment for permeability enhancement for hydrocarbon production.     

Solution of the equation of transfer with Rayleigh's phase function in a thin atmosphere

The equation of radiative transfer with scattering according to Rayleigh's phase function has been solved in a thin atmosphere by use of a modification of the spherical-harmonic method suggested by Wanet al. (1986).