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Purpose The study aims to assess the heater and cooler positional impacts systematically using four different quadrantal cavities filled with hybrid nanofluid, keeping the curved surface adiabatic under the orientated magnetic fields. Both heat transfer and entropy generation analyses are performed for a hybrid nanofluid flow in a quarter circular cavity considering different orientations of magnetic fields. The investigation is focused to assess the heater and cooler positional impacts systematically using four different quadrantal cavities (first to fourth quadrantal cavities), keeping the curved surface always adiabatic. The impacts of pertinent variables like Rayleigh number, Hartmann number and volumetric concentration of hybrid nanofluid on heat transfer characteristics are in consideration with the second law of thermodynamics. The analysis includes the thermal, viscous and magnetic aspects of entropy generation. Design/methodology/approach After validating against the experimental results, the present work explores numerically following the Galerkin weighted finite element technique. The solution is obtained through an iterative process satisfying the convergence limit of 10−8 and 10−10 for the maximum residuals and the mass defect, respectively. Findings It revealed that the mutual exchange of heater-cooler positions on the adjacent straight edges of the quadrant cavity does not have any impact on the flow direction. Although the magnitude of flow velocity enhances, the sidewall plays a decision-making role in the formation of a single circulation vortex. It also shows that thermal entropy production is the main cause behind thermodynamic irreversibility. The second or third quadrantal arrangement could have been opted as the best configuration of the heater-cooler position for achieving superior heat transfer. The Lorentz force plays a great role to moderate the heat transfer process. The maximum entropy generation is located, as expected, at the heating-cooling junction point. Research limitations/implications There are plenty of prospects for extension of the present research concept numerically or experimentally, adopting three-dimensional analysis, working fluids, boundary conditions, etc. In fact, the study could be carried out for unsteady or turbulent fluid flow. Practical implications As the position of the heated source and cold sink on the enclosure geometry can significantly alter the thermo-fluid phenomena, this kind of analysis is of utmost relevance for the further development of efficient heating/cooling arrangements and proper management of the devices subjected to magnetic field applications. This original contribution could be a potentially valuable source for future research and exploration pertaining to a thermal system or device, like heat exchangers, solar collectors, thermal storage, electronic cooling, food and drying technologies and others. Originality/value In the literature, an inadequate number of works have focused on a quadrantal cavity, mostly considering the first quadrant of the circle. However, during practical applications, it is possible that the cavity can take the shape of the other three quadrants too, and the corresponding knowledge on relative performance is still missing. Furthermore, the present investigation includes the existence of magnetic fields at various orientations. The impact analysis of this field-induced Lorentz force on the nanofluid thermal performance is another major contribution from the present work that would enrich the domain knowledge and could be useful for thermal system engineers.

Exact analytical solutions have been obtained for conduction heat transfer in a long rod or duct, having cross section of a semi-ellipse, using the “elliptic-cylindrical coordinate system”. Results are presented for two possible cross-sectional configurations of the rod: in one case, the cross section is bounded by a semi-ellipse with the straight edge aligned with the major axis, whereas, in other case, it is bounded by a semi-ellipse with the straight edge coincident with the minor axis. Expressions of temperature distribution, heat flux and heat line are determined for constant wall temperature as well as constant heat flux boundary conditions. The analytical results are illustrated graphically to highlight the salient physics associated with the problem. Apart from the analytical results, the “bivariate Chebyshev collocation spectral method” has been used to determine the numerical solution of the problem of heat conduction in the semi-elliptical geometries; numerical results are found to be consistent with the analytical expressions. The study opens up avenues for obtaining exponentially accurate numerical solution of energy equation in complex elliptic geometries using Chebyshev spectral method.

Wetlands provide numerous ecological and economic services to mankind. The soils of wetlands are one of the largest sinks of carbon (C) among the terrestrial ecosystems and can play an important role in offsetting the emission of C as a greenhouse gas (GHG) to the atmosphere. India is bestowed with enriched wetland ecosystems that support diverse and unique habitats. The potential of the wetlands in terms of C capture and sequestration has not been quantified. Therefore, in the present paper, an assessment of C capture from different sources and its ultimate deposition in soils leading to sequestration has been done in three different types of wetlands, one created sewage-fed and two natural floodplain oxbow lakes, in the West Bengal state of India. Multiple seasonal sampling of water, macrophytes, and soil was done to assess the primary productivity, dissolved C, and deposition of C in soils of the wetlands in comparison to reference upland sites. All these wetlands are productive ecosystems as indicated by the physicochemical parameters of water and soil. The quantity of C accumulated up to 0.3 m depth in the oxbow lakes was to the tune of 144–166 Mg/ha, which was 3.43–4.78 times higher than that in the corresponding reference upland sites. In the sewage-fed wetland, the C accumulation estimated as 50 Mg/ha was 1.27 times higher than its corresponding upland site. So, the wetland ecosystems, particularly the floodplains, are highly efficient in accumulating C in their soils and thus can somewhat negate the GHG emission.

Anthropogenic and climatic changes are continuously altering the freshwater plankton, necessitating an evaluation of the complex structure of plankton communities to understand and mitigate these impacts. In this context, the present study focuses on evaluating the structure of plankton communities, specifically Phytoplankton Functional Groups (FGs) for assessing the environmental sensitivity of wetlands under changing scenario. These FGs are defined by shared adaptive features rather than taxonomic traits. Over the period from 2016 to 2018, two ecologically distinct wetlands were examined, analysing their phytoplankton FGs and their relationship with water quality parameters. Ecohydrological data revealed significant seasonal variations ( p  ≤ 0.05) in key parameters such as water depth, temperature, pH, electrical conductivity, dissolved oxygen, total alkalinity, total hardness, NO 3 -N, and PO 4 -P. Notably, there were no significant differences observed among the sampling stations within each wetland. A total of 125 phytoplankton genera/species were classified into 23 FGs in the open wetland and 22 FGs in the closed wetland. Spatial and seasonal analyses of dominant FGs suggested both wetlands were experiencing pollution pressures. This study highlights the powerful role of phytoplankton functional groups (FGs) as bioindicators of wetland health, uncovering pollution pressures. In open wetlands, 15 phytoplankton FGs with 36 key taxa (Indicator Value ≥ 40%) emerged as critical indicators, while in closed wetlands, only 10 FGs with 17 taxa were identified. To assess eutrophication, the occurrence of these indicator species was evaluated using BVSTEP function analysis. The study recommends pollution reduction in catchment areas and restoration of riverine connectivity to enhance FG diversity. Phytoplankton FG methodologies are deemed effective for assessing the environmental sensitivity of wetlands significantly impacted by human activities. This research offers a scientific foundation for the evaluation and restoration of wetland ecosystems. Highlights Phytoplankton functional groups (FGs) serve as precise bioindicators of wetland environmental sensitivity and pollution pressures. Seasonal and spatial assessments of water quality reveal insights into wetland ecological health. The response of phytoplankton FGs to environmental factors effectively indicates water quality. Key plankton species were identified as indicators of wetland ecological sensitivity.

Diseases are the most significant constraint to the sustainable growth of aquaculture. Therefore, surveillance for aquatic animal diseases is essential for early detection of diseases which is important for management of endemic diseases and eradication or containment of exotic or emerging diseases. Often, many disease incidences in aquaculture go unreported due to unavailability of the field-level disease reporting mechanism. Therefore, there is a necessity of a mechanism that can connect farmers, field-level officers and fish health experts for strengthening the farmer-based disease reporting. Keeping the same in consideration, for improving the reporting of aquatic animal diseases in the country, an android-based GPS-enabled mobile application named as ‘ReportFishDisease (RFD)’ has been developed. Using the RFD app, the farmers can report incidence of disease in finfish, shrimps and molluscs on their farms to the field level-officers and fish disease experts as and when required, and get timely scientific advice for efficient management of diseases. The data regarding the diseases is being stored on temporal and spatial scale and can be used for mapping the disease cases. It is expected that the app would help in improving farmer-based reporting, getting scientific advice and reducing losses due to diseases.

Background Hemibagrus punctatus (Jerdon, 1849) is a critically endangered bagrid catfish endemic to the Western Ghats of India, whose population is declining due to anthropogenic activities. The current study aims to compare the mitogenome of H. punctatus with that of other Bagrid catfishes and provide insights into their evolutionary relationships. Methods and Results Samples were collected from Hemmige Karnataka, India. In the present study, the mitogenome of H . punctatus was successfully assembled, and its phylogenetic relationships with other Bagridae species were studied. The total genomic DNA of samples was extracted following the phenol–chloroform isoamyl alcohol method. Samples were sequenced, and the Illumina paired-end reads were assembled to a contig length of 16,517 bp. The mitochondrial genome was annotated using MitoFish and MitoAnnotator (Iwasaki et al ., 2013). A robust phylogenetic analysis employing NJ (Maximum composite likelihood) and ASAP methods supports the classification of H. punctatus within the Bagridae family, which validates the taxonomic status of this species. In conclusion, this research enriches our understanding of H. punctatus mitogenome, shedding light on its evolutionary dynamics within the Bagridae family and contributing to the broader knowledge of mitochondrial genes in the context of evolutionary biology. Conclusions The study’s findings contribute to a better understanding of the mitogenome of H . punctatus and provide insights into the evolutionary relationships within other Hemibagrids.

The magnificent shrimp, Ancylomenes magnificus (Bruce, 1979), is a sea anemone associated marine ornamental organism exploited from Indo-Pacific waters, for the marine aquarium trade, as it has attractive coloration. However, there are no reports available yet on its population and reproductive characteristics (population structure, length–weight relationship, fecundity, sexual dimorphism, sex ratio and maturity stages). The present investigation provides information for the first time on the population and reproductive parameters of A. magnificus. In this study, a total of 158 individuals were collected from the intertidal regions of the Gulf of Mannar, Tamil Nadu, India from August 2021 to April 2022, out of which 61.4% (97 individuals) were females and 38.6% (61 individuals) were males. The estimated mean size (CL ± SD) of females was 4.93 ± 0.78 mm, while that of males was 3.22 ± 0.56 mm. The estimated mean body weight was 0.091 and 0.219 g in males and females, respectively. The study indicated strong sexual dimorphism in this species and considerable variation appeared in the carpus and chela of the second major pereopod, carapace and total length. The carapace length and weight showed a negative allometric relationship with a significant coefficient. Fecundity was relatively lower and embryo volume increased with size groups. Interestingly, the study revealed year-round breeding activity with a peak in the post-monsoon (January to March) and monsoonal period (October to December) for this species. The present investigation provides the first baseline information on the population and reproductive parameters of A. magnificus.

Thirty polymorphic microsatellites were developed and characterised for the aquaculture important species, Green chromide, Etroplus suratensis through Illumina Sequencing with a mean read quality (Phred score) of 35.8 and the microsatellite primers were designed from the sequenced information, considering various attributes such as the number of repeats, Tm, GC content, Product size, etc. using the software PRIMER 3.0 web tool. The allele numbers ranged from 6 to 18. The mean observed heterozygosity was 0.745 and the mean expected heterozygosity was 0.762. The average PIC value for 30 microsatellite primers was 0.80 and all the loci had PIC values > 0.75. The identified polymorphic loci would help in revealing the genetic stock identification among the Pearlspot population.

Eutrophication level in lakes and reservoirs depends on both internal and external phosphorus (P) load. Characterization of sediment P fractionation and identifying the P pollution sources are important for assessing the bio-availability of P and the dominant P source, for effectively controlling the water pollution. For determining the availability and sources of sediment P and eutrophication status, spatio-temporal variation in different P fractionation of sediment of hyper-eutrophic Krishnagiri reservoir, Tamil Nadu, India, was investigated. Sediment average total P (TP) content ranged from 4.62 to 5.64 g/kg. Main phosphorus form was the inorganic P (IP), and it makes up to 73.4–87.7% of TP. Among the different P fraction, viz. calcium bound (Ca-P), iron bound (Fe–P), aluminium bound (Al-P), exchangeable (Ex-P) and Organic-P (Org-P), Ca-P was the dominating fraction in both IP and TP. Trend of IP fraction was as follows: Ca-P > Fe–P > Al-P > Ex-P in pre-monsoon season, Fe–P > Ca-P > Al-P > Ex-P in monsoon and Ca-P > Al-P > Fe–P > Ex-P in post-monsoon. Overall the trend was as follows Ca-P > Fe–P > Al-P > Org-P > Ex-P. Bio-available-P (BAP) fractions ranged from 35.2 to 64.0% of TP, indicating its comparative higher value. Pearson’s correlation matrix revealed that there was strong correlation among the different P fractions. Factor analysis indicates that different fractions of P were the dominating factor than the other sediment parameters. The observed variation in sediment P fractionation indicate the differences in source and characterization of P which is very helpful for implementation of effective management practices in controlling pollution that arises due to phosphorus in this hyper-eutrophic reservoir.

The Navier–Stokes equations have been solved to derive the expressions of the velocity distributions for two cases: (1) oscillatory flows inside and outside of an axially oscillating cylindrical pipe, and (2) oscillatory flow inside an axially oscillating cylindrical annulus. In both the cases, in addition to the exact expressions for the velocity profiles, particular emphasis has been given for the determination of approximate velocity distributions for the high frequency and low frequency or quasi-static limits. It is shown that, for sufficiently large value of an appropriate frequency parameter, the velocity distribution inside the axially or longitudinally oscillating cylindrical annulus can be approximated as a superposition of the velocity distribution inside an axially oscillating cylindrical pipe of radius R ¯ o and the velocity distribution outside an axially oscillating cylindrical pipe of radius R ¯ i , where R ¯ i and R ¯ o are the inner and outer radii of the axially oscillating annulus, respectively.