Simulations of a weakly conducting droplet under the influence of an alternating electric field

We investigate the electrohydrodynamics of an initially spherical droplet under the influence of an external alternating electric field by conducting axisymmetric numerical simulations using a charge-conservative volume-of-fluid based finite volume flow solver. The mean amplitude of shape oscillations of a droplet subjected to an alternating electric field for leaky dielectric fluids is the same as the steady-state deformation under an equivalent root mean squared direct electric field for all possible electrical conductivity ratio $(K_r)$ and permittivity ratio $(S)$ of the droplet to the surrounding fluid. In contrast, our simulations for weakly conducting media show that this equivalence between alternating and direct electric fields does not hold for $K_r \ne S$. Moreover, for a range of parameters, the deformation obtained using the alternating and direct electric fields is qualitatively different, i.e. for low $K_r$ and high $S$, the droplet becomes prolate under alternating electric field but deforms to an oblate shape in the case of the equivalent direct electric field. A parametric study is conducted by varying the time period of the applied alternating electric field, the permittivity and the electrical conductivity ratios. It is observed that while increasing $K_r$ has a negligible effect on the deformation dynamics of the droplet for $K_r<S$, it enhances the deformation of the droplet when $K_r>S$ for both alternating and direct electric fields. We believe that our results may be of immense consequence in explaining the morphological evolution of droplets in a plethora of scenarios ranging from nature to biology.Comment: 10 pages, 8 figure

Motion of an air bubble under the action of thermocapillary and buoyancy forces

A novel way to handle surface tension gradient driven flows is developed in the volume-of-fluid (VoF) framework. Using an open source Navier-Stokes solver, {\it Basilisk}, and the present formulation, we investigate thermocapillary migration of drops/bubbles in a surrounding medium. Several validation exercises have been performed, which demonstrate that the present solver is a robust one to investigate interfacial flows with variable surface tension. It is well known that it is a challenging task to numerically model the tangential and normal surface forces arising due to interfacial tension. We have shown that the present method does not require the artificial smearing of surface tension about the interface, and thus predicts the theoretical value of the terminal velocity of bubble/drop migrating due to an imposed temperature gradient very well. It is also demonstrated that the present solver provides accurate results for problems exhibiting the gravity and thermocapillary forces simultaneously, and useful for systems with high viscosity and density ratios.Comment: 30 pages, 16 figures, submitted to Computers and Fluid

Comparative Phytochemical Screening and Pharmacognostic Study on Stem Bark and Root bark of Endangered Medicinal Plant Oroxylum indicum (L.) Vent

Medicinal plants are an important component of natural resources and they are used as a source of food, medicine, fibres, tannin, gum and allied uses. Oroxylum indicum (L.) Vent. (Bignoniaceae) also known as ‘Sonapatha’ is an important endangered medicinal plants of indigenous medical system for over hundreds of years. It has been used as a single drug and as a component for preparation of ayurvedic compound preparations viz. Dashmularistha and Chyavanprash etc. Plants are used in treating in various human ailments like jaundice, dysentery, asthma, allergic disease, urticaria, sore throat, measles, laryngitis, hoarseness and diarrhea. The present paper provides a detailed account of the phytochemical evaluation and pharmacognostic studies of Sonapatha stem bark and rroot bark. The study includes macroscopy, microscopy, and powder microscopy studies, fluorescence study, physicochemical parameters, preliminary phytochemical screening High Performance Thin Layer Chromatography fingerprint profile. Established parameters can be used as standards for identification and quality control of the plants in compound formulations and also preparation of a monograph of the plant. &nbsp

An Assessment of Environmental Impact of a Prominent Contributor in Coalmining Industry of India

The mining industry plays a crucial role in supporting the economic development of nation, but on the darker side it has some undesirable impacts on environment. Being a heavy pollution causing industry and an energy supply industry, mining industry is the focus of environmental protection work. It is evident that despite the increase in Corporate Environmental Disclosure, there remains a substantial heterogeneity in terms of how corporations hold accountability for their environmental impacts. Therefore, to understand this heterogeneity in a better way, this study examines the perceived Environmental Accountability of the NCL, (a prominent contributor in coalmining industry of India), by evaluating its impact on environment from the perspective of different stakeholders

Comparison of Enriched Silvipasture and \u3cem\u3eCenchrus ciliaris\u3c/em\u3e Pasture with Natural Pasture in Ravenous Soils for Goat Production under Rainfed Conditions

Goat is a future animal and plays a crucial role in providing livelihood and supplementary income to resource poor farmers and landless labourers of rural India. Goat rearing also ensures self-employment and act as a cushion in present climate change phenomena like drought and famine. Goats are found more in ecologically fragile arid and semiarid areas. Hence, it is imperative to address goat production under present scenario of climate change and food scarcity. The diverse challenges and constraints as growing population, increasing food, feed and fodder needs, natural resources degradation, climate change demands a reorientation of our strategies for goat production and development of feed and fodder resources in the country by utilizing waste lands/ poor lands, because in our country goats are mainly depend on natural feed resources available on waste and degraded lands. The poor production potential of these lands and poor values of qualitative parameters of available vegetation on such lands hamper expression of production potential of Indian goats, side by side economic progress of goat keepers. Therefore, an attempt was made to develop feed resources under three models i.e., Silvipasture, sown pasture and natural vegetation stand (natural pasture) in Yamuna ravines of Mathura district of Uttar Pradesh

Pharmacognostic evaluation of Bilva [Aegle marmelos (L.) Correa] root bark

670-676Aegle marmelos L., family Rutaceae, is a sacred plant mentioned in various Hindu scriptures. It has both medicinal as well as cultural importance. In the present investigation, macroscopy, microscopy, and powder microscopy studies, physicochemical analysis, detection of heavy metals, analysis of aflatoxins, screening of microbiological parameters and High Performance Thin Layer Chromatography (HPTLC) fingerprint profile of methanolic extract were performed. Analysis of 04 aflatoxins (A1, B1, A2, and B2) was performed and found that no aflatoxins were present, authenticated by comparing the Rf value and colour of the standards spot with sample on TLC plate. Qualitative microbiological analysis of pathogenic bacteria, i.e., Staphylococcus aureus, Salmonella sp., Pseudomonasaeruginosa and Escherichia coli were done and found that no bacterial pathogens are present in the Aegle marmelos root bark extract. HPTLC chromatographic fingerprint of Aegle marmelos root bark was done by using mobile phase toluene: ethyl acetate: formic acid (7.5: 2.5: 0.4). TLC plate was derivatized by using derivatizing reagent 5% Methanolic - sulphuric acid reagent and plate was heated at 105°C till the bands are clearly visible. Major spots Rf values and colour were noted at 254 nm, 366 nm, after derivatization 366 nm and UV light. Therefore, established parameters may be used as a reference tool for proper recognition and confirmation of right plant material and monitoring of batch to batch consistency of finished herbal products using Aegle marmelos as an ingredient. This study may also helpful in the preparation of Aegle marmelos root bark monograph

ASH LAYERS FROM SOUTH ANDAMAN SEA: PROBABLY SOURCED FROM TOBA CALDERA

Deep Sea sediment core PC-1 from the South Andaman Sea (7 ̊19.85' N; 94 ̊ 39.26' E; in East Andaman Basin) below the water depth of 3144 m contain discrete ash layers at various depths. According to morphological study, these ash layers contain glass shards of different varieties i.e. Type-I, Type-II, Type-III, Type-IV and Type-V and it is comparable to glass shards of Toba volcanic reported from other parts of the world. This observation is also supported on the basis of relative biostratigraphic datum observed in the core PC-1. The Layer-A (56 cm thick) at 210 cm bsf is just above the biostratigraphic datum of ca. 0.12 Ma, correspond to Youngest Toba Tuff (YTT), followed by Layer-C belongs to Middle Toba Tuff (MTT) and Layer-D inferred as Oldest Toba Tuff (OTT). This interpretation is further supported by the geochemical data obtained from the EDX analysis, which suggest high silica and alkali contents of rhyolitic composition. Hence, geochemical composition, morphology and biostratigraphic data of these discrete tephra layers show identical characteristics to the products of Toba eruptions, including YTT, MTT and OTT