R Nagarajan

A common spice, Syzygium aromaticum is widely known as clove; this is the flower bud of a tree that belongs to the Myrtaceae family. With its origin in Indonesia, it has found application in medicine in Asian and western countries. It has taken a prominent place in alternative medicine and as a food flavoring agent. The clove buds contain several compounds of interest, such as eugenol, eugenyl acetate, trans-caryophyllene, β-caryophyllene, polyphenols, tannins, and triterpenoids. These rich bioactives make it a sought-after home remedy for illness from dental complications to inflammation of several kinds. The active compounds have been effectively extracted using solvents such as water, ethanol, and methanol. These compounds contribute to the fragrance and antioxidant, antibacterial, and antifungal properties, which underpin its enormous applications in the food and flavoring industries. Despite these beneficial properties, they may elicit some adverse reactions when administered at higher concentrations. Clove buds and their extracts containing active compounds, or the standalone compounds such as eugenol and oleoresins, have been approved by the Food and Drug Administration (FDA) as a food additive. The phenolics-rich fraction of clove has been reported to show no adverse effects on Wistar rats at 1000mg/kg body weight/day. A few research reports are indicative of the extract affecting the reproductive indices in animal models. However, the studies related to the toxic exposure of clove extracts are limited due to the highly variable nature of the sources and their constituents extracted thereafter. This work discusses the toxicity of different types of clove extracts.

The present work describes an investigation of the effect of 3 different parameters of laser surface alloying-i.e., laser scanning speed (LSS), nozzle stand-off distance (NSOD) and laser beam scan-off distance (LBSOD) on coating height, depth and width. Nickel-based Colmonoy 88 alloy powder has' been deposited on 13Cr-4Ni steel by single-step process of laser surface alloying. Laser power and powder feed rate were maintained at 3kW and 25 g/min, respectively. L8 orthogonal array has been designed to study these 3 parameters at 2 levels each. The results of single pass with extent of dilution, surface hardness and microstructures produced by different conditions are presented and discussed. For a specified NSOD and LBSOD, there was a decrease in coating height and depth with increase in LSS. Coating height and depth were not affected much by increase in NSOD. From the present investigation, optimized parameters were identified for enhanced hardness, minimum dilution and desired coating height and coating depth.

Coal is the one of the world's most abundant fossil fuel resources. It is not a clean fuel, as it contains ash and sulfur. SOx as a pollutant are a real threat to both the ecosystem and to human health. There are numerous de-sulfurization methods to control SO2 emissions. Nowadays, online flue gas de-sulfurization is being used as one such method to remove sulfur from coal during combustion. The biggest disadvantage associated with this method is formation of by-products (FGD gypsum). A way for effective usage of FGD gypsum has not yet been found. This will lead to acute and chronic effects to humans as well as plants. Power ultrasound can be used for the beneficiation of coal by the removal of sulfur from coal prior to coal combustion. The main effects of ultrasound in liquid medium are acoustic cavitation and acoustic streaming. The process of formation, growth and implosion of bubbles is called cavitation. Bulk fluid motion due to sound energy absorption is known as acoustic streaming. In addition, coupling of an acoustic field to water produces OH radicals, H 2O2, O2, ozone and HO2 that are strong oxidizing agents. Oxidation that occurs due to ultrasound is called Advanced Oxidation Process (AOP). It converts sulfur from coal to water-soluble sulphates. Conventional chemical-based soaking and stirring methods are compared here to ultrasonic methods of de-sulfurization. The main advantages of ultrasonic de-sulfurization over conventional methods, the mechanism involved in ultrasonic de-sulfurization and the difference between aqueous-based and solvent-based (2 N HNO3, 3-volume percentage H2O 2) de-sulfurization are investigated experimentally. © 2010 Elsevier B.V.

The present study is focused on fabrication of high-purity submicrometer alumina ceramic particles (predominantly in sub-100 nm range) from micrometer-sized feed (e.g., 70-80 μm) using sonofragmentation. The effects of various parameters such as ultrasonic frequency, feed concentration, sonication time, surfactant, and applied ultrasonic power on sonofragmentation were investigated. Sub-100 nm particle production by sonofragmentation was validated via three metrics, i.e., laser particle size analysis, high-resolution transmission electron microscopy, and turbidimetry. There is a significant change in color and shape of alumina ceramic particles as a result of sonofragmentation. Higher size reduction ratios are obtained at lower frequencies and at higher input power. Submicrometer particle generation increases as concentration of the feed particles increases, indicating that attrition by interparticle collision is a significant mechanism. The shape of the particles changes from angular to spherical as sonofragmentation time increases. Probe-type sonication produces fragmentation effects that are less uniform than those induced by tank-type ultrasonics. Surfactant plays a significant role in preventing agglomeration, especially as finer fragments are produced with prolonged sonication. © 2008 IEEE.

To illustrate the concept of the inter-dependence between multicomponent chemical reactions and transport phenomena, a theoretical investigation of a halogen-cycle tungsten filament incandescent lamp was undertaken based on local thermochemical equilibrium (LTCE) coupled with Fickian and thermal (Soret) transport of species. Deposition of tungsten on the bulb wall leads to 'bulb blackening', resulting in reduction in the luminous efficiency of the lamp, a problem typically combated by addition of small amounts of halogen and oxygen. Utilizing temperature-dependent Soret diffusion factors, elemental fluxes were analyzed. Zero element flux (ZEF) maps were generated based on temperature-dependent Soret diffusion factors. The element solubilities and the filament-to-wall element segregation were found to be strongly dependent on the bulb wall temperature, oxygen fill pressure and Soret diffusion factors. Transport-affected shifts in element solubilities from pure LTCE condition were studied. Implications of this study for the modelling of nano-scale CVD processes are highlighted. © The Electrochemical Society.

The effects of ash particle physical properties and transport dynamics on the erosive wear of three different grades of low alloy steel, using three different power-station ash types, were determined in this study through experimental investigation. The study used a Taguchi fractional-factorial L27 DOE. The experimental data were used to derive a model for the prediction of erosion rates. The model incorporates the properties of the ash particles and the target metal surface, as well as the characteristics of ash particle motion in the form of the impingement velocity and the impingement angle. Given the availability of large number of experimental data, it became possible to predict the relationship between erosion loss and the factors influencing the rate of room-temperature erosion. Fly-ash particulate size and concentration, moisture and titania content, impact velocity and angle, duration of impact, and alloy surface roughness were determined to be first-order effects. © 2009 Elsevier B.V. All rights reserved.

Gas bubbles introduced into a liquid in the mixing chamber help to break up the liquid into fine droplets on being expanded to the ambient pressure. The passage of gas bubbles through the orifice of the nozzle requires that the size of the bubbles be much smaller than the diameter of the orifice. In the present work, the effectiveness of 20. kHz ultrasound to increase number density of fine bubbles within the mixing chamber of an effervescent atomizer by breaking up bubbles introduced in it by an aerator was investigated. Bubbles of initial size in the range of 5-10. mm were shown to get disintegrated into clusters of micron and sub-micron sized bubbles. A fine spray was produced in the presence of ultrasound at a gas-to-liquid mass flowrate ratio (GLR) of 0.063%. The half-cone angle of spray was in the range of 6-10°, which compares favorably with conventional atomizers. The experimental findings of bubble breakup were theoretically modeled by the Rayleigh-Plesset equation. The results of the model indicate that bubbles having initial radius less than 3. mm undergo growth and subsequent disintegration at 20. kHz for the given acoustic pressure of 0.3. MPa. © 2011 Elsevier B.V.

In this experimental work, three different types of nanofluids were evaluated for their stability using dynamic light scattering and particle morphological study using scanning electron microscopy. The nanofluids used in this study are zinc oxide (ZnO) nanoparticle in water and 5 wt% polyvinylpyrrolidone (PVP) as a dispersant, and ZnO with polyethylene glycol (PEG 600) and CuO with PEG 600 with 5 wt% PVP at different concentration of 0.1, 0.3 and 0.5 wt%. Thermal and electrical conductivities were determined by KD-2 Pro® and PC 700 Eutech®. The result shows better enhancement in the thermal and electrical conductivity in the ZnO+PVP+Water system, followed by the CuO+PVP+PEG and ZnO+PEG systems. The highest percentage enhancement in thermal conductivity found to be 35.5% of ZnO+ PVP+water systems. The thermal conductivity results were compared with a theoretical model and show good agreement with results predicted by the model. The proposed model of Nan et al. (1997) is based on a hypothesis regarding the physical mechanism in heat transfer for nanofluids. This study is expected to form the basis for the development of nanofluid-based technologies with PEG as the primary additive in the upstream oil and gas industry especially in gas hydrates and drilling technology.

The Mentha arvensis essential oil, due to its poor aqueous solubility and the lack of a proper formulation, has found very limited clinical use. In this study, Mentha oil nanoemulsion was formulated using ultrasonication of Mentha oil with tween 80 and water, and its role as a potential anticancer and antibacterial agent was evaluated. Surfactant concentration and emulsification time play an important role in optimization of nanoemulsions. A clear and stable nanoemulsion (M3C) with a droplet diameter in the nanometric range was obtained in a sonication time of 20 min. The anticancer activity of the nanoscale-based Mentha oil emulsion was evaluated by various cell culture techniques including MTT, colony formation assay, and Annexin V apoptotic assay. The result of Annexin V-FITC assay, marker of apoptosis, clearly displays the induction of early apoptosis in anaplastic/aggressive thyroid cancer cell line (HTh-7). Also, M3C demonstrated antibacterial activity against Staphylococcus aureus (ATCC 29213). In addition, interaction of M3C with the pathogen caused structural changes in the lipid cell membrane of pathogen, with increased leakage of cytoplasmic contents as assessed through the absorbance value of 260 nm. Agar well diffusion, along with membrane integrity analysis, also validated the antimicrobial activity. The results of this translational research are expected to substantiate the potential for use of Mentha oil in therapeutic studies, as well as in anticancer and antibacterial therapy.