Enhancement of ferroelectric and piezoelectric characteristics in europium substituted SrBi2Ta2O9 ferroelectric ceramics

Europium substituted samples of compositions Sr_1 − xEu_xBi₂Ta₂O₉ were synthesized by solid-state reaction method. The prepared samples were characterized for their structural and electrical properties. X-ray analysis confirms the formation of the single-phase layered perovskite structure. The microstructural studies reveal that the average grain size increases with increase in Eu content. An increase in remanent polarization and d₃₃ values with increasing concentration of europium has been observed. The maximum 2P_r ~ 14 μC/cm² is observed in the sample with x = 0.20. The observed results have been discussed in terms of contribution from the cation vacancies introduced into the lattice structure due to donor doping.     

Novel applications of solid and liquid formulations of nanoparticles against insect pests and pathogens

Nanoparticles are of special interest because of their markedly different physico-chemical properties than their bulk counterparts. This review covers the use of these novel agents to combat real life agricultural and medical issues important to Indian subcontinent. Nanoparticles of oxides like SiO₂ produced and characterized in our laboratory were tested against insect pests and pathogens. Nanosilica against insect pests shows nearly 100% mortality. Survivability of grasserie afflicted silkworm increased from 0% to 30% with hydrophobic nano-aluminosilicate. Treatment of multi-drug resistant tuberculosis with nanosilver and trypanosome infected mice with Dsethvasan showed significant protection. Sporulation and growth of fungi were inhibited by nanosulfur.     

Computational fluid dynamics (CFD) modeling of an electrical heating oven for bread-baking process

Radiation is the most dominant heat transfer mode in an electrical heating oven. A 3D CFD model for an electric heating baking oven was developed. Three different radiation models namely, discrete transfer radiation model (DTRM), surface to surface (S2S) and discrete ordinates (DO) were employed for the simulation of the electrical baking oven. All models predicted almost similar results, which tallied well with the experimental measurements. During the full heating cycle, the oven set-point temperature was reached after 360 s. Lower temperature zones occurred near oven wall due to lower air flow. Based on preliminary evaluation of applicability, the DO radiation model was selected for bread baking simulation and validated with the experimental measurement of bread temperature. Bread simulation was carried out to study the profiles of temperature and starch gelatinization of crust and crumb of the product. This study indicated the baking process to be complete at 1500 s when the temperature of bread-center reached 100 °C.     

Effect of Whey Protein Concentrate on the Rheological and Baking Properties of Eggless Cake

Effect of substitution of wheat flour with whey protein concentrate (WPC) at the level of 10, 20, and 30% as an egg replacer and its influence on physical properties of cake batter and quality characteristics of eggless cake were studied. The apparent viscosity of the eggless cake batter decreased with the increase in the level of WPC. The evaluation of eggless cake batter for density showed that incorporation of WPC decreased the batter density. The photomicrographs of eggless cake batters with WPC showed an increase in number of air cells and even distribution when compared with the control indicating lighter batter. Eggless cake with 20% WPC was rated the best.     

Light-activated nanotube-porphyrin conjugates as effective antiviral agents

Porphyrins have been used for photodynamic therapy (PDT) against a wide range of targets like bacteria, viruses and tumor cells. In this work, we report porphyrin-conjugated multi-walled carbon nanotubes (NT-P) as potent antiviral agents. Specifically, we used Protoporphyrin IX (PPIX), which we attached to acid-functionalized multi-walled carbon nanotubes (MWNTs). We decided to use carbon nanotubes as scaffolds because of their ease of recovery from a solution through filtration. In the presence of visible light, NT-P was found to significantly reduce the ability of Influenza A virus to infect mammalian cells. NT-P may be used effectively against influenza viruses with little or no chance of them developing resistance to the treatment. Furthermore, NT-P can be easily recovered through filtration which offers a facile strategy to reuse the active porphyrin moiety to its fullest extent. Thus NT-P conjugates represent a new approach for preparing ex?vivo reusable antiviral agents.     

Controlled clustering in metal nanorod arrays leads to strongly enhanced field emission characteristics

We show that controlled clustering in electrochemically grown silver nanorods results in up to 50% enhancement in their field emission performance. Larger cluster size and nanorod length lead to a lower turn-on electric field, a higher current density and a larger enhancement factor. However, beyond a critical length (≈30 μm), the nanorods begin to form disordered ridges instead of well separated conical clusters and the field emission performance proceeds to deteriorate. With the help of finite element modelling, we show that a larger cluster size indeed leads to an enhanced electric field at the cluster edges, effectively reducing screening effects and thereby enhancing the field emission performance. Though our present work pertains to silver nanorods, a similar clustering of nanorods is observed in many types of electrochemically grown nanorods, and even in carbon nanotubes and Si nanowires grown by other techniques. Hence, we expect this study to have general applicability in the design of better nanorod-based field emitters.     

UV-photolysis assisted digestion of food samples for the determination of selenium by electrothermal atomic absorption spectrometry (ETAAS)

An UV-oxidation procedure has been developed to completely digest biological/food samples for the determination of trace levels of selenium. A combined use of UV photolysis and hydrogen peroxide in the presence of an oxidant (HNO₃), results in the complete oxidation of the organic matter. This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures. The clear solution obtained was analysed for the selenium content by graphite furnace atomic absorption spectrometry. Unreduced palladium-nitrate modifier was used in all cases. However, in case of samples that are known to contain sulfur (like mushroom, Brazil nut, etc.), reduced palladium was used as modifier. The method was verified using three standard reference materials i.e., Whole egg powder-8415, Tuna fish-IAEA 350, Oyster tissue-1566a, and the results were in agreement at 95% confidence level. By using standards addition as calibration method, accurate results were obtained for the certified reference material, the precision for the CRM’s were in the range of 3.5–8%. The characteristic mass of selenium is assessed as 10 pg. The detection limits were in the range of 35–40 ng/g.     

Influence of whey protein concentrate on the rheological characteristics of dough, microstructure and quality of unleavened flat bread (parotta)

In order to explore the possibility of using WPC as a functional ingredient in Indian traditional product – South Indian Parotta investigations were made to study the effect of replacement of wheat flour with 5, 10 and 15% WPC on the farinograph, extensograph, amylograph characteristics of wheat flour, quality of parotta and microstructure of baked parotta. The results showed an increase in farinograph stability, extensograph resistance to extension up to 10% WPC and a decrease in the farinograph water absorption, extensograph extensibility, amylograph peak viscosity, cold paste viscosity, breakdown and setback values with an increase in the level of WPC from 0% to 15%. The quality characteristics of parotta showed that the spread ratio decreased and shear force values increased significantly above 5% level. Control parotta and parotta with 5% WPC were soft, possessed thin and transparent layers whereas parottas beyond 5% WPC had thick, fused and opaque layers. The parottas with 5% WPC were rated good. The quality characteristics of parotta were adversely affected beyond 5% level of WPC. The microstructure of the top and middle layer of baked parotta with 5% WPC showed that there was a disruption in the continuity of the gluten matrix.     

Computational fluid dynamics modeling of bread baking process

A computational fluid dynamic (CFD) model was developed to study the temperature and browning profile of bread. This study differs from previous work of CFD modeling reported in literature in that phase change during evaporation as well as evaporation-condensation mechanism during baking process was incorporated in this model. Simulation results were validated with experimental measurements of bread temperature at three different positions. In this study crumb temperature does not cross 100 °C due to incorporation of evaporation-condensation mechanism in this model. Baking process completes within 25 min of processing time once the temperature of crumb becomes stable at 98 °C. Formation of crust and browning of bread surface were studied using earlier reported kinetic model and it predicted more browning at bread edges than the surfaces. However, predicted browning index was well within the range (< 52).     

Listeria in tropical fish and fishery products

Listeria monocytogenes is considered to be a ubiquitous organism occurring in both terrestrial and aquatic habitats. This organism has been isolated from fish and fishery products from different parts of the world and interestingly the incidence rate reported from tropical fish is rather low. Varying methodologies have been used by different investigators to study the incidence of L. monocytogenes in fish. Data on virulence of seafood-associated strains are lacking. For quality assurance in the fish processing industry, rapid and sensitive methods for the detection of L. monocytogenes are required.