Search

Thermal energy and its storage systems play an extensive role in day-to-day life. They store renewable energy and are capable of recovering generated heat from different systems. Storage of thermal energy can be classified into three types: sensible, latent and sorption heat storages. Thermal heat storages use different types of materials based on their capacity of heat storage, stability of duration and thermal conductivity. Various phase change materials (PCMs) that are suitable for thermal storage are reported. Low conversion ability limits their effectiveness. We reviewed some of the traditional materials synthesized recently that are used for thermal energy storage (TES). Recently developed TES materials exhibit high thermal conductivity, reduced super cooling and multiple phase change temperatures. Nano-enhanced PCMs produced an increase in thermal conductivity up to 32% with a reduction in latent heat by 32%. At this juncture, MXenes with high performance and extraordinary properties (thermal, mechanical, etc.) are of special significance. MXenes displayed an increased thermal conductivity up to 16% and 94% efficiency. In view of their structure and adaptability to be used in thermal storage systems, an attempt was made to review their role also in thermal storage applications. It is observed that MXenes highly impact storage and efficiency. Apart from MXenes, various types of PCMs along with their thermal characteristics are presented. [ABSTRACT FROM AUTHOR]

Magnetic properties and structural analysis of Nd(Neodymium) doped Ni0.65Zn0.35Fe2O4 using XRD, Rietveld Analysis, FTIR Spectroscopy and VSM are reported. Confirmation of secondary phase formation with increased Nd content is established. Cation distribution for neodymium substituted nickel-zinc ferritesis proposed by considering the deficiency of Fe3+ in NiZnFe2O4 due to secondary phase formation of NdFeO3. The quality of present cation distribution was confirmed through close agreement of experimentally calculated lattice constant and Rietveld refinement. Changes in saturation magnetization with increased Nd content are explained on the basis of intensifying effect on energy exchange (inter-sublattice) between Ni-O-Nd and Ni-O-Fe concnerning Fe-O-Fe interaction, effect of replacing lower magnetic moment Nd3+ (3.62 μB) in place of Fe3+ (5 μB) and exchange developed between the cations existing at B-sites due to creation of oxygen vacancies. [ABSTRACT FROM AUTHOR]

In this study, we grew 5-layered SrBi4.25La0.75Ti4FeO18 (SBLFT) polycrystalline thin films (80–330 nm thick) via pulsed-laser deposition to study their ferroelectric and magnetoelectric response. Structural/microstructural analysis confirmed the formation of orthorhombic SBLFT with good crystallinity and randomly oriented Aurivillius phases. Detailed scanning transmission electron microscopy analysis of 120 nm film revealed a predominantly five-layered structure with the coexistence of four-layer stacking. Such stacking defects are found to be pertinent to the high structural flexibility of Bi-rich Aurivillius phases, alleviated by lattice strain. Raman spectral features at ambient temperatures depict the signature of the orthorhombic-tetragonal phase transition. SBLFT films have a strong ferroelectric nature (remanent polarization 2Pr of 35 μC cm−2) with a fatigue endurance up to 1010 cycles and strongly improved, switchable magnetization as opposed to its antiferromagnetic bulk counterpart. The scaling behavior of dynamic hysteresis reveals that ferroelectric domain reversal has good stability and low energy consumption. We observed the presence of SBLFT nanoregions (1–5 nm), distributed across the film, with Bi and Fe-rich compositions and oxygen vacancies that contribute to the weak ferromagnetic behavior mediated by the Dzyaloshinskii–Moriya interactions. Subtle changes in the structural strain and lattice distortions of thin films with varied thicknesses led to distinct ferroic properties. Stronger ferroelectric polarization of 80 nm and 120 nm films compared to that of thicker ones can be due to structural strain and the possible rearrangement of BO6 octahedra. The observation of the improved magnetoelectric coefficient of 50 mV cm−1 Oe−1 for 120 nm film, as compared to that of several Aurivillius oxides, indicates that the structural strain modification in SBLFT is beneficial for the fatigue-free magnetic field switching of ferroelectric polarization. The structural strain of the unit cell as well as the presence of Bi- and ferromagnetic Fe-rich nanoregions was found to be responsible for the improved multiferroic behaviour of the SBLFT films. [ABSTRACT FROM AUTHOR]

Supervisory Control and Data Acquisition (SCADA) systems have proved to be one of the important ingredients for substation automation. Legacy SCADA architectures are based on proprietary hardware and software-based Remote Terminal Units (RTUs) with little scope for modifications and expansions. Current SCADA architectures are based on distributed systems with Intelligent Electronic Devices (IEDs) based on IEC 61850. These SCADA systems are implemented with a centralized server located at control centers for performing various substation automation functions. With this kind of architecture, a local Human Machine Interface (HMI) is normally implemented to have access to the operational data at the substation level. Certain specific software applications catering to asset management functions, which are useful for the local operators, are also implemented at the substation level. All such local applications have to access data from IEDs, legacy RTUs, etc., called hardware nodes. Since these hardware nodes follow different communication interface methods, the software applications running in the desktop computers also have to adopt hardware-specific communication interface routines. Fast and reliable data transfer among these heterogeneous systems coupled with seamless integration to host applications is a technical challenge. The paper presents a generic Soft Data Bus (SDB), a communication interface framework between hardware nodes and software applications. SDB provides a common interface method on both sides which enables seamless access of data from RTUs which can easily be integrated with the local HMI and other asset management applications. It can be scaled up for a number of hardware nodes and data points without sacrificing much of performance. [ABSTRACT FROM AUTHOR]

Single-phase bismuth layered structure ferroelectromagnet (BLSFEM) LaGdxB5-xFe2Ti3O18of composition (x = 0.1, 0.2, 0.4, 0.6 and 0.8), novel ceramics were prepared by solid state route. Electrical and impedance measurements were made on the ceramics. Complex Impedance spectroscopic plots showed the signature of magnetic ion (Gd) and the results were corroborated to the Debye and Gaussian fitting curves. The variation of dielectric and modulus with temperature plots were used to explain dielectric phenomenon. An attempt is made to understand the effect of magnetic (Gd) ion on A site of (Bi2O2)2+(LaGdxBi3-xTi3Fe2O16)2−, layered perovskite (title) compound. [ABSTRACT FROM AUTHOR]

Bt. cotton, transgenic to protect from boll worms, needs integrated pest/disease management to avoid the losses due to sucking pests and foliar diseases. It is important to identify Bt. cotton hybrids resistant to major pests and diseases. One hundred and forty three Bt. cotton hybrids were evaluated against leaf hopper incidence and Alternaria leaf spot diseases under unprotected conditions during kharif, 2012. The experiment was laid in randomized block design, with two replications, by adopting 105×60 cm2 spacing. Leaf hopper counts were taken at regular intervals and grading was done at peak incidence. Alternaria leaf spot disease was recorded by adopting 0 to 4 scales and percent disease intensity was calculated. Hybrid wise yield was recorded. Two hybrids viz., Tulasi-144 (Prachanda Bhaskar) BG-II (3.75PDI) and U5-SS-33 BG-II (4.38PDI) recorded resistant reaction while 127 hybrids were moderately resistant to Alternaria leaf spot. Fifteen hybrids viz., SWCH-4746 BG-II, Sri Tulasi BG-II-4, NCS 9605, SP 7149, Big boss, ACH-111-2, PCH 468, NCS-456, NCS-245, KSPL (KDCHH-065), NCS-9015 (Malini), Jodha, Lotus, Bunny and Badhra recorded moderate susceptibility. Thirty hybrids exhibited grade II reaction to leaf hoppers including Jadoo KCH-14K-59, Neeraja MRC-7201, ATM-KCH-311 BG-II, Yuva BG II, Dr. Brent MRC-7347 BG-II with moderate resistance to Alternaria leaf spot and yields above 20 q ha-1. In conclusion farmers are advised to cultivate Bt. hybrids with multiple disease resistance to reduce the cost of plant protection and thus net returns can be enhanced. [ABSTRACT FROM AUTHOR]

The bismuth layer structured ferroelectric (BLSF) ceramics consisting of four-layers (BaLa0.75Bi3.25Ti4O15) and five-layers (Ba2La0.75Bi3.25Ti5O18) were prepared by the conventional solid-state reaction method. Summerfield ac-conductivity scaling analysis was used to evaluate the electrical behavior and the ac-conductivity isotherm curves. The relaxation results were corroborated with the Raman Peak positions and full width at half maximum was obtained by using Lorentzian peak fit method. Finally, the results were compared with the two-layered relaxor-compound (Bi2.45La0.55TiNbO9) and technologically standard three-layered compounds (La0.75Bi3.25Ti3O12; BLT). The dielectric relaxation of Bi2.45La0.55TiNbO9was verified using modified Curie-Weiss law and Vögel-Fulcher relationship. An attempt is made to realize the typical collective nature of the ionic conductivity of the samples. [ABSTRACT FROM AUTHOR]

A laboratory bioassay was conducted to study the impact of Cry 1 Ac protein on survival and development of Helicoverpa armigera (Hubner.) by feeding larvae with Bt cotton plant parts. During the study, terminal leaves and squares of two Bt hybrids, their corresponding non Bt hybrids and Bunny as check were fed to larvae. Among the plant parts tested, mortality of H.armigera larvae was higher on leaves compared to squares of both the Bt hybrids. Further, the mortality of early larval instars was higher compared to older instar larvae on both leaves and squares of Bt hybrids. Though, the later instar larvae were able to survive when exposed continuously to Bt cotton plant parts, but reduction larval and pupal weight, increase in larval developmental period, malformations in pupae and adults, reduction in adult emergence, less fecundity, low growth and survival indices was observed on both the Bt hybrids compared to their corresponding non Bt hybrids and check hybrid, Bunny. [ABSTRACT FROM AUTHOR]

Oxygen-deficient and charge- imbalanced polycrystalline materials of three-layered Auruvillius compound, namely Sr2Bi2Nb3O12(SBN), was synthesized by Sol-Gel method. X-ray diffraction analysis was made on SBN and lattice parameters were calculated. Electrical impedance and Pyroelectric measurements were performed on SBN. The broad peak observed in the dielectric permitivity data indicates that the transition is diffused phase transition (DPT) and the modified Curie-Weiss law was used to describe the DPT of SBN. The sharp intensity peak observed at 176 and 219 cm−1in Raman spectra is an indicative of Sr-O-Sr and Sr-O-Bi bonds and its competitive interactions. The peaks of FTIR spectra appeared at 610 cm−1confirmed the same. The nature of difffused type was attributed to compositional heterogenity and the results were corroborated with the log-log spectroscopic plots of impedance,modulus and permitivity for better understanding of the disorder ferroelectric behavior of the sample. The broad semicircle behavior observed in the complex impedance aswell as modulus plot, associated with grain and grain boundary, confirm the same. [ABSTRACT FROM AUTHOR]

Lanthanum and vanadium modified polycrystalline material of La0.75Bi3.25Ti2.9625V0.03O12(BLVT) of Aurivillius family, was prepared by conventional solid-state reaction method. X-ray diffraction showed single phase with orthorhombic structure. Electron microcopy was done on as-sintered and oxygen-annealed samples. Impedance studies of BLVT showed multiple impedance relaxations. Based on the impedance factor (related to full width at half maximum) and master plots, the relaxations are found to be collectively competitive. A broad dielectric peak and Curie-Weiss diffused parameter indicates diffused phase transition. Complex impedance analysis along with the log-log spectroscopic plots was studied on BLVT at 500°C. But complex impedance plot of BLVT showed single broad semicircle, unlike La0.75Bi3.25Ti3O12(BLT), which showed three semicircles on separately coated silver- and platinum- ceramic disks. However, complex modulus plot (complimentary to impedance) of BLVT showed three semicircles, which clearly indicates the tendency of formation of space charges, which might result in the accumulation of defects at electrode-ferroelectric interfaces, and considered to be a characteristic feature of the sample. In view of this, some of the BLVT samples were annealed in oxygen- and vacuum. Detailed ac-conductivity analysis suggests that double oxygen vacancies play vital role in conduction phenomenon. [ABSTRACT FROM AUTHOR]

Novel polycrystalline materials of bismuth substituted barium titanate, namely, BaBixTi1-xO3-δ, (x = 0.025, 0.075, 0.125 and 0.175) was prepared by sol-gel chemical route and characterized by X-ray diffraction and scanning electron microscopy. Bismuth ion was added in place of titanium of B-site of ABO3 perovskite structure and both the site-balance as well as charge-balance was considered. The substitution of bismuth for Ti-site is clearly seen in both the XRD as well as IR spectroscopic data. Dielectric and impedance analysis were also made on the present novel ceramics. The above mentioned substitution involves ionic compensation, through creation of cation vacancies and is explained by proposing the defect dynamics. The results were corroborated with dielectric and complex impedance analysis for further understanding of ionic motion in this kind of disordered diffused materials. [ABSTRACT FROM AUTHOR]

Tri-Valent (Sm3+/ Dy3+) and pentavalent (Nb5+) modified polycrystalline material of Aurivillius family, namely R0.75Bi3.25Ti2.9625.Nb0.03O12 (R = Sm, Dy), were prepared by conventional solid-state reaction method. Impedance and pyroelectric measurements were carried out to understand the electrical properties of the samples. Master plots were drawn to understand the defect role, especially vacancies, and the results were corroborated with the dc-conductivity data. Finally, both the complex impedance spectroscopic as well as pyroelectric results were compared with the impedance data of technological important materials, namely La0.75Bi3.25Ti3O12 (BLT) and lead zirconium titanate (PZT) for the further understanding of defects and its effects at the grain interfaces. [ABSTRACT FROM AUTHOR]

Impedance measurements were made on technological important ferroelectric ceramics, namely PZT and La0.75 Bi3.25Ti3O12 (BLT), in the frequency range of 100 Hz to 1 MHz, from room temperature to 500°C. Combined impedance and modulus spectroscopic analysis along with the detailed conductivity (ac and dc) data was used to understand the heterogeneity of the ceramics and the results were corroborated with temperature coefficient of dc-conductivity (figure of merit) data for the further understanding. AC-conductivity plots against frequency at different temperatures for PZT and BLT suggest the response of obeying Jonscher's and modified Jonscher's law, respectively. [ABSTRACT FROM AUTHOR]

Tri (Dy3 +) and pentavalent (Nb+5) modified new polycrystalline material of Aurivillius family (Dy0.75Bi3.25Ti2.9625Nb0.03O12) was prepared by solid-state reaction method and the lattice parameters were calculated by using X-ray diffractogram. Impedance measurements were carried out from room temperature to 500°C in the frequency range of 100 Hz to 1 M Hz. Impedance spectroscopic plots show non-Debye type and detailed ac-conductivity analysis was also employed to understand the heterogeneity of the present electro-ceramics. The results were corroborated with the proposed defect formula and in addition, thermal stimulated current measurements show that the present sample has an excellent pyroelectric response. [ABSTRACT FROM AUTHOR]

Impedance spectroscopic measurements were carried out on lead based ferroelectric ceramics, namely PZT, PLZT and PMN-PT, in the frequency range of 0.1 Hz-1 MHz. Spectroscopic plots showed broad peaks, and are found to shift towards higher frequency side. Apart from this, both Z'' and M'' spectroscopic peaks are found to coincide almost in the same frequency region. This indicates approximated-Debye behavior. Frequency dependent conductivity plots show two slopes at lower and higher frequency regions. Low frequency relaxations are found to be non-exponential. Bulk relaxation vs. temperature plots are found to obey Arhenius linear fit. The relaxation at lower frequency and higher are attributed to Kohlrausch-Williams-Watt (KWW) type and migration of slow oxygen and lead vacancies. The results are corroborated to the conduction barrier hopping mechanism and new Eyraud's conductivity model. [ABSTRACT FROM AUTHOR]

A and B site modified new bismuth layered structure ferroelectric ceramics of the Aurivillius family were prepared by the solid-state route. Impedance measurements were performed on these samples to understand the relaxation effects in the frequency range of 100 Hz to 1 MHz. From the detailed impedance and modulus spectroscopic analysis, it is found that the aliovalent modified B-site enhances the relaxor-like nature, compared to A-site substitution. These results were corroborated with ac-conductivity transport analysis. In this connection, a defect formula is also proposed. The results are discussed. [ABSTRACT FROM AUTHOR]

AC-impedance spectroscopic studies are carried out on lead magnesium niobate (PMN) and La-modified PMN-PT (lead magnesium niobate-lead titanate), Pb 1 - x La x [(Mg 1 + x / 3 Nb 2 - x / 3 ) 0.65 Ti 0.35( 1 - x / 4 ) ]O 3 , ceramic, with x = 0 to 0.07. Complex modulus and impedance plots exhibit two depressed semicircles and one depressed semicircle, respectively for PMN. This is attributed to the nearly same capacitance of grain and grain boundaries and higher grain boundary resistance than the grain resistance for PMN. Un-doped MPB composition of PMN-PT (0/65/35) and La-doped PMN-PT composition (7/65/35) also show similar complex modulus and impedance plots of PMN but in these samples the grain boundary capacitance was found to be higher than the grain capacitance. Cole-Cole plot shows two depressed semicircles, exhibiting grain and grain-boundary contributions in all the samples. La substitution is found to result in a broad peak in the frequency dependence of the imaginary part of the impedance and the modulus, for the temperature range 300–600°C. The maxima in the impedance and the modulus are found to shift towards higher frequencies with increasing temperature for all La-doped PMN-PT compositions, indicating a deviation from Debye behaviour. La-substitution results in broadening of the ε( T ) peak, and a marked frequency dependence of ε max (T max ), similar to that observed in PMN. It is believed that La-substitution induces the relaxor-like permittivity characteristics in MPB composition of PMN-PT by constructing higher-resistive and lower-capacitive grains, and grain boundaries. [ABSTRACT FROM AUTHOR]

The Ac conductivity measurements of polycrystalline materials of rare earth substituted Bi[sub 6]Fe[sub 2]Ti[sub 3]O[sub 18] compound at different frequencies (1 kHz-1 MHz) and temperatures (30550°C) are reported. The dc conductivity, ionic hoping rate as well as carrier densities have been extracted from the ac conductivity data. The results show that hoping mechanism dominates at lower temperature. The results are discussed. [ABSTRACT FROM AUTHOR]

GdBi[sub 5]Fe[sub 2]Ti[sub 3]O[sub 18] (GBFT), a compound of Aurivillius family, was prepared by solid state reaction method. Complex impedance measurement was made on these samples from room temperature to 500°C in the frequency range of 1 kHz-1 MHz. Cole-Cole plots were found to become very broad near 400°C. Dielectric and dc conductivity measurements were made on these samples. The results are analysed to understand the conductivity mechanism. [ABSTRACT FROM AUTHOR]

Back electromotive force (EMF)-based sensorless vector control of permanent magnet synchronous motor (PMSM) drives provides a simple, robust, and low-cost solution for applications requiring only medium- and high-speed control. However, during the low-speed operation, back EMF is nearly zero, and hence, for starting and speed ramp-up, open-loop I−ƒ control is used. Once the motor attains a sufficient speed, the control is transferred to sensorless vector control. However, an arbitrary choice of the slope of frequency ramp leads to pole slipping. Pole slipping is usually prevented by fixing the frequency ramp slope to a minimum value, which deteriorates the dynamic performance during starting. In this article, a torque controller is proposed to dynamically vary the frequency slope depending on the moment of inertia and load torque present in the system, achieving fast and reliable starting. A reference frequency modulation algorithm for overcoming the inherent mid-frequency instability of the open-loop control is also included. An additional slope attenuator is proposed to minimize the torque oscillations caused by the reference frequency modulation during the transition from a ramp-up interval to a constant-speed interval with I−ƒ control. The proposed methods are experimentally verified on a 25-kW PMSM drive, which is started using open-loop I−ƒ control. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to evaluate the efficacy of certain new molecules as well as entomopathogens as foliar sprays against leafhoppers in Bt cotton at Regional Agricultural Research Station, Lam, Guntur, Andhra Pradesh for two consecutive years. The new molecule, flonicamid 50% WG at two doses i.e. at 75 g a.i./ha and 100 g a.i./ha followed by diafenthiuron 50% WP 300 g a.i./ha and buprofezin 25% SC @ 250 g a.i./ha were found promising against leaf hoppers together with high seed cotton yield. New molecules were found significantly superior over to NSKE 5 % and entomopathogens in suppressing the leafhoppers. [ABSTRACT FROM AUTHOR]

Depleting water resources and increasing human demands on the available fresh water resources suggest the need and scope for integrated water resources assessment and management. Narava basin, a small watershed spread over 105 km² with a khondalitic suite of rocks and gneisses of Archaean age in the north coastal region of Andhra Pradesh, India was studied to propose effective water resources assessment and management strategies. The watershed, with an undulating topography and gentle to steep slopes, is drained by a dendritic to sub-dendritic drainage system. The watershed receives an annual average rainfall of 980 mm. With increasing agricultural activity, monsoon failures, and indiscriminate developmental activities, groundwater during the last two decades has become the main trusted source for irrigation and drinking. A hydrogeomorphological approach integrating remote sensing applications, geoelectrical investigations and hydrological studies was proposed to delineate and study the groundwater potential and recharge dynamics in the Narava watershed. Linking the remote sensing data, morphometric characteristics, topographic analysis, land use/cover assessment and groundwater conditions, hydrogeomorphic maps were prepared. Synergizing the lineament densities with layer parameters, aquifer yields, groundwater occurrence and dynamics, groundwater potential zones were demarcated and classified. Merging the characteristics of groundwater potential, hydrogeomorphology and water balance, suitable water harvesting structures and management strategies are suggested. [ABSTRACT FROM AUTHOR]

Nano particulate Barium Bismuth Titanate (BaBixTi1-xO3-δ) materials with (x = 0.25, 0.075. 0.125 and 0.175) were prepared through sol-gel chemical route (Pichini method) and the XRD patterns were indexed on the basis of tetragonal-BaTiO3 phase. The electrical impedance measurements were carried out on the samples by using Auto Lab PGSTAT30 impedance analyzer in the frequency region 100 Hz-1 MHz from RT to 500°C. Impedance spectroscopic and complex explicit plots show the presence of both bulk and grain boundary effects, and impedance spectroscopy is shown to be an efficient method capable of detecting the conductivity species and estimating the electrical conductivity as well as activation energy value. Finally, the results are interpreted in terms of the defect dynamics and conduction mechanisms taking place in the samples. [ABSTRACT FROM AUTHOR]

The presence and distribution of water in the pore space is a critical factor for flow and transport of gases through unsaturated porous media. The water content also affects the biological activity necessary for treatment of polluted gas streams in biofilters. In this research, microbial activity and quantity of inactive volume in a porous medium as a function of moisture content and gas flow rate were investigated. Yard waste compost was used as a test medium, and oxygen uptake rate measurements were used to quantify microbial activity and effective active compost volume using batch and column flow-through systems. Compost water contents were varied from air-dry to field capacity and gas flows ranged from 0.2 to 2 L · min-1. The results showed that overall microbial activity and the relative fraction of active compost medium volume increased with airflow velocity for all levels of water content up to a certain flow rate above which the oxygen uptake rate assumed a constant value independent of gas flow. The actual value of the maximum oxygen uptake rate was controlled by the water content. The oxygen uptake rate also increased with increasing water content and reached a maximum between 42 and 48% volumetric water content, above which it decreased, again likely because of formation of inactive zones in the compost medium. Overall, maximum possible oxygen uptake rate as a function of gas flow rate across all water contents and gas flows could be approximated by a linear expression. The relative fraction of active volume also increased with gas flow rate and reached approximately 80% for the highest gas flows used. [ABSTRACT FROM AUTHOR]

Samarium modified SrBi4-xSmxTi4O15 (x = 0, 0.13, 0.43 and 0.78) ferroelectric ceramics of Aurivillius family were prepared by conventional solid state reaction method. X-ray diffraction studies confirm the formation of a single-phase. Microstructural images show randomly oriented palate-like structure. Broad dielectric peaks were found to obey the modified Curie-Weiss law. The overall inherent ferroelectric nature was explained on the basis of the Avrami model. Furthermore, with increasing the Sm3+ content, the grain morphology and diffusive parameters have shown a comprehending impact on the ferroelectric (hysteresis) behavior. [ABSTRACT FROM AUTHOR]

SmxBi3–xTiNbO9 (SBTN) with x = 0 , 0.2, 0.4, 0.6, 0.8 and 1.0, a novel type of ceramic was prepared by a conventional solid-state reaction method. X-ray diffraction patterns confirm the formation of a single-phase, and lattice parameters were calculated based on the parent compound Bi3TiNbO9 (BTN). Well-defined grains were seen in the scanning electron microscopy pictures. A kink observed near 400°C for all the samples in the dielectric plot as well as in the stretched exponential parameter (β) vs. temperature plot reveals the dielectric relaxation of the samples. The tolerance factor (t) was found to increase with increase in the size of the A-site (Bi-site) modified ion (Sm). Impedance and modulus spectroscopic studies were conducted to understand the plausible reason for the dielectric relaxation. The relaxation was found to be well-fit with Arrhenius equation. SBTN samples showed lower dielectric loss compared to BTN. The remnant polarization, obtained from experimental, was found to be less than that of theoretically calculated polarization, using Shimakawa's formula. The proposed defect mechanism was interpreted using FTIR and Raman spectroscopic studies. [ABSTRACT FROM AUTHOR]

Bismuth layered structure ferroelectric materials of Aurivillius family have been attracted on account of their inherent-ferroelectric properties. Rare earth modified two layered compound, namely, Bi3TiNbO9has been found to be a relaxor ferroelectric material, and therefore much attention is being concentrated to enhance the dielectric properties with different modifications. In view of this, Sm-modified novel ceramic(Bi2SmTiNbO9) was prepared by the conventional solid-state reaction method. Impedance spectroscopic measurements were made as a function of frequency at different temperatures. Electrical studies were also made, and the results were corroborated to the Raman spectroscopic data. [ABSTRACT FROM AUTHOR]

Bismuth titanate (BT-‘Bi4Ti3O12’) is one of the extensively studied materials of the Bismuth layered structure ferroelectric (BLSF) family for its large spontaneous polarization along c-axis. In the present investigation, we have synthesised SmxBi4-xTi3O12(x = 0.37, 0.57, 0.72) ceramics using the conventional solid-state reaction method. The dielectric anomaly was observed near 450°C. Well-broad hysteresis loops were observed above room temperature up to 100°C. The coercive field (Ec) and consistent remanent polarization (Pr) values with temperature, compared to BT, indicates that the title compound has good promising ferroelectric-nature. This phenomenon is attributed to the easy recovery of defects (such as oxygen vacancies) accumulated at grain-interfaces, above room temperature, resulting in to well-hysteresis behaviour. The results were further confirmed with remanent polarization (2 Pr vs. temperature) plots. [ABSTRACT FROM AUTHOR]

Cyanobacteria or blue green algae have an extraordinary potential of producing secondary metabolites which can be an ultimate source of newer drugs for future. The purified strain Anabaena showed best photoautotrophic growth at 28°C with specific growth and generation time were 0.098 and 10.0 hr respectively. The better biomass production and antibacterial activity on 30th days of culture. 16 cyanobacterial strains collected from different sites of Delhi and NCR (National Capital Region, INDIA) identified as Microcystis, Anabaena, Oscillatoria, Nostoc, Phormidium sps were examined for antibacterial properties. The crude methanolic intracellular extracts of 8 strains showed activity against non-pathogenic Enterobacter aerogens and all 16 given potential against pathogenic Escherichia coli. In which purified Anabaena sps given maximum antibacterial activity against E. coli while Anabaena (Johad) and Microcystis (water tank) from Manesar (Gurgaon, India) against E. aerogens. The same strain from different origin has different antibacterial activity. This interpretation indicates the biosynthesis of bioactive molecules is niche and species specific. [ABSTRACT FROM AUTHOR]

Due to selenium (Se) deficiency, Se fortification of food and feed is applied in many countries. Therefore, potential use of Se-enriched kenaf was investigated based on its Se accumulation, its potential to transform accumulated Se to other Se species, and effect of Se accumulation on its growth. Kenaf was grown with different levels of two Se fertilizers (selenite and selenate) at concentrations ranging from 0 to 4 mg Se (kg soil)-1. Total Se concentrations in the plants grown on selenate-treated soil amounted to (1019 ± 136) mg Se (kg dry weight)-1 and were much higher compared to plants grown on selenite-treated soil. Identified Se species were selenite, selenate, Se-methionine, and Se-cystine. Biomass yield, net photosynthesis, and chlorophyll index of the plants decreased when plants were grown on soils treated with high doses of selenate. [ABSTRACT FROM AUTHOR]