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In this article a compact circular monopole antenna is represented with dimensions of 38.87 × 24.00 × 1.60 mm3 applicable for WLAN/Wi-MAX and satellite band rejection characteristics. The impedance bandwidth is 9.42 GHz (3.12–12.54 GHz) for the final antenna with an equivalent fractional bandwidth of about 120.31%, producing triple notched bands centered at 3.95, 5.20 and 8.90 GHz with assistance of Archimedean spiral slot and incorporation of defected ground structure allowing WLAN (5.2 GHz), WiMAX (3.5 GHz) and higher satellite X-band (8.5 GHz) filtering abilities. Simulations of the antenna are performed to attain preferable return loss properties as well as gain and omni-directional radiation patterns. The suggested antenna yields a peak gain of about 7.46 dBi at 11.30 GHz and experimental values are in good obedience with simulated ones.

Polymer-piezoceramic composites harness the flexibility of polymer and piezoelectric properties of ceramics to offer flexible piezoelectric materials for use in energy harvesting applications. Although, there is a general temptation to use piezoceramics which exhibits high piezoelectric coefficient (d33) in the fabrication of such composites, there are limitations posed by the processing conditions of the composite which eventually determines their overall performance. In the present work we have explored this aspect in detail. We fabricated composites with polyvinylidene fluoride (PVDF) as the polymer and three different piezoceramic powders namely BaTiO3 (BT), Ba(Ti0.97Sn0.03)O3 (BTS) and Sm-doped Pb (Mg1/3Nb2/3)O3-PbTiO3(Sm-PMN-PT). Our focus here is to understand the role of grain size of the ceramic powders in determining the dielectric, piezoelectric, and energy harvesting performance of the composites. To broaden the perspective, the results are compared with another analogous composite 0.59PbTiO3-0.41Bi(Zr0.5Ni0.5)O3 (PT-BNZ)-PVDF reported before. We found that, although, the dense ceramic specimen of Sm-PMN-PT exhibits exceptionally large d33, the composite with PT-BNZ exhibited the best piezoelectric and energy harvesting performance. BT, BTS and Sm-PMN-PT composites showed maximum surface power density of 6.24, 12.81 and 23.18 I¼W/cm2, respectively, and volume power density of 416.18, 854.1 and 1104 I¼W/cm3, respectively. Whereas surface power density and volume power density of PT-BNZ was 101.80 I¼W/cm2 and 5088.80 I¼W/cm3 respectively. We have also attempted to establish a correspondence between the piezoelectric response, energy harvesting performance and the poling induced domain reorientation/structural changes in the ceramic grains of the composites. © 2020 John Wiley & Sons Ltd

The present work was conducted to biofabricate silver nanoparticles (AgNPs) in single step employing aqueous extract of Dregea volubilis flowers and to investigate its antioxidant, antidiabetic and...

This article presents a compact circular-sectored microstrip antenna embedded with circular slots and a sectoral ground plane for enhanced bandwidth and applicable for UWB communications exhibiting...

This Letter illustrates prefrontal haemodynamics as a neurovascular basis of inter-personal working memory differences. A functional near-infrared spectroscopy with sampling frequency ∼2 Hz is used to record the blood oxyhaemoglobin and deoxyhaemoglobin signals from 19 subjects engaged in working memory task of encoding and retrieval of ten symbol-meaning association learning. The individual difference in working memory performance is classified by supervised learning-based linear discriminant analysis and ensemble classifiers. Prior to the classification approach, individual performance is labelled as high, moderate and low on the basis of the performance index. The spontaneous haemodynamic activity and task-evoked responses are marked as background and foreground signals, respectively, which are scaled by means of stream-independent and stream-dependent models. The classifiers' performance shows that the stream-dependent model-based feature construction-classification improves classification accuracy to a major extent compared to the stream-independent model and no gain model. To understand the neurovascular basis of the inter-individual performance difference, diffused voxel plots are constructed. The voxel plots showed that concurrent activation of orbitofrontal and dorsolateral prefrontal cortex could have a possible association with persons' higher working memory performance.

While studies in the past have shown that certain kinds of off-stoichiometry enhance the piezoelectric response of the lead-free piezoceramic Na0.5Bi0.5TiO3 (NBT), there is a lack of clarity regarding the mechanism associated with this interesting phenomenon from the fundamental structural perspective. In this paper, we have investigated this issue comprehensively and succeeded in establishing a mutual correspondence between off-stoichiometry, grain size, crystal structure, dielectric and piezoelectric properties in Na0.5Bi0.5TiO3 (NBT). Of the four different types of off-stoichiometric samples synthesized as per nominal formulae namely Na0.5+xBi0.5TiO3 (Na-excess Na-series), Na0.5-xBi0.5TiO3 (Na-deficient Na-series), Na0.5Bi0.5+xTiO3 (Bi-excess Bi-series), and Na0.5Bi0.5+xTiO3 (Bi-deficient Bi-series), the best piezoelectric response (d(33) similar to 100 pC/N) was obtained in the Na-deficient series with x = 0.04. We succeeded in establishing the structural link between off-stoichiometry and piezoelectricity of this series by examining the structural state of the specimens in their poled state. We show that the off-stoichiometric compositions exhibiting higher piezoelectric response contain a higher fraction of the disordered ferroelectric phase coexisting with the field stabilized long-range ferroelectric (R3c) order. Beyond the critical off-stoichiometry (x > 0.04), the dominance of the structural disorder collapses the piezoelectric response of the system. We also show that what can be achieved by off-stoichiometry can as well be achieved by reducing the grain size of stoichiometric NBT. Our results suggest that the enhanced piezoelectric response of the off-stoichiometric compositions is due to their reduced grain size as compared to the stoichiometric composition, and that the nature of the defect species has a secondary role, if any. We found the same phenomenon/mechanism to be operative in the off-stoichiometric morphotropic phase boundary composition 0.94Na(0.5)Bi(0.5)TiO(3)-0.06BaTiO(3) (NBT-6BT). While our experiments confirm the role of the surviving structural heterogeneity (after poling) as an important contributing factor which enhances the piezoelectric response of NBT-based lead-free piezoceramics, we also use dielectric dispersion as a tool to show that the off-stoichiometric composition exhibiting highest piezoelectric response is characterized by maximum suppression of the disordered phase by the poling field. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

This paper presents a compact circular sectored microstrip antenna embedded with two symmetric circular slots and a sectoral ground plane embedded with an open-ended rectangular slot for enhancement of bandwidth and its applicability for UWB communications. The proposed structure exhibits Fractional Bandwidth(FBW) of 157.38 % (2.38 GHz –19.96 GHz) using Rogers RT Duroid 5880as a substrate for lower surface wave loss and attaining broader bandwidth producing notch band centered at around 5.30 GHz (4.26 GHz – 6.34 GHz) which effectively filters out WLAN(5.2/5.8 GHz) and WiMAX(5.5 GHz) bands. The gain of the antenna ranges from 5.34 – 5.73dBi throughout the resonant frequency band and the results obtained from measurement have good accordance with simulated solutions in terms of return loss, gain, polarization and far field patterns.

Purified gum odina (PGO) from Odina wodier Roxb. was characterized by rheology, AFM, Raman and CD spectroscopy, in vitro antioxidant activity against hydroxyl radical and superoxide radical, and total antioxidant capacity. The PGO dispersions exhibited pseudoplastic behaviour. The viscosity of dispersion increased with increasing PGO concentration, but decreased with increasing temperature and added salt concentration. The loss modulus was higher than storage modulus indicating prevalently viscous characteristics. AFM analysis showed irregular spherical lumps due to inter- and intramolecular interactions. The Raman spectrum of PGO was similar to that of gum arabic. Circular dichroism revealed partial adoption of polyproline II type conformation, suggesting a less compact structure. The PGO was found to scavenge hydroxyl radical (IC50 517.68 ± 3.60 μg/mL) and superoxide radical (IC50 586.21 ± 3.41 μg/mL), and possess total antioxidant capacity (9.64 ± 0.23 mg gallic acid equivalent/g). Overall, this work would exploit PGO as a new hydrocolloid source in the food and pharmaceutical industries.

In the current study, a multiple emulsion (W/O/W) of lamivudine was developed using a new biopolymer, gum odina (GOd) to increase bioavailability and patient compliances. GOd was employed to stabilize both the interfaces of liquid membrane in both the external and internal aqueous phases. The developed W/O/W multiple emulsion of lamivudine was characterized by analyzing droplet size, zeta potential, polydispersity index (PDI), sedimentation, viscosity, rheological properties, drug entrapment efficiency, in-vitro drug release and stability at various storage conditions. The results obtained were also compared with W/O/W multiple emulsion of lamivudine prepared using Tween 80 (a standard emulsion stabilizer). The drug entrapment efficiency of W/O/W multiple emulsion stabilized using GOd was measured as 91.60 ± 3.66% with sustained lamivudine release over a period of 6 h. Rheological and microscopic examinations indicated long term stability of the developed emulsion prepared using GOd. The results of the current study provide a promising scope to attain sustained drug release through the W/O/W multiple emulsions stabilized by GOd in antiviral therapies. Keywords: Gum odina, Lamivudine, Multiple emulsions

We have synthesized lead-free BZT-xBCT (x = 0.45, 0.50 and 0.55) compositions near morphotropic phase boundary (MPB) using sol-gel technique. Here, we have reported the compositional effect of BCT concentration on structure, surface morphology, dielectric properties and energy storage capacity of BZT-xBCT ceramics. Scanning electron microscopy analysis suggests that the smallest grain size is found for the x = 0.55 composition. The dielectric constant vs temperature measurement indicates that the addition of BCT causes lowering of ordering temperature. In addition, we have performed modified Curie-Weiss fitting to reveal the microscopic behaviour of the synthesized compositions and found Curie constant ‘C’ as 1.3 × 10 6 , 2.1 × 10 7 and 1.7 × 10 7 for x = 0.45, 0.50 and 0.55 compositions, respectively, and diffusion coefficient 1.4 ≤ γ ≤ 1.99 . Polarization (P) vs electric field (E) curves collected at series of temperature, insights that compositions x = 0.50 and 0.55 exhibit slimmer P-E profiles, which causes lowering of remnant polarization (Pr) and hysteresis loss of dielectric system and ensures their suitability in area of pyroelectric based energy harvesting. We also estimated the energy storage density W~189 mJ/cm3 and high discharge efficiency η~75.6% for BZT-0.55BCT ceramic composition. Further, we have employed Arrott plot approach to reveal the involved mechanism of Landau Free Energy flattening in BZT-BCT composition at MPB. It is considered that Landau Free Energy flattening plays key role in exhibiting high electro-mechanical response at MPB. On the basis of findings from dielectric spectroscopy and Arrott plot scheme, we argue that energy flattening phenomenon and high electromechanical response in BZT-xBCT system is achieved via active “polarization rotation mechanism”, instead of “polarization extension”. Our study emphasizes that BCT rich BZT-0.55BCT ceramics are suitable for high energy storage density application.

Morphotropic phase boundary (MPB) and polymorphic phase boundary ferroelectric solid solutions show enhanced electromechanical response and are sought after as actuator and transducer materials. Compared to others, the lead-free piezoelectric solid solution ${\mathrm{N}}_{0.5}\mathrm{B}{\mathrm{i}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}\ensuremath{-}\mathrm{BaTi}{\mathrm{O}}_{3}$ stands out in two important respects: (i) low piezoelectric coefficients $(\ensuremath{\sim}200\phantom{\rule{0.16em}{0ex}}\mathrm{pC}/\mathrm{N})$ and (ii) anomalous decrease in the depolarization temperature at the MPB, the reason for which is still unclear. Here we show that both features are related; this is caused by an increasing intervention of a nonferroelectric structural distortion which compromises the gains the system acquires at the MPB via the interferroelectric instability. The propensity of the intervening nonferroelectric distortion, identified as in-phase octahedral tilt, grows considerably as the MPB is approached causing considerable structural-polar disorder, weakening the overall strength of ferroelectric interaction.

A Super Wideband (SWB), compact sized, coplanar waveguide fed monopole antenna having dual-band notch feature has been investigated in this paper. The antenna exhibits an extremely wide impedance-bandwidth of 33.12 GHz (01.19 GHz – 34.31 GHz) and an equivalent fractional bandwidth of 186.59 %. The antenna proposed here, shows dual band-notch features at WiMAX (03.3 GHz - 03.7 GHz) and WLAN (05.15 GHz – 05.85 GHz) bands. The band rejection characteristics, for the WLAN band centered at 05.5 GHz has been obtained by introducing a Split Ring Rectangular Resonating Structure (SRRRS) at the lower section of the elliptical radiator. A Defected Spiral Microstrip Structure (DSMS) has been introduced in the feed line segment for obtaining a second band-notch for the WiMAX band centered at 03.5 GHz. The dimension of the whole structure is $W\ x\ L = 20 \times 22\ \mathrm{mm}^{2} = 0.079 \lambda_{\mathrm{o}} \times 0.087 \lambda_{\mathrm{o}}\ \mathrm{mm}^{2}$ . The proposed antenna is applicable for Wireless Personal Area Network (WPAN) based communications.

An isothermal kinetic study of a novel technique for reducing agglomerated iron ore by volatiles released by pyrolysis of lean-grade non-coking coal was carried out at temperature from 1050 to 1200°C for 10–120 min. The reduced samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and chemical analysis. A good degree of metallization and reduction was achieved. Gas diffusion through the solid was identified as the reaction-rate-controlling resistance; however, during the initial period, particularly at lower temperatures, resistance to interfacial chemical reaction was also significant, though not dominant. The apparent rate constant was observed to increase marginally with decreasing size of the particles constituting the nuggets. The apparent activation energy of reduction was estimated to be in the range from 49.640 to 51.220 kJ/mol and was not observed to be affected by the particle size. The sulfur and carbon contents in the reduced samples were also determined.

This study investigates the design of sunflower oil entrapped floating and mucoadhesive beads of amoxicillin trihydrate using sodium alginate and hydroxypropyl methylcellulose as matrix polymers and chitosan as coating polymer to localize the antibiotic at the stomach site against Helicobacter pylori. Beads prepared by ionotropic gellation technique were evaluated for different physicochemical, in-vitro and in-vivo properties. Beads of all batches were floated for >24 h with a maximum lag time of 46.3 ± 3.2 s. Scanning electron microscopy revealed that the beads were spherical in shape with few oil filled channels distributed throughout the surfaces and small pocket structures inside the matrix confirming oil entrapment. Prepared beads showed good mucoadhesiveness of 75.7 ± 3.0% to 85.0 ± 5.5%. The drug release profile was best fitted to Higuchi model with non fickian driven mechanism. The optimized batch showed 100% Helicobacter pylori growth inhibition in 15 h in in-vitro culture. Furthermore, X-ray study in rabbit stomach confirmed the gastric retention of optimized formulation. The results exhibited that formulated beads may be preferred to localize the antibiotic in the gastric region to allow more availability of antibiotic at gastric mucus layer acting on Helicobacter pylori , thereby improving the therapeutic efficacy.

A detailed investigation is made to study the effect of the presence of gangue materials like SiO2, Al2O3 and P2O5 on the reducibility of iron ores in the blast furnace and sponge iron/DRI plants. The shatter index and abrasion index are found to improve marginally with increased content of the gangue materials, though the improvement is not significant. The rate of reduction decreases with time, and interfacial chemical reaction is identified as the rate-controlling resistance. The apparent activation energy is determined from the slope of the plot $${1-(1-f)^{0.5 }}$$ versus time, where f denotes the extent of reduction. At a high temperature (1373 K), a little deviation from linearity is observed, indicating greater contribution of diffusion. The apparent activation energy is found to vary between 125.82 and 149.49 kJ/mol for different composition of the nuggets. The presence of SiO2 and Al2O3 is found to reduce the apparent activation energy, E, while the presence of P2O5 increases the value of E. The average decrease in the apparent activation energy is found to be 1.63 and 1.33 kJ/mol per unit mass% increase in SiO2 and Al2O3, respectively, and the average increase in the apparent activation energy is 2.69 kJ/mol per unit mass% increase in P2O5.

Apart from being a model ferroelectric, BaTiO3 and its derivatives are materials of considerable technological importance in the capacitor industry and as a potential Pb-free piezoelectric. Here, we have examined BaTiO3 for its propensity to stabilize local low symmetry distortions and induce structural heterogeneity for two different situations, namely, (1) by introducing inhomogeneous lattice strain and (2) by restricting the average grain size to the submicrometer regime. We have introduced Eu+3 ions in BaTiO3 in a very dilute concentration to act as local probes. Our strategy relies on exploiting the great sensitivity of the 5D0 → 7F2 transition of Eu+3 with regard to the variation in the asymmetric distribution of the ligand field around itself to probe the structural heterogeneity developed in BaTiO3. The Eu+3 photoluminescence signal revealed a remarkable increase in the local structural heterogeneity in submicrometer (∼0.4 μm) sized BaTiO3. This manifests as an ∼170% increase in the intensity of the 7F2 band with respect to the structure insensitive 7F1 band. Although to a lesser extent, a similar scenario was observed when the large grain BaTiO3 develops residual strain. The structural insights presented here can be helpful in explaining the properties of BaTiO3-based multilayered ceramics wherein the two conditions of submicrometer size and residual strain is a common occurrence.

We report here the synthesis of a self-grown 0–3 particulate multiferroic composite by controlled precipitation of the ferrimagnetic garnet phase using additive (MnO2) assisted sintering of a multi-cation ferroelectric system (Bi, Pb, Dy)(Fe, Ti)O3. The particulate multiferroic composite derived in this manner exhibits a favorable microstructure, wherein, although the volume fraction of the garnet phase is kept low (6%), which helps in retaining the electrical insulating character of the specimen, the number fraction of the garnet grains vis-a-vis the ferroelectric grains is ∼1:1. The composite shows a nearly ∼50% increase in saturation polarization at room temperature under a modest magnetic field of 1 T, suggesting a considerable improvement in ferroelectric domain switching due to the efficient strain transfer from the minority garnet grains to the majority piezoelectric grains.

The toxicity of nanomaterials can sometimes be attributed to photogenerated reactive oxygen species (ROS), but these ROS can also be scavenged by nanomaterials, yielding opportunities for crossover between the properties. The morphology of nanomaterials also influences such features due to defect-induced properties. Here we report morphology-induced crossover between pro-oxidant activity (ROS generation) and antioxidant activity (ROS scavenging) of MgO. To study this process in detail, we prepared three different nanostructures of MgO (nanoparticles, nanoplates, and nanorods) and characterized them by HRTEM. These three nanostructures effectively generate superoxide anions (O2•–) and hydroxyl radicals (•OH) at higher concentrations (>500 μg/mL) but scavenge O2•– at lower concentrations (40 μg/mL) with successful crossover at 200 μg/mL. Nanorods of MgO generate the highest levels of O2•–, whereas nanoparticles scavenge O2•– to the highest extent (60%). Photoluminescence studies reveal that such crossover i...

Local structural heterogeneity is known to enhance the piezoelectric response of perovskite-based ferroelectrics. Here we investigate how this heterogeneity is affected by strong electric fields using dilute doped ${\mathrm{Eu}}^{+3}$ ions as local structural probes. We make use of the extreme sensitivity of the $^{5}D_{0}\ensuremath{\rightarrow}^{7}F_{2}$ hypersensitive transition of ${\mathrm{Eu}}^{+3}$ vis-\`a-vis the asymmetric distribution of the ligand field around the doped ion to demonstrate that a strong electric field (poling) increases the overall low-symmetry regions on the local length scale in a ${\mathrm{BaTiO}}_{3}$-based lead-free piezoceramic near the $P4mm\text{\ensuremath{-}}Amm2$ polymorphic phase boundary (PPB). Our study suggests that the mandatory treatment of poling given to a ceramic to make it piezoactive also contributes to the microscopic mechanisms that improve the system's piezo-response.

In this paper, a wideband printed polygon-shaped monopole antenna has been designed using microstrip line feeding technique which provides dual-notch band characteristics (2.98–3.19[Formula: see text]GHz) and (3.62–5.00[Formula: see text]GHz) by the use of slots geometry in both the patch and the ground plane. The results of the antenna have been compared both with and without slots in both planes. The initial antenna without DGS and slots in the patch was made to work in the frequency range from 2.56–5.98[Formula: see text]GHz having impedance bandwidth of about 80.09%. The proposed antenna can be made usable for multi-band applications such as WLAN (2.4/3.2/5.2/5.8[Formula: see text]GHz) and Wi-MAX (3.5 and 5.5[Formula: see text]GHz) applications providing fractional bandwidth (FBW) of 85.36% (2.33–5.80[Formula: see text]GHz) and maximum peak gain of 5.65[Formula: see text]dBi at 3.50[Formula: see text]GHz. The value of return loss obtained is about 53.36[Formula: see text]dB at 2.56[Formula: see text]GHz. Prototype of the final antenna is fabricated and the results are verified with the simulated ones.

With increasing industrial acceptance of Na0.5Bi0.5TiO3 (NBT)-based lead-free piezoceramics, there is a need to develop insights into the way different factors influence the microstructural–structural–piezoelectric property correlations. In this work, we have examined the role of structural disorder on the piezoelectric response of the pre-MPB composition x = 0.03 of the well-known solid solution series (1-x)Na0.5Bi0.5TiO3-(x)BaTiO3. Using off-stoichiometry on the A-site as a tuning parameter to vary the structural disorder, which we characterize in terms of the fraction of the “cubiclike phase” or variation in the thermal parameter of the A-site cation, it is shown that the piezo response maximizes for the composition, which retains an optimum degree of disorder after poling. Our study confirms the important role of structural disorder in enhancing piezoelectric response in ferroelectric ceramics.