Search

The anomalous behaviour of Eu3+ emission quenching on cooling is explained using experimental/theoretical approaches involving off-resonance excitation. Based on this, a highly sensitive CaTiO3:Eu3+,Er3+ phosphor (Sr = 4.9% K−1 at 83 K) was designed.

Dual polarization is achieved by putting a rectangular or circular patch in between two orthogonal gaps. At the beginning a single-polarized patch is considered. Then by using anequivalent circuit, the impedance matching property of the gap is being configured. After optimization of the length of the patch and width of the gap, a dual polarized antenna is being considered. Here in this article we projected a new technique to design dual polarized microstrip antenna for WLAN, WiMAX, wireless applications using circular patch. By combining all resonant modes we have finally achieved a wide operating bandwidth. Experimental result of the projected antenna shows the operating bandwidth of 21.56% (5.24–6.37 GHz) for (differential mode S-parameter) S dd11 ≤ −10 dB with a high port isolation of 40 dB and a relative gain of 13.5 dBi is achieved. From the result analysis this antenna finds its applications for various WLAN and Wi-MAX frequency band.

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.

In India, foggy weather creates poor visibility, and this leads to several accidents and slows down normal traffic speed, which may lead to adverse effect on the economy of the country. The probable solution is the use of monochromatic light with other artificial vision system to increase the visibility for the drivers in these foggy areas. There are various kinds of monochromatic lights available in the market. In this study, it has been tried to find out the best working monochromatic LEDs for this particular application. In this study, two types of monochromatic radiation were compared (amber light with 600 nm and green light with 545 nm) with and without the camera-display setup (artificial visual system) for finding out best working system in the foggy area for increasing the visibility. The experiment shows that amber light monochromatic radiation with 600 nm works better for identification of objects. The amber light can be used in front of a car to illuminate the front environment in the foggy weather and increase the visibility. It has been observed that green light monochromatic radiation with 545 nm works better for identification of the source from a very long distance. It has been proposed to install both of these lights with amber and green monochromatic radiation in vehicles to reduce accidents in foggy weather.

A-site off-stoichiometry has been an efficient method to enhance the electromechanical properties of lead-free Na0.5Bi0.5TiO3(NBT)-based piezoceramics. In this work, we have reported the effect of Na/Bi off-stoichiometry on the microstructural, structural, and electromechanical properties of the tetragonal 0.80Na0.5Bi0.5TiO3–0.20BaTiO3 (NBT–20BT) ceramic. The maximum piezoresponse ~ 115 pC/N is obtained for 4 mol% Na-deficient (20BT–Na46) and 2 mol% Bi-excess (20BT–Bi52) compositions. It is a 25% increment over the piezoresponse of the stoichiometric composition (20BT–Na50 ~ 90 pC/N). The enhancement in piezoresponse has been attributed to an optimized presence of polar-structural heterogeneity/disorder in the poled ceramic matrix and an optimized distortion of the long-range tetragonal ferroelectric phase. It is established that A-site off-stoichiometry is influencing the polar-structural heterogeneity/disorder and tetragonal lattice distortion via the grain size.

In the recent days, rare-earth doped phosphors have attracted an immense attraction in luminescence field for various solid-state lighting and electronic display device applications. However, need of efficient red phosphor is a prevalent challenge in this field. Herein, we report a bright red light emitting Na+ co-doped SrAl2O4:Eu3+ phosphor which is synthesized by modified sol–gel technique. These nanophosphors show excellent red emission due to characteristic 5D0 → 7Fj (j = 1, 2, 3, 4) transitions of the doped Eu3+ ions excited by 394 nm. Photoluminescence studies of both Eu3+ doped SrAl2O4 and Na+ co-doped SrAl2O4:Eu3+ has shown more than fourfold increase in the intensity for optimum Na+ addition. The improved decay time obtained from decay measurement has revealed that the co-doped Na+ has successfully reduced the nonradiative transitions. Thus, addition of monovalent Na+ to Eu3+ doped SrAl2O4 was found to be effective to address the charge imbalance problem along with significant enhancement in luminescence intensity and decay time. The results suggest that this nanophosphor could be a major candidate in the rapidly increasing field of solid-state lighting applications.

A 10-years-old boy presented with a history of effort intolerance and palpitations for 4 months. His electrocardiogram showed wide complex tachycardia suggestive of fascicular ventricular tachycardia (VT). The echocardiogram showed moderate-to-severe left ventricular systolic dysfunction without any structural lesion. The tachycardia was unresponsive to adenosine and direct current cardioversion. It responded to oral verapamil. The electrophysiology study confirmed the tachycardia as left posterior fascicular VT. The tachycardia was successfully ablated guided by Purkinje potential on three-dimensional mappings. He showed improvement in ventricular functions before discharge. He is doing well on short-term follow-up.

Pulmonary artery to the left atrial fistula is a rare anomaly. Two young males presented with effort intolerance and cyanosis and had large pulmonary artery to left atrial fistula from right and left pulmonary artery, respectively. The right-sided fistula was closed with a large duct occluder device in transseptal approach whereas the left-sided fistula was closed with a large muscular ventricular septal device. Complete occlusion and symptomatic relief was achieved in both cases. In the follow up the patients were doing well.

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...

Secondary metabolites of plants are important resources for development of new drugs. Mangrove plants are very well known sources of wide variety of secondary metabolites. Many of these secondary metabolites from mangroves have been found to possess significant biological activities where human health is concerned. Avicennia alba Blume is one such mangrove plant with reports of having many such secondary metabolites of clinical and commercial interests. Aim: To evaluate antimicrobial activity potential of A. alba wood extract and to isolate new bioactive constituent(s) responsible for such biological activity. Methodology: Preliminary screenings of antimicrobial activities in different organic solvent extracts of A. alba wood tissue were done by TLC-bioautography method and phytochemical nature of the antimicrobial constituent(s) in the extracts have been studied. One compound exhibiting significant antimicrobial activity, named as Albain 1, has been isolated. MIC value has been determined for Albain 1. The purity and structure of Albain 1 have been determined by HPLC, 1H NMR, FTIR and HRMS etc. analysis. Results: 1H NMR, FTIR and HRMS analysis have found out that the isolated compound Albain 1 is a triterpene and the molecular formula is C30H48O4. It has exhibited remarkable antimicrobial activity against Bacillus cereus, Bacillus polymyxa, Bacillus pumilas (MIC 125 μg / ml). Conclusion: The observed antimicrobial activity of the isolated fraction of A. alba offer great potentials in pharmaceutical industries.

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...

The ability to tune the emission color of materials by external stimuli like electric field, pressure, temperature, etc., offers avenues to design light-based sensors and devices. We report here a new strategy which enables large temperature tuning of the emission color of a lanthanide phosphor by combining Raman and photoluminescence (PL) signals. The phenomenon and the associated mechanism, demonstrated on Eu, Er doped BaTiO3, shows the emission color to change from orange to green when cooled down to 10 K. The large color tuning is a consequence of synergy of the two processes: (i) significant enhancement of the Raman signal due to gradual structural ordering in the rhombohedral ferroelectric phase of the host BaTiO3 and (ii) anomalous low temperature quenching of the PL emission of the doped Eu3+ by trap states. We show that this contrasting temperature effect on the PL and the Raman signals can be used as a powerful strategy to design phosphor materials for high performance optical thermometry.

Objective Transcatheter atrial septal defect (ASD) device closure in the older population presents a greater challenge due to the long-standing effect of atrial left-to-right shunt. This study analyzes the challenges encountered in transcatheter ASD device closure in older patients in their fifth decade and beyond. Methods Adults aged 40 years and above with significant secundum ASD who underwent transcatheter ASD device closure between June 2015 and April 2021 were analyzed. Challenges were classified as major and minor challenges based on their impact on the alteration of the treatment protocol. Patients were categorized into three subgroups according to age. Group 1 consisted of patients aged 40-49 years (n = 13), Group 2 consisted of patients aged 50-59 years (n = 16), and Group 3 consisted of patients aged 60 years and above (n = 8). Results A total of 37 patients were analyzed. The challenges encountered were arrhythmia, pulmonary hypertension, left ventricular diastolic dysfunction, bleeding, stroke, coronary artery disease (CAD), hypertension, and airway disease. Thirteen percent of challenges were seen in pre-procedure time, whereas 79% of challenges during the procedure and 8% of challenges during post-procedure were seen. Thirty-five patients (94.6%) underwent transcatheter ASD device closure. Two patients (5.4%) did not undergo transcatheter ASD device closure due to severe diastolic dysfunction and associated CAD, respectively. Eleven major challenges were encountered in 10 patients in which one patient had a dual challenge of bleeding and arrhythmia. Thirteen patients (35.1%) had smooth procedures without any challenges encountered. Twenty-seven minor challenges were encountered in 20 patients with some patients having an overlap of multiple major and minor challenges. The patients were doing well at the mean follow-up of 28 months. Conclusions Transcatheter ASD device closure in older patients who are 40 years and above is safe and effective. Such high-risk patients are prone to various challenges that can be effectively managed if optimally monitored on the basis of a proper understanding of the altered physiology and anticipation of the deviated course at various stages of the procedure.

The prevalent material design principles for optical thermometry primarily rely on thermally driven changes in the relative intensities of the thermally coupled levels (TCLs) of rare-earth-doped phosphor materials, where the maximum achievable sensitivity is limited by the energy gap between the TCLs. In this work, a new, to the best of our knowledge, approach to thermometric material design is proposed, which is based on temperature tuning of PL emission from the visible to the NIR region. We demonstrate a model ferroelectric phosphor, Eu

This paper presents a compact asymmetric CPW fed monopole antenna using Denim fabric as substrate applicable for UWB communication and various wireless body area networks (WBANs). The geometry of the antenna consists of a circular monopole antenna with a modified ground plane and introduction of defected ground structures (DGS) to achieve ultra-wide band (3.10–10.6 GHz) characteristics. The proposed wearable antenna operates from 2.40 to 14.88 GHz providing a fractional bandwidth (FBW) of about 144.44%. Enhancement of the bandwidth is obtained by the insertion of open ended rectangular slit in the ground plane. The final antenna produces a peak gain of about 6.57 dBi at 13.05 GHz and achieved omnidirectional radiation patterns. In terms of return loss, gain, and radiation characteristics, the lightweight flexible wearable antenna is fabricated, and the tested effects are found to be in fair accordance with the simulated ones.

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.

The search for multifunctional organic compounds that display technologically important properties has been pursued in recent years. Here we report the synthesis and structure of a series of single...

Objective: The various parts of Dregea volubilis (Family: Apocynaceae), locally known as Jukti (Bengali), are commonly used in Indian system of medicine to treat various ailments such as inflammation, piles, leukoderma, asthma, and tumors. Literature review suggested that there has been no detailed work on systemic pharmacognostic and phytochemical studies done on the flowers of the plant. The present study is aimed to lay down quality control parameters for D. volubilis flowers to confirm its identity, quality, and purity. Methods: The present work was designed to study detailed organoleptic, histological, quantitative standards, physicochemical, spectroscopic, and chromatographic characteristics of the flowers of D. volubilis. Results: The total ash, acid insoluble ash, water soluble ash, loss on drying, water, and alcohol soluble extractive values were found to be 11.767±0.130% (w/w), 1.287±0.106% (w/w), 9.140±0.344% (w/w), 14.110±0.061% (w/w), 21.600±0.133% (w/v), and 9.603±0.104% (w/v), respectively. Phytochemical screening of different extracts showed the presence of carbohydrates, proteins, amino acids, steroids, glycosides, alkaloids, flavonoids, tannins, and phenolics. The chromatographic study revealed the presence of rhamnose (103.229±4.994 μg/g), fructose (738.670±25.714 μg/g), glucose (285.532±24.465 μg/g), and maltose (49.082±5.206 μg/g). Conclusion: The characterization parameters of the present study may serve as a reference standard for proper authentication, identification and for distinguishing the plant from its adulterants.

Objective: A series of 5-substituted-4-amino-1, 2, 4-triazole-linked hydroxamic acid derivatives have been synthesized and explored in vitro to evaluate antibacterial and antifungal activities. Methods: Different 5-phenyl group substituted-4-amino-1,2,4-triazole-3-thiol reacted with chlorine substituted hydroxamic acid to produce the desired compounds and characterized spectroscopically. Minimum inhibitory concentration (MIC), zone of inhibition (ZOI), growth kinetic studies, and scanning electron microscopy (SEM) were employed to elicit the antimicrobial efficacy of synthesized compounds against a wide range of bacterial and fungal strains. Results: Compounds 6a, 6b, 6d, and 6k (MIC of 25 μg/ml) have been found to be more potent against Klebsiella pneumoniae, Bacillus cereus, Bacillus pumilus, Micrococcus luteus, and Pseudomonas aeruginosa, compounds 6a-6d, 6k, and 6l (MIC of 25–50 μg/ml) have shown potent antibacterial efficacy against Klebsiella pneumonia, P. aeruginosa, and Vibrio cholera compare to the standard drug amoxicillin (MIC of 60 μg/ml, 65 μg/ml, and 25 μg/ml, respectively). Screening for the antifungal activity revealed that the compounds were found to be most active against Candida albicans (6a, 6b, and 6l), Candida tropicalis (6b and 6d), and Aspergillus niger (6a, 6b, 6d, and 6j) with MIC of 15–25 μg/ml. Bacteriostatic and fungistatic effect of titled compounds was revealed from growth kinetics study. Conclusion: Electron donating group at the 5-position of the 5-substituted-1,2,4-triazole-linked hydroxamic acid derivatives conferred the biological effectiveness of the synthesized compounds and also offer a therapeutically effective prototypical structure for further development of new chemical entities with superior antimicrobial activity.

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.

We have conducted two-dimensional computations of vortex-induced vibration of an elastically mounted circular cylinder colliding with a rigid wall at a Reynolds number of 300. For wide ranges of reduced velocities, we have identified C (chaotic), P (periodic), and QP (quasi-periodic) vortex shedding modes at two gap and mass ratios. The deflected gap flow induced by the wall shear layer during the descending motion of the cylinder cause stretching of the vortex strands, while both the P and QP modes show the “S”-type shedding signature. The pathlines for the C-mode yield unstable hyperbolic behavior, whereas twisted knots and spirals are seen for the P-mode. Criss-cross interactions with the swirling pathlines are observed in the QP-mode.