19672 research outputs found
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Fault-Tolerant Field-Oriented Control of Three-Phase Induction Motor Based on Unified Feedforward Method
No full textWith the increasing proliferation of variable speed drive, the demand for the more reliable drive is also on the rise. Despite the growing interest on more advanced motors like permanent magnet and flux switching motors, three-phase induction motors (3ph-IMs) are still the main workhorse in the industry and hence the fault-tolerant control of these motor drives remains an interesting and important topic. In this paper, a simple fault-tolerant field-oriented control technique for 3ph-IMs is presented. It is shown that by injecting zero-sequence compensation voltage in a feedforward manner, open-circuit faults can be effectively tolerated. Compared to the previous feedforward fault-tolerant control methods, the proposed approach does not require the knowledge of the magnetizing inductance, which is tricky to be obtained in induction motors. Furthermore, the unified feedforward approach allows the same control structure to be used for different fault-tolerant 3ph-IMs drive topologies, with minor modifications to the feedforward terms. In addition, the effect of inverter non-idealities on the performance of the proposed control method is also highlighted and addressed. The effectiveness of the proposed controller is verified using MATLAB simulation and further validated using experimental tests. This paper is accompanied by a video demonstrating the experimental results. © 1986-2012 IEEE
Electrostatic interactions at the five-fold axis alter heparin-binding phenotype and drive enterovirus A71 virulence in mice
No full textEnterovirus A71 (EV-A71) causes hand, foot and mouth disease epidemics with neurological complications and fatalities. However, the neuropathogenesis of EV-A71 remains poorly understood. In mice, adaptation and virulence determinants have been mapped to mutations at VP2-149, VP1-145 and VP1-244. We investigate how these amino acids alter heparin-binding phenotype and shapes EV-A71 virulence in one-day old mice. We constructed six viruses with varying residues at VP1-98, VP1-145 (which are both heparin-binding determinants) and VP2-149 (based on the wild type 149K/98E/145Q, termed KEQ) to generate KKQ, KKE, KEE, IEE and IEQ variants. We demonstrated that the weak heparin-binder IEE was highly lethal in mice. The initially strong heparin-binding IEQ variant acquired an additional mutation VP1-K244E, which confers weak heparin-binding phenotype resulting in elevated viremia and increased virus antigens in mice brain, with subsequent high virulence. IEE and IEQ-244E variants inoculated into mice disseminated efficiently and displayed high viremia. Increasing polymerase fidelity and impairing recombination of IEQ attenuated the virulence, suggesting the importance of population diversity in EV-A71 pathogenesis in vivo. Combining in silico docking and deep sequencing approaches, we inferred that virus population diversity is shaped by electrostatic interactions at the five-fold axis of the virus surface. Electrostatic surface charges facilitate virus adaptation by generating poor heparin-binding variants for better in vivo dissemination in mice, likely due to reduced adsorption to heparinrich peripheral tissues, which ultimately results in increased neurovirulence. The dynamic switching between heparin-binding and weak heparin-binding phenotype in vivo explained the neurovirulence of EV-A71. © 2019 Public Library of Science. All rights reserved
Molecular interaction study of an anticancer drug, ponatinib with human serum albumin using spectroscopic and molecular docking methods
No full textBinding of a potent anticancer agent, ponatinib (PTB) to human serum albumin (HSA), main ligand transporter in blood plasma was analyzed with several spectral techniques such as fluorescence, absorption and circular dichroism along with molecular docking studies. Decrease in the K SV value with increasing temperature pointed towards PTB-induced quenching as the static quenching, thus affirming complexation between PTB and HSA. An intermediate binding affinity was found to stabilize the PTB-HSA complex, as suggested by the K a value. Thermodynamic analysis of the binding phenomenon revealed participation of hydrophobic and van der Waals interactions along with hydrogen bonds, which was also supported by molecular docking analysis. Changes in both secondary and tertiary structures as well as in the microenvironment around Trp and Tyr residues of HSA were anticipated upon PTB binding to the protein, as manifested from circular dichroism and three-dimensional fluorescence spectra, respectively. Binding of PTB to HSA led to protein's thermal stabilization. Competitive ligand displacement experiments using different site markers such as warfarin, indomethacin and ketoprofen disclosed the binding site of PTB as Sudlow's site I in HSA, which was further confirmed by molecular docking analysis. © 2019 Elsevier B.V
Valorization of Nutraceutical Industrial Coriander Seed Spent by the Process of Sustainable Adsorption System of Acid Black 52 from Aqueous Solution
No full textThe potential usage of coriander seed spent which is a nutraceutical industrial by-product in the removal of Acid Black 52 (AB52) dye from aqueous solutions was evaluated with respect to various experimental parameters including pH, initial dye concentration, adsorbent dosage, adsorbent particle size, duration of contact time and temperature. The optimal qe value at pH 2, pH 7 and pH 12 was 432 mg g−1, 164 mg g−1 and 220 mg g−1, respectively. Two-level fractional factorial experimental design model yielded maximum adsorption value of 867.00 mg g−1. The influence of each parameter and combination of parameters on the final adsorption capacity of the system has been shown by analysis of variance (ANOVA). Equilibrium data were analyzed by four two-parameter and five three-parameter isotherm models. The dye uptake obeyed pseudo-second order kinetic expression. Intra-particle diffusion showed that the adsorption mechanism was more governed by external mass transfer. AB52 dye adsorption on nutraceutical industrial coriander seed spent (NICSS) was endothermic and almost spontaneous. The NICSS has a highly fibrous matrix with hierarchical porous structure as evidenced by SEM images. The FTIR analysis of the spent confirmed the presence of cellulosic and ligno-cellulosic matter imparting both hydrophilic and hydrophobic properties. The results proved that NICSS efficiently removes AB52 dye from water and textile industrial effluent. © 2019, University of Tehran
Evaluating system of rice intensification using a modified transplanter: A smart farming solution toward sustainability of paddy fields in Malaysia
No full textThis study reports on evaluating a new transplanting operation by taking into accounts the interactions between soil, plant, and machine in line with the System of Rice Intensification (SRI) practices. The objective was to modify planting claw (kuku-kambing) of a paddy transplanter in compliance with SRI guidelines to determine the best planting spacing (S), seed rate (G) and planting pattern that results in a maximum number of seedling, tillers per hill, and yield. Two separate experiments were carried out in two different paddy fields, one to determine the best planting spacing (S=4 levels: s 1 =0.16 m×0.3 m, s 2 = 0.18 m×0.3 m, s 3 =0.21 m×0.3 m, and s 4 =0.24 m×0.3 m) for a specific planting pattern (row mat or scattered planting pattern), and the other to determine the best combination of spacing with seed rate treatments (G=2 levels: g 1 =75 g/tray, and g 2 = 240 g/tray). Main SRI management practices such as soil characteristics of the sites, planting depth, missing hill, hill population, the number of seedling per hill, and yield components were evaluated. Results of two-way analysis of variance with three replications showed that spacing, planting pattern and seed rate affected the number of one-seedling in all experiment. It was also observed that the increase in spacing resulted in more tillers and more panicle per plant, however hill population and sterility ratio increased with the decrease in spacing. While the maximum number of panicles were resulted from scattered planting at s 4 =0.24 m×0.3 m spacing with the seed rate of g 1 =75 g/tray, the maximum number of one seedling were observed at s 4 =0.16 m×0.3 m. The highest and lowest yields were obtained from 75 g seeds per tray scattered and 70 g seeds per tray scattered treatment respectively. For all treatments, the result clearly indicates an increase in yield with an increase in spacing. © 2019, Chinese Society of Agricultural Engineering. All rights reserved
Hybrid nanocellulose/f-MWCNTs nanocomposite for the electrochemical sensing of diclofenac sodium in pharmaceutical drugs and biological fluids
No full textA nanocomposite from a green nanomaterial (nanocellulose) and f-MWCNTs was modified onto glassy carbon (GC) electrode for the detection of diclofenac sodium (DCF), a non-steroidal anti-inflammatory drug (NSAID) and widely used electroactive painkiller. The presence of OH groups in the nanocellulose provides more binding sites for different analytes. This ensures an axial modulus rearrangement and the incorporation of f-MWCNTs which provides larger surface area, high mechanical strength and improved electrical conductivity. On the other hand, the synergy between both compounds enhances the electrochemical detection of DCF in human blood and urine. Under optimum conditions, the modified electrode exhibited a remarkable improvement in the anodic peak current (41.6 μA) for 50 μM DCF at 0.677 V peak potential. The newly fabricated electrode showed two linear dynamic ranges from 0.05 to 1.00 μM and 2–250 μM DCF with low detection limit of 0.012 μM. In addition, differential pulse voltammetry (DPV) and cyclic voltammetry (CV) showed good sensitivity and selectivity for the determination of DCF. With this technique, the modified electrode was very effective and suitable for DCF determination from commercial tablets, ampoules (pharmaceutical preparations) and also from clinical preparations (human blood serum and urine sample) with good recoveries. © 2019 Elsevier Lt
Metallization of Silver Through Coffee‐Ring Assisted Ribonucleic Acid Scaffolding Technique
No full textPreferential binding of base pair units with metallic ions within deoxyribonucleic acids (DNA) to form metal-DNA complexes are well studied and understood. Excitingly, such natural processes have been utilized “artificially” for designing and fabricating nanometallic structures and patterns primarily using double stranded DNA. However, little or no effort has been given to ribonucleic acid or RNA in this aspect. Therefore, in this work we study the scaffolding effect of RNA on metalizing silver (Ag) ions and further the diffusion of majority of the Ag-RNA complexes towards artificially introduced cut or scribed edges as a result of the coffee-ring effect. Upon removal of the RNA scaffold, metallic nanostructures remain along the line of the cut corresponding to the micrometre scale length of the cut, exercising some amount of control and manipulation of parameter. Other parameters such as the height and diameter may directly be related to the concentration and diffusion of the Ag-RNA complexes, while gap size related to the cut width. We anticipate that further in-depth studies will be required before a comprehensive model could be proposed for highly controllable and flexible nanostructure and nanowire fabrication using nucleic acid scaffolding techniques. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinhei
Photo-induced Aggregation of Single-walled Carbon Nanotubes from Dispersion by Using a Photochromic Dispersant
No full textDipropylheterocoerdianthrone (DPHCD) was found to be a potential photo-reactive dispersant of single-walled carbon nanotubes (SWNTs). DPHCD was able to well disperse SWNTs in chloroform. DPHCD is easily photo-oxidized by the irradiation of visible light to form the endoperoxide with a bent structure under oxygen or air atmosphere. Then, SWNTs were photo-precipitated from the DPHCD/SWNTs dispersion. The precipitation was able to disperse again after the photochromic reaction to turn back DPHCD from the endoperoxide and sonication. Such photo-induced precipitation was also observed in DPHCD/SWNTs complex film. The SWNTs precipitates were analyzed by FT-IR and Raman spectra measurements, and discussed about selectivity of DPHCD on chirality, and elimination of the dispersant. © 2019 SPST
Factors that inhibit science teachers' implementation of learner autonomy after a professional development collaboration
No full textDeveloping learner autonomy can improve learners' outcomes. Teaching students autonomy is a cultural endeavour. Therefore teachers operating from an Asian heritage may struggle to implement learner autonomy. Teachers face several pressures when implementing learner autonomy, and require development. This paper investigates what prevented science teachers from implementing autonomy-supportive strategies after a Collaborative Professional Development Programme (CPDP). CPDP guides science teachers to implement learner autonomy, with Assessment for Learning (AfL) principles. It flexibly and expertly encourages teachers to strategise their autonomy. This study is part of a more extensive study. Three primary science teachers participated in the CPDP. They were interviewed afterwards to elicit inhibiting factors, which included lack of time to prepare students for examinations and resources (pressure from above); non-cooperative students (pressure from below) and teachers' beliefs that students were unable to become autonomous (pressure from within). Detailed recommendations are given, with implications for professional programme developers and policymakers.. © 2019 Primrose Hall Publishing Group
Gastroprotective activity of a novel Schiff base derived dibromo substituted compound against ethanol-induced acute gastric lesions in rats
No full textBackground: Basic function of bromine in body is to activate pepsin production in gastritis with low acidity. The present study encompasses a broad in vivo study to evaluate gastroprotective activity of a novel dibromo substituted Schiff base complex against Sprague Dawley (SD) rats. Methods: 2, 2-[1, 2-cyclohexanediylbis (nitriloethylidyne)]bis(4-bromophenol) (CNBP) is synthesized via a Schiff base reaction, using the related ketone and diamine as the starting materials. SD rats are divided as normal, ulcer control (5 ml/kg of 10% Tween 20), testing (10 and 20 mg/kg of CNBP) and reference groups (omeprazole 20 mg/kg). Except for the normal group, the rest of the groups are induced gastric ulcer by ethanol 1 h after the pre-treatment. Ulcer area, gastric wall mucus, and acidity of gastric content of the animal stomachs are measured after euthanization. Antioxidant activity of the compound is tested by Ferric reducing antioxidant power (FRAP) test and safety of the compound is identified through acute toxicity by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, activities of superoxide dismutase (SOD), catalase (CAT), levels of prostaglandins E2 (PGE2) and also malondialdehyde (MDA) are determined. Results: Antioxidant activity of CNBP was approved via FRAP assay. Vast shallow hemorrhagic injury of gastric glandular mucosa was observed in the ulcer group compared to the CNBP-treated animals. Histological evaluations confirmed stomach epithelial defense effect of CNBP with drastic decrease of gastric ulceration, edema and leucocytes penetration of submucosal stratum. Immunostaining exhibited over-expression in HSP70 protein in CNBP-treated groups compared to that of the ulcer group. Also, gastric protein analysis showed low levels of MDA, PGE2 and high activity of SOD and CAT. Conclusions: CNBP with noticeable antioxidant property showed gastroprotective activity in the testing rodents via alteration of HSP70 protein expression. Also, antioxidant enzyme activities which were changed after treatment with CNBP in the animals could be elucidated as its gastroprotective properties. © The Author(s). 2019