19672 research outputs found
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Density functional theory simulation of cobalt oxide aggregation and facile synthesis of a cobalt oxide, gold and multiwalled carbon nanotube based ternary composite for a high performance supercapattery
No full textA novel ternary composite consisting of cobalt oxide (Co3O4) nanoparticles (NPs) grown on multiwalled carbon nanotubes (MWCNTs) and mixed with gold (Au) NPs is synthesized by a single step hydrothermal route. Initially, density functional theory (DFT) simulations were carried out to model the aggregation of Co3O4 NPs and validated further with experimental results. To circumvent this issue, MWCNTs with gold NPs were introduced, which significantly reduced the particle aggregation. Standard three electrode cell studies revealed that the Co3O4/Au@MWCNT composite possesses an excellent energy density, rate capability and very good cyclic stability compared to unsupported Co3O4 or the binary Co3O4@MWCNT. The promising electrochemical performance compared to the single Co3O4 or the binary Co3O4@MWCNT materials is assigned to the synergetic effects of MWCNTs and Au to disaggregate the Co3O4 NPs and to enhance the overall conductivity, respectively. In order to get insight into the evaluation of the performance, two electrode devices were assembled employing activated carbon as a negative electrode and the Co3O4/Au@MWCNT composite as a positive electrode material. The two electrode supercapattery device demonstrated splendid cycling stability with a retention value of 91.90% in 1 M KOH for over 3500 cycles. Additionally, it exhibited an excellent energy density of 18.80 W h kg-1 at a power density of 302.00 W kg-1. These encouraging outcomes can be associated with the distinctive morphology, outstanding conductive networks, increased electroactive sites, and emergence of strong networking of Co3O4, MWCNT and Au in the ternary composite. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique
Characterization of Sulfur-Compounds as Chemotaxonomic Markers in the Essential Oils of Allium Species by Solvent-Free Microwave Extraction and Gas Chromatography–Mass Spectrometry
No full textAllium species were examined to authenticate the chemotaxonomic controversy about these plants by analyzing their extracted compound profiles. Essential oils of various species were isolated using conventional hydro-distillation and solvent-free microwave extraction (SFME). A comparison of the isolation procedures was performed. The presence of sulfur compounds in the Allium genus is a prominent characteristic for their medicinal uses. These components were characterized using two-way hierarchical cluster analysis (HCA) and principal component analysis (PCA). The variation of sulfur-compounds was performed by qualitative analysis of Allium species by gas chromatography–mass spectrometry (GC–MS). 2,4-Dimethyl-5,6-dithia-2,7-nonadienal, 4,6-diethyl-1,2,3,5-tetrathiolane, and 5,7-diethyl-1,2,3,4,6-pentathiepane were revealed as potential chemotaxonomic markers for all of the Alliums examined in this study. These markers may be used to provide improved systematics for other Allium species. © 2018, © 2018 Taylor & Francis
Insights into Heterologous Biosynthesis of Arteannuin B and Artemisinin in Physcomitrella patens
No full textMetabolic engineering is an integrated bioengineering approach, which has made considerable progress in producing terpenoids in plants and fermentable hosts. Here, the full biosynthetic pathway of artemisinin, originating from Artemisia annua, was integrated into the moss Physcomitrella patens. Different combinations of the five artemisinin biosynthesis genes were ectopically expressed in P. patens to study biosynthesis pathway activity, but also to ensure survival of successful transformants. Transformation of the first pathway gene, ADS, into P. patens resulted in the accumulation of the expected metabolite, amorpha-4,11-diene, and also accumulation of a second product, arteannuin B. This demonstrates the presence of endogenous promiscuous enzyme activity, possibly cytochrome P450s, in P. patens. Introduction of three pathway genes, ADSCYP71AV1- ADH1 or ADS-DBR2-ALDH1 both led to the accumulation of artemisinin, hinting at the presence of one or more endogenous enzymes in P. patens that can complement the partial pathways to full pathway activity. Transgenic P. patens lines containing the different gene combinations produce artemisinin in varying amounts. The pathway gene expression in the transgenic moss lines correlates well with the chemical profile of pathway products. Moreover, expression of the pathway genes resulted in lipid body formation in all transgenic moss lines, suggesting that these may have a function in sequestration of heterologous metabolites. This work thus provides novel insights into the metabolic response of P. patens and its complementation potential for A. annua artemisinin pathway genes. Identification of the related endogenous P. patens genes could contribute to a further successful metabolic engineering of artemisinin biosynthesis, as well as bioengineering of other high-value terpenoids in P. patens. © 2019 by the authors
Surface and optical characteristics of polycrystalline GaN layer with different pores profile of porous GaAs/GaAs substrate
No full textThis work investigated the influence of pores profile of a porous GaAs/GaAs substrate on surface and optical characteristics of an over-deposited GaN layer. Different pores profile of the porous GaAs/GaAs substrate was introduced by varying the DMF concentration of 50%, 75% and 90%. The pores distribution is more uniform, while the pores size is bigger with higher DMF concentration. In contrast, the pores depth is less deep when the DMF concentration was higher than 75%. Next, the GaN layer was deposited onto the porous GaAs/GaAs substrate using an e-beam evaporator system, followed by thermal annealing in ammonia ambient. It was found that the porous GaAs/GaAs substrate, etched by the DMF concentration above 75% gave lower surface roughness to the polycrystalline GaN layer although the surface morphology showed no significant changes. XRD measurement showed on non-porous substrate favoured hexagonal growth in the polycrystalline GaN layer. Instead, the porous GaAs/GaAs substrate favoured the cubic growth, especially the porous GaAs/GaAs substrate etched by 75% DMF concentration. Moreover, the GaN layer on the porous GaAs/GaAs substrate etched by 75% DMF concentration showed the smallest FWHM of NBE peak emission, while exhibited a relaxation level closer to a reported stress-free bulk GaN, as compared to other samples. After all, the porous GaAs/GaAs substrate, etched by 75% DMF concentration has improved the surface and optical characteristics of the layer due to its better porosity. © 2019 IOP Publishing Ltd
Grim consequences of workplace traditional bullying and cyberbullying by way of mediation: A case of service sector of Pakistan
No full textVarious studies have been conducted to measure bullying incidence and prevalence in multiple organizational settings based on a variety of methods and research design. Nonetheless, these studies indicate that bullying is a devastating and crippling problem that should be addressed in relation to its adverse effects and implications. This study identified several gaps in the literature when expanded specifically to the service sector of Pakistan, where the problem of bullying is prevalent. This research endeavored to fill in the aforementioned gaps by precisely focusing on organizational climate as a cause of bullying (based on frustration–aggression theory and social interaction approach), technology in relation to cyberbullying, and effects on employee health. Hence, this study contributes to the emergent discussion in identifying the debilitating outcomes of bullying. Results indicated the significant negative relationship of organizational climate and workplace bullying and the grim consequences on employees' health in the form of psychological, physiological, and emotional health distractions. © 2019, Blue Eyes Intelligence Engineering and Sciences Publication. All rights reserved
Geological assessment for tunnel excavation under river with shallow overburden using surface site investigation data and electrical resistivity tomography
No full textTunnelling is a challenging task as many geotechnical uncertainties involved during construction, especially under a river crossing with shallow overburden. This study focussed on geological assessment for the New Austrian Tunneling Method excavation that crosses under Kerau River with shallow overburden. 3D filtered tunnel models using Boolean filter for rock mass weathering grade, rock quality designation, and Lugeon value are developed. Results predict that 53.3% of the tunnel excavation under the Kerau River crossing are highly weathered rocks (Grades III and IV), and 64.51% are in the moderately to highly fractured zone (0%–75% RQD) along the roof of the tunnel granitic bedrock. The Lugeon value models show that 71.64% of the excavating rocks possess a Lugeon value of 5–50 (6–60 × 10−5 cm/s), which denotes considerably high permeability. 2D electrical resistivity tomography is used to verify the permeability results from the Lugeon test. © 2019 Elsevier Lt
Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system
No full textSustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector”s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow. © 2019 ANAME Publication
Synthesis of a Novel Ladder Poly(azomethine-ester) Based on PET Waste Bottles
No full textIn the present investigation, a novel ladder polymer, poly(azomethine ester), was prepared via solution polycondensation polymerization between terephthalic acid and the novel monomer. Terephthalic acid was regenerated from PET waste bottles by saponification process, whereas p-phenylenediamine was obtained via Hoffmann rearrangement method. A novel monomer, namely N,N’-bis(2,5-dihydroxy benzylidene)-1,4-diaminobenzene was prepared from the reaction of 2,5-di-hydroxybenzadehyde with p-phenylenediamine in the ratio of 2:1, respectively. For the first time a solution polycondensation method has been employed for the synthesis of a ladder polymer which is otherwise prepared commonly via Diels-Al-der cycloaddition reaction. The synthesized ladder polymer was characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR), elemental analysis (CHN), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results revealed that the ladder polymer possess highly regular ladder like framework, and that most of the ester groups have taken part in the side-by-side polymerization reaction. © Carl Hanser Verlag, Munich Intern
Validation of smartphone free heart rate monitoring application during treadmill exercise (Validação de aplicativo gratuito de smartphone para monitoramento da frequência cardíaca durante exercício em esteira) (Validación de aplicación gratuita de smartphone para monitorización de la frecuencia cardíaca durante ejercicio en cinta)
No full textObjective: The number of people participating in leisure sports activities and amateur competitions has been rising sharply. Free smartphone heart rate monitoring applications are readily available for use; however, information on their accuracy during exercise is still limited. Therefore, the purpose of our study was to validate a smartphone free heart rate monitoring application during treadmill exercise in healthy individuals. Methods: This was a prospective experimental study testing the free heart rate app ‘INSTANT HEART RATE: AZUMIO.’ Twenty-seven healthy participants were requested to perform the treadmill task with four different workloads: walking at 2.0 mph, walking at 3.5 mph, jogging at 4.5 mph and running at 6.0 mph. Participants had to perform the exercises for 3 minutes for each workload, and heart rates were recorded using the smartphone app and ECG at rest, during the exercise and recovery periods at each 60-second interval. Results: Heart rates measured using the free smartphone app at rest, walking at 2.0 mph, brisk walking at 3.5 mph, slow jogging at 4.5 mph and recovery stage were accurate with correlation coefficient value ≥0.95 and standard error of estimate 5 bpm. Conclusion: The free smartphone app that we tested accurately estimates heart rate at rest, during low to moderate intensity exercise and the recovery period, but becomes less consistent during high-intensity exercise, making this app suitable for use during indoor activities of low to moderate intensity. Level of evidence II; Diagnostic Studies - Investigating a diagnostic test. © 2019, Redprint Editora Ltda. All rights reserved
New Texture Descriptor Based on Modified Fractional Entropy for Digital Image Splicing Forgery Detection
No full textForgery in digital images is immensely affected by the improvement of image manipulation tools. Image forgery can be classified as image splicing or copy-move on the basis of the image manipulation type. Image splicing involves creating a new tampered image by merging the components of one or more images. Moreover, image splicing disrupts the content and causes abnormality in the features of a tampered image. Most of the proposed algorithms are incapable of accurately classifying high-dimension feature vectors. Thus, the current study focuses on improving the accuracy of image splicing detection with low-dimension feature vectors. This study also proposes an approximated Machado fractional entropy (AMFE) of the discrete wavelet transform (DWT) to effectively capture splicing artifacts inside an image. AMFE is used as a new fractional texture descriptor, while DWT is applied to decompose the input image into a number of sub-images with different frequency bands. The standard image dataset CASIA v2 was used to evaluate the proposed approach. Superior detection accuracy and positive and false positive rates were achieved compared with other state-of-the-art approaches with a low-dimension of feature vectors. © 2019 by the authors