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61.
Electromagnetic interference (EMI) shielding has become a phenomenon of great concern and there is growing demand towards the synthesis of materials with better EMI shielding effectiveness (EMI SE). This work highlights the preparation of Polyaniline-Yttrium Oxide (PANI-Y2O3) composites for EMI shielding applications in the frequency range from 12.4 to 18 GHz (Ku-band). The structure and morphology of the composites were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). EMI SE, microwave absorption and reflection, dielectric properties of the composites are discussed in detail. All the computations were based on microwave scattering parameters measured by transmission line waveguide technique. The observed results show absorption dominant EMI shielding in these composites with EMI SE of ?19 to ?20 dB, which mainly depends on the dielectric loss of the composites. Through the results of our observations, we propose these composites to be potential materials for microwave absorption and EMI shielding applications. 相似文献
62.
Shielded sliding discharges are nanosecond streamer discharges which develop along a dielectric between metal foil electrodes, with one of the foils extended over the entire rear of the dielectric layer. The electrode configuration not only allowed rearranging discharges in parallel due to the decoupling effect of the metal layer, but also to modify the electric field distribution in such a way that components normal to the surface are enhanced, leading to an increased energy density in the discharge plasma. By varying the electrode gap, the applied voltage, and the repetition rate, it is shown that by keeping the average electric field constant, the discharge voltage can be reduced from tens of kV to values on the order of a few kV, but only at the expense of a reduced energy density of the plasma. Varying the repetition rate from 20 to 500 Hz resulted in a slightly reduced energy per pulse, likely caused by residual charges on the dielectric surface. Measurements of the NO conversion to NO2 and ozone synthesis in dry air showed that the conversion is only dependent on the energy density of the discharge plasma. Although reducing the pulse voltage from the tens of kV range to that of few kV, and possibly even lower, causes a reduction in energy density, this loss can be compensated for by increasing the electrode gap area. This and the possibility to form discharge arrays allows generating large volume discharge reactors for environmental applications, at modest pulsed voltages. 相似文献
63.
Meirong Hu Xue Zhou Yiping Shi Jianhui Lin Muhammad Irfan Yong Tao 《Applied biochemistry and biotechnology》2014,174(5):2007-2017
POXA1b is the most thermostable laccase isoenzyme from Pleurotus ostreatus. POXA1b is remarkably stable at alkaline pH (the t1/2 at pH 10 was 30 days), and its C-terminal affects its catalytic and stability properties. We cloned POXA1c from P. florida, which showed 99 % identity with POXA1b. POXA1c was functionally expressed in Pichia pastoris. The functions of the N and C termini of POXA1c were investigated using site-directed mutagenesis. Compared with POXA1c, the N-terminal R5V site effectively increased the specific activities for 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and guaiacol by 2- and 3.5-fold, respectively. A C-terminal truncated mutant, POXA1c△13, also increased the specific activities for ABTS and guaiacol by 2.3- and 3.4-fold, respectively. A double mutant, POXA1cΔ13-R5V, combined the R5V and △13 effects. The specific activity of this double mutant for ABTS was 1,321 U/mg, which indicated a 4-fold increase compared with the wild type. The role of residue V5 on laccase catalytic properties was also observed for laccases from Trametes versicolor and Rigidoporus lignosus. The specific activities of the V5R of the laccases from T. versicolor and R. lignosus were half of that of the wild type. The pH and thermal stability analysis of POXA1c and its mutants showed that the enzymes were remarkably stable because they showed 63 % residual activity after incubation for 108 h at 30 °C over a pH range of 4.5 to 9.0. Similar results were observed for POXA1cΔ13-R5V. POXA1cΔ13-R5V can be widely used in industrial biotechnology because of its excellent catalytic properties. 相似文献
64.
Muhammad Ibrar Ahmed Dr. Chuangwei Liu Dr. Yong Zhao Dr. Wenhao Ren Dr. Xianjue Chen Dr. Sheng Chen Prof. Chuan Zhao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(48):21649-21653
Inspired by the metal–sulfur (M-S) linkages in the nitrogenase enzyme, here we show a surface modification strategy to modulate the electronic structure and improve the N2 availability on a catalytic surface, which suppresses the hydrogen evolution reaction (HER) and improves the rate of NH3 production. Ruthenium nanocrystals anchored on reduced graphene oxide (Ru/rGO) are modified with different aliphatic thiols to achieve M-S linkages. A high faradaic efficiency (11 %) with an improved NH3 yield (50 μg h−1 mg−1) is achieved at −0.1 V vs. RHE in acidic conditions by using dodecanethiol. DFT calculations reveal intermediate N2 adsorption and desorption of the product is achieved by electronic structure modification along with the suppression of the HER by surface modification. The modified catalyst shows excellent stability and recyclability for NH3 production, as confirmed by rigorous control experiments including 15N isotope labeling experiments. 相似文献
65.
A new hybrid organic-inorganic perovskite(HOIP)material,[C6H14N2]KBr3,has been synthesized via hydrothermal method and fully characterized.[C6H14N2]KBr3 has a three-dimensional perovskite structure and crystalizes in a trigonal P3121 space group.The elastic properties of[C6H14N2]KBr3 were fully calculated via the density functional theory calculations,which reveal the elastic moduli(11.54~14.07 GPa),shear moduli(4.56~5.68 GPa),Poisson’s ratios(0.18~0.32),bulk modulus(8.51 GPa)and acoustic velocity(2.57~2.74 kms^-1).Additional nanoindentation experiments in the form of single-crystals confirmed the validity of our theoretical approach.[C6H14N2]KBr3 exhibits higher stiffness and thermal stability than the well-known photovoltaic CH3NH3PbI3,which makes it worthwhile for exploring optoelectronic properties. 相似文献
66.
Yusof Enis Nadia Md. Ishak Nurul N. M. Latif Muhammad A. M. Tahir Mohamed I. M. Sakoff Jennette A. Page Alister J. Tiekink Edward R. T. Ravoof Thahira B. S. A. 《Research on Chemical Intermediates》2020,46(4):2351-2379
Research on Chemical Intermediates - A series of tridentate ONS Schiff bases were synthesised via condensation by reacting 2,3-dihydroxybenzaldehyde with S-2-methylbenzyldithiocarbazate (S2MBDTC)... 相似文献
67.
Khoja Asif Hussain Anwar Mustafa Shakir Sehar Mehran Muhammad Taqi Mazhar Arslan Javed Adeel Amin Nor Aishah Saidina 《Research on Chemical Intermediates》2020,46(8):3817-3833
Research on Chemical Intermediates - The excess emission of greenhouse gases (GHGs) such as CO2 and CH4 is posing an acute threat to the environment, and efficient ways are being sought to utilize... 相似文献
68.
Sajid Muhammad Munir Shad Naveed Akthar Javed Yasir Khan Sadaf Bashir Zhang Zhengjun Amin Nasir 《Research on Chemical Intermediates》2020,46(2):1201-1215
Research on Chemical Intermediates - We prepared unique BiVO4/reduce graphene oxide (BiVO4/rGO) nanocomposite with enhanced photocatalytic ability by hydrothermal method applying... 相似文献
69.
Narayan D. Chaurasiya Jacob Midiwo Pankaj Pandey Regina N. Bwire Robert J. Doerksen Ilias Muhammad Babu L. Tekwani 《Molecules (Basel, Switzerland)》2020,25(22)
A set of structurally related O-methylated flavonoid natural products isolated from Senecio roseiflorus (1), Polygonum senegalense (2 and 3), Bhaphia macrocalyx (4), Gardenia ternifolia (5), and Psiadia punctulata (6) plant species were characterized for their interaction with human monoamine oxidases (MAO-A and -B) in vitro. Compounds 1, 2, and 5 showed selective inhibition of MAO-A, while 4 and 6 showed selective inhibition of MAO-B. Compound 3 showed ~2-fold selectivity towards inhibition of MAO-A. Binding of compounds 1–3 and 5 with MAO-A, and compounds 3 and 6 with MAO-B was reversible and not time-independent. The analysis of enzyme-inhibition kinetics suggested a reversible-competitive mechanism for inhibition of MAO-A by 1 and 3, while a partially-reversible mixed-type inhibition by 5. Similarly, enzyme inhibition-kinetics analysis with compounds 3, 4, and 6, suggested a competitive reversible inhibition of MAO-B. The molecular docking study suggested that 1 selectively interacts with the active-site of human MAO-A near N5 of FAD. The calculated binding free energies of the O-methylated flavonoids (1 and 4–6) and chalcones (2 and 3) to MAO-A matched closely with the trend in the experimental IC50′s. Analysis of the binding free-energies suggested better interaction of 4 and 6 with MAO-B than with MAO-A. The natural O-methylated flavonoid (1) with highly potent inhibition (IC50 33 nM; Ki 37.9 nM) and >292 fold selectivity against human MAO-A (vs. MAO-B) provides a new drug lead for the treatment of neurological disorders. 相似文献
70.
Dr. Kai Lin Woon Siti Aisyah Syaerah Mustapa Nor Shafiq Mohd Jamel Dr. Vannajan Sanghiran Lee Muhammad Zhafran Zakaria Dr. Azhar Ariffin 《Chemphyschem》2020,21(22):2620-2626
Material designs that use donor and acceptor units are often found in organic optoelectronic devices. Molecular level insight into the interactions between donors and acceptors are crucial for understanding how such interactions can modify the optical properties of the organic optoelectronic materials. In this paper, tris(4-(tert-butyl)phenyl)amine (pTPA) was synthesized as a donor in order to compare with unmodified triphenylamine (TPA) in a donor–acceptor system by having 2,4,6-triphenyl-1,3,5-triazine (TRZ) as an acceptor. Dimerization of donors and acceptors occurred in solvent when the concentration of solute is high. At 0 K, using a polarizable continuum model, the nitrogen atom of TPA is found to stack on top of the center of triazine of TRZ, whereas such alignment is offset in pTPA and TRZ. We attributed such alignment in TPA-TRZ as the result of attractive interactions between partial localization of 2pz electrons at the nitrogen atom of TPA and the π deficiency of triazine in TPA-TRZ. By taking into account random motions of the solvent effect at 300 K in quantum molecular dynamics and classical molecular dynamics simulations to interpret the marked difference in emission spectra between TPA-TRZ and pTPA-TRZ, it was revealed that the attractive interaction between pTPA and TRZ in toluene is weaker than TPA and TRZ. Because of the weaker attractive interaction between pTPA and TRZ in toluene, the dimers adopted numerous ground state conformations resulting in broad emission bands superimposed with multiple small Gaussian peaks. This is in contrast to TPA-TRZ which has only one dominant dimer conformation. This study demonstrates that the strength of intermolecular interactions between donors and acceptors should be taken into consideration in designing supramolecular structures. 相似文献