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61.
利用电化学衰减全反射原位傅里叶变换红外光谱与微分电化学质谱联用技术,在流动电解池环境以及恒电位条件下研究了Pt电极和Pt电极通过表面电沉积Ru形成的PtRu电极(PtxRuy)上发生的甲醇氧化反应(反应电解质溶液为0.1 mol/L HClO4+0.5 mol/L MeOH). 在0.3~0.6 V(参比电极为可逆氢参比)实验用到的所有电极上,CO是唯一能从红外光谱观察到的与甲醇相关的表面吸附物;在Pt0.56Ru0.44电极上可以观察到CO吸附在Ru原子形成的岛上和CO线式吸附在Pt电极表面红外波段,而其他电极上只能观察到Pt表面上线式吸附的CO;甲醇氧化活性按Pt0.73Ru0.27>Pt0.56Ru0.44>Pt0.83Ru0.17>Pt的顺序递减;在0.5 V 时,甲醇在Pt0.73Ru0.27电极上的氧化反应的CO2电流效率达到了50%. 相似文献
62.
Hassan Yousif Ahmed M. Almaleeh Hilal Fadhil S.A. Aljunid Ammar Elyass N.M. Saad 《Optik》2012,123(15):1352-1359
This paper investigates the performance of vector combinatorial (VC) code for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a newly proposed subtract exclusive OR detection (SED) technique. VC code is constructed using Euclidean vector and algebraic ways. One of the important properties of this code is that the maximum cross correlation is one, which means that multi-user interference (MUI) and phase induced intensity noise (PIIN) are reduced. The weight for the VC code can be any positive integer number. The system performance was evaluated by comparing the theoretical studies using related equations and simulation results taken from the commercial optical systems, “VPI? TransmissionMaker 7.1”. Significant improvement in system performances has been observed when the proposed SED technique employing VC code was applied compared to other codes that utilize conventional balance detection techniques for spectral amplitude coding. 相似文献
63.
Performance scaling of passively mode-locked ultrashort-pulse fiber oscillators in terms of average power, peak power, and pulse energy is demonstrated. A very-large-mode-area fiber laser in an all-positive group-velocity-dispersion ring cavity configuration with intracavity spectral filter, mode-locked by nonlinear polarization evolution, emits 66 W of average power at 76 MHz repetition rate, corresponding to 0.9 μJ pulse energy. The pulses are dechirped to 91 fs outside the cavity with an average power of 60 W remaining after the compressor. The generated pulse peak power is as high as 7 MW. 相似文献
64.
Abdo A Saeed F Hamza H Ahmed A Salim N 《Journal of computer-aided molecular design》2012,26(3):279-287
Query expansion is the process of reformulating an original query to improve retrieval performance in information retrieval
systems. Relevance feedback is one of the most useful query modification techniques in information retrieval systems. In this
paper, we introduce query expansion into ligand-based virtual screening (LBVS) using the relevance feedback technique. In
this approach, a few high-ranking molecules of unknown activity are filtered from the outputs of a Bayesian inference network
based on a single ligand molecule to form a set of ligand molecules. This set of ligand molecules is used to form a new ligand
molecule. Simulated virtual screening experiments with the MDL Drug Data Report and maximum unbiased validation data sets
show that the use of ligand expansion provides a very simple way of improving the LBVS, especially when the active molecules
being sought have a high degree of structural heterogeneity. However, the effectiveness of the ligand expansion is slightly
less when structurally-homogeneous sets of actives are being sought. 相似文献
65.
Hussein Osman Ammar S. A. El-Nahhas M. M. Ghorab A. H. Salama 《Journal of inclusion phenomena and macrocyclic chemistry》2012,72(1-2):127-136
One of the most attractive areas of research in drug delivery is the design of nanomedicines consisting of nanosystems that are able to deliver drugs to the right place, at appropriate time. Natural polysaccharides, due to their outstanding merits, have received more and more attention in the field of drug delivery systems. In particular, polysaccharides seem to be the most promising materials in the preparation of nanometric carriers. The main goal of the present study was to investigate the potential of a recent generation of hybrid polysaccharide nanocarriers, composed of chitosan (CS) and an anionic cyclodextrin, carboxymethyl-β-cyclodextrin (CM-β-CD), for the encapsulation of a model drug, sulindac. CS and CM-β-CD were processed to nanoparticles (NPs) via the ionotropic gelation technique. The stoichiometric ratio between these two polymers was found to influence particle size and zeta potential. Decreasing CS:CM-β-CD ratio led to an increase in particle size and decrease in zeta potential. DSC and FTIR analyses confirmed formation of NPs and encapsulation of sulindac inside them. Release profiles indicate a continuous release of the drug throughout 24?h. However, the rate of release was more rapid during the first hours; about 55–90% of the drug being released after 3?h. 相似文献
66.
Mohamed Ali Mahjoub Samia Ammar Kaouther Majouli Zine Mighri 《Chemistry of Natural Compounds》2012,47(6):955-958
Two new alkaloid derivatives of the 3-benzazocine skeleton (cotuzine A and B) and a new polyphenolic substance (3-(1,3-dihydroxyprop-2-yl)-4-hydroxyanisol)
(corimen) have been isolated from the aerial part (stems, leaves) of the plant Cotula coronopifolia (L.). These three new
structures were established by spectroscopic procedures (1H, 13C, one- and two-dimensional NMR). The stereochemistry of the new alkaloids was established based on different NOE effects
revealed on the NOESY spectrum. Mass spectrometry and IR spectroscopy were used to confirm these structures. 相似文献
67.
Houcine Ammar Fatma Abdelkafi Souhir Abid Bouchra Benjelloum-Mlayah Rachid El Gharbi Michel Delmas 《Chemistry of Natural Compounds》2012,48(1):99-102
Alfa grass pulping was successfully performed in hydro-organic acid medium under mild conditions (107°C, atmospheric pressure, cooking
time: 3 h). Use of an acetic acid/formic acid/water mixture as pulping liquor was perfectly suitable for selective isolation
of pulp, lignin, and hemicelluloses. The unbleached pulp obtained in good yield was first delignified by peroxyacids in organic
acid medium and then bleached with hydrogen peroxide in a basic medium to give pulp offering good physico-chemical and mechanical
characteristics. 相似文献
68.
Mohamad M.E. Shakdofa Hanan A. Mousa Ahmed M.A. Elseidy Ammar A. Labib Mamdouh M. Ali Amira S. Abd‐El‐All 《应用有机金属化学》2018,32(1)
Thiosemicarbazone ligand, 2‐((4,9‐dimethoxy‐5‐oxo‐5H‐furo[3,2‐g]chromen‐6‐yl)methylene) hydrazinecarbothioamide and its Cd(II), Cu(II), Zn(II), Ni(II), Co(II), VO(II), and Mn(II) complexes have been prepared and characterized by various spectroscopic and analytical techniques. Complexes molar conductance measurements displayed that all complexes (2–8) are non‐electrolyte. With general composition [M(H3L)(CH3COO)2H2O].nH2O, where M = Cd(II), Cu(II), Zn(II), Ni(II), Co(II) and Mn(II) while complex (8) has [VO(H3L)(SO4)H2O].2H2O formula. Based on analytical and spectral measurements, the octahedral or distorted octahedral geometries suggested for complexes. Ligand and complexes anti‐proliferative activities were assessed against three various human tumor cell lines including breast cancer (MCF‐7), liver cancer (HepG2) and lung cancer (A549) using SRB fluorometric assay and cis‐platin as positive control. The anti‐proliferative activity result indicated that the ligand and its complexes have considerable anti‐proliferative activity analogous to that of ordinarily utilized anti‐cancer drug (cis‐platin). They do their anti‐cancer activities by modifying free radical's generation via raising the superoxide dismutase activity and depletion of intracellular reduced glutathione level, catalase, glutathione peroxidase activities, escorted by highly generation of hydrogen peroxide, nitric oxide and other free radicals leading to tumor cells death, as monitoring by decreasing the protein and nucleic acids synthesis. 相似文献
69.
Rupak Mukherjee Surabhi Jaiswal Manish K. Shukla Ammar Hakim Edward Thomas 《等离子体物理论文集》2020,60(4):e201900161
A new concept called “configurational temperature” is introduced in the context of dusty plasma, where the temperature of the dust particles submerged in the plasma can be measured directly from the positional information of the individual dust particles and the interaction potential between the dust grains. This method does not require the velocity information of individual particles, which is a key parameter to measure the dust temperature in the conventional method. The technique is initially tested using two-dimensional (2D) OpenMP parallel molecular dynamics and Monte Carlo simulation and then compared with the temperature evaluated from experimental data. The experiment have been carried out in the Dusty Plasma Experimental (DPEx) device, where a 2D stationary plasma crystal of melamine formaldehyde particles is formed in the cathode sheath of a DC glow discharge argon plasma. The kinetic temperature of the dust is calculated using the standard particle image velocimetry technique at different pressures. An extended simulation result for the three-dimensional case is also presented, which can be employed for the temperature measurement of a three-dimensional dust crystal in laboratory devices. 相似文献
70.
Marcelo M. Cavalcanti Ammar Khemmoudj Mohamed Medjden 《Journal of Mathematical Analysis and Applications》2007,328(2):900-930
In this paper, the uniform stabilization of the Cauchy-Ventcel problem with variable coefficients is considered, and the uniform energy decay rate for the problem is established by Riemannian geometry methods. 相似文献