排序方式: 共有81条查询结果,搜索用时 703 毫秒
11.
Bert J. Debusschere Youssef M. Marzouk Habib N. Najm Blane Rhoads Dimitris A. Goussis Mauro Valorani 《Combustion Theory and Modelling》2013,17(1):173-198
This paper presents a novel tabulation strategy for the adaptive numerical integration of chemical kinetics using the computational singular perturbation (CSP) method. The strategy stores and reuses CSP quantities required to filter out fast dissipative processes, resulting in a non-stiff chemical source term. In particular, non-parametric regression on low-dimensional slow invariant manifolds (SIMs) in the chemical state space is used to approximate the CSP vectors spanning the fast chemical subspace and the associated fast chemical time-scales. The relevant manifold and its dimension varies depending on the local number of exhausted modes at every location in the chemical state space. Multiple manifolds are therefore tabulated, corresponding to different numbers of exhausted modes (dimensions) and associated radical species. Non-parametric representations are inherently adaptive, and rely on efficient approximate-nearest-neighbor queries. As the CSP information is only a function of the non-radical species in the system and has relatively small gradients in the chemical state space, tabulation occurs in a lower-dimensional state space and at a relatively coarse level, thereby improving scalability to larger chemical mechanisms. The approach is demonstrated on the simulation of homogeneous constant pressure H2–air and CH4–air ignition, over a range of initial conditions. For CH4–air, results are shown that outperform direct implicit integration of the stiff chemical kinetics while maintaining good accuracy. 相似文献
12.
L.A. Wahab M.B. El-Den A.A. Farrag S.A. Fayek K.H. Marzouk 《Journal of Physics and Chemistry of Solids》2009,70(3-4):604-608
Optical and electrical properties of Zn- and Cd-modified Cu2SnSe4 amorphous films have been studied. The results show that Zn and Cd incorporation decreases the thermal activation energy, the pre-exponential factor and the optical gap. Variation in the refractive index and extinction coefficient with the wavelength has been also reported. The relations between the optical gap and the chemical composition in the investigated films have been discussed in terms of the average heat of atomization. The effect of γ-radiation up to 71.25 Mrad dose on the optical gap was also studied. 相似文献
13.
Ahmed A. Al-Karmalawy Mai M. Farid Ahmed Mostafa Alia Y. Ragheb Sara H. Mahmoud Mahmoud Shehata Noura M. Abo Shama Mohamed GabAllah Gomaa Mostafa-Hedeab Mona M. Marzouk 《Molecules (Basel, Switzerland)》2021,26(21)
Flavonoids are important secondary plant metabolites that have been studied for a long time for their therapeutic potential in inflammatory diseases because of their cytokine-modulatory effects. Five flavonoid aglycones were isolated and identified from the hydrolyzed aqueous methanol extracts of Anastatica hierochuntica L., Citrus reticulata Blanco, and Kickxia aegyptiaca (L.) Nabelek. They were identified as taxifolin (1), pectolinarigenin (2), tangeretin (3), gardenin B (4), and hispidulin (5). These structures were elucidated based on chromatographic and spectral analysis. In this study, molecular docking studies were carried out for the isolated and identified compounds against SARS-CoV-2 main protease (Mpro) compared to the co-crystallized inhibitor of SARS-CoV-2 Mpro (α-ketoamide inhibitor (KI), IC50 = 66.72 µg/mL) as a reference standard. Moreover, in vitro screening against SARS-CoV-2 was evaluated. Compounds 2 and 3 showed the highest virus inhibition with IC50 12.4 and 2.5 µg/mL, respectively. Our findings recommend further advanced in vitro and in vivo studies of the examined isolated flavonoids, especially pectolinarigenin (2), tangeretin (3), and gardenin B (4), either alone or in combination with each other to identify a promising lead to target SARS-CoV-2 effectively. This is the first report of the activity of these compounds against SARS-CoV-2. 相似文献
14.
Mamdouh R. Rezk Ahmed S. Fayed Hoda M. Marzouk Samah S. Abbas 《Journal of Solid State Electrochemistry》2018,22(11):3351-3361
Introduction of potentiometric ion-selective electrodes (ISEs) opened a new bright area in pharmaceutical analysis acknowledged as being an eco-friendly, simple, and energy-saving technique that is well-suited with microfabrication. In this contribution, potentiometric ISEs were employed as an alternative green analytical tool with the crucial goal of expanding the effective application of the potentiometric sensors in different disciplines of drug-stability studies and quality-control investigations. Four novel cyclopentolate hydrochloride and phenylephrine hydrochloride selective membrane sensors were constructed and evaluated. Sensors’ fabrication was achieved using potassium tetrakis (4-chlorophenyl) borate, a cationic exchanger, in a polyvinyl chloride polymeric matrix plasticized with 2-nitrophenyl octyl ether and using 2-hydroxy propyl-β-cyclodextrin as an ionophore. A comparative potentiometric study was implemented using two designs of ISEs; a conventional liquid inner contact and a glassy carbon solid-contact one. Using solid-contact ISEs, detection limit was substantially decreased and the discriminative ability in the presence of the most interfering substances was enhanced. This permits simultaneous estimation of both drugs, in spite of their similar ionic characteristics, abolishing the need for any pretreatment or separation steps in their challenging combined ophthalmic formulation as well as in rabbit aqueous humor and in the presence of their degradation products. 相似文献
15.
Sayed A.M. Marzouk Mohamed H. Al-Marzouqi Samira M.S.M. Baomran 《Microchemical Journal》2010,95(2):207-212
The construction, optimization and use of simple and inexpensive gas analyzer for real time measurement of sulfur dioxide in gas streams are described. The analyzer consisted of three main components (i) a custom fabricated hollow fiber membrane (HFM) gas contactor, (ii) carrier solution which absorbs SO2 molecules from the gas stream in the HFM gas contactor and (iii) a flow-through detector placed downstream which continuously measures the changes occurred to the carrier solution upon absorption of SO2 molecules. The significant acidic properties of the produced sulfurous acid suggested pH and conductivity detectors to monitor the decrease in pH or the increase in the conductivity which constituted the basis for quantification of SO2 in the gas line. Aqueous potassium oxalate (10? 1 mol/L) and hydrogen peroxide (10? 3 mol/L) were used as carrier solutions in combination with pH and conductivity detectors, respectively. The analyzer equipped with pH detector provided linear potentiometric response to SO2 concentration up to 1000 ppm with Nernstian slop of 61 mV/log[SO2]. Excellent SO2 recoveries (97–108%) were obtained in the presence of several folds of potentially interfering acidic gases, i.e., CO2 and H2S. The conductivity detector provided linear response up to 2500 ppm. Under optimized conditions, both detectors offered several favorable performance characteristics such as (i) fast response and recovery times, (ii) excellent signal stability and reproducibility (RSD = 0.5%), (iii) intrinsic high selectivity to most common neutral gases, e.g., CH4, N2, O2, CO, etc. The suggested analyzer was applied successfully in monitoring the removal of SO2 from SO2–N2 gas mixtures with hollow fiber membrane contactor using distilled water or aqueous sodium hydroxide as stripping solvents. 相似文献
16.
The essential oils obtained from leaves of two Myrtus communis varieties (baetica and italica), growing wild in North Tunisia, were investigated by GC and GC–MS at their different phenological stages. The highest essential oil yield was observed at the flowering stage with 0.6% (w/w) for italica and 0.4% (w/w) for baetica and 49 compounds were identified. The main essential oil leaf compounds of both myrtle varieties, belonging to the monoterpene class, were α-pinene, 1,8-cineole, limonene and linalool and their percentages showed significant changes during the phenological stages.
相似文献17.
Ali Fouad Adel A. Marzouk Montaser Sh. A. Shaykoon Samy M. Ibrahim Sobhy M. El-Adl Ashraf Ghanem 《Molecules (Basel, Switzerland)》2021,26(12)
Daptomycin, a macrocyclic antibiotic, is here used as a new chiral selector in preparation of chiral stationary phase (CSP) in a recently prepared polymer monolithic capillary. The latter is prepared using the copolymerization of the monomers glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) in the presence of daptomycin in water. Under reversed phase conditions (RP), the prepared capillaries were tested for the enantioselective nanoliquid chromatographic separation of fifty of the racemic drugs of different pharmacological groups, such as adrenergic blockers, H1-blockers, NSAIDs, antifungal drugs, and others. Baseline separation was attained for many drugs under RP-HPLC. Daptomycin expands the horizon of chiral selectors in HPLC. 相似文献
18.
Nancy Abdelgawad Mahmoud F. Ismail Mohamed H. Hekal Magda I. Marzouk 《Journal of heterocyclic chemistry》2019,56(6):1771-1779
1,3‐Diphenylpyrazole‐4‐carboxylaldehyde and o‐hydroxyacetophenone were exploited as starting materials for the synthesis of novel substituted chalconated pyrazole derivative. The proclivity of this compound towards carbon and nitrogen nucleophiles such as malononitrile, diethyl malonate, ethyl cyanoacetate, ethyl acetoacetate, semicarbazide, thiosemicarbazide, and hydroxylamine has been investigated. The structures of all synthesized compounds were ascertained by analytical and spectral data. The antitumor activity of the target synthesized compounds was tested against a panel of two human tumor cell lines, namely, hepatocellular carcinoma (liver) HepG2 and mammary gland breast MCF‐7. 相似文献
19.
Ultraviolet and visible absorption spectra of prepared undoped lithium phosphate glass and samples of the same nominal composition with additional Bi2O3 contents were measured before and after being subjected to gamma doses of 3 and 6 Mrad. The base undoped lithium phosphate glass exhibits strong charge transfer ultraviolet absorption bands, which are related to unavoidable presence of trace iron impurities within the raw materials for the preparation of this glass. Bi2O3-containing glasses show the extension of UV absorption beside the resolution of visible bands at 400, 450, and 700 nm with the increase of Bi2O3 content due the sharing of absorption of Bi3+ ions. Gamma irradiation of the base glass reveals extended induced bands; the UV bands are related to the conversion of some Fe2+ to Fe3+ through photochemical reactions during the irradiation process. The visible induced bands are related to the formation of positive hole centers from the host phosphate glass. Glasses containing Bi2O3 are observed to show some shielding behavior, which is attributed to the presence of heavy weight and large atomic number of Bi3+ ions. Infrared absorption spectral measurements of the base lithium phosphate glass show characteristic vibrational modes which are related to specific phosphate groups. The addition of Bi2O3 in measurable percent produces additional vibrational bands due to the introduction of Bi–O groups such as BiO3 and BiO6. 相似文献
20.
M. A. I. Salem H. M. F. Madkour M. I. Marzouk M. E. Azab N. F. H. Mahmoud 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2596-2614
The pyrimidinethiones have wide biological and pharmaceutical activities, that have attracted considerable interest in recent years especially as antiviral inhibiting production of hepatitis B virus (HBV), and in vitro insulin-mimetic. Activity of the complexes of pyrimidinone derivatives evaluated from 50% inhibitory concentration promoted us to study the transformation of the 2-thioxopyrimidin-6(1H) ones to fused bi- and tri-cyclic heterocyclic compounds having the pyrimidine moieties and screening their biological activity. The reactivity of 2-mercapto-4-aryl-5-cyanopyrimidin-6(1H)ones (1) towards alkylation by different mono and bifunctional halo-organic compounds has been investigated to give S-monoalkylated products 2, 7 and 9; S- and N-dialkylated products 3, 13 and 14. Treatment of 1 and/or 2 with hydrazine hydrate as a nitrogen nucleophile have been investigated to give 4, treatment of 4 with CS2 and sodium nitrite in the presence of acetic acid (0°C) produced 1,2,4-triazolopyrimidin-5(1H)one derivatives (5)and tetrazolo[1,5-a]pyrimidin-5(1H)ones (6), respectively. Also cyclization of 7 and 9 gave [1,3]thiazolo[3,2-a]pyrimidin-5(1H)one and [1,3]thiazolo[3,2-a]pyrimidin-3,5-dione derivatives 8 and 10 respectively, treatment of 10 with aromatic aldehyde produces 11 which reacted with guanidine HCl to give pyrimido[4,5-d]thiazolo[3,2-a]pyrimidin-6(1H)one derivative 12. Reaction of 14 with o-phenylenediamine was investigated and gave [1,4]quinoxalino[2,3-b][1,3]thiazolo[3,2-a]pyrimidin-9(1H)one derivative 15. 相似文献