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排序方式: 共有118条查询结果,搜索用时 187 毫秒
41.
S. Waleed Noor 《Archiv der Mathematik》2017,109(5):455-460
In this note, we consider the question of when a Toeplitz operator on the Hardy–Hilbert space \(H^2\) of the open unit disk \(\mathbb {D}\) is complex symmetric, focusing on symbols \(\phi :\mathbb {T}\rightarrow \mathbb {C}\) that are continuous on the unit circle \(\mathbb {T}=\partial \mathbb {D}\). A closed curve \(\phi \) is called nowhere winding if the winding number of \(\phi \) is 0 about every point not in the range of \(\phi \). It is then shown that if \(T_\phi \) is complex symmetric, then \(\phi \) must be nowhere winding. Hence if \(\phi \) is a simple closed curve, then \(T_\phi \) cannot be a complex symmetric operator. The spectrum and invertibility of complex symmetric Toeplitz operators with continuous symbols are then described. Finally, given any continuous curve \(\gamma :[a,b]\rightarrow \mathbb {C}\), it is shown that there exists a complex symmetric Toeplitz operator with continuous symbol whose spectrum is precisely the range of \(\gamma \). 相似文献
42.
Waleed A. Hassanain Maha A. Hegazy Laila E. Abdel Fattah Hamed M. El-Fatatry 《液相色谱法及相关技术杂志》2017,40(17):872-878
Degradation of active ingredients is common during the production, transportation, and storage of the pharmaceutical preparations. The resulted degradation products can affect the pharmaceuticals’ therapeutic effect. Also, they may have some toxic properties that make them have deleterious effects on patients. Nifuroxazide, antitumor, antimetastasis, and antidiarrheal agent, has been detected in pharmaceutical formulation by two sensitive, selective, and cheap methods. The first method was densitometric thin-layer chromatography technique. The compound was detected in the presence of its degradation products without any interference. Limits of quantification and detection values were 200 and 94.3?ng/band, respectively. The method was linear in the range 0.2–12?µg/band with mean recovery% ±relative standard deviation (RSD)%?=?99.97%?±?1.414. The second method was developed using simple high-performance liquid chromatography technique. The method was successfully able to separate the proposed compound from its degradation forms in the presence of pentoxiftylline as an internal standard without any interference in less than 5?min. The method also detected nifuroxazide degradation products down to 500?ng/mL. Both methods were statistically compared to a reported method with no significant difference in performance. 相似文献
43.
The development of economic and environmentally friendly extractants to recover cobalt metal is required due to the increasing demand for this metal.In this study,solvent extraction of Co(Ⅱ) from aqueous solution using a mixture of N,N’-carbonyl difatty amides(CDFAs) synthesised from palm oil as the extractant was carried out.The effects of various parameters such as acid,contact time,extractant concentration,metal ion concentration and stripping agent and the separation of Co(Ⅱ) from other metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ) were investigated.It was found that the extraction of Co(Ⅱ) into the organic phase involved the formation of 1:1 complexes.Co(Ⅱ) was successfully separated from commonly associated metal ions such as Fe(Ⅱ),Ni(Ⅱ),Zn(Ⅲ) and Cd(Ⅱ).Co(Ⅱ) stripping from the loaded organic phase was studied in aqueous solution.These results are useful to recover Co(Ⅱ) from aqueous solution utilising(CDFAs) as an extractant. 相似文献
44.
Waleed E. Mahmoud 《先进技术聚合物》2011,22(12):2550-2555
Polyvinyl alcohol (PVA) with different molecular weights (8000, 14,000, and 132,000 g/mol) capped lead selenide (PbSe) quantum dots (QDs) are prepared. The nanocomposites are characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM studies show that the particle size of PbSe QDs decrease with the increase in PVA molecular weight and/or PVA amount. This may be due to the increase in molecular weight inhibiting further growth of PbSe into the polymer matrix. Thermogravimetric analysis showed that the introduction of PbSe QDs into PVA decreases the crystallinity of the polymer. The optical absorption spectroscopy of prepared nanocomposites showed that the absorption peaks are strongly shifted to the lower wavelength (blue shift) from near infrared region to visible region by increasing the PVA molecular weight. The (I–V) characteristic curves of the PVA/PbSe nanocomposite films under illumination showed a photovoltaic cell‐like behavior. The results indicated that as the molecular weight of polymer increases, the conversion efficiency increases. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
45.
Waleed E. Mahmoud A.A. Al-Ghamdi Mohammad W. Kadi 《Radiation Physics and Chemistry》2012,81(6):693-696
This contribution represents the manufacturing of a hybrid organic–inorganic proton conducting compound, which involves the introduction of heteropoly acid (HPA) of different concentrations into poly-vinyl alcohol (PVA). These compounds were irradiated by γ-rays at different doses of 10, 20, 30, and 40 kGy. The unirradiated and irradiated compounds were characterized by XRD and DSC. The XRD results showed that the crystallinity and d-spacing were strongly influenced by the amount of HPA and irradiation doses. The DSC results showed that the melting point was decreased as a result of HPA concentration and irradiation doses. The degree of crystallinity calculated from XRD is in good agreement with that calculated from DSC. The activation energy of the Unirradiated and irradiated compounds was calculated using the Flynn–Wall–Ozawa model. 相似文献
46.
47.
Waleed E. Mahmoud 《Journal of Crystal Growth》2010,312(21):3075-3079
Single crystalline Ce-doped ZnO hexagonal nanoplatelets are successfully synthesized. Zinc acetate, cerium nitrate, potassium hydroxide and poly vinyl alcohol were mixed together and transferred to a 100 mL Teflon-lined stainless steel autoclave kept at 150 °C for 24 h. The obtained precipitant is calcined at 600 °C. The morphology and microstructure were determined by field emission scanning electron microscopy (FE-SEM), X-ray diffraction transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. The investigation confirmed that the products were of the wurtzite structure of ZnO. The doped hexagonal nanoplatelets have edge length 25 nm and thickness 11 nm. EDX result showed that the amount of Ce in the product is about 15%. Photoluminescence of these doped hexagonal nanoplatelets exhibits a blue shift and weak ultraviolet (UV) emission peak, compared with pure ZnO, which may be induced by Ce-doping. The growth mechanism of the doped hexagonal nanoplatelets was also discussed. 相似文献
48.
Chunmin Yang Afsar Alam Fahad A. Alhumaydhi Mohd Shahnawaz Khan Suliman A. Alsagaby Waleed Al Abdulmonem Md. Imtaiyaz Hassan Anas Shamsi Bilqees Bano Dharmendra Kumar Yadav 《Molecules (Basel, Switzerland)》2022,27(10)
Tyrosine-protein kinase Yes (YES1) belongs to the Tyrosine-protein kinase family and is involved in several biological activities, including cell survival, cell–cell adhesion, cell differentiation, and cytoskeleton remodeling. It is highly expressed in esophageal, lung, and bladder cancers, and thus considered as an attractive drug target for cancer therapy. In this study, we performed a virtual screening of phytoconstituents from the IMPPAT database to identify potential inhibitors of YES1. Initially, the molecules were retrieved on their physicochemical properties following the Lipinski rule of five. Then binding affinities calculation, PAINS filter, ADMET, and PASS analyses followed by an interaction analysis to select safe and clinically better hits. Finally, two compounds, Glabrene and Lupinisoflavone C (LIC), with appreciable affinities and a specific interaction towards the AlphaFold predicted structure of YES1, were identified. Their time-evolution analyses were carried out using an all-atom molecular dynamics (MD) simulation, principal component analysis, and free energy landscapes. Altogether, we propose that Glabrene and LIC can be further explored in clinical settings to develop anticancer therapeutics targeting YES1 kinase. 相似文献
49.
50.
A simple and reliable high-performance liquid chromatographic method with UV detection at 245 nm has been developed and validated
for determination of tranexamic acid (TA) in a dosage form and in human urine. Before injection samples were derivatized with
phenyl isothiocyanate (PITC). The reaction temperature, reaction time, and concentration of PITC used for derivatization were
optimized. Chromatographic separation was on a C18 column with a 65:35 (v/v) mixture of 10 mM phosphate buffer, pH 3.6, and acetonitrile as mobile phase. Heptaminol hydrochloride was used as internal
standard. 相似文献