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排序方式: 共有381条查询结果,搜索用时 171 毫秒
141.
Nonlinear Dynamics - In this paper, two efficient cryptosystem schemes in the form of permutation–substitution based on chaotic systems are proposed. Firstly, a simple and efficient S-box... 相似文献
142.
Dr. Muhammad Usman Khan Dr. Muhammad Imran. Dr. Muhammad Fayyaz ur Rehman Dr. Mohammed A. Assiri Dr. Syed Muddassir Ali Mashhadi Dr. Muhammad Safwan Akram Dr. Changrui Lu 《ChemistryOpen》2022,11(8)
Porphyrin‐based non‐fullerene acceptors (NFAs) have shown pronounced potential for assembling low‐bandgap materials with near‐infrared (NIR) characteristics. Herein, panchromatic‐type porphyrin‐based molecules (POR1–POR5) are proposed by modulating end‐capped acceptors of a highly efficient porphyrin‐based NFA PORTFIC(POR) for organic solar cells (OSCs). Quantum chemical structure‐property relationship has been studied to discover photovoltaic and optoelectronic characteristics of POR1–POR5. Results show that optoelectronic properties of the POR1–POR5 are better in all aspects when compared with the reference POR. All proposed NFAs particularly POR5 proved to be the preferable porphyrin‐based NIR sensitive NFA for OSCs applications owing to lower energy gap (1.56 eV), transition energy (1.11 eV), binding energy (Eb =0.986 eV), electron mobility (λe=0.007013Eh ), hole mobility (λh =0.004686 Eh), high λmax =1116.27 nm and open‐circuit voltage (Voc =1.96 V) values in contrast to the reference POR and other proposed NFAs. This quantum chemical insight provides sufficient evidence about excellent potential of the proposed porphyrin‐based NIR sensitive NFA derivatives for their use in OSCs. 相似文献
143.
Geir Bjrklund Amin Gasmi Larysa Lenchyk Mariia Shanaida Saba Zafar Pavan Kumar Mujawdiya Roman Lysiuk Halyna Antonyak Sadaf Noor Muhammad Akram Kateryna Smetanina Salva Piscopo Taras Upyr Massimiliano Peana 《Molecules (Basel, Switzerland)》2022,27(21)
The current review provides an up-to-date analysis of scientific data on astaxanthin (ASX) sources and experimental studies on its health benefits as a potent antioxidant in the aging process. ASX is a liposoluble carotenoid nutrient and reddish-orange pigment, naturally synthesized by numerous microalgae, yeasts, and bacteria as secondary metabolites. Provides a reddish hue to redfish and shellfish flesh that feed on ASX-producing microorganisms. The microalga Haematococcus pluvialis is the most important source for its industrial bioproduction. Due to its strong antioxidant properties, numerous investigations reported that natural ASX is a more significant antioxidant agent than other antioxidants, such as vitamin C, vitamin E, and β-carotene. Furthermore, several data show that ASX possesses important nutraceutical applications and health benefits, especially in healthy aging processes. However, further studies are needed for a deeper understanding of the potential mechanisms through which ASX could lead to its effective role in the healthy aging process, such as supporting brain health and skin homeostasis. This review highlights the current investigations on the effective role of ASX in oxidative stress, aging mechanisms, skin physiology, and central nervous system functioning, and shows the potential clinical implications related to its consumption. 相似文献
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Akram Al-Droubi Michael Renardy 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1988,39(6):931-936
We consider a two-dimensional problem arising from the interaction of electromagnetic waves traveling in air with a metallic body. This problem leads to a parabolic equation inside the body and a hyperbolic equation outside; the two equations interact through jump relations across the boundary of the body. We prove the existence of solutions using energy estimates in conjunction with a Galerkin argument. We also remark on how to obtain similar results in the three-dimensional case.
Zusammenfassung Wir betrachten ein zweidimensionales Problem, welches bei der Wechselwirkung einer sich in Luft ausbreitenden elektromagnetischen Welle mit einem metallischen Objekt auftritt. Dieses Problem führt auf eine parabolische Gleichung innerhalb des Objekts und eine hyperbolische Gleichung außerhalb; die beiden Gleichungen sind durch Sprungbedingungen an der Grenzfläche gekoppelt. Wir zeigen die Existenz von Lösungen mittels Energieabschätzungen in Verbindung mit einem Galerkin-Argument. Es wird auch angedeutet, wie man ähnliche Resultate im dreidimensionalen Falle erhält.相似文献
148.
Kevin G. Siver Kenneth B. Sloan Robert P. Waranis Akram Saab 《Journal of heterocyclic chemistry》1988,25(4):1077-1081
Labile aminomethyl and hydroxymethyl derivatives of 6-mercaptopurine (I) (6-MP) and S6-acyloxymethyl-6-MP have been converted to stable acetyloxymethyl derivatives by their reaction with acetic anhydride. Analysis of the reaction products and comparison of their 'H nmr spectra and hplc chromatograms with those of acetyloxymethyl derivatives of known structures suggested 1) that the aminomethyl derivatives of 6-MP were 7-substituted derivatives, 2) that the aminomethyl derivative of S6-acetyloxylmethyl-6-MP was a 9-derivative, 3) that the hydroxymethyl derivative of 6-MP was a mixture of 7-substituted and S6,3-disubstitu-ted derivatives, and 4) that the hydroxymethyl derivative of S6-pivaloyloxymethyl-6-MP was a 9-substituted derivative. In addition, a previously unreported dialkyl derivative of 6-MP VI was isolated from its reaction with aminomethylating agent and characterized. Analyses of the 'H nmr spectra and hplc chromatograms of the reaction of VI with acetic anhydride suggested that VI was a 1,7-disubstituted derivative. 相似文献
149.
The complex formed between palladium(II) and tin(II) in hydrochloric acid solutions, and its extractability by tri-n-octylamine were investigated. Two different species were obtained: one a brown-red complex and the other yellow. Both were extracted into tri-n-octylamine in benzene, but the yellow species which had a definite absorption maximum at 410 mμ was more suitable for the determination of palladium. A method is described for the spectrophotometric determination of palladium in the presence of many other elements. Both species are considered to be anionic and a mechanism for their extraction is proposed. 相似文献
150.
Enhanced Viscosity of Poly(acrylamide) Solution in the Presence of Chromium Citrate Triggered by Release of CO2
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Ai-guo Mo Yu-pu Wang Yi-kun Liu Wan-fu Zhou Quan Zhou Akram Yasin Hai-yang Yang 《化学物理学报(中文版)》2018,31(1):117-122
Partially hydrolyzed polyacrylamide (HPAM) has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3+ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3+ so that the crosslinking between HPAM and Cr3+ can be prevented completely. Due to the decomposition of the bicarbonate (HCO3-) embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3+ increased accordingly. When the complexation of Cr3+ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased significantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate (KH2PO4), the release of CO2 was very slow and the condition was highly controlled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3+ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery. 相似文献