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排序方式: 共有392条查询结果,搜索用时 31 毫秒
81.
John Ojur Dennis Mohammed Khalil Mohammed Ali Khalid Hassan Ibnaouf Osama Aldaghri Naglaa F. M. Abdel All Abdullahi Abbas Adam Fahad Usman Yarima Mudassir Hassan Bashir Abubakar Abdulkadir 《Molecules (Basel, Switzerland)》2022,27(17)
In this study, a solution casting method was used to prepare solid polymer electrolytes (SPEs) based on a polymer blend comprising polyvinyl alcohol (PVA), cellulose acetate (CA), and potassium carbonate (K2CO3) as a conducting salt, and zinc oxide nanoparticles (ZnO-NPs) as a nanofiller. The prepared electrolytes were physicochemically and electrochemically characterized, and their semi-crystalline nature was established using XRD and FESEM. The addition of ZnO to the polymer–salt combination resulted in a substantial increase in ionic conductivity, which was investigated using impedance analysis. The size of the semicircles in the Cole–Cole plots shrank as the amount of nanofiller increased, showing a decrease in bulk resistance that might be ascribed to an increase in ions due to the strong action of the ZnO-NPs. The sample with 10 wt % ZnO-NPs was found to produce the highest ionic conductivity, potential window, and lowest activation energy (Ea) of 3.70 × 10–3 Scm–1, 3.24 V, and 6.08 × 10–4 eV, respectively. The temperature–frequency dependence of conductivity was found to approximately follow the Arrhenius model, which established that the electrolytes in this study are thermally activated. Hence, it can be concluded that, based on the improved conductivity observed, SPEs based on a PVA-CA-K2CO3/ZnO-NPs composite could be applicable in all-solid-state energy storage devices. 相似文献
82.
Necessary and sufficient conditions for oscillation of second‐order dynamic equations on time scales
Yong Zhou Bashir Ahmad Ahmed Alsaedi 《Mathematical Methods in the Applied Sciences》2019,42(13):4488-4497
In this paper, we establish necessary and sufficient conditions for oscillation of second‐order strongly superlinear and strongly sublinear dynamic equations. Our results unify and improve many known results in the literature. 相似文献
83.
A sensitive and selective spectrophotometric method for the determination of acetone in acetic acid has been worked out. It is based on the reaction of acetone with diazotized p-aminobenzoic acid in a strongly alkaline medium to form a purple color with maximum absorption at 540 nm. Beer's law holds up in the range 20–140 μg of acetone in a final volume of 20 ml, with a molar absorptivity of 8.1 × 103 liters mol?1 cm?1, sensitivity index of 0.0072 μg cm?2, relative error of ?1.9 to +0.6%, and relative standard deviation of 0.7–3.5, depending on the concentration level. Furthermore, the color reaction is fast, and the procedure is simple, and avoids the use of an extraction. 相似文献
84.
Dihydroxybenzoic acid was modified to three analogues (M2, M4 and M6). The analogues exhibited specific properties that resulted in enhancement of analyte signal intensity with or without addition of iodine compared to the underivatized parent. Addition of iodine to M2, an ester of dihydroxybenzoic acid that had a terminal double bond in the alkyl chain, resulted in peak intensities comparable to the parent, indicating that iodine interaction across the double bond resulted in enhancement although the exact mechanism is not fully understood. No enhancement on addition of iodine was observed for M4, which had a long alkyl chain that contained no double bonds. The alkyl chain allowed micelle formation in solution, which in turn allowed more uniform analyte-to-matrix mixing. The final analogue combined the long alkyl chain of M4 with the double bond of M2 and exhibited either similar peak intensities to that of dihydroxybenzoic acid or better. Micelle formation in solution was examined using spectroscopy and in the solid by reflective microscopy. The standard deviation from spot to spot was considerably lower relative to dihydroxybenzoic acid (RSD 3.4%vs. 14.2%). Unlike dihydroxybenzoic acid, the novel matrix M6 was able to yield characteristic peaks for analytes such as ubiquitin. 相似文献
85.
Zahid Hassan Hidayat Hussain Viqar Uddin Ahmad Shazia Anjum Gennaro Pescitelli Tibor Kurtn Karsten Krohn 《Tetrahedron: Asymmetry》2007,18(24):2905-2909
The absolute configuration of 1β,10β-epoxydesacetoxymatricarin 1, a sesquiterpenoid isolated from Carthamus oxycantha, was established by TDDFT CD calculations in combination with single crystal X-ray analysis. Since the solid-state CD spectrum shows contributions from intermolecular interactions in the crystal, 1 represents a test case for our solid-state CD/TDDFT approach. 相似文献
86.
Cellulose acetate was characterized by using enzyme in both digestion and chemical derivation and acetolysis. The fragments were normalised and compared on an anhydroglucose scale, using mass spectrometry to identify the different sized fragments. It was determined that at least two sub-populations for cellulose acetate existed within the parent. The macroscopic effect of this variation in the degree of acetylation will be a modification of the structural properties of the polymer chains. It was found that through comparison with enzyme-based degradation, an estimation of the acetylation topography of the cellulose acetate fraction could be made. Enzyme degradation produced a number of oligosaccharides of more than 10 glucose units, presumably resistant to enzyme degradation because they contained acetate groups. Chemical hydrolysis gave a random ladder of short sequences of mainly 3–4 glucose units some of which had a high methyl ether content, that were analysed by mass and converted to an anhydroglucose mass scale. This approach could be used to demonstrate differences between large biopolymers of cellulose acetate that previously gave an overall average rather than a specific ladder average. 相似文献
87.
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89.
Hydralazine hydrochloride itself is a reducing agent and its redox properties like other reducing agents vary as the oxidizing agent and applied conditions vary. The redox properties of hydralazine were studied by spectrophotometric method. Formal redox potential of hydralazine was calculated and effect of pH was observed on redox properties of hydralazine. 相似文献
90.