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排序方式: 共有218条查询结果,搜索用时 15 毫秒
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Xia X Naumann d'Alnoncourt R Strunk J Litvinov S Muhler M 《The journal of physical chemistry. B》2006,110(16):8409-8415
A reliable method for adsorption systems in equilibrium is established to derive coverage-dependent kinetics and thermodynamics from the volumetric data obtained during the static microcalorimetric measurement of heats of adsorption. The Wigner-Polanyi equation is applied to analyze the pressure change as a function of time during stepwise dosing of the adsorptive until thermodynamic adsorption-desorption equilibrium is established. For carbon monoxide adsorption on a hydrogen-reduced Cu/ZnO/Al2O3 catalyst, the adsorption rate constant (ka) is found to be in the range from 10(-6) to 10(-4) Pa(-1) s(-1), and the desorption rate constant (kd) from 10(-4) to 10(-2) s(-1), both increasing with fractional coverage theta. The kinetically derived equilibrium constant Ktheta is in good agreement with Ktheta obtained from the adsorption isotherm. RT ln(Kp0) and the differential heat of adsorption (qdiff) were found to decrease in parallel, reflecting a normal Temkin-type heterogeneity. 相似文献
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Raoul Walther Anna K. Winther Anne Sofie Fruergaard Wouter vandenAkker Lise Srensen Signe Maria Nielsen Morten T. JarlstadOlesen Yitao Dai Henrik S. Jeppesen Paolo Lamagni Aleksandr Savateev Sren Lykke Pedersen Camilla Kaas Frich Ccile Vigier‐Carrire Nina Lock Mandeep Singh Vipul Bansal Rikke L. Meyer Alexander N. Zelikin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):284-288
Nanozymes, nanoparticles that mimic the natural activity of enzymes, are intriguing academically and are important in the context of the Origin of Life. However, current nanozymes offer mimicry of a narrow range of mammalian enzymes, near‐exclusively performing redox reactions. We present an unexpected discovery of non‐proteinaceous enzymes based on metals, metal oxides, 1D/2D‐materials, and non‐metallic nanomaterials. The specific novelty of these findings lies in the identification of nanozymes with apparent mimicry of diverse mammalian enzymes, including unique pan‐glycosidases. Further novelty lies in the identification of the substrate scope for the lead candidates, specifically in the context of bioconversion of glucuronides, that is, human metabolites and privileged prodrugs in the field of enzyme‐prodrug therapies. Lastly, nanozymes are employed for conversion of glucuronide prodrugs into marketed anti‐inflammatory and antibacterial agents, as well as “nanozyme prodrug therapy” to mediate antibacterial measures. 相似文献
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The Schramm-Loewner evolution (SLE) is a powerful tool to describe fractal interfaces in 2D critical statistical systems, yet the application of SLE is well established for statistical systems described by quantum field theories satisfying only conformal invariance, the so-called minimal conformal field theories (CFTs). We consider interfaces in Z(N) spin models at their self-dual critical point for N = 4 and N = 5. These lattice models are described in the continuum limit by nonminimal CFTs where the role of a ZN symmetry, in addition to the conformal one, should be taken into account. We provide numerical results on the fractal dimension of the interfaces which are SLE candidates for nonminimal CFTs. Our results are in excellent agreement with some recent theoretical predictions. 相似文献
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Portet B Fabre N Rozenberg R Habib-Jiwan JL Moulis C Quetin-Leclercq J 《Journal of chromatography. A》2008,1210(1):45-54
The fragmentations of hydroxylated flavanones, chalcones and dihydrochalcones were investigated by direct loop injection using an ion trap mass spectrometry equipped with atmospheric pressure chemical ionization (APCI) probe. Some of them have been isolated from the leaves of Piper hostmannianum var. berbicense and standards were used to confirm their fragmentation behaviour. In negative ion mode, fragmentations of these three types of flavonoids revealed specific diagnostic ions which allowed us to identify aglycones in a crude plant extract. The major fragment ion obtained in MS/MS experiment for methoxylated chalcones is the neutral loss of a methyl radical whereas a H(2)O molecule is lost in the case of methoxylated dihydrochalcones. Methoxylated chalcones and flavanones isomers could be differentiated by the relative intensity ratio of [M-H-CH(3)]*(-) and [M-H-C(2)H(2)O](-) ions. Based on UV and MS data, a decision tree that includes UV lambda(max) absorptions and MS/MS diagnostic ions was built in order to obtain structural information of unknown compounds present in the extract. This tree was used to identify flavonoids in the ethyl acetate extract of P. hostmannianum var. berbicense leaves after analysis by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization ion trap multistage mass spectrometry. A total of 11 flavonoids were tentatively characterized based on the MS fragmentations pattern observed in MS(n) experiments. 相似文献
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