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41.
An analytical energy gradient formula for the density-matrix-based linear-scaling divide-and-conquer (DC) self-consistent field (SCF) method was proposed in a previous paper by Yang and Lee (YL) [J. Chem. Phys. 103, 5674 (1995)]. Since the formula by YL does not correspond to the exact gradient of the DC-SCF energy, we derive the exact formula by direct differentiation, which requires solving the coupled-perturbed equations while including the inter-subsystem coupling terms. Next, we present an alternative formula for approximately evaluating the DC-SCF energy gradient, assuming the variational condition for the subsystem density matrices. Numerical assessments confirmed that the DC-SCF energy gradient values obtained by the present formula are in reasonable agreement with the conventional SCF values when adopting a reliable buffer region. Furthermore, the performance of the present method was found to be better than that of the YL method. 相似文献
42.
Jyunichi Koyanagi Katsumi Yamamoto Kouji Nakayama Akira Tanaka 《Journal of heterocyclic chemistry》1994,31(5):1303-1304
Phthalic anhydride in THF was added to 3-lithiofuran 2 in THF to give 3,3-di-(3-furyl)-1,3-dihy-droisobenzofuran-1-one 4 . On the other hand, 2 in THF was added to phthalic anhydride in THF to give 2-(3-furanoyl)benzoic acid 3 by the inverse addition method. Further, the parent naphtho[2,3-b]furan-4,9-dione 1 was obtained from the reaction of 3 with two equimolar amounts of LDA. 相似文献
43.
The statistical error of liquid level controlled by radiaiton relay is analysed and a method of minimizing the error is proposed in this paper. This method comes to the problem of optimum setting of the time constant of radiation relay. The equations for obtaining the value of time constant are presented and the numerical results are shown in a table and plotted in a figure. The optimum time constant of the upper level control relay differs entirely from that of lower level control relay. 相似文献
44.
Whitmania pigra is common in China and has been used as a traditional Chinese anticoagulant medicine for years, but its effective components are unknown to scientists. In this article we report a rapid method for isolation and purification of an anticoagulant from W. pigra for the first time. An acetone-water extract of W. pigra was subjected to anion-exchange chromatography on a Sephadex DEAE A-50 column, and gel permeation chromatography on Sephadex G-25 and Sephadex LH-20 columns successively, which afforded a fraction with potent anticoagulant activity. An anticoagulant was isolated and purified from this fraction by reversed-phase high-performance liquid chromatography (RP-HPLC). It was identified as a single pure substance by RP-HPLC and sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). This component was named whitmanin and its molecular weight was determined as 8608 Da by matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF-MS). 相似文献
45.
New Insights into the Nature of Co‐components and Their Impact on Pd Structure: X‐ray Absorption Studies on Toluene Acetoxylation Catalysts
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Dr. Suresh Gatla Dr. Jörg Radnik Dr. Neetika Madaan Dr. Marga‐Martina Pohl Dr. Olivier Mathon Dr. Andrei Rogalev Dr. Venkata Narayana Kalevaru Dr. Andreas Martin Dr. Sakura Pascarelli Prof. Dr. Angelika Brückner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15280-15289
Co‐components are a powerful tool to tune the performance of catalysts, but their nature and their impact on the catalysts is often controversially discussed. In this study X‐ray absorption spectroscopy (XAS) was employed to elucidate the nature of co‐components and their impact on the catalytic reaction. In anatase‐supported Pd‐based catalysts for the gas‐phase acetoxylation of toluene, less noble co‐components (e.g., Mn, Co, and Sb) spread over the support in their oxidic form and changed their valence state on stream. Incorporated atoms such as C or a small part of the Sb affect the electronic structure of Pd. For the noble Au, only a weak interaction with the support and Pd was observed during time on stream. Only XAS at the K‐edges together with investigations of the Pd L‐edge for a better understanding of the electronic structure, supplemented by STEM for elemental mapping, allow such detailed insights. 相似文献
46.
Fish are selenium rich foodstuffs and a major selenium source for the Japanese population. Niboshi is processed from Japanese anchovy (Engraulis japonicus) and commonly used to prepare soup stock for Japanese dishes. In this study, we characterized selenium species in the Niboshi extract by ultrafiltration, ion-exchange chromatography and mass spectrometry. Selenium species in the Niboshi were more extractable by polar solvents (water and ethanol) than an apolar one (hexane) along with amino acids and proteinous species. Selenium in the water-extract from the Niboshi was mostly ascribed to organoselenium compounds with a molecular mass less than 5?kDa. Although selenoamino acids and selenoproteins and their fragments were involved in the extract, a large portion of the selenium species appeared to be low-molecular-mass organoselenium compounds other than selenoamino acids and their derivatives. Ion-exchange chromatographic separations revealed that most of the selenium species in the extract possess anionic and/or amphoteric characteristics. One of these selenium species from the Niboshi extract was detected at m/z 577 for 80Se by mass spectrometry subsequent to ion-pair extraction. 相似文献
47.
Robert A. Mayanovic Alan J. Anderson Hingure A. N. Dharmagunawardhane Sakura Pascarelli Giuliana Aquilanti 《Journal of synchrotron radiation》2012,19(5):797-805
Radiolysis‐induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X‐ray micro‐beam in a WO3 + H2O system at 873 K and 200 MPa. In situ Fe K‐edge energy‐dispersive X‐ray absorption spectroscopy (ED‐XAS) measurements were made on Fe(II)Cl2 aqueous solutions to 773 K in order to study the kinetics of high‐temperature reactions of Fe2+ and Fe3+ ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe2+ ion at 573 K and reduction of Fe3+ at temperatures between 673 and 773 K and of the Fe2+ ion at 773 K. The edge‐energy drift evident in the ED‐XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe2+ and Fe3+ ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible. 相似文献
48.
Gemma Guilera Bernard Gorges Sakura Pascarelli Hugo Vitoux Mark A. Newton Carmelo Prestipino Yasutaka Nagai Naoyuki Hara 《Journal of synchrotron radiation》2009,16(5):628-634
Two novel high‐temperature reactors for in situ X‐ray absorption spectroscopy (XAS) measurements in fluorescence are presented, each of them being optimized for a particular purpose. The powerful combination of these reactors with the turbo‐XAS technique used in a dispersive‐XAS beamline permits the study of commercial three‐way catalysts under realistic gas composition and temporal conditions. 相似文献
49.
Lorine Brülisauer Gina Valentino Sakura Morinaga Kübra Cam Dr. Jens Thostrup Bukrinski Prof. Dr. Marc A. Gauthier Prof. Dr. Jean‐Christophe Leroux 《Angewandte Chemie (International ed. in English)》2014,53(32):8392-8396
Disulfide‐containing IgG‐, Fc‐, or albumin‐based prodrugs that rely on FcRn‐trafficking by endothelial cells for prolonged circulation in the body might be hampered by premature bio‐reduction processes during FcRn‐mediated recycling events. A detailed bio‐reduction analysis of redox‐sensitive albumin conjugates in two FcRn‐expressing cell lines has been performed. The obtained results indicate that the FcRn‐mediated recycling pathway is not (or is only poorly) bio‐reducing. 相似文献
50.
Abstract— Evidence of complex formation between pyrene and polar solvent molecules has been obtained by monitoring the S1 ,← S0 and S2 ← S0 absorption spectra of pyrene. The solvents employed are propionitrile, valeronitrile, dichloromethane, and dioxane. The stabilization energy is found to be small relative to general hydrogen bond energies, but somewhat high relative to the Boltzmann energy. These are in good accord with the findings of Lianos and Georghiou [ Photochem. Photobiol. 30 ,355 (1979)] that pyrene forms 1:1 molecular complexes with several dipolar solvents in the ground state. 相似文献