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951.
We study the expectation value of the phase of the fermion determinant for Wilson lattice fermions with chemical potential. We use quenched SU(3) ensembles and implement a recently proposed exact dimensional reduction of the fermion determinant. Ensembles at several temperatures below and above the phase transition are studied and we analyze the role of the quark mass, the temperature, the volume and the topological sectors. We compare our numerical results to predictions from chiral perturbation theory. 相似文献
952.
Marina S. Fonari Eduard V. Ganin Wen‐Jwu Wang 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(7):o431-o433
In the centrosymmetric formula unit of the title complex, C8H16O4·2C18H16S, the 1,4,7,10‐tetraoxacyclododecane molecule adopts the biangular [66] conformation, and the triphenylmethanethiol molecules are linked to the macrocycle via a long S—H⋯O hydrogen bond [S⋯O = 3.460 (2) Å and S—H⋯O = 161 (2)°]. Attractive interactions of phenyl groups in edge‐to‐face conformations combine inversion‐related formula units into chains running along the [111] direction in the crystal structure. Association of the chains into sheets is achieved via C—H⋯π interactions. 相似文献
953.
954.
Irina Malakhova Yuliya Parotkina Marina Palamarchuk Marina Eliseikina Aleksandr Mironenko Alexey Golikov Svetlana Bratskaya 《Molecules (Basel, Switzerland)》2021,26(15)
The feasibility of several approaches to the fabrication of monolith composite cryogels containing transition-metal ferrocyanides for Cs+ ion uptake has been evaluated. Although in the series of investigated metal ion precursors (Cu(II), Zn(II), Ni(II), and Co(II)), in situ formation of the sorption active phase in polyethyleneimine (PEI) cryogel was feasible only in the case of Zn(II) ferrocyanide, this approach has shown significant advantages over the immobilization of ex situ synthesized ferrocyanide nanoparticles. Nanoparticles of the mixed ferrocyanide Zn1.85K0.33[Fe(CN)6] formed in situ had an average size of 516 ± 146 nm and were homogeneously distributed in the monolith located at the polymer surface rather than embedded in the matrix. The Young modulus of the PEI cryogel increased after modification from 25 to 57 kPa, but composites maintained high permeability to the flow. Sorption of Cs+ ions has been investigated at superficial velocity up to 8 m/h. Steep breakthrough profiles and uptake efficiency of >99.5% until breakthrough point confirmed that a supermacroporous structure of the monolith composite assured good mass transfer, so that intraparticle diffusion was not the limiting stage of sorption kinetics. Application of the rate-constant distribution model (RCD model) to analyze the breakthrough curves of Cs+ sorption allowed the identification of two types of sorption sites with a difference in sorption rate constants of ~1 log unit. Most likely, sorption on “fast” sorption sites was governed by ion exchange between Cs+ ions in solution and K+ ions in the ferrocyanide lattice. Cs-137 radionuclide removal was investigated using the monolith composite columns of various geometries at superficial velocity up to the 6.6 m/h; specific gamma activity was reduced from 265 kBq/L to the background level, showing high potential of these materials for POU application. 相似文献
955.
Artem A. Zemtsov Marina I. Struchkova Pavel A. Belyakov Vladimir A. Tartakovsky 《Tetrahedron letters》2009,50(25):2998-7806
A method for the trifluoromethylation of arylidene Meldrum’s acids using Me3SiCF3 followed by transformation of the initial products to CF3-substituted esters and alcohols is described. The sequence of reactions is performed without isolation of intermediate compounds furnishing the final products in good overall yields. 相似文献
956.
Complexes of poly(propylene imine) dendrimers D8[DAB-dendr-(NH2)8] and D32 [DAB-dendr-(NH2)32] were prepared by interaction of the dendrimers with transition metal salts such as FeCl3.6H2O; CoCl2.6H2O; CuCl2.2H2O; VOSO4.5H2O; Na2MoO4.2H2O and Na2WO4.2H2O at room temperature in aqueous solutions. The content of metal ions in the complexes was found to be from 8.2 to 69.6 mg metal ion/g polymer carrier. The complexes were characterized by using IR, UV-VIS, Moessbauer spectroscopy and EPR. The anticipated co-ordination structure of the compounds was suggested. It was found that the order of the catalytic activity of the complexes of poly(propylene imine) dendrimers D8 and D32 in the reaction of epoxidation of cyclohexene with organic hydroperoxides such as tert-butyl hydroperoxide (t-BHP), ethylbenzene hydroperoxide (EBHP) and cumene hydroperoxide (CHP) was as follows: D32-MoО22+>D32-VО2+>D32-WО22+ > D32-Co2+ > D32-Cu2+>D32-Fe3+. The order of reactivity of organic hydroperoxides in the reaction studied was: t-BHP > EBHP > CHP. 相似文献
957.
Olga V. Turova Eugenia V. Starodubtseva Maxim G. Vinogradov Vladimir A. Ferapontov Marina I. Struchkova 《Tetrahedron: Asymmetry》2009,20(18):621-2124
The catalytic asymmetric hydrogenation of acylsuccinates using RuCl3 as a precatalyst and atropisomeric diphosphines as chiral auxiliaries allows the synthesis of optically active 2-alkylparaconic acid esters in preparative yields with enantioselectivities up to 99.5% ee. 相似文献
958.
Lorenzo Tei Marina Benzi Filip Kielar Mauro Botta Camilla Cavallotti Giovanni Battista Giovenzana Silvio Aime 《Helvetica chimica acta》2009,92(11):2414-2426
Two new derivatives based on an s‐triazine structural motif were synthesized by attaching two 2,2′‐hydrazinylidenebis[acetic acid] moieties to the triazine ring to reach an overall heptadenticity for the complexation of lanthanide(III) cations. The remaining reactive site was exploited for the substitution with a functionizable amino group (see H4 L1 ) and a lipophilic moiety (see H4 L2 ). Luminescence‐lifetime determinations revealed the presence of a single H2O molecule coordinated for [Eu( L1 )]. A complete 1H‐NMR relaxometric study was carried out for the octacoordinated [Gd( L1 )] and [Gd( L2 )] complexes. A remarkably long H2O residence lifetime (298τM =5.2 μs) was found by 17O‐NMR in the case of [Gd( L1 )]. Micelle formation of the lipophilic complex [Gd( L2 )] was evidenced, the critical micellization concentration (cmc) determined, and relaxometric properties of the system investigated. 相似文献
959.
Alexey V. Garshev Prof. Vladimir K. Ivanov Alina A. Krotova Darya G. Filatova Elizaveta A. Konstantinova Daniil O. Naberezhnyi Nikolay O. Khmelevsky Artem V. Marikutsa Pavel A. Kots Andrey V. Smirnov Prof. Marina N. Rumyantseva Prof. Alexander M. Gaskov Valeriy V. Krivetskiy 《Chemphyschem》2019,20(15):1985-1996
Understanding ammonia oxidation over metal oxide surfaces is crucial for improving its detection with resistive type gas sensors. Formation of NOx during this process makes sensor response and calibration unstable. Cr-doping of nanocrystalline metal oxides has been reported to suppress NO2 sensitivity and improve response towards NH3, however the exact mechanism of such chromium action remained unknown. Herein, by using EPR spectroscopy we demonstrate formation of Cr(VI) lattice defects on the surface of nanocrystalline Cr-doped SnO2. Enhancement of Cr-doped SnO2 surface acidity and ammonia adsorption as a result has been revealed by using in situ IR spectroscopy. Moreover, a decrease in concentration of free electrons in the conduction band has been shown as a result of substitutional Cr(III) defects formation. Weaker NOx chemisorption during ammonia oxidation over SnO2 surface after Cr doping has been found with the use of mass-spectrometry assisted NH3 thermo-programmed desorption. The given example of surface acidity adjustment and electronic configuration by means of doping may find use in the design of new gas-sensing metal oxide materials. 相似文献
960.
Several Bauhinia species are widely used in Southern South America in the treatment of infections, pain and several diseases including diabetes. Flavonoid compounds based on quercetin and kaempferol glycoside derivatives are believed to be responsible for their therapeutic properties. To investigate this, we have studied two native species from Argentina: B. uruguayensis (BU) and B. forficata subsp. pruinosa (BF). We have analyzed the major polyphenol components in hydro-methanolic extracts of leaves, by high performance liquid chromatography tandem mass spectrometry. Chromatographic analysis yielded five main compounds in BF, corresponding to rutinosides and rhamnosides derivatives of kaempferol and quercetin, which are considered chemotaxonomic markers and responsible for antioxidant activity. The presence of kaempferitrin, an antidiabetic agent, has been confirmed. In extracts of BU, four major compounds were identified as rhamnosides and galloyl derivates from quercetin and kaempferol. One of these compounds, quercitrin-3-rhamnoside may confer anti-inflammatory and analgesic properties to BU extracts. 相似文献