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861.
We study the existence of strong solutions to the three-dimensional Navier-Stokes initial-boundary value problem in the domain, , exterior to a rigid body that rotates with constant angular velocity, . We show that when the initial data, u0, are prescribed in an appropriate functional class, a strong solution exists at least in some finite time interval. Moreover, the solution exists for all times, provided u0, in suitable norm, and the magnitude of do not exceed a certain constant depending only on the kinematic viscosity and on the regularity of . In this latter case, we also show that the velocity field converges to the velocity field of the corresponding steady-state solution. 相似文献
862.
M. Cristina?Cerutti Fausto?Ferrari Sandro?SalsaEmail author 《Archive for Rational Mechanics and Analysis》2004,171(3):329-348
We prove C
1,
regularity of Lipschitz free boundaries of two-phase problems for linear elliptic operators with Hölder continuous coefficients. 相似文献
863.
Highly Stereoselective Synthesis of Natural‐Product‐Like Hybrids by an Organocatalytic/Multicomponent Reaction Sequence
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M. Sc. Radell Echemendía M. Sc. Alexander F. de La Torre M. Sc. Julia L. Monteiro M. Sc. Michel Pila Prof. Dr. Arlene G. Corrêa Prof. Dr. Bernhard Westermann Prof. Dr. Daniel G. Rivera Prof. Dr. Márcio W. Paixão 《Angewandte Chemie (International ed. in English)》2015,54(26):7621-7625
In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one‐pot process comprising an organocatalytic conjugate addition of 1,3‐dicarbonyls to α,β‐unsaturated aldehydes followed by an intramolecular isocyanide‐based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity‐generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties. 相似文献
864.
Andreu Presa Rosa F. Brissos Ana Belén Caballero Ivana Borilovic Dr. Luís Korrodi‐Gregório Prof. Ricardo Pérez‐Tomás Dr. Olivier Roubeau Prof. Patrick Gamez 《Angewandte Chemie (International ed. in English)》2015,54(15):4561-4565
The photoactivation of potential anticancer metal complexes is a hot topic of current research as it may lead to the development of more selective drugs. Photoactivated chemotherapy (PACT) with coordination compounds is usually based on a (photo)chemical reaction taking place at the metal center. Herein, a new strategy is exploited that consists of “photomodifying” a ligand coordinated to metal ions. Platinum(II) complexes from photoswitchable 1,2‐dithienylethene‐containing ligands have been prepared, which exhibit two interconvertible photoisomeric forms that present distinct DNA‐interacting properties and cytotoxic behaviors. 相似文献
865.
Targeting the Two Oncogenic Functional Sites of the HPV E6 Oncoprotein with a High‐Affinity Bivalent Ligand
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866.
Metal‐Doped Nitrogenated Carbon as an Efficient Catalyst for Direct CO2 Electroreduction to CO and Hydrocarbons
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Dr. Ana Sofia Varela Dr. Nastaran Ranjbar Sahraie Julian Steinberg Wen Ju Dr. Hyung‐Suk Oh Prof. Dr. Peter Strasser 《Angewandte Chemie (International ed. in English)》2015,54(37):10758-10762
This study explores the kinetics, mechanism, and active sites of the CO2 electroreduction reaction (CO2RR) to syngas and hydrocarbons on a class of functionalized solid carbon‐based catalysts. Commercial carbon blacks were functionalized with nitrogen and Fe and/or Mn ions using pyrolysis and acid leaching. The resulting solid powder catalysts were found to be active and highly CO selective electrocatalysts in the electroreduction of CO2 to CO/H2 mixtures outperforming a low‐area polycrystalline gold benchmark. Unspecific with respect to the nature of the metal, CO production is believed to occur on nitrogen functionalities in competition with hydrogen evolution. Evidence is provided that sufficiently strong interaction between CO and the metal enables the protonation of CO and the formation of hydrocarbons. Our results highlight a promising new class of low‐cost, abundant electrocatalysts for synthetic fuel production from CO2. 相似文献
867.
Diferrocenophosphaborin: A Planar‐Chiral,Redox‐Active and Anion‐Responsive Ambiphilic Ligand
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Dr. Jiawei Chen Didier A. Murillo Parra Prof. Dr. Roger A. Lalancette Prof. Dr. Frieder Jäkle 《Angewandte Chemie (International ed. in English)》2015,54(35):10202-10205
A new class of Janus‐like ambiphilic ligands is introduced. The rigid diferrocene backbone in heterocycles 4‐SnP and 4‐BP creates an unprecedented chiral environment as demonstrated by multinuclear NMR and single‐crystal X‐ray studies. In addition, the ligands are redox‐responsive and the Lewis acidic borane moiety in 4‐BP can be exploited to further tune the properties: a clear decrease in the CO stretching frequency of a Vaska‐type RhI complex 5‐BP is observed upon addition of fluoride ions. Thus, the Lewis acid and Lewis base sites influence each other and their strength can be modulated by redox chemistry and anion binding. 相似文献
868.
Computational Study of Proton Transfer in Tautomers of 3‐ and 5‐Hydroxypyrazole Assisted by Water
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Dr. Cristina Trujillo Dr. Goar Sánchez‐Sanz Prof. Ibon Alkorta Prof. José Elguero 《Chemphyschem》2015,16(10):2140-2150
The tautomerism of 3‐ and 5‐hydroxypyrazole is studied at the B3LYP, CCSD and G3B3 computational levels, including the gas phase, PCM–water effects, and proton transfer assisted by water molecules. To understand the propensity of tautomerization, hydrogen‐bond acidity and basicity of neutral species is approached by means of correlations between donor/acceptor ability and H‐bond interaction energies. Tautomerism processes are highly dependent on the solvent environment, and a significant reduction of the transition barriers upon solvation is seen. In addition, the inclusion of a single water molecule to assist proton transfer decreases the barriers between tautomers. Although the second water molecule further reduces those barriers, its effect is less appreciable than the first one. Neutral species present more stable minima than anionic and cationic species, but relatively similar transition barriers to anionic tautomers. 相似文献
869.
Influence of the Solvent on the “Casting” Methodology for MWCNT‐Modified Glassy Carbon and Platinum Electrodes
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Ana Carolina Ângelo Dorim Herbert Aleixo Edilton de Souza Barcellos Leonardo Luiz Okumura 《Electroanalysis》2015,27(11):2663-2669
The choice of electrode material and surface preparation method are usually dictated by the suitability of the electrode to observe an electrochemical parameter, such as heterogeneous electron transfer rate, surface coverage, or redox potential. Thus, the glassy carbon (GC) and platinum (Pt) electrodes were modified with multiwalled carbon nanotubes (MWCNT) by direct “casting” modification using nine different aliquots of solvents. After drying at room temperature, the modified electrode showed distinct redox peaks corresponding to ferrocyanide oxidation/reduction. Using chemometrics, the cyclic voltammograms with higher current intensity were obtained for those in which ethanol, water and acetone as dispersing agents were used for GCE and dimethylformamide, water and acetone for Pt electrode modification. 相似文献
870.
Identification strategies for flame retardants employing time‐of‐flight mass spectrometric detectors along with spectral and spectra‐less databases
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Alin C. Ionas Ana Ballesteros Gómez Pim E. G. Leonards Adrian Covaci 《Journal of mass spectrometry : JMS》2015,50(8):1031-1038
In the past, the preferred strategy for the identification of unknown compounds was to search in an appropriate mass spectral database for spectra obtained using either electron ionisation (GC‐MS analyses) or collision‐induced dissociation (LC‐MS/MS analyses). Recently, an increase has been seen in the use of accurate mass instruments and spectra‐less databases, based on monoisotopic accurate mass alone. In this article, we describe a systematic workflow for the screening and identification of new flame retardants. This approach utilises LC‐quadrupole‐time‐of‐flight MS and spectra‐less databases based only on monoisotopic accurate mass for the identification of ‘unknowns’. An in‐house database was built, and the input parameters used in the data analysis process were optimised for flame retardant chemicals, so that it can be easily transferred to other laboratories. The procedure was successfully applied to dust, foam and textiles from car interiors and indoor consumer products. The developed method was demonstrated for the main new flame retardant present in Antiblaze V6 and for the three unreported reaction by‐products/impurities present in the same technical mixture. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献