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排序方式: 共有4915条查询结果,搜索用时 31 毫秒
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Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献
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Faure Thierry M. Dumas Laurent Montagnier Olivier 《Theoretical and Computational Fluid Dynamics》2020,34(1):79-103
Theoretical and Computational Fluid Dynamics - The aerodynamic characteristics of two neighboring airfoils are greatly different from those of a single airfoil, for both attached and detached flow... 相似文献
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The Reductive Dehydration of Cellulose by Solid/Gas Reaction with TiCl4 at Low Temperature: A Cheap,Simple, and Green Process for Preparing Anatase Nanoplates and TiO2/C Composites 下载免费PDF全文
Sandrine Plumejeau Dr. Matthieu Rivallin Prof. Stephan Brosillon Prof. André Ayral Dr. Laurent Heux Prof. Bruno Boury 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17262-17268
Metal oxides and metal oxide/carbon composites are entering the development of new technologies and should therefore to be prepared by sustainable chemistry processes. Therefore, a new aspect of the reactivity of cellulose is presented through its solid/gas reaction with vapour of titanium(IV) chloride in anhydrous conditions at low temperature (80 °C). This reaction leads to two transformations both for cellulose and titanium(IV) chloride. A reductive dehydration of cellulose is seen at the lowest temperature ever reported and results in the formation of a carbonaceous fibrous solid as the only carbon‐containing product. Simultaneously, the in situ generation of water leads to the formation of titanium dioxide with an unexpected nanoplate morphology (ca. 50 nm thickness) and a high photocatalytic activity. We present the evidence showing the evolution of the cellulose and the TiO2 nanostructure formation, along with its photocatalytic activity. This low‐temperature process avoids any other reagents and is among the greenest processes for the preparation of anatase and also for TiO2/carbon composites. The anisotropic morphology of TiO2 questions the role of the cellulose on the growing process of these nanoparticles. 相似文献
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Insights into the Cascade Reaction of CO and Heteroallenes Mediated by Dinitrogen Hafnocene Complexes: The Indirect Effect of Nitride's Nucleophilicity 下载免费PDF全文
Dr. Christos E. Kefalidis Prof. Dr. Laurent Maron 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(14):4743-4747
A DFT mechanistic exploration of the reactivity of the dinitrogen hafnocene complex, [{(η5‐C5H2‐1,2,4‐Me3)2Hf}2(μ2‐N2)], towards mixtures of CO/CO2 and CO/OCNtBu is reported. The crucial role of the nitride intermediate is highlighted, as well as the importance of the bridging mode of the cyanate ligand between the two Hf metal atoms throughout the process. Interestingly, the CO2 addition to the nitride intermediate occurs through an outer‐sphere transition state, whereas the addition of the heteroallene is governed by the steric congestion imposed by cyclopentadienyl ligands. 相似文献
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Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe 下载免费PDF全文
Dr. Sophie Carron Dr. Maarten Bloemen Prof. Luce Vander Elst Prof. Sophie Laurent Prof. Thierry Verbiest Prof. Tatjana N. Parac‐Vogt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4521-4527
A new prototype consisting of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles decorated with europium(III) ions encapsulated in a DO3A organic scaffold was designed as a platform for further development of bimodal contrast agents for MRI and optical imaging. The USPIO nanoparticles act as negative MRI contrast agents, whereas the europium(III) ion is a luminophore that is suitable for use in optical imaging detection. The functionalized USPIO nanoparticles were characterized by TEM, DLS, XRD, FTIR, and TXRF analysis, and a full investigation of the relaxometric and optical properties was conducted. The typical luminescence emission of europium(III) was observed and the main red emission wavelength was found at 614 nm. The relaxometric study of these ultrasmall nanoparticles showed r2 values of 114.8 mm ?1Fes?1 at 60 MHz, which is nearly double the r2 relaxivity of Sinerem®. 相似文献
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Dr. Franck Ulm Dr. Yann Cornaton Dr. Jean-Pierre Djukic Prof. Michael J. Chetcuti Prof. Vincent Ritleng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(41):8916-8925
The pentamethylcyclopentadienyl N-heterocyclic carbene nickel complex [Ni(η5-C5Me5)Cl(IMes)] (IMes=1,3-dimesitylimidazol-2-ylidene) efficiently catalyses the anti-Markovnikov hydroboration of alkenes with catecholborane in the presence of a catalytic amount of potassium tert-butoxide, and joins the very exclusive club of nickel catalysts for this important transformation. Interestingly, the regioselectivity can be reversed in some cases by using pinacolborane instead of catecholborane. Mechanistic investigations involving control experiments, 1H and 11B NMR spectroscopy, cyclic voltammetry, piezometric measurements and DFT calculations suggest an initial reduction of the NiII precursor to a NiI active species with the concomitant release of H2. The crucial role of the alkoxo-catecholato-borohydride species resulting from the reaction of potassium tert-butoxide with catecholborane in the formation of an intermediate nickel-hydride species that would then be reduced to the NiI active species, is highlighted. 相似文献