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排序方式: 共有495条查询结果,搜索用时 15 毫秒
141.
Dr. Romain Haudecoeur Loic Stefan Dr. David Monchaud 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12739-12747
Natural G‐quartets, a cyclic and coplanar array of four guanine residues held together through a Watson–Crick/Hoogsteen hydrogen‐bond network, have received recently much attention due to their involvement in G‐quadruplex DNA, an alternative higher‐order DNA structure strongly suspected to play important roles in key cellular events. Besides this, synthetic G‐quartets (SQ), which artificially mimic native G‐quartets, have also been widely studied for their involvement in nanotechnological applications (i.e., nanowires, artificial ion channels, etc.). In contrast, intramolecular synthetic G‐quartets (iSQ), also named template‐assembled synthetic G‐quartets (TASQ), have been more sparingly investigated, despite a technological potential just as interesting. Herein, we report on a particular iSQ named PNADOTASQ, which demonstrates very interesting properties in terms of DNA and RNA interaction (notably its selective recognition of quadruplexes according to a bioinspired process) and catalytic activities, through its ability to perform peroxidase‐like hemin‐mediated oxidations either in an autonomous fashion (i.e., as pre‐catalyst for TASQzyme reactions) or in conjunction with quadruplex DNA (i.e., as enhancing agents for DNAzyme processes). These results provide a solid scientific basis for TASQ to be used as multitasking tools for bionanotechnological applications. 相似文献
142.
Elise Romain Carolin Fopp Fabrice Chemla Franck Ferreira Olivier Jackowski Martin Oestreich Alejandro Perez‐Luna 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(42):11515-11519
The silylzincation of terminal ynamides is achieved through a radical‐chain process involving (Me3Si)3SiH and R2Zn. A potentially competing polar mechanism is excluded on the basis of diagnostic control experiments. The unique feature of this addition across the CC bond is its trans selectivity. One‐pot electrophilic substitution of the C Zn bond by CuI‐mediated C C bond formation and subsequent manipulation of the C Si bond provides a modular access to Z‐α,β‐disubstituted enamides. 相似文献
143.
Converging algorithm for a class of BMI applied on state-dependent stabilization of switched systems
Alexandre Kruszewski Romain Bourdais Wilfrid Perruquetti 《Nonlinear Analysis: Hybrid Systems》2011,5(4):647-654
In this paper, a design of a stabilizing state-dependent switching law is presented. First, it is based on a new reformulation of this control problem into a class of BMI (Bilinear Matrix Inequality) problem. The originality of this reformulation is that it will be used, in a second part, by an algorithm dedicated to solve this class of BMI without loss of generality. The construction of this algorithm is then specified, and the proof of its convergence is given for the two-subsystem case. The last part of the work consists in presenting the problem for a polytopic switching system, and how the previous algorithm can be extended. The proposed scheme is illustrated by an academical example. 相似文献
144.
Lacombe R Moussou P Aurégan Y 《The Journal of the Acoustical Society of America》2011,130(5):2662-2672
An experimental investigation of the parameters controlling the whistling frequency and amplitude of an orifice in a confined turbulent flow is undertaken. A circular single hole orifice with sharp edges, a hole diameter equal to 0.015 m and a thickness equal to 0.005 m, is arranged in an air test rig with an inner diameter equal to 0.03 m. The Mach number ranges around 0.02 and the Reynolds number around 10(4). Variable reflecting boundary conditions are arranged upstream and downstream, and several flow velocities are tested. It is found that the Bode-Nyquist criterion accurately predicts the conditions of self-sustained oscillation and the value of the whistling frequency. Furthermore, it is found that the acoustic velocity in whistling regime varies from 1% to 15% of the steady flow velocity, and that it depends on the overall acoustic reflection of the surrounding pipe and on the Strouhal number. 相似文献
145.
We introduce a scheme that integrates a digital key in a phase-chaos electro-optical delay system for optical chaos communications. A pseudorandom binary sequence (PRBS) is mixed within the chaotic dynamics in a way that a mutual concealment is performed; e.g., the time delay is hidden by the binary sequence, and the PRBS is also masked by the chaos. In addition to bridging the gap between algorithmic symmetric key cryptography and chaos-based analog encoding, the proposed approach is intended to benefit from the complex algebra mixing between a (pseudorandom) Boolean variable, and another continuous time (chaotic) variable. The scheme also provides a large flexibility allowing for easy reconfigurations to communicate securely at a high bit rate between different systems. 相似文献
146.
Mgane Bernard Romain Lucas Hatim Laadoua Zineb Khaldi Nicolas Pradeilles Olivier Rapaud Sylvie Foucaud Rachida Zerrouki Franois Brouillette 《先进技术聚合物》2020,31(2):319-327
Porous silicon carbide (SiC) materials were fabricated using the polymer‐derived ceramics method with kraft pulp papers (KPP) and a commercial polycarbosilane, the allylhydridopolycarbosilane (AHPCS), as starting materials. For this, KPP, propargylated KPP, or phosphorylated KPP were used to be impregnated by the AHPCS, with or without Karstedt catalyst. The pyrolysed materials were characterized at different stages, by using thermogravimetric analysis (TGA) coupled with mass spectrometry, X‐ray diffraction (XRD), and scanning electron microscopy (SEM). Depending on the nature of the initial template, various architectured SiC ceramics were successfully obtained with adjustable porosities. The key role of the previous functionalization of the papers was highlighted in terms of interactions at the interface between the polymer and the lignocellulosic handsheets. It led to either replica or sacrificial template methods. Thus, it was possible to tune the open porosity of the porous carbon and β‐SiC materials between 14.8% and 92.9%, with ceramic yields varying from 12% to 71%. 相似文献
147.
Hailong Yuan Florian Massuyeau Nicolas Gautier Antoine Blaise Kama Eric Faulques Fei Chen Qiang Shen Lianmeng Zhang Michael Paris Romain Gautier 《Angewandte Chemie (International ed. in English)》2020,59(7):2802-2807
Near‐UV‐pumped white‐light‐emitting diodes with ultra‐high color rendering and decreased blue‐light emission is highly desirable. However, discovering a single‐phase white light emitter with such characteristics remains challenging. Herein, we demonstrate that Mn doping as low as 0.027 % in the hybrid post‐perovskite type (TDMP)PbBr4 (TDMP=trans‐2,5‐dimethylpiperaziniium) enables to achieve a bright pure white emission replicating the spectrum of the sun's rays. Thus, a white phosphor exhibiting an emission with CIE coordinates (0.330, 0.365), a high photoluminescence quantum yield of 60 % (new record for white light emission of hybrid lead halides), and an ultra‐high color rendering index (CRI=96, R9=91.8), corresponding to the record value for a single phase emitter was obtained. The investigation of the photoluminescence properties revealed how free excitons, self‐trapped excitons, and low amount of Mn dopants are coupled to give rise to such pure white emission. 相似文献
148.
Roza Bouchal Zhujie Li Chandra Bongu Steven Le Vot Romain Berthelot Benjamin Rotenberg Frederic Favier Stefan A. Freunberger Mathieu Salanne Olivier Fontaine 《Angewandte Chemie (International ed. in English)》2020,59(37):15913-15917
Water‐in‐salt electrolytes based on highly concentrated bis(trifluoromethyl)sulfonimide (TFSI) promise aqueous electrolytes with stabilities nearing 3 V. However, especially with an electrode approaching the cathodic (reductive) stability, cycling stability is insufficient. While stability critically relies on a solid electrolyte interphase (SEI), the mechanism behind the cathodic stability limit remains unclear. Now, two distinct reduction potentials are revealed for the chemical environments of free and bound water and that both contribute to SEI formation. Free water is reduced about 1 V above bound water in a hydrogen evolution reaction (HER) and is responsible for SEI formation via reactive intermediates of the HER; concurrent LiTFSI precipitation/dissolution establishes a dynamic interface. The free‐water population emerges, therefore, as the handle to extend the cathodic limit of aqueous electrolytes and the battery cycling stability. 相似文献
149.
On the Importance of Decarbonylation as a Side‐Reaction in the Ruthenium‐Catalysed Dehydrogenation of Alcohols: A Combined Experimental and Density Functional Study 下载免费PDF全文
Dr. Nicolas Sieffert Romain Réocreux Patrizia Lorusso Prof. Dr. David J. Cole‐Hamilton Prof. Dr. Michael Bühl 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):4141-4155
We report a density functional study (B97‐D2 level) of the mechanism(s) operating in the alcohol decarbonylation that occurs as an important side‐reaction during dehydrogenation catalysed by [RuH2(H2)(PPh3)3]. By using MeOH as the substrate, three distinct pathways have been fully characterised involving either neutral tris‐ or bis‐phosphines or anionic bis‐phosphine complexes after deprotonation. α‐Agostic formaldehyde and formyl complexes are key intermediates, and the computed rate‐limiting barriers are similar between the various decarbonylation and dehydrogenation paths. The key steps have also been studied for reactions involving EtOH and iPrOH as substrates, rationalising the known resistance of the latter towards decarbonylation. Kinetic isotope effects (KIEs) were predicted computationally for all pathways and studied experimentally for one specific decarbonylation path designed to start from [RuH(OCH3)(PPh3)3]. From the good agreement between computed and experimental KIEs (observed kH/kD=4), the rate‐limiting step for methanol decarbonylation has been ascribed to the formation of the first agostic intermediate from a transient formaldehyde complex. 相似文献
150.
We consider the exit measure of super Brownian motion with a stable branching mechanism of a smooth domain D of ℝ
d
. We derive lower bounds for the hitting probability of small balls for the exit measure and upper bounds in the critical
dimension. This completes results given by Sheu [22] and generalizes the results of Abraham and Le Gall [2]. Because of the
links between exits measure and partial differential equations, those results imply bounds on solutions of elliptic semi-linear
PDE. We also give the Hausdorff dimension of the support of the exit measure and show it is totally disconnected in high dimension.
Eventually we prove the exit measure is singular with respect to the surface measure on ∂D in the critical dimension. Our main tool is the subordinated Brownian snake introduced by Bertoin, Le Gall and Le Jan [4].
Received: 6 December 1999 / Revised version: 9 June 2000 / Published online: 11 December 2001 相似文献