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排序方式: 共有211条查询结果,搜索用时 15 毫秒
91.
Sebastien Piant Alexandre Specht Boris Zemelman Attila Losonczy 《Molecular Crystals and Liquid Crystals》2016,627(1):56-65
ABSTRACTGeneral molecular engineering rules for the optimization of two-photon sensitive cages are presented and examples for nitrobenzyl, indole and nitrophenethyl platforms are highlighted. The efficiency of electron donor and acceptor groups in dipolar structures and the length of the conjugated system in the photolabile protecting group on two-photon uncaging efficiency will be discussed, as well as the emergence of symmetrical platform based on bis-electron donor or on quadrupolar architectures. We will then present our first results on the nano-structuration of donor-acceptor systems based on nitrophenetyl platform using diethyleneglycol or pentaerythritol cores. 相似文献
92.
Dzmitry Sodzel Volodymyr Khranovskyy Valerio Beni Anthony P. F. Turner Roman Viter Martin O. Eriksson Per-Olof Holtz Jean-Marc Janot Mikhael Bechelany Sebastien Balme Valentyn Smyntyna Ekaterina Kolesneva Lyudmila Dubovskaya Igor Volotovski Arnolds Ubelis Rositsa Yakimova 《Mikrochimica acta》2015,182(9-10):1819-1826
93.
A Comparison of Primary and Secondary Hydrogen Abstraction from Organophosphates by Hydroxyl Radical
Douglas S. Burns Marshall G. Cory Decarlos E. Taylor Steven W. Bunte Keith Runge Joseph L. Vasey 《国际化学动力学杂志》2013,45(3):187-201
To compare the effect of primary and secondary C? H bonds on hydrogen?atom abstraction by hydroxyl radical, rate constants for the reactions of OH radicals with trimethyl phosphate [TMPO, (CH3O)3P(O)] and triethyl phosphate [TEPO, (CH3CH2O)3P(O)] have been calculated using the semiclassical flux–flux autocorrelation function (SCFFAF) method and compared with experimental measurements over the temperature range 250–350 K. SCFFAF specifies that structures be obtained at the CCSD/6?31++G** level of chemical theory and the height of the activation barrier be determined using an energy extrapolation, here a variant of the G2MP2 method. Dynamics are generated in the SCFFAF method from forces computed with a transfer Hamiltonian, which provides information about the curvature of the potential energy surface in the neighborhood of the transition state (TS), as well as the required internal forces. The temperature?dependent reaction rate constants are calculated for the various possible abstraction pathways, primary hydrogen atom abstraction in the case of TMPO, and primary and secondary in the case of TEPO. Since two energetically favorable parent structures for each system are included in the model, the activation energy is calculated with respect to the conformer that connects to a given TS and the total rate constant at a given temperature is Boltzmann weighted with respect to the parent conformer. The computed temperature?dependent rate curves are consistent with published experimental data in both magnitude and temperature dependence. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 187–201, 2013 相似文献
94.
We introduce a model for self-organized dynamics which, we argue, addresses several drawbacks of the celebrated Cucker-Smale
(C-S) model. The proposed model does not only take into account the distance between agents, but instead, the influence between
agents is scaled in term of their relative distance. Consequently, our model does not involve any explicit dependence on the number of agents; only their geometry in phase space
is taken into account. The use of relative distances destroys the symmetry property of the original C-S model, which was the
key for the various recent studies of C-S flocking behavior. To this end, we introduce here a new framework to analyze the
phenomenon of flocking for a rather general class of dynamical systems, which covers systems with non-symmetric influence matrices. In particular, we analyze the flocking behavior of the proposed model as well as other strongly asymmetric
models with “leaders”. 相似文献
95.
Mikhail K. Gratchev Galina I. Kurochkina Eric Monflier Sebastien Tilloy Herve Bricout Edward E. Nifantiev 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1489-1492
Principal peculiarities of the use of phosphocontaining cyclodextrins as a new class of supramolecular structures are discussed. For the first time cyclodextrin perphosphite has been obtained and isolated in an individual state by the treatment of g -cyclodextrin with triazolide neopentylenephosphorous acid. Cyclodextrin perphosphite exhibited an unusual transphosphorylation under reaction with some chlorophosphites. The inclusion of adamantane into the cyclodextrin cavity results in slowing this reaction down. Some water-soluble cyclodextrin derivatives displayed high activity as phase transfer catalysts in biphase catalysis. 相似文献
96.
Sebastien Blanquer Julien Tailhades Vincent Darcos Muriel Amblard Jean Martinez Benjamin Nottelet Jean Coudane 《Journal of polymer science. Part A, Polymer chemistry》2010,48(24):5891-5898
Novel 5‐Z‐amino‐δ‐valerolactone (5‐NHZ‐VL) was synthesized with an aim to prepare degradable polyesters and copolyesters having amino pendant groups. Following a straightforward and efficient synthetic pathway, 5‐NHZ‐VL was obtained in only two steps and up to 50% yield. The monomer was fully characterized by 1H NMR, 13C NMR, ESI mass spectrometry, and HPLC. Various conventional conditions were tested for this lactone ring‐opening polymerization and led to the novel corresponding poly(5‐NHZ‐VL) (Mn = 7000 g/mol; PD = 1.2). Following this homopolymerization, 5‐NHZ‐VL was copolymerized with ε‐caprolactone to generate a family of copolyesters with an amino‐group content ranging from 10 to 80%. Finally, the polyelectrolyte poly(5‐NH3+‐VL) was recovered by removal of the protecting group under acidic conditions, and integrity of the polyester backbone was confirmed by 1H NMR. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
97.
Vladimir?Kazakov Sebastien?LeurentEmail author Zengo?Tsuboi 《Communications in Mathematical Physics》2012,311(3):787-814
We propose the operatorial Baxter’s TQ-relations in a general form of the operatorial Bäcklund flow describing the nesting process for the inhomogeneous rational gl(K|M) quantum (super)spin chains with twisted periodic boundary conditions. The full set of Q-operators and T-operators on all levels of nesting is explicitly defined. The results are based on a generalization of the identities among the group characters and their group co-derivatives with respect to the twist matrix, found by one of the authors Kazakov and Vieira (JHEP 0810:050, 2008). Our formalism, based on this new “master” identity, allows a systematic and rather straightforward derivation of the whole set of nested Bethe ansatz equations for the spectrum of quantum integrable spin chains, starting from the R-matrix. 相似文献
98.
Anizan S Bichon E Duval T Monteau F Cesbron N Antignac JP Le Bizec B 《Journal of mass spectrometry : JMS》2012,47(1):131-140
The use of anabolic steroids as growth promoters for meat-producing animals is banned within the European Union. However, screening for the illegal use of natural steroid hormones still represents a difficult challenge because of the high interindividual and physiological variability of the endogenous concentration levels in animals. In this context, the development of untargeted profiling approaches for identifying new relevant biomarkers of exposure and/or effect has been emerging for a couple of years. The present study deals with an untargeted metabolomics approach on the basis of GC-MS aiming to reveal potential biomarkers signing a fraudulent administration of 4-androstenedione (AED), an anabolic androgenic steroid chosen as template. After a sample preparation based on microextraction by packed sorbent, urinary profiles of the free and deglucurono-conjugates urinary metabolites were acquired by GC-MS in the full-scan acquisition mode. Data processing and chemometric procedures highlighted 125 ions, allowing discrimination between samples collected before and after an administration of 4-AED. After a first evaluation of the signal robustness using additional and independent non-compliant samples, 17 steroid-like metabolites were pointed out as relevant candidate biomarkers. All these metabolites were then monitored using a targeted GC-MS/MS method for an additional assessment of their capacity to be used as biomarkers. Finally, two steroids, namely 5α-androstane-3β,17α-diol and 5α-androst-2-en-17-one, were concluded to be compatible with such a definition and which could be finally usable for screening purpose of AED abuse in cattle. 相似文献
99.
Tahri Z Lepski R Hsieh KY Bendeif el-E Pillet S Durand P Woike T Schaniel D 《Physical chemistry chemical physics : PCCP》2012,14(11):3775-3781
We study the properties of photoinduced metal-nitrosyl linkage isomers in sodium nitroprusside (SNP) as a function of particle size. By embedding the molecular complex at various concentrations into mesopores of silica xerogels the size of the particles can be adjusted. The ground state is characterized by X-ray diffraction, absorption and infrared spectroscopy. The physical properties of the photoswitched molecules were analysed by steady-state low-temperature absorption, infrared spectroscopy and by nanosecond transient absorption spectroscopy. The electronic structure as well as the activation energies of the metastable linkage isomers are independent of the particle size down to single isolated molecules, indicating that the SNP complexes are quasi-free inside the pores of the gel. 相似文献
100.
Galletta M Puntoriero F Campagna S Chiorboli C Quesada M Goeb S Ziessel R 《The journal of physical chemistry. A》2006,110(13):4348-4358
The six multichromophoric species 1-6, containing the potentially luminescent Ru(II) polypyridine subunits and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene fluorophores (dipyrromethene-BF(2) dyes, herein after called bodipy), have been prepared and their absorption spectra, luminescence properties (both at room temperature in fluid solution and at 77 K in rigid matrix), and redox properties have been investigated (for the structuralformulas of all the compounds, see Figure 1). For comparison purposes, also the same properties of the bodipy-based free ligands have been examined. Three of the multichromophoric species (1-3) are based on the Ru(bpy)(3)-type metal subunit, whereas 4-6 are based on the Ru(terpy)(2)-type metal subunit. Transient absorption spectroscopy at room temperature of all the compounds has also been performed. The absorption spectra of all the metal complexes show features that can be assigned to the Ru(II) polypyridine subunits and to the bodipy centers. In particular, the lowest energy spin-allowed pi-pi* transition of the bodipy groups dominates the visible region, peaking at about 530 nm. All the new complexes exhibit a rich redox behavior, with reversible processes attributed to specific sites, indicating a small perturbation of each redox center and therefore highlighting the supramolecular nature of the multichromophoric assemblies. Despite the good luminescence properties of the separated components, 1-6 do not exhibit any luminescence at room temperature; however, transient absorption spectroscopy evidences that for all of them a long-lived (microsecond time scale) excited state is formed, which is identified as the bodipy-based triplet state. Pump-probe transient absorption spectroscopy suggests that such a triplet state is formed from the promptly prepared bodipy-based (1)pi-pi* state in most cases by the intervention of a charge-separated level. At 77 K, all the complexes except complex 1 exhibit the bodipy-based fluorescence, although with a slightly shortened lifetime compared to the corresponding free ligand(s), and 4-6 also exhibit a phosphorescence assigned to the bodipy subunits. Phosphorescence of bodipy species had never been reported in the literature to the best of our knowledge: in the present cases we propose that it is an effective decay process thanks to the presence of the ruthenium heavy atom and of the closely lying (3)MLCT state of the Ru(terpy)(2)-type subunits. 相似文献