PdII‐Catalyzed Intermolecular Amination of Unactivated C(sp3)H Bonds

Pd^II‐catalyzed intermolecular amination of unactivated C(sp³)?H bonds has been successfully developed for the first time. This method provides a new way to achieve the challenging intermolecular amination of unactivated C(sp³)?H bonds, producing a variety of unnatural β²‐amino carboxylic acid analogues. This C(sp³)?H amination protocol is demonstrated with a broad substrate scope, good functional‐group tolerance, and chemoselectivity. It is operated without use of phosphine ligand or external oxidant.     

Performance evaluation and optimization of semi-dimpled slit fin

In this paper, the semi-dimpled slit fin is proposed and the characteristics of heat transfer and fluid flow are analyzed based on the orthogonal experiment design method. A serial studies on the effects of fin pitch, arrangement of semi-dimple, dimple radius on heat transfer and flow characteristics of semi-dimpled slit fin are investigated. The computational results show fin pitch (Fp) has significantly effected on the performance of heat transfer and fluid flow, the influence of arrangement of semi-dimple, the dimple radius (R) and the opening direction of semi-dimples dwindle. At the same time, compared to the general semi-dimpled slit fin, the heat transfer coefficient and JF factors of the optimized fin increase by 10.7–25.1 and 2.6–7.7 %, respectively. When Re ≤ 1,521, the overall performance of slit fin is better than that of optimized fin; while Re > 1,521, the overall performance of optimized fin is better than that of slit fin. Finally, the performance evaluation plot of enhanced heat transfer of heat exchanger is applied to analyze the optimized fin, it can be seen that optimization fin have better heat transfer performance under the same power consumption.     

费米气体在光晶格中的自俘获现象及其周期调制

研究了一维光晶格中费米气体从BCS区过渡到unitarity区研究相图及周期调制现象. 通过调节散射长度与耠合系数对相图的影响, 发现在unitarity 区, 从约瑟夫振荡到振荡自俘获及振荡自俘获到自俘获, 存在耦合系数的临界值, 同时得到了临界耦合系数与散射长度的关系. 关键词： 费米气体 自俘获 周期调制     

Sur un modèle markovien rudimentaire de diffusion atomique

We introduce and study an interacting particle system. The evolution is Markovian. The elementary step of the dynamics is the following: one point is randomly chosen in the ambient space, the nearest particle moves to that point. We investigate in particular equilibrium properties of the system. To cite this article: J.-B. Gouéré, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

An Asymptotic Analysis of a 2-D Model of Dynamically Active Compartments Coupled by Bulk Diffusion

A class of coupled cell–bulk ODE–PDE models is formulated and analyzed in a two-dimensional domain, which is relevant to studying quorum-sensing behavior on thin substrates. In this model, spatially segregated dynamically active signaling cells of a common small radius \(\epsilon \ll 1\) are coupled through a passive bulk diffusion field. For this coupled system, the method of matched asymptotic expansions is used to construct steady-state solutions and to formulate a spectral problem that characterizes the linear stability properties of the steady-state solutions, with the aim of predicting whether temporal oscillations can be triggered by the cell–bulk coupling. Phase diagrams in parameter space where such collective oscillations can occur, as obtained from our linear stability analysis, are illustrated for two specific choices of the intracellular kinetics. In the limit of very large bulk diffusion, it is shown that solutions to the ODE–PDE cell–bulk system can be approximated by a finite-dimensional dynamical system. This limiting system is studied both analytically, using a linear stability analysis and, globally, using numerical bifurcation software. For one illustrative example of the theory, it is shown that when the number of cells exceeds some critical number, i.e., when a quorum is attained, the passive bulk diffusion field can trigger oscillations through a Hopf bifurcation that would otherwise not occur without the coupling. Moreover, for two specific models for the intracellular dynamics, we show that there are rather wide regions in parameter space where these triggered oscillations are synchronous in nature. Unless the bulk diffusivity is asymptotically large, it is shown that a diffusion-sensing behavior is possible whereby more clustered spatial configurations of cells inside the domain lead to larger regions in parameter space where synchronous collective oscillations between the small cells can occur. Finally, the linear stability analysis for these cell–bulk models is shown to be qualitatively rather similar to the linear stability analysis of localized spot patterns for activator–inhibitor reaction–diffusion systems in the limit of long-range inhibition and short-range activation.     

基于CdTe量子点荧光猝灭-恢复方法测定依诺沙星的研究

水相合成了巯基丙酸保护的CdTe量子点。根据在Cu2+存在的情况下,CdTe量子点荧光恢复程度与依诺沙星浓度成正比的现象,建立了基于CdTe量子点荧光猝灭-恢复测定依诺沙星的新方法。考察了溶液pH值以及Cu2+浓度等对检测体系的影响。在p H=10的硼砂缓冲溶液中,在Cu2+浓度为2.3×10-5mol/L的条件下,依诺沙星浓度在8.0×10-7~3.0×10-5mol/L范围内与量子点荧光恢复程度呈良好的线性关系,检出限为7.2×10-8mol/L。该方法用于实际样品中依诺沙星的检测,回收率为95.5%~105.0%。     

Preparation of mannan modified anionic PCL-PEG-PCL nanoparticles at one-step for bFGF antigen delivery to improve humoral immunity

In this article, blank anionic poly(-caprolactone)-poly(ethylene glycol)-poly(-caprolactone) (PCEC) and anionic mannan modified PCEC (MPCEC) nanoparticles with nearly the same particle size and zeta potential were prepared by emulsion solvent evaporation method. Human basic fibroblast growth factor (bFGF) was absorbed onto anionic nanoparticles surface due to electrostatic interaction. The obtained bFGF-nanoparticles complexes were injected subcutaneously into C57BL/6 mice at 20 μg of bFGF/dose on week 0, 1, 2 and 3. The mice serum was collected on week 4, and bFGF-specific autoantibody total IgG, IgG1 and IgG2a titer in serum was determined by ELISA. The results indicated that the autoantibody IgG, IgG1 and IgG2a titer of the mice immunized by bFGF–MPCEC complexes were higher than that immunized by either bFGF–PCEC or bFGF–Alum. This phenomenon might be due to that mannan functionalized MPCEC nanoparticles could be targeted to dendritic cells (DCs) to improve humoral immunity. The prepared anionic mannan modified PCEC nanoparticles (MPCEC) might have great potential application in vaccine delivery systems.     

Flutelike porous hematite nanorods and branched nanostructures: synthesis, characterisation and application for gas-sensing

Flute-like porous alpha-Fe2O3 nanorods and branched nanostructures such as pentapods and hexapods were prepared through dehydration and recrystallisation of hydrothermally synthesised beta-FeOOH precursor. Transmission electron microscopy (TEM), high-resolution TEM and selected area electron diffraction analyses reveal that the nanorods, which grow along the [110] direction, have nearly hollow cavities and porous walls with a pore size of 20-50 nm. The hexapods have six symmetric arms with a diameter of 60-80 nm and length of 400-900 nm. The growth direction of the arms in the hexapod-like nanostructure is also along the [110] direction, and there is a dihedral angle of 69.5 degrees between adjacent arms. These unique iron oxide nanostructures offer the first opportunity to investigate their magnetic and gas sensing properties. The nanostructures exhibited unusual magnetic behaviour, with two different Morin temperatures under field-cooled and zero-field-cooled conditions, owing to their shape anisotropy and magnetocrystalline anisotropy. Furthermore, the alpha-Fe2O3 nanostructures show much better sensing performance towards ethanol than that of the previously reported polycrystalline nanotubes. In addition, the alpha-Fe2O3 nanostructure based sensor can selectively detect formaldehyde and acetic acid among other toxic, corrosive and irritant vapours at a low working temperature with rapid response, high sensitivity and good stability.