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21.
A key challenge in predicting the multiphase chemistry of aerosols and droplets is connecting reaction probabilities, observed in an experiment, with the kinetics of individual elementary steps that control the chemistry that occurs across a gas/liquid interface. Here we report evidence that oxygenated molecules accelerate the heterogeneous reaction rate of chlorine gas with an alkene (squalene, Sqe) in submicron droplets. The effective reaction probability for Sqe is sensitive to both the aerosol composition and gas phase environment. In binary aerosol mixtures with 2-decyl-1-tetradecanol, linoleic acid and oleic acid, Sqe reacts 12–23× more rapidly than in a pure aerosol. In contrast, the reactivity of Sqe is diminished by 3× when mixed with an alkane. Additionally, small oxygenated molecules in the gas phase (water, ethanol, acetone, and acetic acid) accelerate (up to 10×) the heterogeneous chlorination rate of Sqe. The overall reaction mechanism is not altered by the presence of these aerosol and gas phase additives, suggesting instead that they act as catalysts. Since the largest rate acceleration occurs in the presence of oxygenated molecules, we conclude that halogen bonding enhances reactivity by slowing the desorption kinetics of Cl2 at the interface, in a way that is analogous to decreasing temperature. These results highlight the importance of relatively weak interactions in controlling the speed of multiphase reactions important for atmospheric and indoor environments.The heterogeneous chlorination rate of an alkene is unexpectedly accelerated in the presence of spectator molecules containing oxygenated functional groups, which suggests weak halogen bonds can catalyze reactions at liquid surfaces. 相似文献
22.
Embedding flows are used to obtain a rigidity result on strongly topological conjugacy of families of diffeomorphisms, i.e. families of Cr(2?r?∞) diffeomorphisms, the strongly topologically conjugating homeomorphisms near degenerate saddle-nodes will be differentiable on center manifolds of the saddle-nodes. 相似文献
23.
本文分析了象差函数对光学传递函数的性态影响,指出在用白光主观散斑法测量曲面变形时,由于成象系统不能对曲面上各点同时对焦,各物点有不同程度的离焦,而造成光学传递函数对频率响应的下降,有效截止频率的降低,从而影响其测量灵敏度的提高。 相似文献
24.
Jinzhi?LeiEmail author Pedro?J.?Torres Meirong?Zhang 《Journal of Dynamics and Differential Equations》2005,17(1):21-50
In this paper, we will give, for the periodic solution of the scalar Newtonian equation, some twist criteria which can deal with the fourth order resonant case. These are established by developing some new estimates for the periodic solution of the Ermakov–Pinney equation, for which the associated Hill equation may across the fourth order resonances. As a concrete example, the least amplitude periodic solution of the forced pendulum is proved to be twist even when the frequency acroses the fourth order resonances. This improves the results in Lei et al. (2003). Twist character of the least amplitude periodic solution of the forced pendulm. SIAM J. Math. Anal. 35, 844–867.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday. 相似文献
25.
Li Y Zhao M Wang J Liu K Cai C 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4848-4856
We have developed a general method combining photochemical grafting and copper-catalyzed click chemistry for biofunctionalization of titanium substrates. The UV-activated grafting of an α,ω-alkenyne onto TiO(2)/Ti substrates provided a "clickable" thin film platform. The selective attachment of the vinyl end of the molecule to the surface was achieved by masking the alkynyl end with a trimethylgermanyl (TMG) protecting group. Subsequently, various oligo(ethylene glycol) (OEG) derivatives terminated with an azido group were attached to the TMG-alkynyl modified titanium surface via a one-pot deprotection/click reaction. The films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, ellipsometry, and atomic force microscopy (AFM). We showed that the titanium surface presenting click-immobilized OEG substantially suppressed the nonspecific attachment of protein and cells as compared to the unmodified titanium substrate. Furthermore, glycine-arginine-glycine-aspartate (GRGD), a cell adhesion peptide, was coimmobilized with OEG on the platform. We demonstrated that the resultant GRGD-presenting thin film on Ti substrates can promote the specific adhesion and spreading of AsPC-1 cells. 相似文献
26.
A new method based on matrix solid phase dispersion-capillary electrophoresis with electrochemiluminescence detection (MSPD-CE-ECL) has been developed for the simultaneous determination of three kinds of phenylurea herbicides (PHUs). Poly-β-cyclodextrin (poly-β-CD) was used as an additive in the running buffer to improve the separation of three analytes. The conditions for CE separation, ECL detection and effect of poly-β-CD were investigated in detail. Under the optimal conditions, three kinds of herbicides (isoproturon, linuron and diuron) were well separated and detected within 8 min. The linear ranges of the standard solution for isoproturon and linuron were 1-300 μg L(-1) with a detection limit (S/N=3) of 0.1 μg L(-1), and for diuron was 2-500 μg L(-1) with a detection limit of 0.2 μg L(-1). The average recoveries were in the range of 86.9-102.8%, and all relative standard deviation of the migration time and the ECL intensity in intraday and interday were less than 9.0%. The proposed method was also applied to the determination of three kinds of herbicides in green vegetable and rice samples with recoveries in the range from 78.1 to 93.8%. 相似文献
27.
Yu M Ding Z Jiang F Ding X Sun J Chen S Lv G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,83(1):453-460
The interaction between bovine serum albumin (BSA) and pegylated puerarin (Pur) in aqueous solution was investigated by UV-Vis spectroscopy, fluorescence spectroscopy and circular dichroism spectra (CD), as well as dynamic light scattering (DLS). The fluorescence of BSA was strongly quenched by the binding of pegylated Pur to BSA. The binding constants and the number of binding sites of mPEG(5000)-Pur with BSA were 2.67±0.12 and 1.37±0.05 folds larger after pegylating, which were calculated from the data obtained from fluorescence quenching experiments. The enthalpy change (ΔH) and entropy change (ΔS) were calculated to be 4.09 kJ mol(-1) and 20.01 J mol(-1) K(-1), respectively, according to Van't Hoff equation, indicating that the hydrophobic force plays a main role in the binding interaction between pegylated Pur and BSA. In addition, the negative sign for Gibbs free energy change (ΔG) implies that the interaction process is spontaneous. Moreover, the results of synchronous fluorescence and CD spectra demonstrated that the microenvironment and the secondary conformation of BSA were changed. Comparing with Pur, all our data collected indicated that pegylated Pur interacted with BSA in the same way as that of Pur, but docked into the hydrophobic pocket of BSA with more accessibility and stronger binding force. DLS measurements showed monomethoxy polyethylene glycol (mPEG) have an effect on BSA conformation, and revealed that changes in BSA size might be due to increases in binding constant and the absolute values of ΔG after Pur pegylation. 相似文献
28.
测量了间位甲苯酚和甲酚异构体混合物能量在35180-36002cm^-1范围的双光子共振四光子电离谱。对第一电子激发态振动带做了分析和归属,并对苯分子的不同取代对振动模的影响做了比较和分析。 相似文献
29.
本文报道了测量多光子电离谱的一整套硬件和软件系统。自行设计实现了将计算机、激光器及Boxcar连接起来的自动控制系统。这一系统大大改善了实验条件,提高了信噪比及仪器的分辨率。所得的实验结果,未曾见报道。 相似文献
30.
In this paper, we will give some optimal estimates on the rotation number of the linear equation
and that of the asymmetric equation:
where p(t) and q(t) are almost periodic functions and
These estimates are obtained by introducing some kind of new norms in the spaces of almost periodic functions.
Supported by the National Natural Science Foundation of China (no. 10325102), TRAPOYT-M.O.E. of China (2001), and the National
973 Project of China (no. G1999075108).
Received: April 6, 2004; revised: July 7, 2004 相似文献