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201.
Nucleation underlies the dynamics of most first-order phase transitions in natural and man-made systems. However, most of the systems of interest are out of equilibrium. Little is known on the effect of nonequilibrium factors on the dynamics of nucleation. Here, we use the forward flux sampling method to investigate the effect of nonequilibrium diffusion on nucleation in small-world Ising networks, wherein spins can be exchanged between nearest-neighboring nodes. We introduce a parameter α to quantify the difference of nucleation rate with and without diffusion. We find that α shows a nonmonotonic dependence on the rewiring probability p of small-world networks. In particular, for different diffusion probability D, a crossover happens at p ≃ 0.17, below which the nucleation rate decreases as D increases, suggesting that the diffusion is against nucleation; while above which the nucleation rate increases with D, indicating that the diffusion is in favor of nucleation. By identifying the distinct features of nucleating clusters along the pathways for different randomness of networks, we reveal the underlying mechanism of such a nontrivial dependence. 相似文献
202.
The equation of state of a face-centered cubic phase has been quantitatively analyzed in terms of the statistical theory of
crystals. It has been shown that, for xenon at room temperature, the pressure equal to 1.5 GPa determines the instability
point where the condition of the positive bulk modulus of a face-centered cubic crystal is violated. A “universal line” bounding
the thermodynamic stability region of the face-centered cubic phase of van der Waals crystals has been constructed. An analysis
of the data available in the literature allows the conclusion that the revealed transition of face-centered cubic xenon to
the martensitic phase at a pressure of 1.5 GPa and a temperature of 300 K can be considered a manifestation of the predicted
instability. In this respect, it is important to perform detailed experiments on polymorphic transformations of real xenon
(and also krypton). Another aspect of the proposed theory is that it provides a means for quantitatively predicting the characteristics
of the so-called “cold” (at negative pressures) melting, which recently has become accessible for experimental observation. 相似文献
203.
《Journal of organometallic chemistry》2005,690(24-25):5973-5978
Application of the second generation Grubbs metathesis catalyst for the homo-cross-metathesis of acroyl amides from chiral amines is reported. This efficient and high-yielding reaction provides a side-product free synthesis of fumaric acid diamides which are formed with complete (E)-selectivity under the reaction conditions. In particular, products which cannot be synthesized from the corresponding fumaroyl chloride via classic condensation route can now be provided in excellent yields (88–98%) with a catalyst loading from 2.5 mol% to even 0.375 mol%. 相似文献
204.
The crystal CaCO3 with specific shapes was prepared by the biomimetic synthesis , using BSA as the matrix. The products were characterized by scanning electron microscopy (SEM), FTIR spectroscopy and TG. The results show that BSA have the effect on the shapes of CaCO3 in the crystallization process. The probable mechanism of the effect was discussed。 相似文献
205.
Microchimica Acta - A new Hg(II)-imprinted thiol-functionalized silica gel sorbent was synthesized by a surface imprinting technique for selective solid-phase extraction of Hg(II). Compared to a... 相似文献
206.
研究了具有变时滞的退化中立型微分系统的稳定性.利用退化时滞微分系统的变易公式和Gronwall-Bellman积分不等式给出了该系统的指数估计以及稳定和指数渐近稳定的充分条件. 相似文献
207.
In this paper, stability of time varying singular differential systems with delay is considered. Based on variation formula and Gronwall-Bellman integral inequality, we obtain the exponential estimation of the solution and the sufficient conditions under which the considered system is stable and exponentially asymptotically stable. These results will be very useful to further research on Roust stability and control design of uncertain singular control systems with delay. 相似文献
208.
209.
利用侧链带有羧基的官能化两亲性聚己内酯基共聚物Pluronic-b-poly(ε-caprolactone-co-6-carboxylic-ε- caprolactone) [Pluronic-b-P(CL-co-CCL), FC]为底物, 与紫杉醇(PTX)反应得到了一系列PTX的聚合物前药FCPTX. 通过核磁共振(1H NMR)和高效液相色谱(HPLC)表征了聚合物前药结构并分析了前药中的PTX接枝率. 通过聚合物前药胶束进一步物理包载PTX, 得到载有PTX的聚合物前药胶束PTX/FCPTX, 其载药量和包封率随着前药FCPTX中的PTX接枝率的增加而提高. 利用荧光光谱(FS)、透射电镜(TEM)和粒径分析仪(DLS)表征了胶束的临界胶束浓度(CMC), 形态和粒径. 体外细胞评价表明, 聚合物前药FCPTX具有较高的胞内累积量和良好的血液相容性、能有效降低紫杉醇的药物毒性. 作为一种优秀的药物载体, 聚合物前药FCPTX在联合化疗领域有着较大的应用潜力. 相似文献
210.
We study the fluctuation-activated transition process in a system of two coupled forced bistable oscillators with a mismatch σ in the force constants. As the coupling strength μ is increased, the transition pathway undergoes four stages changes from a two-step process with two candidate pathways to a mixture of a two-step pathway and a one-step pathway to a one-step process with also two candidate pathways and then to a one-step process with a single pathway.Interestingly, we find that the total transition rate depends nonmonotonically on σ in the weak coupling: a maximal rate appears in an intermediate magnitude of σ. Moreover, the rate also exhibits an unexpected maximum as a function ofμ. The results are in an excellent agreement with our numerical simulations by forward flux sampling. 相似文献