Nanostructured Pt/GC model electrodes prepared by the deposition of metal-salt-loaded micelles

Novel, nanostructured, carbon-supported Pt model electrodes with homogeneously distributed Pt nanoparticles of uniform size were fabricated and analyzed with respect to their electrochemical properties. For this purpose, Pt-salt-loaded micelles were deposited on a glassy carbon substrate and subsequently exposed to an oxygen plasma and a H2 atmosphere for removal of the polymer carriers and reduction of the Pt salt. The morphology of the resulting nanoparticles and their electrochemical/electrocatalytic properties were characterized by high-resolution scanning electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and differential electrochemical mass spectrometry for CO electrooxidation. The data demonstrate that this method is generally suited to the production of nanostructured model electrodes with well-defined and independently adjustable particle size and interparticle distance distributions, which are specifically suited for quantitative studies of transport processes in electrocatalytic reactions.     

江西省社会发展评价指标体系的建构及对各地市的评价

本文介绍了由本省省情构建的一套江西省社会发展评价指标体系,并用系统工程和计算机技术对全省11地市1988至1990年三年间的社会发展进行综合评述。     

杂氮硅三环化合物(Ⅰ)和(Ⅱ)晶体结构的研究

杂氮硅三环化合物Ⅰ和的分子结构用直接法解,经全矩阵最小二乘修正,得到它们的晶体学参数。并对它们的结构进行了比较和讨论。     

系列双核Ln(III)配合物的晶体结构和磁性

合成了分子式为[Ln~2(phen)~2L],phen=C~1~2H~8N~2[ALn=Nd,L=(CH~3COO)~4(ONO~2)~2,BLn=Sm,L=(C~6H~5COO)~6,CLn=Eu,L=(C~6H~5COO)~6]3种同双核配合物。用X射线四圆衍射仪测定了3种化合物的结构。在化合物A分子中,2个Nd(III)原子由4个CH~3COO^-基团桥联,以phen和ONO~2^-为端基,构成了一个具有C~2对称性的双核分子。配合物B和C具有完全相同的结构,它们是以4个苯甲酸根为桥,2个phen和2个C~6H~5COO^-为端基的中心对称双核分子,其中6个苯甲酸根的成键状态可分为3种状况。在3种化合物中,每个Ln均为9配位,呈不规则多面体。Ln-Ln距离,A为0.397nm,B和C均为0.405nm。测定了各配合物的变温磁化率,通过对磁性质研究,发现化合物A在低温下具有反铁磁物质行为,并由理论拟合,求得了磁参数g,J值。     

Theoretical estimates of the IR spectrum of water intercalated into kaolinite

Calculations at AM1, PM3, and HF/6‐31G levels of part of the IR spectrum of the water–kaolinite intercalated system based on a 96‐atom cluster of kaolinite with one water molecule are reported. Only the water molecule conformation is optimized. Frequencies and intensities for just the water vibrations and stretchings of four cluster hydroxyls were calculated through partial Hessian matrices and polar tensors obtained by numerical differentiation of energy gradients and dipole moment. The water molecule was found to attach to the cluster mainly through a double hydrogen bond to the siloxane inner surface, partially entering the siloxane ring hexagonal hole. Though the theoretical results predict that the water OH stretching frequencies decrease from the gas‐phase state to the intercalated state, they are still higher than expected with respect to the observed spectrum. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers

Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases shows that they enable convergence toward solutions that are unstable to stationary and oscillatory disturbances, with either a single or multiple frequency content. Finally, comparisons with SFD are also performed, showing significant reduction in computer cost for complex flows by using the implicit multi-step MGM schemes.     

Organocatalysis of CN/CN and CC/CN Exchange in Dynamic Covalent Chemistry

The reversibly formed C?N bond plays a very important role in dynamic covalent chemistry and the C?N/C?N exchange of components between different imine constituents to create dynamic covalent libraries has been extensively used. To facilitate diversity generation, we have investigated an organocatalyzed approach, using L ‐proline as catalyst, to accelerate the formation of dynamic libraries of [n×n] imine components. The organocatalysis methodology has also been extended, under somewhat modified conditions, to reversible C?C/C?N exchange processes between Knoevenagel derivatives of barbituric acid and imines, allowing for the generation of increased diversity.     

吸附固定相电色谱和动态改性电色谱的手性分离

对动态改性电色谱手性分离进行了研究。电色谱柱填充强阴离子交换固定相（SAX0,添加在流动相中的磺化β－环糊精（S－CD）动态地吸陵于SAX填料表面,形成一层准手性固定相。色氨酸、阿托品和异博定对映体在本体系获得了很好的分离,它们的分离分别为2．06,10．1和1．96,对映体峰的柱效价于85,000塔板数／米和412,000塔板数／米之间。连续运行17次,死时间和色氨酸对映体的电色谱保留因子的相对标准偏差分别为0．53％,0．62％和0．69％。此外,以吸附于SAX填料的牛血清白蛋白和S－CD为手性固定相进行了电色谱手性分离的研究。在这两种体系下分离色氨酸对映体的分离度分别为3．86和2．97。吸附S－CD柱电色谱和动态改性电谱的重现性进行子比较,发现动态改性电色谱有更好的重现性。