The state of palladium in the system potassium palladium-11-tungstosilicate on aluminosilicate as studied by DRIFT spectroscopy

The influence of redox treatments on the state of palladium in the heteropoly acid K₆[SiW₁₁PdO₃₉] supported on amorphous aluminosilicate was studied by diffuse-reflectance IR spectroscopy using CO as a probe molecule. A bulk sample of the K₆[SiW₁₁PdO₃₉]·11H₂O heteropoly compound (HPC) was studied for comparison. The deposition of the bulk sample on aluminosilicate leads to the partial decomposition of Keggin structure and to the removal of palladium cations from the HPC framework. The metal introduced into the K₆[SiW₁₁PdO₃₉]/SiO₂-Al₂O₃ system within HPC displays higher thermal stability in redox cycles compared to that of the bulk HPC. A highly dispersed state of palladium persists up to 573 K.     

三组分一锅法合成1-羧甲基-6-芳基-1,2,3,4,5,6-六氢茚并[2,3-b]-喹啉-5,11-二酮

以芳醛、1,3-茚二酮、烯胺酮为原料, 冰醋酸为溶剂, 三组分一锅法合成了一系列茚并[2,3-b]喹啉类化合物. 该反应产率高(83%～93%)、操作简单、后处理方便. 产物的结构通过红外光谱、核磁共振谱和元素分析证实, 同时给出了该反应可能的反应机理.     

Peculiarities in the Raman spectra of ZrB12 and LuB12 single crystals

We have measured Raman spectra of high-quality Zr^natB₁₂, Lu^natB₁₂ and Lu¹¹B₁₂ single crystals with high resolution, and the observed strong peaks are attributed to specific vibration modes. Besides, there are a number of additional Raman peaks in spectral ranges, where only Raman-inactive vibrations of the atomic arrangement are expected. Accordingly, it is assumed, that the investigated crystals contain intrinsic structural imperfections or distortions in sufficient concentration and efficiency to initiate the observed breaking of phonon selection rules. We suppose boron vacancies, boron isotope effects and displacements of the metal atoms to be reasons for such imperfections.     

Studies directed towards the total synthesis of anthracycline antibiotics

At present anthracycline antibiotics have proven to be the most exciting agents in cancer chemotherapy. Both adriamycin and daunomycin are proven to be effective against a variety of human tumour cells, despite their cardiotoxicity. However, some synthetic analogues, such as 4-demethoxydaunomycin, are shown to be better therapeutic ratios compared to adriamycin or daunomycin. Various approaches have been successfully made for the total synthesis of (±) 4-demethoxydaunomycinone, the aglycone of (±) 4=demethoxydaunomycin, starting from benzoquinone, napthalene or anthraquinone precursors. Finally an elegant approach for the stereoconvergent synthesis of (+) 4-demethoxydaunomycinone has been worked out. New methods involving both Diels-Alder and Friedal-Crafts acylation, have been developed for the total synthesis of daunomycinone and 11-deoxydaunomycinone. The synthesis of L-daunosamine, the amino sugar unit present in the antitumor anthracyclines has been successfully elaborated starting either from D-glucose or D-glucosamine.     

稀土对SAPO-11分子筛结构与性能的影响

分别采用浸渍法及离子交换法将稀土元素镧、铈引入SAPO-11分子筛, 通过XRD、BET、孔分布、in-situ FTIR及NH3-TPD等表征手段考察了稀土对SAPO-11分子筛结构及表面性能的影响. 结果表明, SAPO-11分子筛经稀土元素La、Ce改性后, 分子筛摩尔组成改变、结晶度下降, 其中La3+离子交换改性带来的变化最为明显. 在分子筛表面聚集的稀土元素可作为Lewis酸中心, 造成分子筛L酸含量增多, B/L比值下降；同时, 由于三价稀土离子吸引电子的能力弱于Al3+, 改性后催化剂的桥连羟基强度下降. 经稀土改性后, 催化剂总酸量下降.     

Viability of Bacteria in Hybrid Aqueous Silica Gels

Whole E. coli bacteria have been trapped within silica gels obtained via the acidification of sodium silicate and silica nanoparticles solutions. Their -galactosidase enzymatic activity increases with time, suggesting that their membrane is partially lysed during the encapsulation process. Such a lysis can be greatly reduced when encapsulation is performed in the presence of gelatin. The biocatalytic activity of trapped bacteria remains almost constant for more than a week. Moreover bacteria trapped in such gels remain able to incorporate glucose, showing that their viability has been preserved.     

Eulerian numbers with fractional order parameters

Summary The aim of this paper is to generalize the well-known Eulerian numbers, defined by the recursion relationE(n, k) = (k + 1)E(n – 1, k) + (n – k)E(n – 1, k – 1), to the case thatn is replaced by . It is shown that these Eulerian functionsE(, k), which can also be defined in terms of a generating function, can be represented as a certain sum, as a determinant, or as a fractional Weyl integral. TheE(, k) satisfy recursion formulae, they are monotone ink and, as functions of , are arbitrarily often differentiable. Further, connections with the fractional Stirling numbers of second kind, theS(, k), > 0, introduced by the authors (1989), are discussed. Finally, a certain counterpart of the famous Worpitzky formula is given; it is essentially an approximation ofx in terms of a sum involving theE(, k) and a hypergeometric function.Dedicated to the memory of Alexander M. Ostrowski on the occasion of the 100th anniversary of his birth.     

Asymptotic behavior of some power series with ζ-functions in the coefficients

The asymptotic behaviors of four closely related special cases of power series with -functions in the coefficients have appeared in the literature. A function which involves a real parameter is introduced; the parameter can be specialized to produce all of these special cases. The asymptotic behavior is obtained for this function for all real values of the parameter.     

An application of an optimal behaviour of the greedy solution in number theory

Leta ₁,a ₂, ...,a _n be relative prime positive integers. The Frobenius problem is to determine the greatest integer not belonging to the set { _j=1 ⁿ a _j x _j :xZ ₊ ⁿ }. The Frobenius problem belongs to the combinatorial number theory, which is very rich in methods. In this paper the Frobenius problem is handled by integer programming which is a new tool in this field. Some new upper bounds and exact solutions of subproblems are provided. A lot of earlier results obtained with very different methods can be discussed in a unified way.