Synthesis and characterization of phase-pure manganese(II) and manganese(III) silicalite-2

Manganese silicalite-2 was synthesized at high pH using the molecular cluster Mn 12O 12(O 2CCH 3) 16 as a Mn source. The silicalite-2 (ZSM-11) materials were synthesized using 3,5-dimethyl- N, N-diethylpiperdinium hydroxide as a structure-directing agent to produce phase-pure ZSM-11 materials. No precipitation of manganese hydroxide was observed, and synthesis resulted in the incorporation of up to 2.5 mol % Mn into the silicalite-2 with direct substitution into the framework verified by the linear relationship between the unit cell volume and loading. The Mn is reduced to Mn (II) during hydrothermal synthesis and incorporated into the silicalite-2 framework during calcination at 500 degrees C. Further calcination at 750 degrees C does not affect the crystallinity but oxidizes essentially all of the Mn (II) to Mn (III) in the framework. The large difference in oxidation temperatures between the II and III oxidation states provides a means of producing relatively pure manganese(II) and manganese(III) silicalite-2 materials for applications such as catalysis.     

Convergence in p-mean for arrays of row-wise extended negatively dependent random variables

It is known that the maximal operator \({\sigma^{\kappa,*}(f)} := sup_{n \in \mathbf{P}}{|{\sigma}_{n}^{\kappa} (f)|}\) is bounded from the dyadic Hardy space \({H_{p}}\) into the space \({L_{p}}\) for \({p > 2/3}\) [6]. Moreover, Goginava and Nagy showed that \({\sigma^{\kappa,*}}\) is not bounded from the Hardy space \({H_{2/3}}\) to the space \({L_{2/3}}\) [9]. The main aim of this paper is to investigate the case \({0 < p < 2/3}\). We show that the weighted maximal operator \({\tilde{\sigma}^{\kappa,*,p}(f) :=sup_{n\in \mathbf{P}} \frac{|{\sigma}_{n}^\kappa (f)|}{n^{2/p-3}}}\), is bounded from the Hardy space \({H_{p}}\) into the space \({L_{p}}\) for any \({0 < p < 2/3}\). With its aid we provide a necessary and sufficient condition for the convergence of Walsh–Kaczmarz–Marcinkiewicz means in terms of modulus of continuity on the Hardy space \({H_p}\), and prove a strong convergence theorem for this means.     

天目山自然保护区常绿落叶阔叶林优势种群空间分布格局

基于浙江省天目山常绿阔叶林1 hm²样地调查数据,应用点格局方法分析了3种优势种细叶青冈(Cyclobalanopsis gracilis)、杉木(Cryptomeria fortunei)、短尾柯(Lithocarpus brevicaudatus)的空间分布格局,对比了优势种不同生长阶段(幼苗、幼树、中树、大树)的空间分布格局以及不同生长阶段之间的空间关联性.结果表明:(1)3个主要优势种并未受到明显的生境异质性的影响,总体呈现随机分布格局,其中短尾柯由于具有较高的根蘖率,导致在中树种群阶段于2~10 m处呈现聚集分布;(2)3个主要优势种在不同生长阶段之间1~25 m尺度范围内总体表现为无关联性,其中幼树与幼苗在小尺度(1~3 m)上均表现为正相关,细叶青冈中树与大树阶段之间存在潜在的负相关趋势,杉木幼树与大树阶段存在潜在的正相关趋势;(3)3个优势种群在发育过程中均未明显受到密度制约造成的自疏效应的影响.     

金属蒸气法制备聚合物固载Pd—Cu燃料电池电极

利用金属蒸气法制备了三种不同金属重量比的树脂固我及活性炭负载Pd－Cu双金属催化剂。透射电镜（TEM）和X射线衍射（XRD）测定结果表明催化剂中Pd—Cu已形成合金。合金粒度极小，平均直径小于5nm。树脂固载催化剂金属粒度远小于活性炭负载催化剂的金属粒度。X－射线光电子能谱（XPS）结果表示Pd和Cu均以零价态存在。极化曲线表明，树脂固载催化剂的电催化活性接近于相应的活性炭负载催化剂。     

Limiting behavior for arrays of row-wise upper extended negatively dependent random variables

Our aim is to obtain deterministic bounds for the row sum elements of a random triangular array introducing, thereunto, a dependence structure for triangular arrays of random variables which extend the concepts of upper and lower extended negatively dependence already known for random variables. Concretely, for triangular arrays \({\{X_{n,k}, 1 \leqq k \leqq n, n \geqq 1\}}\) of row-wise upper extended negatively dependent random variables with dominating sequence \({\{M_{n}, n \geqq 1\}}\) weakly mean dominated by a random variable X and sequences \({\{b_{n}\}}\) of positive constants, conditions are stated to ensure the deterministic boundedness of \({\Sigma^{n}_{k=1}(X_{n,k} - {\mathbb E}X_{n,k})/\sqrt{b_{n} {\rm Log} n}}\), where \({{\rm Log} n := {\rm log} {\rm max}\{n, e\}}\). In particular, a sufficient moment condition is given permitting us to achieve our goal under the rate of the so called “Law of the Logarithm”.     

c-Si与a-Si的竞争取决于材料费用

尽管c-Si和a-Si模块每瓦成本的计算方法并不完全一致,并且长期来看仍认为a-Si电池的成本会更低,但很明显到2013年,a-Si太阳能电池的市场份额仍不会超过20%。     

Metal site-mediated, thermally induced structural changes in Cr6+-silicalite-2 (MEL) molecular sieves

Cr(6+) ions were incorporated into the lattice sites of phase-pure silicalite-2 made using 3,5-dimethylpiperidinium as a structure-directing agent. The materials exhibited a remarkably well-resolved vibronic emission consisting of a high frequency progression of 987 cm(-1), which was assigned to the fundamental symmetric stretching mode of the (Si-O-)(2)Cr(═O)(2) group dominated by the terminal Cr═O stretch. A low frequency progression at 214 cm(-1), which was assigned to a symmetric O-Cr-O bending mode, was built on each band of the 987 cm(-1) progression. Studies of the vibronic structure of the emission spectrum as a function of temperature and Cr ion concentration reveal an abrupt change in the Franck-Condon factor of the emission at 20 K for samples with very low Cr concentrations (0.03 mol %). The change in the Franck-Condon factor is attributed to a temperature-induced structural change in the coordination sphere of the metal ion. This structural change was found to be accompanied by a concomitant structural change in the lattice structure of the silicalite-2. This structural change, as studied by temperature-dependent X-ray diffraction, did not involve a crystallographic phase change but an abrupt decrease in the unit cell volume, caused specifically by a decrease in the c-axis. This structural change was not observed in pure silicalite-2, indicating that it is not intrinsic to the silicalite lattice. Moreover, no similar structural change was observed at higher Cr loading (1 mol %). This suggests that the presence of the Cr ions and the changes in the coordination geometry they undergo at low temperature induced the observed contraction in the silicalite-2 lattice, in effect acting as a thermal switch that decreases the unit cell volume.     

Synthesis, characterization, and spectroscopic characteristics of chromium(6+) and -(4+) silicalite-2 (ZSM-11) materials

The systematic incorporation of Cr ions into a phase-pure silicalite-2 lattice was accomplished through hydrothermal synthesis using 3,5-dimethylpiperidinium as a templating agent. The Cr ions, after calcination to remove the template, were in the 6+ oxidation state, with their incorporation into the lattice verified by the systematic expansion of the unit cell as a function of Cr loading. The structures of these materials as revealed by electronic spectroscopy and X-ray absorption near-edge spectroscopy (XANES) were consistent with the dioxo structure typically exhibited by Cr(6+) in an amorphous silica matrix. These materials were highly luminescent, with the emission spectra showing an unusually well-resolved vibronic structure characteristic of an emissive site with little inhomogeneous broadening. The site was reduced under flowing CO to Cr(4+), as characterized by XANES. The reduction of Cr from 6+ to 4+ resulted in unit-cell volumes that are systematically smaller than those observed with Cr(6+), even though the ionic radius of Cr(4+) is larger. This is attributed to the fact that the Cr(6+) site is not a simple metal ion but a significantly larger [CrO(2)](2+) unit, requiring a larger lattice expansion to accommodate it. Through analysis of the XANES preedge and assignment of the ligand-field spectrum of the Cr(4+) ions, it is possible to establish isomorphic substitution into the silicalite lattice.     

Integer Powers of Anti-Bidiagonal Hankel Matrices

In this paper we derive a general expression for integer powers of real upper and lower anti-bidiagonal matrices with constant anti-diagonals using Chebyshev polynomials. An explicit formula for the inverse of these matrices is also provided.