A coordination polymer of CdCl2 with the novel zwitterionic dicarboxylate ligand 2,2′‐(2‐methylbenzimidazolium‐1,3‐diyl)diacetate (pda)

The title compound, poly[chlorido[μ₄‐2,2′‐(2‐methylbenzimidazolium‐1,3‐diyl)diacetato]cadmium(II)], [Cd(C₁₂H₁₁N₂O₄)Cl]_n, is an undulating two‐dimensional polymer consisting of a paddlewheel Cd₂(CO₂)₄ cluster which lies on an inversion centre. These paddlewheel clusters act as four‐connected square building units interlinked via bridging zwitterionic dicarboxylate ligands into a corrugated layer which is consolidated by π–π interactions between benzene rings of benzimidazole groups. Neighbouring layers are further assembled via interlayer π–π interactions into a three‐dimensional supramolecular structure. The key feature of this study is the synthesis of a paddlewheel‐based polymer constructed with a novel multifunctional zwitterionic dicarboxylate ligand.     

1,3-Sulfinate Migration Triggered by α-Imino Carbene and Divergent Zwitterion Cyclization: Synthesis of Cyclopropane,Dihydropyrrole, and Azepane Ring Systems

Cyclopropane, dihydropyrrole, and azepane ring systems were synthesized conveniently from sulfinate-tethered triazoles. The divergent synthetic strategy started with the unique 1,3-sulfinate migration of an α-imino carbene. The efficient reaction allowed control of the zwitterion bearing multiple reactive sites depending on the increased stability of the resulting carbocation and anion. The sulfinate was converted to a sulfone after the group migration, and a stable anion bearing two electron-withdrawing groups was thus formed. Catalytic amounts of iodide acted as a switch for the synthesis of cyclopropanes and dihydropyrroles. The reaction merits including readily available substrates, mild reaction conditions, and excellent functional group compatibility qualified this protocol a possible synthetic tool for cyclic compounds, especially for N-heterocycles.     

On the hybrid finite difference scheme for a singularly perturbed Riccati equation

In this paper a singularly perturbed Riccati equation is considered. The problem is solved by using a hybrid finite difference method on a Shishkin mesh. The method is composed of the midpoint upwind scheme and the backward Euler scheme based on the relation between the local mesh width and the perturbation parameter. It is proved that the scheme is almost second-order convergent, in the global maximum norm, independently of the singular perturbation parameter. Numerical experiments support the theoretical results.     

Existence of Matrix-Valued Multiresolution Analysis-Based Matrix-Valued Tight Wavelet Frames

In this article, we introduce and study the matrix-valued tight wavelet frames for analyzing matrix-valued signal based on matrix-valued multiresolution analysis (MMRA). We put our emphasis on the existence of the MMRA-based matrix-valued tight wavelet frames by establishing the correspondence with their the unitary extension principle (UEP). Here in particular we introduce the square brackets product and the quasi-interpolatory operator, which makes the certificating process for UEP become relatively simple. Some interesting byproducts, such as features on the quasi-interpolatory operator 𝒫_n in the matrix-valued function space case, are the critical foundation for our main work.     

圆锥形血管中的振荡发展流动

本文在小锥度角的假设下,研究了圆锥形血管的非定常振荡的发展流动问题.导得了相应的速度分布公式.分析表明,所有收缩的圆锥形血管的流动都是发展流动,而且锥度角对发展流动的影响随着锥度角的增大而增大.     

Developing flows and developed flows

This paper puts emphasis on the problem of the developing flows in the circular tube under oscillatory conditions. According to the Navier-Stokes' equations and using the method of Bessel function of imaginary argument, a system of formulas is obtained. Comparing the formulas obtained in this paper with Atabek's formulas, it may be seen that the former is simpler and more convenient. When both the formulas obtained in this paper and Atabek's formulas are reduced to the representation of developed flows, both of them are consistent. Numerical calculation results show that the computed results obtained in this paper are rather consistent with both Atabek's computed results and the experimental results.     

First Total Synthesis of (±)-13-Hydroxyneocembrene

First total synthesis of (±)-13-hydroxyneocembrene ( 1 ), starting from 6-methyl-5-hepten-2-one ( 6 ) and geraniol ( 7 ), is described. The key steps are (i) the addition of sulfur-stabilized carbanion 12 to aldehyde 9 , (ii) the synthesis of 18 by using phase-transfer catalyzed coupling reaction, and (iii) low-valent titanium-induced intramolecular coupling of oxo aldehyde 3 to afford the target molecule after the final deprotection.     

一类实奇芽等价的充要条件

给定一自反的Ｂａｎａｃｈ空间Ｘ．在ｃ^∞函数芽环∈（Ｘ）中,任何在原点Ｏ∈Ｘ的实奇芽ｆ,若其二阶Ｆｒｅｃｈｅｔ导数ｆ″（０）＝Ｔ是一个Ｆｒｅｄｈｏｌｍ算子,则它同构于形如：1/2+g(v)的一个芽．如果代替ｇ以一个与之同构的芽ｇ_１,显然得到一个与原来的芽同构的芽．然而,其逆是否真呢？本文将证明其逆命题亦真     

Investigating particle and volatile evolution during pulverized coal combustion using high-speed digital in-line holography

Devolatilization is an important process in pulverized coal combustion because it affects the ignition, volatile combustion, and subsequent char burning and ash formation. In this study, high-speed digital in-line holography is employed to visualize and quantify the particle and volatile evolution during pulverized coal combustion. China Shanxi bituminous coal particles sieved in the range of 105–154 µm are entrained into a flat flame burner through a central tube for the study. Time-resolved observations show the volatile ejection, accumulation, and detachment in the early stage of coal combustion. Three-dimensional imaging and automatic particle extraction algorithm allow for the size and velocity statistics of the particle and stringy volatile tail. The results demonstrate the smaller particle generation and coal particle swelling in the devolatilization. It is found that the coal particles and volatiles accelerate due to the thermal buoyancy and the volatiles move faster than the coal particles. On average, smaller particles move faster than the larger ones while some can move much slower possibly because of the fragmentation.     

四种藏药成方制剂中铅、砷含量的湿法消化-流动注射氢化物发生-原子吸收光谱法测定研究

选择藏族地区常用的四种藏药成方制剂安置精华散、当佐、仁青常觉和七十味珍珠丸作为研究对象,通过优化消化条件和测定条件,探索建立其铅、砷含量测定的湿法消化与流动注射氢化物发生-原子吸收光谱(FI-HAAS)联用分析方法,并对其铅砷含量进行精确测定。在优化的工作条件下,铅和砷的检出限分别为：0.067和0.012 μg·mL-1;定量限分别为：0.22和0.041 μg·mL-1;线性范围分别为：25～1 600 ng·mL-1(r=0.999 5),12.5～800 ng·mL-1(r=0.999 4);精密度(RSD)分别为：2.0%和3.2%;加标回收率范围分别为：98.00%～99.98%和96.67%～99.87%。四种藏药成方制剂的铅、砷含量测定结果如下,安置精华散中铅砷含量分别为：0.63～0.67和0.32～0.33 μg·g-1;当佐为：42.92～43.36和24.67～25.87 μg·g-1;仁青常觉为：1 611.39～1 631.36和926.76～956.52 μg·g-1;七十味珍珠丸为：1 102.28～1 119.27和509.96～516.87 μg·g-1。本研究建立了藏药成方制剂中铅、砷检测方法,并测定了四种藏药成方制剂中铅、砷含量,为其在临床安全有效使用提供了参考依据。