Synergistic Effect of Oxalate and Ethylene Glycol on the Formation of SnO2 Rods

SnO₂ rods have been synthesized by using tin (II) chain‐like complexes as precursors in which oxalate and ethylene glycol act as co‐ligands. On the basis of experimental analysis, a reasonable formation mechanism of rods is discussed, which is further supported by Fourier transform infrared spectroscopy (FT‐IR). These results show that the synergistic effect of oxalate group and ethylene glycol plays an important role in the formation of long SnO₂ rods.     

Aligned and molecularly oriented semihollow ultrafine polymer fiber yarns by a facile method

In this work, aligned and molecularly oriented bone‐like PLLA semihollow fiber yarns were manufactured continuously from an optimized homogeneous polymer‐solvent‐nonsolvent system [PLLA, CH₂Cl₂, and dimethyl formamide (DMF)] by a single capillary electrospinning via self‐bundling technique. Here, it should be emphasized that the self‐bundling electrospinning technique, a very facile electrospinning technique with a grounded needle (which is to induce the self‐bundling of polymer nanofibers at the beginning of electrospinning process), is used for the alignment and molecular orientation of the polymer fiber, and the take‐up speed of the rotating drum for the electrospun fiber yarn collection is very low (0.5 m/s). PLLA can be dissolved in DMF and CH₂Cl₂ mixed solvent with different ratios. By varying the ratios of mixed solvent system, PLLA electrospun semihollow fiber with the porous inner structure and compact shell wall could be formed, the thickness of the shell and the size of inner pores could be adjusted. The results of polarized FTIR and wide angle X‐ray diffraction investigations verified that as‐prepared PLLA semihollow fiber yarns were well‐aligned and molecularly oriented. Both the formation mechanism of semihollow fibers with core‐shell structure and the orientation mechanism of polymer chains within the polymer fibers were all discussed. The as‐prepared self‐bundling electrospun PLLA fiber yarns possessed enhanced mechanical performance compared with the corresponding conventional electrospun PLLA fibrous nonwoven membranes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1118–1125, 2010     

Synthesis and thermoreversible gelation of dendron‐like polypeptide/linear poly(ε‐caprolactone)/dendron‐like polypeptide triblock copolymers

Dendron‐like poly(γ‐benzyl‐L ‐glutamate)/linear poly(ε‐caprolactone)/dendron‐like poly(γ‐benzyl‐L ‐glutamate) triblock copolymers having 2^{m + 1} PBLG branches (denoted as PBLG‐Dm‐PCL‐Dm‐PBLG, m = 0, 1, 2, and 3) were for the first time synthesized by utilizing ring‐opening polymerization (ROP) and click chemistry. The bifunctional azide‐terminated PCL (N₃‐PCL‐N₃) was click conjugated with propargyl focal point PAMAM‐typed dendrons Dm to generate Dm‐PCL‐Dm, which was then used as macroinitiator for the ROP of BLG‐NCA monomer to produce the targeted PBLG‐Dm‐PCL‐Dm‐PBLG triblock copolymers. Their molecular structures and physical properties were characterized in detail by FTIR, NMR, gel permeation chromatography, differential scanning calorimetry, and wide angle X‐ray diffraction (WAXD). The crystallinity of the central PCL segment within these copolymers is increasingly suppressed by the flanking PBLG wedges, whereas the PBLG segments gradually changed from a β‐sheet conformation to an α‐helix conformation with the increasing PBLG branches. These triblock copolymers formed thermoreversible organogels in toluene, and the dendritic topology of PBLG wedges controlled their critical gelation concentrations. The self‐assembled structure of organogels was further characterized by means of transmission electron microscopy, WAXD, and small‐angle X‐ray scattering. The fibers with flat ribbon morphology were clearly shown, and the gelation occurred through a self‐assembled nanoribbon mechanism. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 709–718, 2010     

A note on static spaces and related problems

In this paper we study static spaces introduced in Hawking and Ellis (1975)  [1], Fischer and Marsden (1975) [3] and Riemannian manifolds possessing solutions to the critical point equation introduced in Besse (1987)  [11], Hwang (2000)  [12]. In both cases, on the manifolds there is a function satisfying a particular Ricci–Hessian type equation (1.6). With an idea similar to that used in Cao et al. (2012)  [15], [16], we have made progress in solving the problem raised in Fischer and Marsden (1975)  [3] of classifying vacuum static spaces and in proving the conjecture proposed in Besse (1987)  [11] concerning manifolds admitting solutions to the critical point equation in general dimensions. We obtain even stronger results in dimension 3.     

Local convergence results of Gauss-Newton's like method in weak conditions

In this paper, we study the convergence of Gauss-Newton's like method for nonlinear least squares problems. Under the hypothesis that derivative satisfies some kind of weak Lipschitz condition, we obtain the sharp estimates of the radii of convergence ball of Gauss-Newton's like method and the uniqueness ball of the solution.     

Strings and branes under microscope

It is shown that in the standard vacuum 5D Kaluza‐Klein gravity there exist wormhole‐like solutions which look like strings attached to two D‐branes. The asymptotic behaviour of the corresponding metric is investigated.     

二维Finsler空间是共形平坦的若干判定条件

本文利用Finsler约度量函数与度量张量获得了二维Finsler空间是共形平坦的若干令新的充要条件．此外，还推导了在共形映射下，局部Minkowski空间、常曲率Finsler空间与零曲率Finsler空间保持不变的新的充要条件．     

局部对称共形平坦黎曼流形中紧致极小子流形的一个刚性定理

本文研究局部对称共形平坦黎曼流形中紧致极小子流形,得到了这类子流形第二基本形式模长平方关于外围空间Ricci曲率的—个拼挤定理,推广了文[1]中的结果.     

关于CPn中共圆平坦全实极小子流形的一点注记

Let M be a concircularly flat totally real minimal submanifold in CP~4. The infimum V_m of the volume V(M) of M is obtained, also the necessary and sufficient conditions of "V(M)=V_m" is given.     

混合结构的闭环光纤陀螺研究

提出并研制了混合结构的闭环光纤陀螺系统。详细分析了该系统的结构特点、信号检测方法以及反馈信号对系统的影响。该系统具有低损耗、长期低漂移特性。实现了３００ｄｅｇ．／ｓ的动态范围及小于３００×１０－６的线性误差。