Investigations on the growth,optical behaviour and factor group of an NLO crystal: L‐alanine alaninium nitrate

Amino acid family crystals exhibit excellent nonlinear and electro‐optical properties. L‐alanine alaninium nitrate (LAAN) single crystal belonging to the amino acid group was grown by slow cooling solution growth technique. The High resolution X‐ray diffraction (HRXRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV‐Vis., Photoluminescence (PL) and Factor group analyses were carried out. The factor group analysis reveals 183 internal vibrations for the title compound. The second harmonic generation property was tested by Kurtz‐Perry powder technique. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solution growth of new ferroelectric glycine phosphite unidirectional single crystals at room temperature

Glycine phosphite [NH₃CH₂COOH₃PO₃], abbreviated as GPI is the second hydrogen bonded ferroelectric crystal combination of phosphorous acid and amino acid following βnine phosphite crystals abbreviated as BPI. Sankaranarayanan and Ramasamy‐Technique was adopted to prepare the ferroelectric glycine phosphite unidirectional single crystal. The growth orientation was imposed by the pre‐grown 〈010〉 seed. As water was the solvent, transparent, colourless crystal with cylindrical shaped ingot of sized 20mm‐diameter was grown. Powder X‐ray diffraction, HRXRD, FTIR, dielectric and mechanical studies were carried out. The results are discussed in detail. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of Poly(methyl methacrylate) Nanoparticles Initiated by 2,2′‐Azoisobutyronitrile via Differential Microemulsion Polymerization

The synthesis of nanosized poly(methyl methacrylate) initiated by 2,2′‐azoisobutyronitrile via differential microemulsion polymerization has been investigated. Poly(methyl methacrylate) with a molecular weight of around 1 × 10⁶ and a particle size of about 20 nm was achieved under mild reaction conditions. A typical condition was that the surfactant amount required could be as low as 1/130 of the monomer amount in weight, and the surfactant/water ratio could be as low as 1/600, which is much less than the corresponding amounts reported in the literature. “Molecular bricks”, i.e., nanoparticles in which there are only one or two polymer chains, can be achieved using mild conditions by differential microemulsion polymerization, which may have potential applications for making molecular devices.

     

Complex Macromolecular Architectures by Reversible Addition Fragmentation Chain Transfer Chemistry: Theory and Practice

Reversible addition–fragmentation chain transfer (RAFT) chemistry can be effectively employed to construct macromolecular architectures of varying topologies. The present article explores the principle design routes to star, block, and comb polymers in the context of theoretical design criteria for the so‐called Z‐ and R‐group approaches. The specific advantages and disadvantages of each approach are underpinned by selected examples generated in the CAMD laboratories. In particular, we demonstrate how the modeling of full molecular weight distributions can be employed to guide the synthetic effort. We further explore the theory and practice of generating amphiphilic block copolymer structures and their self‐assembly. In addition, the article foreshadows how modern synthetic techniques that combine RAFT chemistry with highly orthogonal click chemistry can be employed as a powerful tool that furthers the enhancement of macromolecular design possibilities to generate block (star) copolymers of monomers with extremely disparate reactivities. Finally, the ability of RAFT chemistry to modify the surface of well‐defined nano‐ and microspheres as devices in biomedical application is detailed.

     

Process Intensification of Emulsion Polymerization in the Continuous Taylor Reactor

Summary: Process intensification is investigated by the emulsion polymerization of styrene in the continuous Taylor reactor. The result is an increase in space time yield up to a factor 200 in comparison to a semi-batch polymerization process. This is obtained by a fast emulsion polymerization with a mean residence time, which is reduced to 60 seconds. The article presented the results of the process and the economical aspects of the Taylor reactor plant.     

Microwave Assisted Graft Copolymerization of N-Isopropyl Acrylamide and Methyl Acrylate on Cellulose: Solid State NMR Analysis and CaCO3 Crystallization

Summary: Graft copolymerization of N-isopropyl acrylamide and methyl acrylate on α-cellulose was carried out under microwave irradiation at specific cut off temperatures with cerium (IV) ammonium nitrate and potassium persulfate (KPS) as the initiating system. The role of KPS was to oxidize Ce (III) to Ce (IV) which is the active species in radical formation. The reactions at a temperature cut off of 60 °C were confirmed by ¹³C nuclear magnetic resonance cross-polarization with magic- angle spinning (¹³C NMR CP/MAS) and Fourier-transform infrared spectroscopy (FTIR). The extent of grafting was calculated from weight gain and ¹³C resonances. The grafted cellulose was thermally more stable than the parent cellulose. An attempt to do grafting at a higher cut off temperature of 80 °C was made, however, no grafting was observed from ¹³C NMR CP/MAS but TGA results showed that a cellulose having more thermal stability resulted which was attributed to cross linking. Crystallization of CaCO₃ was carried out using the grafted materials as templates showed better nucleation and different crystal structure was observed.     

Crystallization shelves for laboratory furnaces

Several designs of air coolers (modular bilateral “crystallization shelves”), installed in laboratory furnaces are presented. The setup allows easy regulation and simultaneous crystallization of several substances at different temperature gradients, shapes of crystallization fronts and rate intervals, with the purpose of obtaining crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一类热传导问题源项识别的快速稳定算法

利用正算子的性质和Lax-Milgram定理,将一维热传导方程源项识别问题转化为适定的、第二类Volterra方程的求解,给出一个新的快速稳定算法,并进行理论分析.采用两种实现后验准则的新途径,在输入数据的误差水平已知和未知的情况下,快速地决定正则参数.数值实验证实了算法的有效性.     

Dependence of the force action of a water wave on the shape of its leading front

The results of experiments in which bore-type waves with various leading front shapes propagated first above an even horizontal bottom, then above a rising bottom, then again above a horizontal bottom segment, and were finally reflected from a vertical wall are presented. It is shown that the impact force is greatest if the leading front breaks directly on approaching the wall. This force is much greater than the impact force of smooth waves or waves that break before they reach the wall.     

新型快速显微多道分光光度技术对血红蛋白的光谱分析

用新型快速显微多道分光光度(MMSP)技术,在生理环境(pH、温度、氧分压和渗透压)改变下,对单个活态人血红细胞内血红蛋白分子的吸收光谱进行监测。发现生理环境的改变,引起血红蛋白吸收光谱曲线540,575 nm特征吸收峰的峰高、峰位和峰形发生了不同程度的变化。MMSP技术提示血红蛋白分子的结构、浓度和功能与上述生理环境密切相关。