Interpolymer radical coupling: A toolbox complementary to controlled radical polymerization

The current review focuses on the relevance and practical benefit of interpolymer radical coupling methods. The latter are developing rapidly and constitute a perfectly complementary macromolecular engineering toolbox to the controlled radical polymerization techniques (CRP). Indeed, all structures formed by CRP are likely to be prone to radical coupling reactions, which multiply the available synthetic possibilities. Basically, the coupling systems can be divided in two main categories. The first one, including the atom transfer radical coupling (ATRC), silane radical atom abstraction (SRAA) and cobalt-mediated radical coupling (CMRC), relies on the recombination of macroradicals produced from a dormant species. The second one, including atom transfer nitroxide radical coupling (ATNRC), single electron transfer nitroxide radical coupling (SETNRC), enhanced spin capturing polymerization (ESCP) and nitrone/nitroso mediated radical coupling (NMRC), makes use of a radical scavenger in order to promote the conjugation of the polymer chains. More than a compilation of macromolecular engineering achievements, the present review additionally aims to emphasize the particularities, synthetic potential and present limitations of each system.     

Minor Role of Mitochondrial Respiration for Fatty-Acid Induced Insulin Secretion

An appropriate insulin secretion by pancreatic beta-cells is necessary to maintain glucose homeostasis. A rise in plasma glucose leads to increased metabolism and an elevated cytoplasmic ATP/ADP ratio that finally triggers insulin granule exocytosis. In addition to this triggering pathway, one or more amplifying pathways—activated by amino acids or fatty acid—enhance secretion by promoting insulin granule recruitment to, and priming at, the plasma membrane. The aim of this study was to clarify the impact of the mitochondrial respiratory activity on fatty acid-induced insulin secretion that was assessed by an extracellular flux analyzer. Treatment of isolated mouse islets with glucose (20 mM) increased insulin secretion 18-fold and correlated with ATP-synthesizing respiration. Furthermore, oxygen consumption rate (OCR) significantly increased by 62% in response to glucose, whereas the addition of palmitate resulted only in a minor increase of OCR at both 2.8 mM (11%) and 20 mM glucose (21%). The addition of palmitate showed a pronounced increase of coupling efficiency (CE) at 2.8 mM glucose but no further insulin secretion. However, treatment with palmitate at 20 mM glucose increased insulin secretion about 32-fold accompanied by a small increase in CE. Thus, fatty acid induced respiration has a minor impact on insulin secretion. Our data clearly demonstrate that fatty acids in contrast to glucose play a minor role for respiration-mediated insulin secretion. In the presence of high glucose, fatty acids contribute partially to amplifying pathways of insulin secretion by further increasing mitochondrial activity in the islets of Langerhans.     

Cooperative Effects in the Photoluminescence of (In,Ga)As/GaAs Quantum Dot Chain Structures

Multilayer In_0.4Ga_0.6As/GaAs quantum dot (QD) chain samples are investigated by means of cw and time-resolved photoluminescence (PL) spectroscopy in order to study the peculiarities of interdot coupling in such nanostructures. The temperature dependence of the PL has revealed details of the confinement. Non-thermal carrier distribution through in-chain, interdot wave function coupling is found. The peculiar dependences of the PL decay time on the excitation and detection energies are ascribed to the electronic interdot coupling and the long-range coupling through the radiation field. It is shown that the dependence of the PL decay time on the excitation wavelength is a result of the superradiance effect.     

钢管穿轧过程的三维热力耦合模拟

描述了使用有限元方法(FEM)模拟钢管在曼内斯曼式穿轧机上的穿孔过程,建立了三维有限元模型,并考虑了在金属成形过程中出现的热力学现象。模拟的结果动态地显示了在工件内部等效应变、等效应变率和温度的分布。基于这些参数,分析了钢管的穿孔过程,同时通过实验测试与有限元模拟的结果进行对比。结果表明,测试的结果与有限元模拟的结果比较吻合。     

德制紧固螺栓的性能跟踪与安全性分析

德国ABB公司200MW进口机组在早期基建安装阶段发现对轮螺栓等一批螺栓硬度值高于德国提供的要求。为了掌握材料运行后的性能变化规律和安全性能，对该批螺栓的力学性能、显微组织、热处理工艺和运行工况等情况进行了系统的研究与分析，认为德制高硬度螺栓运行8年后的微观组织及力学性能的变化是好的，可以满足机组的安全要求。     

Implementation of Two-Dimensional Polycrystalline Grains in Object Oriented Micromagnetic Framework

In response to the growing need for a more accurate micromagnetic model to understand switching phenomenon in nanoscale magnets, we developed the capability to simulate two-dimensional polycrystalline grains using the Object Oriented Micromagnetic Framework (OOMMF). This addition allows users full flexibility in determining the magnetocrystalline anisotropy and axe in each grain as well as the inter- and intragranular exchange coupling strength.     

Fabrication and Magnetic Properties of Fe<Subscript>65</Subscript>Co<Subscript>35</Subscript>–ZnO Nano-Granular Films

A series of nano-granular films composed of magnetic metal (Fe₆₅Co₃₅) granules with a few nanometers in size and semiconductor oxide (ZnO) have been fabricated by a magnetron sputtering method, and excellent soft magnetic properties have been achieved in a wide metal volume fraction (x) range for as-deposited samples due to the exchange coupling between FeCo granules (a ferromagnetic interaction in nano-scale). In a wide range (0.53 < x < 0.71), the films exhibit coercivity H _C not exceeding 15 Oe, along with high resistivity. Especially for the sample with x = 0.67, coercivities in hard and easy axes are 1.43 and 7.08 Oe, respectively, 4πM _S  = 9.85 kg, and ρ reaches 2.06 × 10³ μΩ cm. The dependence of complex permeability μ = μ′ − jμ″ on frequency shows that the real part μ′ is more than 100 below 1.83 GHz and that the ferromagnetic resonance frequency reaches 2.31 GHz, implying the promising for high frequency application. The measured negative temperature coefficient of resistivity reveals that may be the weak localized electrons existing in samples mediate the exchange coupling.     

Combining continuous catalytic regenerative naphtha reformer with thermally coupled concept for improving the process yield

Advancements in the catalytic naphtha reforming process, as one of the main processes in petrochemical industry, contributed to development of continuous catalytic regenerative naphtha reformer units. Increasing the yield of aromatic and hydrogen as well as saving the energy in this process through the application of thermal coupling technique is a potentially interesting idea. This novel idea has been assessed in this paper. In the proposed configuration, continuous catalyst regeneration naphtha reforming process is coupled with hydrogenation of nitrobenzene in a two co-axial reactor separated by a solid wall, where the generated heat in nitrobenzene hydrogenation reaction transfers to naphtha reforming reaction medium through the surface of the tube. A steady-state, homogeneous, two-dimensional model is used to describe the performance of this configuration and a kinetic model including 32 pseudo-components with 84 reactions is considered for naphtha reforming reaction. After validating the model with the commercial data of a domestic plant, the obtained results of coupled reactor are compared by the conventional one. The obtained results show the superiority of CCR coupled reactor against the conventional one.     

Electronically coupled porphyrin-arene dyads for dye-sensitized solar cells

An acetylene-linked porphyrin-perylene anhydride and an acetylene-linked porphyrin-naphthalic anhydride have been synthesized; the highly conjugated acetylenic bridge in these porpyrins efficiently mediates electronic interaction between the porphyrin and perylene units to extend the π-conjugation of the porphyrin dye and to cause both broadening and red shifts of both the Soret and Q absorption bands. This condition is a useful feature for efficient dye-sensitized solar cell applications. The optical, electrochemical and photovoltaic properties of the new linked anhydrides show that the HOMO-LUMO gap decreased upon extension of π-conjugation, indicating a strong electronic coupling between the porphyrin and the perylene or naphthalene unit.     

Modal criteria for optimization of structures through active structural acoustic control

This paper deals with modal criteria allowing optimization of structures through active structural acoustic control (ASAC) based on the independent modal strategy control (IMSC). The aim of the paper is to propose efficient criteria allowing to process optimization of structures by determining the most important modes to control considering only the location of the excitation on the structure. A generalized modal synthesis is used to study the coupled fluid–structure system. Modal criteria are proposed in order to determine the best choice for the controlled modes used in IMSC method. The way the ASAC will be applied is not discussed in the paper. Numerical simulations are computed to show the efficiency of the method, considering a simple vibroacoustic structure. Copyright © 2010 John Wiley & Sons, Ltd.