Stability analysis of the simplest Takagi-Sugeno fuzzy control system using circle criterion

A frequency-domain-based sufficient condition is derived to guarantee the globally asymptotic stability of the simplest Takagi-Sugeno (T-S) fuzzy control system by using the circle criterion. The analysis is performed in the frequency domain, and hence the condition is of great significance when the frequency-response method, which is widely used in the linear control theory and practice, is employed to synthesize the simplest T-S fuzzy controller. Besides, this sufficient condition is featured by a graphical interpretation, which makes the condition straightforward to be used. Comparisons are drawn between the performance of the simplest T-S fuzzy controller and that of the linear compensator. Two numerical examples are presented to demonstrate how this sufficient condition can be applied to both stable and unstable plants.     

The PREPL A protein, a new member of the prolyl oligopeptidase family, lacking catalytic activity

The PREPL (previously called KIAA0436) gene encodes a putative serine peptidase from the prolyl oligopeptidase family. A chromosomal deletion involving the PREPL gene leads to a severe syndrome with multiple symptoms. Homology with oligopeptidase B suggested that the enzyme cleaves after an arginine or lysine residue. Several PREPL splice variants have been identified, and a 638-residue variant (PREPL A) was expressed in Escherichia coli and purified. Its secondary structure was similar to that of oligopeptidase B, but differential-scanning calorimetry indicated a higher conformational stability. Dimerization may account for the enhanced stability. Unexpectedly, the PREPL A protein did not cleave peptide substrates containing a P1 basic residue, but did slowly hydrolyse an activated ester substrate, and reacted with diisopropyl fluorophosphate. These results indicated that the catalytic serine is a reactive residue. However, the negligible hydrolytic activity suggests that the function of PREPL A is different from that of the other members of the prolyl oligopeptidase family.     

耦合诱导的金纳米棒禁戒等离激元模式激发

用时域有限差分方法（finite-difference time-domain,FDTD）模拟了有不同局域等离激元共振频率和不同体积的外来金纳米颗粒以及外来介质纳米颗粒与金纳米棒的耦合,研究了正入射条件下与各种颗粒耦合对诱发金棒上纵向等离激元的禁戒模式的不同影响,发现外来颗粒上足够多的电荷积聚造成的电场对称性破缺是诱发禁戒模式的原因.这一发现对理解金属纳米颗粒的近场光学实验探测有重要意义.     

常规及偶应力轴对称有限元分片检验函数

我们提出的增强型分片检验可以用于检验一类非齐次阶微分方程的有限元的收敛性.由此,建立了常规轴对称问题和轴对称偶应力/应变梯度C1理论有限元增强型分片检验的检验函数,并得到重要结论：这类轴对称有限元的分片检验函数不含常剪应力项.     

腾冲嗜酸两性菌硫氧化还原酶分子结构中铁原子结合位点的新特征

前期研究表明, 铁原子对于嗜酸两性菌中硫氧化还原酶(SOR)的活性至关重要. 本研究表明, 2,2′-联吡啶、1,2-二羟基苯-3,5-二磺酸钠、8-羟基喹啉等特异性铁离子螯合剂强烈抑制腾冲嗜酸两性菌SOR酶活性, 进一步表明铁原子是SOR酶活必需. 对目前基因组数据库中的SOR基因或者SOR类似基因进行序列比对, 发现了一个潜在的铁原子结合模体(H⁸⁶-X₃- H⁹⁰-X_n-E¹¹⁴-X_n-E¹²⁹). 据此, 本研究采用定点突变技术, 将氨基酸残基H⁸⁶, H⁹⁰和E¹²⁹分别突变为苯丙氨酸或者丙氨酸, 圆二色光谱测定发现突变体(H⁸⁶F, H⁹⁰F和E¹²⁹A)的二级结构没有明显改变, 但是这3个突变体全部丧失了酶活性. 突变体蛋白中铁原子含量测定结果表明, 3个突变体全部或者部分丢失了铁原子, 而之前研究中获得的3个半胱氨酸突变体(完全丧失了酶活)铁原子含量没有变化. 根据本研究并结合前期实验结果可知, SOR分子中模体C³¹-X_n-C¹⁰¹-X₂-C¹⁰⁴是底物硫分子活化区域; 而模体H⁸⁶-X₃-H⁹⁰-X₂₃-E¹¹⁴-X_¹⁴-(E/D)¹²⁹是SOR分子中铁原子的结合区域, 与铁原子结合形成一个非卟啉铁中心, 是SOR的氧化还原中心; 这两个区域均是SOR酶活性的必需部分.     

修正表面张力系数的包膜气泡动力学模型

基于包膜造影剂气泡的实际应用, 在传统的三层模型基础上提出了一个修正的动力学模型来描绘包膜气泡的动力学行为. 通过衔接三层模型中包膜的两个边界条件, 得到一个两层模型并简化了方程的结构. 为了使动力平衡更加准确, 在建立边界条件时考虑了包膜质量, 并将包膜层厚度与气泡半径的关系具体化. 更为重要的是, 我们对绝大多数文献中的表面张力系数不变的假设进行了修正, 认为其随半径变化呈非线性变化, 且通过数值计算对表面张力系数修正带来的变化进行了讨论. 此外, 我们应用本文模型对实验得到的Optison及Sonozoid微气泡的动力学曲线进行了拟合, 并与其他经典模型的拟合结果进行了比较, 结论证明了本文模型具有很好的适用性.     

东方龙虱鞘翅:形态学及力学性能研究

研究了东方龙虱鞘翅的拓扑结构及其鞘翅生物材料的力学性能. SEM观测表明鞘翅横向截面和纵向截面结构相同, 是一种具 “桥墩” 状连接的空腔轻质结构, 由致密的黑色外表皮层和其下数十层几丁质纤维层平行、螺旋交织构成的内表皮层组成; 纳米压痕仪测得新鲜鞘翅外侧区域的硬度和弹性模量分别为0.31和6.13 GPa; 拉伸实验得到新鲜鞘翅横向和纵向的强度极限分别为169.2和194.5 MPa; 干燥鞘翅对应的强度极限为85.38和90.91 MPa, 新鲜鞘翅的强度是干燥鞘翅值的2倍; 结果表明甲虫鞘翅是一种力学性能呈现拓扑分布规律的轻质生物复合材料, 该研究为航空航天材料的轻质结构的设计提供了生物学的参考.     

On-chip natural assembly of silicon photonic bandgap crystals.

Photonic bandgap crystals can reflect light for any direction of propagation in specific wavelength ranges. This property, which can be used to confine, manipulate and guide photons, should allow the creation of all-optical integrated circuits. To achieve this goal, conventional semiconductor nanofabrication techniques have been adapted to make photonic crystals. A potentially simpler and cheaper approach for creating three-dimensional periodic structures is the natural assembly of colloidal microspheres. However, this approach yields irregular, polycrystalline photonic crystals that are difficult to incorporate into a device. More importantly, it leads to many structural defects that can destroy the photonic bandgap. Here we show that by assembling a thin layer of colloidal spheres on a silicon substrate, we can obtain planar, single-crystalline silicon photonic crystals that have defect densities sufficiently low that the bandgap survives. As expected from theory, we observe unity reflectance in two crystalline directions of our photonic crystals around a wavelength of 1.3 micrometres. We also show that additional fabrication steps, intentional doping and patterning, can be performed, so demonstrating the potential for specific device applications.     

Programmable and autonomous computing machine made of biomolecules.

Devices that convert information from one form into another according to a definite procedure are known as automata. One such hypothetical device is the universal Turing machine, which stimulated work leading to the development of modern computers. The Turing machine and its special cases, including finite automata, operate by scanning a data tape, whose striking analogy to information-encoding biopolymers inspired several designs for molecular DNA computers. Laboratory-scale computing using DNA and human-assisted protocols has been demonstrated, but the realization of computing devices operating autonomously on the molecular scale remains rare. Here we describe a programmable finite automaton comprising DNA and DNA-manipulating enzymes that solves computational problems autonomously. The automaton's hardware consists of a restriction nuclease and ligase, the software and input are encoded by double-stranded DNA, and programming amounts to choosing appropriate software molecules. Upon mixing solutions containing these components, the automaton processes the input molecule via a cascade of restriction, hybridization and ligation cycles, producing a detectable output molecule that encodes the automaton's final state, and thus the computational result. In our implementation 1012 automata sharing the same software run independently and in parallel on inputs (which could, in principle, be distinct) in 120 microl solution at room temperature at a combined rate of 109 transitions per second with a transition fidelity greater than 99.8%, consuming less than 10-10 W.     

Superconductivity in CaCuO2 as a result of field-effect doping.

Understanding the doping mechanisms in the simplest superconducting copper oxide-the infinite-layer compound ACuO2 (where A is an alkaline earth metal)-is an excellent way of investigating the pairing mechanism in high-transition-temperature (high-Tc) superconductors more generally. Gate-induced modulation of the carrier concentration to obtain superconductivity is a powerful means of achieving such understanding: it minimizes the effects of potential scattering by impurities, and of structural modifications arising from chemical dopants. Here we report the transport properties of thin films of the infinite-layer compound CaCuO2 using field-effect doping. At high hole- and electron-doping levels, superconductivity is induced in the nominally insulating material. Maximum values of Tc of 89 K and 34 K are observed respectively for hole- and electron-type doping of around 0.15 charge carriers per CuO2. We can explore the whole doping diagram of the CuO2 plane while changing only a single electric parameter, the gate voltage.