葡萄栽培品种花芽高节位分化观察研究

在管理良好、植株健壮的条件下，葡萄花芽高节位分化是一个普遍的现象。一年生枝从低节位到高节位均可形成正常的花芽，并能正常开花结果，而且高节位分化花芽对当年的果实品质及次年的花芽分化无不良的影响。合理利用这一特性对促进葡萄幼树早丰产有重要的指导意义。     

Differentiation of apple juice samples on the basis of heat treatment and variety using chemometric analysis of MIR and NIR data

The potential of mid-infrared (MIR) and near-infrared (NIR) spectroscopy for their ability to differentiate between apple juice samples on the basis of apple variety and applied heat-treatment was evaluated. The heat-treatment involved exposure of juice samples (15 ml) for 30 s in a 900 W microwave oven and the apple varieties used to produce the juice samples were Bramley, Elstar, Golden Delicious and Jonagold. The chemometric procedures applied to the MIR and NIR data were partial least squares regression (PLS1 for differentiation on the basis of heat-treatment, PLS2 for varietal differentiation) and linear discriminant analysis (LDA) applied to principal component (PC) scores. PLS1 and PLS2 gave the highest level of correct classification of the apple juice samples according to heat-treatment (77.2% for both MIR and NIR data) and variety (78.3–100% for MIR data; 82.4–100% for NIR data), respectively.     

基于遗传算法的六自由度并联平台的控制

由于单通道电液位置伺服系统是一种非线性时变系统,而且有阻尼比小、参数变化大、非线性程度高的特点,传统的PID控制已经很难满足六自由度并联平台的控制精度的要求。针对六自由度并联平台单通道的数学模型,采用遗传算法对其PID控制器的参数进行优化控制,以满足系统的控制精度的要求。仿真结果表明该控制系统的性能指标有了很大改善,证明了该遗传算法的可行性和有效性,克服了传统PID整定参数费时的缺点,对解决实际控制问题提供了有效的方法,并且具有良好的抗干扰能力,其适应性(鲁棒性)也有了很大的提高。     

Efficient conditional probability theorem and importance sampling-based methods for global reliability sensitivity analysis

Global reliability sensitivity (GRS) analysis can measure the effect of random inputs on failure probability (FP). To efficiently solve GRS, two conditional probability theorem (CPT)-based methods are proposed by combining adaptive Kriging (AK) with importance sampling (IS) (CPT-AK-IS) and combining AK with Meta-IS (CPT-AK-Meta-IS) respectively. Firstly, differentiation approximation and CPT are used to convert the estimation of conditional probability density function (PDF), which is required by the existing Bayes theorem-based methods, into that of a series of probabilities. Secondly, GRS can be directly estimated by the failure samples of IS, while the existing Bayes theorem methods based on IS need to transform the failure samples of IS into those of original PDF. Both the first and second strategies can reduce the computational complexity of solving GRS. Thirdly, by selecting a suitable differentiation interval with a proposed adaptive strategy, the estimation of a series of probabilities can be accurately completed as a byproduct of one IS based simulation for solving FP without additional computational cost. Finally, by introducing AK into IS and Meta-IS, it can reduce the number of evaluating performance function and the size of candidate sample pool simultaneously. These novelties are sufficiently verified by the presented examples.     

High speed decoding of the binary (47, 24, 11) quadratic residue code

An efficient table lookup decoding algorithm (TLDA) is presented to decode up to five possible errors in a binary systematic (47, 24, 11) quadratic residue (QR) code. The main idea of the TLDA is based on the weight of syndrome, the syndrome decoder together with a reduced-size lookup table (RSLT), and the shift-search method given by Reed et al. Thus, the size of the lookup table and computational complexity in a finite field can be significantly reduced. The memory size of the proposed condensed lookup table (CLT) consists of only 36.6 Kbytes and is only about 0.24% of the full lookup table (FLT) and 3.2% of the lookup up table given by Chen et al., respectively. These facts lead to significant reduction of computational time and the decoding complexity. A simulation result shows that the decoding speed of the proposed TLDA is much faster than all existing decoding algorithms. Moreover, it can be extended to decode all QR codes, including the class of the cyclic codes when the code length is moderate. The CLT makes this new decoding algorithm suitable for hardware or firmware implementations.     

bFGF促增殖后骨髓间充质干细胞向多巴胺能神经元样细胞的分化

目的探讨碱性成纤维细胞生长因子(Basic fibroblast growth factor,bFGF)体外作用于骨髓间充质干细胞(Mesen-chymal stem cells,MSCs)后,诱导其向神经元样细胞和多巴胺能神经元样细胞定向分化的情况。方法从鼠骨髓中获得MSCs,培养传代,用MTT法检测bFGF对骨髓MSCs生长的影响。10 ng/ml bFGF作用2 d后,通过IBMX、细胞因子bFGF、GDNFI、L-1β、中脑神经胶质细胞条件培养基和中脑神经细胞膜碎片等分组联合诱导骨髓MSCs向神经元样细胞、多巴胺能神经元样细胞分化,免疫细胞化学方法鉴定特异标志NSE、MAP-2a,b和TH的表达。结果在一定范围内,bFGF对骨髓MSCs具有明显的促增殖作用。分化的神经元样细胞表达NSE、MAP-2a,b和TH,联合应用GDNFI、L-1β、中脑条件培养基和中脑神经细胞膜碎片诱导7 d后,NSE阳性率为(27.774±2.747)%,MAP-2a,b为(28.006±3.080)%,TH为(3.098±0.352)%。结论体外骨髓MSCs被诱导分化成神经元样细胞和多巴胺能神经元样细胞,为帕金森等中枢神经系统疾病的细胞移植治疗奠定了基础。     

基于(w，z)参数轴对称3D刚体摆姿态PD控制

基于(w,z)参数化轴对称Three Dimensions(3D)摆的姿态控制问题研究,提出(w,z)参数描述姿态描述方法。该方法通过2次绕正交轴旋转,引入复变量,将球面上的点向复平面投影。提出Proportion Differentiation(pd)控制对轴对称3D摆的姿态控制方法。首先列出轴对称3D摆的动力学方程,以(w,z)参数表示轴对称3D摆的姿态运动学方程及推导过程。利用(w,z)参数设计出PD控制器,使得轴对称3D刚体摆在其倒立位置渐近稳定。仿真实验验证了控制器对轴称3D摆姿态控制的有效。     

基于中国经济社会现状讨论社会空间分异现象

对城市社会空间经典研究理论进行梳理,并探讨国内外相关研究现状。在反思中外城市社会空间分异原因之区别与联系的基础上,探讨我国空间分异机制的相关要素与结果。     

Use of β-hydroxyacyl-CoA-dehydrogenase (HADH) activity to differentiate frozen from unfrozen fish and shellfish

 Further work on an enzymic method to differentiate frozen from unfrozen fish and shellfish is reported. The method is based on the release of the β-hydroxyacyl-CoA-dehydrogenase (HADH) from mitochondria during freezing. Enzymic activity was evaluated in fresh and frozen thawed samples from sole (Solea solea), sea bream (Pagellus centrodontus), hake (Merluccius merluccius), gilt headed bream (Sparus aurata), sea bass (Dicentrarchus labrax), salmon (Salmo salar), prawn (Penaeus japonicus) and Norwegian lobster (Nephrops norvegicus). Changes in the HADH activity of fresh and frozen thawed samples were compared after freezing at –196  °C for 15 min. Two values were obtained: U (by dividing: HADH activity of samples frozen at –196  °C, then thawed/HADH activity of unfrozen samples) and F (by dividing: HADH activity of samples frozen at –18  °C, thawed, then frozen at –196  °C /HADH activity of samples frozen at –18  °C, then thawed). Statistical analysis showed significant differences (P≤0.05) between both quotients for gilt headed bream, salmon, sea bream, sole and prawn, and an arbitrary limit was set at 2 to differentiate frozen thawed from unfrozen samples. The application of this limit made it possible to discriminate the unfrozen from the frozen thawed state of around 90% of the total samples analysed. Best results were obtained for prawn (100% of samples differentiated). In the present paper, a laboratory routine is proposed based on the comparison of the HADH activity of a sample analysed straight away and that of a sample frozen at –196  °C and then thawed. The reported method is simple and fast. The entire laboratory procedure can be performed in 45 min. Received: 20 July 1998 / Revised version: 2 November 1998