基于电子管SRPP电路的高保真耳机放大器设计

以电子管微变等效电路分析为基础,设计了一款以驱动高保真耳机为目的的耳机放大器.该放大器以共阴极放大器为输入级,SRPP放大器为输出级,驱动耳机工作.分析了该放大器的开环和闭环参数,并采用客观测量和主观评价的方式对该放大器的品质进行评价.     

S波段微波照射对大鼠免疫功能的影响

用S波段高功率微波照射大鼠,观察大鼠白细胞计数、淋巴细胞数、T细胞及其亚群和免疫球蛋白的变化,以期了解S波段高功率微波照射对大鼠免疫功能的影响.结果表明,S波段高功率微波照射可以引起大鼠白细胞水平降低,T细胞亚群出现兴奋效应,免疫球蛋白早期出现不同程度的降低,表现出低剂量刺激而高剂量抑制的效应.     

提高GPS长基线解算精度的探讨

随着GPS（Global Positioning System）定位技术应用的不断扩展,各地陆续建立GPS连续运行参考站,而参考站的分布稀疏、GPS基线较长,定位精度受到各种误差的影响。其中与距离有关的误差,尤其是对流层延迟使定位精度降低。为了满足GPS高精度定位的需要,文中利用普通克利金（Kriging）内插法精确确定了对流层延迟,通过消弱此影响来提高GPS长基线解算的精度,并通过实例证实了GPS定位精度的提高。     

FEMWATER在地下水流数值模拟中运用

GMS是目前使用广泛的一个地下水模拟软件,它包含多个水流模拟计算模块,其中基于有限元分析的FEMWATER模块是一个功能强大的三维水流-溶质运移的数值模拟模块。迄今为止, FEMWATER在国内地下水数值模拟中的运用甚少。本文介绍了FEMWATER主要特点和应用领域,采用基准问题(Theis问题和Henry问题)对模型进行校正,然后选取了张家港合兴地块为实例,对该研究区的地下水流模型采用FEMWATER进行数值模拟,对比分析了FEMWATER和MODFLOW模拟结果,并由此概括了有限元和有限差分计算中的不同和FEMWATER运用注意事项,为他人今后开展相关工作提供参考。     

PCC在双转子连续混炼机控制系统中的应用

采用先进的PCC控制系统实现了对双转子连续混炼机的有效控制。介绍了该系统的整体方案,简述了该控制系统的特点,重点阐述了在设备运行中对混炼机、喂料机、单螺杆挤出机及切粒机等主要部件的连锁控制及对相关回路的PID控制。该系统具有友好的人机界面、操作简便、运行可靠等特点。     

Characterization,Expression Profiling,and Biochemical Analyses of the Cinnamoyl-CoA Reductase Gene Family for Lignin Synthesis in Alfalfa Plants

Cinnamoyl-CoA reductase (CCR) is a pivotal enzyme in plant lignin synthesis, which has a role in plant secondary cell wall development and environmental stress defense. Alfalfa is a predominant legume forage with excellent quality, but the lignin content negatively affects fodder digestibility. Currently, there is limited information on CCR characteristics, gene expression, and its role in lignin metabolism in alfalfa. In this study, we identified 30 members in the CCR gene family of Medicago sativa. In addition, gene structure, conserved motif, and evolution analysis suggested MsCCR1–7 presumably functioned as CCR, while the 23 MsCCR-likes fell into three categories. The expression patterns of MsCCRs/MsCCR-likes suggested their role in plant development, response to environmental stresses, and phytohormone treatment. These results were consistent with the cis-elements in their promoters. Histochemical staining showed that lignin accumulation gradually deepened with the development, which was consistent with gene expression results. Furthermore, recombinant MsCCR1 and MsCCR-like1 were purified and the kinetic parameters were tested under four substrates. In addition, three-dimensional structure models of MsCCR1 and MsCCR-like1 proteins showed the difference in the substrate-binding motif H212(X)2K215R263. These results will be useful for further application for legume forage quality modification and biofuels industry engineering in the future.     

Biochemical characteristics and thermal inhibition kinetics of polyphenol oxidase extracted from Thompson seedless grape

Polyphenol oxidase (PPO) was isolated from Thompson seedless grape (Vitis vinifera ‘Thompson Seedless’), and its biochemical characteristics were studied. The PPO showed activity to catechol and D, L-DOPA, but not towards monophenol l-Tyrosine, diphenols guaiacol and caffeic acid, and triphenols pyrogallic acid and gallic acid. Apparent Michaelis–Menten constant (K _m) and maximum velocity of the reaction (V _max) values were 45.0 ± 0.05 mM and 500.0 ± 15.3 OD_400 nm/min for catechol, and 34.6 ± 0.03 mM and 384.6 ± 11.7 OD_478 nm/min for D, L-DOPA, respectively. The obtained similar specificity values of V _max/K _m ratio of catechol and D, L-DOPA indicated their similar affinity to Thompson seedless PPO. The most effective inhibitor was l-cysteine, followed in decreasing order by ascorbic acid, sodium metabisulfite, EDTA, NaCl, and citric acid. It was discovered that metal ions of Mg²⁺ and Cu²⁺ increased, while Zn²⁺ and K⁺ reduced the PPO activity. Sugars showed inhibition on the PPO activity, with higher effect by sucrose and lower effect by fructose and glucose. Optimum pH and temperature for grape PPO activity were 6.0 and 25 °C with 10 mM catechol as substrate. The enzyme was heat stable between 10 and 25 °C, but showed significant activity loss at temperatures higher than 40 °C and completely inactivation at 70 °C for 10 min. Thermal inactivation of PPO showed a first-order kinetic with an activation energy (E _a) of 146.1 ± 10.8 kJ/mol at pH 6.0.     

啤酒生产过程中氧化还原酶系的研究

啤酒生产过程中的氧化还原酶与啤酒风味陈化紧密相关。低水分下，其耐温活性远高于其它几种酶，在麦芽中酶活升高比例最大（与大麦中的酶活相比），其在糖化过程中氧化多酚的能力远大于多酚氧化酶。糖化过程中迅速失活，而脂肪酸氧化酶在糖化起始的低温阶段仍有部分酶活，影响不饱和脂肪酸的氧化。焙燥过程中适当延长50～70℃温度段时间，可有效降低麦芽中氧化还原酶的酶活。结合这些酶的性质，从部分抑制它们的活性角度出发，在糖化过程中，于50～60℃进行隔氧处理，可经济、有效的减少影响风味氧化的前驱物质的含量。同一质量等级不同品种的麦芽的氧化还原酶系差别相当大，相应制得的麦汁中与风味氧化有关的物质含量也有较大差别，这可能是造成不同批次原料酿造的成品啤酒风味保鲜期不稳定的原因之一。     

消火栓按钮的设置和接线

通过分析试验和检查用消火栓的功能要求,指出该处消火栓设置按钮的必要性,从防雷电电磁脉冲角度提出了试验和检查用消火栓按钮的设置原则;通过对设计上常用的消火栓按钮接线方式的分析,提出了消火栓按钮接线的最佳方案。     

超声波辅助提取油茶籽油工艺条件研究

以油茶籽为原料,筛选出正己烷为提取油茶籽油的适宜溶剂,并确定了最佳提取方法。考察料液比、提取温度和提取时间等因素对油茶籽油得率的影响,在单因素试验的基础上,通过正交试验确定了提取油茶籽油的较佳工艺条件,并对该工艺条件下提取的油茶籽油进行了理化检测。结果表明:在试验范围内,各因素对油茶籽油得率的影响依次为提取温度>料液比>提取时间。以正己烷为溶剂提取油茶籽油的较佳工艺参数:料液比为1:12、超声波提取温度60℃、提取时间30 min。在该工艺条件下得率达40.89%,所得油茶籽油的各项理化指标均达到了国家标准要求。