外界因素和杜仲叶提取物对双乙酸钠的抑菌活性影响

本文研究了食品基质（蛋白质和碳水化合物浓度）和加工条件（温度和pH）对双乙酸钠（sodium diacetate,SDA）抑菌活性的影响,并考察了SDA与杜仲叶提取物（Eucommia ulmoides leaves extract,EULE）的联合抑菌作用。通过Modified Gompertz动力学方程拟合细菌生长曲线,计算出沙门氏菌和金黄色葡萄球菌的迟缓期（λ）和最大比生长速率（μ_max）。采用二倍稀释法确定了SDA和EULE的最低抑菌浓度（minimum inhibitory concentration,MIC）,并通过棋盘法评价了SDA与EULE的联合抑菌效果。结果表明:高浓度蛋白质（10%牛肉浸粉）和高浓度碳水化合物（7%可溶性淀粉）可减弱SDA的抑菌活性。高温处理（121和138℃）和碱性环境（pH8.5）也会减弱SDA的抑菌活性。酸性环境（pH为4.5、5.5和6.5）可增强SDA的抑菌活性。同时发现,SDA与EULE联用对抑菌效果有相加作用。本研究结果可为SDA在食品工业的应用提供理论参考。     

I2C总线及其应用

主要介绍了I^2C总线的起源、概念及其基本工作原理，并总结了I^2C总线的特点，重点介绍I^2C软件的编写。     

Fall Composition of Storage Lipids is Associated with the Overwintering Strategy of <Emphasis Type="Italic">Daphnia</Emphasis>

Diapause, which occurs through the production of dormant eggs, is a strategy used by some zooplankton to avoid winter months of persistent low temperatures and low food availability. However, reports of active zooplankton under the ice indicate that other strategies also exist. This study was aimed at evaluating whether the composition of storage lipids in the fall differs between diapausing and active overwintering Daphnia. We assessed the quantity of storage lipids and fatty acid (FA) composition of Daphnia species, along with FA content of seston, in six boreal, alpine and subarctic lakes at the onset of winter, and evaluated the association between storage lipids and Daphnia overwintering strategy. We found that active overwintering Daphnia had >55% body fat and the highest FA concentrations. Polyunsaturated FA, especially stearidonic acid (18:4n-3; SDA) and high ratios of n-3:n-6, were preferentially retained to a greater extent in active overwintering Daphnia than in those that entered diapause. Daphnia FA composition was independent of that of the seston diet, indicating that Daphnia adjusted their storage lipids according to the physiological requirements of a given overwintering strategy. The occurrence of an active overwintering strategy has consequences for zooplankton community structure, and can have important implications for the transfer of high-quality energy at higher trophic levels.     

环境化合物降解预测模型的研究

为建立化合物降解的计算机预测模型,确定降解和非降解化合物显然不同的参数.选择389个有机分子作为数据集,选其中312个为训练集,其余77个为验证集,每个分子计算195个分子参数,分别采用逐步判别法和主成分分析法建模,并用外部验证集验证模型的预测能力.结果:逐步判别法分析结果中,训练集的降解和非降解化合物的正确率分别为90.6%和69.5%;验证集的降解和非降解化合物的正确率分别为83.9%和63.6%.主成分分析结果在测试集中,降解和非降解化合物的正确率分别为80.4%和31.8%.验证集的降解化合物和非降解化合物的正确率分别为67.9%和50.0%.因此,采用逐步判别法模拟而建立的数学模型,可作为预测化合物降解的模型.以卜研究可以为预测有机物降解提供参考.     

多类运动想象脑电信号的两级特征提取方法

共同空间模式（Common spatial pattern,CSP）是运动想象脑机接口（Brain-computer interface,BCI）中常用的特征提取方法,但对多类任务的分类正确率却明显低于两类任务.通过引入堆叠降噪自动编码器（Stacked denoising autoencoders,SDA）,提出了一种多类运动想象脑电信号（Electroencephalogram,EEG）的两级特征提取方法.首先利用一对多CSP（One versus rest CSP,OVR-CSP）将脑电信号变换到使信号方差区别最大的低维空间,然后通过SDA网络提取其中可以更好表达类别属性的高层抽象特征,最后使用Softmax分类器进行分类.在对BCI竞赛IV中Data-sets 2a的4类运动想象任务进行的分类实验中,平均Kappa系数达到0.69,表明了所提出的特征提取方法的有效性和鲁棒性.     

云计算在全业务网架构中的应用研究

电信重组促使运营商向全业务运营转型,业务网络架构也需要根据新的需求进行重新梳理。文章从全业务运营的角度出发,基于云计算的架构和服务模式,以中国移动业务网络为例,分析基于云计算构建全业务网络的方法和架构。     

基于数据降维与精确欧氏局部敏感哈希的k近邻推荐方法

针对基于k近邻的协同过滤推荐算法中存在的评分特征数据维度过高、k近邻查找速度慢,以及评分冷启动等问题,提出基于数据降维与精确欧氏局部敏感哈希（E²LSH）的k近邻协同过滤推荐算法。首先,融合评分数据、用户属性数据以及项目类别数据,将融合后的数据作为输入对堆叠降噪自编码（SDA）神经网络进行训练,取神经网络编码部分最后一个隐层的值作为输入数据的特征编码,完成非线性降维。然后,利用精确欧氏局部敏感哈希算法对降维后的数据建立索引,通过检索得到目标用户或目标项目的相似近邻。最后,计算目标与近邻之间的相似度,利用相似度对近邻的评分记录加权得到目标用户对目标项目的预测评分。在标准数据集上的实验结果表明,在冷启动场景下,均方根误差比基于局部敏感哈希的推荐算法（LSH-ICF）平均降低了约7.2%,平均运行时间和LSH-ICF相当。表明该方法在保证推荐效率的前提下,缓解了评分冷启动问题。     

铁氧体-硅双层基片微带线的谱域导抗法分析

该文提出两种铁氧体-硅双层基片的微带线结构,并通过对麦克斯韦方程的坐标旋转和傅里叶变换导出波导纳,用谱域导抗法进行特性分析。尤其是对微带线的色散特性进行了计算,讨论了微带线各种参数对色散特性的影响,并对它们的特性进行了对比,发现其中一种结构的色散受各因素的影响很小,尤其是介质的工艺尺度,可用于更高集成电路的制造中。     

Preparation of stearidonic acid‐enriched triacylglycerols from Echium plantagineum seed oil

HPLC analysis of Echium plantagineum seed oil shows a complex triacylglycerol (TAG) profile. TAG species were separated on an analytical scale by HPLC and their fatty acid (FA) composition is reported. GLC analyses showed that some TAG fractions reached a stearidonic acid (SDA, 18:4n‐3) percentage significantly higher than that in the original oil. TAG separation on a bigger scale was also essayed, by means of a gravimetric normal‐phase chromatographic column, using silver ion‐silica gel as stationary phase. Gradient elution with solvents of increasing polarity was applied, allowing the separation of valuable TAG species containing γ‐linolenic acid (GLA, 18:3n‐6), α‐linolenic acid (ALA, 18:3n‐3) and SDA as the main constituents (more than 85% of the total FA). An enzymatic hydrolysis reaction showed the distribution of FA in the isolated species of TAG. SDA was the major FA in the sn‐2 position (more than 50% of total FA), followed by ALA (19%) and GLA (18.5%).     

利用壳聚糖的生产废弃液制备双乙酸钠

工业上用甲壳素生产壳聚糖会产生高浓度强碱性废液,传统工业方法是将其处理后排放,这样既浪费资源又污染环境。本文利用该废液制备防腐剂——双乙酸钠（SDA）,从废液脱色、浓缩、投入乙酸的量、反应温度、反应时间、干燥温度与时间等制备条件进行了研究,确定了最佳制备工艺。所得产品中含40.38%乙酸和58.42%乙酸钠,水含量小于2%,质量符合FAO/WHO标准。