高层建筑结构自由振动的渐近解法

In this paper, the iteration method is used to calculate the free vibration of tall building structures and the iteration formula is derived with the static analysis. The principle and general steps to calculate the structural frequency and mode by using     

水溶性低分子量酚醛树脂的合成

利用凝胶渗透色谱仪对16种不同合成条件的水[溶性低分子量酚醛树脂样品进行检测，分别求得数均分子量mn，重均分子量mw和树脂质量指标。结果表明，苯酚：甲醛：NaOH的摩尔比为1：2．1：0．1，反应时间超过180min后，PF 预聚物的分散指数小，分子量均匀，GPC谱图显示，谱峰比较稳定，分子量分布在200－400之间的占98．3％，树脂质量指标检测表明，固体含量为49．8％，游离苯酚含量为0．18％，游离甲醛含量为0．14％，可被溴化物含量为15．5％；树脂粘度为8．8m|Pa.s；树脂的PH值为9．23，水混合倍数为L＞7．5。     

南疆地区部分县,团场棉籽饼棉酚含量的测定

本试验采用间苯三酚法测定了南疆地区部分县(市)、团场的棉籽饼粕游离棉酚的含量,为畜禽饲养者提供了一个饲喂棉籽饼的科学依据.并且分析了棉籽中游离棉酸含量高的原因,同时,说明了常用脱毒剂硫酸亚铁的添加比例应为:游离棉酚含量:硫酸亚铁=1:5.     

书院历史变迁与士大夫价值取向

中国书院历经了一千多年的历史发展与制度变迁。书院一方面体现出独立的文化创新精神,成为当时教育改革、学术创新的大本营;另一方面又与官方密切合作,有很强的“官学化”趋势。导致书院发展趋势与变迁的原因在书院内部,即作为书院创建、主持的古代士大夫及其价值取向。     

Dietary taurine supplementation enhances antioxidative capacity and improves breast meat quality of broiler chickens

ABSTRACT

1. The aim of this study was to determine the effect of dietary taurine supplementation on growth performance, meat quality and antioxidant responses in breast muscle of broiler chickens.

2. A total of 72 Arbor Acres broiler chickens (28-day-old) with similar body weight were randomly allocated into two groups, and fed either 0 g/kg (control; C) or 5 g/kg taurine-supplemented diets (TS) for 14 days.

3. The results showed that TS had no effect on growth performance or chemical composition of breast muscle in broilers. The drip and cooking losses were significantly decreased (P < 0.05), and the pH_24h of breast muscle were increased (P < 0.05) in the TS group. Meanwhile, broilers in the TS group exhibited significantly higher (P < 0.05) scavenging activities of superoxide and 2,2-diphenyl-1-picrylhydrazyl radicals, and lower (P < 0.05) contents of carbonyl, malondialdehyde, and 4-hydroxynonenal. TS increased (P < 0.05) total antioxidant capacity and superoxide dismutase activities. Moreover, TS significantly upregulated (P < 0.05) the mRNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1, NAD(P)H quinone dehydrogenase 1, superoxide dismutase, catalase, and glutathione peroxidase.

4. These findings suggested that TS enhanced antioxidative capacity and improved breast meat quality of broilers via activating the Nrf2 pathway.     

小麦突变体返白系返白机理研究 Ⅲ.返白阶段叶蛋白质、游离氨基酸变化规律的分析

在返白过程中,近白系叶片蛋白氮含量降低,蛋白酶活性升高,总游离氨基酸积累,各游离氨基酸组分变化幅度不同。变化最大的丝氨酸在全白叶片中可占总游离氨基酸量的50％。认为蛋白质含量下降,游离氨基酸增多与蛋白酶活性升高有关。SDS-PAGE分析发现,叶蛋白质组分没有明显的差异,各组分的含量均有下降。Rubisco减少最多,全白叶中几乎见不到它的条带。复绿过程中以上各变化均逆转回复。     

Volatile flavor changes responding to heat stress‐induced lipid oxidation in duck meat

The effects of heat stress on lipid oxidation and volatile compounds in duck meat were investigated. To simulate heat stress on ducks, room‐temperature was controlled at 25°C, except that a raised temperature of 32°C for 8 hr each day was conducted. After stress for 1 and 3 weeks, respectively, the birds were euthanized and the breast meat was separated to evaluate the changes of lipid oxidation and volatile flavor compounds. Results showed that heat stress significantly increased the lipoxygenase activity and thiobarbituric acid reactive substances, and reduced the contents of free unsaturated fatty acids in duck meat. A total of 85 volatile flavor compounds were detected by gas chromatography‐mass spectrometry. Interestingly, when exposed to heat stress, the volatiles generation in raw duck meat was promoted, which was then inhibited after cooking. These data reveal meat oxidative changes and flavor loss caused by heat stress and provide useful information for potential labels and meat flavor preservation against the negative effects of heat stress.     

土壤中偏二甲肼的吸附及降解规律研究

对偏二甲肼在红壤土和黄棕壤土中的吸附及降解进行了研究。通过对不同浓度的偏二甲肼在这两种土壤中的吸附的研究,用改进的平衡法给出了偏二甲肼在这两种土壤中的吸附等温线,得出了它们的吸附常数。通过对偏二甲肼降解产生的中间产物甲醛的初步研究,得到偏二甲肼在两种土壤中降解产生的甲醛浓度随时间的变化趋势,并对测得结果进行了讨论。     

儿茶素抗氧化作用的协同增效效应

用电子自旋共振(ESR)和化学发光技术,研究了(-)-EGCG、(-)-ECG、(-)-EC、(-)-EGC 4种儿茶素及其不同组合,对超氧阴离子自由基(O(?))的清除作用。结果表明,单一儿茶素以(-)-EGCG 的清除能力最强,其纳摩尔清除率为316.3,其次为(-)-ECG,纳摩尔清除率为262.9;两两不同组合对O(?)的清除率以(-)-EGCG+(-)-ECG 效果最佳,比各自单独存在时要增效,三三组合时以(-)-EGCG+(-)-ECG+(-)-EC 组合效果最佳,增效效果明显,且强于两两组合。这些组合的增效效果与体系中存在的儿茶素的摩尔浓度呈高度的线性正相关。4种儿茶素组成不同的比例,以茶叶天然组成增效效果最明显。用伏安法测得的各儿茶素第一还原电位由高到低的次序为:(-)-EGCG>(-)-ECG>(-)-EGC≈(-)-EC,这一电位次序是儿茶素构成抗氧化循环的根本所在。