硫代硫酸钠法测定过氧化氢的最佳硫酸用量研究

[目的]采用Na2S2O3滴定法测定土壤液中H2O2含量经济、快捷,但酸度严重影响测定结果的准确性。[方法]对Na2S2O3法测定H2 O2时稀H2 SO4用量进行研究。[结果]对理论浓度为9.898 mol/L H2 O2样品进行6次平行测定,回收率达98.8%～100.8%,相对标准偏差（RSD）为0.83%,平均值为9.857 mol/L。[结论]只有稀H2SO4用量至少为理论值的2倍（[H＋]/[H2O2]≥4）,才能抑制H2O2歧化反应的发生,且Na2S2O3的歧化反应不会发生。     

巴梨适宜采收期的初步研究

研究了不同采收期巴梨果实品质和在常温（25℃）下所需的后熟时间。结果表明,北京地区巴梨最适采收期以果实固酸比达到70左右为宜。采收时果实固酸比值是反映果实品质和采后耐贮性的一个关键指标。     

脱水蓖麻油聚酰胺-环氧树脂体系的固化反应动力学研究

由脱水蓖麻油制得聚酰胺固化剂,并用差示扫描量热法(DSC)研究了该固化剂与环氧树脂体系(DCOPA-EP)的固化反应动力学.综合采用Kissinger、Crane和Malek等方法探讨DCOPA-EP固化体系的固化动力学模型参数.由Kissinger方法算得表观活化能( E a)55.94kJ/mol,频率因子( A )1.61×107s-1;并经过分析验证,Malek法所得自催化反应模型(反应级数 m ＝0.135, n ＝0.766)比Crane法的 n 级反应模型(反应级数 n =0.90)更适合DCOPA-EP固化体系.     

不同催化剂条件下毛竹材液化反应动力学研究

为了筛选出高效液化竹材催化剂,达到竹材温和条件下液化,该文利用等温差示热量扫描曲线方法,分析了不同催化剂（KCl和K2 CO3）对毛竹材液化剂苯酚液化反应的影响。在20～300℃温度范围内,运用Kissinger方程在不同的升温速率（5、10、15和20℃/min）下进行动力学研究。结果表明:竹材液化反应是吸热反应;随着升温速率的增加,特征液化温度向高温方向移动;不同催化剂（K2 CO3、KCl、无催化剂）条件下竹材液化反应表观活化能依次是45.95、59.99、58.00 kJ/mol,可见K2 CO3适合做竹材液化的催化剂。由外推法得出竹材液化反应最佳工艺为:催化剂为K2 CO3,初始液化温度为691℃,液化峰高温度为97.3℃,液化峰终温度为111.9℃。      

室内培养条件下两种氨挥发监测方法的比较

为探索一种简单、快捷的氨挥发监测体系,采用室内静态密闭土壤培养方法,对氨气检测管法与目前常用的硼酸吸收-标准酸滴定法所监测的氨挥发结果进行对比研究。结果表明:加入200 mg N·kg~(-1)尿素态氮的条件下,硼酸吸收-标准酸滴定法和氨气检测管法所测氨挥发累积损失量分别为3.29 mg N·kg~(-1)和3.05 mg N·kg~(-1),累积氨挥发损失率分别为1.26%和1.15%;加入氮量增加至400 mg N·kg~(-1)时,两种方法所测氨挥发累积损失量分别是7.20 mg N·kg~(-1)和7.16 mg N·kg~(-1),累积氨挥发损失率分别为1.61%和1.59%。两种方法的氨挥发损失动力学过程和累积氨挥发损失量具有良好的一致性。研究表明,氨气检测管法适用于室内静态密闭培养过程氨挥发监测。     

新疆奎屯排碱渠生物膜胞外聚合物与As(Ⅲ)的络合作用

新疆奎屯地区是地质背景高砷区,排碱渠水体砷（As）污染严重,排碱渠中普遍发育的生物膜胞外聚合物（EPS）与As之间的络合会影响砷的迁移扩散,进而影响到砷的生物毒性和生态风险。目前,排碱渠中普遍发育的生物膜EPS对水中As的迁移转化及行为归宿的影响还完全不清楚。本文结合荧光猝灭滴定技术和等温微量热滴定技术研究了该地区普遍发育的藻生物膜EPS与As（Ⅲ）之间的相互作用。荧光猝灭实验表明：排碱渠生物膜EPS有3个荧光峰：峰A属于含芳环基团的蛋白质Ⅱ;峰B属于溶解性的微生物类蛋白质;峰C属于类腐殖酸。峰A和峰B统称为类蛋白质物质,其中峰B被确定为类色氨酸物质。类蛋白物质与As（Ⅲ）具有较强的结合作用,而类腐殖酸物质与As（Ⅲ）几乎没有结合能力。EPS与As（Ⅲ）荧光淬灭作用属于静态淬灭和动态碰撞淬灭,同时存在的复合淬灭机制。EPS中含芳环基团的蛋白质Ⅱ和类色氨酸物质与As（Ⅲ）的结合常数lg Kb分别为3.82和2.22,说明As（Ⅲ）与前者的结合强度比后者大一个数量级,前者与As（Ⅲ）形成络合物的稳定性稍微大于后者。As（Ⅲ）可以与含芳环基团的蛋白质Ⅱ的多类位点结合,且在多类结合位点之间存在拮抗竞争作用,而类色氨酸物质中只有一类位点参与As的络合。等温微量热滴定实验结果经过Independent模型拟合,求得了EPS和As（Ⅲ）络合反应的热动力学参数：ΔH、ΔG、ΔS。负的焓变ΔH和负的吉布斯自由能ΔG证明EPS与As（Ⅲ）间的络合反应是一个自发进行的放热反应。随着络合反应进行,反应体系的无序度增加,反应为熵驱动。排碱渠生物膜EPS中的类蛋白质在As（Ⅲ）的迁移转化及其生态风险中起着重要作用,而EPS中的类腐殖酸物质不会对As（Ⅲ）的环境行为产生显著影响。     

Determination of the energy value of corn distillers dried grains with solubles containing different oil levels when fed to growing pigs

This experiment used indirect calorimetry to determine the net energy (NE) content of five corn distillers dried grains with solubles (corn DDGS) containing different oil levels and to compare the NE obtained using indirect calorimetry with that calculated using previously published prediction equations. There were two samples of high‐oil DDGS, one sample of medium‐oil DDGS and two samples of low‐oil DDGS. Twelve barrows (initial BW of 32.8 ± 2.0 kg) were used in a repeated 3 × 6 Youden square design with three periods and six diets. The diets were comprised of a corn–soybean meal basal diet and five diets containing 29.25% of one of the corn DDGS added at the expense of corn and soybean meal. During each period, the pigs were individually housed in metabolism crates for 16 days which included 7 days for adaption to feed and environmental conditions. On day 8, the pigs were transferred to respiration chambers and fed one of the six diets at 2300 kJ ME/kg BW^0.6/day. Faeces and urine were collected from day 9 to 13 and heat production (HP) was also measured. From day 14 to 15, the pigs were fed 893 kJ ME/kg BW^0.6/day to allow them to adapt from the fed to the fasted state. On the last day of each period (day 16), the pigs were fasted and fasting HP was measured. The digestible energy value was 16.0, 17.1 and 15.3 MJ/kg DM, the metabolizable energy value was 14.6, 15.5 and 13.7 MJ/kg DM and the NE value was 10.7, 11.0 and 9.4 MJ/kg DM, for the high‐oil, medium‐oil and low‐oil corn DDGS, respectively. The NE obtained with indirect calorimetry in the present study did not differ from values calculated using previously published prediction equations.     

Evaluation of the thermal property of bovine intramuscular adipose tissue using differential scanning calorimetry

The thermal property of bovine intramuscular adipose tissue (IAT) was evaluated using differential scanning calorimetry (DSC) and compared with the melting point temperature (MP) of the fat extract of IAT, which was measured using the slip point method. The beef samples were classified according to the beef marbling score (BMS). Beef with a high BMS contained less protein than that with middle or low BMS. Beef with a high BMS contained significantly more fat than that with a low BMS (P < 0.05). The endothermic point temperature (EP) of IAT, measured by DSC, was significantly higher than the MP of IAT fat (P < 0.05). The EP showed no significant difference among the three marbling grade groups. Although the MP was correlated with the monounsaturated fatty acids (MUFA) content of IAT (R² = 0.505), there was no correlation between the EP and the MUFA (R² = 0.040). However, the EP of IAT treated with collagenase was relatively highly correlated with the MP (R² = 0.655). Thus, these results suggested that DSC analysis would give us the practical thermal information regarding the melt‐in the‐mouth of beef such as the gelatinization of collagen, along with the melting of fat in IAT.     

饲喂水平对杂交肉羊(母)营养物质代谢及能量需要参数的影响

采用完全随机试验设计,将15只出生日期相近、体况良好、体重均匀的杂交母羊随机分成3组(每个处理5只羊),分别按自由采食(AL)、限饲70%(IR70)和限饲40%(IR40)3水平投喂试验饲粮,试验期26 d,连续两期试验。结果表明,饲喂水平对杜寒杂交母羊生长性能及营养物质采食量有极显著影响(P0.01),但对营养物质消化率无影响(P0.05);饲喂水平对杂交肉羊甲烷排放量、甲烷能及产热量均有极显著影响(P0.01);试验母羊绝食60 h时,FHP为0.20和0.24 MJ·kg~(-1)·W0.75,NEm为0.24和0.288 MJ·kg~(-1)·W0.75。文章旨在利用"开放式"呼吸测热装置研究杜寒杂交母羊营养物质代谢及能量需要参数,为肉羊科学饲养提供依据。     

宁夏灌淤土对磷吸附的初步研究

本文报道了宁夏灌淤土12个代表性土样对磷的等温吸附与解吸特性。实测吸附曲线与Preundlich、Langmuir和Temkin三种等温吸附方程都很吻合。全部供试样品的相关系数变化在0.931-0.999之间,均达极显著水平(p<0.01)。其中Langmuir等温式与本实验资料最为吻合。供试土壤对磷的最大吸附量(X_m)变化在172-460μgP/g之间,平均为347±28μgP/g。影响其大小的因子主要是物理性粘粒和CaCO₃,含量,均达极显著正相关。灌淤土不同土层的吸磷量大小依次为:剖面24>23>21>22,而解吸磷能力大小依次为:剖面23>22>21>24。磷的解吸量与吸附量之间呈极显著正相关。根据本试验数据,土壤对磷的等温吸附曲线可以用来预测土壤需磷量。