脱水菠菜贮藏过程中颜色变化动力学

为了探讨脱水菠菜在贮藏过程中叶绿素变化及其与颜色损失的关系,鲜菠菜经过热烫处理后冷冻干燥,包装后在25、35、45和55℃下贮藏,测定贮藏过程中叶绿素和颜色变化,以确定脱水菠菜叶绿素和颜色变化动力学。结果表明：无论是否经过热烫前处理,经过冻干技术得到的脱水菠菜,在贮藏过程中其叶绿素的降解与颜色损失都遵循一级反应动力学方程,且叶绿素的减少与颜色损失密切相关（R2＞0.95,p＜0.05）。在未经热烫和经热烫处理后冻干的菠菜其叶绿素降解的活化能分别为39.99 kJ/mol和41.44 kJ/mol。而用色度计测定的红绿值a*和色彩角值h中,经过热烫前处理的脱水菠菜其活化能分别是18.93 kJ/mol和48.08 kJ/mol,而未经烫漂的分别为18.20 kJ/mol和44.04 kJ/mol。与热烫处理的样品相比,未热烫的脱水菠菜更容易失去叶绿素,热烫处理有利于延长脱水菠菜的货架期。相同前处理的脱水菠菜,在设定的贮藏温度下,叶绿素降解、红绿值a*和色彩角值h的速率常数随贮藏温度的升高均逐渐增大,低温贮藏有利于延长脱水菠菜的货架期。在常温下（20℃）脱水菠菜的货架期为168 d（未热烫）或465 d（热烫）。     

Fate of prions in soil: Degradation of recombinant prion in aqueous extracts from soil and casts of two earthworm species

Prions represent the active agent in transmissible spongiform encephalopathy (TSE) diseases and can remain infective to mammals even after prolonged periods in soil. The influence of mesofauna on prion dispersal and degradation in soil, however, remains unknown. In this study the effect of earthworms on the retention/dissemination of TSEs in soil was evaluated using a model recombinant prion protein (recPrP) and aqueous extracts from soil and fresh casts of two earthworm species, Lumbricus terrestris and Aporrectodea caliginosa. Our results showed that earthworm gut-derived enzymes did not enhance the degradation of recPrP in comparison to soil, even though non-prion related proteolytic activity was higher in fresh worm excrements than in soil samples. Complete degradation of recPrP occurred in the aqueous extracts from all samples within up to 6 days at +15 °C. The proteolytic enzymes responsible for degrading recPrP were inhibited by aprotinin and leupeptin and studies in pure cultures suggested these were most probably of soil microbial origin.     

地衣芽孢杆菌降解水产养殖中残余饵料的特性研究

从土壤及饲料添加剂中筛选获得了一株能较高效降解水产养殖中残余饵料蛋白、淀粉的功能菌,经鉴定为地衣芽孢杆菌.通过研究养殖水体中饲料浓度、pH值、温度等因素对地衣芽孢杆菌降解饲料中蛋白质、淀粉的影响.结果表明,该菌降解饲料中蛋白质、淀粉的适宜条件为:饲料浓度≤5g/L,pH值6～7,温度25～30℃,盐浓度0～1%,溶氧浓度约4mg/L.地衣芽孢杆菌在这种水体生态条件下接种5%,饲料中的蛋白质与淀粉降解率约为60%.     

Thermal degradation modeling of flexural strength of wood after exposure to elevated temperatures

Abstract

Wood is being used heavily in single-family residential dwellings. Therefore, it is important to categorize their response when exposed to elevated temperatures for a sustained period of time. An important aspect of structural fire design is to assess postfire residual strength of existing structures. This study addresses this issue by developing models to predict strength degradation of wood after exposure to elevated temperature. The objectives were to (a) study the effect of exposure time on bending strength [Modulus of Rupture (MOR)] of wood at elevated temperatures, (b) interpret any relationships between different temperature and time of exposure using kinetics and a statistical approach, and (c) compare the two approaches. Two hundred thirty-two samples in total were tested in flexure as a function of exposure time and several temperatures. MOR of wood decreased as a function of temperature and exposure time. Rate of degradation was higher at higher temperatures. These results were fit to a simple kinetics model, based on the assumption of degradation kinetics following an Arrhenius activation energy model with apparent activation energy of 37.4 kJ/mol. A regression-based statistical model was also developed. The kinetics-based model fit the data better with one less parameter and predictions consistently matched the observed values, making the model preferred over the regression approach.     

砷污染区黄牛和水牛姐妹染色单体交换和细胞周期动力学的研究

本文以外周血淋巴细胞姐妹染色单体互换(SCE)频率和细胞周期动力学为指标,以较长期(4～13年)生活在砷污染区的黄牛和水牛为对象,对砷在动物体内慢性蓄积所诱发细胞遗传学效应进行了研究。其结果表明,砷污染区黄牛和水牛SCE频率均显著高于对照组,参照有关评价标准,可判为弱阳性,提示在当地污染水平下,黄牛和水牛都诱发了一定程度的细胞遗传学效应。对细胞周期动力学的观察结果表明,砷对黄牛和水牛没有明显的细胞毒性。本试验还报告了正常黄牛和水牛外周血液淋巴细胞SCE的自发频率以及培养72小时各期细胞的正常比率。     

土壤中积累态磷活化动力学的研究Ⅱ.沸石的影响

本文研究了NH4-沸石对潮土和红壤中积累态磷的活化动力学的影响。修正的Elovich公式和双常数速率公式对土壤中积累态磷的活化动力学拟合最好。土壤中添加了NH4-沸石后 ,土壤中积累态磷的活化释放明显增快。NH4-沸石有较强的释磷作用 ,可以促进土壤中积累态磷的活化释放。     

微贮对秸秆在瘤胃NDF降解率的影响

试验采用3个重复对比设计，将玉米，小麦和稻草秸秆的微贮样与原样放置在永久瘘管牛体内，分别在6．12、24．36、48和72小时时间点取出样本进行NDF降解率试验测定分析，结果：秸秆处理样NDF在各个时间点的NDF瞬间降解率和有效降解率均极显著优于原样（P＞0．01）而玉米秸秆处理样与小麦和稻草处理样相比差异不显著（P＞0．05）。     

微生物降解动力学参数估计新算法的比较

为了有效地估计较大范围变化的微生物降解动力学参数,发展了基于瞬时精英保护策略的遗传算法(IEPGA)和简单改进遗传算法(IGA),并和多次在参数区间内获取随机初值联用Matlab的lsqnonlin搜寻的算法进行了比较.这些算法利用模拟数据和文献数据,估计了积分形式的Monod模型参数.结果表明,虽然三者均能较好解决这一问题,但考虑到实际运行规模、时间以及最终结果精度,对于较大范围变化的微生物降解参数估计问题,多次(>20次)随机初值联用lsqnonlin的方法相对两种遗传算法更为可行.     

甘蔗品种抗旱性光合生理指标及其综合评价

利用相关、主成分、聚类和判别分析, 研究有关生理生化指标与甘蔗抗旱性关系. 结果表明: (1)中度水分胁迫下, MDA含量和PMP有不同程度地提高, 而Fv/Fm、 Fv/Fo、ΔFv/Fo、ΔFv/Ft和T1/2 有不同程度地降低, 变化的幅度因供试品种基因型而异. (2)PMP与MDA含量呈极显著正相关, 而与Fv/Fm、 Fv/Fo及ΔFv/Fo呈显著负相关; Fv/Fm与F     

Degradability of atrazine, cyanazine, and dicamba in methanogenic enrichment culture microcosms using sediment from the Pearl River of Southern China

Degradation of three herbicides, atrazine, cyanazine and dicamba, was assessed in laboratory microcosms incubated under simulated methanogenic conditions using sediment from Pearl River of Southern China as an inoculum. Atrazine was much more resistant to degradation than cyanazine and dicamba over 300 days of incubation. Biodegradation of cyanazine and dicamba was further substantiated by establishment of enrichment transfer cultures in which the degradation of the respective herbicide was accelerated by the active microorganisms. Degradation of cyanazine initially involved the removal of chlorine and the two side chains, while that of dicamba was O-demethylation reaction forming 3,6-dichlorosalicyclic acid. Results suggest that biodegradation of xenobiotics can be established through enrichment culture transfer technique, and further mechanism of degradation and microorganisms involved can be elucidated.