基于电子鼻的带鱼货架期预测模型

为探索通过气味分析判断海产品贮藏品质的方法,利用电子鼻对带鱼在不同贮藏温度与贮藏时间下的挥发性气味变化进行了分析,对所获数据进行了主成分分析与货架期分析,并与理化品质指标值挥发性盐基氮（total volatile basic nitrogen,TVBN）相联系,建立了带鱼在273～283 K下的货架期预测模型。结果表明：电子鼻18个金属传感器能很好地将贮藏于273与283 K下的带鱼随着贮藏时间变化的气味进行区分。贮藏于不同温度条件下的带鱼的TVBN值与菌落总数值均随着贮藏时间的增加而增长,且均符合一级化学动力学模型（R2＞0.9）。基于电子鼻货架期分析获得的273～283 K下的气味变化结果与该温度下理化品质指标变化具有较好的对应关系,采用Arrhenius动力学模型推导公式求得带鱼在（273～283 K）温度段内TVBN的Q10（温差为10 K的货架寿命之比）值,对照该温度段下电子鼻货架期分析获得的气味变化货架期分析值,得到带鱼在该温度段内的Q10货架期预测模型,经验证,其预测误差小于20%。可根据获得的货架期预测模型对带鱼在273～283 K条件下的货架期进行预测。     

Characterization of Elemental Species in PM2.5 Samples Collected in Four Cities of Northeast China

A monitoring program of particulate matter was conducted at eight sampling sites in four highly industrialized cities (Shenyang, Anshan, Fushun, and Jinzhou) of Liaoning Province in Northeast China to identify the major potential sources of ambient PM_2.5. A total of 814 PM_2.5 and PM_2.5–10 samples were collected between 2004 and 2005. All PM samples were collected simultaneously in four cities and analyzed gravimetrically for mass concentrations. A sum of 16 elemental species concentrations in the PM samples were determined using inductively coupled plasma atomic emission spectroscopy. Annual means of PM_2.5 concentrations ranged from 65.0 to 222.0 μg m^?3 in all the eight sampling sites, and the spatial and seasonal variations were discussed. Enrichment factors were calculated, and Cr, Cu, Zn, As, Cd, and Pb will be pollution-derived elements. Site-to-site comparisons of PM_2.5 species in each city were examined using coefficient of divergence, revealing that the two sites in each city are similar in elemental species. Principle component analysis was used for preliminary source analysis of PM_2.5. Three or four factors in each city were isolated, and similar sources (crustal source, coal combustion, vehicle exhaust, iron making, or some other metallurgical activities) were identified at four cities.     

大豆胞囊线虫相关G2-like转录因子生物信息学分析

G2-like转录因子在植物中广泛存在,是GARP转录因子超家族中重要成员之一,在叶绿体发育、果实生长、生物或非生物胁迫和植物衰老等方面均起重要作用.研究对大豆胞囊线虫3号生理小种胁迫下东农L-10(抗病)根部进行转录组测序,初步筛选得到8个与大豆胞囊线虫抗性相关G2-like转录因子,并通过在线软件对其作生物信息学分...     

不同工况下柴油机活塞变形的三维有限元分析

为了考察各种工况因素对柴油机活塞工作时变形的影响情况,以某4105型号柴油机活塞为对象,采用三维有限元分析方法,分别就各种工况因素对活塞变形的影响进行分析。结果表明,在机械负荷作用下,随着柴油机负荷或转速的增加,活塞的变形也相应的增大,活塞的最大变形均发生在活塞主推力面裙部下沿位置;在热负荷作用下,随着柴油机负荷的增加,活塞的变形也相应的增大,而此时转速差异对活塞变形的影响不是很明显,整个活塞的最大热变形发生在活塞顶部靠近排气口一侧边缘;活塞在机械—热负荷耦合作用下的变形情况与在机械负荷作用下分析得到的结果相似。该结果可以为活塞的结构改进和优化设计提供参考依据。     

参考作物蒸发蒸腾量计算方法在海河流域的适用性

参考作物蒸发蒸腾量（ET0）的计算公式很多,各公式所需参数各异,为寻找一种所需资料少而又精度较高的替代方法,选用1998年FAO-56分册推荐的Penman－Monteith（PM）、Hargreaves、Irmark-Allen等6种方法分别计算海河流域10个典型气象站30 a的参考作物蒸发蒸腾量,并以PM公式为标准,对其他方法进行评价。结果表明,10个站点中除了五台山地区,Hargreaves与FAO-24 Radiation 这2种方法更接近于PM方法的计算结果,其误差较小,在海河流域缺少辐射和风速     

Anti-inflammatory effects of caper (Capparis spinosa L.) fruit aqueous extract and the isolation of main phytochemicals

Caper (Capparis spinosa L.) fruits have been used as food as well as folk medicine in the treatment of inflammatory disorders, such as rheumatism. The present study was carried out to study the anti-inflammatory activities of C. spinosa L. fruit (CSF) aqueous extract and to isolate main phytochemicals from its bioactive fractions. The CSF aqueous extract were separated into three fractions (CSF1-CSF3) by macroporous adsorption resins. The fractions CSF2 and CSF3 effectively inhibited the carrageenan-induced paw edema in mice. Systematic fractionation and isolation from CSF2+3 led to the identification of 13 compounds (1-13). Their chemical structures were elucidated by spectroscopic analyses including nuclear magnetic resonance (NMR) and mass spectrometry (MS) and literature comparisons. Major compounds found in the bioactive fraction CSF2+3 are flavonoids, indoles, and phenolic acids. To our knowledge, 8 of these 13 compounds (1-4, 6-7, 10, and 13) were identified from caper fruits for the first time. The anti-inflammatory effects of these purified compounds are currently under investigation.     

生存与保障:集市对集市相关利益群体的重要性——基于对青岛李村大集的个案研究

集市作为基层市场,是满足社会低收入群体基本生活需求的主要场所。在这里,笔者把以谋生为目的,从事集市职业的这类群体称之为集市谋生群体,经常在集市这个场域中消费的这一类群体称之为集市消费群体。集市谋生群体与集市消费群体在集市中进行贸易往来,通过交换获得满足自身需要的用品,集市是谋生群体与消费群体的生存的场域空间之一。但是,随着城市化的推进,集市受到了城市化张力的排挤,低层次集市的发展受到了极大地制约,有的集市甚至被予以取缔,集市谋生群体、集市消费群体的利益受到了极大侵害。本文主要从集市谋生群体、集市消费群体的自身特点,来说明集市对其存在的现实意义。     

养殖场的选址和布局

养殖场的选址和布局选址是养殖环节的重要前提和基础性工作,合理的选址与布局为家畜和管理人员创造良好生产和生活环境,合理的利用自然资源和社会资源,避免了不必要的损失.     

地膜玉米栽培及病虫害防治要点分析

首先从分做好播前准备、品种选择、精细整地、铺膜播种、田间管理和收获6个方面阐述了地膜玉米高产栽培技术,然后对地膜玉米病虫害防治进行了简单的探讨。     

Quantitative structure-activity relationships of monoterpenoid binding activities to the housefly GABA receptor

BACKGROUND: Monoterpenoids are a large group of plant secondary metabolites. Many of these naturally occurring compounds have shown good insecticidal potency on pest insects. Previous studies in this laboratory have indicated that some monoterpenoids have positive modulatory effects on insect GABA receptors. In this study, the key properties of monoterpenoids involved in monoterpenoid binding activity at the housefly GABA receptor were determined by developing quantitative structure‐activity relationship (QSAR) models, and the relationship between the toxicities of these monoterpenoids and their GABA receptor binding activities was evaluated. RESULTS: Two QSAR models were determined for nine monoterpenoids showing significant effects on [³H]‐TBOB binding and for nine p‐menthane analogs with at least one oxygen atom attached to the ring. The Mulliken charges on certain carbon atoms, the log P value and the total energy showed significant relationships with binding activities to the housefly GABA receptor in these two QSAR models. CONCLUSIONS: From the QSAR models, some chemical and structural parameters, including the electronic properties, hydrophobicity and stability of monoterpenoid molecules, were suggested to be strongly involved in binding activities to the housefly GABA receptor. These findings will help to understand the mode of action of these natural insecticides, and provide guidance to predict more monoterpenoid insecticides. Copyright © 2012 Society of Chemical Industry