Population dynamics of the potato cyst nematode,Globodera pallida,in relation to temperature,potato cultivar and nematicide application

The impact of increasing temperatures on the population dynamics of the soil-dwelling nematode Globodera pallida, a persistent and economically important pest of potatoes, was investigated. The reproductive factor (final population⁄initial population) and length of life cycle were found to be temperature sensitive. Pot experiments performed over 4 months allowed comparison of the effect on development of G. pallida of two temperature regimes: an average temperature comparable to current field conditions (14.3 °C) and an average temperature above current field conditions (17.3 °C). A larger second generation of juveniles was observed at 17.3 °C compared to 14.3 °C. Multiplication of G. pallida at field sites in Shropshire and East Lothian (average soil temperatures of 15.5 and 14.1 °C, respectively, during potato cropping) was also examined. A quantitative PCR assay and visual examination of roots were used to monitor the dynamics of the G. pallida populations in both field sites at 4-weekly intervals. Four cultivars, Desirée, Cara, Maris Piper and Estima, were grown with and without nematicide treatments. Nematicide treatments suppressed population increases at both sites. Females were observed on the roots of cvs Cara and Desirée at the end of the growing season in Shropshire, but not at East Lothian, and are likely to represent a second generation.     

蒸汽烫漂与热风干燥箱流场优化设计及仿真

农产品的烫漂与干燥是农产品加工的关键技术。农产品蒸汽烫漂与热风干燥箱是集烫漂与干燥一体的新型农产品绿色保质低碳智能干燥技术装备。农产品蒸汽烫漂与热风干燥箱内部流场均匀性直接影响着农产品烫漂与干燥效果。为提高其内部速度均匀性与温湿度均匀性,同时减少冷凝现象发生,采用计算流体力学（computational fluid dynamics,CFD）方法建立蒸汽烫漂与热风干燥箱模型,对其送风方式和送风口数量进行研究。结果表明：侧送侧回的送风方式在速度场以及温湿度场的均匀性总体优于上送下回,能量利用系数提高约18%,箱内壁面冷凝面积小于上送下回。仿真研究表明,当送风口数量为4个时,箱内的温度场和相对湿度场均匀性更好,能量利用系数最高。试验表明,蒸汽烫漂与热风干燥箱的试验值和仿真值最大温度偏差为2.3℃,相对湿度误差不超过1.3%,误差在合理范围内,仿真结果可靠,研究结果可为农产品低碳智能干燥新技术的研究提供参考。     

市售氯硝柳胺在斑点叉尾组织中的残留消除规律研究

为了研究氯硝柳胺在斑点叉尾(Ictalurus punctalus)组织中的残留消除规律,在静水条件下经安全性试验确定安全浓度后,直接对水族箱泼洒25%氯硝柳胺乙醇胺盐(NES)粉剂后采集斑点叉尾皮肤、肌肉和水样。采用高效液相色谱-质谱联用法(HPLC-ESI/MS/MS)测定样品中氯硝柳胺的浓度,结果表明,静水条件下25%氯硝柳胺乙醇胺对斑点叉尾的安全浓度为0.113 mg/kg;养殖水环境中氯硝柳胺能快速消解,实验第2天即低于1μg/L,并呈无规律性持续较长时间;用药24 h内,氯硝柳胺在鱼体肌肉和鱼皮中具有较强的蓄积能力,但48 h后,其在鱼皮和肌肉中呈现快速消除至较低浓度,但后期消除缓慢,并会持续一定时间;氯硝柳胺(NIC)在斑点叉尾肌肉和鱼皮中的消除半衰期T1/2分别为10.66和9.24 d,显著大于在水体中的消除半衷期。     

Summertime and early autumn activity of some enzymes in the carbohydrate and fatty acid metabolism of the crucian carp

In June, July, and September the activities of five enzymes involved in the carbohydrate and fatty acid metabolism, namely phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), cytochrome oxidase (cyt ox) and 3-hydroxy-acyl-CoA dehydrogenase (HAD), were measured in the heart, liver, red muscle, white muscle, and gill lamellae of crucian carp (Carassius carassius). LDH activity was measured in both reducing (LDHr) and oxidizing (LDHo) directions.The PFK activity in red and white muscle increased significantly between July and September indicating a preparation to winter anoxia by an increased glycylytic capacity in these organs. The HAD activity of the liver had increased significantly (by more than 50%) by September, also a preparation to winter anoxia as HAD is used in the reversed -oxidation (chain elongation of fatty acids). The LDHr and cyt ox activities in the heart and white muscle were highest in July. This shows that both the anaerobic and aerobic capacities are elevated in mid-summer when water temperature is high and oxygen concentration of the water could fluctuate greatly. The LDHo and CS activities in gill lamellae were lowest in July. The results show that the metabolism of crucian carp is under seasonal influence and that a preparation to winter hypoxia/anoxia could be detected in September.     

基于多体接触碰撞的松软地面车轮沉陷仿真

提出了一种大规模多体系统接触碰撞理论与车辆地面力学理论相结合的仿真方法,并基于多体动力学仿真平台开发了车轮土壤相互作用仿真模块。基于该方法建立的土壤动力学模型和车轮土壤接触碰撞模型,进行了车轮沉陷的仿真。根据记录,在普通配置台式计算机上模拟土槽系统30 s的运动,仅需20 min。在相同实验条件下,仿真结果与土槽实验结果趋势一致,仿真曲线与土槽实验曲线吻合良好。由此表明该仿真算法能够满足越野行驶仿真的需要。     

纳米铜晶胞体积弹性模量变化规律的分子动力学模拟

用分子动力学的方法详细模拟纳米铜晶胞随温度与压强变化的规律,得到了铜晶胞体积弹性模量突变的敏感压强点.模拟结果表明:单晶铜的在压强小于75GPa时体积弹性模量随温度升高而降低,随压强增大而增大;在压强大于75GPa时,体积弹性模量随温度升高而增大,随压强增大而减小.     

Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland

The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield.     

Differential HSP90α expression in fish hepatocytes from polluted estuary during summer

The molecular chaperone, heat shock protein 90α (HSP90α), plays an important role in protein folding, degradation of denatured proteins and steroid activation. It is essential for the maintenance of cellular integrity and survival when induced in response to environmental, physical and chemical stresses. In the present investigation the effect of environmental stress on HSP90α expression was examined in grey mullet Mugil cephalus living in either a contaminated (Ennore) or uncontaminated (Kovalam) estuary over two seasons: Hepatocytes were isolated from grey mullet of both estuaries. Oxidative stress was determined along with HSP90α in these fish. Additionally, immunohistochemical changes were studied to confirm the HSP90α expression. Comparison of the results revealed enhanced hepatocyte oxidative stress and HSP90α expressions in fish from Ennore to a significant extent than fish from Kovalam. Also, the results showed significant seasonal variations with maximum expression observed during summer compared to the monsoon season. Overexpression of HSP90α in hepatocytes exposed to chronic environmental stress by pollutants may confer differential effects on cell survival by protecting against oxidative stress induced changes. The results also indicate that seasonal variations have significant effect on the HSP90α expression.     

油松大蚜的种群动态、有效积温及防治

通过野外调查和室内不同温度下饲养观察,对油松大蚜(Cinara formosana)生活史、种群动态、有效积温、天敌、物候预测和化学防治进行了研究。结果表明:油松大蚜1年可发生8代,6月中旬分化出有翅孤雌蚜并扩散,10月上旬性蚜交配产卵,以卵越冬;油松大蚜种群数量1年内有2个高峰期,分别在6月上旬和9月上旬,8月上旬—8月中旬种群数量最低;油松大蚜不同虫态的发生与山桃(Prunus davidiana)、连翘(Forsythia suspense)、龙爪槐(Sophora japonica)和火炬树(Rhus typhina)的一些物候相吻合,可通过观察这些植物的物候来预测油松大蚜各虫态发生情况;油松大蚜优势天敌依次为异色瓢虫(Leis axyridis)、七星瓢虫(Coccinella septempunctata)、蚜茧蜂(未鉴定);油松大蚜4个龄期的若虫及全世代的发育起点温度分别为4.5、6.7、5.9、7.7、3.1℃,有效积温分别为48.6、49.3、67.4、62.7、291.7日·度;胶带-药膜法防治油松大蚜效果显著,14 d后处理区校正虫口减退率可达80%以上。     

不同通风形式日光温室湿热特性的数值模拟

研究日光温室不同通风形式对室内湿热特性的影响。采用计算流体动力学数值模拟方法,构建日光温室作物-环境湿热系统的数值模拟模型。将模拟结果与试验测量结果进行对比,温度和相对湿度的模拟值与实测值的最大相对误差分别为4.7%和4.1%,验证了所构建模型的准确性。应用该模型模拟不同通风形式下温室内的气流和温湿度分布情况,比较分析不同的通风形式对室内湿热特性的影响。结果表明：不同的通风形式会影响室内气流的运动轨迹和速度,从而影响室内温度和相对湿度的分布变化。仅开启上通风口通风时,室内的平均温度和相对湿度较高,气候分布均匀,整体变化较小,适宜冬春季节或清晨傍晚室内温湿度较低时的通风要求;仅开启下通风口通风时室内温湿度分布模式均匀性最差,进风口处的温湿度明显低于北墙,且进口存在涡流,不利于作物生长发育;上、下通风口均只开一半通风时,作物区平均温度和相对湿度分别为39.3℃和25%,上、下通风口均全开时作物区平均温度和相对湿度为36.8℃和23.7%,较于前者室内温度和相对湿度分别降低了2.5℃和1.3%,适宜于炎热天气下日光温室内的降温除湿要求。