Beaver dams,streamflow complexity,and the distribution of a rare minnow,Lepidomeda copei

Freshwater fishes are threatened globally, and often too little is known about threatened species to effectively guide their conservation. Habitat complexity is linked to fish species diversity and persistence, and degraded streams often lack habitat complexity. Beaver Castor spp., in turn, have been used to restore streams and increase habitat complexity. The northern leatherside chub Lepidomeda copei is a rare, small‐bodied, drift‐feeding minnow that has anecdotally been observed to use complex habitats associated with beaver dams in the western United States. To investigate this anecdote, we conducted fish and habitat surveys, the latter focusing on quantifying habitat complexity, in a sub‐basin of the Upper Snake River Basin in the USA. Complementary generalised linear model and path analyses revealed that northern leatherside chub occurred more often at sites with complex streamflows, and streamflows were more complex when beaver dams were present and pools were deeper. Northern leatherside chubs were also more likely to occur when temperatures were warmer, aquatic macrophytes were abundant and stream channels were narrow and deep. The linkage between chubs, complex streamflows and beaver dams needs to be evaluated more broadly to completely understand its role in the rangewide status of the species. However, it does suggests that increased use of beaver reintroductions and dam analogues for stream restoration could be a boon for the northern leatherside chub, but such efforts should be monitored to determine their effectiveness to help adapt beaver‐based restoration approaches to best benefit the species.     

硅藻土杀虫剂处理后储粮害虫成虫体重减轻与死亡

研究了硅藻土杀虫剂“普粮泰”对米象、谷蠹、玉米象和锯谷盗成虫体重的影响。在30±1℃、65%±1%RH条件下,试虫分别在0.5~8 g/m2的粉剂药膜上处理1天,它们(顺序同上)的平均体重分别减少了0.1、0.4、0.2和0.2 mg/头,在相同条件下培养7天后,它们的平均死亡率分别为52%、100%、97%和100%。在25±1℃、65%±1%RH条件下,经过1 g/m2粉剂药膜处理锯谷盗1天后,在原条件下不提供食物保持3天,平均每头锯谷盗体重比对照减少了0.2~0.3 mg/头,平均死亡率达到76%。由此可见,硅藻土杀虫剂处理的储粮害虫成虫体重明显减少(P<0.05),死亡率很高,说明硅藻土杀虫剂可能破坏了试虫体壁保持体内水分的蜡质层,从而引起锯谷盗失水干燥而死。     

稀土对阿尔巴斯白绒山羊瘤胃发酵,消化代谢及其生产性能的影响

实验１用４只安装永久性瘤胃漏管的阿尔巴斯白绒山羊（母），进行瘤胃消化代谢试验；实验２用６只成年母绒山羊进行消化代谢试验；试验３选用同品种成年妊娠母羊进行放牧补饲实验。实验１得出，稀土的使用可促进瘤胃内ＮＨ３－Ｎ的利用；细菌数比对照组提高３５．６７％；丙酸产量提高２８．６３％。实验２得出，稀土可提高绒山羊日粮ＤＭ、ＯＭ、ＧＥ及ＡＤＦ消化率，分别为１１．５８％、１２．２７％、１６．６９％和２６．２９％；每日氮存留率比对照组提高１８０．１％。实验３得出，稀土组产绒量比对照组提高８．９０％。     

镧素对镰刀菌Fusarium solani及其致病酶的影响

采用琼脂平板生长速率法及液体培养基培养测定了La对镰刀菌Fusarium solani的抑制作用和毒力,并测定了其对病菌胞外的果胶酶、蛋白酶和纤维素酶等几种致病酶活性的影响。结果表明,随着La2O3浓度升高,对病菌菌丝生长的抑制作用增强,对病菌的EC50和EC95分别为278.2和552.0 mg/L;在一定浓度范围内,La提高了单位量菌丝所产生3种致病酶的活性,但由于菌丝生长受到抑制,除蛋白酶外,病菌胞外致病酶果胶酶和纤维素酶的总量或总活性受到了抑制,降低了病菌的致病力。     

稀土对刺槐苗木生理特性影响的研究

稀土对刺槐苗木生理特性影响的研究赵兰勇，梁玉堂（山东农业大学林学院泰安２７１０１８）王九龄（北京林业大学北京１０００８３）关键词稀土，刺槐，光合速率，叶绿素含量，水分利用效率，矿质元素含量近年来，稀土元素在农业上的应用研究越来越受到人们的重视，并且已...     

稀土元素铈对‘红地球’葡萄组培苗生长的影响

 以‘红地球’葡萄组培苗茎段为外植体，在培养基中添加1～100 mg·L^-1 Ce(NO₃)₃，，研究 不同浓度Ce(NO₃)₃对其生长的影响。结果表明适宜浓度的Ce(NO，)，(1～10 mg·L^-1 )对‘红地球’葡萄组培苗的生长具有促进作用，加快外植体生根，侧根数及侧根总长显著增加,根、茎、叶鲜样质量和干样质量也增加，根系活力提高而增加移栽成活率，增加叶绿素含量，有利于植株对矿质营养的吸收。而100 mg·L^-1。Ce(NO₃)₃对葡萄组培苗生长起明显抑制作用。     

砌石拱坝加高倍厚的三维接触仿真

对砌石拱坝的加高倍厚中新、老坝体结构面，用有限元软件ANSYS结合接触理论进行计算，并分析结果得出：温升、水压力和淤沙压力使结合面上的接触压力增大，从而接触摩擦应力较大，有利于结合面的结合，而结合面在温降的作用下有脱离的趋势。     

Physical simulation of fluid field and structure optimization in two-strand tundish

The influence of the structure and location of dam and weir on fluid flow state in a two-strand tundish is studied, and a set of optimal structure, combining with the average residence time calculated from RTD curve, is obtained. The result indicates that the fluid flow state can be changed and the path of the fluid flow can be prolonged as well as the average residence time is improved after using dam and weir. But there are some dead zones after fluid passed through the dam and weir. Combination scheme of No. one dam and weir is better than the others. Its average residence time is 299 s and the volume fraction of dead zone is 31.0%. After the optimization of flowing control parameters in tundish, the best case is that the distance between dam and weir is 290 mm and the distance between weir and the long nozzle is 383 mm. The longest average residence time is 351 s and the minimum volume fraction of dead zone is 19.0% under the above situation. Compared with that of no dam and weir, the average residence time increases by 65 s and the dead zone volume fraction decreases by 15.0%. Based on Newton formula, the calculated results show that the inclusions with diameter larger than 17.5 μm can float up within 351 s under this optimization situation.     

Application and Advancement of Reinforced Earth Technique

In this paper, the application of reinforced earth technique, principle and calculation method, new reinforced materials developed and produced are introduced. A few of key technical problems in reinforced earth application is discussed, such as reinforced earth behavior, calculation method, durability of reinforced material, amendment and complement of the current standards. Then, the reinforced earth technique development and advancement were introduced.     

Research on Design Methods for Reinforced Earth Retaining Wall with Cohesive Backfill

For the stability analysis of the reinforced earth retaining wall with cohesive backfill, this paper assumes that the state of failure surface is circular sliding surface and the bearing capacity is straight line relation with capacity and length of the reinforcement strip. These formulas agree with actual state of the reinforced earth retaining wall with cohesive backfill and result in saving reinforcement material in the design.