磁处理对大蒜胚性愈伤组织生长和体胚发生的影响

以大蒜为试材，研究了磁处理对其胚性愈伤组织生长和发生的效应。结果表明：在0．23T磁感应强度下，0－20min之间的磁处理对大蒜胚性愈伤组织的生长和增殖影响不明显，磁处理时间超过20min后，明显对愈伤组织的生长和增殖产生抑制或破坏作用。5min磁处理能显著地促进大蒜体胚的发生和发育，在10－80min内，随磁处理时间延长，平均每克鲜物质体胚数呈缓慢递增趋势，5－10min磁处理的体胚发育状态更趋成熟。     

农村公路的现状和发展规划研究

以湖北省公安县公路养建情况为例，对农村公路的基本概况与管养体制进行了分析，提出了公安县农村公路建设的发展建设和未来10年的发展规划。     

关于Lapicunaxa属分类地位的商榷——蜱螨亚纲、真螨目、巨须螨科

曾义雄1980年发表了巨须螨科(Cunaxidae Thor,1902)的一个新属Lapicunaxa,但属以上的分类地位一直未确定。根据J.Den Heyer(1980)的新分类系统和作者的研究认为,该属似应上升为亚科,定名为叠板巨须螨亚科La-picunaxinae。     

超低温（LN2,—196℃）贮存牧草种子初探

在牧草种子的贮存过程中，最重要且最难于解决的问题就是克服所贮存种子的生理衰变。超低温技术（LN2，于－196℃条件）可以将种子内部新陈代谢降低到一个很低的水平，使所有的生化过程处于“停顿”状态，这样便可以大大延长种子的贮存寿命。本实验将9种在常规条件下难于保持活力的牧草种子放入液氮中贮存一年，解冻后测定贮存种子的发芽率、发芽指数、电导率、呼吸强度及ATP含量情况。结果表明，禾本科、豆科、藜科牧草种子属于液氮耐受类型，特别是短命种子驼绒藜与木地肤对液氮贮存表现特别适应。     

我国图书馆员职业化进程缓慢的原因及对策

中国图书馆界一直在提倡图书馆员职业化,但国内图书馆员的职业化进程仍旧非常缓慢,甚至某些地区还有去职业化倾向。从图书馆员本身、其他行业人员、教育体制、相关管理部门4个角度分析了图书馆员职业化进程缓慢的原因,并对症下药,根据不同原因,提出了不同的改进措施,以期能加快图书馆员职业化的进程。     

四株玉米秸秆快速降解菌的分离与鉴定技术研究

筛选出了四株能够快速降解玉米秸秆中纤维素和半纤维素的菌株,经初步鉴定该菌株为类芽孢杆菌属(Paenibacillus spp.),未定种.     

Regulatory pathways controlling the endovascular invasive trophoblast cell lineage

Hemochorial placentation is characterized by trophoblast-directed uterine spiral artery remodeling. The rat and human both possess hemochorial placentation and exhibit remarkable similarities regarding the depth of trophoblast invasion and the extent of uterine vascular modification. In vitro and in vivo research methodologies have been established using the rat as an animal model to investigate the extravillous/invasive trophoblast lineage. With these research approaches, two signaling pathways controlling the differentiation and invasion of the trophoblast cell lineage have been identified: i) hypoxia/hypoxia inducible factor and ii) phosphatidylinositol 3-kinase/AKT/Fos like antigen 1. Dissection of these pathways has facilitated identification of fundamental regulators of the invasive trophoblast cell lineage.     

3种散生竹的单根抗拉力学特性

植被在改善生态环境、减少水土流失、涵养水源、固土护坡等方面具有其他工程措施所不能替代的作用.现有研究表明,植物根系对土壤的力学作用,能够稳定土层结构、提高土壤的抗剪强度,是植被实现固土护坡的重要手段(Roering et al.,2003;李绍才等,2006;吕春娟等,2011). 林木根系的抗拉力学特性是影响根系固土护坡效果的重要因素(陈丽华等,2008).植物根系由众多单根构成,单根是发生根土力学作用的基本单元,单根的抗拉能力及抵抗形变能力决定了植株受外力时的整体形变状态及对土壤的约束能力,因此,具有较大抗拉强度的单根构成的根系将有助于土壤的稳固和增强.     

基于超级电容—液钒电池平滑直驱风电系统出力

风电作为环境友好型电源在电网中的渗透率不断增大,其输出功率的波动性和间歇性对电力系统电能质量及其运行稳定性将产生重大影响;同时,电网故障也会给风电系统带来一系列的暂态过程。文章将高压大功率三电平变换器应用到直驱风电系统,为了抑制风电机组输出功率波动及电网故障对风电的不利影响,本文针对储能型并网永磁直驱风力发电系统的运行特点,提出了一种可行的综合控制策略,在风电机组输出功率较为平滑的同时,还具有较强的低电压穿越能力,使风电系统在电网故障时能保持正常运行。仿真结果很好地验证了所提出的控制策略的正确性和有效性。     

Spatial variability in soil heat flux at three Inner Mongolia steppe ecosystems

Closing the energy budget at flux measurement sites is problematic, even when the fetch extends over flat, homogeneous surfaces with low vegetation cover. We used the residual energy balance and ordinary least square (OLS) linear regression methods to quantify spatial variability in soil heat flux contributing to energy balance closure (EBC), by deploying a mobile energy system within the footprints of three Eddy-covariance towers located in the steppe of Inner Mongolia, China. The EBC at the study sites had a daily average residual of 8–19 W m⁻² with OLS slopes of 0.83–0.96. The EBC was better achieved at the wet site than at the dry site. The spatial variability in soil heat flux was 48 W m⁻² (13% of R_n) during the day and 15 W m⁻² (34%) at night, with an average of 29 W m⁻² (24%) across the three sites. A 9% OLS slope difference due to this variability was recorded from our eight plot measurements. A large amount of missing energy (110 W m⁻² at peak) could occur with decreasing OLS slope of 23% across the three grassland sites when soil heat flux is not taken into account. In particular, heat storage in the top soil layer not only influenced the magnitude of EBC, but also adjusted soil heat flux to match the ‘truth schedule’. Heat storage in the top soil layer comprised half of the soil heat flux when the heat flux plate was deployed at a depth of 30 mm. If this part of heat storage was neglected, the residual of EBC would increase as large as 60 W m⁻² with OLS slope decreasing 9%. Comparing them with the multiple-location soil heat flux measurements, the single-location measurements from near the Eddy-covariance towers obtained a slightly better EBC with the OLS slope increasing by 4%.