沙生针茅种子萌发特性及其影响因素

利用控制试验研究了不同温度蒸馏水水分、盐分胁迫等生态因子对沙生针茅种子萌发的影响,探索了沙生针茅种子对各种生态因子的适应性。结果表明:(1)蒸馏水浸泡种子,以60℃温水浸泡、自然降温至常温12h最好;(2)低温处理与未经低温处理的种子发芽率差异不显著(P0.05),说明沙生针茅种子不存在生理后熟因素影响;(3)随着PEG-6000浓度的增加,沙生针茅种子的发芽率、发芽势、发芽指数呈下降趋势,种子发芽率的PEG-6000浓度的临界值和极限值分别为15.9%和26.3%;(4)沙生针茅种子的发芽率、发芽势、发芽指数随着盐分浓度的增加呈下降趋势,其中Na2CO3处理下的沙生针茅种子萌发率下降幅度明显大于NaCl,表明沙生针茅种子对相同质量浓度的Na2CO3的耐受能力显著低于对NaCl的耐受能力。     

VH1-44 gene usage defines a subset of canine B-cell lymphomas associated with better patient survival

The use of specific immunoglobulin heavy chain variable region (VH) genes has been associated with increased patient survival in human B-cell lymphomas (hBCL). Given the similarity of human and canine BCL (cBCL) in morphology and clinical treatment, we examined the choice of VH in cBCL and determined whether VH gene selection was a distinct feature associated with survival time in dogs. VH gene selection and mutational status in 52 cBCL, including 29 diffuse large B-cell lymphomas (cDLBCL, the most common subtype of cBCL), were analyzed by comparison with the 80 published canine germline VH gene sequences. We further examined the prognostic impact of the subgroups defined by these features on canine survival. We found that VH1-44 was preferentially expressed in the majority of the 52 cBCLs (60%) as well as in the majority of the cDLBCL subset (59%). VH1-44 gene expression was associated with a statistically better overall survival (p = 0.039) in cBCL patients, as well as in the cDLBCL subset of patients (p = 0.038). These findings suggest that VH gene selection in cBCL is not random and may therefore have functional implications for cBCL lymphomagenesis, in addition to being a useful prognostic biomarker.     

Nest site selection of white-naped crane （Grus vipio） at Zhalong National Nature Reserve,Heilongjiang, China

White-naped crane （Grus vipio） is a globally threatened spe- cies. It is very important to analyze its nest site selection in circum- stances where there are multiple disturbances, and also helpful to accu- mulate valuable information about this threatened species and supply scientific suggestions for conservation and management. We studied nest site selection and the effects of environmental variables on nesting habits of white-naped crane at Zhalong National Nature Reserve, Qiqihar City, Heilongiiang, China, during March-May of 2002-2008. White-naped crane responded and adapted to changes in the quality of the spatial environments of landscape and microhabitat under multiple environ- mental disturbances. Nest site selection included two scales and two choices, namely the choice of nest site habitat type within the macro-habitat scale and nest site micro-habitat selection within the mi- cro-habitat scale. Nest sites were recorded only in reed marshes. The choice of nest site micro-habitat included three basic elements and six factors, namely incubation element （nest parameters factor, incubation temperature factor and incubation humidity factor）, safety element （pro- tection factor and concealment factor）, and food element （water factor）. Water, remnant reed clusters, and fire were major resource management challenges during the breeding period for the white-naped crane in this Reserve.     

Effect of Crop-Straw Derived Biochars on Pb(Ⅱ) Adsorption in Two Variable Charge Soils

Two variable charge soils were incubated with biochars derived from straws of peanut, soybean, canola, and rice to investigate the effect of the biochars on their chemical properties and Pb（II） adsorption using batch experiments. The results showed soil cation exchange capacity （CEC） and pH significantly increased after 30 d of incubation with the biochars added. The incorporation of the biochars markedly increased the adsorption of Pb（II）, and both the electrostatic and non-electrostatic adsorption mechanisms contributed to Pb（II） adsorption by the variable charge soils. Adsorption isotherms illustrated legume- straw derived biochars more greatly increased Pb（II） adsorption on soils through the non-electrostatic mechanism via the formation of surface complexes between Pb（II） and acid functional groups of the biochars than did non-legume straw biochars. The adsorption capacity of Pb（II） increased, while the desorption amount slightly decreased with the increasing suspension pH for the studied soils, especially in a high suspension pH, indicating that precipitation also plays an important role in immobilizing Pb（II） to the soils.     

几个杨树品种低温与变温胁迫对比试验

以几种常见杨树品种为试材,在不同时期进行了低温胁迫试验,通过相对电导率测试及生长恢复情况调查,分析了不同时期低温对杨树发生冻害的影响,结果显示：在冬季树木深休眠期持续的低温对杨树具有一定的伤害,但伤害程度不大;初春树木萌动期低温对杨树伤害较大。根据此结论,进一步开展变温胁迫试验,结果显示：高温和低温的变温对不同杨树伤害较大,而且变化幅度越剧烈,造成伤害越严重。     

热压工艺参数对三聚氰胺饰面刨花板甲醛释放量的影响

以市售刨花板和三聚氰胺浸渍纸为原料,制备三聚氰胺饰面刨花板.采用L9（34）正交试验考察热压温度、热压时间、热压压力3个热压工艺参数对三聚氰胺板甲醛释放量的影响.采用国家标准（GB/T 17657-1999）《人造板及饰面人造板理化性能试验方法》干燥器法检测甲醛的释放量.试验结果表明,热压温度对甲醛释放量影响最大、热压时间其次、热压压力影响最小,其中热压温度对甲醛释放量有显著影响,热压时间和热压压力的影响并不显著.热压工艺参数提高,会引起热压后的三聚氰胺板前期的甲醛释放量明显升高.确定饰面刨花板甲醛低释放的最优化生产工艺参数为热压温度170℃、热压时间40s、热压压力2.5 MPa.     

高速公路可变限速控制算法研究

高速公路可变限速控制是减少拥挤和事故发生的有效方法,是近年来高速公路研究领域的热点．对高速公路可变限速控制算法进行综述分析,根据控制区域的不同将算法分成主线可变限速控制和主线与匝道可变限速协调控制两大类,从这两大类算法出发,分别总结不同算法的应用现状,指出目前研究中存在的主要问题,结合最新成果对未来研究的方向进行分析．     

小型无人机机载农药变量喷洒系统设计

基于脉宽调制（Pulse Width Modulation,PWM）技术设计小型无人机机载农药变量喷洒系统,主要由药 箱、喷头、液泵及喷洒控制器组成,通过调整PWM 喷洒控制信号的占空比,改变液泵的工作时长,从而实现变量喷 洒。基于常量喷洒流量指标和机载喷洒系统的覆盖范围,确定PWM 频率为1 Hz,并建立了该频率下占空比与喷洒流 量之间的3 次多项式关系模型,模型决定系数达到0.9944。以关系模型为指导,分别测试了0.3、0.4、0.5 L/min 流量控 制指标下的变量喷洒试验效果,喷洒值和目标值之间误差分别为8.66%、4.50%和1.60%,达到变量喷洒控制的目的。     

铜离子吸附对可变电荷土壤与恒电荷土壤铝释放的影响

研究了两种可变电荷土壤和两种恒电荷土壤在不同铜离子浓度条件下,pH对铝释放的影响.结果显示,随着加入铜离子浓度的增加,由铜离子交换作用而引起的可溶性铝也随之增加,相同pH条件下,可溶性铝的解吸量依次为砖红壤＞红壤＞黄棕壤＞棕壤,恒电荷土壤中铜离子浓度变化对铝释放的影响较可变电荷土壤更大,当pH大于3.6(恒电荷土壤)或pH大于4.0(可变电荷土壤)时,溶液中可溶性铝的含量几乎可以忽略不计.因此在所研究的铜离子浓度范围内,引起可溶性铝离子量变化的主导因素应该是体系pH值的变化而非铜离子的吸附.     

地理集聚与农业国际竞争力的相关性研究——来自我国水果产业的证据

以我国水果产业为研究对象,利用1992要2012年的相关数据,采用产业集中率和显示性比较优势指数分别测算了5种主要水果作物和水果产业的地理集聚度与国际竞争力。在此基础上,构建固定影响变系数模型,定量分析了我国水果产业地理集聚与国际竞争力之间的相关关系。结果表明,整体来看,我国水果产业地理集聚与国际竞争力存在显著的正相关关系,苹果、梨、柑橘产业的地理集聚有利于促进国际竞争力的提高;香蕉和葡萄产业的地理集聚与国际竞争力存在负相关关系,可能的原因是加入WTO后葡萄和香蕉出口环境的变化以及香蕉和葡萄主要供应国内消费的现实情况。最后,结合本文的研究内容和研究结论,就相关研究领域提出了几点思考。