Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： Dynamic response of an end-bearing pipe pile subjected to transient torsional loading in layeredsaturated soil is theoretically studied in this paper. First , Biot's wave equation is decoupled by recourse toLaplace transform technique and separation of variables , and a series of distributed linear springs are uti-lized to simulate the dynamic interaction between the soil layers.By combined with the continuity andboundary conditions of pile-soil interface, the torsional dynamic response of an arbitrary pile segment isfurther derived in the transformed domain. Then, according to the principle of the recursion of impedancefunctions and by means of inverse Laplace transform , the time-domain solutions of pipe pile under transienttorsional loading embedded in a layered saturated soil are finally obtained. Numerical results show that thetime coresponding to maximum twist angle atop the pile lags behind that of maximum loading when subjected to triangular or semi-sinusoidal loads. The twist angle atop the pile almost remains constant in thecase of outer soil with relatively high or low permeability coefficients , whereas it gradually increases in themiddle range of the permeability. The hard interlayer soil increases the torque of upper part of the pile anddecreases that of the lower part , while the effect of soft interlayer soil is inverse.
Subjects: Geosciences >> Geography submitted time 2020-12-17 Cooperative journals: 《干旱区研究》
Abstract：松叶猪毛菜（Salsola laricifolia）是典型的荒漠C3-C4中间型植物，隶属于藜科（Chenopodiaceae）猪毛菜属，是研究C4途径进化以及光呼吸减少机制的最佳物种。以松叶猪毛菜无菌苗为试验材料，通过农杆菌介导的瞬时转化方法，分别对质粒载体、苗龄、农杆菌侵染浓度、侵染时间和乙酰丁香酮浓度进行研究，探究各因素对松叶猪毛菜植株瞬时遗传转化效率的影响，以确立最佳的瞬时转化体系；并在上述体系的基础上，过表达松叶猪毛菜叶绿体型NADP-苹果酸酶基因（SaNADP-ME1），通过GUS组织化学染色和荧光定量PCR验证瞬时转化效果。结果表明：（1）采用pCAMBIA1301构建表达载体，以30 d苗龄植株作为转化受体，在侵染液中添加200 μmol·L-1乙酰丁香酮，农杆菌菌液OD600为0.8，侵染6 h条件下，瞬时转化效率最佳（92%）；（2）构建过表达载体并瞬时转化松叶猪毛菜植株，通过染色检测到GUS活性，并且荧光定量PCR检测到SaNADP-ME1的表达量相比对照组显著增高，该基因成功瞬时过表达转化至植株中。综上所述，本试验在松叶猪毛菜植株中建立了一种快速基因功能验证方法，为以后研究松叶猪毛菜功能基因奠定了基础。
Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Basic Disciplines of Agriculture submitted time 2017-11-07 Cooperative journals: 《中国生态农业学报》
Abstract：为阐明不同类型玉米自交系氮效率差异特征, 筛选氮高效的玉米自交系, 以陕A 群、陕B 群选育的33 份玉米自交系为材料, 以4 份骨干自交系(‘郑58’、‘昌7-2’、‘PH6WC’和‘PH4CV’)为对照, 调查了2 种施肥条件下[0 kg(N)·hm2、180 kg(N)·hm2]玉米自交系的穗位叶SPAD 值、叶面积、干物质积累量、叶片、茎秆和籽粒氮含量等生理指标。利用主成分分析和模糊隶属函数, 采用逐步回归分析方法建立最优回归方程, 筛选耐低氮性综合评价指标。结果表明: 穗位叶SPAD 值、吐丝期绿叶面积、吐丝期茎干重、吐丝期叶干重和籽粒氮含量, 可作为玉米自交系耐低氮能力的第2 性状筛选指标。以产量作为第1 性状指标, 可将37 份玉米自交系划分为14 份高产氮高效型, 5 份低产氮高效型, 15 份低产氮低效型和3 份高产氮低效型。以耐低氮能力综合值D 值筛选, 将37 份玉米自交系可分成3 种类型, 其中耐低氮能力较强的15 份(D 值≥0.5), 耐低氮能力中等的15 份(0.35≤D 值<0.5), 耐低氮能力较差的7 份(D 值<0.35)。综合分析, 2 种施氮条件下, ‘KB215’、‘KB417’、‘KA225’、‘KB081’和‘L123098-2’ 5 份玉米自交系具有吐丝期绿叶面积大, 吐丝期茎叶干重、籽粒氮含量高和籽粒产量高, 耐低氮能力强的特点。因此, 强化育种环境的选择压力, 实施低氮选择策略, 可有效提高玉米种质对氮肥的利用效率。
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