【摘 要】
：
Nitrogen is a limiting element for all living organisms,including plants grown in the wild and in agriculture.A group of plants,lar-gely legumes,have developed strategies to “grab” free atmospheric nitrogen by symbiotically housing nitrogen-fixing bacteri
【机 构】
：
Department of Biological Sciences,National University of Singapore,Singapore 117543,Singapore;Depart
论文部分内容阅读
Nitrogen is a limiting element for all living organisms,including plants grown in the wild and in agriculture.A group of plants,lar-gely legumes,have developed strategies to “grab” free atmospheric nitrogen by symbiotically housing nitrogen-fixing bacteria,collec-tively referred to as rhizobia,in highly specialized organs called root nodules.These root nodules have fascinated botanists for cen-turies,and how they are formed,or their evolutionary develop-mental (evo-devo) origin,has remained at the center of the mystery.In recent years,various studies suggest that legume nodulation shares genetic hallmarks of lateral root development[1,2],a process found in most if not all seed plants.Histological and lineage-tracing studies also revealed the similarity in the cel-lular origins between root nodules and lateral roots-being that of pericycle,endodermis,and cortex of the primary root [3-5].
其他文献
卡默勒的幻觉主义理论是现象意识分析中一种不同的声音。其幻觉主义理论认为:现象意识是一个幻觉;可基于相似性理论来解释现象意识的机制,指出现象意识就是外部物理性质经模块处理的结果,其处理过程遵循表象原则、接受喜好原则、配置原则和个例化原则;现象意识的幻觉元是解释现象意识为何强烈的问题。幻觉主义理论为现象意识的分析提供了一个新的思路,但也存在着如特殊心理模块等的理论缺陷。
为了研究硅电极在充放电过程中的应力演化,在忽略弹性变形的情况下提出了一个考虑粘塑性的简化力学模型,分别导出了出现相分离和不出现相分离时薄膜电极内应力场的解析解,该模型的计算结果与现有的实验结果相吻合.计算结果表明,当存在相分离时,电极中的应力取决于薄膜电极的厚度和充电速率的乘积;在未出现相分离现象时,应力仅取决于充电速率.这个解析形式的力学模型对于锂离子电池电极材料的设计有着重要的指导意义.
研究静载荷作用下夹层圆板的超谐波共振问题.基于Hoff型夹层板理论,给出了静载荷作用下夹层圆板的非线性动力学方程.应用Galerkin法推导了静载荷作用下夹层圆板的轴对称非线性振动方程.运用多尺度法分别对系统的三次超谐波问题和二次超谐波问题进行了求解,并依据Lyapunov稳定性理论得到了系统稳态运动的稳定性判据.通过算例,得到了周边简支约束下夹层圆板三次超谐波共振和二次超谐波共振的幅频响应曲线图、振幅-静载荷响应曲线图、振幅-激励力幅值响应曲线图;研究了不同参数对系统振幅的影响规律,并对解的稳定性进行了
Following the observation of three narrow N* pentaquark states with hidden charm,Pc(4312),Pc(4440)and Pc(4457)[1,2],very recently,the LHCb Collaboration reported the first evidence for their strange ∧* counterparts,PCS(4459),in the J/ψ∧ invariant mass dis
Seasonal abrupt climatic events severely impact ecosystems and human society.Knowledge of how seasonal abrupt climate events have evolved in the geological past is crucial for under-standing seasonal climate change,because the long duration of geological
Besides the observed quark-antiquark and three-quark states,the quark model predicts other states with integral charges,such as qq(qq)(tetraquarks)and qqqq(q)(pentaquarks).In 2015,the LHCb Collaboration observed J/ψp resonances consistent with pen-taquark
First evidence of a structure in the J/ψ∧ invariant mass distribution is obtained from an amplitude anal-ysis of Ξ-b → J/ψ∧K-decays.The observed structure is consistent with being due to a charmonium pen-taquark with strangeness with a significance of 3.1
Zhang et al.[1] reported the first direct detection of the natural supercritical CO2 (scCO2;critical point:31.1 ℃ and 72.9 atm) in a deep-sea hydrothermal system,In their study,they measured in situ the Raman bands of scCO2 bubbling from an approximately
When elemental iron is cooled from high temperatures,mag-netic moments carried by its d-electrons begin a continuous tran-sition to a state of parallel aligned moments below its Curie temperature Tc of about 1040 K.As established in the mid-1900s,the stat
Sulfur dioxide(SO2)was previously considered only as air pol-lutant.In 2008,our group first detected the endogenous SO2 gener-ating enzymes as well as its generating pathway in cardiovascular system[1].Our recent studies have shown that endogenous SO2 pla