Botany: a new self-pollination mechanism

Pollen grains from most flowering plants are transported by wind or animals and deposited on the receptive surface of the stigma of a different individual, but self-pollination is also common. We have discovered a new process for self-pollination in the laterally orientated flowers of a Chinese herb, in which a film of pollen is transported from the anther (pollen sacs) by an oily emulsion that slides sideways along the flower's style and into the individual's own stigma. This mode of self-pollination is a new addition to the broad range of genetic and morphological mechanisms that have evolved in flowering plants (angiosperms), and may be common in species growing in shady, windless and insect-poor habitats.     

A new cellular mechanism for coupling inputs arriving at different cortical layers

Pyramidal neurons in layer 5 of the neocortex of the brain extend their axons and dendrites into all layers. They are also unusual in having both an axonal and a dendritic zone for the initiation of action potentials. Distal dendritic inputs, which normally appear greatly attenuated at the axon, must cross a high threshold at the dendritic initiation zone to evoke calcium action potentials but can then generate bursts of axonal action potentials. Here we show that a single back-propagating sodium action potential generated in the axon facilitates the initiation of these calcium action potentials when it coincides with distal dendritic input within a time window of several milliseconds. Inhibitory dendritic input can selectively block the initiation of dendritic calcium action potentials, preventing bursts of axonal action potentials. Thus, excitatory and inhibitory postsynaptic potentials arising in the distal dendrites can exert significantly greater control over action potential initiation in the axon than would be expected from their electrotonically isolated locations. The coincidence of a single back-propagating action potential with a subthreshold distal excitatory postsynaptic potential to evoke a burst of axonal action potentials represents a new mechanism by which the main cortical output neurons can associate inputs arriving at different cortical layers.     

A cellular mechanism of reward-related learning.

Positive reinforcement helps to control the acquisition of learned behaviours. Here we report a cellular mechanism in the brain that may underlie the behavioural effects of positive reinforcement. We used intracranial self-stimulation (ICSS) as a model of reinforcement learning, in which each rat learns to press a lever that applies reinforcing electrical stimulation to its own substantia nigra. The outputs from neurons of the substantia nigra terminate on neurons in the striatum in close proximity to inputs from the cerebral cortex on the same striatal neurons. We measured the effect of substantia nigra stimulation on these inputs from the cortex to striatal neurons and also on how quickly the rats learned to press the lever. We found that stimulation of the substantia nigra (with the optimal parameters for lever-pressing behaviour) induced potentiation of synapses between the cortex and the striatum, which required activation of dopamine receptors. The degree of potentiation within ten minutes of the ICSS trains was correlated with the time taken by the rats to learn ICSS behaviour. We propose that stimulation of the substantia nigra when the lever is pressed induces a similar potentiation of cortical inputs to the striatum, positively reinforcing the learning of the behaviour by the rats.     

生态系统关键种理论:新思想、新机制、新途径

关键种概念的提出,推动了生态学的深入发展,并渐已成为保护生物学基本原理的组成部分,但同明它也受到一些质疑介绍了关键种概念的内涵、外延及国内外研究现状,评价了其重要价值,阐述了亟待研究的几个问题。     

Interferon modulation of cellular microRNAs as an antiviral mechanism

RNA interference through non-coding microRNAs (miRNAs) represents a vital component of the innate antiviral immune response in plants and invertebrate animals; however, a role for cellular miRNAs in the defence against viral infection in mammalian organisms has thus far remained elusive. Here we show that interferon beta (IFNbeta) rapidly modulates the expression of numerous cellular miRNAs, and that eight of these IFNbeta-induced miRNAs have sequence-predicted targets within the hepatitis C virus (HCV) genomic RNA. The introduction of synthetic miRNA-mimics corresponding to these IFNbeta-induced miRNAs reproduces the antiviral effects of IFNbeta on HCV replication and infection, whereas neutralization of these antiviral miRNAs with anti-miRNAs reduces the antiviral effects of IFNbeta against HCV. In addition, we demonstrate that IFNbeta treatment leads to a significant reduction in the expression of the liver-specific miR-122, an miRNA that has been previously shown to be essential for HCV replication. Therefore, our findings strongly support the notion that mammalian organisms too, through the interferon system, use cellular miRNAs to combat viral infections.     

探索党建工作新途径 开拓思政教育新思路

当前高等教育全面发展、高校不断扩招、学生素质整体下降，高校系部党建和思想政治工作出现很多以前没有遇到的问题和困难，要搞好系部的党建和思想政治工作，必须充分研究新形势、探索新途径、形成新机制、开拓新思路。     

一种新型红色夹泥成因机制的工程地质分析

以湖北某水电站坝肩岩体内发现的大量红色夹泥为例,以红色夹泥的矿物成分和化学成分分析结果以及物理性质测试结果为基础,结合现场调查资料,从构造、正常风化卸荷、斜坡变形、喀斯特垮塌等方面入手,综合分析得出了红色夹泥的成因是:红色夹泥是由于层状岩体中小型层状溶洞顶板岩体坍塌,造成围岩变形、拉裂,后期地下水携带泥质物充填形成.     

一种新型微位移放大机构设计与特性分析

基于柔性铰链的传导性,运用杠杆原理设计了一种全对称结构的二级微位移放大机构,该机构具有无附加方向上位移及运动精确等优点.建立了微位移放大机构的仿真模型和运动学模型,给出了工作原理;根据机构学原理推导出了机构位移放大比,运用ANSYS13.0对该机构进行有限元仿真,得出了实际输出位移、放大比及该机构的固有频率.放大比误差为7.46%;误差分析主要原因为在理论模型中采取简化分析,忽略了柔性铰链伸长变形导致的中心偏移,并且假设了除去柔性铰链外,其他的部分全为刚性.本文研究为微位移放大机构的实际生产提供了理论依据.     

一种新型齿轮齿条发动机的结构及其机理分析

提出一种能源利用率高的新型齿轮齿条发动机,介绍该发动机的结构和特点,分析发动机的工作过程及其驱动特性.理论分析和仿真实验结果表明,新型发动机解决了传统发动机存在对曲轴主轴颈的"死点"压力和对汽缸壁的侧向压力等不平衡问题.     

Autophagy as new emerging cellular effect of nanomaterials

The biosafety issue of nanoscale materials is getting more and more attention with their increasing manufacture and application.In the research of cellular effects and underlying mechanisms related to toxicity of nanomaterials,most emphasis were placed on processes such as apoptosis,metabolic inhibition and oxidative stress.Recent evidence suggests that autophagy is part of the biological effects by nanomaterials and various kinds of nanomaterials are capable of disturbing the autophagic process.This review will highlight the importance of autophagy as an emerging mechanism of nanomaterial toxicity and the implication in the therapy of autophagy-related diseases.We summarize current research status of interaction between nanomaterials and autophagic pathways.It is of note that nanomaterials can either induce or block autophagy,which result in similar phenotype but completely different biological consequence.It is therefore important to perform comprehensive analysis of the whole autophagic flux in the future research.     

Opsin expression: new mechanism for modulating colour vision

Each cone photoreceptor in the retina responds to light in a limited range of wavelengths, giving it a spectral phenotype. This phenotype is determined by the most prevalent of the photoreceptor's visual-pigment proteins (opsins) and is assumed to remain unchanged during an animal's lifetime. Here we show that in the Pacific pink salmon, Oncorhynchus gorbuscha, single cones can switch their spectral phenotype from ultraviolet to blue by regulating the production of the appropriate opsins as the fish grow older. This photoreceptor plasticity may operate to modulate colour vision as the salmon's lifestyle changes.     

基于业务量感知的蜂窝网络中继站协作控制机制

针对目前多用户、多业务的蜂窝网络现状,采用三次指数平滑预测对小区内用户业务量进行统计预测,由预测值产生阈值K来控制中继站(relay station,RS)的工作模式使中继站与基站协作为用户提供服务.仿真结果表明,中继站与基站相互协作可以显著降低网络的掉话率和呼叫阻塞率;改变阈值调整系数α和RS数目会使网络呼叫阻塞率产生明显的变化.     

Structures of human insulin-degrading enzyme reveal a new substrate recognition mechanism

Insulin-degrading enzyme (IDE), a Zn2+-metalloprotease, is involved in the clearance of insulin and amyloid-beta (refs 1-3). Loss-of-function mutations of IDE in rodents cause glucose intolerance and cerebral accumulation of amyloid-beta, whereas enhanced IDE activity effectively reduces brain amyloid-beta (refs 4-7). Here we report structures of human IDE in complex with four substrates (insulin B chain, amyloid-beta peptide (1-40), amylin and glucagon). The amino- and carboxy-terminal domains of IDE (IDE-N and IDE-C, respectively) form an enclosed cage just large enough to encapsulate insulin. Extensive contacts between IDE-N and IDE-C keep the degradation chamber of IDE inaccessible to substrates. Repositioning of the IDE domains enables substrate access to the catalytic cavity. IDE uses size and charge distribution of the substrate-binding cavity selectively to entrap structurally diverse polypeptides. The enclosed substrate undergoes conformational changes to form beta-sheets with two discrete regions of IDE for its degradation. Consistent with this model, mutations disrupting the contacts between IDE-N and IDE-C increase IDE catalytic activity 40-fold. The molecular basis for substrate recognition and allosteric regulation of IDE could aid in designing IDE-based therapies to control cerebral amyloid-beta and blood sugar concentrations.     

'Lophenteropneust' hypothesis refuted by collection and photos of new deep-sea hemichordates

The deep ocean is home to a group of broad-collared hemichordates--the so-called 'lophenteropneusts'--that have been photographed gliding on the sea floor but have not previously been collected. It has been claimed that these worms have collar tentacles and blend morphological features of the two main hemichordate body plans, namely the tentacle-less enteropneusts and the tentacle-bearing pterobranchs. Consequently, lophenteropneusts have been invoked as missing links to suggest that the former evolved into the latter. The most significant aspect of the lophenteropneust hypothesis is its prediction that the fundamental body plan within a basal phylum of deuterostomes was enteropneust-like. The assumption of such an ancestral state influences ideas about the evolution of the vertebrates from the invertebrates. Here we report on the first collected specimen of a broad-collared, deep-sea enteropneust and describe it as a new family, genus and species. The collar, although disproportionately broad, lacks tentacles. In addition, we find no evidence of tentacles in the available deep-sea photographs (published and unpublished) of broad-collared enteropneusts, including those formerly designated as lophenteropneusts. Thus, the lophenteropneust hypothesis was based on misinterpretation of deep-sea photographs of low quality and should no longer be used to support the idea that the enteropneust body plan is basal within the phylum Hemichordata.     

汽车新型储能动力传动系统节能机理

储能传动是一有效的节能传动技术。研究了一种新型储能动力传动系统。与传统的储能动力传动系统相比，新型储能动力传动系统的结构更简单，重量更轻，并且性能更加优越。在探讨新型储能动力传动系统的原理之后，对该系统进行了性能分析，给出了一个新型储能动力传动系统的仿真实例。