Retinotopic order appears before ocular separation in developing visual pathways

In mammals, the major subcortical visual structures receive projections from both eyes, with the uncrossed projection being smaller than the crossed. Each projection is arranged as a separate orderly map of one hemiretina. Although these hemiretinal maps are separate in the nuclei, they are aligned so that the representations of points in the visual field are in register, thus there is a continuity of visual field representation between them. During the early development of the binocular pathways, terminals from the two eyes overlap almost entirely. As development proceeds, terminals arising from each eye segregate to form the adult pattern. In the present study, local retinal lesions were made in ferrets at various stages in development before the separation of the projections from the two eyes. A neuronal tracer was then injected into the damaged eye, defining the pattern of projection from that eye. As reported here, the lesion resulted in a limited interruption in the pattern of terminal label on both sides of the brain, demonstrating that terminals from each eye are arranged in an orderly retinotopic manner at this stage. hence, during later development, as one projection is reduced relative to the other, the two maps must slide in relation to each other.     

Regulation of axon growth in vivo by activity-based competition

The formation of functional neural networks requires precise regulation of the growth and branching of the terminal arbors of axons, processes known to be influenced by early network electrical activity. Here we show that a rule of activity-based competition between neighbouring axons appears to govern the growth and branching of retinal ganglion cell (RGC) axon arbors in the developing optic tectum of zebrafish. Mosaic expression of an exogenous potassium channel or a dominant-negative SNARE protein was used to suppress electrical or neurosecretory activity in subsets of RGC axons. Imaging in vivo showed that these forms of activity suppression strongly inhibit both net growth and the formation of new branches by individually transfected RGC axon arbors. The inhibition is relieved when the activity of nearby 'competing' RGC axons is also suppressed. These results therefore identify a new form of activity-based competition rule that might be a key regulator of axon growth and branch initiation.     

零售商竞争下的合作广告策略与订货策略

针对一个制造商与多个竞争性零售商组成的供应链系统,研究了需求不确定的情况下,处于主方的制造商的最优品牌广告投入水平、地方性广告投入补贴费用,以及作为从方的多个具有关联性(竞争)的零售商的最佳地方性广告投入和订货问题。建立了合作广告的主从对策模型,证明了均衡解的存在,并给出了优化模型的求解算法。最后以一个制造商和两个零售商为例进行了数值实验,分析了参数变化对最优策略的影响。     

一类n阶本原图的广义Competition指数

根据图论、数论的相关知识，对本原图中每一点经过k长途径所到达点的集合进行分析，再结合广义Competition 指数的定义，确定了一类n阶本原图的广义 Competition 指数。当m≤s＋1且s＋m为奇数时，km（D）=1＋〔s＋m-1/2〕s;当m≤s且s＋m为偶数时，km（D）=1＋〔s＋m-2/2〕（s＋1）;当m≥s＋2时，km（D）=1＋s2.     

Computing along the axon

A special form of spiking neural P systems, called axon P systems, corresponding to the activity of Ranvier nodes of neuron axon, is considered and a class of SN-like P systems where the computation is done along the axon is introduced and their language generative power is investigated.     

Computing along the axon

A special form of spiking neural P systems, called axon P systems, corresponding to the activity of Ranvier nodes of neuron axon, is considered and a class of SN-like P systems where the computation is done along the axon is introduced and their language generative power is investigated.     

Separate sodium and calcium spikes in the same axon

Aglantha digitale is a jellyfish (order Hydromedusae) capable of two distinct kinds of locomotion; 'slow' swimming which is generated endogenously and is used in fishing behaviour, and 'fast' swimming which is evoked by predators and serves for escape. Both forms of swimming are produced by contraction of the bell-shaped body wall and expulsion of a jet of water from an opening at the base of the animal. During slow swimming, the contractions are weak and the animal moves about 15 mm, roughly one body length, but during a fast swim there is a more violent contraction which can propel the animal five times as far. Both forms of contraction depend on impulses in the eight giant motor axons that synapse directly with the muscle sheet making up the inner surface of the body wall. We report here that the giant motor axons are able to mediate both kinds of activity because they can conduct two different sorts of impulse. Fast swimming requires a rapidly conducted Na+-dependent action potential whereas slow swimming depends on a low amplitude Ca2+ 'spike'. This is the first report of an axon capable of two kinds of impulse propagation and it provides a physiological function for low potential Ca2+ activation.     

权力场上的人性角逐--论刘震云早期中篇系列小说

刘震云早期的中篇小说《新兵连》、《单位》、《一地鸡毛》、《官人》、《官场》、《头人》等系列作品都渗透出一种有关权力的思考,作品刻画了一个个在权力重压下被扭曲的“官”或“民”的人物形象。这些人物为获取权力或为权力所驱使,在权力的角斗场上疫于奔命,成为主体意识沦丧的灰色人群。通过对灰色人群生存状态的审视,刘的“新写实”叙事文本极大丰富了当代文学对人性内涵的表达,揭示了国人真实的文化心理和当前面临的精神困境。同时,这些作品蕴含的矛盾也表明作家思想的犹疑及其对传统现实主义写作观念的新思考。     

Turnover of fluorescently labelled tubulin and actin in the axon.

The cytoskeleton has an important role in the generation and maintenance of the structure of the axon. Microtubules, neurofilaments and actin, together with various kinds of associated proteins, form highly organized dynamic cytoskeletal structures. Because tubulin and actin molecules are essential cytoskeletal components and are transported down the axon, it is important to understand their dynamic behaviour within the axon. Although previous pulse-labelling studies have indicated that the axonal cytoskeleton is a static complex travelling down the axon, this view has been challenged by the results of several recent experiments. We have now addressed this question by analysing the recovery of fluorescence after photobleaching fluorescent analogues of tubulin and actin in the axons of cultured neurons. We did not observe movement or spreading of bleached zones along the axon, both in neurons injected with fluorescein-labelled tubulin and actin. All bleached zones recovered their fluorescence gradually, however, indicating that microtubules and actin filaments are not static polymers moving forward within the axon, but are dynamic structures that continue to assemble along the length of the axon.     

High-transition-temperature superconductivity in the absence of the magnetic-resonance mode

The fundamental mechanism that gives rise to high-transition-temperature (high-T(c)) superconductivity in the copper oxide materials has been debated since the discovery of the phenomenon. Recent work has focused on a sharp 'kink' in the kinetic energy spectra of the electrons as a possible signature of the force that creates the superconducting state. The kink has been related to a magnetic resonance and also to phonons. Here we report that infrared spectra of Bi2Sr2CaCu2O8+delta (Bi-2212), shows that this sharp feature can be separated from a broad background and, interestingly, weakens with doping before disappearing completely at a critical doping level of 0.23 holes per copper atom. Superconductivity is still strong in terms of the transition temperature at this doping (T(c) approximately 55 K), so our results rule out both the magnetic resonance peak and phonons as the principal cause of high-T(c) superconductivity. The broad background, on the other hand, is a universal property of the copper-oxygen plane and provides a good candidate signature of the 'glue' that binds the electrons.     

Interferon-gamma elicits arteriosclerosis in the absence of leukocytes

Atherosclerosis and post-transplant graft arteriosclerosis are both characterized by expansion of the arterial intima as a result of the infiltration of mononuclear leukocytes, the proliferation of vascular smooth muscle cells (VSMCs) and the accumulation of extracellular matrix. They are also associated with the presence of the immunomodulatory cytokine interferon-gamma (IFN-gamma). Moreover, in mouse models of atheroma formation or allogeneic transplantation, the serological neutralization or genetic absence of IFN-gamma markedly reduces the extent of intimal expansion. However, other studies have found that exogenous IFN-gamma inhibits cultured VSMC proliferation and matrix synthesis, and reduces intimal expansion in response to mechanical injury. This discrepancy is generally explained by the idea that IFN-gamma either directly activates macrophages, or, by increasing antigen presentation, indirectly activates T cells within the lesions of atherosclerosis and graft arteriosclerosis. These activated leukocytes are thought to express the VSMC-activating cytokines and cell-surface molecules that cause the observed arteriosclerotic responses. Here we have inserted pig and human arteries into the aorta of immunodeficient mice, and we show that IFN-gamma can induce arteriosclerotic changes in the absence of detectable immunocytes by acting on VSMCs to potentiate growth-factor-induced mitogenesis.