DMSP夜间灯光数据与Landsat数据结合的建成区提取研究——以江西省为例

建成区面积代表着城镇用地水平和发达程度,其变化反映了城市扩张强度和经济发展水平.该文以江西省为研究区域,提出了一种Landsat TM/ETM＋光学遥感影像与DMSP/OLS(Defense Meteorological Satellites Program/ Operational Linescan System)夜光数据相结合的建成区提取方法,提取精度达到89.7%;利用长时序提取结果分析了江西省1995年～2014年的城市建成区扩张情况,结果表明江西省近20 a间建成区面积增加了1 276.33 km2,扩张率达423.99%.综合分析建成区提取结果与经济统计指标,结果显示江西省的建成区面积扩张与经济发展存在显著正相关关系(R2＝0.62);鄱阳湖生态经济区建立后,区域内城市的建成区建设速度和经济发展速度明显加快.     

Interneuronal barrages and ripple superposed on inhibitory postsynaptic potentials

Résumé L'activité électrique des neurones du noyau thalamique ventro-latéral est étudiée ici chez des chats anesthésiés au nembutal et immobilisés avec du flaxedil au moyen d'un enregistrement intracellulaire. Nous avons observé que l'enregistrement de certains neurones montre que le potentiel nommé inhibiteur postsynaptique (IPSP) est accompagné de la décharge en barrage d'un autre neurone probablement semblable à la cellule deRenshaw.

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We thank Mr.G. Bilanow for invaluable technical help.     

Terahertz semiconductor-heterostructure laser

Semiconductor devices have become indispensable for generating electromagnetic radiation in everyday applications. Visible and infrared diode lasers are at the core of information technology, and at the other end of the spectrum, microwave and radio-frequency emitters enable wireless communications. But the terahertz region (1-10 THz; 1 THz = 10(12) Hz) between these ranges has remained largely underdeveloped, despite the identification of various possible applications--for example, chemical detection, astronomy and medical imaging. Progress in this area has been hampered by the lack of compact, low-consumption, solid-state terahertz sources. Here we report a monolithic terahertz injection laser that is based on interminiband transitions in the conduction band of a semiconductor (GaAs/AlGaAs) heterostructure. The prototype demonstrated emits a single mode at 4.4 THz, and already shows high output powers of more than 2 mW with low threshold current densities of about a few hundred A cm(-2) up to 50 K. These results are very promising for extending the present laser concept to continuous-wave and high-temperature operation, which would lead to implementation in practical photonic systems.     

Selective inhibition of the multiplication of phage T1 inE. coli K12

Riassunto Un nuovo antibiotico, la Distamicina, inibisce selettivamente lo sviluppo del batteriofago T1 inE. coli K12 pur non esercitando alcuna azione sullo sviluppo del microorganismo ospite. L'antibiotico può inibire sia la penetrazione del batteriofago nelle cellule batteriche sia la sua liberazione.     

The formation of the Kuiper belt by the outward transport of bodies during Neptune's migration

The 'dynamically cold Kuiper belt' consists of objects on low-inclination orbits between approximately 40 and approximately 50 au from the Sun. It currently contains material totalling less than a tenth the mass of the Earth, which is surprisingly low because, according to accretion models, the objects would not have grown to their present size unless the cold Kuiper belt originally contained tens of Earth masses of solids. Although several mechanisms have been proposed to produce the observed mass depletion, they all have significant limitations. Here we show that the objects currently observed in the dynamically cold Kuiper belt were most probably formed within approximately 35 au and were subsequently pushed outward by Neptune's 1:2 mean motion resonance during its final phase of migration. Combining our mechanism with previous work, we conclude that the entire Kuiper belt formed closer to the Sun and was transported outward during the final stages of planet formation.     

Positioning of follicular dendritic cells within the spleen controls prion neuroinvasion

Peripheral infection is the natural route of transmission in most prion diseases. Peripheral prion infection is followed by rapid prion replication in lymphoid organs, neuroinvasion and progressive neurological disease. Both immune cells and nerves are involved in pathogenesis, but the mechanisms of prion transfer from the immune to the nervous system are unknown. Here we show that ablation of the chemokine receptor CXCR5 juxtaposes follicular dendritic cells (FDCs) to major splenic nerves, and accelerates the transfer of intraperitoneally administered prions into the spinal cord. Neuroinvasion velocity correlated exclusively with the relative locations of FDCs and nerves: transfer of CXCR5-/- bone marrow to wild-type mice induced perineural FDCs and enhanced neuroinvasion, whereas reciprocal transfer to CXCR5-/- mice abolished them and restored normal efficiency of neuroinvasion. Suppression of lymphotoxin signalling depleted FDCs, abolished splenic infectivity, and suppressed acceleration of pathogenesis in CXCR5-/- mice. This suggests that prion neuroimmune transition occurs between FDCs and sympathetic nerves, and relative positioning of FDCs and nerves controls the efficiency of peripheral prion infection.     

Pregnancy: a cloned horse born to its dam twin

Several animal species, including sheep, mice, cattle, goats, rabbits, cats, pigs and, more recently, mules have been reproduced by somatic cell cloning, with the offspring being a genetic copy of the animal donor of the nuclear material used for transfer into an enucleated oocyte. Here we use this technology to clone an adult horse and show that it is possible to establish a viable, full-term pregnancy in which the surrogate mother is also the nuclear donor. The cloned offspring is therefore genetically identical to the mare who carried it, challenging the idea that maternal immunological recognition of fetal antigens influences the well-being of the fetus and the outcome of the pregnancy.     

意大利歌剧院的体形、体量及材料对声场的影响

针对意大利歌剧院进行研究，着重研究建筑设计对厅堂音质的影响．对两个剧院的常规音质参量进行了测量．这两座剧院是由同一建筑师Antonio Galli Bibiena设计的，分别是波仑亚的市立剧院和曼图亚的科学剧院．二者具有相当近似的形式，但尺寸不同，所用的材料也各畀，前者是用砖石建成，后者是用木料建成，因此在整修前采用了许多预应力钢筋混凝土结构．文中提供了不少数据并给出了对这些数据加以比较和分析的结果，特别是关于某些特征尺寸与扫频信号各可闻频率产生的空间听觉感受之间相关性的分析，以及若干有关材料和体型对IACC和EDT等音质参量的影响的思考．