Conodont survival and low iridium abundances across the permian-triassic boundary in South china

The Permian-Triassic sedimentary sequence of China includes one of the most complete and fossiliferous Paleozoic-Mesozoic boundaries known. Closely spaced sampling across the boundary, which is an important extinction event for most organisms, has produced good conodont faunas that show little diversity change. A drop in conodont abundance is the only apparent response to the extinction event. A low concentration of iridium in the boundary clay (0.002 part per billion +/-20 percent), as well as in samples immediately below and above, that range from 0.004 to 0.034 part per billion do not support the proposal of an extraterrestrial impact event at this boundary in China.     

Altered river morphology in south africa related to the permian-triassic extinction

The Permian-Triassic transition in the Karoo Basin of South Africa was characterized by a rapid and apparently basin-wide change from meandering to braided river systems, as evidenced by preserved sedimentary facies. This radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die-off of rooted plant life in the basin. Evidence from correlative nonmarine strata elsewhere in the world containing fluvial Permian-Triassic boundary sections suggests that a catastrophic terrestrial die-off of vegetation was a global event, producing a marked increase in sediment yield as well as contributing to the global delta(13)C excursion across the Permian-Triassic boundary.     

农业“艺机一体化”的实践与思考

农业机械化是农业现代化进程中的关键环节。基于6 a的研究和实践,提出了"艺机一体化"的概念。"艺机一体化"既是山西省情、农情的特殊要求,也是现阶段我国国情、农情的普遍需求,它不仅使先进农艺技术有了载体,而且作为一个关键环节,还进一步有力地促进了农业生产的科学化、机械化以及在此基础上的规模化、商品化乃至产业化;同时也推动了学科的建设和发展,是与时俱进的机械化。其发展进程中所出现的更广范围的障碍因素、发人深思的诸多问题,则需要在新一轮的改革中突破。     

杨树叶试管不定根高频率同步发生体系的研究

[目的]建立高频率和高同步性不定根发生体系。[方法]以长期继代培养的741杨无根苗或有根试管苗[Populus alba×(P.davidiana+P.simonni)P.tomentosa]的叶、嫩茎、叶盘和叶柄等外植体为试材,在试管内分别诱导不定根发生。[结果]从不定根发根时间、生根率和生根同步性等方面看,所有生根试管苗上的叶明显优于嫩茎、继代苗上的叶、叶盘和叶柄,而试管生根初期苗上的叶又好于生根后期苗上的叶。进一步优化试管生根初期苗上的叶的不定根诱导条件,在1/2 MS+0.5 mg/LIBA生根培养基上,培养6 d可见根原基突起,6～8 d为不定根高发期,8 d后生根率可达100%,单叶平均生根数为3.7条。不定根发生进程的形态学观察发现,不定根发生部位为叶柄基部及向上至3 mm处,不定根起始分化时间集中为诱导后2 d,不定根发生起源于维管形成层,特别是维管射线正对的形成层。[结论]杨树是木本植物的模式植物,建立高频率和高同步性不定根发生体系,可为深入研究木本植物不定根发生调控机制提供良好的试验体系和技术平台。     

市场边界的策略分析

把市场机制与灵活性行为和混合策略联系起来,可以得到市场存在于极确定与极不确定之间的环境中。市场的边界还随着行为主体对环境信息的识别能力而变化,完全的信息意味着市场边界的扩大。另外,在极不确定的情况下,习惯和传统机制将起主导作用,而在极确定的条件下,理性的计划体制将发挥作用。     

一种保证步进电机在变速运行中不失步的控制方法

在单片机控制系统中，提出了通过硬件及软件的失步解决方案，并给出实例。     

Quantum state engineering and precision metrology using state-insensitive light traps

Precision metrology and quantum measurement often demand that matter be prepared in well-defined quantum states for both internal and external degrees of freedom. Laser-cooled neutral atoms localized in a deeply confining optical potential satisfy this requirement. With an appropriate choice of wavelength and polarization for the optical trap, two electronic states of an atom can experience the same trapping potential, permitting coherent control of electronic transitions independent of the atomic center-of-mass motion. Here, we review a number of recent experiments that use this approach to investigate precision quantum metrology for optical atomic clocks and coherent control of optical interactions of single atoms and photons within the context of cavity quantum electrodynamics. We also provide a brief survey of promising prospects for future work.     

不同诱捕器与诱芯对柑橘小实蝇的诱捕效果

对不同诱捕器及诱芯诱捕柑橘小实蝇进行试验。结果表明,广西柳州双虹塑料工业有限公司生产的诱捕器诱捕柑橘小实蝇效果最好,其次为自制和浙江慈溪和城信息科技有限公司生产的诱捕器,宁波纽康生物技术有限公司生产的诱捕器的效果最不理想。用纤维板诱芯诱捕柑橘小实蝇效果比用棉花和诱蝇醚包装瓶直接当成诱芯使用效果好。     

不同诱捕器和引诱剂组合对松墨天牛诱捕效果的影响

为探讨生产上松墨天牛诱捕优化技术,于2013年和2014年在福建省安溪县开展了不同诱捕器和引诱剂组合(农林大APF-Ⅰ型引诱剂及其诱捕器、福建省L型引诱剂及其L型诱捕器)诱捕松墨天牛成虫试验,比较诱获的松墨天牛数量,并抽取部分虫体进行解剖,分析其携带的寄生性线虫及雌成虫的怀卵情况。结果表明,不同诱捕器引诱剂4种组合2 a间诱捕的松墨天牛总数量有极显著差异。农林大APF-Ⅰ型引诱剂及其诱捕器诱获的天牛数量最多,雌雄比最大;福建省L型引诱剂及其L型诱捕器组合诱获的天牛数量最少,雌雄比最低。在诱捕器相同的情况下,APF-Ⅰ型引诱剂的诱捕效果极显著优于L型引诱剂,且前者诱捕天牛的雌雄比高于后者。在引诱剂相同的情况下,农林大诱捕器与福建省L型诱捕器的诱捕效果差异不显著,且两者诱捕的天牛雌雄比差别不大。APF-Ⅰ型引诱剂引诱的天牛成虫寄生性线虫携带率高于L型引诱剂,但2种引诱剂引诱的松墨天牛雌成虫平均怀卵量差异不大,因此生产上应优先推广APF-Ⅰ型引诱剂。     

Diviner Lunar Radiometer observations of cold traps in the Moon's south polar region

Diviner Lunar Radiometer Experiment surface-temperature maps reveal the existence of widespread surface and near-surface cryogenic regions that extend beyond the boundaries of persistent shadow. The Lunar Crater Observation and Sensing Satellite (LCROSS) struck one of the coldest of these regions, where subsurface temperatures are estimated to be 38 kelvin. Large areas of the lunar polar regions are currently cold enough to cold-trap water ice as well as a range of both more volatile and less volatile species. The diverse mixture of water and high-volatility compounds detected in the LCROSS ejecta plume is strong evidence for the impact delivery and cold-trapping of volatiles derived from primitive outer solar system bodies.     

桔小实蝇诱捕器悬挂高度对诱捕效果的影响

观察研究了柿子园内性诱剂诱捕器悬挂高度对桔小实蝇雄性成虫诱集效果的影响。结果表明,在一定高度范围内随着诱捕器悬挂高度的增高,诱集到的虫量呈上升趋势,1.5 m、2.5 m、3.5 m、4.5 m和5.5 m等不同处理诱集虫量分别占总虫数的8.1%、14.0%、18.6%、20.2%,39.1%。悬挂高度以树冠中层效果最好,树冠下层其次,树冠以下最差。     

Grain boundary scars and spherical crystallography

We describe experimental investigations of the structure of two-dimensional spherical crystals. The crystals, formed by beads self-assembled on water droplets in oil, serve as model systems for exploring very general theories about the minimum-energy configurations of particles with arbitrary repulsive interactions on curved surfaces. Above a critical system size we find that crystals develop distinctive high-angle grain boundaries, or scars, not found in planar crystals. The number of excess defects in a scar is shown to grow linearly with the dimensionless system size. The observed slope is expected to be universal, independent of the microscopic potential.     

农田-草地景观镶嵌体土壤水分界面瞬时判定初探

采用地统计学方法和Lattice Wombling界面判定方法对典型农牧交错带(河北沽源地区)农田-草地景观镶嵌体土壤水分界面的瞬时界面因子空间特征进行初探.结果表明:利用地统计学对不同粒度的土壤水分空间特征研究验证土壤水分界面存在,且存在不同生态梯度效应.应用Lattice Wombling界面判定方法对农田-草地界面土壤水分进行界面的瞬时判定表明,农田-草地界面土壤水分界面的判定呈不规则曲线的界面变化;农田-草地界面土壤水分界面的界面因子(BE)在农田内部较为明显,在距农田草地边界农田一侧的3~7 m处和草地内部3 m处左右.     

粘虫黄板不同放置高度对黄曲条跳甲诱杀效果试验

利用黄曲条跳甲对黄色具有正趋性的特点,进行了粘虫黄板不同放置高度对黄曲条跳甲成虫的诱杀效果试验,结果表明,诱杀黄曲条跳甲的粘虫黄板的最佳放置高度为8~24cm,这个高度恰好是试验时迟熟菜心分布有绿叶和嫩芽的区域。