Absolute plate motions and true polar wander in the absence of hotspot tracks

The motion of continents relative to the Earth's spin axis may be due either to rotation of the entire Earth relative to its spin axis--true polar wander--or to the motion of individual plates. In order to distinguish between these over the past 320 Myr (since the formation of the Pangaea supercontinent), we present here computations of the global average of continental motion and rotation through time in a palaeomagnetic reference frame. Two components are identified: a steady northward motion and, during certain time intervals, clockwise and anticlockwise rotations, interpreted as evidence for true polar wander. We find approximately 18 degrees anticlockwise rotation about 250-220 Myr ago and the same amount of clockwise rotation about 195-145 Myr ago. In both cases the rotation axis is located at about 10-20 degrees W, 0 degrees N, near the site that became the North American-South American-African triple junction at the break-up of Pangaea. This was followed by approximately 10 degrees clockwise rotation about 145-135 Myr ago, followed again by the same amount of anticlockwise rotation about 110-100 Myr ago, with a rotation axis in both cases approximately 25-50 degrees E in the reconstructed area of North Africa and Arabia. These rotation axes mark the maxima of the degree-two non-hydrostatic geoid during those time intervals, and the fact that the overall net rotation since 320 Myr ago is nearly zero is an indication of long-term stability of the degree-two geoid and related mantle structure. We propose a new reference frame, based on palaeomagnetism, but corrected for the true polar wander identified in this study, appropriate for relating surface to deep mantle processes from 320 Myr ago until hotspot tracks can be used (about 130 Myr ago).     

Ice-volcanism due to tidal stress on Europa

Tectonism would be driven by tidal beat on Europa, and there may be ice-volcano on the surface of active Europa. We assume that ice-volcano would spurt out due to tidal stress, and calculate the velocity and height of the spurt in scale. We also find out the approximate distribution of the active volcanoes on Europa.     

Ultraviolet emissions from the magnetic footprints of Io, Ganymede and Europa on Jupiter

Io leaves a magnetic footprint on Jupiter's upper atmosphere that appears as a spot of ultraviolet emission that remains fixed underneath Io as Jupiter rotates. The specific physical mechanisms responsible for generating those emissions are not well understood, but in general the spot seems to arise because of an electromagnetic interaction between Jupiter's magnetic field and the plasma surrounding Io, driving currents of around 1 million amperes down through Jupiter's ionosphere. The other galilean satellites may also leave footprints, and the presence or absence of such footprints should illuminate the underlying physical mechanism by revealing the strengths of the currents linking the satellites to Jupiter. Here we report persistent, faint, far-ultraviolet emission from the jovian footprints of Ganymede and Europa. We also show that Io's magnetic footprint extends well beyond the immediate vicinity of Io's flux-tube interaction with Jupiter, and much farther than predicted theoretically; the emission persists for several hours downstream. We infer from these data that Ganymede and Europa have persistent interactions with Jupiter's magnetic field despite their thin atmospheres.     

矿井提升机驱动系统合理加速度曲线的确定

矿井提升机提升容器加速度取决于提升机驱动系统加速度和提升绳系特性.基于钢绳为连续弹性杆的条件下,通过提升容器满足乘坐舒适性和提升钢丝绳系产生较小震动为目标的综合分析,提出了矿井提升机械驱动系统的合理加速度曲线,即提升机常用激励加速度函数的首选形式,为矿井提升机的进一步研究和设计提供参考依据.图7,参14.     

Secondary craters on Europa and implications for cratered surfaces

For several decades, most planetary researchers have regarded the impact crater populations on solid-surfaced planets and smaller bodies as predominantly reflecting the direct ('primary') impacts of asteroids and comets. Estimates of the relative and absolute ages of geological units on these objects have been based on this assumption. Here we present an analysis of the comparatively sparse crater population on Jupiter's icy moon Europa and suggest that this assumption is incorrect for small craters. We find that 'secondaries' (craters formed by material ejected from large primary impact craters) comprise about 95 per cent of the small craters (diameters less than 1 km) on Europa. We therefore conclude that large primary impacts into a solid surface (for example, ice or rock) produce far more secondaries than previously believed, implying that the small crater populations on the Moon, Mars and other large bodies must be dominated by secondaries. Moreover, our results indicate that there have been few small comets (less than 100 m diameter) passing through the jovian system in recent times, consistent with dynamical simulations.     

A novel Chinese polar knowledge repository based on polar data-sharing ontology

In order to archive and utilize the information from Chinese polar expeditions to the greatest extent, we design a novel knowledge repository, in which an automatic query model based on neural networks is proposed and a data call trigger is established to keep data consistent between polar data-sharing platforms. And in this repository, anybody can make contributions to the repository by creating or updating entries with version control and an authority control mechanism. In this paper, the data sources, data processes and network structure of this repository are described, and the keywords extraction and decision support operation are detailed. The analysis of this design’s feasibility and applicability indicates that this knowledge repository is open, sole and authoritative for Chinese polar expeditions.     

新型苊并吡嗪类高灵敏度极性探针

以苊醌为原料,经溴化、环构化和芳香亲核取代反应合成了一种新型的以苊并吡嗪为母体的极性荧光探针3-正丁胺基-苊并吡嗪-8,9二腈(A)。探针A的荧光强度随着溶剂极性的增加显著降低,从四氯化碳(Φf=0.364 2)到乙腈(Φf=0.000 6)荧光量子产率减弱超过600倍,从四氯化碳(533nm)到N,N-二甲基甲酰胺(651nm)最大发射波长红移了118nm。利用探针A对极性敏感来检测有机溶剂中的水含量,建立了一种新的四氢呋喃和1,4-二氧六环中水含量荧光分析方法,最低检测限分别为0.019%和0.0076%。     

Active formation of 'chaos terrain' over shallow subsurface water on Europa

Europa, the innermost icy satellite of Jupiter, has a tortured young surface and sustains a liquid water ocean below an ice shell of highly debated thickness. Quasi-circular areas of ice disruption called chaos terrains are unique to Europa, and both their formation and the ice-shell thickness depend on Europa's thermal state. No model so far has been able to explain why features such as Conamara Chaos stand above surrounding terrain and contain matrix domes. Melt-through of a thin (few-kilometre) shell is thermodynamically improbable and cannot raise the ice. The buoyancy of material rising as either plumes of warm, pure ice called diapirs or convective cells in a thick (>10 kilometres) shell is insufficient to produce the observed chaos heights, and no single plume can create matrix domes. Here we report an analysis of archival data from Europa, guided by processes observed within Earth's subglacial volcanoes and ice shelves. The data suggest that chaos terrains form above liquid water lenses perched within the ice shell as shallow as 3?kilometres. Our results suggest that ice-water interactions and freeze-out give rise to the diverse morphologies and topography of chaos terrains. The sunken topography of Thera Macula indicates that Europa is actively resurfacing over a lens comparable in volume to the Great Lakes in North America.     

从汉匈战争中认识真实的李广

在汉匈战争中，与同期的卫青、霍去病相比较，李广有勇无谋，屡为败军之将，与军功无缘，这是导致“李广难封”的根本原因。司马迁在李广传记的写作上对李广颇为衰扬，实为文笔多于史笔，这是缘于他对李广祖孙三代不幸遭遇的深切同情以及他自身挥之不去的悲悯情结。     

真彩色IFS吸引子的计算机构造

阐述了迭代函数系(iteratedfunctionsystem,IFS)理论,给出了构造IFS吸引子的随机迭代算法.将彩色空间与IFS理论相结合,提出了ΦΩΨ-IFS(ΦΩΨ表示RGB、CMY、YIQ、HSV或HLS)模型,并利用计算机构造了一系列二维、三维ΦΩΨ-IFS吸引子(即真彩色IFS吸引子),讨论了ΦΩΨ-IFS吸引子的几何变换和色彩修正.研究表明:调整ΦΩΨ-IFS的参数,既可改变吸引子的结构,也可改变吸引子的色彩,因此ΦΩΨ-IFS吸引子可更有效地模拟自然景观.     

不同纯度和极性的香蕉果皮黄酮抑菌活性的研究

采用滤纸片法,以大肠杆菌和金黄色葡萄球菌为供试菌,对香蕉果皮黄酮粗提物、纯化物、不同极性的黄酮以及香蕉果皮黄酮-丙酸复配剂的抑菌活性进行了研究.结果表明,香蕉果皮黄酮纯度越高,极性越大,抑菌活性越强,对革兰氏阳性菌金黄色葡萄球菌的抑菌活性明显大于对革兰氏阴性菌大肠杆菌的抑菌活性.香蕉果皮黄酮纯化后对大肠杆菌和金黄色葡萄球菌的最小抑菌浓度(MIC)分别为13.00 mg·m L-1和3.25 mg·m L-1,其与丙酸复配能显著增加对大肠杆菌的抑菌活性,2者具有协同增效作用.     

基于极坐标的摄像机标定

为了改进多摄像机标定实现的方便性和参考标定板的多样性,用极坐标设计标定板并以此来进行摄像机参数的标定.根据设计好的标定板确定世界坐标下的特征点,识别相应的特征点在图像坐标的位置,匹配特征点在图像坐标和世界坐标的位置关系后完成摄像机的标定.该标定方法只需大约20点对左右数据,同时保证标定的结果和鲁棒性;较少的点对和图像的多样性避免了遮挡和公共部分不足的问题,有利于完成多摄像机标定,较传统多摄像机标定方法在分配摄像机和标定板之间的位置关系上更加灵活.与传统的精确标定板的结果比较,在保证精度情况下,标定板设计和整个标定系统的实现则更加简单易行.     

仿真物理实验室

仿真实验是一种新型的实验模式,仿真物理实验室是实现这种模式的一个平台,通过这个平台,可以对各种实验进行模拟、演示和动画展示,可以更直观地看到实验过程,也方便对实验数据进行分析.     

刘知张幾与柳宗元辨伪方法论略

刘知几与柳宗元在辨伪学史上皆做出了重要贡献。辨伪方法上,柳宗元继承了刘知几于史实和文义等层面来考辨古籍真伪之路径,并在从源流、语言文字、古籍之著者考辨及伪书并非毫无价值亦有可取之处等诸多方面对古籍辨伪方法作了新的拓展。     

基于四元数极表示的四元数扩散方程

目的去除彩色图像噪声。方法采用RGB灰度中心的彩色空间,使用四元数极表示的各向异性扩散方程给出彩色图像去噪的应用实例。结果使用非线性四元数扩散方程,可以有效地递减阶梯效应。结论基于四元数极表示,提出一个线性扩散方程和3个非线性扩散方程及它们的离散算法,其理论分析结果紧凑,容易应用。     

Phylogenetic relationship and phenotypic comparison of Psychrobacter species isolated from polar oceans

To investigate the phylogenetic relationship and biogeography of bacterioplankton in polar oceans, four Psychrobacter strains, BSw10170, BSw20352, BSw20370, and BSw20461, isolated from seawater of the Bering Sea, the Chukchi Sea, and the Prydz Bay, were characterized by 16S rDNA sequencing and physiological and biochemical testing. Results demonstrated that close relationships existed between the Arctic and Antarctic strains with sequence similarities higher than 97%. These four Psychrobacter strains not only showed almost identical phenotypic characteristics among them, but also shared a lot of similarities with those related Psychrobacter species, indicating that psychrotolerance and halotolerance of Psychrobacter strains may be among the reasons for their bipolar, even global distribution in marine environments at the genus level.