The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field

The penetration depth of Saturn’s cloud-level winds into its interior is unknown.A possible way of estimating the depth is through measurement of the effect of the winds on the planet’s gravitational field.We use a self-consistent perturbation approach to study how the equatorially symmetric zonal winds of Saturn contribute to its gravitational field.An important advantage of this approach is that the variation of its gravitational field solely caused by the winds can be isolated and identified because the leading-order problem accounts exactly for rotational distortion,thereby determining the irregular shape and internal structure of the hydrostatic Saturn.We assume that(i)the zonal winds are maintained by thermal convection in the form of non-axisymmetric columnar rolls and(ii)the internal structure of the winds,because of the Taylor-Proundman theorem,can be uniquely determined by the observed cloud-level winds.We calculate both the variation △J_n,n=2,4,6...of the axisymmetric gravitational coefficients J_n caused by the zonal winds and the non-axisymmetric gravitational coefficients △J_(nm) produced by the columnar rolls,where m is the azimuthal wavenumber of the rolls.We consider three different cases characterized by the penetration depth 0.36 R_S,0.2 R_S and 0.1 R_S,where R_S is the equatorial radius of Saturn at the 1-bar pressure level.We find that the high-degree gravitational coefficient ( J_(12)+△J_(12)) is dominated,in all the three cases,by the effect of the zonal flow with |△J_(12)/J_(12)|100%and that the size of the non-axisymmetric coefficientsdirectly reflects the depth and scale of the flow taking place in the Saturnian interior.     

Morphology and Structure of High-redshift Massive Galaxies in the CANDELS Fields

Using the multi-band photometric data of all five CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) fields and the near-infrared (F125W and F160W) high-resolution images of HST WFC3 (Hubble Space Telescope Wide Field Camera 3), a quantitative study of morphology and structure of mass-selected galaxies is presented. The sample includes 8002 galaxies with a redshift 1 < z < 3 and stellar mass M_*> 10¹⁰M_⊙. Based on the Convolutional Neural Network (ConvNet) criteria, we classify the sample galaxies into SPHeroids (SPH), Early-Type Disks (ETD), Late-Type Disks (LTD), and IRRegulars (IRR) in different redshift bins. The findings indicate that the galaxy morphology and structure evolve with redshift up to z ～ 3, from irregular galaxies in the high-redshift universe to the formation of the Hubble sequence dominated by disks and spheroids. For the same redshift interval, the median values of effective radii (r_e) of different morphological types are in a descending order: IRR, LTD, ETD, and SPH. But for the Sérsic index (n), the order is reversed (SPH, ETD, LTD, and IRR). In the meantime, the evolution of galaxy size (r_e) with the redshift is explored for the galaxies of different morphological types, and it is confirmed that their size will enlarge with time. However, such a phenomenon is not found in the relations between the redshift (1 < z < 3) and the mean axis ratio (b/a), as well as the Sérsic index (n).     

乡镇尺度上的山东省人口老龄化空间格局演变与影响因素研究

基于第五次和第六次人口普查数据,研究了乡镇尺度上山东省人口老龄化的空间格局及其演变特征,并采用空间计量方法定量探讨了其影响因素。研究发现：① 山东省人口老龄化发展迅猛,但乡镇街道之间在老龄化水平、老年人口密度和增长速度等方面均存在非常显著的地域差异。② 按照不同的分析维度,山东省乡镇街道涵盖了丰富的人口老龄化地域类型,其中的2个类型形成了典型的空间分异格局。一类主要聚集在县级以上城市及其周边地域,总体上具有老年人口低占比、高密度、高绝对增长、低相对增长的特点;另一类是主要分布在胶东地区、黄河三角洲地区、沂蒙地区和鲁西地区等4个区域的一般乡镇,大体表现为高占比、低密度、低绝对增长、高相对增长特征。③ 空间滞后模型回归结果显示,老龄化动态演变过程的不确定性更强、影响因素更为复杂,基期老龄化基础对其影响效应不显著,经济增长速度有显著负向影响,但经济发展水平对老龄化静态格局的影响却不显著,使得乡镇尺度上老龄化空间格局的演变机制呈现出特殊性。     

Disorder-induced enhancement of conductance in doped nanowires

A new mechanism is proposed to explain the enhancement of conductance in doped nanowires. It is shown that the anomalous enhancement of conductance is due to surface doping. The conductance in doped nanowires increases with dopant concentration, which is qualitatively consistent with the existing experimental results. In addition, the I-V curves are linear and thus suggest that the metal electrodes make ohmic contacts to the shell-doped nanowires. The electric current increases with wire diameter (D) and decreases exponentially with wire length (L). Therefore, the doped nanowires have potential application in nanoscale electronic and optoelectronic devices.     

青海湖盆地35万年来的植被演化及环境变迁

本文依据青海湖南岸二郎剑阶地QH-86孔(深155m)中200余个孢粉样品的分析资料,将该孔深78m以上的孢粉图式,从下至上划分出七个区域性孢粉带,并结合铀系法测年数据,论述了350ka B.P.来的湖区植被和环境演变。其气候曲线与毗邻的柴达木盆地,甚至与深海钻孔及洛川黄土,具有可对比性。     

Silurian integrative stratigraphy and timescale of China

Silurian is a period with the shortest duration in Phanerozoic except for the Neogene and Quaternary. It represents an important and unique interval when the biotic diversity recovered quickly after the end-Ordovician mass extinction, different paleoplates or terranes conjoined, big oceans disappeared or narrowed, climate and sea level changed frequently, global biotic provincialism became weaker, some primitive plants started to occupy the land. Silurian is also the first system of which all the chronostratigraphic stratotypes(i.e. the GSSPs) including four series and seven stages were established by the International Subcommission on Silurian Stratigraphy(ISSS). Nonetheless, during the post-GSSP studies conducted by ISSS in the middle1980 s, some Silurian GSSPs were found to have some congenital defects such as no index fossils available that hinder the high resolution subdivision and correlation on a regional or global scale. In this paper, based on the latest development of Silurian study in China, the progress in biostratigraphy, chronostratigraphy, event stratigraphy(such as facies differentiation, heterochrony of black shales, marine red beds, carbonate rocks and reefs), chemostratigraphy, and tectonic stratigraphy(e.g., widespread of the late Silurian rocks in South China and its tectonic implication) are systematically summarized. Some existing problems and the areas to be focused in future work are also discussed. It is suitable for chronostratigraphic study to concentrate not only on the boundary but also doing multidisciplinary analysis on the biotic, chemical, magnetic, environmental, and chronologic aspects, in order to enhance the reliability and the potential for regional and global correlation of a certain GSSP.Some important achievements are expected in these areas in the Silurian study in China:(1) ecostratigraphy and basin analysis of the Llandovery, and the correlation of integrative stratigraphy with a high resolution;(2) establishment of the Wenlock to Pridoli chronostratigraphic framework;(3) the chemo-and magnetic stratigraphy and the age of some key intervals and horizons;(4)further investigation on paleogeography and plate tectonics; and(5) origin and early evolution of the terrestrial ecosystem. Some new breakthroughs might occur in the restudy on some of those problematic GSSPs of some particular series and stages.     

新型紫外光致发光图像高速采集装置的研制及其在筛分天然钻石中的应用

为了提高批量小颗粒钻石的筛查效率和准确性,研制了一种新型紫外光致发光图像高速采集装置——珠宝首饰观察鉴定仪(DDO),通过对激发光波长、工业相机等的选用和结构设计技术突破,以及对发光现象采集方式进行创新,实现了批量观察不同宝石间的光致发光现象和发光延迟现象差异等,从而实现对宝石高效检测。对20 000粒以上无色天然钻石、合成钻石和钻石相似品进行的DDO测试结果表明,98%~99%的无色天然钻石在紫外光激发光停止后的0.1~10 ms内可观察到的碧蓝色磷光现象,为天然钻石典型特征,合成钻石和其他无色宝石的发光特征(发光颜色、强度、持续时间、结构分区)明显区别于天然钻石,由此建立了一种通过观测包括荧光、衰减时间在100 ms内的连续发光(磷光)特征差异性作为筛分条件快速、准确筛分无色天然钻石的新方法。本装置提高了钻石鉴定的准确度和检测效率,对天然钻石的筛查通过率可高达99%,对合成钻石和仿钻石的筛查准确性可达100%。     

中国对虾黄、渤海沿岸地理群的RAPD分析

采用随机扩增多态DNA(random amplified polymorphic DNA,简称RAPD)技术,对中国对虾的黄、渤海地理群的32个个体遗传多样性进行了检测,使用OPI系列的20个10bp的寡核苷酸随机引物,对每个个体的基因组DNA进行扩增,结果为:17个引物获得了谱带清晰且重复性好的产物,扩增片段的分子量在2000～2000bp之间,共检测106个位点,其中多态位点数为39个,占36.8%;平均遗传距离为0.0941+0.0206,有67个标记(占63.2%)在整个群体的32个个体间表观稳定的一致性.     

中国北方苹果干旱等级指标构建及危险性评价

以中国北方苹果主产区为研究对象,利用1981-2018年气象资料、1981-2017年苹果干旱灾情历史资料和发育期资料,在构建干旱指数(D1)的基础上,以历史灾情反演、灾害样本重建和历史灾害过程解析为主线,采用独立样本T检验、Kolmogorov-Smirnov(K-S)检验、累积概率反函数值等方法,构建适用于中国北方...     

滆湖人工放流技术的改进及其效益分析

本文研究了滆湖1986—1988年人工放流主要鱼类的年龄组成、生长速度、肥满度、回捕率及其经济效益。青鱼、草鱼和团头鲂等主要放流种类的回捕率为23.85％—39.88％;鲢鳙鱼为8.20％—19.63％;中华绒螫蟹苗和蟹种分别为2.69％和48.57％。人工放流的产量效益平均为14.3倍,经济效益早均为9.6倍。