Vertical distribution of living mangrove foraminifera from KwaZulu-Natal,South Africa

Modern foraminiferal assemblage zones can be used to reconstruct palaeo sea levels when applied to fossil foraminifera down a sediment core. Previous intertidal foraminiferal studies have predominantly focused on assemblages in surface sediments (0–1 cm), with the rationale that surface assemblages reflect the modern-day environment. Foraminifera live infaunally and therefore there is a need to document the infaunal vertical distribution of living foraminifera to fully capture the modern environment. Infaunal foraminiferal populations may compositionally differ from or be similar to those in the uppermost 1 cm of a core sample, but abundance is variable vertically, making it very complex to reconstruct and interpret past sea levels. This can have implications for the choice of assemblages to use as modern analogues for past sea-level reconstructions. This study documents the vertical infaunal distribution of living foraminifera, to allow for more informed interpretations of palaeo-reconstructions in mangrove environments. The down-core vertical distribution and abundance of living foraminifera, along with grain size and organic content, were documented using sediment cores along an elevational transect. Nine taxa were recorded as living at the time of collection, six of which were restricted to the top 4 cm. The majority of these were calcareous and found in the cores situated closer to the intertidal channel. Therefore, we argue that the diversity of living calcareous and agglutinated foraminifera could be restricted by grain size, with coarser grain sizes associated with lower species diversity. The findings suggest that foraminiferal species inhabiting the top 4 cm represent deeper living foraminiferal populations. Therefore, the top 4-cm interval can be used to establish a modern training set upon which reconstructions can be based. The findings from this study will provide guidance on the use of South African mangrove environments for future sea-level reconstructions.     

利用纳米透射X射线显微成像技术研究页岩有机孔三维结构特征

页岩纳米级孔隙的三维结构特征直接决定页岩气微观渗流机理,是完善页岩储层流动模型亟需解决的核心问题。本文以龙马溪组页岩有机孔样品(直径约7μm)为研究对象,分别利用同步辐射纳米CT和实验室纳米CT重建有机孔三维空间结构,针对两个装置获得的孔隙结构参数进行对比研究,结果表明:(1)龙马溪组页岩有机孔样品呈蜂窝状,孔隙度约60%,连通性较好;孔径分布呈双峰模式,集中于60~150nm和500~1400 nm;孔径大于500 nm的孔隙对样品的总孔隙度贡献较大。(2)同步辐射纳米CT与实验室纳米CT结果相较,孔隙度和孔隙总数两参数基本一致,喉道总数和喉道半径偏差较大;孔径分布和配位数分布规律虽然类似,但具体数值存在明显差异,值得进一步深入比较分析和研究。(3)纳米CT方法在页岩纳米孔隙三维结构表征方面存在阈值划分难度大与扫描视场过小的问题,可从切片重构算法、三维数据处理、表征单元体三方面进行改进。     

Stratigraphic reconstruction of the Strzelecki Group outcrops in west Gippsland: new data on the present-day thickness and amount of erosion

The Lower Cretaceous Strzelecki Group forms the basement to the eastern part of the Gippsland Basin, but is exposed in the west and forms spectacular outcrops, especially along the coastal area between San Remo and Inverloch. The coastal area is highly faulted and lacks stratigraphic markers so matching sections in different fault blocks based only on lithology has not been possible. A combination of mapping, detailed logging, vitrinite reflectance measurements and palynology were used to determine the present-day thickness of the coastal sections and the amount of erosion that occurred during the Late Cretaceous. A total thickness of about 1500 m is inferred between Harmers Haven and Inverloch but because of the amount of faulting and probable repeated sections, the true thickness of Strzelecki Group exposed in the coastal outcrops is only about 300 m. Based on palynology and vitrinite reflectance results, the reconstructed Strzelecki Group stratigraphy has been subdivided into three distinct ‘bio-blocks’, with an eroded section estimated to range from 1.5 km (0.3–2.6 km at ±95% confidence limits) to 2.7 km (2.2–3.1 km at ±95% confidence limits).     

生态水文阈值在中国沙区人工植被生态系统管理中的意义

中国北方风沙区是全球沙漠化发展和生态退化最为严重的地区之一。利用植被固沙是遏制沙化土地扩张和生态重建与恢复的主要途径,但人工植被的稳定维持是可持续性风沙治理所长期面临的挑战。作为人工植被生态系统管理的依据,对生态水文阈值的认识及界定具有重要的理论和实践意义。本文以固沙植被中人工种植的灌木和乔木（仅限东部沙区）的盖度与深层土壤水分含量互馈互调作用的长期变化为依据,基于对中国不同气候带沙区典型人工植被系统生态和水文过程的模拟,通过建立生态水文模型初步界定了不同沙区适宜于人工植被生态系统管理的生态水文阈值,对现有沙区固沙植被的生态系统管理和未来风沙区植被建设具有一定的借鉴意义。     

Crop cover reconstruction and its effects on sediment retention in the Tibetan Plateau for 1900–2000

Geographically explicit historical land use and land cover datasets are increasingly required in studies of climatic and ecological effects of human activities. In this study, using historical population data as a proxy, the provincial cropland areas of Qinghai province and the Tibet Autonomous Region (TAR) for 1900, 1930, and 1950 were estimated. The cropland areas of Qinghai and the TAR for 1980 and 2000 were obtained from published statistical data with revisions. Using a land suitability for cultivation model, the provincial cropland areas for the 20th century were converted into crop cover datasets with a resolution of 1 × 1 km. Finally, changes of sediment retention due to crop cover change were assessed using the sediment delivery ratio module of the Integrated Valuation of Ecosystem Services and Trade-offs (In- VEST) model (version 3.3.1). There were two main results. (1) For 1950–1980 the fractional cropland area increased from 0.32% to 0.48% and land use clearly intensified in the Tibetan Plateau (TP), especially in the Yellow River–Huangshui River Valley (YHRV) and the midstream of the Yarlung Zangbo River and its two tributaries valley (YRTT). For other periods of the 20th century, stability was the main trend. (2) For 1950–1980, sediment export increased rapidly in the Minhe autonomous county of the YHRV, and in the Nianchu River and Lhasa River basins of the YRTT, which means that sediment retention clearly decreased in these regions over this period. The results of this assessment provide scientific support for conservation planning, development planning, or restoration activities.     

我国海洋法律体系的重构——以海权为中心

在反思我国现有海洋法律体系的基础上,指出海洋法律体系的构建必须着眼未来,运用评价法学的法伦理原则和理性主义的建构思路加以阐发,建立以维护和发展海权为核心的,以海洋基本法主要内容的,国家和地方海洋法律法规相结合的,国际法和国内法相衔接的多层次、立体化的现代法律体系。     

基于泊松碟采样的地震数据压缩重建

在地震资料处理领域,数据的压缩和重建是非常重要的问题,但往往由于数据的严重缺失或采样原因而达不到理想的效果.新发展起来的压缩感知理论为重建欠采样数据提供了可能,而选用合适的采样方法是其中的关键技术之一.本文基于傅里叶变换和压缩感知理论,采用泊松碟采样,对不完整地震数据进行恢复重建.数值实验表明,与传统的单纯随机采样方法相比,泊松碟采样方法在保持采样随机性的同时,使采样点的分布更加均匀,有效地调节了采样间距,从而达到更好的恢复效果,可以有效地指导地震数据采集设计及重建.     

16层螺旋CT重建在距骨骨折的应用价值

目的:研究16层螺旋CT多平面(MPR)、三维(3D)重建在距骨骨折中的临床应用价值。资料与方法:对132例距骨骨折患者的X射线平片、16层螺旋CT-MPR、3D重建影像资料对比分析。结果:132例距骨骨折中,16层螺旋CT-MPR、3D重建骨折和脱位全部显示,X射线平片查出骨折99例,脱位31例。骨折X射线平片检出率75%,三维重建检查检出率100%,脱位X射线平片检出率87%,三维重建检查检出率100%。结论:16层螺旋CT多平面和三维重建,可更好地显示距骨骨折和脱位,对术前诊断和治疗有很大价值,尤其是对距骨细微骨折和半脱位的诊断。     

多层螺旋CT后处理技术对气管支气管异物的诊断价值

目的:评价多层螺旋CT三维重建及仿真内窥镜技术对气管支气管异物的诊断价值。方法:对20例支气管异物、1例气管异物、1例先天性气管性支气管发育异常、1例气管良性肿瘤患儿行多层螺旋CT检查并进行三维重建及仿真内窥镜技术显示气管支气管病变;三维重建技术包括多平面重建、最大密度投影、最小密度投影、表面遮盖显示和容积再现,CT仿真内窥镜对气管支气管异物的显示与支气管镜所见具有一致性。结果:多层螺旋CT三维重建及仿真内窥镜可准确、直观地显示气管支气管异物的位置、大小、形态、密度及阻塞程度。结论:多层螺旋CT三维重建及仿真内窥镜可准确评价气管支气管异物,是一种准确无创性诊断方法,为临床治疗提供直观的影像学资料,具有较高的临床诊断及指导价值。     

数字合成X射线体层成像的小波-伽辽金重建算法

数字合成X射线体层成像技术的重建问题是在有限投影数据条件下的病态重建问题。本文通过分析数字合成X射线体层成像技术的系统模型,获得重建问题的系统方程。在对系统方程进行正则化改造的基础上,提出了一种新的重建算法——自适应小波-伽辽金重建算法。该算法融合了伽辽金方法的计算简洁和小波内在的多尺度特性,更好地适应了待重建图像的求解。仿真实验结果表明,与ART重建算法相比,自适应小波-伽辽金重建算法在保证重建质量前提下能加快收敛,从而大大地节省了计算时间。