Distribution of free electrons in the galactic plane

A method is proposed for constructing a map of the electron density distribution in the galactic plane. Data on the dispersion measures DM of more than 1500 pulsars and their distances, found by an independent method, are used. The independent distances of the pulsars are estimated using an empirical relation of the form L=γP ^α Ṗ ^β W ^δ between the radio luminosity L of the pulsars and their periods P, the rate of change Ṗ. of their periods, and the half width W of their pulses. A map of the electron density distribution in the galactic plane within a ±400 pc layer is provided. __________ Translated from Astrofizika, Vol. 49, No. 2, pp. 277–287 (May 2006).     

Temporal and cross-shelf distribution of ichthyoplankton in the central Cantabrian Sea

Environmental variables have been measured and sampling for ichthyoplankton has been conducted monthly, since April 2001, at three stations, located at the inner (1), middle (2) and outer (3) shelf of the central Cantabrian Sea. This paper presents the results of the study of the ichthyoplankton collected from July 2001 to June 2004. Fish larvae from 99 species, belonging to 37 families, were identified. Families with higher number of species were Gadidae, Sparidae and Labridae. The larval fish assemblage was dominated by pelagic fish species, with Sardina pilchardus, as the most abundant. There was a pronounced spring peak in larval abundance, dominated by S. pilchardus. A smaller peak, dominated by S. pilchardus and Micromesistius poutassou, was recorded in late winter at Stns 2 and 3. This pattern was evident for the three-year study. Results also indicate that this study was limited to the coastal larval fish assemblage inhabiting the central Cantabrian Sea shelf. This assemblage was temporally structured into other three assemblages: winter, late winter–spring and summer–autumn. Temperature was apparently a key factor in larval fish assemblage succession. In a scenario of global warming, this study constitutes a basis to evaluating the ongoing changes in the pelagic coastal ecosystem of the central Cantabrian Sea.     

北黄海典型水域春夏季浮游植物的昼夜变化

根据黄海西北部2006年夏季3个连续站和2007年春季1个连续站垂直分层拖网的调查资料,研究了黄海西北部典型海区浮游植物的昼夜垂直变化.夏季共检出浮游植物79种,主要优势种为旋链角毛藻Chaetoceros curvisetus、梭角藻Ceratium fusus、三角角藻Ceratium tripos和具槽帕拉藻Paralia sulcata;春季检出51种,主要优势种为浮动弯角藻Eucampia zodiacus、具槽帕拉藻和尖刺伪菱形藻Pseudo-nitzschia pungens.夏季L01站受潮汐的影响各水层低潮期浮游植物细胞丰度高于高潮期,垂直分布趋势为表层细胞丰度最高,底层最低.而由于底栖硅藻的细胞再悬浮作用夏季L02、L03站和春季L02站底层细胞丰度高于表层,但各水层细胞丰度的昼夜变化相对较平缓.     

山东近海溶解态无机营养盐的分布特征研究

根据2006年8月、12月和2007年4月、10月山东近海海区4个航次海水中溶解无机营养盐等的调查资料,分析了该海域5种溶解无机营养盐(包括PO4-P,NO3-N,NO2-N,NH4-N,SiO3-Si)的平面分布和时空变化特征.结果表明,5种营养盐在胶州湾内出现高值,平面分布整体上呈现沿岸浓度高、外海浓度低的趋势;根据绝对限制和相对限制法则,春季和夏季P为限制因子,秋冬季营养盐结构发生变化,由缺P向缺Si转变;SiO3-Si浓度随季节变化逐渐增加,其他营养盐浓度在春季和夏季较低,秋季达到最大值.秋冬季溶解无机营养盐周日变化受潮汐影响明显.     

海洋鱼类分子系统地理学研究进展

简要叙述了分子系统地理学的发展简史、研究内容,重点介绍了Avise的5种物种分布模式及中性溯祖理论。并回顾了近年来分子系统地理学的研究进展及其在海洋鱼类研究中的应用,最后对海洋鱼类分子系统地理学研究进行了展望。     

A bimodal four‐parameter lognormal linear model of soil water repellency persistence

Soil water repellency may be characterized in terms of the delayed infiltration time of a water droplet resting on the soil surface, which is, water drop penetration time (WDPT), or repellency persistence. Such repellency persistence varies nonlinearly with soil water content (θ_g), although no models have been proposed to reproduce the variation of WDPT with θ_g in soils. Dynamic factor analysis (DFA) is used to identify two common patterns of unexplained variability in a scattered dataset of WDPT versus θ_g measurements. A four‐parameter lognormal distribution was fitted to both common patterns obtained by DFA, and these were combined additively in a weighted multiple linear bimodal model. We show how such an empirical model is capable of reproducing a large variety of WDPT versus θ_g curve shapes (N = 80) both within a wide range of measured WDPTs (0–17 000 s) and for samples with organic matter content ranging from 21·7 to 80·6 g (100 g)^?1. Copyright © 2009 John Wiley & Sons, Ltd.     

东营凹陷低渗透油藏分布规律及储层改造效果

东营凹陷2001年之前探明的低渗透油藏主要分布在洼陷带、中央背斜带及北部陡坡带,以沙三段深水浊积扇及沙四段滨浅湖相砂岩滩坝、扇三角洲前缘等沉积体系为主。油藏类型主要是岩性油藏,其次为构造—岩性复合型油藏。低渗透油藏以中深层、常压-超高压、低产、中产为特征,多为特小型、小型油藏,储量丰度为低丰度~特低丰度。低渗透油藏的探井试油过程中,经历了从酸化逐步到压裂的技术发展过程。统计探井的试油效果表明,沙四段碳酸盐含量较高的砂岩低渗透油藏,酸化效果较好;黏土含量较高的沙三段低渗透油藏,压裂效果较好。     

集聚型空间点模式结构信息提取研究

空间点模式是一个2维离散点集,点集中的每一个元素代表地球表面一个点状目标的空间位置。当2维离散点集具有集聚特征时,称其为集聚型空间点模式,它与空间聚类、制图综合和空间分析的许多具体应用紧密相关。如何提取集聚型空间点模式的结构信息(集聚子群的个数和对应的集聚中心)是其中尚未彻底解决的问题。作者以几何概率为理论基础,提出测度正方形区域内2维离散点集分布特征的H函数并推导其解析表达式,运用H函数设计和实现了集聚型2维离散点集结构信息提取的通用算法。利用该算法处理一个由居民地坐标数据得到的具有集聚特征的空间点模式,提取出其结构信息并进行可视表达。分别以该空间点模式中的各离散点为顶点和发生元生成Delaunay三角网和Voronoi图,在Delaunay三角网中保留面积最小的前1/10、前1/100三角形的顶点,在Voronoi图中保留面积最小的前1/10、前1/100邻近多边形的发生元,将可视表达的点集结构信息分别与依据Delaunay三角网和Voronoi图得到的结果进行对比分析。结果表明,运用H函数能够有效地提取出集聚型空间点模式的全局性结构信息,而Delaunay三角网和Voronoi图虽然能够反映其局部密度,但在提取全局结构信息时存在局限性。     

Coherent Chemical Variation Trends of the 55-25 Ma Magmatic Rocks in SE Tibet:N-S Direction Lithospheric Stretching of Eurasia during Early Stage of India-Eurasia Collision

The progressive indentation of India into Eurasia generated an E–W-trending orthogonal collision belt and a N–S-trending oblique collision belt. Compiling available data reveals that ～70% of the Cenozoic igneous rocks in eastern and southeastern Tibet are concentrated within an ENE-trending, ～550-km long and ～250-km wide magmatic zone(CMZ) that once separated the orthogonal and oblique collision belts. The Latitude 26°N Line is now its southern boundary. The onset timing of magmatism of the CMZ ...