蛤蜊科3种贝类16SrRNA基因片段及ITS2核苷酸序列分析

利用PCR技术分别扩增连云港及启东沿海蛤蜊科的西施舌（Coelomactra antiquata）、中国蛤蜊（Mactra chinensis）和四角蛤蜊（Mactra veneriformis）3种双壳贝的16SrRNA基因片段和ITS2核苷酸序列．测序后用DNAstar软件分析了核苷酸差异。结果显示：三种贝类16SrRNA基因片段长度相同，均为306bp（去除引物）．核苷酸存在多态性。共有45个变异位点，54个核苷酸发生了变异。全部为碱基置换。西施舌与中国蛤蜊此片段核苷酸的同源性为88．9％．与四角蛤蜊的同源性为88．6％．中国蛤蜊与四角蛤蜊的同源性为90．6％。三种蛤蜊ITS2序列分别为390bp（西施舌）、441bp（四角蛤蜊）和466bp（中国蛤蜊）。存在长度多态性．ITS2核苷酸差异分析结果显示．西施舌与中国蛤蜊的同源性为70．9％-71．1％，西施舌与四角蛤蜊的为70．5％-71．0％。中国蛤蜊与四角蛤蜊的同源性为88．1％-88．8％。ITS2序列分析结果与16SrRNA基因片段分析结果一致．2种分子分析法均显示中国蛤蜊与四角蛤蜊的亲缘关系近。     

东昆仑清水泉蛇纹岩中铬铁矿环带成因

东昆仑造山带清水泉超基性岩已蚀变成蛇纹岩,部分浸染状铬铁矿颗粒具有环带结构,这将为研究铬铁矿形成后所经历的变质过程及其寄主岩体的构造演化提供可靠的信息.通过对铬铁矿进行显微结构观察和电子探针分析得出:所研究铬铁矿的环带结构从核部到边缘依次为铝铬铁矿、高铁铬铁矿和铬磁铁矿,被绿泥石所包裹.从铝铬铁矿到高铁铬铁矿,Cr2O3,Al2O3和MgO含量下降,Fe2O3和FeO含量升高;Cr#,TiO2含量,YFe值以及Fe2+#值明显具有升高的趋势,而Mg#值却急剧下降.以上变化规律表明本文所研究的铬铁矿经历了由高温到低温,同时氧逸度上升的过程,并伴随有蛇纹石化作用、热液流体以及区域变质作用等改造,最终形成环带结构.此过程与铬铁矿寄主岩体经历的由地幔抬升至浅部地壳以及相关的变质作用过程相对应.     

天山地震带空间集中度ΔC值演化特征

采用新疆地区1990年以来的浅源地震目录,利用扩散链法去除余震,在小震空间集中度C值的研究基础上,进一步发展了C值变化量,即ΔC值的时空扫描计算方法,针对2000年以来天山地震带11次6级以上地震前ΔC值的演化过程,进行回顾性研究.结果表明,2012年新源—和静交界MS 6.6地震、2017年精河MS 6.6地震和20...     

介质密度反演偏导矩阵的精确计算方法

实现反演偏导矩阵的计算是基于导数最优化反演方法的关键,然而目前的地震反演几乎都是基于Zoeppritz方程近似实现的,使计算精度和适应范围受到限制.本文利用Zoeppritz方程建立了反射系数对地层介质密度比偏导方程,导出了Zoeppritz方程矩阵元对介质密度比的导数.通过求解偏导方程获得了反射系数对介质密度比偏导数的精确计算(考虑了速度中含介质密度的问题).利用数值算例分析了反射系数对介质密度比偏导数的变化特点.本文采用直接解法求解偏导矩阵方程组,获得了快的计算速度和高的计算精度,为实现地层介质密度反演(包括大角度反演)提供了偏导矩阵的计算方法.     

A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection

To dates,most ship detection approaches for single-pol synthetic aperture radar(SAR) imagery try to ensure a constant false-alarm rate(CFAR).A high performance ship detector relies on two key components:an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm.First,a novel nonparametric sea surface distribution estimation method is developed based on n-order Bézier curve.To estimate the sea surface distribution using n-order Bézier curve,an explicit analytical solution is derived based on a least square optimization,and the optimal selection also is presented to two essential parameters,the order n of Bézier curve and the number m of sample points.Next,to validate the ship detection performance of the estimated sea surface distribution,the estimated sea surface distribution by n-order Bézier curve is combined with a cell averaging CFAR(CA-CFAR).To eliminate the possible interfering ship targets in background window,an improved automatic censoring method is applied.Comprehensive experiments prove that in terms of sea surface estimation performance,the proposed method is as good as a traditional nonparametric Parzen window kernel method,and in most cases,outperforms two widely used parametric methods,K and G0 models.In terms of computation speed,a major advantage of the proposed estimation method is the time consuming only depended on the number m of sample points while independent of imagery size,which makes it can achieve a significant speed improvement to the Parzen window kernel method,and in some cases,it is even faster than two parametric methods.In terms of ship detection performance,the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors,resolutions and sea surface homogeneities and obtains a leading performance on the test dataset.     

Characteristics of Lake Breezes and Their Impacts on Energy and Carbon Fluxes in Mountainous Areas

In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(F_{CO_2}) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_{CO_2}. For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange.     

Sedimentary Features and Their Implications of Microdigital Stromatolites from the Mesoproterozoic Wumishan Formation at the Jixian Section in North China

<正>The Mesoproterozoic Wumishan Formation at the Jixian section in Tianjin is a set of more than 3000-m-thick stromatolitic carbonate succession.In this succession,several lithofacies units,that is,the subtidal stromatolitic biostrome,the thrombolitic bioherm,tidal-flat micritic dolomite and lagoon dolomitic shale,make up many meter-scale cycles of the peritidal carbonate type that have been nominated as the Wumishan cycles.Importantly,many microdigital stromatolites make up the stromatolitic biostrome unit of the Wumishan cycles in the lower part of the Wumishan Formation. These microdigital stromatolites have been grouped as a stromatolitic assemblage by paleontologists, that is,"Pseudogymnosolen mopanyuensis-Scuphus-Yangzhuang columnaris"assemblage.These microdigital stromatolites had also been interpreted as the aragonite(tufa) sea-floor precipitates by sedimentologists,and has further been thought as the special products of the transitional period from the sea-floor aragonite precipitates of the Archean to the clastic and muddy carbonates of the Neoproterozoic.Although there are some restrictions for the stratigraphic meaning of the concept of the stromatolitic assemblage,detailed studies on classification by paleontologists provide an important clue to understand the sedimentological meaning of the microdigital stromatolites.Furthermore,an important and obvious horizon for the end of the microdigital stromatolites was recorded in the Mesoproterozoic Wumishan Formation at the Jixian section,which provides useful information to understand the stromatolite decline occurred at c.1250 Ma and the evolving carbonate world of the Precambrian.     

松花江上游地区汞污染的化学生态效应

采样分析了吉林省东部松花江上游金矿开采区及其附近水、土壤、动植物及河流沉积物样品中汞的含量，发现河流沉积物中汞的污染相当严重；受其影响当地的植物和两栖类动物——中国林蛙体内总汞和甲基汞含量也明显高于对照组。实验表明，林蛙内脏对汞的富集能力大于肌肉；秋季对汞的富集大于春季；河流沉积物中甲基汞的含量与林蛙体内甲基汞的含量有较好的正相关。汞污染的来源与区域内个体金矿的滥采滥排有直接关系，表明人类活动所产生的有毒重金属在地表过程中出现了化学生态效应。     

GNSS/地磁组合的室内外无缝定位平滑过渡方法

针对室内外无缝定位在室内外过渡点精度低、不能平滑自动切换等问题,结合GNSS定位技术以及室内地磁指纹节点的组合方法来实现室内外无缝定位及导航。由于从室外至室内时接收机接收到的卫星星数减少、GDOP值逐渐增加、定位的误差增大,因此室内地磁定位精度逐渐优于GNSS定位精度,在两个定位精度临界点通过分析计算得出GDOP最优转化范围值,进行平稳切换。此次试验仿真结果表明,GDOP在3~3.5进行切换与单一GNSS或地磁方法定位的精度相比,分别提高85.7%和82.6%,从而达到了室内外的高精度无缝定位,填补了国内外在室内外无缝定位上没有合适的切换界定的空白。     

蒙古国植被对干旱响应的敏感性研究

本文分析了蒙古国不同区域、不同土地覆被类型区的植被生长状况对干旱响应的敏感性特征,并探讨了成因。研究表明：① 2001—2019年,蒙古国虽然发生了3次较为严重的干旱事件,但整体上干旱程度呈轻微降低趋势,SPEI出现轻微上升,总体增速为0.001%/a;植被生长状况出现了好转,植被指数也呈上升趋势,总体增速为0.15%/a。② 蒙古国大部分区域植被生长受干旱影响较强,各植被指数与干旱指数呈较明显的正相关关系,在NDVI与SPEI-12的相关性分析中,正相关面积占比达76.36%;而在杭爱山脉和肯特山脉以北降水量丰沛的区域和阿尔泰山脉以南荒漠化严重和植被极为稀少区域,植被生长受干旱影响较弱,植被指数与SPEI相关性较小。③ 不同类型植被对干旱响应的敏感性也有差异,其中草地敏感性最强（0.22）,而森林敏感性最弱（-0.04）。④ 干旱持续时间长短,对植被生长影响有较大差异,蒙古国大部分区域的植被对延续3个月至半年的干旱最为敏感,而年内以7月份干旱对植被影响最强。⑤ 植被对干旱响应的敏感性实质是区域水分平衡的植被影响,对同种植被而言多年平均气温越高或降水量越少,植被对干旱响应的敏感性越强,反之则越弱。本文的研究结果对蒙古国因地制宜开展荒漠化防治具有重要参考价值。