Cloning and characterization of a delta-6 desaturase encoding gene from Nannochloropsis oculata

A gene(NANOC-D6D) encoding a desaturase that removes two hydrogen atoms from fatty acids at delta 6 position was isolated from a cDNA library of Nannochloropsis oculata(Droop) D.J.Hibberd(Eustigmatophyceae).The unicellular marine microalga N.oculata synthesizes rich long chain polyunsaturated fatty acids(LCPUFAs),including eicosapentaenoic acid(20:5n-3,EPA).The deduced protein contains 474 amino acids that fold into 4 trans-membrane domains.The neighbor-joining phylogenetic tree indicates that NANOC-D6D is ...     

关联矩阵法与城市宜居指标的结构关系度量——以中国老年人宜居城市评价指标体系为例

城市宜居环境综合评价本质上是城市内部包括物质空间、社会文化空间等众多要素之间的结构关系研究。城市系统结构可以分为不同的亚系统,亚系统之间的关系可以用数量方法确定。以中国老年人宜居城市评价指标体系为例,介绍和比较了各种宜居环境评价指标体系指标赋权的方法,应用关联矩阵法确定老年人城市宜居环境各亚系统之间,以及亚系统内部各个指标的重要性。旨在说明关联矩阵法在确定城市结构中各亚系统关联度上具有合理、简便的特点,尤其是具有将客观性与主观性评价相结合的优势。     

A probe heat flow value of the East China Sea shelf

Bottom temperature variation (BTV) is a serious problem in determining the thermal gradient and heart flow of the sediments in shallow seas. The water depth of the East China Sea shelf is mostly below 150m, and the heat flow measurement is strongly affected by BTV. Following a statistical algorithm, we rechecked the temperature and thermal conductivity data of the cruises KX90-1 and KX91-1, carried out by a cooperation program of China and Japan, and calculate the heat flow in a site without long-term temperature record. The calculated heat flow in the site was 58.6±3.6 mW/m², being just within the range of the drill heat flow value of East China Sea shelf. The inversed amplitude spectrum of BTV has a peak in frequency of 1/10 per year, and the annual component is also an important part. Comparison with two lakes of Lake Greifensee and Lac Leman (i.e. Lake Geneva), which are in different water depth, revealed that with increasing water depth, the peak of amplitude spectrum moved towards low frequency components. The heat flow values calculated in this paper and from petroleum bore hole in East China Sea shelf are much more close to that in southeast China than in Okinawa Trough. Supported by the National High Technology R&D Program of China (2004 AA616060)     

Prediction and verification of earthquakes induced by the Xiluodu hydropower station reservoir

Research has been conducted on reservoir-induced earthquakes in China since the Xinfengjiang reservoir-induced earthquakes in the 1960s. Regulations now require the risk of reservoir-induced earthquakes to be evaluated in the pre-research stage of all hydropower projects. Although nearly 40 cases of reservoir-induced earthquakes have been reported in China, analyses comparing the changes in seismic activity following reservoir impoundment with predictions are rare. In this study, we compared seismic activities observed in the reservoir area before and after the impoundment of the Xiluodu hydropower station in terms of the spatial distribution, frequency, and focal depths of the earthquakes, and clarified the correlation between their frequency/timing and reservoir level after impoundment. We then concluded that the seismic events in the head region were karst-type earthquakes, while those in the second segment of the reservoir were tectonic earthquakes. The spatial distribution of the earthquake epicenters and the seismic intensities validated some of the results for the reservoir-induced seismic risk assessment for the Xiluodu hydropower station, indicating that the proposed earthquake triggers and predictive models are reasonable. This study can provide a valuable reference for investigating the mechanism (s) of reservoir-induced earthquakes, revising reservoir-induced earthquake hazard assessment codes, and predicting the hazard zones of reservoir-induced seismicity under similar conditions.     

东平湖水体透明度的遥感反演研究

针对传统水体透明度测量方法不仅耗时费力,而且在时间和空间的监测中也会受到很大的限制,只能了解研究区域内点状剖面的透明度状况,但是遥感技术的发展为解决传统采样方法的局限性问题提供了可能。该文在分析内陆湖泊水体光学特征的基础上,利用三期Landsat8 OLI影像数据及准同期的地面实测数据,寻找与东平湖水体透明度敏感的波段,对东平湖丰、平、枯水期水体透明度的进行遥感反演研究。结果表明,OLI影像B3、B4波段的反射率与实测的透明度数据之间具有良好的相关关系,并以此为基础建立了该区域水体透明度遥感反演模型。结果表明:模拟值与实测值的总体相对误差为19.77%,均方根误差为19.35cm,模型精度在可以接受的范围之内;由于受围网养殖、叶绿素a含量等因素的影响,东平湖透明度总体呈现出南低北高的分布趋势。据此绘制了东平湖丰、平、枯水期水体透明度分布图。     

国家森林公园空间分布格局及其影响因素研究

国家森林公园是我国生态文明建设的重要载体之一。以1994、2004年和2019年国家森林公园为研究对象,综合运用空间分析技术系统探究其空间分布格局及成因,旨在为国家森林公园空间布局优化和健康可持续发展提供科学参考。结果表明：（1）国家森林公园主要分布在胡焕庸线以东,大致形成了以京津冀、长三角、川渝交界和湘赣交界地区为核心的高密度分布地区,呈现出“大集聚、小分散”的分布格局。（2）国家森林公园系统分形特征明显,分形结构较为复杂。（3）国家森林公园省际间分布差异明显,三大地带间呈现东西少、中部多的“凸字形”分异规律,八大分区间呈现“由长江中下游、西南地区向东北和黄河中游地区递减”。（4）国家森林公园热点区呈现出一定的不稳定性,其中黑龙江、江苏和浙江发展较为活跃,持续保持在热点区域,而新疆、西藏和四川等地基本上都处于冷点区域,森林公园发展较为缓慢。（5）地形、降水量、客源市场和旅游资源禀赋是影响国家森林公园空间分布格局的主要因素。     

京藏高速青海东部地区汛期路面水膜厚度变化特征及预报模型构建

利用2018—2020年汛期（5—9月）京藏高速青海省公路沿线交通自动监测站逐小时气象观测资料,研究路面水膜厚度变化特征,构建水膜厚度与气象因子的预报模型。结果表明：（1） 京藏高速公路高庙桥站和汉庄村站逐小时路面水膜厚度主要分布均在0.0~0.2 mm之间,频率分别为66.0%和63.0%,大于0.5 mm以上的路面水膜厚度频率均较小（10.0%）,2站均属于强变异性地区。（2） 采用相对阈值法统计分析,发现2站路面水膜厚度在0.1 mm以内的比例分别为33.8%和36.3%,路面水膜厚度在0.1~0.6 mm之间的比例分别为59.2%和56.0%,路面水膜厚度大于0.7 mm以上即易发生水滑,引起车辆失稳、失控等危险的比例分别为7.0%和7.6%。（3） 路面水膜厚度日变化和月变化特征明显。高庙桥站和汉庄村站水膜厚度的月变化均呈弱双峰性,2站的月变化趋势不完全一致。高庙桥站的日变化峰值出现在02:00—06:00,低谷出现在14:00—16:00,汉庄村站日变化峰值出现在06:00,低谷出现在16:00。（4） 随着降水强度的增加,平均水膜厚度均遵循幂函数关系迅速增加;在降水强度0.00~1.75 mm·h^-1之间时,平均水膜厚度增加趋势明显,降水强度大于1.76 mm·h^-1平均水膜厚度变化有增有减。（5） 采用多元回归统计方法建立依据气象因子和不同降水强度下分别构建的水膜厚度模型具有较好的使用价值,可在实际业务工作中推广应用。（6） 不同降水强度下构建的水膜厚度模型计算值明显高于季天剑模型和罗京模型,本文模型与罗京模型变化趋势较为一致,水膜厚度随降雨强度增加增长趋势明显,季天剑模型水膜厚度计算值随降雨强度增加增长趋势缓慢。研究成果可应用于高原环境雨天车速管理和路面交通安全管理,能够为公路设计人员或运营管理人员提供辅助决策的依据。     

页岩气储层测井评价有关问题的探讨

页岩气是存在于页岩中的非常规的天然气,测井是评价页岩气储层的一种不可缺少的方法.通过对煤田测井、煤层气测井、页岩气测井的比较,认为现有的测井方法能够准确定性页岩气储层及厚度.结合国内外页岩气测井实践,对页岩气储层的测井评价有关问题进行了探讨,包括页岩气储层的含气量确定,页岩层的裂缝、缝隙、孔隙度、渗透系数等,另外提出了矿物组成、脆性、力学性质、岩层产状等技术指标的测井评价方法.为了适应页岩气大规模开发,测井的定量评价的精度有待于提高,评价的方法有待于丰富.     

轮古西奥陶系潜山洞穴型岩溶储层发育特征与充填规律

洞穴型岩溶储层是塔里木盆地轮古油田缝洞型碳酸盐岩油藏的主要储集空间类型,多数高效井均钻遇大型洞穴型岩溶储层。依据轮古西奥陶系潜山大量单井资料分析,洞穴型岩溶储层可分为充填洞穴、半充填洞穴和未充填洞穴三种类型。结合古地貌精细刻画与岩溶垂向分带成果,认为古地貌位置由岩溶台地向岩溶缓坡和岩溶盆地逐渐降低,而洞穴发育和充填程度在逐渐增高。未充填与半充填洞穴主要发育在岩溶台地和岩溶缓坡的溶峰边坡、溶丘边坡及沟槽谷洼地边坡等地貌单元。表层岩溶带、径流溶蚀带洞穴型岩溶储层发育频率最高,其次为垂直渗滤带和潜流溶蚀带。未充填与半充填洞穴型岩溶储层主要发育在表层岩溶带。