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301.
为了探索北极陆域真菌的多样性,进一步揭示其生态学角色,本研究对中国第5次北极科学考察采集自黄河站区附近的24份样品进行了真菌的分离培养及鉴定,样品涂布划线后共分离得到60株真菌,其中腐殖质样品中分离到的真菌种类和数量最多;对选取的28株代表菌株进行了真菌ITS区序列鉴定,结果表明它们分属于4个纲,12个属,分别为散囊菌纲、粪壳菌纲、座囊菌纲和微藻菌纲,其中地丝霉属为优势类群。该结果表明北极地区具有丰富的真菌物种多样性。通过对代表土壤理化性质的测定,探究了真菌多样性和土壤理化参数的相关性,其中有机碳氮及可溶性营养盐含量是影响北极土壤真菌多样性的重要指标。 相似文献
302.
Junjie Yi Di Xu Xiaonan Zang Dingyang Yuan Bingran Zhao Li Tang Yanning Tan Xuecheng Zhang 《中国海洋大学学报(英文版)》2014,13(3):497-502
Arthrospira platensis is an economically important cyanobacterium; and it has been used widely in food and pharmaceutical industries. The phycocyanin(PC) from A. platensis is extremely valuable in medicine and molecular biology due to its antioxidation and anti-tumoring activity and applicability as fluorescence protein tag. In present study, two recombinant plasmids, one contained the phycocyanobilin(PCB)-producing genes(hox1 and pcyA) while the other contained the phycobiliprotein gene(cpcB) and the lyase gene(either cpcS/U or cpcT), were constructed and synchronically transferred into E. coli in order to test the the activities of relevant lyases for catalysing PCB addition to CpcB during synthesizing fluorescent PC holo-β-subunit(β-PC) of A. platensis. As was evidenced by the fluorescence emitted at a peak specific for PC, CpcB was successfully synthesized in E. coli, to which co-expressed PCBs attached though at a relatively low efficiency. The results showed that the attachment of PCBs to CpcB were carried out mainly by co-expressed CpcS/U but CpcB also showed some autocatalytic activity. Currently, no CpcT activity was detected in this E. coli expression system. Further studies will be conducted to improve the efficiency of fluorescent PC synthesis in E. coli. 相似文献
303.
Statistical analysis of thunderstorms on the eastern Tibetan Plateau based on modified thunderstorm indices 总被引:1,自引:0,他引:1
The Tibetan Plateau, with an average altitude above 4000 m, is the highest and largest plateau in the world. The frequency of thunderstorms in this region is extremely high. Many indices are used in operational forecasting to assess the stability of the atmosphere and predict the probability of severe thunderstorm development. One of the disadvantages of many of these indices is that they are mainly based on observations from plains. However, considering the Plateau's high elevation, most convective parameters cannot be applied directly, or their application is ineffective. The pre-convective environment on thunderstorm days in this region is investigated based on sounding data obtained throughout a five-year period(2006–10).Thunderstorms occur over the Tibetan Plateau under conditions that differ strikingly from those in plains. On this basis,stability indices, such as the Showalter index(including SI and SICCL), and the K index are improved to better assess the thunderstorm environments on the Plateau. Verification parameters, such as the true-skill statistic(TSS) and Heidke skill score(HSS), are adopted to evaluate the optimal thresholds and relative forecast skill for each modified index. Lastly, the modified indices are verified with a two-year independent dataset(2011–12), showing satisfactory results for the modified indices. For determining whether or not a thunderstorm day is likely to occur, we recommend the modified SICCLindex. 相似文献
304.
黄河源区拥有独特的生态系统和生物资源,是我国重要的江河水源涵养地和重要的生态屏障。近年来,放牧家畜数量的增加使该地区传统草地畜牧业面临过度放牧、草地退化、季节性失衡等发展难题。为科学掌握黄河源区放牧家畜的情况,本文以黄河源区的玛多县为研究区,应用无人机对玛多县放牧家畜(牦牛、藏羊和马)的数量和空间分布开展航拍调查。根据牦牛、藏羊和马的无人机图像解译标志库进行目视解译,采用5种方法估算玛多县放牧家畜的数量,利用选择指数分析家畜空间位置与环境因子的关系,结果表明:① 在冷季无人机航拍样带内,牦牛、藏羊和马的样带密度分别为4.12、7.34和0.06 只/km2。② 玛多县有牦牛7.08万头,藏羊10.22万只,马0.12万匹,经验证,估算牦牛、藏羊和马数量的误差分别为-0.93%、2.27%和-13.23%。③ 家畜对环境因子的选择倾向于坡度小于12°,草地覆盖度高于0.6,距居民点小于1 km,距水源小于 3 km,距公路大于3 km的区域。研究结果表明,无人机遥感技术在畜牧业方面有较大的应用潜力,为研究牧区放牧家畜的特征和草畜平衡情况提供新的思路。 相似文献
305.
The relationship between the East Asian winter monsoon (EAWM) and East Asian summer monsoon (EASM) during the Holocene is complicated and remains controversial. In this study, analysis of grain size and benthic foraminiferal oxygen isotope, as well as accelerator mass spectrometry 14C dating was performed on a sediment core retrieved from the newly revealed muddy deposit on the northern South China Sea continental shelf. The history of the EAWM and EASM were reconstructed for the last 8200 a BP. Further analysis in conjunction with previously published paleo-climate proxies revealed that the relationship between the EAWM and EASM during the Holocene is more complex than a simple and strict anti-phase one-both negative and positive correlations were identified. The EAWM and EASM are negatively correlated around 7500, 4800, 4200, 3200, and 300 a BP (cooling periods), while positively correlated around 7100, 3700, and 2100 a BP (warm periods). In particular, both the EAWM and EASM intensified during the three positive correlation periods. However, we also found that the relationship between these two sub-monsoons is anti-phase during the final phase of particularly hot periods like Holocene Optimum and Medieval warm period. The possible impact from variations of solar irradiance on the relationship between the EAWM and EASM was also discussed. 相似文献
306.
307.
308.
辽西地区建昌盆地含有丰富的油页岩资源。利用野外露头、钻井和化验分析等资料,分析油页岩分布、岩石学特征、地球化学特征和沉积环境。研究表明:油页岩发育于下白垩统九佛堂组一段、二段和三段,共计9个矿组,九佛堂组三段油页岩平均含油率高、厚度大;建昌盆地油页岩平均含油率为5.15%,平均灰分质量分数可达81.9%,平均发热量为5.19 kJ/g,全硫质量分数低,属于中品位高灰分中高发热量低硫型油页岩,开发时对环境污染小;碱厂、五家子、九佛堂、七道泉子和敖汉旗大青山含矿区累计油页岩查明技术可采资源8.22×108 t,油页岩油查明可回收资源3.17×107 t,建昌盆地预测油页岩资源9.27×1010 t。有机地化特征显示,建昌盆地油页岩有机质丰度较高,有机质类型主要为Ⅰ型和Ⅱ1型,成熟度较低,处于未成熟—低成熟阶段。九佛堂组时期气候温暖湿润,来源于陆地和湖泊的有机质大量沉积于淡水—咸水的湖泊中,水底为还原环境,有利于有机质的保存。 相似文献
309.
Using the layered viscoelastic medium model, this paper calculated the coulomb stress loading effect on the Lushan epicenter generated by the Wenchuan earthquake. Then combined with the rate-state friction law proposed by Dieterich J. (1994), we obtain the probability of an MW ≥ 6.0 earthquake occurring in the vicinity of Lushan. The results show that the probability of MW ≥ 6.0 earthquake of the Lushan region in 2013 is up to 18%, indicating that the stress disturbance caused by the Wenchuan earthquake accelerated the Lushan earthquake. This paper also calculates the coulomb stress accumulation on the "seismic gap" generated by the two earthquakes of Wenchuan and Lushan, and combined with the background seismicity, gives the MW>6.0 earthquake probability of the "seismic gap". Although there may be a certain error in the results because of the Dayi earthquake, selection of the medium model parameters and background seismicity, the seismic probability of the "seismic gap" is increasing. Thus, we think destructive earthquakes are still likely to occur in the "seismic gap". 相似文献
310.
Yue Li Shijin Zhao Hongye Pei Shi Qian Jingjie Zang Xinyue Dang Huan Yang 《中国科学:地球科学(英文版)》2018,61(7):925-939
Glycerol Dialkyl Glycerol Tetraethers(GDGTs)serve as important tools for the quantitative reconstruction of paleoclimate and paleoecology in both continental and marine environments.Previous studies of GDGTs in the terrestrial environments focused primarily on the soils from the relatively warm-humid or cold-dry regions.However,it is still unclear how GDGTs respond to environmental variables in the cold-humid regions.Here,we collected soils along an altitudinal transect of Mountain(Mt.)Changbai,which has a typical cold-humid climate,to investigate the distribution of GDGTs and the response of GDGT-based proxies to changes in climate along the transect.The shift in the distribution of archaeal isoprenoidal GDGTs(iso GDGTs)revealed that the archaeal community varied significantly along the transect,which can affect the relationship between TEX_(86)and mean annual air temperature(MAT).In addition,the increased temperature seasonality at higher altitudes exerted a significant impact on TEX_(86).We proposed a global calibration of TEX_(86)for the growing season temperature reconstruction in the soil environments:T=85.19×TEX_(86)-46.30(R~2=0.84,p0.001).The methylation indices for 5-methyl branched GDGTs(br GDGTs)including MBT′_(5me)and MBT_(5/6),showed correlation with soil water content but no relationship with MAT,indicating that MBT′_(5me)and MBT_(5/6)from cold-humid environments may be not suitable for temperature and altitude reconstruction.In contrast,the recently developed p H proxies,including MBT′_(6me)(the methylation index for 6-methyl br GDGTs),CBT(Cyclisation index of Branched Tetraethers),IR_(IIa’)(Isomer ratio of IIa′)and IR_(IIIa′)(Isomer ratio of IIIa′)exhibited significant correlations with soil p H,suggesting these proxies can still be used for soil p H reconstruction in the coldhumid regions.The combination of MBT′_(5me)and MBT′_(6me)was strongly related to different types of climate(cold-dry,warmhumid,cold-humid,and warm-dry).For example,MBT′_(5me)0.65 and MBT′_(6me)0.55 are diagnostic for the cold-humid climate.Thus,the combination of MBT′_(5me)and MBT′_(6me)has the potential as a tool for the identification of different types of paleoclimate. 相似文献