Improved spatial delineation of streambed properties and water fluxes using distributed temperature sensing          下载免费PDF全文

Landon J. S. Halloran  Hamid Roshan  Gabriel C. Rau  Martin S. Andersen  R. Ian Acworth 《水文研究》2016,30(15):2686-2702

A new method was developed for analysing and delineating streambed water fluxes, flow conditions and hydraulic properties using coiled fibre‐optic distributed temperature sensing or closely spaced discrete temperature sensors. This method allows for a thorough treatment of the spatial information embedded in temperature data by creating a matrix visualization of all possible sensor pairs. Application of the method to a 5‐day field dataset reveals the complexity of shallow streambed thermal regimes. To understand how velocity estimates are affected by violations of assumptions of one‐dimensional, saturated, homogeneous flow and to aid in the interpretation of field observations, the method was also applied to temperature data generated by numerical models of common field conditions: horizontal layering, presence of lateral flow and variable streambed saturation. The results show that each condition creates a distinct signature visible in the triangular matrices. The matrices are used to perform a comparison of the behaviour of one‐dimensional analytical heat‐tracing models. The results show that the amplitude ratio‐based method of velocity calculation leads to the most reliable estimates. The minimum sensor spacing required to obtain reliable velocity estimates with discrete sensors is also investigated using field data. The developed method will aid future heat‐tracing studies by providing a technique for visualizing and comparing results from fibre‐optic distributed temperature sensing installations and testing the robustness of analytical heat‐tracing models. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

A Long Way to Go: Collective Paths to Racial Justice in Geography     

Caroline Faria  Bisola Falola  Jane Henderson  Rebecca Maria Torres 《The Professional geographer》2019,71(2):364-376

Despite decades of recognition and worry about diversity, our discipline remains persistently white. That is, it is dominated by white bodies and it continues to conform to norms, practices, and ideologies of whiteness. This is a loss. At best, it limits the possibilities and impact of our work as geographers. At worst, it perpetuates harmful exclusions in our discipline: its working environments, its institutions, and its knowledge production. This remains deeply concerning for many geographers, and there has been important research, commentary, and institutional activity over the years. Yet, research shows us that little meaningful progress has been made. We know that mentoring is one vital part of the journey toward change. As such, we reflect here on our experience developing a research collective built on a transformative mentoring practice. We outline the key challenges, strategies, and tentative successes of the collective in supporting women of color undergraduate, graduate, and faculty geographers, arguing that such feminist formations are a vital part of the path to intellectual racial justice in our field. Key Words: diversity, feminist geography, higher education, mentoring, race.  相似文献   

浮游植物metacaspase的分布、结构及其功能特性     

苏金净  蔡伟聪  李桂玲  李健  曾珺  刘静雯 《海洋与湖沼》2019,50(5):1059-1069

精氨酸/赖氨酸特异性半胱氨酸蛋白酶(Metacaspase)在浮游植物程序性细胞死亡(programmed cell death.PCD)过程中起着关键作用。本文利用生物信息学方法分析metacaspase基因在浮游植物中的分布,并以海洋球石藻(Emilianiahuxleyi)metacaspases(EhMCs)为代表分析其结构和功能,依据Uniprot和String数据库挖掘与metacaspase功能相关并参与浮游植物PCD过程的互作蛋白。结果发现:共计29条、四种类型的metacaspases分布于11种浮游植物中,它们的metacaspase蛋白一级结构存在明显差异,但位于p20的组氨酸和半胱氨酸活性位点均具有高度的保守性;EhMCs三级结构与酵母的metacaspase十分相似,暗示它们具有类似的功能;浮游植物metacaspases与多种蛋白存在直接或间接的互作关系,在细胞PCD过程、响应环境胁迫和能量代谢等方面发挥重要作用。另外.metacaspase的磷酸化修饰可能在浮游植物PCD信号转导过程中起调节作用。  相似文献   

苯并（a）芘诱导下岩虫CYP基因的表达特征     

李婉娟  赵欢  Ba Fuyang  李绍娟  孙秀鹏  杨大佐  周一兵 《海洋学报(英文版)》2019,38(6):46-53

Rapid amplification of cDNA ends(RACE) and real-time polymerase chain reaction(RT-PCR) were carried out to analyze the CYP4 gene expression in polychaete Marphysa sanguinea exposed to benzo[a]pyrene(BaP) in this study. The full length of MsCYP4 cDNA was 2 470 bp, and it encoded 512 amino acids. The deduced amino acid sequence showed 47% identity with CYP4 F from frog Xenopus tropicalis and shared high homology with other known CYP4 sequences. To analyse the role of CYP4 in protecting M. sanguinea from BaP exposure, three BaP groups were established: 0.5, 5 and 50 μg/L. Polychaetes were sampled after 3, 7 and 12 d. At 0.5 μg/L, the effect of BaP on MsCYP4 gene expression increased with time prolonged. MsCYP4 gene expression curve showed Ushaped trend with time in 5 and 50 μg/L BaP groups. Therefore, MsCYP4 gene may play an important role in maintaining the balance of cellular metabolism and protecting M. sanguinea from BaP toxicity.  相似文献   

广西北部湾海域球形棕囊藻囊体时空分布及其影响因素     

贺成  宋书群  李才文 《海洋与湖沼》2019,50(3):630-643

为揭示广西北部湾海域球形棕囊藻囊体的时空分布特征,探讨其与水体环境因素的关系,于2016年12月至2017年6月对该海域29个站位进行了6次综合调查。结果表明,调查海域球形棕囊藻囊体丰度介于0—4.09×10~4col/m~3,12月至次年3月囊体丰度较高;西南深水区域囊体丰度呈现逐月递减趋势,而广西和雷州半岛近岸海域囊体丰度呈现先升高再降低的趋势。相关性分析显示该海域囊体丰度与水温、磷酸盐和硅酸盐浓度呈显著负相关(P0.01);与叶绿素a浓度、溶解氧呈显著正相关(P0.01);在局部区域与盐度呈显著正相关(P0.01),与硝酸盐浓度呈显著负相关(P0.01)。典型站位分析结果显示球形棕囊藻囊体丰度的变化趋势与其他浮游植物的相同,而与群落多样性指数的变化趋势相反。球形棕囊藻囊体的时空分布主要取决于环境条件的变化,也会受到其他浮游植物群落结构改变的影响。  相似文献   

A shift towards wetter and windier conditions in southern Sweden around the prominent solar minimum 2750 cal a BP          下载免费PDF全文

ANETTE MELLSTRÖM  NATHALIE VAN DER PUTTEN  RAIMUND MUSCHELER  RIXT DE JONG  SVANTE BJÖRCK 《第四纪科学杂志》2015,30(3):235-244

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全站仪三维坐标法在桥梁施工测量中的应用   总被引：1，自引：0，他引：1  

田林亚  王进锋  武东辉 《测绘科学》2010,35(3):198-199,202

尽管全站仪三维坐标法已在工程测量领域得到广泛采用,但其测量精度及其影响因素还需要深入分析,使之能合理地应用于具体工程。推导了三维坐标的精度计算公式,分析了测量精度的影响因素,针对特定的测量仪器、测量条件和大气折光误差,计算和分析了测点所能达到的精度,阐明了控制和提高测量精度的措施。将该方法应用于苏通大桥墩塔基础施工测量,根据具体的测量仪器和环境条件等,计算测点的点位中误差和高程中误差分别为±5.9mm和±6.9mm,其精度完全满足施工测量的限差要求,表明测量结果具有较高的精度和可信度。  相似文献   

Potential Influence of a Developing La Niña on the Sea-Ice Reduction in the Barents–Kara Seas     

Rui Luo  Peng Zhang  Juan Dou 《大气与海洋》2013,51(3):182-194

Abstract

The potential influence of a developing La Niña on Arctic sea-ice annual variability is investigated using both observational data and an atmospheric general circulation model. It is found that during the developing phase of an eastern Pacific (EP) La Niña event in June, July, and August (JJA) and September, October, and November (SON), the sea-ice concentration (SIC) over the Barents–Kara Seas declines more than 15%. The local atmospheric circulation pattern associated with the EP La Niña is characterized as a weak decrease in geopotential height over the Barents–Kara Seas, combined with an anticyclone in the North Atlantic. The corresponding southerly winds push warm waters northward into the key sea-ice reduction region and directly accelerate sea-ice melt. Meanwhile, the abundant moisture contained in the lower troposphere is transported into the Arctic region by winds resulting from the local barotropic structure. The humid atmosphere contributes to both net shortwave and longwave radiation and thus indirectly accelerates the decline in sea ice. Simulations by the European Centre Hamburg Model, version 5.4, are forced by observed sea surface temperature anomalies associated with EP La Niña events. The results of the simulations capture the North Atlantic anticyclone and reproduce the moisture transport, which supports the premise that an EP La Niña plays a crucial role in sea-ice reduction over the Barents–Kara sector from the perspective of atmospheric circulation and net surface heat flux.  相似文献   

Unconventional geometric phase gate and multiqubit entanglement for hot ions with a frequency-modulated field     

钟文学  程广玲  陈爱喜 《海洋学报(英文版)》2010,29(11)

We present an alternative scheme for implementing the unconventional geometric two-qubit phase gate and preparing multiqubit entanglement by using a frequency-modulated laser field to simultaneously illuminate all ions. Selecting the index of modulation yields selective mechanisms for coupling and decoupling between the internal and the external states of the ions. By the selective mechanisms, we obtain the unconventional geometric two-qubit phase gate, multiparticle Greenberger--Horne--Zeilinger states and highly entangled cluster states. Our scheme is insensitive to the thermal motion of the ions.  相似文献   

Seasonal variations of phytoplankton diversity in the Coleroon coastal waters, southeast coast of India   总被引：1，自引：0，他引：1  

Thillai Rajasekar K  Rajkumar M  SUN Jun  Ashok Prabu V  Perumal P 《海洋学报(英文版)》2010,29(5):97-108

The results of an investigation carried out during June 2005 to May 2007 on physico-chemical parameters,species composition and community structure of phytoplankton including Chlorophyll a(Chl-a) at the Coleroon coastal waters(Southeast coast of India) are reported.Air and surface water temperatures(°C) varied from 25.1 to 30.1 and from 24.5 to 28.5 respectively.Salinity values varied from 6 to 28.5 and the pH ranged between 7.0 and 8.3.Variation in dissolved oxygen content was from 3.1 to 7.5 mg/dm-3 while the light extinction coefficient values(LEC) ranged between 3.1 and 10.1 cm.The ranges of inorganic nutrients(μmol/dm-3) viz.,nitrate,nitrite,phosphate and silicate were 10.1-23.4,1.2-8.9,0.2-3.1 and 55-125,respectively.The ranges of Chlorophyll a(μg/dm-3) values was 2.0-7.5.Presently,124 phytoplankton species representing different classes viz:Bacillariophyceae(77),Dinophyceae(19),Cyanophyceae(15),Chlorophyceae(10) and Chrysophyceae(3) were recorded.The phytoplankton cell abundance varied from 0.290 to 111.662 cells/cm-3,with peak diversity(3.38 bits/ind.) during summer season.The maximum abundance was found during summer season coinciding with the stable hydrographical conditions.The seasonal distribution and abundance of phytoplankton are discussed in relation to hydrographical parameters.Canonical Correspondence Analysis(CCA) was applied in this paper for discriminating environmental factors having effect on phytoplankton community at species level.Coleroon coastal water is subjected to long term fluctuations in physico-chemical parameters depending upon the seasonal tidal amplitude and freshwater influx resulting in a continuous exchange of organic,inorganic,plant and animal matters.  相似文献