Tunable surface-plasmon-resonance wavelength of silver island films     

王继飞  李宏建  周子游  李雪勇  刘菊  杨海艳 《海洋学报(英文版)》2010,29(11)

This paper experimentally and theoretically investigates the effect of the underlayer medium on tuning of the surface plasmon resonance (SPR) wavelength of silver island films, and the effect of substrate temperature on the morphologies and optical properties of the films. From the absorption spectra of single Ag with various thickness and overcoated (Ag/TiO₂) films deposited on glass substrates at various substrate temperatures by RF magnetron sputtering, we demonstrate that the surface plasmon resonance wavelength can be made tunable by changing the underlayer medium, the thickness of metal layer and the substrate temperature. By varying substrate temperatures, the interparticle coupling effects on plasmon resonances of nanosilver particles enhance as the spacing between the particles reduces. When the substrate temperature is up to 500 ℃, the absorption peak decreases sharply and shifts to shorter wavelength side due to the severe coalescence between silver islands in the film.  相似文献   

铜尾矿基质改良对旱柳生长的影响研究     

肖正辉  田胜尼  张静  李晓凤 《安徽地质》2014,(2):134-138

通过盆栽实验,研究了不同营养土改良的铜尾矿对旱柳(Salix matsudana)扦插枝条生长及根系特性的影响。处理方式分别为TA100(100%尾矿)、TA80(80%尾矿+20%营养土)、TA60(60%尾矿+40%营养土)、TA40(40%尾矿+60%营养土)、TA20(20%尾矿~80%营养土)、TA00(100%营养土)。研究结果发现,旱柳枝条在5种处理方式下均可生根成活,但长势存在差异。随着尾矿含量的降低,旱柳枝条的生物量呈现出增加的趋势;随着尾矿含量的降低,旱柳枝条不定根数目增多、平均根长及最长的根长增加,根系活力先增强后降低。结果表明,旱柳可用于铜尾矿废弃地植被恢复,利用营养土改良有利于柳条不定根的形成和生长。  相似文献   

基于Sentinel-2卫星影像的海南西岛珊瑚礁识别和变化分析          下载免费PDF全文

周雅君  何明郡  刘聪  贺双颜  姜庆岩  韩玉  陈栋  李培良 《海洋与湖沼》2024,55(1):65-76

珊瑚礁是海洋中最重要的生态系统之一, 近年来在全球气候变化和人为干扰加剧的影响下, 我国南海珊瑚礁总体处于快速退化状态。以海南西岛珊瑚礁为例, 基于Sentinel-2系列卫星10 m空间分辨率影像, 利用面向对象分类法(object-based image analysis, OBIA)对2017年12月~2018年3月和2021年12月两个时期的海南西岛珊瑚礁底质进行了识别分类, 并进行珊瑚礁面积变化分析。将2021年12月的分类结果与现场调查数据进行对比验证, 总分类精度和Kappa系数分别为83.3%和0.71。对比两个时期珊瑚礁底质分类结果表明, 西岛西侧珊瑚礁覆盖面积未出现明显变化, 东侧珊瑚礁显示恢复趋势。本文研究表明, 10 m地面分辨率卫星系列影像和面向对象的阈值分类方法可以对海南西岛珊瑚礁进行较为准确的识别和变化分析, 监测结果可为海南岛沿岸西岛等小型岛礁珊瑚保护及修复提供参考。  相似文献   

Kinematic wave solutions for pollutant transport by runoff over an impervious plane,with instantaneous or finite‐period mixing     

Vijay P. Singh 《水文研究》2002,16(9):1831-1863

Kinematic wave solutions are derived for transport of a conservative non‐point‐source pollutant during a rainfall‐runoff event over an impervious plane. Rainfall is assumed to be steady, uniform and finite in duration. Prior to the start of rainfall, the pollutant is distributed uniformly over the plane. When rainfall occurs, the pollutant is washed off in a particular manner and the mixing of pollutant in the runoff water occurs either instantaneously or in a finite period of time under the assumption that the pollutant is soluble and is mixed completely in the runoff water. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Resistance of salt marsh substrates to near-instantaneous hydrodynamic forcing     

Helen Brooks  Iris Möller  Simon Carr  Clementine Chirol  Elizabeth Christie  Ben Evans  Kate L. Spencer  Tom Spencer  Katherine Royse 《地球表面变化过程与地形》2021,46(1):67-88

Salt marshes deliver vital ecosystem services by providing habitats, storing pollutants and atmospheric carbon, and reducing flood and erosion risk in the coastal hinterland. Net losses in salt marsh areas, both modelled globally and measured regionally, are therefore of concern. Amongst other controls, the persistence of salt marshes in any one location depends on the ability of their substrates to resist hydrodynamic forcing at the marsh front, along creek margins and on the vegetated surface. Where relative sea level is rising, marsh elevation must keep pace with sea-level rise and landward expansion may be required to compensate for areal loss at exposed margins. This paper reviews current understanding of marsh substrate resistance to the near-instantaneous (seconds to hours) forcing induced by hydrodynamic processes. It outlines how variability in substrate properties may affect marsh substrate stability, explores current understanding of the interactions between substrate properties and erosion processes, and how the cumulative impact of these interactions may affect marsh stability over annual to decadal timescales. Whilst important advances have been made in understanding how specific soil properties affect near-instantaneous marsh substrate stability, less is known about how these properties interact and alter bulk substrate resistance to hydrodynamic forcing. Future research requires a more systematic approach to quantifying biological and sedimentological marsh substrate properties. These properties must then be linked to specific observable erosion processes, particularly at the marsh front and along creek banks. A better understanding of the intrinsic dynamics and processes acting on, and within, salt marsh substrates will facilitate improved prediction of marsh evolution under future hydrodynamic forcing scenarios. Notwithstanding the additional complications that arise from morphodynamic feedbacks, this would allow us to more accurately model the future potential protection from flooding and erosion afforded by marshes, while also increasing the effectiveness of salt marsh restoration and recreation schemes. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

A comparative study of intensive Litopenaeus vannamei culture on four bottom substrates without water change     

Hongwei Shan  Li Zhang  Lei Gao  Yuepeng Su  Weiyang Bao  Shen Ma 《中国海洋大学学报(英文版)》2014,13(4):705-711

The effect of four bottom substrates, oyster shell powder (OP), sugarcane bagasse (SB), a mixture of OP and SB (OS) and fresh soil (FS), on the water quality and bacterial and zooplankton density of intensive shrimp (Litopenaeus vannamei) culture tanks without water change and the growth performance of cultured shrimp were compared in this study. At the end of a 110 days culturing trial, the total ammonium-N (TAN) of the water on SB and the nitrite nitrogen (NO₂-N) on OS was significantly lower than that on the other substrates (P<0.05), which coincided with the high density of ammonium- and nitrite-oxidizing bacteria in the water on SB and OS, respectively. The concentration of chlorophyll a (Chl a) increased slowly on OP, SB and OS but remained low on FS. The density of total bacteria on OP, SB and OS was one order of magnitude higher than that on FS, and the density of zooplankton on SB and OS was significantly higher than that on FS or OP (P<0.05). The improved water quality and increased density of bacteria and zooplankton on SB and OS may have had a synergistic effect on shrimp culture, improving its growth performance (high survival rate and yield and low feed conversion rate). SB and OS were more effective for improving the growth performance of intensively cultured L. vannamei without water change than OP and FS. To our knowledge, this study presents the first evidence regarding the effect of different bottom substrates on intensive shrimp culture.  相似文献   

Rocky Substrate and the Lower Treeline Ecotone of Yellowstone's Northern Range     

《自然地理学》2013,34(4):356-373

Lower treeline ecotones are influenced by several processes, including fire, grazing, and climatic variables, but rocky substrate is an under-recognized factor affecting their patterns and dynamics. On the Northern Range of Yellowstone National Park, we hypothesized that north-facing slopes and riparian zones would explain the distribution of most forested areas, but that rocky substrate would explain a substantial additional portion of the lower treeline, and that advancement of conifers into grassland has occurred along rocky substrate. We used GIS software and change detection analysis to assess the spatial distribution and change of the forest with respect to north-facing slopes, riparian areas, and rocky substrate. As in other lower treeline studies, we found that north-facing slopes and riparian zones contained the majority of forested land (63%). However, areas with rocky substrate accounted for more forested area than north-facing slopes and riparian zones combined (67.4%), including 28% of forest that was not explained by the first two variables. Change detection analysis between 1954 and 2006 revealed that conifer advancement was insignificant but the number of forested patches increased and the mean size of patches decreased. These results suggest a more fragmented lower treeline environment that may indicate forest advancement in small patches. Field surveys revealed that rocky substrate did not provide conifers with protection from browsing ungulates or fire, yet conifers preferentially established on rocky areas. Our landscape analysis suggests that weathered rock increases soil coarseness in a landscape dominated by fine glacial till, which improves conditions for seedling establishment by reducing competition with grasses and shrubs sufficiently to overcome the negative influence of dry, nutrient-poor microsites in a moisture-stressed environment.  相似文献   

米槠天然林土壤真菌对N2O产生的贡献     

章伟  高人  陈仕东  马红亮  高艳  朱祥妹  尹云锋  杨玉盛  官惠玲 《亚热带资源与环境学报》2013,(2):28-34

研究表明亚热带地区森林土壤硝化和反硝化能力都非常低,但却是全球N2O最大的自然源之一,因而推测极有可能存在N2O潜在源未被认识,有迹象表明真菌最有可能是这一潜在源的贡献者,但实际研究证据并不多．为此本研究以中亚热带地区典型常绿阔叶林——武夷山自然保护区米槠天然林土壤为对象,利用室内基质诱导呼吸选择抑制方法,研究在水分60％WHC和温度25℃条件下土壤真菌细菌活性比及其对N2O产生的相对贡献．结果显示真菌和细菌的活性比例分别是0．7±0．3和0．3±0．1,前者显著大于后者（P〈0．05）,真菌与细菌的活性比为2．00±1．00;与对照相比,添加放线菌酮（真菌抑制剂）处理N2O产生速率减少了50．8±11．3％,添加链霉素（细菌抑制剂）处理则减少了43．7±11．8％,前者减少是后者的1．15倍,但差异不显著．研究结果表明该米槠天然林土壤在给定实验条件下真菌活性比细菌的大,但二者对土壤N2O产生的贡献几乎相等．基质诱导呼吸选择抑制方法具有较多的限制条件,若得出可靠结论,还应该利用包括生物化学、分子生物学方法在内的多种方法进行相互验证．同时今后应加强真菌产生N2O途径及机理研究．  相似文献   

The effect of abiotic environmental variables on the Danube macrozoobenthic communities     

Emília Elexov  Danka Nmethov 《Limnologica》2003,33(4):340-354

160 taxa of macrozoobenthos were recorded in the Danube River (R. km 1880-1704) riparian zone. Many typical Danubian and Pontocaspian representatives were found. The Slovak section of the Danube represents the border between its epipotamal and metapotamal stretches with different flow velocity and other environmental variables related to it. This paper characterises some abiotic ecological factors influencing the distribution of benthic taxa in five sampling sites along the longitudinal profile of the Danube. The benthic community composition was more strongly influenced by hydrological parameters than by oxygen and temperature regimes, as well as by the water quality conditions. In other words, the bottom substrate, flow velocity, water level fluctuation and discharge changes had the predominant effect on the taxocoenoses of macrozoobenthos. Three characteristic groups of macrozoobenthic organisms were recorded, as far as corresponding trophic guilds are concerned. Shredders and scrapers predominated in high flow velocity conditions with coarse substrate particles. Collectors of fine organic matter preferred slow-flowing conditions caused by damming or by a reduction of current due to the presence of bedrock. Filterers prevailed in the lower section of the Danube stretch monitored. Predators occurred independently of the environmental variables studied.  相似文献   

Eulerian-Lagrangian formulation of the equations for groundwater denitrification using bacterial activity     

S. Sorek  C. Braester 《Advances in water resources》1988,11(4)

A mathematical model for groundwater denitrification using bacterial activity is presented. The model includes the momentum and mass balance equations for water and nitrogen, substrate and bacteria, and chemical reactions between them. The resulting multiphase, multicomponent, flow and transport governing equations, are coupled and nonlinear. A Eulerian-Lagrangian formulation of the equations is developed. The water and gas flow and transport equations are split into forward advection along characteristics, and a residual at a fixed frame of reference. Discontinuities, sharp fronts and steep gradients of the dependent variables are imposed on the advection mode and solved exactly. It is believed that this novel method will avoid numerical artifacts for the solution of the multiphase flow equations (e.g., upstream permeability) and numerical dispersion for the transport equation.  相似文献