大菱鲆体重和主要体型比率性状的遗传动态分析     

王新安  马爱军 《海洋学报(英文版)》2020,39(2):22-27

The objective of this study was to estimate genetic parameters of body width(BW)to body length(BL)ratio(BW/BL)and of body weight traits(BWT)in turbot,and to elucidate the genetic mechanism of the two traits during ontogeny by dynamic genetic analysis.From 3 to 27 months,BW,BL and BWT of each communally stocked fish were measured every 3 months.The BW/BL ratio was measured at different sampling ages.A twotrait animal model was used for genetic evaluation of traits.The results showed that the heritability values of BW/BL ratio ranged from 0.2168 to 0.3148,corresponding to moderate heritability.The BWT heritability values ranged from 0.2702 to 0.3479 corresponding to moderate heritability.The heritability of BW/BL ratio was lower than that of BWT,except at 3 months of age.Genetic correlation between BW/BL ratio and BWT decreased throughout the measurement period.Genetic correlations were higher than the phenotypic correlations.The current results for estimating genetic parameters demonstrate that the BW/BL ratio could be used as a phenotypic marker of fast-growing turbot,and the BW/BL ratio and BWT could be improved simultaneously through selective breeding.  相似文献   

Discrete element method modeling of inherently anisotropic rocks under uniaxial compression loading          下载免费PDF全文

K. Duan  C.Y. Kwok  M. Pierce 《国际地质力学数值与分析法杂志》2016,40(8):1150-1183

A new numerical approach is proposed in this study to model the mechanical behaviors of inherently anisotropic rocks in which the rock matrix is represented as bonded particle model, and the intrinsic anisotropy is imposed by replacing any parallel bonds dipping within a certain angle range with smooth‐joint contacts. A series of numerical models with β = 0°, 15°, 30°, 45°, 60°, 75°, and 90° are constructed and tested (β is defined as the angle between the normal of weak layers and the maximum principal stress direction). The effect of smooth‐joint parameters on the uniaxial compression strength and Young's modulus is investigated systematically. The simulation results reveal that the normal strength of smooth‐joint mainly affects the behaviors at high anisotropy angles (β > 45°), while the shear strength plays an important role at medium anisotropy angles (30°–75°). The normal stiffness controls the mechanical behaviors at low anisotropy angles. The angle range of parallel bonds being replaced plays an important role on defining the degree of anisotropy. Step‐by‐step procedures for the calibration of micro parameters are recommended. The numerical model is calibrated to reproduce the behaviors of different anisotropic rocks. Detailed analyses are conducted to investigate the brittle failure process by looking at stress‐strain behaviors, increment of micro cracks, initiation and propagation of fractures. Most of these responses agree well with previous experimental findings and can provide new insights into the micro mechanisms related to the anisotropic deformation and failure behaviors. The numerical approach is then applied to simulate the stress‐induced borehole breakouts in anisotropic rock formations at reduced scale. The effect of rock anisotropy and stress anisotropy can be captured. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2000-2015年三江平原主要作物需水量征及影响因素分析          下载免费PDF全文

任修琳  李宏亮  张玉虎  蒲晓  张立林 《干旱区地理》2019,42(4):854-866

全生育期内作物需水量的研究是农业水资源有效利用和进行合理灌溉的重要依据。基于三江平原22个气象站点2000—2015年逐日气象观测资料及中国区域地面气象要素数据集，利用国际粮农组织 （FAO）Penman-Monteith模型和分段单值平均作物系数法，分别对三江平原水稻、玉米和大豆的作物需水量进行计算，分析作物需水量年际变化特征，采用通径分析法研究作物需水量的变化成因。结果表明：（1）三江平原16 a来年均参考作物蒸散量为537.4 mm，日均为 3.5 mm，呈波动减少趋势。（2）生长季内，水稻在分蘖期需水量最大，为177.1 mm，玉米在七叶期需水量最大，为99.7 mm，大豆在结荚期需水量最大，为96.1 mm；水稻、玉米和大豆的净灌溉需水量分别为195.4 mm、130.8 mm和72.2 mm，对灌溉的依赖程度水稻>玉米>大豆。（3）由通径分析结果可知，三江平原作物需水量的主要影响因素为净辐射、气温和日照时数。  相似文献   

The use of the exponent K(q) function to delimit homogeneous regions in regional frequency analysis of extreme annual daily rainfall          下载免费PDF全文

A. P. García‐Marín  J. Estévez  C. Sangüesa‐Pool  R. Pizarro‐Tapia  J. L. Ayuso‐Muñoz  F. J. Jimenez‐Hornero 《水文研究》2015,29(1):139-151

The regional frequency analysis of extreme annual rainfall data is a useful methodology in hydrology to obtain certain quantile values when no long data series are available. The most crucial step in the analysis is the grouping of sites into homogeneous regions. This work presents a new grouping criterion based on some multifractal properties of rainfall data. For this purpose, a regional frequency analysis of extreme annual rainfall data from the Maule Region (Chile) has been performed. Daily rainfall data series of 53 available stations have been studied, and their empirical moments scaling exponent functions K(q) have been obtained. Two characteristics parameters of the K(q) functions (γ_max and K(0)) have been used to group the stations into three homogeneous regions. Only five sites have not been possible to include into any homogenous regions, being the local frequency analysis of extreme daily rainfall the most appropriate method to be used at these locations. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Validating the ability of the discontinuous deformation analysis method to model normal P‐wave propagation across rock fractures          下载免费PDF全文

Wenjun Gong  Yunsheng Wang  Youjun Ning  Yonghong Luo  Yujie Wang 《国际地质力学数值与分析法杂志》2017,41(10):1267-1282

The effects of fractures on wave propagation problems are increasingly abstracting the attention of scholars and engineers in rock engineering field. This study aims to fully validate the ability of discontinuous deformation analysis (DDA) to model normal P‐wave propagation across rock fractures. The effects of a single fracture and multiple parallel fractures are all tested. The results indicate that DDA can accurately reflect the fracture effects, including the fractures stiffness, the fracture spacing and the fracture number, and the effects of incident wave frequency on one‐dimensional P‐wave propagation problems. Thus, DDA is able to deal well with normal incident P‐wave propagation problems. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Characterizing and classifying urban watersheds with compositional and structural attributes     

Joseph M. Delesantro  Jonathan M. Duncan  Diego Riveros-Iregui  Joanna R. Blaszczak  Emily S. Bernhardt  Dean L. Urban  Lawrence E. Band 《水文研究》2021,35(9):e14339

Current land-use classifications used to assess urbanization effects on stream water quality date back to the 1980s when limited information was available to characterize watershed attributes that mediate non-point source pollution. With high resolution remote sensing and widely used GIS tools, there has been a vast increase in the availability and precision of geospatial data of built environments. In this study, we leverage geospatial data to expand the characterization of developed landscapes and create a typology that allows us to better understand the impact of complex developed landscapes across the rural to urban gradient. We assess the ability of the developed landscape typology to reveal patterns in stream water chemistry previously undetected by traditional land-cover based classification. We examine the distribution of land-cover, infrastructure, topography and geology across 3876 National Hydrography Dataset Plus catchments in the Piedmont region of North Carolina, USA. From this dataset, we generate metrics to evaluate the abundance, density and position of landscape features relative to streams, catchment outlets and topographic wetness metrics. While impervious surfaces are a key distinguishing feature of the urban landscape, sanitary infrastructure, population density and geology are better predictors of baseflow stream water chemistry. Unsupervised clustering was used to generate a distinct developed landscape typology based on the expanded, high-resolution landscape feature information. Using stream chemistry data from 37 developed headwater catchments, we compared the baseflow water chemistry grouped by traditional land-cover based classes of urbanization (rural, low, medium and high density) to our composition and structure-based classification (a nine-class typology). The typology based on 22 metrics of developed landscape composition and structure explained over 50% of the variation in NO₃⁻-N, TDN, DOC, Cl⁻, and Br⁻ concentration, while the ISC-based classification only significantly explained 23% of the variation in TDN. These results demonstrate the importance of infrastructure, population and geology in defining developed landscapes and improving discrete classes for water management.  相似文献   

Spatiotemporal estimation of snow depth using point data from snow stakes,digital terrain models,and satellite data          下载免费PDF全文

Antonio‐Juan Collados‐Lara  Eulogio Pardo‐Igúzquiza  David Pulido‐Velazquez 《水文研究》2017,31(10):1966-1982

Snow availability in Alpine catchments plays an important role in water resources management. In this paper, we propose a method for an optimal estimation of snow depth (areal extension and thickness) in Alpine systems from point data and satellite observations by using significant explanatory variables deduced from a digital terrain model. It is intended to be a parsimonious approach that may complement physical‐based methodologies. Different techniques (multiple regression, multicriteria analysis, and kriging) are integrated to address the following issues: We identify the explanatory variables that could be helpful on the basis of a critical review of the scientific literature. We study the relationship between ground observations and explanatory variables using a systematic procedure for a complete multiple regression analysis. Multiple regression models are calibrated combining all suggested model structures and explanatory variables. We also propose an evaluation of the models (using indices to analyze the goodness of fit) and select the best approaches (models and variables) on the basis of multicriteria analysis. Estimation of the snow depth is performed with the selected regression models. The residual estimation is improved by applying kriging in cases with spatial correlation. The final estimate is obtained by combining regression and kriging results, and constraining the snow domain in accordance with satellite data. The method is illustrated using the case study of the Sierra Nevada mountain range (Southern Spain). A cross‐validation experiment has confirmed the efficiency of the proposed procedure. Finally, although it is not the scope of this work, the snow depth is used to asses a first estimation of snow water equivalent resources.  相似文献   

Isolation, distribution and evaluation of cytotoxic and antioxidant activity of cultivable actinobacteria from the Oman Sea sediments     

Gozari Mohsen  Bahador Nim  Jassbi Amir Rez  Mortazavi Mohammad Seddiq  Hamzehei Sam  Eftekhar Ebrahim 《海洋学报(英文版)》2019,38(12):84-90

Screening bioactive natural products from bacteria is a determinative step in the drug discovery programs. The present study aim to isolate actinobacteria from the Oman Sea sediments for determining the effects of different culture media and treatments on the yield of the isolation process, and measure the DPPH radical scavenging and Artemia cytotoxic activity of culture extracts of the actinobacterial isolates. A total of 290 actinobacterial isolates were collected from 14 sediment samples. Heat treatment(40.68%) and M_4 medium(29.31%) exhibited the maximum isolation rates of actinobacteria. Streptomyces isolates were dominantly distributed in all of the investigated stations according to 16 S rRNA gene sequencing. The distribution pattern of Streptomyces followed a depth-dependent frequency trend, whereas the members of rare genera including Micromonospora, Nocardia Actinoplanes, Nocardiopsis, Saccharopolyspora and Crossiella were distributed in deeper stations. Approximately,25% of the examined isolates could scavenge 90% of 10~(–4) mol/L DPPH solutions at 1 250 μg/mL final concentration of their ethyl acetate culture extracts. Furthermore, the most potent extracts could scavenge DPPH radicals with IC50 ranges from 356.8 to 566.4 μg/mL. Brine shrimp cytotoxicity tests showed that 38.88% of the examined culture extracts exhibited LC_(50) lower than 1 000 μg/mL against the Artemia cells. Moreover, the most potent culture extracts exhibited LC_(50) range from 335.4 to 534.4 μg/mL. Phylogenetic analysis by 16 S rRNA gene sequence revealed that the OS 005, OS 263 and OS 157 closely related to Streptomyces djakartensis, Streptomyces olivaceus and Nocardiopsis dassonvillei respectively. These results suggested the widespread distribution of the antioxidant and cytotoxic producing actinobacteria in the Oman Sea sediments, which could be considered as promising candidates for the discovery of microbial bioactive compounds.  相似文献   

2000-2015年柴达木盆地植被覆盖度时空变化及其与环境因子的关系          下载免费PDF全文

张斯琦  陈辉  宋明华  付阳  牛慧慧  杨祎  张博雄 《干旱区地理》2019,42(5):1124-1132

基于MODIS-NDVI、DEM和气象数据，分析柴达木盆地2000—2015年植被覆盖度（FVC）时空变化特征，并与降水、温度、日照时数、相对湿度、蒸散量和海拔进行相关、偏相关或叠加分析，探讨FVC与各环境因子的关系。结果表明：FVC整体自东南向西北内陆呈半环状递减，FVC集中在20%以下，人类活动及径流等打破植被地带性规律；2000—2015年FVC明显改善，广泛分布于盆地中西部地区，2001—2002年年际变化最显著；FVC与降水、相对湿度以正相关为主，与温度关系不显著，与日照时数和蒸散量主要为负相关，降水对FVC贡献最大，温度通过影响蒸散量等间接影响FVC，而土壤蒸发对蒸散量的影响大于植物蒸腾；FVC与等高线空间分布较吻合，FVC在2 800~2 900 m和4 600~4 700 m出现两个峰值，4 700 m以上FVC迅速降低。  相似文献   

文学地理学视野下香港文化认同     

张铃钰  叶浩威  安宁 《热带地理》2019,39(6):880-888

通过文本分析和档案分析的方法,立足文学地理学分析框架和研究范式,分析了香港70年代、过渡时期、后殖民时期三部文学界热门且公认具代表性的作品——《我城》《烦恼娃娃的旅程》和《后殖民食物与爱情》,解构了作品中“本土”“国家”和“全球”3个空间维度下再现的地理物象、空间想象、人物活动、地方文化,窥探其内部隐含的文化认同与身份意识问题。结果发现,由于香港社会历史和文化背景不断变迁等原因,香港的文化和身份意识处于不断重塑的状态。通过文本分析,发现香港文学作品中最早萌芽的是“本土”意识。西西的《我城》被认为是本土意识的发轫之作,其在港英政府和回不去的家这一夹缝中在“城”这一空间尺度上勾勒出浓浓的地方意识。其次,在中国恢复行使香港主权这一背景下,《烦恼娃娃的旅程》这一极具回归题材代表性的作品深刻地刻画了香港人在身份认同尺度升级过程中的迷惘。最后,也斯的《后殖民食物与爱情》通过“食物”为线索讲述了回归后的香港故事,为读者认识后殖民时期多元文化混杂下的香港社会提供了细致的观察。通过对三部文学作品的分析,发现港人经历了由殖民统治时期本土身份意识的觉醒以及对中国文化的归属,到回归过渡阶段身份意识的尺度升级及其不适,再到回归后多元文化的交织和协商,不仅在尺度上实现了由地方到国家再到全球化的身份意识塑造,而且在结构上存在中华文化、西方文化和香港本土文化不断协商与冲突的三重性。更为重要的是,通过文学地理视角的讨论,发现这样的文化和身份意识不是属于某个群体的特有特征,而是根植于香港社会的每一寸肌肤,不仅反映了小说作者对香港社会的细致观察,在一定程度上也反映了社会本身所面临的文化和身份困扰。  相似文献