Metabolic loss of mass in glass eels at different salinities according to their propensity to migrate     

S. Bureau du Colombier  V. Bolliet  P. Lambert  A. Bardonnet 《Estuarine, Coastal and Shelf Science》2011

Eel facultative catadromy is not clearly understood. Initial work suggested a possible control by energy content and energy expense in young stages. The present work aimed to better understand the mechanisms involved, by studying the influence of the salinity rearing environment in the loss of mass and therefore on fish energy and migration. Glass eels (Anguilla anguilla L.) caught on the Atlantic coast were identified according to their rheotactic response to the dusk signal, and thus to their propensity to migrate which can be low (sedentary, M⁻ fish) or high (flow-wise catches in early night, M⁺ fish). M⁺ and M⁻ fish were individually placed at different salinities (0, 10 or 30) for 28 days in small containers equipped with shelters. Individual wet mass and pigmentary stage were determined on Day 1 and Day 28. In addition, dry mass and percent dry mass were measured on a sub-sample of 30 fish randomly chosen on Day 1, and on all fish on Day 28. There was no difference in the loss of mass linked to their adaptation to salinity between M⁻ and M⁺ fish, and so the results do not support the link between migratory behaviour and salinity tolérance (or to a larger extent osmoregulation). However, M⁻ fish lost more wet mass than M⁺ fish irrespective of the salinity, maybe because of a higher standard metabolism, which suggests that glass eels prone to loose more energy might choose to settle at sea or in estuary. In addition, the highest percent dry mass after 28 days in seawater associated to the highest loss of mass in 28 days in seawater does not support a higher energy cost of osmoregulation at sea.  相似文献   

The strength of biogenic sand reefs: Visco-elastic behaviour of cement secreted by the tube building polychaete Sabellaria alveolata, Linnaeus, 1767     

Jean-Benoît Le Cam  Jérôme Fournier  Samuel Etienne  Jérôme Couden 《Estuarine, Coastal and Shelf Science》2011

Mechanical properties of the biomineralised cement from tube-building marine worms are poorly known. Secreted from an organ connected to the polychaetes specialised glands, the cement glues sand grains and calcareous shell fragments of a given size and, on a larger scale, ensures the resistance of the reef to waves. In this study, three kinds of mechanical tests were performed with worm tubes to establish the nature of the cement behaviour. Results obtained show that cement behaves like a visco-elastic material. This property allows the tubes to dissipate the mechanical energy from the waves to which they are subject and to reduce the mechanical stress transmitted inside the tubes to the polychaetes. Comparison of “fresh” and “dry” cements highlights that the visco-elastic behaviour of the cement is maintained after five years. The viscosity of the cement is therefore not related to moisture but to its chemical composition. More generally, these results offer a better understanding of the role of cement on worm reefs strength and their persistence in the geological record.  相似文献   

Estimating Synaphobranchus kaupii densities: Contribution of fish behaviour to differences between bait experiments and visual strip transects     

Verena M. Trenkel  Pascal Lorance 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):63-71

Kaup's arrowtooth eel Synaphobranchus kaupii is a small-bodied fish and an abundant inhabitant of the European continental slope. To estimate its local density video information using the remotely operated vehicle (ROV) Victor 6000 were collected at three locations in the Bay of Biscay slope. Two methods for estimating local densities were tested: strip transect counts and bait experiments. For bait experiments three behaviour types were observed in about equal proportions for individuals arriving near the seafloor: moving up the current towards the ROV, moving across the current and drifting with the current. Visible attraction towards the bait was the highest for individuals swimming against the current (80%) and about equally low for the other two types (around 30%); it did not depend on current speed nor temperature. Three main innovations were introduced for estimating population densities from bait experiments: (i) inclusion of an additional behaviour category—that of passively drifting individuals, (ii) inclusion of reaction behaviour for actively swimming individuals and (iii) a hierarchical Bayesian estimation framework. The results indicated that about half of individuals were foraging actively of which less than one third reacted on encountering the bait plume and the other half were drifting with the current. Taking account of drifting individuals and the reaction probability made density estimates from bait experiments and strip transects more similar.  相似文献   

Formulation of a 3-D numerical model of brittle behaviour   总被引：1，自引：0，他引：1  

Frédéric Donzé  Sophie-Adélaide Magnier 《Geophysical Journal International》1995,122(3):790-802

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Deformation of rock: A pressure-sensitive,dilatant material   总被引：5，自引：0，他引：5  

A. Ord 《Pure and Applied Geophysics》1991,137(4):337-366

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冻土的单轴压缩本构关系   总被引：21，自引：9，他引：21  

朱元林  张家懿 《冰川冻土》1992,14(3):210-217

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地形对中期天气过程的动力和热力作用的初步探讨     

黄伯银  吴万里 《高原气象》1992,11(2):161-169

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内蒙古乌奴格吐山铜—钼矿床稀土元素的行为及意义   总被引：10，自引：0，他引：10       下载免费PDF全文

秦克章  王之田 《地质学报》1993,67(4):323-335

以热液作用为联结点，将斑岩和围岩作为一个整体系统来考虑，对乌奴格吐山特大型斑岩铜－钼矿床热液蚀变矿化过程中ＲＥＥ行为进行了研究，首次发现热液蚀变过程中母岩与围岩ＲＥＥ变化具互补性，铕亏损对斑岩矿化具指示意义。分析ＲＥＥ的赋存矿物及其在蚀变过程中的变化，推断成矿流体具有贫ＲＥＥ，相对富ΣＹ，强烈亏损铕的性质在中强蚀变带斑岩和围岩基本上是以等比质量参与热液蚀变交代的。稀土元素，液体包裹体和氢，氧同位素  相似文献   

轨道站点合理步行可达范围建成环境与轨道通勤的关系研究——以北京市44个轨道站点为例   总被引：4，自引：1，他引：3  

申犁帆  王烨  张纯  姜冬睿  李赫 《地理学报》2018,73(12):2423-2439

轨道站点步行可达范围内建成环境因素与轨道交通通勤行为之间的关系越来越受到人们的重视。从潜在通勤者的角度出发,划定轨道站点的合理步行可达范围,以北京市44个轨道站点为例,利用大数据方法从“宜出行”程序中提取站点合理步行范围内的相对人口数据,结合2017年9月10个工作日早高峰时段的轨道站点刷卡数据得到该站点的相对乘车率。基于数据的非正态分布特征构建GARCH模型,分析早高峰站点合理步行范围内建成环境因素与站点相对乘车率的关系。结果表明：① 始发轨道站点与站点乘车率存在显著正向关系,而站点所在线路的换乘概率与站点乘车率具有非常明显的负相关性;② 轨道站点的出入口数量与乘车率显著正相关;③ 小区—站点的路径转折数和步行范围内的交叉路口数等可步行性特征对轨道交通通勤行为无显著影响,步行范围的公交车站密度与站点乘车率正相关;④ 合理步行范围内的用地混合度与乘车率存在显著的负相关性;⑤ 合理步行范围内的路网密度以及早高峰拥堵道路比与乘车率之间在不同程度上呈现正向关系;⑥ 共享单车订单数与轨道交通通勤行为之间的关系并不明确;⑦ 相比手机信令数据,“宜出行”定位数据的精度更高,适用于分析微观尺度下的实时人口分布及变化。  相似文献   

Assessing the EU ETS with a bottom-up,multi-sector model     

Pablo Pintos  Pedro Linares 《Climate Policy》2018,18(4):413-424

The European Emissions Trading System (EU ETS) is the central pillar of the EU response against climate change. This trading mechanism is considered, from the theoretical point of view, as the most cost-effective method to reduce GHG. However, previous studies show that the agents who participate in these markets may behave in a way that may lead to inefficient CO₂ prices, creating doubts about the static and dynamic efficiency of the system. This article analyses these possible anomalies by first trying to model the ETS in a more realistic way, addressing some of the limitations of previous models, and second, by comparing the results with real market transactions. For this, a bottom-up, multi-sector model has been built, which represents the EU ETS in an integrated, cross-sectoral way, paying particular attention to the interactions among the most emissions intensive industries. The results show the benefits of this modelling approach and how it better reflects real market conditions. Some preliminary conclusions regarding the behaviour of the agents in the ETS market are also presented.

POLICY RELEVANCE

Low allowance prices in the EU ETS have put into question the dynamic efficiency of the EU ETS system, prompting various ideas for structural reform. However, determining the right reform also requires estimating correctly how agents will respond to it. This article proposes a tool to realistically simulate the EU ETS under the assumption of rational agents, and compare it to real market outcomes, in order to understand better the behaviour of agents in this carbon market, and therefore how to design better policies.  相似文献