Phenotypic plasticity in gut length in the planktivorous filter-feeding silver carp (Hypophthalmichthys molitrix)

Phenotypic plasticity widely exists in the external morphology of animals as well as the internal traits of organs. In the present study, we studied the gut length plasticity of planktivorous filter-feeding silver carp under different food resources in large-net cage experiments in Meiliang Bay of Lake Taihu in 2004 and 2005. There was a significant difference in stocking density between these 2 years. Under a low stocking density and abundant food resources, silver carp increased their energy intake by feeding on more zooplankton. Meanwhile, silver carp adjusted their gut length to match the digestive requirements of food when exposed to different food resources. In the main growth seasons (from April to October), silver carp significantly increased their relative gut length when feeding on more phytoplankton in 2005 (p < 0.01, 9.23 +/- 1.80 in 2004 and 10.77 +/- 2.05 in 2005, respectively). There was a nearly significant negative correlation between zooplankton proportion in the diet and the relative gut length when silver carp were stocked in a high density (p = 0.112). It appears that silver carp might have evolved plasticity to change their gut length rapidly to facilitate efficient utilization of food resources. Such resource polymorphisms in the gut may be a good indication of temporal adaptation to resource conditions. Our work provided field evidence for understanding the functional basis of resource polymorphisms and the evolution of phenotypic plasticity in planktivorous filter-feeding fish.

Interlayer segregation in magnetic multilayers and its influence on exchange coupling

Experimental results show that the exchange coupling field (H-ex) of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. X-ray photoelectron spectroscopy shows that Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. While studying Ta/X(X=Bi,Pb,Ag,In)/NiFe/FeMn multilayers, we also find that X atoms segregate to the NiFe/FeMn interface, which results in a decrease of the H-ex. However, a small amount of Bi, Pb, etc. deposited between Cu and pinned NiFe layer for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers can increase H-ex. (C) 2003 American Institute of Physics.

Interface energy and its influence on interface fracture between metal and ceramic thin films in nanoscale

A theoretical model about the size-dependent interface energy between two thin films with different materials is developed by considering the chemical bonding contribution based on the thermodynamic expressions and the structure strain contribution based on the mechanical characteristics. The interface energy decreases with reducing thickness of thin films, and is determined by such available thermodynamic and mechanical parameters as the melting entropy, the melting enthalpy, the shear modulus of two materials, etc. The predicted interface energies of some metal/MgO and metal/Al2O3 interfaces based on the model are consistent with the results based on the molecular mechanics calculation. Furthermore, the interface fracture properties of Ag/MgO and Ni/Al2O3 based on the atomistic simulation are further compared with each other. The fracture strength and the toughness of the interface with the smaller structure interface energy are both found to be lower. The intrinsic relations among the interface energy, the interface strength, and the fracture toughness are discussed by introducing the related interface potential and the interface stress. The microscopic interface fracture toughness is found to equal the structure interface energy in nanoscale, and the microscopic fracture strength is proportional to the fracture toughness. (C) 2010 American Institute of Physics. [doi:10.1063/1.3501090]

黄土高原土壤侵蚀与旱地农业国家重点实验室土壤侵蚀模拟实验大厅降雨装置

黄土高原土壤侵蚀与旱地农业国家重点实验室土壤侵蚀模拟实验大厅自 1 992年竣工以来运转正常 ,在降雨面积之大、降雨强度调节范围之宽、降雨特性与天然降雨之接近程度、以及自动化控制程度等方面 ,目前均为全国之最。在土壤侵蚀实验研究中发挥了重要作用。在论述土壤侵蚀模拟实验重要意义的基础上 ,简要介绍了有关模拟降雨装置 (包括降雨喷头、供水管网等 )的设计依据、选型和布设安装等情况 ,并介绍了模拟降雨的基本特征。

中国土壤侵蚀影响因素及其危害分析

该文从降雨、地貌、植被、土壤及人为因素等方面对中国土壤侵蚀的影响因素进行了系统分析 ,研究了土壤侵蚀使中国土地资源破坏、粮食减产、灾害发生、土壤肥力下降、水资源环境污染、库塘湖泊淤积、城市安全受到威胁等一系列危害 ,可供水土保持及环境整治决策作参考

基于面向对象的数控加工编程模拟仿真系统

数控编程技术对于数控机床的使用是非常重要的.对于其学习过程仅仅依靠书本及培训是远远不够的.一个人机界面友好、功能实用的模拟仿真系统无论是对于数控编程的学习还是对数控机床的使用都有重要意义.本文介绍了以面向对象的程序设计方法,针对FANUC6M系统,所完成的数控加工编程模拟仿真系统的开发技术.介绍了系统的体系结构、数据结构的设计及软件中的各个功能模块的作用及实现方法.

水库建设选址方案的决策分析

水库建设方案的评价,涉及投入和效益两方面。投入包括资金和工期等,称为“输入”:效益包括工农业用水增加、防洪能力强增等。称为“输出”。分析这种多输入,多输出的系统,应用数据包络分析方法是非常有效的。

基于DSRC的多功能不停车收费系统

DSRC标准是ISO/TC204制定的智能交通系统(ITS)中车—路信息通讯的协议。采用双片式ETC���子标签结合双界面IC卡的储值卡方案形成的多功能不停车收费系统,充分兼容了当前国内普遍应用的IC卡半自动收费方式,集中了IC卡收费系统和ETC���费系统的优点,方便、快捷、通行能力强,并解决了收费口的交通拥挤现象。