Growth and shape control of disks by bending and extension

Differential growth of thin elastic bodies furnishes a surprisingly simple explanation of the complex and intriguing shapes of many biological systems, such as plant leaves and organs. Similarly, inelastic strains induced by thermal effects or active materials in layered plates are extensively used to control the curvature of thin engineering structures. Such behaviour inspires us to distinguish and to compare two possible modes of differential growth not normally compared to each other, in order to reveal the full range of out-of-plane shapes of an initially flat disk. The first growth mode, frequently employed by engineers, is characterised by direct bending strains through the thickness, and the second mode, mainly apparent in biological systems, is driven by extensional strains of the middle surface. When each mode is considered separately, it is shown that buckling is common to both modes, leading to bistable shapes: growth from bending strains results in a double-curvature limit at buckling, followed by almost developable deformation in which the Gaussian curvature at buckling is conserved; during extensional growth, out-of-plane distortions occur only when the buckling condition is reached, and the Gaussian curvature continues to increase. When both growth modes are present, it is shown that, generally, larger displacements are obtained under in-plane growth when the disk is relatively thick and growth strains are small, and vice versa. It is also shown that shapes can be mono-, bi-, tri- or neutrally stable, depending on the growth strain levels and the material properties: furthermore, it is shown that certain combinations of growth modes result in a free, or natural, response in which the doubly curved shape of disk exactly matches the imposed strains. Such diverse behaviour, in general, may help to realise more effective actuation schemes for engineering structures. © 2012 Elsevier Ltd. All rights reserved.

收割对穗花狐尾藻生长的影响

在水深为24cm的桶中,以6、12和18cm等3个收割强度对穗花狐尾藻(Myrio-phyllum spicatum)进行了连续4次收割实验,研究了收割强度、收割频次及收割季节对穗花狐尾藻生长恢复的影响。结果表明:8月下旬第1次收割18cm后,植物在41d恢复,但产生分枝较少,影响了植物的无性繁殖;9月下旬之前,前2次收割6cm或12cm后,穗花狐尾藻在55d恢复,并能产生较多的分枝,而且条枝总长有明显的增加,表明穗花狐尾藻的无性繁殖没有受到抑制;10月初第2次收割18cm,或11月下旬前第3次收割6或1

黄鳝摄食活饵的初步研究

本文对不同体重的黄鳝摄食蚯蚓、蝌蚪、蛴螬的饵料系数、特定生长率、能量转化效率和最大摄食量等作了初步研究。结果表明 :在限食试验中 ,黄鳝摄食蚯蚓、蝌蚪、蛴螬的饵料系数分别为 3.2 83.89、7.0 99.0 7、3.393.4 2 ;特定生长率分别为 0 .33% 1.0 9%、1.0 9% 1.2 0 %、0 .6 5 % 0 .70 % ;能量转化效率分别为2 4 .9% 2 9.5 %、33.2 % 34.1%、2 8.8% 2 9.1%。饵料系数、特定生长率的大小主要决定于饵料性质 ,与体重(

单克隆抗体技术在水生动物病毒研究中的应用

“淡水生态与生物技术”国家重点实验室开放课题(2002FB07); 国家自然科学基金(30170726); 中国科学院及中国科学院水生生物研究所创新项目(KSCX2-SW-302与220313)

湖北省楔桥弯藻属新种类(英文)

楔桥弯藻属 (Gomphocymbella)是由M櫣ｌｌｅｒ在 190 5年建立的 ,它兼有桥弯藻属和异极藻属的双重特性。虽然对它的系统发育及分类问题仍在讨论之中 ,但一般把它归于异极藻科中。它较为罕见 ,至今报道的种类仅有 10个左右。在我国至今只报道有一个种。近几年来 ,著者对湖北省硅藻类中的异极藻科 (Gomphomenaceae)进行了分类学研究 ,发现有 3个楔桥弯藻属的种类 ,其中 2个为新种类 :疏纹楔桥弯藻 (GomphocymbellalaxistriaShietN .Li)和不对称楔桥

A preliminary study of target multiplicity for ADSRs

The Accelerator Driven Subcritical Reactor (ADSR) concept is based on the coupling of a particle accelerator to a subcritical reactor core by means of a neutron spallation target interface. This paper investigates the benefits of multiple spallation targets in ADSRs. The motivation behind this is, firstly, to improve the overall reliability of the accelerator-reactor system, and, secondly, to evaluate other potential advantages such as lower beam power requirements. The results show that a system containing two or three spallation targets, coupled to independent accelerators, offers better neutronic performance. This is demonstrated through the increased effective multiplication factor (keff) in the two- and three-target configurations and a more uniform neutron flux distribution. A multiple-target ADSR also proves effective in mitigating the impact of frequent beam interruptions, a pressing issue that needs to be addressed for the ADSR concept to advance. Assuming no simultaneous beam shutdowns, the two- and three-target configurations reduce the risk of fuel cladding failure due to thermal cyclic fatigue. © 2013 Elsevier B.V. All rights reserved.

微卫星DNA遗传分析在原生动物学中的研究进展

国家自然科学基金资助项目 ( 39730 0 70 ); 中国科学院创新基金资助项目 ( 2 2 0 2 0 7)资助

中国缓步动物门二新种及三新纪录种和亚种(异缓步纲,棘影熊虫科;真缓步纲,小斑熊虫科,大生熊虫科,高生熊虫科)

记述采自河南省洛阳市、湖北省京山县和四川省都江堰市的缓步动物门 2新种及 3新纪录种和亚种 :异缓步纲棘影熊虫科的四棘棘影熊虫 ,新纪录EchiniscusquadrispinosusRichters,190 2 ;真缓步纲小斑熊虫科的都江小斑熊虫 ,新种Milnesiumdujiangensissp .nov .,大生熊虫科的节值大生熊虫戴冠亚种 ,新纪录MacrobiotusharmsworthicoronatusBarros,1942 ;高生熊虫科的大指等高熊虫 ,新纪录Isohypsibiusma

水生大型无脊椎动物的能量密度

测定了 72种大型水生无脊椎动物的能量密度 ,其中 6 9种是第一次测定 .底栖动物的能量密度随物种、季节、地区、年龄等的不同而存在差异 .绝大多数寡毛类的能量密度为 2 2 .99- 2 5 .0 8kJ/g(干重 ) ,软体动物的能量密度为 16 .72 - 2 2 .99kJ/g(干重 ) ,昆虫及其幼虫的能量密度变异较大 ,为 10 .4 5 - 2 5 .0 8kJ/g(干重 )左右 .

银鲫能量收支同步测定方法

国家自然科学基金96-008-02-03

维生素C在水产养殖业的应用

<正> 维生素C,又称丙种维生素,VitaminumC,抗坏血酸(Ascorbic acid),简称维C或Vc。维生素C是一种酸性己糖衍生物。化学名称为L—3—氧带苏己糖醛酸内酯。分子式为C_6H_8O_6,分子量为176.1。1维生素C的性状 外观为白色结晶粉末,有酸味,久置色渐变微黄色,易溶于水,水溶液呈酸性反应。稍溶于乙醇,微溶于甘油,不溶于乙醚和氯仿。熔点为190℃。抗坏血酸钠为白色或微黄色结晶粉末,略带酸味,只溶于水,基本上不溶于乙醇、乙醚等。在220℃时分解。 维生素C是动物的重要营养成分之一

湖北省异极藻属的新种类

国家自然科学基金39899400

蓝藻Anabaena sp.PCC7120 羧体碳酸酐酶的鉴定

在丝状蓝藻Anabaena sp.PCC7120细胞粗提液的碳酸酐酶(CA)分析中,发现了两种形式的CA活性.高CO_2下生长的细胞,在35μmol/L EZ(Ethoxyzolamide,碳酸酐酶的抑制剂)存在的情况下,CA总活性的85％左右被抑制,其半抑制浓度I_(50)为7.4μmol/L;随着EZ浓度的继续增加,CA活性在EZ浓度达到约150μmol/L处出现了第二个抑制峰,在250μmol/L处抑制程度达到最大,使CA总活性的15％被抑制,其半抑制浓度I_(50)为190μmol/L。在空气条件