Digging with ‘hands’: observations of food capture in the flying gurnard Dactylopterus volitans (Linnaeus, 1758)

ABSTRACT

Videofilms of a foraging flying gurnard (Dactylopterus volitans) were collected at Itaipu, Niterói, RJ, Brazil. Analysis revealed details of the use of anterior parts of the pectoral fins which act as digging ‘hands’ to access infaunal prey items that are subsequently captured by oral suction feeding. Each pectoral fin has two distinct sections articulated separately on the pectoral girdle. The digging ‘anterior pectoral fin’ mainly consists of segmented and flexible fin rays but has an anterior robust unsegmented ray that provides an edge to the ‘hand’, allowing penetration of the substratum. The huge ‘posterior pectoral fins’ are supported by unsegmented rays. Most digging episodes involved one ‘hand’ and consisted of 1–7 cycles of movement with frequencies 1.15–3.74 cycles s^?1. During a cycle, the ‘hand’ is moved forwards and medially above the substratum, then is twisted medially and simultaneously depressed so that the anterior unsegmented ray impacts and enters the substratum. The hand is then drawn backwards and laterally to disturb the substratum. To prevent upward pitching of the head during digging, the ‘posterior pectoral fins’ are both moved anteriorly and laterally to shift the centre of gravity forwards while the caudal and ?second dorsal fins continue to provide propulsive force.     

大兴安岭中段哈达陶勒盖组火山岩U-Pb定年及成因

为了研究大兴安岭中段哈达陶勒盖组火山岩的形成时代和岩石成因,进行了锆石U-Pb同位素年龄测试和地球化学研究.LA-ICP-MS锆石U-Pb定年结果显示,哈达陶勒盖组火山岩形成于234~244Ma的中三叠世.岩石地球化学研究表明,哈达陶勒盖组火山岩具有低硅富碱、富钙镁的特征;稀土丰度总量w(∑RE)= 122.32×10^-6~140.66×10^-6,轻、重稀土分馏较明显,m(La)/m (Yb)_N=11.99~18.68, 无明显Eu负异常(δ_○Eu=0.84~0.98),微量元素以富集Rb,K,Ba,Th,亏损Nb,P,Ti为特征.哈达陶勒盖组火山岩岩浆源区为富集的岩石圈地幔, 并遭受了地壳物质的混染.     

水下航行器附连水质量的理论及实验研究

以二维无限长圆柱在水下的垂向振动为例,对其有限区域的不可压缩流场进行分析;通过数值计算并借鉴刘易斯法,分析了水域宽度比、水深比和浸没深度比等无量纲参数对刚体附连水质量的影响;提出了水下航行器附连水质量的快速预测公式.结果表明:刚性壁面可使刚体的附连水质量增大,但当刚体与壁面的距离增加到一定程度(截面半径的5倍)时,刚性壁面的影响可以忽略;自由表面可使刚体的附连水质量减小,当刚体与自由表面的距离达到截面半径的6倍时,可以忽略自由表面的影响;当刚体的垂向运动频率较高或刚体与自由表面的距离较大时,可以认为自由表面的速度势为零.     

论儿童英文原版绘本阅读

近年来，绘本阅读逐渐受到家长、学校和图书馆界的广泛重视。英文原版绘本以其视角多元、绘画优美、富于情趣而更受孩子们的喜欢。对于英文原版绘本阅读，要给予必要的引导，培养孩子们的阅读习惯。     

对仓显先生批评《有感》一文的回答--材料的再批判

针对仓显先生的辩护，对苏北提供的《处士施公廷佐墓志铭》、释满家的《施氏家簿谱》、杨新的《故处士施公墓志铭》、王道生的《施耐庵墓志》以及《兴化县续志》所载的《施耐庵传》进一步阐述本人的观点，加以再批判。     

密度均匀连续分层流体的内波格林函数

考虑自由表面的影响,从理论上建立了在密度均匀的连续分层流体中脉动点源生成内波的数理模型,应用Fourier变换和围道积分,推导出点源脉动频率的平方小于Brunt-Visl频率的平方条件下含自由面的连续分层流体中脉动点源的内波格林函数,并给出了详细的解析表达式,讨论了解的性质、内波的生成机理和自由面的干扰机理及波动特征.结果表明,所提出的连续分层流体中脉动点源的内波生成格林函数具有较好的准确性.     

“学生权利”与“学生权力”：论高校管理中的学生参与

大学生参与高校管理，既是其作为教育消费者与接受者的重要权利，又是其保障自身利益的合法权力。与西方国家相比，我国高校中的学生参与既存在学生主体地位被忽视、学生参与能力遭质疑和学生个体意识淡薄等理念性障碍，也存在行政管理机构中的边缘化、学生自治组织中的虚无化等制度性障碍。为更好地促进与提升高校管理中的学生参与，需要更新学生参与高校管理的观念、完善学生参与高校管理的机制和提升学生参与高校管理的品质。     

Curie’s principle and causal graphs

Curie’s Principle says that any symmetry property of a cause must be found in its effect. In this article, I consider Curie’s Principle from the point of view of graphical causal models, and demonstrate that, under one definition of a symmetry transformation, the causal modeling framework does not require anything like Curie’s Principle to be true. On another definition of a symmetry transformation, the graphical causal modeling formalism does imply a version of Curie’s Principle. These results yield a better understanding of the logical landscape with respect to the relationship between Curie’s Principle and graphical causal modeling.