Vortex-Induced Vibrations of A Long Flexible Cylinder in Linear and Exponential Shear Flows

A numerical study based on a wake oscillator model was conducted to determine the response performance of vortex-induced vibration(VIV) on a long flexible cylinder with pinned-pinned boundary conditions subjected to linear and exponential shear flows. The coupling equations of a structural vibration model and wake oscillator model were solved using a standard central finite difference method of the second order. The VIV response characteristics including the structural displacement, structural frequency, structural wavenumber, standing wave behavior,travelling wave behavior, structural velocity, lift force coefficient and transferred energy from the fluid to the structure with different flow profiles were compared. The numerical results show that the VIV displacement is a combination of standing waves and travelling waves. For linear shear flow, standing waves and travelling waves dominate the VIV response within the low-velocity and high-velocity zones, respectively. The negative values of the transferred energy only occur within the low-velocity zone. However, for exponential shear flow, travelling waves dominate the VIV response and the negative energy occurs along the entire length of the cylinder.     

大别-苏鲁造山带橄榄岩记录的碰撞造山过程中地幔楔的地壳交代作用

地壳交代作用是洋壳俯冲带板片-地幔界面的普遍现象,由于地幔楔样品的缺乏,其识别存在困难。而碰撞造山带广泛出露的地幔楔来源的造山带橄榄岩则是理想的研究对象。本文对大别-苏鲁造山带橄榄岩的已有研究成果进行了系统总结。这些成果表明这些橄榄岩在大洋俯冲向大陆碰撞转换的不同阶段经历了多期地壳来源流体的交代作用。地壳交代作用不仅改变了地幔楔橄榄岩的地球化学成分,而且导致了交代矿物的生长以及超镁铁质交代体的形成。这些交代体或作为同碰撞和碰撞后镁铁质火成岩的地幔源区,或将地壳组分传输到深部地幔,或释放流体交代大陆俯冲隧道中的俯冲陆壳。本文对地壳交代作用研究中存在的重要问题和解决思路提出了建议。     

牙鲆gnrh基因的表达分析

本文通过qPCR方法,研究了我国重要海水鱼类——牙鲆（Paralichthys olivaceus）雌、雄成体组织以及性腺分化期的脑、性腺中gnrh1、gnrh2和gnrh3的表达水平。结果显示,gnrh1分布于所有检测的组织：在脑、垂体、肾脏和肝脏中高表达,在性腺中表达相对较低;gnrh2则在雌、雄性的肝脏以及雄性的肠、肾脏、眼睛和头肾中;而gnrh3只在雄性的肾脏、眼睛和肌肉中检测到微弱表达。人工诱导的牙鲆雌核发育鱼苗分别用17β-雌二醇（E₂）和17α-甲基睾酮（MT）处理,使其分化为雌性或雄性个体表型。在性腺分化期的脑中,gnrh1的表达呈现上升趋势,在全长（total length,TL）4 cm鱼苗中,E₂组的表达显著高于MT组（P<0.05）;gnrh2在2 cm TL时E₂组显著高于MT组（P<0.05）,随后在E₂和对照组的表达水平均出现下降趋势;gnrh3在2 cm TL时E₂和对照组的表达均显著高于MT组（P<0.05）,自6 cm TL时MT和E₂组的表达开始下降。在性腺中,三种gnrh在性腺分化前2 cm TL表达量都相对较高,随后呈现下降趋势。综上,推测牙鲆gnrh1可能参与了性腺分化的启动、分化过程及性腺发育,gnrh2主要参与了性腺分化的启动,gnrh3主要参与了性腺分化的启动和分化过程。