三疣梭子蟹几丁质酶基因(PtCht6)的克隆及其在免疫中的功能分析     

宋柳  吕建建  王磊  孙东方  刘萍 《海洋与湖沼》2019,50(5):1080-1090

几丁质酶(chitinase)在甲壳动物的蜕皮、消化和免疫等很多生物学过程中发挥重要功能,为深入探讨几丁质酶的免疫防御机制,本实验利用RACE技术克隆了三疣梭子蟹(Portunus trituberculatus)PtCht6基因。该基因cDNA全长2736bp,开放阅读框(ORF)2103bp,编码700个氨基酸,具有几丁质酶GH18家族典型特征。利用实时荧光定量技术分析PtCht6在三疣梭子蟹不同组织、不同蜕皮阶段、不同病原感染以及低盐胁迫(11)下的表达特征,结果显示:PtCht6在各组织中均有表达且在肝胰腺中的表达量最高;在不同蜕皮时期的肝胰腺中,其表达量由蜕皮后期(A/B)、蜕皮间期(C)、蜕皮前期(D)依次递减(P0.05);人工感染WSSV和副溶血弧菌后.PtCht6的表达量在肝胰腺中分别于12h、72h达到最大值,在血细胞中均于12h达到最大值,且相较于对照组,整体显著上调表达(P0.05);低盐胁迫能够显著抑制该基因的表达,最高抑制73倍(P0.05)。同时发现,低盐环境下感染WSSV后,该基因达到峰值的时间明显延迟(至少延迟12h.P0.05)。该研究结果预示PtCht6作为免疫因子参与三疣梭子蟹的病原防御,且低盐胁迫在一定程度上抑制了该基因的免疫功能。  相似文献   

军曹鱼（Rachycentron canadum）幼鱼对环境低氧胁迫氧化应激与能量利用指标的响应     

李洪娟  陈刚  郭志雄  王维政  黄建盛  曾泽乾 《海洋学报》2020,42(4):12-19

本文探究环境低氧对军曹鱼(Rachycentron canadum)氧化应激和能量利用指标的影响，为军曹鱼的健康养殖提供参考依据。通过设置低氧胁迫–恢复实验，将军曹鱼幼鱼(平均体质量(220.67±20.73)g)在低氧((2.64±0.25)mg/L)胁迫3 h及复氧((6.34±0.15)mg/L)8 h、24 h和48 h后，测定其肝脏和肌肉组织的氧化应激与能量利用指标。结果显示，低氧胁迫后，肝脏中丙二醛（Malondialdehyde，MDA)、过氧化氢酶(Catalase，CAT)和谷胱甘肽还原酶(Glutathione Reductase，GR)活力均显著低于对照组(p<0.05)，乳酸脱氢酶(Lactate Dehydrogenase，LDH)活性显著高于对照组(p <0.05)；肌肉中MDA和脂质过氧化物(Lipid Peroxidase，LPO)活性均显著低于对照组(p<0.05)，超氧化物歧化酶(Superoxide Dismutase，SOD)和LDH活性均显著高于对照组(p<0.05)；肌糖原和肝糖原含量极显著低于对照组(p<0.01)。复氧过程中，肝脏和肌肉中MDA、LPO、SOD、CAT、谷胱甘肽过氧化物酶(Glutathione Peroxidase，GPx)和GR含量均出现不同程度的升高；肝糖原在复氧24 h后显著高于对照组(p<0.05)，复氧48 h后显著低于对照组(p<0.05)；肌糖原在复氧8 h、24 h和48 h后均显著低于对照组(p<0.05)。研究表明，低氧胁迫能够对军曹鱼幼鱼机体造成一定的氧化损伤，肝脏和肌肉组织的酶活力和能量供应发生变化；低氧胁迫后的再复氧环境，对机体造成更为强烈的氧化损伤，可通过自身生理调节逐渐恢复到正常水平。  相似文献   

基于ABAQUS的深水连接器连接性能分析     

曹博  蔡志杰  石中玉  张玉龙  段梦兰 《海洋工程》2020,38(3):132-139

为解决现有深水连接器连接性能研究中力学分析建模不准确,且缺乏抗弯抗扭能力分析的问题,基于ABAQUS有限元分析软件对深水连接器进行三维模型动态仿真分析,对连接器的受力、密封性能以及在实际工程需求中不同内压下的抗弯及抗扭性能进行深入研究。结果表明:在安装及生产两种工况下,深水连接器各部件除密封环外受力均满足其强度设计要求,密封环接触表面发生合理塑性变形,满足密封要求;随着内压的增加,深水连接器的抗弯能力逐渐下降,抗扭能力则呈现增加的趋势;极限弯矩分别在0 MPa与35 MPa内压下的判定依据为密封失效,在14 MPa与52 MPa内压下的判定依据为下毂座屈服,而极限扭矩在不同内压下的判定依据均为密封失效。  相似文献   

KK型管节点应力集中系数几何敏感性分析     

林海花  孙承猛  石强 《海洋工程》2020,38(6):142-150

KK型管节点是自升式平台桁架式桩腿中的一种管节点，其应力集中系数是影响桩腿疲劳寿命的重要参数。应力集中系数与管节点的几何形式密切相关，为分析KK型管节点应力集中系数对几何参数的敏感性，利用ANSYS软件对某KK型管节点进行几何参数化建模，利用有限元数值模拟方法对各工况下的热点应力进行分析，并分别计算各相应工况下的名义应力，然后将热点应力与名义应力相比得到不同几何参数下的热点应力集中系数。对计算结果进行整理分析，得到了KK型管节点应力集中系数对无量纲几何参数的敏感性规律。结果表明，应力集中系数与撑杆受力状态、管节点结构形式有关，在满足结构布置、建造工艺和其他安全性指标的前提下，分析结果能够为KK型管节点的结构设计和疲劳分析提供技术支撑。  相似文献   

Unified numerical study of shallow foundation on structured soft clay under unconsolidated and consolidated-undrained loadings     

Santosh Kumar Yadav  Guan-lin Ye  Usama Khalid 《Marine Georesources & Geotechnology》2020,38(4):400-416

Abstract

Based on a new elasto-plastic constitutive model, this paper presents a soil–water coupled numerical prediction of the bearing capacity for shallow foundation constructed on Ballina soft clay for unconsolidated undrained (UU) and consolidated undrained (CU) conditions. This elasto-plastic constitutive Shanghai model has an advantage of describing the mechanical behaviour of over-consolidated and structured soil under different loading and drainage conditions, by using one set of material parameter. In this paper, the Shanghai model used for both UU and CU conditions has the same initial parameters obtained from laboratory test results. The loading conditions and consolidation stages vary based on construction details. The predicted bearing pressure-settlement responses for UU and CU, approves the field observation. The phenomenon of gaining the bearing capacity due to consolidation is captured and explained by the use of soil–water coupled numerical analysis with a new elasto-plastic model. The stress strain behaviour, stress paths and the decay of the structure of elements at different depths presented in this study, reveal the mechanism for the difference between UU and CU conditions to understand the foundation behaviour. Effect of the initial degree of soil structure on the bearing capacity is also addressed. Overall, this approach provides the integrated solution for the shallow foundation design problems under short and long-term loadings.  相似文献   

Dynamic characteristics of marine soft clay under variable phase difference and initial static shear stress     

Wenqian Dong  Xiuqing Hu  Hongtao Fu 《Marine Georesources & Geotechnology》2020,38(7):770-785

Abstract

Under seismic loading, the soil layer is subjected to multidirectional cyclic shear stress with different amplitudes and frequencies because of the coupling of multiple shear waves and the soil element within a slope or behind a retaining wall is subjected to initial static shear stress before subjected to cyclic loading. Due to the complexity of seismic loading propagation, a phase difference exists between the initial static shear stress and cyclic shear stress. To investigate the influence of the phase difference and initial static shear stress on cyclic shear strain, cyclic modulus, and cyclic strength, a series of laboratory tests are performed on Wenzhou marine soft clay by multi-directional simple shear system, which can simulate the actual state better by controlling the horizontal cyclic stress in the x and y directions simultaneously. As the phase difference varies from 0° to 90°, the dynamic shear modulus increases and cyclic strain accumulation decreases with an increasing number of cycles. The shear strain increases with the initial shear stress.  相似文献   

Effect of microstructure on stress–strain and pore-pressure response of sabarmati sand under the influence of mica     

P. Seethalakshmi 《Geomechanics and Geoengineering》2020,15(2):123-139

ABSTRACT

Micaceous soil is believed to be detrimental for civil engineering constructions due to the effect of high compressibility, low compacted density and low shear strength. Individual mica particle has numerous intact mica flakes foliated over each other making it flexible upon loading and rebound upon unloading due to its low hardness and resilient nature. Hence, micaceous soils with mica content more than 10% are considered undesirable for highway pavements, embankments and railway track constructions. When platy mica particles are sufficiently numerous to interact with spherical sand particles, bridging and ordering phenomena are augmented within the soil mass creating unique sand-mica particle orientation (MS microstructure) unlike sand-sand particle orientation (PS microstructure). The current experimental research was conducted to evaluate the variation in stress–strain, pore pressure and effective stress path response of Sabarmati sand under the influence of mica (sand with 30% mica and pure sand) with MS and PS microstructure respectively. Effect of particle crushing on stress–strain and pore pressure response was also studied on Sabarmati sand with MS and PS microstructure. Distinctive macroscopic response was observed in Sabarmati sand with MS microstructure under the influence of mica as well as mica particle crushing.  相似文献   

Effects of wave directionality on extreme response for a long end-anchored floating bridge     

《Applied Ocean Research》2019

Reliable design codes are of great importance when constructing new civil engineering concepts such as floating bridges. Previously only a scarce number of floating bridges have been built in rough wave conditions and only limited knowledge of the extreme environmental conditions and the associated extreme response exists. To form a better design basis an increased understanding of the sensitivity in the structural response towards changes in short-crested sea parameters is needed. Furthermore, acquiring the necessary accuracy in simulated extreme response is often a computationally expensive endeavour and the number of simulations needed is often based on experience. The present study investigates the wave-induced short-term extreme response of a simplified end-anchored floating bridge concept for several wave environments with a return period of 100 years. The study includes convergence of the coefficient of variation for the extreme response for different realization lengths as well as number of realizations. The sensitivity in the structural response towards different main wave directions and spreading exponents is investigated and includes both transverse and vertical displacement response spectra and extreme Von Mises stress in the bridge girder cross-section. The extreme response is based on an accuracy of 2% in the coefficient of variation equivalent to 40 3-h realizations and a low sensitivity in the response is found for natural occurring spreading exponents and for main wave directions within 15° from beam sea.  相似文献   

海气动量通量研究综述   总被引：1，自引：0，他引：1  

冯兴如  李水清  尹宝树 《海洋科学》2018,42(10):103-109

海气界面动量通量也称为风应力,是海流和表面海浪的主要驱动力,是海洋从大气获得动量的重要途径。因此,合理可靠的海洋表面风应力的参数化对于海洋、大气和波浪以及气候模式的准确预报都具有非常重要的科学意义和实用价值。对风应力拖曳系数的参数化是风应力参数化的主要内容。近来的观测发现,风应力拖曳系数随着风速的增加出现了先增后减的趋势,同时还与海面的波浪状态以及海流有关。基于观测或理论分析,目前已经得到了一系列的风应力拖曳系数计算方法或公式,有的考虑了海浪的作用,有的没有,但这些方案大都是适合中低风速,在高风速下的适用性还有待检验。本文回顾了目前在海气动量通量观测和参数化方面的研究进展,并建议应增加高风速下风速、海流以及海浪等的同步观测,以进一步完善风应力参数化方案。  相似文献   

A plasticity constitutive model for unsaturated,anisotropic, nonexpansive soils     

Panagiotis Sitarenios  Michael Kavvadas 《国际地质力学数值与分析法杂志》2020,44(4):435-454

The paper describes and evaluates an incremental plasticity constitutive model for unsaturated, anisotropic, nonexpansive soils (CMUA). It is based on the modified Cam-Clay (MCC) model for saturated soils and enhances it by introducing anisotropy (via rotation of the MCC yield surface) and an unsaturated compressibility framework describing a double dependence of compressibility on suction and on the degree of saturation of macroporosity. As the anisotropic and unsaturated features can be activated independently, the model is downwards compatible with the MCC model. The CMUA model can simulate effectively: the dependence of compressibility on the level of developed anisotropy, uniqueness of critical state independent of the initial anisotropy, an evolving compressibility during constant suction compression, and a maximum of collapse. The model uses Bishop's average skeleton stress as its first constitutive variable, favouring its numerical implementation in commercial numerical analysis codes (eg, finite element codes) and a unified treatment of saturated and unsaturated material states.  相似文献