Finite element models and molecular dynamic simulations for studying the response of mast cell under mechanical activation

In micropipette aspiration experiment, increasing mechanical stress applied to cell membrane induced degranulation of mast cell as well as a current that could be inhibited by an inhibitor, which is specific for the transient receptor potential vanilloid （TRPVs） channels. To determine the sensitivity of TRPVs to membrane strain and tension, and to gain new insights into the activation mechanism of TRPVs, finite element models of mast cell and molecular dynamic simulations of human aquaporin-1 are presented. During the finite element simulations, the cell membrane sustained to micropipette aspiration was simulated, and the strain distribution along membrane thickness direction was obtained. Besides, combining the finite element models of osteoblast aspirated into micro- pipette and other compared models, we examined the relationship between cell mechanical stimulations and mechanical attributes and presented a new perspective to determine the cell equivalent elastic modulus. Consid- ering the indetermination of TRPV crystal structure, human aquaporin-1, one kind of the channel membrane proteins, substituting for TRPV, has been studied with molecular dynamic （MD） simulations, under different external lateral tensions which have been obtained in mast cell finite ele- ment simulations, to investigate the mechanical stimulation effects on the membrane channels. The simulations show that human aquaporin-1 undergoes significant conforma- tional change and expands in accordance with lateraltension, which not only confirms the tendency of the pre- vious electrophysiological experiments but also leads us to a better understanding of TRPVs. The multi-scale study combining finite element simulation and MD simulation is a significant breakthrough in the field of mechanical mechanism in cell system.     

Synthesis of Ta C and Ta_2C from tantalum and graphite in the laser-heated diamond anvil cell

The pressure dependence of the onset of the formation of Ta C and Ta2 C from the elements has been investigated by in situ X-ray diffraction and pyrometry.Ta C has been synthesized by the reaction of Ta and graphite at pressures between 8.6 and 14.3 GPa and at temperatures up to 2,300 K using a laser-heated diamond anvil cell. The products were characterized by X-ray diffraction. Ta and graphite begin to react around 1,100 K at ambient pressure conditions, and the reaction temperature increases with increasing pressure. A linear extrapolation of these data is consistent with recent observations of the formation of Ta C at 90 GPa and 3,600 K. We show that diffusion of carbon into tantalum significantly changes the lattice parameter of up to 2 % in the pressure range of up to19 GPa. In some experiments, Ta2 C was formed concomitantly. The experimentally determined bulk modulus of Ta2 C is B0;exp：= 286（5） GPa. Other tantalum carbide phases were not observed.     

Structural phase transition and metallization in compressed SrC_2

The structural, dynamical, and electronic properties of compressed Sr C2 were systematically investigated up to 200 GPa by using ab initio method. Three new phases are obtained by means of evolutionary algorithm. The confirmed most stable structure has C2/c symmetry at zero pressure, which transforms into an orthorhombic Cmcm phase at 4.5 GPa, followed by another orthorhombic Immm phase, which is stabilized at wide pressure range of 21.5–123.5 GPa, and then transformed into Mg B2-type phase（space group, P6/mmm）. Although Sr C2 has similar structural transformation to that of compressed Ca C2, Sr C2 holds small electron–phonon coupling,which leads to its low superconducting critical temperature（only 1.8 K）.     

Compression behavior of Sm）2Ti2O7-pyrochlore up to 50 GPa：single-crystal X-ray diffraction and density functional theory calculations

Single-crystal X-ray diffraction at pressures up to 50 GPa has been employed to study the compression behavior of Sm2Ti2O7-pyrochlore. In contrast to earlier reports, we observed no pressure-induced amorphization or pressure-induced anion disorder up to 50 GPa. The experimental study has been complemented by density functional theory-based calculations. A combination of the theoretical and experimental data yields a bulk modulus of 185 GPa, significantly higher than a value which had been reported earlier. In comparison to earlier work, the current study provides more reliable data due to the use of neon as a pressure medium, which provides a more hydrostatic pressure than the aluminum, which had been employed as a pressure medium in the earlier studies. An analysis of the compressibility of Al2B2O7 pyrochlores shows an approximately linear dependence of the bulk modulus on the unit cell volume.     

某型飞机一起机身异常振动故障分析

<正>1故障基本情况某部本场组织某型飞机进行起落航线训练,第一轮训练结束飞机着陆后,飞行员解除限动,同时脚踩刹车减速时感觉飞机异常振动明显。当飞行员停止刹车时,飞机又平稳滑行。在飞机转向滑行道时,先刹车减速,同时使用前轮转弯操作手柄操纵前轮转弯困难。2故障机理分析产生飞机异常震动的原因主要为:(1)机轮LS-108A轴承调节衬套调整不当,或轮毂、轴承及调节衬套不配套,使主轮轴向间隙过大产生震动。(2)调节衬套与轴承安装的螺帽松动。(3)机轮轴承严重磨损产生间隙。(4)刹车系统故障。     

一例发动机加速异响故障的诊断

<正>一辆奥迪C5A6轿车,配备1.8T发动机和自动变速器,行驶里程为10万km。车主反映发动机在2、3挡加速时有"咯啦、咯啦"异响声,声音已经持续了约半个月的时间,且时有时无,直到最近这两天声音变得明显起来。该车来我校汽修厂后,经试车发现声音果然如车主所述,在2、3挡时加速听见发动机传出"咯啦咯啦"声,听声音确实像发动机的爆震声,但发动机的动力并没有受到什么影响,原地加速发动机声音一切正常。根据我们的维修经验,结合故障分析,认为发动机在2、3挡加速     

电线电缆绝缘高温压力试验测量不确定度分析及评定

本文对外径约6mm及以下的电线电缆高温压力试验检测结果的测量不确定度进行评估,结果为29.6%,扩展不确定度为4.4%,其不确定度主要来源于压痕深度的测量。     

鱼类的深潜极限

<正>人们早就发现,在海洋中最深的约2 5%的部分(8400~11000米)里并没有鱼类生存。对此,长期以来人们都有一种推测。认为是因为那里的压力太大。但是,那里的深海生物本来就非常少,因此一直也没有发现直接证据。鱼类的体细胞内有一种叫做"氧化三甲氨"(TMAO)的化     

鄂尔多斯盆地南泥湾超低渗油藏物性及孔隙结构特征

在岩心观察基础上,根据铸体薄片、扫描电镜、压汞等资料,对鄂尔多斯盆地南泥湾超低渗油藏的物性和孔隙结构特征进行了深入研究,并分析了其影响因素.研究结果表明,该区块属于典型的低孔、超低渗油藏,储层以粒间溶孔和残余粒间孔为主,孔隙组合为粒间孔-溶孔和溶孔-粒间孔.孔隙直径小,面孔率低,分布不均匀,平均配位数小于1.5.喉道类型以片状和弯片状为主,多为细孔喉,孔隙间连通性差,存在比较多的无效孔隙.储层岩性细、压实程度高以及重结晶作用是造成孔隙度小,喉道狭窄,渗透率低的主要原因.灰质含量对渗透率的影响也十分明显.研究成果为开发措施的实施提供了依据.     

成型压力对废弃物基地质聚合物制品性能的影响

采用压制成型法,利用工业固体废渣为原料,制备了一类能耗低、免烧的地质聚合物.研究了压制成型时成型压力对制品强度、体积密度、吸水率、软化系数、耐磨性、耐水性以及抗冻融循环的影响,并结合SEM及XRD分析试样的微观形貌和矿物组成.试验结果表明:成型压力对地质聚合物制品的性能有重要影响,制备该废弃物基地质聚合物制品的最佳成型压力为30 MPa.