家蚕细胞周期素E基因在5龄幼虫组织表达的剪切变体和表达谱特征

细胞周期素E（cyclinE）是调控细胞周期从G1期进入S期的关键因子。利用家蚕基因组数据库信息设计引物,克隆家蚕cyclinE在5龄幼虫不同组织表达的cDNA序列,获得该基因的6种不同剪切变体,这6种剪切变体前4个外显子和最后一个外显子都相同,变化主要集中在第5~7外显子处。同源性比对显示,不同物种来源的cyclinE周期蛋白盒区域具有较高的保守性,有35个氨基酸的共同保守序列,该区域可能也是家蚕cyclinE的特异识别并结合细胞周期素依赖蛋白激酶的功能区域。利用实时定量PCR分析显示,cyclinE在家蚕5龄第3天幼虫的中肠、脂肪体、丝腺、脑、马氏管、精巢、卵巢、血液等8种组织、器官中均有表达,并且在脂肪体中的表达相对较高,推测cyclinE基因在家蚕脂肪体细胞分裂过程中发挥重要作用。

吸力路径对非饱和土力学性质的影响

基质吸力的存在使得土的工程性状变得十分复杂。非饱和土的力学性质,不仅受基质吸力及竖向荷载等应力状态的影响,吸力路径也起着不可忽视的作用。为了探讨不同吸力路径对非饱和土应力-应变关系和强度的影响,采用非饱和土直剪仪对不同吸力路径固结平衡的非饱和土样进行直剪试验,获得其固结量及应力-应变关系,得到了不同吸力路径对非饱和土抗剪强度的影响规律。试验结果表明:在相同的竖向荷载条件下,非饱和土的抗剪强度随着吸力的增加明显增大。在相同吸力及竖向荷载条件下,经历过较高吸力历史的试样固结量和前期剪切强度明显增大。

促甲状腺激素β剪接变体在自身免疫性甲状腺炎小鼠甲状腺中的表达

目的探讨促甲状腺激素（TSH）β剪接变体在甲状腺球蛋白（强）免疫诱发的自身免疫性甲状腺炎小鼠甲状腺中的表达及碘过量对表达的影响，了解TSHβ剪接变体是否参与了自身免疫性甲状腺炎发生的病理过程。方法选7～8周龄的BALB／c小鼠48只，雌雄各24只，体质量20—25g。根据小鼠的体质量和性别，采用随机数字表法分为4组，每组12只，雌雄各半。对照组：饮去离子水；免疫（TG）组：饮去离子水，每只小鼠在8周龄时注射0．1mgTg皮下免疫，分别在11周龄和15周龄时各加强免疫1次；高碘（HI）组：饮用0．05％碘化钠（NaI）水；联合（TG＋HI）组：饮0．05％NaI水，免疫同TG组。喂养8周后处死小鼠，采集外周血，通过化学免疫发光法测量血清中总甲状腺素和游离甲状腺素（TT4、FT4）、总三碘甲腺原氨酸和游离三碘甲腺原氨酸（TT3、FT3）水平；取小鼠甲状腺，冰冻切片后用于HE染色，光镜下观察甲状腺细胞形态改变。SYBRGreen荧光实时定量（RT）-PCR检测TSHβ剪接变体表达。结果肉眼下，与对照组比较，HI组和TG＋HI组小鼠甲状腺明显肿大，颜色暗红。光镜下，对照组小鼠甲状腺滤泡大小较一致，上皮细胞多呈立方形，滤泡腔内含丰富胶质，无淋巴细胞浸润；TG组甲状腺滤泡较一致，上皮细胞立方形，可见单个散在淋巴细胞；HI组可见甲状腺滤泡胶质蓄积性扩张，上皮细胞呈低立方状或扁平状，但少见淋巴细胞浸润；TG＋HI组甲状腺内多为胶质蓄积性大滤泡，上皮细胞扁平状，可见滤泡结构破坏及局部淋巴细胞浸润。小鼠FT3、FT4、FT4和TSHβ剪接变体表达组间比较差异有统计学意义（F=4．00、12．54、31．92、214．29，P均〈0．05）。与对照组比较，TG组TT3、TT4、FT4和TSHβ剪接变体表达升高（nmol／L：0．92±0．07比1．30±0．33、67．75±11．91比95．60±14．10；pmol／L：54．07±3．67比154．80±0．01；×10-3：4．1l±0．32比8．38±0．22；t值分别为-2．24、-3．02、-54．87、-19．11，P均〈0．05）；HI组TT4下降（nmol／L：67．75±11．91比45．50±3．85，t=3．55，P〈0．05）；TG＋HI组FT4和TSHB剪接变体表达升高（pmol／L：54．07±3．67比139．46±30．00；×10-3：4．11±0．32比5．33±1．47；t值分别为-5．65、-5．95，P均〈0．05）。结论Tg诱发了BALB／c小鼠自身免疫性甲状腺炎症反应，小鼠甲状腺中TSHβ剪接变体的表达明显升高，高碘可以加重Tg的这种反应，TSHβ剪接变体参与了自身免疫性甲状腺炎的病理过程。

脑胶质瘤组织中OCT4A和OCT4B水平及临床意义分析

目的探讨脑胶质瘤组织中八聚体结合转录因子4(OCT4)剪切变体OCT4A和OCT4B水平及临床意义。方法收集本院2011年1月至2016年12月手术切除并经病理证实的脑胶质瘤组织84例和正常脑组织36例,采用实时荧光定量PCR(QPCR)检测以上组织中的OCT4A和OCT4B mRNA水平,分析脑胶质瘤组织中OCT4A和OCT4B mRNA水平与临床病理参数(年龄、性别、病理分级、病理类型、分化程度、瘤周水肿及浸润深度)和预后的关系,采用Cox比例风险回归模型分析影响预后的因素。结果 84例脑胶质瘤组织中的OCT4A mRNA水平为2. 144±1. 293,高于36例正常组织的1. 181±0. 688(t=4. 212,P<0. 001); OCT4B mRNA水平为2. 912±1. 540,亦高于正常组织的1. 258±0. 882(t=6. 025,P<0. 001);脑胶质瘤组织中OCT4A和OCT4B mRNA水平呈正相关(r=0. 462,P=0. 012)。脑胶质瘤组织中OCT4A和OCT4B水平与患者的性别、年龄和瘤周水肿均无关,而与病理类型、分化程度和病理分级有关,且在胶质母细胞瘤、低分化和病理分级Ⅲ～Ⅳ级患者中较高(P<0. 05)。单因素分析发现脑胶质瘤患者的总生存期与性别、年龄、瘤周水肿和浸润深度均无关,而与病理类型、分化程度、病理分级及OCT4A和OCT4B表达水平有关(P<0. 05); Cox风险比例回归模型分析发现病理类型、分化程度、病理分级及OCT4A和OCT4B表达水平为影响预后的独立因素,其中胶质母细胞瘤、低分化程度、病理分级较晚及OCT4A、OCT4B高表达为风险因素。结论脑胶质瘤组织中OCT4A和OCT4B水平升高,且与病理类型、分化程度和病理分级有关,OCT4A和OCT4B高表达者的预后较差,可能参与了该恶性肿瘤的发生发展,对脑胶质瘤的诊治及预后预测有一定意义。

Numerical Analysis on Magnetic-induced Shear Modulus of Magnetorheological Elastomers Based on Multi-chain Model

Based on the magnetic interaction energy, using derivative of the magnetic energy density, a model is proposed to compute the magnetic-induced shear modulus of magnetorheological elastomers. Taking into account the influences of particles in the same chain and the particles in all adjacent chains, the traditional magnetic dipole model of the magnetorheological elastomers is modified. The influence of the ratio of the distance etween adjacent chains to the distance between adjacent particles in a chain on the magnetic induced shear odulus is quantitatively studied. When the ratio is large, the multi-chain model is compatible with the single chain model, but when the ratio is small, the difference of the two models is significant and can not be neglected. Making certain the size of the columns and the distance between adjacent columns, after constructing the computational model of BCT structures, the mechanical property of the magnetorheological elastomers composed of columnar structures is analyzed. Results show that, conventional point dipole model has overrated the magnetic-induced shear modulus of the magnetorheological elastomers. From the point of increasing the magnetic-induced shear modulus, when the particle volume fraction is small, the chain-like structure exhibits better result than the columnar structure, but when the particle volume fraction is large,the columnar structure will be better.

Casting effect on compressive brittleness of bulk metallic glass

An interesting phenomenon of cooling-rate induced brittleness in Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass （BMG） was reported. It was found that the as-cast BMG specimens exhibited a brittle-ductile transition when the larger specimens were machined into smaller specimens through removing the cast-softening surface layer by layer. After compression tests, the as-machined small specimens, owing to the absence of the cast-softening surface, displayed highly dense and intersecting shear bands, and extensive plastic deformation. This is in contrast to the catastrophic failure and low deformability in the as-cast large specimens. More free volume was detected in the smaller as-fractured specimens, by differential scanning calorimetry, which may be attributed to the occurrence of strain softening and increased plasticity. Compared with the relatively smooth fracture surface in the smaller specimens, the larger specimens showed more diverse features on the fracture surface due to their graded structures.

Effect of surfactants on hydrodynamics characteristics of bubble in shear thinning fluids at low Reynolds number

In this study,the effects of surfactants on the hydrodynamic characteristics of bubbles in shear-thinning fluids at low Reynolds number(Re<50)are investigated.The bubble terminal velocity and drag coefficient of bubble in clean and contaminated carboxymethylcellulose(CMC)solutions are obtained using a high-speed camera for examining differences.The results show that the existence of surfactant could reduce the terminal velocity of bubble at small volume(0.25wt%CMC:<100 mm3;0.50wt%CMC:<110 mm3),attributed to stiffening the bubble interface.However,this negative effect decreases and finally disappears with increasing bubble volume.The drag coefficient curves of the bubble in contaminated CMC solution exhibit behavior similar to that exhibited by a solid sphere at Re<10,indicating that internal circulation flow is absent at the bubble interface as compared to that in clean CMC solution.However,for 10<Re<40,a transition of drag curve from 24/Re to 16/Re in contaminated CMC solution is observed,which is easy at low SDS concentrations and high CMC concentrations.

Elastoplastic model for discontinuous shear deformation of deep rock mass

Deep rock mass possesses some unusual properties due to high earth stress,which further result in new problems that have not been well understood and explained up to date.In order to investigate the deformation mechanism,the complete deformation process of deep rock mass,with a great emphasis on local shear deformation stage,was analyzed in detail.The quasi continuous shear deformation of the deep rock mass is described by a combination of smooth functions:the averaged distribution of the original deformation field,and the local discontinuities along the slip lines.Hence,an elasto-plastic model is established for the shear deformation process,in which the rotational displacement is taken into account as well as the translational component.Numerical analysis method was developed for case study.Deformation process of a tunnel under high earth stress was investigated for verification.

Numerical simulation of single bubble rising in shear-thinning fluids by level set method

The behavior of single bubble rising in quiescent shear-thinning tlmds was lnvestlgateO numerically by level set metnoa. number of bubbles in a large range of Reynolds number and Eotvos number were investigated including spherical, oblate and spherical. The bubble shape and drag coefficient were compared with experimental results. It is observed that the simulated results show good conformity to experimental results over a wide range of Reynolds number. In addition, the detailed flow field based on the reference coordinate system moving with the bubble is obtained, and the relationship among flow field, bubble shape and velocity is discussed.

Deformation characteristics of coarse-grained soil with various gradations

By using large scale triaxial shearing apparatus,consolidated-drained shear tests were conducted on coarse-grained soil with different gradations.In order to describe their deformation rules,three main characteristics of tangent Poisson ratio curves were summarized and the reason was revealed by dividing the movement of soil particles into two kinds: the movement of fine particles and the movement of coarse particles.Then,a volumetric strain expression and a tangent Poisson ratio expression were put forward,and two defects of widely used Duncan-Chang model were fixed.Results calculated from them agree well with test results.There are three parameters,namely L,G and F,in this new model.Parameter L reflects the dilatancy of a specimen and L=4 can be used as a criterion to estimate whether a certain kind of soil has dilatancy quality or not.Parameters G and F relate to the initial slope of tangent Poisson ratio curves,and G=F=0 indicates a special situation which happens in dense granular material of the same diameter.Influences of various gradations on volume deformation are mainly reflected in parameter L which is smaller when there are more gravels in specimens.

A revisit of strain-rate frequency superposition of dense colloidal suspensions under oscillatory shears

Strain-rate frequency superposition(SRFS) is often employed to probe the low-frequency behavior of soft solids under oscillatory shear in anticipated linear response. However, physical interpretation of an apparently well-overlapped master curve generated by SRFS has to combine with nonlinear analysis techniques such as Fourier transform rheology and stress decomposition method. The benefit of SRFS is discarded when some inconsistencies of the shifted master curves with the canonical linear response are observed. In this work, instead of evaluating the SRFS in full master curves, two criteria were proposed to decompose the original SRFS data and to delete the bad experimental data. Application to Carabopol suspensions indicates that good master curves could be constructed based upon the modified data and the high-frequency deviations often observed in original SRFS master curves are eliminated. The modified SRFS data also enable a better quantitative description and the evaluation of the apparent structural relaxation time by the two-mode fractional Maxwell model.

Vibration and Instability of Third⁃Order Shear Deformable FGM Sandwich Cylindrical Shells Conveying Fluid

The vibration and instability of functionally graded material(FGM)sandwich cylindrical shells conveying fluid are investigated.The Navier-Stokes relation is used to describe the fluid pressure acting on the FGM sandwich shells.Based on the third-order shear deformation shell theory,the governing equations of the system are derived by using the Hamilton’s principle.To check the validity of the present analysis,the results are compared with those in previous studies for the special cases.Results manifest that the natural frequency of the fluid-conveying FGM sandwich shells increases with the rise of the core-to-thickness ratio and power-law exponent,while decreases with the rise of fluid density,radius-to-thickness ratio and length-to-radius ratio.The fluid-conveying FGM sandwich shells lose stability when the non-dimensional flow velocity falls in 2.1-2.5,which should be avoided in engineering application.

Shear and extensional rheology of entangled polymer melts: Similarities and differences

This work extends our previous understanding concerning the nonlinear responses of entangled polymer solutions and melts to large external deformation in both simple shear and uniaxial extension. Many similarities have recently been identified for both step strain and startup continuous deformation, including elastic yielding, i.e., chain disentanglement after cessation of shear or extension, and emergence of a yield point during startup deformation that involves a deformation rate in excess of the dominant molecular relaxation rate. At a sufficiently high constant Hencky rate, uniaxial extension of an entangled melt is known to produce window-glass-like rupture. The present study provides evidence against the speculation that chain entanglements tie up into "dead knots" in constant-rate extension because of the exponentially growing chain stretching with time. In particular, it is shown that even Instron-style tensile stretching, i.e., extending a specimen by applying a constant velocity on both ends, results in rupture. Yet, in the same rate range, the same entangled melt only yields in simple shear, and the resulting shear banding is clearly not a characteristic of rupture. Thus, we conclude that chain entanglements respond to simple shear in the manner of yielding whereas uniaxial extension is rather effective in causing some entanglements to lock up, making it impossible for the entanglement network to yield at high rates.

Unanswered questions in unsaturated soil mechanics

The last two to three decades have seen significant advances in the mechanics of unsaturated soils.It is now widely recognized that the fundamental principles in soil mechanics must cover both saturated and unsaturated soils.Nevertheless,there is still a great deal of uncertainties in the geotechnical community about how soil mechanics principles well-established for saturated soils can be extended to unsaturated soils.There is even wide skepticism about the necessity of such extension in engineering practice.This paper discusses some common pitfalls related to the fundamental principles that govern the volume change,shear strength and hydromechanical behaviour of unsaturated soils.It also attempts to address the issue of engineering relevance of unsaturated soil mechanics.