行为的结构、刚性和多样性

有关动物行为的定义、结构和多样性是一个被长期忽视的研究领域。然而 ,动物行为多样性不仅是一个生物多样性基础理论问题 ,也与濒危动物的成功保护有关。本文定义了动物行为以及行为的刚性与弹性 ,探讨了行为表达的空间条件以及生境因素与行为多样性之间的关系。我们发现雌雄大熊猫个体在较大的活动空间里的发情行为表现的频次及活动频率显著地高于那些在较小的空间里的雌雄个体 ,说明活动空间对雄性或雌性大熊猫的发情行为有显著影响。圈养空间影响麋鹿的社会行为、通讯行为和聚群行为。圈养在小圈中的麋鹿没有出现同性聚群现象 ,当圈养麋鹿野放后即表现出这种现象。圈养环境中长大的动物个体由于缺乏行为的表达空间 ,仅仅表现出刚性大的行为 ,丧失了许多弹性大的行为 ,从而导致动物行为的多样性下降。对那些生活在开阔草原和荒漠上的野生有蹄类动物实施迁地保护时 ,必须考虑其逃逸空间 ,为那些动物建立自然保护区时 ,则必须考虑其迁移空间。此外 ,动物行为的多样性与生境元素有关。我们应当给圈养动物提供复杂而多样的环境 ,以增加圈养野生动物表达寻找食物、建立领域、筑巢和避开不利环境等行为的可能性 。

组织刚性对企业并购目标选择的影响机理研究

受目标企业组织刚性影响,主并方在后期整合中往往面临着“我想但是我不能(I want but I can’t)”的现实矛盾,进而陷入“赢家诅咒”。为厘清目标企业组织刚性与其整合潜力之间的作用机制,采用探索性案例研究方法,对上汽与双龙之间的并购事件进行探究。研究表明:目标企业的整合潜力对并购整合的成败有着重要作用;企业并购认知分为机会认知与威胁认知两种,目标企业原有认知刚性、并购事件获益性和可控性共同对企业变革认知起锚定作用;资源能力协同互补性、管控模式的匹配性会影响目标企业对并购事件获益性和可控性的判断,从而影响其并购认知;机会认知下,目标企业的整合潜力较高,反之整合潜力较低。将目标企业组织刚性作为并购的前因变量,提出组织刚性对企业并购目标整合潜力的影响模型,从事前控制角度可为我国企业并购目标的选取提供一定参考。

Effects of temperature change on elastic behavior of steel beams with semi-rigid connections

Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.

Numerical evaluation of buckling behavior in space structure considering geometrical parameters with joint rigidity

The buckling behavior of single layer space structure is very sensitive. The joint rigidity, moreover, is one of the main factors of stability which may determine the entire failure behavior. Thus, the reasonable stiffness of joint system, which is neither total pin assumption nor perfect fix condition, is very important to apply to the real single layer space one. Therefore, the purpose of this work was to investigate the buckling behavior of single layer space structure, using the development of the upgraded stiffness matrix for the joint rigidity. To derive tangential stiffness matrix, a displacement function was assumed using translational and rotational displacement at the node. The geometrical nonlinear analysis was simulated not only with perfect model but also with imperfect one. As a result, the one and two free nodal numerical models were investigated using derived stiffness matrix. It was figured out that the buckling load increases in proportion to joint rigidity with rise-span ratio. The stability of numerical model is very sensitive with the initial imperfection, responding of bifurcation in the structure.

Post-fire cyclic behavior of reinforced concrete shear walls

The effects of fire exposure,reinforcement ratio and the presence of axial load under fire on the seismic behavior of reinforced concrete(RC) shear walls were investigated.Five RC shear walls were tested under low cyclic loading.Prior to the cyclic test,three specimens were exposed to fire and two of them were also subjected to a constant axial load.Test results indicate that the ultimate load of the specimen with lower reinforcement ratio is reduced by 15.8%after exposure to elevated temperatures.While the reductions in the energy dissipation and initial stiffness are 59.2%and 51.8%,respectively,which are much higher than those in the ultimate load.However,this deterioration can be slowed down by properly increasing reinforcement due to the strength and stiffness recovery of steel bars after cooling.In addition,the combined action of elevated temperatures and axial load results in more energy dissipation than the action of fire exposure alone.

Stiffness heterogeneity-induced double-edged sword behaviors of carcinoma-associated fibroblasts in antitumor therapy

Carcinoma-associated fibroblasts(CAFs) function as a double-edged sword in tumor progression. However,factors affecting the transition between tumor promotion and inhibition remain to be investigated. Here, we found that the transition was determined by stiffness heterogeneity of the tumor stroma in which tumor cells and CAFs were grown.When tumor cells were grown on a rigid plastic substrate,supernatants from CAFs inhibited the cytotoxic effects of 5-fluorouracil. In contrast, when tumor cells were grown on a soft substrate(5.3 kPa), supernatants from CAFs grown on a soft substrate increased the cytotoxicity of 5-fluorouracil. The diverse effects of CAFs were mediated by mechanotransduction factors, including stroma stiffness-induced cytokine expression in CAFs and signal transduction associated with stress fiber formation of CAFs. Moreover, we found that the cytokine expression in CAFs was regulated by nuclear Yesassociated protein, which changed according to cell stiffness,as characterized by atomic force microscopy. Overall, these findings suggested that modulating the mechanotransduction of the stroma together with CAFs might be important for increasing the efficacy of chemotherapy.