关键词： Molecular dynamics   Calcium silicate hydrate   Dynamic mechanical behaviors  

摘要： Dynamic mechanical behaviors of the calcium silicate hydrate (C-S-H) under shock compression loading in layered direction have been investigated by molecular dynamics (MD) simulations. The various piston velocities ranging from 0.2 to 3.0 km/s used to describe the propagation of stress waves have been employed in our MD simulations. The shock Hugoniot curve and the distribution of particle velocity are obtained. It is found that the Hugoniot elastic limit is 7.5 GPa, and the impact may induce elastic response, elastic-plastic response and shock regime. Our results reveal that only a continuous elastic wave exists when the particle velocity is below 0.5 km/s, while a new wave is generated when the particle velocity is at 0.5 km/s. With further increasing the particle velocity, a two-wave structure is generated. After the particle velocity is larger than 2.0 km/s, the shock wave is dominant. These findings provide important atomic insights for understanding the dynamic mechanical behaviors of C-S-H.

关键词： epithelial-to-mesenchymal transition   ESCRT machinery   receptor trafficking   signaling dynamics   SMAD2   TGF-β  

摘要： Signal transduction pathways stimulated by secreted growth factors are tightly regulated at multiple levels between the cell surface and the nucleus. The trafficking of cell surface receptors is emerging as a key step for regulating appropriate cellular responses, with perturbations in this process contributing to human diseases, including cancer. For receptors recognizing ligands of the transforming growth factor beta (TGF-beta) family, little is known about how trafficking is regulated or how this shapes signaling dynamics. Here, using whole genome small interfering RNA (siRNA) screens, we have identified the ESCRT (endosomal sorting complex required for transport) machinery as a crucial determinant of signal duration. Downregulation of ESCRT components increases the outputs of TGF-beta signaling and sensitizes cells to low doses of ligand in their microenvironment. This sensitization drives an epithelial-to-mesenchymal transition (EMT) in response to low doses of ligand, and we demonstrate a link between downregulation of the ESCRT machinery and cancer survival.

关键词： epithelium   adhesion   mechanical forces   morphogenesis   growth   homeostasis  

摘要： During epithelial tissue development, repair, and homeostasis, adherens junctions (AJs) ensure intercellular adhesion and tissue integrity while allowing for cell and tissue dynamics. Mechanical forces play critical roles in AJs’ composition and dynamics. Recent findings highlight that beyond a well-established role in reinforcing cell-cell adhesion, AJ mechanosensitivity promotes junctional remodeling and polarization, thereby regulating critical processes such as cell intercalation, division, and collective migration. Here, we provide an integrated view of mechanosensing mechanisms that regulate cell-cell contact composition, geometry, and integrity under tension and highlight pivotal roles for mechanosensitive AJ remodeling in preserving epithelial integrity and sustaining tissue dynamics.

关键词： Octanol model   Biphasic dissolution   Poorly soluble APIs   Hydrodynamics   Small-scale  

摘要： Biphasic dissolution models were proposed to provide good predictive power for in vivo absorption kinetics. However, up to date the impact of hydrodynamics in mini-scale models are not well understood. Consequently, the aim of this work was to investigate different setups of a previously published mini-scale biphasic dissolution model (miBIdi-pH-II) to better understand the relevance of hydrodynamics for evaluating kinetic parameters and to simultaneously increase the robustness of the experimental model. As a first step, the hydrodynamics within the aqueous phase were characterized by in silico simulations of the flow patterns. Different settings, such as higher rotation speeds of the paddles, the implementation of a second propeller into the aqueous phase, and different shapes of aqueous stirrers were investigated. Second, to evaluate the results of the in silico simulations, in vitro experiments with glitter were carried out. Last, the same settings were applied in the miBIdi-pH-II using dipyridamole (DPD) as model compound to estimate kinetic parameters by applying a compartment-based modelling approach. Both in vitro experiments with glitter or DPD demonstrated the adequateness of the previous in silico hydrodynamic simulations. The use of higher rotation speeds and a second aqueous propeller resulted in more homogeneous mixing of the aqueous phase. This resulted in faster distribution of dissolved active pharmaceutical ingredient (API) into the octanol phase. A kinetic model was successfully applied to quantify the influence of hydrodynamics on the partitioning rate of the API into the octanol phase. In conclusion, the combination of in silico and in vitro methods was demonstrated to be powerful for investigating the flow patterns within the miBIdi-pH-II. A comprehensive understanding of the hydrodynamics and the respective influence on the dissolution and apparent partitioning into the octanol phase in the biphasic dissolution model was obtained and completed

关键词： 机械多体系统   Euler-Lagrange方程   对称性   守恒量   平面连杆  

摘要： 为给复杂机械多体系统碰撞动力学问题的定量和定性分析提供一个强有力新工具,该文将现代分析力学中的对称性理论引入到机械多体外碰撞动力学研究中.首先,基于冲量动量法推导系统碰撞动力学的Euler-Lagrange方程;其次,引进群分析理论,根据不变性原则给出系统存在Noether对称性与Lie对称性的各自条件方程以及得到相应守恒量的形式,为动力学方程的解析积分理论提供了有效途径.最后以一平面开环两连杆机构的碰撞力学为例进行实际分析运用.研究表明,借助对称性和守恒量可以得到机械多体系统动力学更深层次的力学规律和运动特性,可为系统更精确的动态优化设计和先进控制奠定理论基础.

关键词： 学业帮扶   精细化管理   分级预警   本科生  

摘要： 本论文从上海交通大学机械与动力工程学院为例,结合学业帮扶机制、学业预警机制与精细化管理理念的基础上,引入并实践了本科生学业帮扶精细化管理模式,把学生工作的各个环节有机地联系起来,有效地提高了高校学生管理效率和教育质量,在提升本科生人才培养质量方面具有重要意义。

关键词： confinement effect   differentia spectra   glass-rubber transitions   linear confinement   molecular motions  

摘要： The confinement effect on molecular motions has been widely observed in polymeric blends and composites. For polymers that have softening dynamics in glass-rubber transition region, the confinement effect can influence the molecular motions to different degrees. In this work, the differentia spectra of dynamic mechanical analysis were applied to analyze the confinement effect in butyl rubber (IIR)/ethylene-vinyl acetate copolymer (EVA) blends, IIR/high-density polyethylene (HDPE) blends, chlorobutyl rubber (CIIR)/polystyrene (PS) blends, IIR/silica composites, and CIIR/organophilic montmorillonite (OMMT) composites. In the differentia spectra, the confinement effect from additional components on local segment motions (LSM), sub-Rouse modes, and Rouse modes was investigated, indicating that the effect on sub-Rouse modes is smaller than that on Rouse modes but larger than that on LSM. Moreover, the coupling effects slightly change with introduction of the secondary components, which enables us to assume that the confinement effect has a linear relationship with the content of secondary components. Finally, it has been found that the decrease in tan delta exhibited a linear relationship with the content of secondary components.

关键词： Nano-structures   Hybrid   Mechanical properties   Computational modelling  

摘要： Graphene and fullerenes are impressive nanostructures having great potential be used in many areas due to their unique physical and chemical properties. By hybridizing these nanostructural units, it is possible to obtain superior composite nanostructures with novel properties. In this study, a new hybrid nanostructure that will be named as graphene nanoribbon-fullerene (GNR-F) network is introduced by providing its tensile and compressive mechanical characteristics through molecular dynamics simulations. The proposed nanostructure is mainly an interconnected network of GNR units on which fullerenes are covalently grafted. Three different atomistic models are generated using different types of fullerenes (i.e. C60, C180 and C320) to investigate the effects of the fullerene types on the mechanical properties. After examining the thermodynamic stability of the specimens -by monitoring the free energy profiles and morphologic evolution within a sufficiently long period of time, deformation mechanisms of the specimens subjected to tensile and compression tests are investigated. Simulation results indicate that the proposed GNR-F network nanostructure has a ductile nature in tensile loading while its compressive response is foam-like with remarkable energy absorbing capacity. In addition to the expected effect of the fullerenes on the compressive behavior, a significant effect is also observed for the tensile response.

关键词： Broiler house   Computational fluid dynamics   Discharge coefficient   Fan performance curve   Mechanical ventilation   Orifice equation  

摘要： Precise ventilation control of broiler houses is essential to effectively exhaust pollutants and attain the required breeding environment. However, the ventilation rate used in practise is always lower than the desired or designed value because of difficulties in measuring the pressure difference between the indoor and outdoor pressure of the facility. In this study, a new formula was developed to estimate the total ventilation rate for mechanically ventilated broiler houses using the number of operating fans and the slot opening rate, both of which are relatively easy to measure in practice. The proposed formula was derived from the in-situ fan performance curve and the discharge coefficient, which represent the ventilation characteristics of the exhaust fans and slot openings respectively. This was evaluated through a field experiment and a computational fluid dynamics (CFD) simulation. The measured ventilation rate was 24.1-26.6% lower than the desired ventilation rate showing that the in-situ fan performance curve was 33.7 Pa lower on average than the designed fan performance curve provided by the manufacturer. The distribution of static pressure in the broiler house was analysed using CFD models and it was found that the new formula could be applied to broiler houses having difference lengths. (C) 2018 IAgrE. Published by Elsevier Ltd. All rights reserved.

关键词： Carbon allotrope   Mechanical properties   Molecular dynamics simulation   Novamene  

摘要： We have investigated through fully atomistic reactive molecular dynamics and density functional theory simulations, the mechanical properties and fracture dynamics of single-ringed novamene (1R-novamene), a new 3D carbon allotrope structure recently proposed. Our results showed that 1R-novamene is an anisotropic structure with relation to tensile deformation. Although 1R-novamente shares some mechanical features with other carbon allotropes, it also exhibits distinct ones, such as, extensive structural reconstructions. 1R-novamene presents ultimate strength (similar to 100 GPa) values lower than other carbon allotropes, but it has the highest ultimate strain along the z-direction (similar to 22.5%). Although the Young's modulus (similar to 600 GPa) and ultimate strength values are smaller than for other carbon allotropes, they still outperform other materials, such as for example silicon, steel or titanium alloys. With relation to the fracture dynamics, 1R-novamene is again anisotropic with the fracture/crack propagation originating from deformed heptagons and pentagons for x and y directions and broken sp(3) bonds connecting structural planes. Another interesting feature is the formation of multiple and long carbon linear chains in the final fracture stages. (C) 2018 Elsevier Ltd. All rights reserved.