 Subjects -> INSTRUMENTS (Total: 62 journals)
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- Regulation of Cell Behavior by Hydrostatic Pressure
- Authors: Liu S; Tao R, Wang M, et al.
Abstract: Hydrostatic pressure (HP) regulates diverse cell behaviors including differentiation, migration, apoptosis, and proliferation. Abnormal HP is associated with pathologies including glaucoma and hypertensive fibrotic remodeling. In this review, recent advances in quantifying and predicting how cells respond to HP across several tissue systems are presented, including tissues of the brain, eye, vasculature and bladder, as well as articular cartilage. Finally, some promising directions on the study of cell behaviors regulated by HP are proposed.
PubDate: Tue, 23 Jul 2019 00:00:00 GMT
- A Survey of Models of Ultraslow Diffusion in Heterogeneous Materials
- Authors: Liang Y; Wang S, Chen W, et al.
Abstract: Ultraslow diffusion is characterized by a logarithmic growth of the mean squared displacement (MSD) as a function of time. It occurs in complex arrangements of molecules, microbes, and many-body systems. This paper reviews mechanical models for ultraslow diffusion in heterogeneous media from both macroscopic and microscopic perspectives. Macroscopic models are typically formulated in terms of a diffusion equation that employs noninteger order derivatives (distributed order, structural, and comb models (CM)) or employs a diffusion coefficient that is a function of space or time. Microscopic models are usually based on the continuous time random walk (CTRW) theory, but use a weighted logarithmic function as the limiting formula of the waiting time density. The similarities and differences between these models are analyzed and compared with each other. The corresponding MSD in each case is tabulated and discussed from the perspectives of the underlying assumptions and of real-world applications in heterogeneous materials. It is noted that the CMs can be considered as a type of two-dimensional distributed order fractional derivative model (DFDM), and that the structural derivative models (SDMs) generalize the DFDMs. The heterogeneous diffusion process model (HDPM) with time-dependent diffusivity can be rewritten to a local structural derivative diffusion model mathematically. The ergodic properties, aging effect, and velocity autocorrelation for the ultraslow diffusion models are also briefly discussed.
PubDate: Tue, 09 Jul 2019 00:00:00 GMT
- Mechanics of Strong and Tough Cellulose Nanopaper
- Authors: Meng Q; Wang T.
Abstract: Cellulose nanopaper, which consists of a porous network of cellulose nanofibrils (CNFs), exhibits excellent mechanical properties with high strength and toughness. The physical mechanisms, including a realizable reduction of defect size in the nanopaper and facile formation/reformation of hydrogen bonds among CNFs, suggest a bottom-up material design strategy to address the conflict between strength and toughness. A thorough exploration of the rich potential of such a design strategy requires a fundamental understanding of its mechanical behavior. In this review, we supply a comprehensive perspective on advances in cellulose nanopaper mechanics over the most recent two decades from the three aspects of mechanical properties, structure–property relationship and microstructure-based mechanical modeling. We discuss the effects of size, orientation, polymerization degree, and isolate origins of CNFs; density or porosity and humidity of nanopaper; and hemicellulose and lignin on the mechanical properties of cellulose nanopaper. We also discuss the similarities and differences in the microstructure, mechanical properties, and toughening mechanisms between cellulose nanopaper and cellulose nanocrystal (CNC) nanopaper, chitin nanopaper, carbon nanotube (CNT) nanopaper, and graphene nanopaper. Finally, we present the ideas, status quo, and future trends in mechanical modeling of cellulose nanopaper, including atomistic- and microscale-level numerical modeling, and theoretical modeling. This review serves as a modest spur intended to induce scientists to present their valuable contributions and especially to design more advanced cellulose nanopapers and promote the development of their mechanics.
PubDate: Tue, 09 Jul 2019 00:00:00 GMT
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