Amazing state transitions!

Here are some interesting papers published recently.

NATURE COMMUNICATIONS | ARTICLE

  

Ultra-responsive soft matter from strain-stiffening hydrogels

Maarten Jaspers, Matthew Dennison, Mathijs F. J. Mabesoone, Frederick C. MacKintosh, Alan E. Rowan and Paul H. J. Kouwer

Few synthetic hydrogels are known to display strain-stiffening behaviour. Here, Jaspers et al. show how concentration, polymer length and temperature can be used to modify the mechanical properties of synthetic gels to access mechanically highly sensitive and responsive materials

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

Z. Wang, B. A. Sun, H. Y. Bai and W. H. Wang

Glasses are known to have very slow flow behaviour on application of force, but the structural basis for this flow is currently unclear. Here Wang et al. use a dynamic mechanical analysis to study the flow phenomena in a La-based metallic glass.

Nature Materials January 2015 Volume 14, No 1

Colloidal matter

Model colloidal systems provide insight into aspects of the structure and dynamics of particulate systems on a broad range of length and time scales. In this focus issue, we highlight recent developments in colloidal self-assembly and colloidal phase transitions.

Order through entropy
Daan Frenkel
Nature Materials 14, 9–12 (2015) doi:10.1038/nmat4178
Published online 17 December 2014

FW: [Perspective] How Shape Affects Microtubule and Nanoparticle Assembly

[Description: Figure]

It is quite interesting to observe the change of shapes under some stimulus for better structures and functions.

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Part of the tantalizing promise of nanoparticles is that they can serve as building blocks of complex systems that could outperform other materials. For example, different structures could form depending on the shape of the nanoparticles. A stimulus, such as a change in temperature or the addition of a small molecule, that changes nanoparticle shape could create a new structure with a different function. Nature provides a large example set of nanoparticles in the form of proteins, which can be studied to gain insight into shape-dependent assembly. In a recent paper, Ojeda-Lopez et al. (1<http://www.sciencemag.org/content/343/6174/981.full#ref-1>) describe a new shape-changing mechanism that dramatically alters how a protein system assembles. The α–β tubulin dimer naturally polymerizes to form microtubules. The authors discovered that adding a highly charged small molecule, spermine, causes a shape transformation. The tubules assemble within an inverted structure compared to that of the original microtubules.
Microtubules, the track along which kinesin motor proteins walk, are a key component underlying cellular transport and cell division (2<http://www.sciencemag.org/content/343/6174/981.full#ref-2>). These functions occur in part because of the special properties derived from tubulin, which are of interest to general polymer physics and to the development of synthetic systems, such as ones performing nanoscale transport (3<http://www.sciencemag.org/content/343/6174/981.full#ref-3>). Microtubules assemble, dissociate, and reassemble in cells, and the dynamics of polymerization and depolymerization depends on binding of guanosine triphosphate (GTP) and its dephosphorylation to guanosine diphosphate (GDP). With GTP bound to tubulin, straight growth of the tubule occurs, but the transition to GDP alters the tubulin geometry, tending to cause filaments to peel away in arcs, and leads to catastrophic depolymerization.
Ojeda-Lopez et al. stabilized the microtubules using taxol. The subsequent addition of spermine produced arcs peeling away from the tubule, similar to the effect of dephosphorylation (see the figure). However, the spermine-induced structure is an inverted tubulin tubule (ITT)—a spiral tubule with tubulin orientation inverted with respect to the microtubule orientation. The ITT has a larger diameter, 40 nm, versus 24 nm for microtubules.


Feed: Science: Current Issue
Posted on: Friday, 28 February 2014 11:00 AM
Author: Mark J. Stevens
Subject: [Perspective] How Shape Affects Microtubule and Nanoparticle Assembly

Models of nanoparticle assembly can help explain aspects of the inverted structure that forms because of induced change in tubulin protein shape. Author: Mark J. Stevens


View article...<http://www.sciencemag.org/content/343/6174/981.abstract?rss=1>

Read books in 2012

好像这两本领域差的有点远，不过觉得对自己的工作还是有些意义的，所以就坚持读了。（图片来源网络或者自己手机拍照）
《01》讲述物质堆积的内容，希望对自己的工作有所帮助，不过目前还没有相关工作发表。
《02》是从连续方法的角度对流化进行分析，介绍了particle bed model在一维和二维情况下的应用。虽然自己流化床方面的工作主要是基于偶合的连续流体力学和离散颗粒方法，但这本书对过程的理解和分析还是很有帮助的。本人关于流化床发表的工作有（做下广告）：

1. Hou, Q.F., Zhou, Z.Y. & Yu, A.B. (2012). Micromechanical modeling and analysis of different flow regimes in gas fluidization. Chemical Engineering Science, 84, 449-468.
2. Hou, Q.F., Zhou, Z.Y. & Yu, A.B. (2012). Computational study of the heat transfer in bubbling fluidized beds with a horizontal tube. AIChE Journal, 58, 1422-1434.
3. Hou, Q.F., Zhou, Z.Y. & Yu, A.B. (2012). Computational Study of the Effects of Material Properties on Heat Transfer in Gas Fluidization. Industrial & Engineering Chemistry Research, 51, 11572-11586.

01 The Pursuit of Perfect Packing

By Tomaso Aste, D. L. Weaire

A review from website (http://books.google.com.au/books/about/The_Pursuit_of_Perfect_Packing.html?id=d8bZDWcSdzMC&redir_esc=y)
Coauthored by one of the creators of the most efficient space packing solution, the Weaire–Phelan structure, The Pursuit of Perfect Packing, Second Edition explores a problem of importance in physics, mathematics, chemistry, biology, and engineering: the packing of structures. Maintaining its mathematical core, this edition continues and revises some of the stories from its predecessor while adding several new examples and applications.
The book focuses on both scientific and everyday problems ranging from atoms to honeycombs. It describes packing models, such as the Kepler conjecture, Voronoï decomposition, and Delaunay decomposition, as well as actual structure models, such as the Kelvin cell and the Weaire–Phelan structure. The authors discuss numerous historical aspects and provide biographical details on influential contributors to the field, including emails from Thomas Hales and Ken Brakke.
With examples from physics, crystallography, engineering, and biology, this accessible and whimsical book touches on many aspects of packing objects. It will help you understand components of packing and aid you in the quest for the perfect packing solution.

02 Fluidization-dynamics
L. G. Gibilaro

A review from google books:

Fluidization Dynamics has been written for students and engineers who find themselves involved with problems concerning the fluidized state. It presents an analysis that focuses directly on the problem of predicting the fluid dynamic behaviour of a proposed fluidized system for which empirical data is limited or unavailable. 

The second objective is to provide a treatment of fluidization dynamics that is readily accessible to the non-specialist. The linear approach adopted in this book, starting with the formulation of predictive expressions for the basic forces that act on a fluidized particle, offers a clear way into the theory. The incorporation of the force terms into the conservation equations for mass and momentum and subsequent applications are presented in a manner that requires only the haziest recollection of elementary fluid-dynamics theory. 

The analyses presented in this book represent a body of research that has appeared in numerous publications over the last 20 years. L.G. Gibilaro has taken the opportunity to reorder much of the material in the light of subsequent knowledge, to correct minor errors and inconsistencies and to add detail and clarification where necessary. This material helps to form the basis for university course modules in engineering and applied science at undergraduate and graduate level, as well as focused, post-experienced courses for the process, and allied industries. 

• Bridges the gulf between observed behaviour and fluid-dynamic theory
• Clear account of basic theory of fluidization
• Accessible treatment of fluidization analysis

A simulation work published in Nature: phase transition

As a researcher in simulation and modelling, feel excited. I would like to share this paper with you guys!

Structural transformation in supercooled water controls the crystallization rate of ice Nature 479, 7374 (2011). doi:10.1038/nature10586 Authors: Emily B. Moore & Valeria Molinero One of water's unsolved puzzles is the question of what determines the lowest temperature to which it can be cooled before freezing to ice. The supercooled liquid has been probed experimentally to near the homogeneous nucleation temperature, TH ≈ 232 K, yet the mechanism of ice crystallization—including the size and structure of critical nuclei—has not yet been resolved. The heat capacity and compressibility of liquid water anomalously increase on moving into the supercooled region, according to power laws that would diverge (that is, approach infinity) at ∼225 K (refs 1, 2), so there may be a link between water's thermodynamic anomalies and the crystallization rate of ice. But probing this link is challenging because fast crystallization prevents experimental studies of the liquid below TH. And although atomistic studies have captured water crystallization, high computational costs have so far prevented an assessment of the rates and mechanism involved. Here we report coarse-grained molecular simulations with the mW water model in the supercooled regime around TH which reveal that a sharp increase in the fraction of four-coordinated molecules in supercooled liquid water explains its anomalous thermodynamics and also controls the rate and mechanisms of ice formation. The results of the simulations and classical nucleation theory using experimental data suggest that the crystallization rate of water reaches a maximum around 225 K, below which ice nuclei form faster than liquid water can equilibrate. This implies a lower limit of metastability of liquid water just below TH and well above its glass transition temperature, 136 K. By establishing a relationship between the structural transformation in liquid water and its anomalous thermodynamics and crystallization rate, our findings also provide mechanistic insight into the observed dependence of homogeneous ice nucleation rates on the thermodynamics of water.

摄影师拍放大250倍沙粒显微照: 结构精细似雪花

说是沙粒，其实应该是各种微粒的集合，因为已经不是沙了。太漂亮了，不解释。

Applied Physics: Knot Your Simple Defect Lines?

（该图借用娃她妈博客发图，表示感谢）

中国有句俗语叫'快刀斩乱麻'。说的就是如果一团麻打结到一起的时候，与其慢慢解开，不如用刀斩断。可见打结给人带来的是头疼的麻烦，不容易完美解决。这事最近还真让我遇到了，给儿子买了一个大风筝，线据说有上百米长。带出去玩的时候，悲剧发生了，儿子意欲掌控风筝，接过绕线的轴，上面为了方便收放有一些结构，你懂的！接过，不小心有几圈线脱落下来，这下打结了。想要慢慢绕开恐怕不是短时间能够解决的（虽然理解上来，这种打结应该就是简单的过程的重复迭代，但是关键不知道他的迭代方程啊）。于是乎，出狠招，把轴上面的线全部放下，抓住线头我一下一下的绕，问题解决了。哈哈，有风的时候可以再玩了！这个例子说明的是打结带给我们的麻烦。

而今天推荐的这个文章就不一样了，它讲的是利用打结，把液晶中的线性位错，经过打结改善品质！图示为常见和论文讨论的打结。

(this figure is from science)

The ordering of molecules in a liquid crystal is disrupted by colloidal particles and creates lines of defects, which can be manipulated to form loops and knots. Author: Randall D. Kamien

View article...

snow flake-try attachment

some beautiful flowers. These beautiful photos are generated by Kenneth G. Libbrecht, please refer to the website (for more photos)