Numerical and Experimental Studies of Liquid Crystalline Flow Induced by Annihilation of Paired Defects

Author(s):  
Masahiro Kuroiwa ◽  
Tomohiro Tsuji ◽  
Shigeomi Chono

Numerical and experimental studies of liquid crystalline flow induced by the annihilation of paired defects have been achieved by using the Doi theory coupled with the Marrucci-Greco potential. The molecular orientation distribution function is approximated by a series of spherical harmonic functions, to reduce the computational task. It is empirically known that the defects with different types of molecular orientation configuration attract each other, and finally annihilate. During this annihilation process, the liquid crystalline flow will be induced through the rotation of the molecular orientation direction. It is found from the numerical results that vortex-like liquid crystalline flow is induced around the defects come closer. The numerical predictions are induced liquid crystalline flow is confirmed by the experiment.

Polymer ◽  
2004 ◽  
Vol 45 (15) ◽  
pp. 5341-5352 ◽  
Author(s):  
Stanley Rendon ◽  
Wesley R. Burghardt ◽  
Anthony New ◽  
Robert A. Bubeck ◽  
Lowell S. Thomas

An analytic method is presented for calculation of the orientation distribution function (ODF). It is very rapid, since the amount of computation does not depend on the value of the applied shear. The existence of a hypothetical reference texture is also demonstrated, which plays a central role in the present approach. With the aid of this ‘texture’ and the initial texture, the current ODF is uniquely defined as a function of strain. Shear textures in face-centred cubic (FCC) polycrystals are predicted analytically in this way on the basis of the uniform strain (Taylor) hypothesis and the theory of rate dependent slip. Two special fibres are examined closely, and it is shown that they undergo periodic variations. The period is fixed for the cube-on-face fibre, but depends on rate sensitivity in the cube-on-edge case. The results obtained for the two fibres compare very well with previous completely numerical predictions, and are also consistent with the only available set of experimental results. The present predictions, which can be obtained very easily and rapidly, are useful for testing large deformation computer codes for texture simulation.


1975 ◽  
Vol 8 (2) ◽  
pp. 185-235 ◽  
Author(s):  
D. Chapman

The concept that the liquid crystalline or mesomorphic condition was of importance to biological systems is a relatively old idea. Thus Bernal (1933) when discussing the different types of arrangements of molecules in liquid crystals commented ‘Such structures belong to the liquid crystal as a unit and not to its molecules which may be replaced by others without destroying them and they persist in spite of the complete fluidity of the substance. These are just the properties to be required for a degree of organization between that of the continuous substance, liquid or crystalline solid and even the simplest living cell.’ Stewart (1961) some thirty years later also stated that ‘It is this property – the combination of flow and lability with a preferred and relatively stable molecular orientation – that makes the mesomorphic (i.e. liquid crystal) phase uniquely appropriate to the structure of protoplasm and living tissue.’


Author(s):  
Wendy Putnam ◽  
Christopher Viney

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.


2006 ◽  
Vol 2006 (suppl_23_2006) ◽  
pp. 175-180
Author(s):  
G. Gómez-Gasga ◽  
T. Kryshtab ◽  
J. Palacios-Gómez ◽  
A. de Ita de la Torre

Author(s):  
Б.И. Гельцер ◽  
Э.В. Слабенко ◽  
Ю.В. Заяц ◽  
В.Н. Котельников

Одним из основных требований к разработке экспериментальных моделей цереброваскулярных заболеваний является их максимальная приближенность к реальной клинической практике. В работе систематизированы данные по основным методам моделирования острой ишемии головного мозга (ОИГМ), представлена их классификация, анализируются данные о преимуществах и недостатках той или иной модели. Обсуждаются результаты экспериментальных исследований по изучению патогенеза ОИГМ с использованием различных моделей (полной и неполной глобальной, локальной и мультифокальной ишемии) и способов их реализации (перевязка артерий, клипирование, коагуляция, эмболизация и др.). Особое внимание уделяется «стабильности» последствий острого нарушения мозгового кровообращения: необратимых ишемических повреждений головного мозга или обратимых с реперфузией заданной продолжительности. Отмечается, что важное значение в этих исследованиях должно принадлежать современным методам прижизненной визуализации очагов острого ишемического повреждения, что позволяет оценивать динамику патологического процесса. Предлагаемый метод отвечает требованиям гуманного обращения с животными. Подчеркивается, что выбор релевантной модели ОИГМ определяется задачами предстоящего исследования и технологическими ресурсами научной лаборатории. Development of experimental models for acute forms of cerebrovascular diseases is essential for implementation of methods for their prevention and treatment. One of the principal requirements to such models is their maximum approximation to actual clinical practice. This review systematized major models of acute cerebral ischemia (ACI), their classification, and presented information about their advantages and shortcomings. Also, the review presented results of experimental studies on pathophysiological mechanisms of different types of modeled ACI (complete and incomplete global, local, and multifocal ischemia) and methods for creating these models (arterial ligation, clipping, coagulation, embolization, etc.). Particular attention was paid to “stability” of the consequences of acutely impaired cerebral circulation - an irreversible ischemic brain injury or a reversible injury with reperfusion of a given duration. The authors emphasized that in such studies, a special significance should be given to intravital imaging of acute ischemic damage foci using modern methods, which allow assessing the dynamics of the pathological process and meet the requirements to humane treatment of animals. The choice of a relevant ACI model is determined by objectives of the planned study and the technological resources available at the research laboratory.


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