scholarly journals Foamy oysters: vesicular microstructure production in the Gryphaeidae via emulsification

2020 ◽  
Vol 17 (170) ◽  
pp. 20200505
Author(s):  
Antonio G. Checa ◽  
Fátima Linares ◽  
Julia Maldonado-Valderrama ◽  
Elizabeth M. Harper

The vesicular microstructure is a very distinctive arrangement of calcite, consisting of hollow cavities (vesicles) of diverse sizes and shapes, usually elongated in the direction of shell thickening. It is uniquely found among living bivalves in a single oyster family, Gryphaeidae. The vesicles are distributed in lenses interleaved with compact foliated layers. We have studied the morphology and distribution of vesicles within the lenses using optical and electron microscopy, and micro-computed tomography. At a small scale, vesicles do not follow a classical von Neumann–Mullins route typical of ideal foams. At a larger scale, the initiation and evolution of a vesicular layer statistically proceed like a foam, with vesicles becoming more numerous, larger and more even in size. In summary, the vesicular material follows a foam-like coarsening to reduce the number of energetically costly interfaces. However, a steady state is never reached because the animal permanently introduces energy in the system by creating new vesicles. The fabrication of the vesicular material is mediated by the production of an emulsion between the extrapallial fluid and the precursor PILP of the calcitic walls within the thin extrapallial space. For this mechanism to proceed, the mantle cells must perform highly sophisticated behaviours of contact recognition and secretion. Accordingly, the vesicular material is under mixed physical–biological control.

Author(s):  
Daniel H. Morse ◽  
Arlyn J. Antolak ◽  
Bernice E. Mills

X-ray radiography has long been recognized as a valuable tool for detecting internal features and flaws. Recent developments in microfabrication and composite materials have extended inspection requirements to the resolution limits of conventional radiography. Our work has been directed toward pushing both detection and measurement capabilities to a smaller scale. Until recently, we have used conventional contact radiography, optimized to resolve small features. With the recent purchase of a nano-focus (sub-micron) x-ray source, we are now investigating projection radiography, phase contrast imaging and micro-computed tomography (μ-CT). Projection radiography produces a magnified image that is limited in spatial resolution mainly by the source size, not by film grain size or detector pixel size. Under certain conditions phase contrast can increase the ability to resolve small features such as cracks, especially in materials with low absorption contrast. Micro-computed tomography can provide three-dimensional measurements on a micron scale and has been shown to provide better sensitivity than simple radiographs. We have included applications of these techniques to small-scale measurements not easily made by mechanical or optical means. Examples include void detection in meso-scale nickel MEMS parts, measurement of edge profiles in thick gold lithography masks, and characterization of the distribution of phases in composite materials. Our work, so far, has been limited to film.


2018 ◽  
Vol 38 (5) ◽  
pp. 199-210 ◽  
Author(s):  
Xiu-Wei Yu ◽  
Hao Wang ◽  
Zhong-Wei Wang

Variation of yarn fiber volume fraction, induced by the compression between adjacent yarns during the manufacturing process of textile composites, is difficult to be determined by using a single imaging method. A method combining scanning electron microscopy and micro-computed tomography is proposed to quantify the variation of yarn fiber volume fraction of textile composites, which is decomposed into systematic trend and stochastic deviation. The method takes the advantages of high resolution of scanning electron microscopy and wide 3D view of micro-computed tomography. Average fiber cross-sectional areas are acquired by analyzing hundreds of fiber cross-sectional areas in scanning electron microscopic images. Yarn cross-sectional area is determined by fitting ellipse to the labeled yarn cross-section in slices of micro-computed tomography images. The results of E-glass/epoxy and carbon/epoxy specimens show that their systematic trends of yarn fiber volume fraction combined with standard deviations of stochastic deviation, relative to the respective global means, fluctuate between [−11.4%, 15.3%] and [−12.9%, 10.7%], respectively. Yarn FVF varies in specimen obviously and needs to be considered in mechanical property prediction.


Sign in / Sign up

Export Citation Format

Share Document