STEPHEN WEINER

..We also suspect that ACC fulfils many different functions, including as a transient precursor phase during the formation of crystalline calcium carbonate...

..Structure is thus in many respects the foundation upon which the field of biomineralization rests...

..The few graphite-like microcrystallites found in fossilized charcoal were composed of onion-like structures that are probably less prone to oxidation owing to their rounded structures...

..Charcoal and bone collagen samples located above and below one of the fragments produced dates of around 18,000. These ceramic potsherds therefore provide some of the earliest evidence for pottery making in China...

..Our results support and expand upon the hypothesis that the durability of the whole tooth relies upon a bucco-lingual asymmetric matching of stiffness by means of an interphase: a cushioning soft layer between enamel and bulk dentin...

..As the tablets grow, the silk-fibroin is pushed aside and becomes sandwiched between the mineral and the chitin layer...

..All this takes place in a highly structured chitinous framework. Here we present ideas on how these disparate components work together to produce the highly structured pearly nacreous layer of the mollusk shell...

..This counterintuitive approach to extracting relatively well preserved DNA from bones significantly improves the chances of obtaining authentic ancient DNA sequences, especially from human bones...

..0 GPa. Our approach can be used to map deformations on irregular surfaces, and measure strain on wet samples of varying sizes. This can be extended to the study of other biological materials including bone and synthetic biomaterials...

..We conclude that for the most part, that enamel and not dentin dictates the mechanical behavior of the whole tooth...

..We suggest that these results demonstrate the importance of enamel cap morphology in directing deformation behavior; an ability stemming from the stiffness of the enamel cap overlying the more pliable dentin...

..We show that this method can be used to accurately and precisely measure the effective elastic modulus of mouse cortical bone...

..The observed differentiation in the distribution of matrix components and their functional groups shows that the different stages of single crystal growth are highly controlled by the matrix...

..It is also shown that within a relatively small bone specimen there are considerable variations in the modulus, presumably caused by structural inhomogeneities...

..Clearly the formation of the tooth, and the tooth tip in particular, is amazingly well controlled. The improved understanding of these structural features could lead to the design of better mechanical grinding and cutting tools...

..We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism...

..Crystal growth, on the other hand, is apparently not influenced by the matrix, in contrast to many other biomineralization systems...

..Although we do not know, as yet, the function of these proteins, their generally conserved sequences do indicate that they might well fulfill basic functions in shell formation...

..Deposition of transient amorphous phases as a strategy for producing single crystals with complex morphology may have interesting implications for the development of sophisticated materials...

..We conclude that ACC fulfills an important function in mollusc larval shell formation. It is conceivable that ACC may also be involved in adult shell formation...

..Comparing the mechanisms of growth of the nacreous and prismatic layers can help to understand the underlying strategies of formation of mineralized structures...

..The integration of the two techniques demonstrates that new mineral is delivered and deposited as packages of amorphous calcium phosphate nanospheres, which transform into platelets of crystalline apatite within the collagen matrix...

..Based on these findings, we propose that this amorphous calcium phosphate phase may be a precursor phase that later transforms into the mature crystalline mineral...

..A mechanism of geometric frustration is suggested, whereby the presence of the tetrahedral silicate ion in the flat carbonate lattice prevents organization into crystalline polymorphs...

..The results will improve understanding of the aging process of human osteonal bone, and will allow better evaluation of possible effects that treatments for osteoporosis may have on mechanical function of bone. ..

..The structural information from normal bones will be compared with that from bones suffering pathology, in order to identify any significant differences, and hopefully relate these to the manner in which the tissue malfunctions...

..Knowledge of the molecular organization of bone should form the basis for understanding its formation, its role during calcium homeostasis, its destruction during remodeling and its biomechanical functions as a structural support system...

..Detailed maps of microhardness, as well as local strain values using Moire fringes, will be produced and then related back to tooth structure. ..

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