Coherent nanoprecipitates within a biogenic single crystal: From spinodal decomposition to a prestressing strategy

We recently discovered a unique biostrategy for strengthening and toughening brittle crystals of calcite [1]. Our studies on the atomic- and nano-structure of the mineralized lenses of the brittle star Ophiocoma wendtii revealed the presence of metastable coherent nanoprecipitates that induce compressive stress on the crystal. Although the final nanostructure is akin to the Guinier–Preston (GP)zones well known in classical metallurgy the brittle star achieves this nanostructure via a completely novel mechanism, in which crystals are formed at ambient conditions from a supersaturated amorphous precursor having coherently aligned nanoprecipitates and coherently alternating stress and elastic modulus layers. This induces compressive stress, which strengthens and toughens the mineralized tissue. In this talk I will present our study on the characterization of such crystals utilizing state-of-the-art techniques and will present the most possible mechanism of their formation both in biological and synthetic systems. [2] Please click Additional Files below to see the full abstract

Senior Volunteerism: Dissatisfaction and Turnover Among Older Volunteers

This study examined levels of satisfaction with dimensions of the volunteer job to determine whether there was a meaningful association between dissatisfaction with the volunteer job and the decision to discontinue volunteering among senior volunteers. Very little association was found to exist. Senior volunteers who stopped volunteering were only somewhat less satisfied with their volunteer jobs than those who continued to volunteer. Rather, the findings suggest that other reasons, namely poor health, the need for paid employment, and other personal reasons accounted for turnover among older volunteers

Bio-inspired hybrid nanocomposites in single crystalline hosts: From structure to function

Often crystals in nature exhibit fascinating mechanical, optical, magnetic and other characteristics. Such natural single crystals are very different than man-made crystals: they are in fact hybrid nanocomposites due to the incorporation of organic molecules within heir crystalline lattice and often reveal intricate shapes and morphologies rather than clear facets. In this talk I will show that we can emulate these two specific features demonstrated by organisms so as to form new structural materials with new properties and characteristics. I will show that we can grow inorganic single crystals in which different organic molecules are incorporated on a nanometer scale. This incorporation has pronounced effects on the crystal structure of the crystal host and depending on the choice of materials can enhance the mechanical properties, manipulate its electronic properties and even serve as a drug delivery platform with highly controlled release properties. I will also show that using this bio-inspired approach we can grow functional single crystals that demonstrate no facets but rather have intricate shapes such as nanoporous morphologies (nano sponge) or curved surfaces and yet maintain their single crystal nature. We believe that our approach will open up new ways to control the structure and properties of smart materials

Hybrid gold single crystals incorporating amino acids

Composite hybrid gold crystals are of profound interest in various research areas ranging from materials science to biology. Their importance is due to their unique properties and potential implementation, for example in sensing or in bio-nanomedicine. Here we report on the formation of hybrid organic-metal composites via the incorporation of selected amino acids histidine, aspartic acid, serine, glutamine, alanine, cysteine, and selenocystine into the crystal lattice of single crystals of gold. We used electron microscopy, chemical analysis and high-resolution synchrotron powder X ray diffraction to examine these composites. Crystal shape, as well as atomic concentrations of occluded amino acids and their impact on the crystal structure of gold, were determined. Concentration of the incorporated amino acid was highest for cysteine, followed by serine and aspartic acid. Our results indicate that the incorporation process probably occurs through a complex interaction of their individual functional groups with gold atoms. Although various organic gold composites have been prepared, to the best of our knowledge this is the first reported finding of incorporation of organic molecules within the gold lattice. We present a versatile strategy for fabricating crystalline nanohybrid composite gold crystals of potential importance for a wide range of applications

Situs inversus totalis: A report of a case presenting with an acute abdomen

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Bioinspired nanocomposites: Ordered 2D materials within a 3D lattice

Advanced composites are used in a variety of industrial applications and therefore attract much scientific interest. We recently developed a novel carbon‐based nanocomposite via incorporation of graphene oxide (GO) into the crystal lattice of single crystals of calcite [1]. Incorporation of a 2D organic material into single‐crystal lattices has never before been reported. To characterize the resulting nanocomposites, high‐resolution synchrotron powder X‐ray diffraction, electron microscopy, transmission electron microscopy, fluorescence microscopy and nanoindentation tests are employed. A detailed analysis reveals a layered distribution of GO sheets incorporated within the calcite host (Fig. 1). Moreover, the optical and mechanical properties of the calcite host are altered when a carbon‐based nanomaterial is introduced into its lattice. Compared to pure calcite, GO/calcite composite crystals exhibit lower elastic modulus and higher hardness. The results of this study show that the incorporation of a 2D material within a 3D crystal lattice is not only feasible but also can lead to the formation of hybrid crystals exhibiting new properties. Please click Additional Files below to see the full abstract