Homer. The Iliad. A Student Guide, de Michael Silk y Homer. The Odyssey. A student Guide, de Jasper Griffin

Fil: Fernández Deagustini, María del Pilar. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Homer. The Iliad. A Student Guide, de Michael Silk y Homer. The Odyssey. A student Guide, de Jasper Griffin

Fil: Fernández Deagustini, María del Pilar. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Homer. The Iliad. A Student Guide, de Michael Silk y Homer. The Odyssey. A student Guide, de Jasper Griffin

Fil: Fernández Deagustini, María del Pilar. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Correlation Between Processing Conditions, Microstructure and Mechanical Behavior in Regenerated Silkworm Silk Fibers

Regenerated silkworm fibers spun through a wet-spinning process followed by an immersion postspinning drawing step show a work to fracture comparable with that of natural silkworm silk fibers in a wide range of spinning conditions. The mechanical behavior and microstructure of these high performance fibers have been characterized, and compared with those fibers produced through conventional spinning conditions. The comparison reveals that both sets of fibers share a common semicrystalline microstructure, but significant differences are apparent in the amorphous region. Besides, high performance fibers show a ground state and the possibility of tuning their tensile behavior. These properties are characteristic of spider silk and not of natural silkworm silk, despite both regenerated and natural silkworm silk share a common composition different from that of spider silk.

Sequential origin in the high performance properties of spider dragline silk

Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers.

Identification and dynamics of polyglycine II nanocrystals in Argiope trifasciata flagelliform silk

Spider silks combine a significant number of desirable characteristics in one material, including large tensile strength and strain at breaking, biocompatibility, and the possibility of tailoring their properties. Major ampullate gland silk (MAS) is the most studied silk and their properties are explained by a double lattice of hydrogen bonds and elastomeric protein chains linked to polyalanine β-nanocrystals. However, many basic details regarding the relationship between composition, microstructure and properties in silks are still lacking. Here we show that this relationship can be traced in flagelliform silk (Flag) spun by Argiope trifasciata spiders after identifying a phase consisting of polyglycine II nanocrystals. The presence of this phase is consistent with the dominant presence of the –GGX– and –GPG– motifs in its sequence. In contrast to the passive role assigned to polyalanine nanocrystals in MAS, polyglycine II nanocrystals can undergo growing/collapse processes that contribute to increase toughness and justify the ability of Flag to supercontract.

Mechanical behaviour and formation process of silkworm silk gut

High performance silk fibers were produced directly from the silk glands of silkworms ("Bombyx mori") following an alternative route to natural spinning. This route is based on a traditional procedure that consists of soaking the silk glands in a vinegar solution and stretching them by hand leading to the so called silkworm guts. Here we present, to the authors’ best knowledge, the first comprehensive study on the formation, properties and microstructure of silkworm gut fibers. Comparison of the tensile properties and microstructural organization of the silkworm guts with those of naturally spun fibers allows gain of a deeper insight into the mechanisms that lead to the formation of the fiber, as well as the relationship between the microstructure and properties of these materials. In this regard, it is proved that an acidic environment and subsequent application of tensile stress in the range of 1000 kPa are sufficient conditions for the formation of a silk fiber.

The New Silk Road: a versatile instrument in China’s policy. OSW Commentary No. 161, February 10 2015

Introduction. The Chinese leader Xi Jinping presented the concept of the New Silk Road – a collection of land and maritime routes – in autumn 2013. Initially, it envisaged the creation of a network of infrastructural connections, mainly transport corridors, between China and its most important economic partner – Europe. The concept grew in importance throughout 2014 to become the key instrument of China’s foreign policy, especially in the areas of public diplomacy and soft power. Towards the end of 2014, the Chinese government announced it would establish a Silk Road Fund worth US$40 billion. The New Silk Road idea is a flexible formula used by China in its dialogue with many other countries. Its inclusive nature helps contribute to diluting the negative impression caused by China’s rapid economic expansion and assertiveness in foreign policy, especially with regard to its neighbours. The process of implementing the New Silk Road concept will allow China to expand its influence within its neighbourhood: in Central and South-Eastern Asia. The New Silk Road will be an alternative point of reference to the US dominance and Russian integration projects in these regions. The concept will legitimise and facilitate the growth of China’s influence in the transit countries on the route to Western Europe, i.e. in the Middle East (Arab countries, Israel and Turkey, the Horn of Africa and Central Europe (the Balkans and the Visegrad Group countries). This concept is also essential for China’s domestic policy. It has become one of Xi Jinping’s main political projects. It will boost the development of China’s central and western provinces. The fact that the concept is open and not fully defined means that it will be a success regardless of the extent to which it will be implemented in practice. Its flexible nature allows China to continue investments already initiated bilaterally and to present them as components of the New Silk Road concept.