Elastic-plastic and fracture properties are key issues in characterizing materials' mechanical behavior, and they have been extensively studied for over a century for bulk structured materials. [1][2][3] Silicon is one of the most important and representative materials for these studies owing to its extremely important applications. [4,5] Silicon nanowires (NWs) are one of the most important nanostructures used for fabricating various electronic and optoelectronic nanodevices, [6,7] and they could be a building block for the construction and assembly of functional nanometer-scale systems. Although the electrical and optical properties of Si NWs have been extensively studied, only limited information is available about the structure-mechanical property correlations of Si NWs. This is likely due to the difficulty of carrying out in situ tensile or bending measurements on individual NWs. The elastic-plastic strains retained in NWs can significantly affect their electronic properties by perturbing the band structure or changing the Fermi energy of the nanostructures. [8] For example, the applied strains of continuous torsion on carbon NTs could result in chirality variation and therefore introduce a distinct conductance oscillation from metallic to semiconductor.[9] A straininduced giant piezoresistance effect has also been observed for Si NWs.[10]Results of studies of the elastic-plastic behavior of Si NWs are of technological importance. Silicon NWs are a potential candidate for building devices that are to be integrated with microelectronics and microelectromechanical systems (MEMS). They are also an outstanding candidate for constructing devices for flexible electronics. Several approaches have been developed to study the mechanical properties of NWs and nanotubes (NTs) based on atomic force microscopy (AFM) at nanometer-scale spatial resolution. [11,12] The major limitation of AFM measurements is that they are unable to reveal the atomic-scale structural evolution process during the in situ elastic-plastic-fracture process. Transmission electron microscopy (TEM) has been one of the most important and effective tools with a capability of atomic level imaging for investigating the in situ mechanical properties of single NWs and NTs, [13,14] although ex situ studies have to be carried out. [15,16] Direct and in situ atomic level imaging during tensile testing is fundamentally important to view and provide true physical insight into the elastic-plastic and fracture processes, [12,13] but this type of study is challenging experimentally.In this report, we present in situ TEM observation of the elastic-plastic-fracture processes of a single Si NW recorded at atomic resolution. The study directly shows the strain-induced structural evolution process of Si NWs and its largestrain plasticity (LSP). Our results indicate that the LSP of Si NWs via a brittle-ductile transition originates from a dislocation-initiated amorphization. This behavior is in contrast to the mechanical behavior of bulk Si. Our observation reveals a ...

Super‐plasticity of single‐crystal beta‐SiC [111] nanowires for > 200 % elongation was observed by in situ axial‐tensile experiments in a scanning electron microscope. The SiC nanowires were characterized by a bamboo‐like structure appearing as the 3C structured segments intergrowth along the nanowire. The axial localized plasticity and super‐plasticity are suggested to result only from the 3C segments, through dislocation generation, propagation and amorphization in contrast to the highly defected structural segments that conduct elastic‐deformation only, owing to the lack of slip systems. These results provide key information for understanding the mechanical behavior of SiC nanowires.

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Individual single-crystalline Si nanowires (NWs) were bent by forming loops or arcs with different radius. Positional-resolved atomic level strain distribution (PRALSD) along both of the radial and axial directions were calculated and mapped directly from the atomic-resolution strained high-resolution electron microscopy (HREM) images of the bent Si NWs. For the first time, the neutral-strain axis shifted from the compressive zone to the tensile region was directly demonstrated from the PRALSD along the radial direction. Bending-induced ripple-buckling of the bent Si NW was observed and a significant strain variation along the bending axial direction in the compressive region was revealed. The tensile surface atomic steps and the compressive buckling are the physical origin of the asymmetric tensile-compressive properties of postelastic instabilities and the incipient plasticity. Both of the tensile surface atomic-steps and the compressive buckling initiated versatile ductile plastic dislocation events.

Graves' disease is a common autoimmune disorder characterized by thyroid stimulating hormone receptor autoantibodies (TRAb) and hyperthyroidism. To investigate the genetic architecture of Graves' disease, we conducted a genome-wide association study in 1,536 individuals with Graves' disease (cases) and 1,516 controls. We further evaluated a group of associated SNPs in a second set of 3,994 cases and 3,510 controls. We confirmed four previously reported loci (in the major histocompatibility complex, TSHR, CTLA4 and FCRL3) and identified two new susceptibility loci (the RNASET2-FGFR1OP-CCR6 region at 6q27 (P(combined) = 6.85 × 10(-10) for rs9355610) and an intergenic region at 4p14 (P(combined) = 1.08 × 10(-13) for rs6832151)). These newly associated SNPs were correlated with the expression levels of RNASET2 at 6q27, of CHRNA9 and of a previously uncharacterized gene at 4p14, respectively. Moreover, we identified strong associations of TSHR and major histocompatibility complex class II variants with persistently TRAb-positive Graves' disease.