Controlling Deformability in Metallic Glass Nanopillars and Nanolattices

Metallic glasses offer desirable mechanical properties, including high strength, hardness, and elasticity. In bulk, they suffer from catastrophic failure upon mechanical loads. However, ductility may emerge upon (1) reducing the characteristic dimension of the metallic glass to the nanoscale or (2) irradiating the metallic glass. These two methods of controlling metallic glass deformability are investigated through a host of mechanical experiments on metallic glass nanopillars and nanolattices before and after irradiation. The mechanical experiments are conducted inside a scanning electron microscope to allow simultaneous mechanical loading and visualization of nanoscale deformation behavior. Such experiments reveal that helium irradiation of electrodeposited Ni73P27 metallic glass tensile nanopillars increases plasticity by a factor of two with no sacrifice in strength. Other tensile experiments on Zr-Ni-Al metallic glass nanopillars in as-sputtered and annealed states reveal substantial ductility, highly dependent upon both the nanopillar size and processing conditions. Molecular dynamics simulations, transmission electron microscopy, and synchrotron x-ray diffraction are used to explain the observed mechanical behavior through changes in free volume and short-range order. Larger nanolattice structures are fabricated to contain hollow beams of metallic glass, with beam wall thicknesses in the nanoscale size range that may allow proliferation of the beneficial “smaller is more ductile” size effect observed in metallic glass nanopillars. Compression experiments on Zr-Ni-Al metallic glass nanolattices reveal enhanced deformability as the nanolattice wall thickness is reduced and upon irradiation. This work points to metallic glass nanolattices as promising candidates for radiation-intensive applications and demonstrates that by fabricating the metallic glass in a nanolattice architecture the beneficial nanoscale size effect in deformability can be preserved.</p

3D nano-architected metallic glass: Size effect suppresses catastrophic failure

We investigate the mechanical behavior of 3D periodically architected metallic glass nanolattices, constructed from hollow beams of sputtered Zr-Ni-Al metallic glass. Nanolattices composed of beams with different wall thicknesses are fabricated by varying the sputter deposition time, resulting in nanolattices with median wall thicknesses of ∼88 nm, ∼57 nm, ∼38 nm, ∼30 nm, ∼20 nm, and ∼10 nm. Uniaxial compression experiments conducted inside a scanning electron microscope reveal a transition from brittle, catastrophic failure in thicker-walled nanolattices (median wall thicknesses of ∼88 and ∼57 nm) to deformable, gradual, layer-by-layer collapse in thinner-walled nanolattices (median wall thicknesses of ∼38 nm and less). As the nanolattice wall thickness is varied, large differences in deformability are manifested through the severity of strain bursts, nanolattice recovery after compression, and in-situ images obtained during compression experiments. We explain the brittle-to-deformable transition that occurs as the nanolattice wall thickness decreases in terms of the “smaller is more deformable” material size effect that arises in nano-sized metallic glasses. This work demonstrates that the nano-induced failure-suppression size effect that emerges in small-scale metallic glasses can be proliferated to larger-scale materials by the virtue of architecting

Effects of Helium Implantation on the Tensile Properties and Microstructure of Ni₇₃P₂₇ Metallic Glass Nanostructures

We report fabrication and nanomechanical tension experiments on as-fabricated and helium-implanted 130 nm diameter Ni₇₃P₂₇ metallic glass nanocylinders. The nanocylinders were fabricated by a templated electroplating process and implanted with He+ at energies of 50, 100, 150, and 200 keV to create a uniform helium concentration of 3 atom % throughout the nanocylinders. Transmission electron microscopy imaging and through-focus analysis reveal that the specimens contained 2 nm helium bubbles distributed uniformly throughout the nanocylinder volume. In situ tensile experiments indicate that helium-implanted specimens exhibit enhanced ductility as evidenced by a 2-fold increase in plastic strain over as-fabricated specimens with no sacrifice in yield and ultimate tensile strengths. This improvement in mechanical properties suggests that metallic glasses may actually exhibit a favorable response to high levels of helium implantation

Cross language priming extends to formulaic units: evidence from eye-tracking suggests that this idea “has legs”

Idiom priming effects (faster processing compared to novel phrases) are generally robust in native speakers but not non-native speakers. This leads to the question of how idioms and other multiword units are represented and accessed in a first (L1) and second language (L2). We address this by investigating the processing of translated Chinese idioms to determine whether known L1 combinations show idiom priming effects in non-native speakers when encountered in the L2. In two eye-tracking experiments we compared reading times for idioms vs. control phrases (Experiment 1) and for figurative vs. literal uses of idioms (Experiment 2). Native speakers of Chinese showed recognition of the L1 form in the L2, but figurative meanings were read more slowly than literal meanings, suggesting that the non-compositional nature of idioms makes them problematic in a non-native language. We discuss the results as they relate to crosslinguistic priming at the multiword level

Full-Stokes polarimetry with circularly polarized feeds - Sources with stable linear and circular polarization in the GHz regime

We present a pipeline that allows recovering reliable information for all four Stokes parameters with high accuracy. Its novelty relies on the treatment of the instrumental effects already prior to the computation of the Stokes parameters contrary to conventional methods, such as the M\"uller matrix one. The instrumental linear polarization is corrected across the whole telescope beam and significant Stokes $Q$ and $U$ can be recovered even when the recorded signals are severely corrupted. The accuracy we reach in terms of polarization degree is of the order of 0.1-0.2 %. The polarization angles are determined with an accuracy of almost 1$^{\circ}$. The presented methodology was applied to recover the linear and circular polarization of around 150 Active Galactic Nuclei. The sources were monitored from July 2010 to April 2016 with the Effelsberg 100-m telescope at 4.85 GHz and 8.35 GHz with a cadence of around 1.2 months. The polarized emission of the Moon was used to calibrate the polarization angle. Our analysis showed a small system-induced rotation of about 1$^{\circ}$ at both observing frequencies. Finally, we identify five sources with significant and stable linear polarization; three sources remain constantly linearly unpolarized over the period we examined; a total of 11 sources have stable circular polarization degree $m_\mathrm{c}$ and four of them with non-zero $m_\mathrm{c}$. We also identify eight sources that maintain a stable polarization angle over the examined period. All this is provided to the community for polarization observations reference. We finally show that our analysis method is conceptually different from the traditionally used ones and performs better than the M\"uller matrix method. Although it was developed for a system equipped with circularly polarized feeds it can easily be modified for systems with linearly polarized feeds as well.Comment: 19 pages, 17 figures, accepted for publication in Astronomy & Astrophysics on May 30, 201

The multifaceted role of curcumin in cancer prevention and treatment

Despite significant advances in treatment modalities over the last decade, neither the incidence of the disease nor the mortality due to cancer has altered in the last thirty years. Available anti-cancer drugs exhibit limited efficacy, associated with severe side effects, and are also expensive. Thus identification of pharmacological agents that do not have these disadvantages is required. Curcumin, a polyphenolic compound derived from turmeric (Curcumin longa), is one such agent that has been extensively studied over the last three to four decades for its potential anti-inflammatory and/or anti-cancer effects. Curcumin has been found to suppress initiation, progression, and metastasis of a variety of tumors. These anti-cancer effects are predominantly mediated through its negative regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other oncogenic molecules. It also abrogates proliferation of cancer cells by arresting them at different phases of the cell cycle and/or by inducing their apoptosis. The current review focuses on the diverse molecular targets modulated by curcumin that contribute to its efficacy against various human cancers

Novel curcumin- and emodin-related compounds identified by in silico 2D/3D conformer screening induce apoptosis in tumor cells

BACKGROUND: Inhibition of the COP9 signalosome (CSN) associated kinases CK2 and PKD by curcumin causes stabilization of the tumor suppressor p53. It has been shown that curcumin induces tumor cell death and apoptosis. Curcumin and emodin block the CSN-directed c-Jun signaling pathway, which results in diminished c-Jun steady state levels in HeLa cells. The aim of this work was to search for new CSN kinase inhibitors analogue to curcumin and emodin by means of an in silico screening method. METHODS: Here we present a novel method to identify efficient inhibitors of CSN-associated kinases. Using curcumin and emodin as lead structures an in silico screening with our in-house database containing more than 10(6 )structures was carried out. Thirty-five compounds were identified and further evaluated by the Lipinski's rule-of-five. Two groups of compounds can be clearly discriminated according to their structures: the curcumin-group and the emodin-group. The compounds were evaluated in in vitro kinase assays and in cell culture experiments. RESULTS: The data revealed 3 compounds of the curcumin-group (e.g. piceatannol) and 4 of the emodin-group (e.g. anthrachinone) as potent inhibitors of CSN-associated kinases. Identified agents increased p53 levels and induced apoptosis in tumor cells as determined by annexin V-FITC binding, DNA fragmentation and caspase activity assays. CONCLUSION: Our data demonstrate that the new in silico screening method is highly efficient for identifying potential anti-tumor drugs