Unlike the well-defined long-range periodic order that characterizes crystals, so far the inherent atomic packing mode in glassy solids remains mysterious. Based on molecular dynamics simulations, ...here we find medium-range atomic packing orders in metallic glasses, which are hidden in the diffraction data in terms of structure factors or pair correlation functions. The analysis of the hidden orders in various metallic glasses indicates that the glassy and crystalline solids share a nontrivial structural homology in short-to-medium range, and the hidden orders are formulated by inheriting partial crystalline orders during glass formation. As the number of chemical components increases, more hidden orders are often developed in a metallic glass and entangled topologically. We use this phenomenon to explain the geometric frustration in glass formation and the glass-forming ability of metallic alloys.
Close white dwarf binaries consisting of a white dwarf and an A-, F-, G-, or K-type main-sequence star, henceforth close WD+AFGK binaries, are ideal systems to understand the nature of type Ia ...supernovae progenitors and to test binary evolution models. In this work we identify 775 WD+AFGK candidates from TGAS (The Tycho-Gaia Astrometric Solution) and Gaia Data Release 2 (DR2), a well-defined sample of stars with available parallaxes, and we measure radial velocities (RVs) for 275 of them with the aim of identifying close binaries. The RVs have been measured from high-resolution spectra obtained at the Xinglong 2.16 m Telescope and the San Pedro Mártir 2.12 m Telescope and/or from available LAMOST DR6 (low-resolution) and RAVE DR5 (medium-resolution) spectra. We identify 23 WD+AFGK systems displaying more than 3 RV variation among 151 systems for which the measured values are obtained from different nights. Our WD+AFGK binary sample contains both AFGK dwarfs and giants, with a giant fraction ∼43%. The close binary fractions we determine for the WD+AFGK dwarf and giant samples are 24% and 15%, respectively. We also determine the stellar parameters (i.e., effective temperature, surface gravity, metallicity, mass, and radius) of the AFGK companions with available high-resolution spectra. The stellar parameter distributions of the AFGK companions that are members of close and wide binary candidates do not show statistically significant differences.
We have recently identified and characterized a novel oncogene, maelstrom (MAEL) from 1q24, in the pathogenesis of hepatocellular carcinoma. In this study, MAEL was investigated for its oncogenic ...role in urothelial carcinoma of the bladder (UCB) tumorigenesis/aggressiveness and underlying molecular mechanisms. Here, we report that overexpression of MAEL in UCB is important in the acquisition of an aggressive and/or poor prognostic phenotype. In UCB cell lines, knockdown of MAEL by short hairpin RNA is sufficient to inhibit cell growth, invasiveness/metastasis and suppressed epithelial-mesenchymal transition (EMT), whereas ectopic overexpression of MAEL promoted cell growth, invasive and/or metastatic capacity and enhanced EMT both in vitro and in vivo. We further demonstrate that MAEL could induce UCB cell EMT by downregulating a critical downstream target, the metastasis suppressor 1 (MTSS1) gene, ultimately leading to an increased invasiveness of cancer cells. Notably, overexpression of MAEL in UCB cells substantially enhanced the enrichment of DNA methyltrans-ferase (DNMT)3B and histone deacetylase (HDAC)1/2 on the promoter of the MTSS1, and thereby epigenetically suppressing the MTSS1 transcription. Downregulation of MTSS1 by MAEL in UCB cells is partially dependent on DNMT3B. Furthermore, we identify that beside the gene amplification of MAEL, miR-186 is a key negative regulator of MAEL and downregulation of miR-186 is another important mechanism for MAEL overexpression in UCBs. These data suggest that overexpression of MAEL, caused by gene amplification and/or decreased miR-186, has a critical oncogenic role in UCB pathogenesis by downregulation of MTSS1, and MAEL could be used as a novel prognostic marker and/or effective therapeutic target for human UCB.
The properties of quantum materials are commonly tuned using experimental variables such as pressure, magnetic field and doping. Here we explore a different approach using irreversible, plastic ...deformation of single crystals. We show that compressive plastic deformation induces low-dimensional superconductivity well above the superconducting transition temperature (T
) of undeformed SrTiO
, with evidence of possible superconducting correlations at temperatures two orders of magnitude above the bulk T
. The enhanced superconductivity is correlated with the appearance of self-organized dislocation structures, as revealed by diffuse neutron and X-ray scattering. We also observe deformation-induced signatures of quantum-critical ferroelectric fluctuations and inhomogeneous ferroelectric order using Raman scattering. Our results suggest that strain surrounding the self-organized dislocation structures induces local ferroelectricity and quantum-critical dynamics that strongly influence T
, consistent with a theory of superconductivity enhanced by soft polar fluctuations. Our results demonstrate the potential of plastic deformation and dislocation engineering for the manipulation of electronic properties of quantum materials.
There is an increasing demand for ultrahigh-strength ferritic steels strengthened by nanoprecipitates. Improvement of the precipitation strengthening response requires an understanding of the ...nanoscale precipitation mechanisms. In this study, the synergistic effects of Cu and Ni on nanoscale precipitation and mechanical properties of ferritic steels were thoroughly investigated, and new steels with ultrahigh strength and high ductility have been developed. Our results indicate that Ni effectively increases the number density of Cu-rich nanoprecipitates by more than an order of magnitude, leading to a substantial increase in yield strength. It appears that Ni decreases both the strain energy for nucleation and the interfacial energy between the nucleus and the matrix, thereby decreasing the critical energy for nucleation of Cu-rich nanoprecipitates. Cu and Ni are also found to be beneficial to grain-size refinement, resulting from lowering the austenite-to-ferrite transformation temperature, as determined from thermodynamic calculations. In addition, the strengthening mechanisms of Cu and Ni were quantitatively evaluated in terms of precipitation strengthening, grain refinement strengthening and solid-solution strengthening. The current findings shed light on the composition–microstructure–property relationships in nanoprecipitate-strengthened ferritic steels.
Abstract
Lower hybrid drift waves are commonly observed at plasma boundaries, playing an important role in plasma dynamics. Such waves have been widely investigated in the terrestrial magnetosphere ...but have never been reported in other planetary environments. Here, using the measurements from the Mars Atmosphere and Volatile EvolutioN mission, we present the first observation of electromagnetic lower hybrid drift waves at the edge of the current sheet on the dusk side of the Martian magnetotail, which should be locally excited rather than propagated from other regions. These plasma waves are associated with significant density gradients and magnetic field gradients. Based on the measured local plasma parameters and the sufficient condition for lower hybrid drift instability to be excited, we find that the proton density gradient is sharp enough to excite the lower hybrid drift instability. The analysis of the existence condition for lower hybrid drift instability indicates that these lower hybrid drift waves at the edge of the current sheet are generated through lower hybrid drift instability. The above results can improve our understanding of Mars’ magnetospheric dynamics.
The extracellular signal-regulated kinase (ERK) is one of the three major types of mitogen-activated protein kinases. Previous studies showed that ERKs mediate various signaling pathways for cell ...proliferation, differentiation, survival and transformation in mammals. In the present study, we use goldfish as a model system and demonstrate that ERK kinases play important roles in promoting embryonic survival and regulate development of eye and trunk in vertebrates. ERKs are highly expressed in multiple tissues including lens epithelial cells, lens fiber cells, retina, brain, muscle and heart of adult goldfish. Injection of the dominant negative ERK mutant (DNM-ERK) into the fertilized eggs of goldfish significantly inhibited ERK activity at blastula stage, and completely blocked ERK activity at gastrula and later stages. As a result, the blastula cells were induced into apoptosis, and majority of the injected embryos were lethal at embryonic stages. At the molecular level, inhibition of ERK activity by DNM-ERKs suppressed phosphorylation of Bad at Ser-112 to promote apoptosis. Similar results were observed when MEK activity was inhibited by U0126 treatment. The survived embryos display significant abnormality in the phenotypes of both eye and trunk. Associated with the abnormality in the eye development, phosphorylation in Pax-6 and expression of HSF4 were significantly decreased and expression of the β-crystallin gene was also downregulated. These results provide novel information regarding the roles of ERKs in regulating vertebrate development.
ABSTRACT
High time resolution and accuracy are of critical importance in the studies of timing analysis and time delay localization of gamma-ray bursts (GRBs), soft gamma-ray repeaters (SGRs) and ...pulsars. The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) consisting of two micro-satellites, GECAM-A and GECAM-B, launched on 2020 December 10, is aimed at monitoring and locating X-ray and GRBs all over the sky. To achieve its scientific goals, GECAM is designed to have the highest time resolution (0.1 $\mu {\rm s}$) among all GRB detectors ever flown. Here, we make a comprehensive time calibration campaign including both on-ground and on-orbit tests to derive not only the relative time accuracy of GECAM satellites and detectors, but also the absolute time accuracy of GECAM-B. Using the on-ground calibration with a $\rm ^{22}Na$ radioactive source, we find that the relative time accuracy between GECAM-A and GECAM-B is about 0.15 $\mu {\rm s}$ (1σ). To measure the relative time accuracy between all detectors of a single GECAM satellite, cosmic-ray events detected on orbit are utilized since they could produce many secondary particles simultaneously record by multiple detectors. We find that the relative time accuracy among all detectors onboard GECAM-B is about 0.12 $\mu {\rm s}$ (1σ). Finally, we use the novel Li-CCF method to perform the absolute time calibration with Crab pulsar and SGR J1935+2154, both of which were jointly observed by GECAM-B and Fermi/GBM, and obtain that the time difference between GECAM-B and Fermi/GBM is 3.06 ± 6.04 $\mu {\rm s}$ (1σ).
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