Strain-hardening (the increase of flow stress with plastic strain) is the most important phenomenon in the mechanical behaviour of engineering alloys because it ensures that flow is delocalized, ...enhances tensile ductility and inhibits catastrophic mechanical failure
. Metallic glasses (MGs) lack the crystallinity of conventional engineering alloys, and some of their properties-such as higher yield stress and elastic strain limit
-are greatly improved relative to their crystalline counterparts. MGs can have high fracture toughness and have the highest known 'damage tolerance' (defined as the product of yield stress and fracture toughness)
among all structural materials. However, the use of MGs in structural applications is largely limited by the fact that they show strain-softening instead of strain-hardening; this leads to extreme localization of plastic flow in shear bands, and is associated with early catastrophic failure in tension. Although rejuvenation of an MG (raising its energy to values that are typical of glass formation at a higher cooling rate) lowers its yield stress, which might enable strain-hardening
, it is unclear whether sufficient rejuvenation can be achieved in bulk samples while retaining their glassy structure. Here we show that plastic deformation under triaxial compression at room temperature can rejuvenate bulk MG samples sufficiently to enable strain-hardening through a mechanism that has not been previously observed in the metallic state. This transformed behaviour suppresses shear-banding in bulk samples in normal uniaxial (tensile or compressive) tests, prevents catastrophic failure and leads to higher ultimate flow stress. The rejuvenated MGs are stable at room temperature and show exceptionally efficient strain-hardening, greatly increasing their potential use in structural applications.
An ultimate goal of spintronics is to control magnetism via electrical means. One promising way is to utilize a current-induced spin-orbit torque (SOT) originating from the strong spin-orbit coupling ...in heavy metals and their interfaces to switch a single perpendicularly magnetized ferromagnetic layer at room temperature. However, experimental realization of SOT switching to date requires an additional in-plane magnetic field, or other more complex measures, thus severely limiting its prospects. Here we present a novel structure consisting of two heavy metals that delivers competing spin currents of opposite spin indices. Instead of just canceling the pure spin current and the associated SOTs as one expects and corroborated by the widely accepted SOTs, such devices manifest the ability to switch the perpendicular CoFeB magnetization solely with an in-plane current without any magnetic field. Magnetic domain imaging reveals selective asymmetrical domain wall motion under a current. Our discovery not only paves the way for the application of SOT in nonvolatile technologies, but also poses questions on the underlying mechanism of the commonly believed SOT-induced switching phenomenon.
The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator, but even if the light field has no thermal component, shot noise still sets a limit on the ...minimum phonon occupation. In optomechanical sideband cooling in a cavity, the finite off-resonant Stokes scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work, we sideband cool a micromechanical membrane resonator to the quantum backaction limit. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath. This level of optomechanical coupling that overwhelms the intrinsic thermal decoherence was not reached in previous ground-state cooling demonstrations.
Abstract
Motivation
Peptide is a promising candidate for therapeutic and diagnostic development due to its great physiological versatility and structural simplicity. Thus, identifying therapeutic ...peptides and investigating their properties are fundamentally important. As an inexpensive and fast approach, machine learning-based predictors have shown their strength in therapeutic peptide identification due to excellences in massive data processing. To date, no reported therapeutic peptide predictor can perform high-quality generic prediction and informative physicochemical properties (IPPs) identification simultaneously.
Results
In this work, Physicochemical Property-based Therapeutic Peptide Predictor (PPTPP), a Random Forest-based prediction method was presented to address this issue. A novel feature encoding and learning scheme were initiated to produce and rank physicochemical property-related features. Besides being capable of predicting multiple therapeutics peptides with high comparability to established predictors, the presented method is also able to identify peptides’ informative IPP. Results presented in this work not only illustrated the soundness of its working capacity but also demonstrated its potential for investigating other therapeutic peptides.
Availability and implementation
https://github.com/YPZ858/PPTPP.
Supplementary information
Supplementary data are available at Bioinformatics online.
In this work, we compare the resolution of V2-V3 and V3-V4 16S rRNA regions for the purposes of estimating microbial community diversity using paired-end Illumina MiSeq reads, and show that the ...fragment, including V2 and V3 regions, has higher resolution for lower-rank taxa (genera and species). It allows for a more precise distance-based clustering of reads into species-level OTUs. Statistically convergent estimates of the diversity of major species (defined as those that together are covered by 95% of reads) can be achieved at the sample sizes of 10000 to 15000 reads. The relative error of the Shannon index estimate for this condition is lower than 4%.
Illuminating gravitational waves Kasliwal, M. M.; Nakar, E.; Singer, L. P. ...
Science (American Association for the Advancement of Science),
12/2017, Letnik:
358, Številka:
6370
Journal Article
Recenzirano
Odprti dostop
Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic ...counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.
We report observations of superradiance for atoms trapped in the near field of a photonic crystal waveguide (PCW). By fabricating the PCW with a band edge near the D(1) transition of atomic cesium, ...strong interaction is achieved between trapped atoms and guided-mode photons. Following short-pulse excitation, we record the decay of guided-mode emission and find a superradiant emission rate scaling as Γ̅(SR)∝N̅Γ(1D) for average atom number 0.19≲N̅≲2.6 atoms, where Γ(1D)/Γ'=1.0±0.1 is the peak single-atom radiative decay rate into the PCW guided mode, and Γ' is the radiative decay rate into all the other channels. These advances provide new tools for investigations of photon-mediated atom-atom interactions in the many-body regime.
Heat processing has been used to improve protein utilization and availability of animal nutrition. However, to date, few studies exist on heat-induced protein molecular structure changes on a ...molecular basis. The aims of this study were to use molecular spectroscopy as a novel approach to determine heat-induced protein molecular structure changes affected by moist and dry heating and quantify protein molecular structures and nutritive value in the rumen and intestine in dairy cattle. In this study, soybean was used as a model for feed protein and was autoclaved at 120°C for 1h (moist heating) and dry heated at 120°C for 1h. The parameters assessed in this study included protein structure α-helix and β-sheet and their ratio, protein subfractions associated with protein degradation behaviors, intestinal protein availability, and energy values. The results show that heat treatments changed the protein molecular structure. Both dry and moist heating increased the amide I-to-amide II ratio. However, for the protein α-helix-to-β-sheet ratio, moist heating decreased but dry heating increased the ratio. Compared with dry heating, moist heating dramatically changed the chemical and nutrient profiles of soybean seed. It greatly decreased soluble crude protein, nonprotein nitrogen, and increased neutral detergent insoluble protein. Both dry and moist heating treatments did not alter digestible nutrients and energy values. Heating tended to decrease the nonprotein nitrogen fraction (soluble and rapidly degradable protein fraction) and true protein 1 fraction (fast-degradable protein fraction). Conversely, the true protein 3 fraction (slowly degradable fraction) significantly increased. The in situ rumen study showed that moist heating decreased protein rumen degradability and increased intestinal digestibility of rumen-undegradable protein. Compared with the raw soybeans, dry heating did not affect rumen degradability and intestinal digestibility. In conclusion, compared with dry heating, moist heating dramatically affected the nutrient profile, protein subfractions, rumen degradability, intestinal digestibility, and protein molecular structure (amide I-to-II ratio; α-helix-to-β-sheet ratio). The sensitivity of soybean seed to moist heating was much higher than that to dry heating in terms of the structure and nutrient profile changes.
Semiconductor nanowires with proximity-induced superconductivity are leading contenders for manifesting Majorana fermions in condensed matter1–5. However, unambiguous detection of these ...quasiparticles is controversial6, and one proposed method is to show that the peak in the conductance at zero applied bias is quantized to the value of 2e2/h (refs. 7–10). This has been reported previously11, but only by probing one end of the device. Yet, if peaks come from Majorana modes, they should be observed at both ends simultaneously. Here we fabricate devices that feature tunnel probes on both ends of a nanowire and observe peaks that are close to the quantized value. These peaks evolve with the tunnel barrier strength and magnetic field in a way that is consistent with Majorana zero modes. However, we only find nearly quantized zero-bias peaks localized to one end of the nanowire, while conductance dips are observed for the same parameters at the other end. We also identify delocalized states near zero magnetic field and at higher electron density, which is not in the basic Majorana regime. These results enable us to lay out procedures for assessing the non-locality of subgap wavefunctions and provide a classification of nanowire bound states based on their localization.Majorana bound states should appear at both ends of a nanowire if it is in the topological regime. This paper reports that, in many cases, zero-bias conduction peaks only occur on one end of the wire, which casts doubt on whether they are Majoranas.
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