High-pressure strengthening in ultrafine-grained metals.

The Hall-Petch relationship, according to which the strength of a metal increases as the grain size decreases, has been reported to break down at a critical grain size of around 10 to 15 nanometres1,2. As the grain size decreases beyond this point, the dominant mechanism of deformation switches from a dislocation-mediated process to grain boundary sliding, leading to material softening. In one previous approach, stabilization of grain boundaries through relaxation and molybdenum segregation was used to prevent this softening effect in nickel-molybdenum alloys with grain sizes below 10 nanometres3. Here we track in situ the yield stress and deformation texturing of pure nickel samples of various average grain sizes using a diamond anvil cell coupled with radial X-ray diffraction. Our high-pressure experiments reveal continuous strengthening in samples with grain sizes from 200 nanometres down to 3 nanometres, with the strengthening enhanced (rather than reduced) at grain sizes smaller than 20 nanometres. We achieve a yield strength of approximately 4.2 gigapascals in our 3-nanometre-grain-size samples, ten times stronger than that of a commercial nickel material. A maximum flow stress of 10.2 gigapascals is obtained in nickel of grain size 3 nanometres for the pressure range studied here. We see similar patterns of compression strengthening in gold and palladium samples down to the smallest grain sizes. Simulations and transmission electron microscopy reveal that the high strength observed in nickel of grain size 3 nanometres is caused by the superposition of strengthening mechanisms: both partial and full dislocation hardening plus suppression of grain boundary plasticity. These insights contribute to the ongoing search for ultrastrong metals via materials engineering.

Dual-phase nanostructuring as a route to high-strength magnesium alloys.

It is not easy to fabricate materials that exhibit their theoretical 'ideal' strength. Most methods of producing stronger materials are based on controlling defects to impede the motion of dislocations, but such methods have their limitations. For example, industrial single-phase nanocrystalline alloys and single-phase metallic glasses can be very strong, but they typically soften at relatively low strains (less than two per cent) because of, respectively, the reverse Hall-Petch effect and shear-band formation. Here we describe an approach that combines the strengthening benefits of nanocrystallinity with those of amorphization to produce a dual-phase material that exhibits near-ideal strength at room temperature and without sample size effects. Our magnesium-alloy system consists of nanocrystalline cores embedded in amorphous glassy shells, and the strength of the resulting dual-phase material is a near-ideal 3.3 gigapascals-making this the strongest magnesium-alloy thin film yet achieved. We propose a mechanism, supported by constitutive modelling, in which the crystalline phase (consisting of almost-dislocation-free grains of around six nanometres in diameter) blocks the propagation of localized shear bands when under strain; moreover, within any shear bands that do appear, embedded crystalline grains divide and rotate, contributing to hardening and countering the softening effect of the shear band.

Magnetic graphene oxide as adsorbent for the determination of polycyclic aromatic hydrocarbon metabolites in human urine.

Detection of monohydroxy polycyclic aromatic hydrocarbons metabolites in urine is an advisable and valid method to assess human environmental exposure to polycyclic aromatic hydrocarbons. In this work, novel Fe3O4/graphene oxide composites were prepared and their application in the magnetic solid-phase extraction of monohydroxy polycyclic aromatic hydrocarbons in urine was investigated by coupling with liquid chromatography and mass spectrometry. In the hybrid material, superparamagnetic Fe3O4 nanoparticles provide fast separation to simplify the analytical process and graphene oxide provides a large functional surface for the adsorption. The prepared magnetic nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry. The experimental conditions were optimized systematically. Under the optimal conditions, the recoveries of these compounds were in the range of 98.3-125.2%, the relative standard deviations ranged between 6.8 and 15.5%, and the limits of detection were in the range of 0.01-0.15 ng/mL. The simple, quick, and affordable method was successfully used in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities. The results indicated that the monohydroxy polycyclic aromatic hydrocarbons level in human urine can provide useful information for environmental exposure to polycyclic aromatic hydrocarbons.

Exploring the push-pull factors influencing parenting efficacy of fathers of children with ASD: a fuzzy set qualitative comparative analysis.

Objectives: This study aimed to explore the core factors and configurations influencing parenting efficacy for fathers of children with ASD in Western China by using a configuration analysis. Background: Understanding the push-pull factors related to parenting efficacy for fathers raising children with ASD can support the fathers of children with ASD to participate in education affairs and improve the quality of family education, which is of significant importance to both individuals and society. This study recruited 156 fathers of children with ASD from China. Results: The results suggested that there was more than one (sub) configuration for achieving a high level of parenting efficacy among fathers of children with ASD. (b) The configurations could be summarized into three main types as follows: "working within the system*flexible working time," "high level of education*high level of other support," and "severe disability*fewer interaction with wife." (c) The two variables, "family income" and "community support," were not as important as they were shown in previous studies, and their effects often depended on how they interact with other variables. Conclusions: Findings highlighted the validity of deploying configuration analysis (based on the ecosystem theory) to establish the relationship between independent variables and the parenting efficacy of fathers of children with ASD. The discovery of more than one configuration led to a new consensus on how multiple factors influence parenting efficacy. Implications were suggested for practitioners, policymakers, and future research alike.

A glycoside hydrolase 30 protein BpXynC of Bacillus paralicheniformis NMSW12 recognized as A MAMP triggers plant immunity response.

Bacillus spp. has been widely used as a biocontrol agent to control plant diseases. However, little is known about mechanisms of the protein MAMP secreted by Bacillus spp. Herein, our study reported a glycoside hydrolase family 30 (GH30) protein, BpXynC, produced by the biocontrol bacteria Bacillus paralicheniformis NMSW12, that can induce cell death in several plant species. The results revealed that the recombinant protein triggers cell death in Nicotiana benthamiana in a BAK1-dependent manner and elicits an early defense response, including ROS burst, activation of MAPK cascades, and upregulation of plant immunity marker genes. BpXynC was also found to be a glucuronoxylanase that exhibits hydrolysis activity on xlyan. Two mutants of BpXynC which lost the glucuronoxylanase activity still retained the elicitor activity. The qRT-PCR results of defense-related genes showed that BpXynC induces plant immunity responses via an SA-mediated pathway. BpXynC and its mutants could induce resistance in N. benthamiana against infection by Sclerotinia sclerotiorum and tobacco mosaic virus (TMV). Furthermore, BpXynC-treated tomato fruits exhibited strong resistance to the infection of Phytophthora capsica. Overall, our study revealed that GH30 protein BpXynC can induce plant immunity response as MAMP, which can be further applied as a biopesticide to control plant diseases.

Profiling of Antimicrobial Metabolites Synthesized by the Endophytic and Genetically Amenable Biocontrol Strain Bacillus velezensis DMW1.

The genus Bacillus is one of the most important genera for the biological control of plant diseases that are caused by various phytopathogens. The endophytic Bacillus strain DMW1 was isolated from the inner tissues of potato tubers and exhibited strong biocontrol activity. Based on its whole-genome sequence, DMW1 belongs to the Bacillus velezensis species, and it is similar to the model strain B. velezensis FZB42. 12 secondary metabolite biosynthetic gene clusters (BGCs), including two unknown function BGCs, were detected in the DMW1 genome. The strain was shown to be genetically amenable, and seven secondary metabolites acting antagonistically against plant pathogens were identified by a combined genetic and chemical approach. Strain DMW1 did significantly improve the growth of tomato and soybean seedlings, and it was able to control the Phytophthora sojae and Ralstonia solanacearum that were present in the plant seedlings. Due to these properties, the endophytic strain DMW1 appears to be a promising candidate for comparative investigations performed together with the Gram-positive model rhizobacterium FZB42, which is only able to colonize the rhizoplane. IMPORTANCE Phytopathogens are responsible for the wide spread of plant diseases as well as for great losses of crop yields. At present, the strategies used to control plant disease, including the development of resistant cultivars and chemical control, may become ineffective due to the adaptive evolution of pathogens. Therefore, the use of beneficial microorganisms to deal with plant diseases attracts great attention. In the present study, a new strain DMW1, belonging to the species B. velezensis, was discovered with outstanding biocontrol properties. It showed plant growth promotion and disease control abilities that are comparable with those of B. velezensis FZB42 under greenhouse conditions. According to a genomic analysis and a bioactive metabolites analysis, genes that are responsible for promoting plant growth were detected, and metabolites with different antagonistic activities were identified. Our data provide a basis for DMW1 to be further developed and applied as a biopesticide, which is similar to the closely related model strain FZB42.

degQ associated with the degS/degU two-component system regulates biofilm formation, antimicrobial metabolite production, and biocontrol activity in Bacillus velezensis DMW1.

The gram-positive bacterium Bacillus velezensis strain DMW1 produces a high level of antimicrobial metabolites that can suppress the growth of phytopathogens. We investigated the mechanism used by degQ and the degS/degU two-component system to regulate the biocontrol characteristics of DMW1. When degQ and degU were deleted, the biofilm formation, cell motility, colonization activities, and antifungal abilities of ΔdegQ and ΔdegU were significantly reduced compared to wild-type DMW1. The expression levels of biofilm-related genes (epsA, epsB, epsC, and tasA) and swarming-related genes (swrA and swrB) were all down-regulated. We also evaluated the impact on secondary metabolites of these two genes. The degQ and degU genes reduced surfactin and macrolactin production and up-regulated the production of fengycin, iturin, bacillaene, and difficidin metabolites. The reverse transcription-quantitative PCR results were consistent with these observations. Electrophoretic mobility shift assay and microscale thermophoresis revealed that DegU can bind to the promoter regions of these six antimicrobial metabolite genes and regulate their synthesis. In conclusion, we provided systematic evidence to demonstrate that the degQ and degU genes are important regulators of multicellular behaviour and antimicrobial metabolic processes in B. velezensis DMW1 and suggested novel amenable strains to be used for the industrial production of antimicrobial metabolites.

Graphene-Based Moisture Actuator with Oriented Microstructures Prepared by One-Step Laser Reduction for Accurately Controllable Responsive Direction and Position.

Actuators with fast and precise controllable responses are highly in demand for implementing agilely accurate mechanical movements in smart robots, intelligent sensors, biomimetic devices, and so on. Here, we report a graphene-based moisture actuator with accurately controllable direction and position responses achieved by a fast, controlled, and even programmable one-step laser reduction method. The laser reduction-induced oriented microstructures help to precisely guide the direction and location of the moisture response in graphene-based Janus films. The excellent moisture-mechanical response behaviors in these novel moisture actuators originate from the Janus structures and the periodic microstructures of a line-scanned layer. Our customized complex intelligent devices such as drums, bands, and three-dimensional wave humidity drives can highly match and verify the finite element simulations, which will inspire the creation of further smart robot designs for accurate deformation.

Characteristics of recombinant xylanase from camel rumen metagenome and its effects on wheat bran hydrolysis.

In the present study, we explored the effects of a novel xylanase from camel rumen metagenome (CrXyn) on wheat bran hydrolysis. CrXyn was heterologously expressed in Escherichia coli and showed maximum activity at 40 °C and pH 7.0. Furthermore, CrXyn exhibited preferential hydrolysis of xylan, but no obvious activity toward other substrates, including carboxymethylcellulose and Avicel. Using wheat straw xylan as a substrate, the Km and Vmax values for CrXyn were 5.98 g/L and 179.9 µmol xylose/min/mg protein, respectively. Mn2+ was a strong accelerator and significantly enhanced CrXyn activity. However, CrXyn activity was inhibited (~50 %) by 1 mM and 5 mM ethylenediaminetetraacetic acid (EDTA) and completely inactivated by 5 mM Cu2+. CrXyn tolerated 5 mM sodium dodecyl sulphate (SDS) and 15 % methanol, ethanol, and dimethyl sulfoxide (DMSO), with >50 % residual activity. CrXyn effectively hydrolyzed wheat bran, with xylobiose and xylotetraose accounting for 79.1 % of total sugars produced. A remarkable synergistic effect was found between CrXyn and protease, leading to an obvious increase in amino acids released from wheat bran compared with the control. CrXyn also enhanced the in vitro hydrolysis of wheat bran. Thus, CrXyn exhibits great potential as a feed additive to improve the utilization of wheat bran in monogastric animal production.

Bio-Inspired High Sensitivity of Moisture-Mechanical GO Films with Period-Gradient Structures.

Moisture actuators can accomplish humidity-triggered energy-conversion process, through material screening and structural design. Inspired by natural caterpillars and the hydrophilic properties of graphene oxide (GO), this work proposes a geometrical design of period-gradient structures in GO films for fabricating moisture actuators. These novel period-gradient-structured GO films exhibit excellent dynamic performance that they could deform at 1000° with a small radius in several seconds at a high relative humidity (RH ≈ 80%). The properties of fast actuating speed and high response to deformation are achieved through the structural designing of the sole GO film by a one-step formation process. A mechanics-based theoretical model combined with the finite element simulation is presented to demonstrate the actuating mechanism in geometry, moisture, and mechanics, which lays the foundation for potential applications of GO films in remote control, environmental monitoring, and man-machine interactions.

In situ growth of ZIF-8-derived ternary ZnO/ZnCo2O4/NiO for high performance asymmetric supercapacitors.

In this paper, the rational design and synthesis of ZIF-8-derived ternary ZnO/ZnCo2O4/NiO wrapped by nanosheets is introduced. Polyhedral ternary ZnO/ZnCo2O4/NiO composites surrounded by nanosheets with different compositions are successfully fabricated through in situ growth on ZIF-8 templates and subsequent thermal annealing in air. Electrochemical investigation reveals that when the molar ratio of nickel nitrate to cobalt nitrate is 1, the composite material is more outstanding, which shows a high specific capacitance of 1136.4 F g-1 at 1 A g-1 and excellent cycling stability of 86.54% after 5000 cycles. Moreover, the excellent performance of this material is also confirmed by assembling an asymmetric supercapacitor. The assembled hybrid device can reach a large potential range of 0-1.6 V and deliver a high energy density of 46.04 W h kg-1 as well as the maximum power density of 7987.5 W kg-1.

Nature-Inspired Hierarchical Steels.

Materials can be made strong, but as such they are often brittle and prone to fracture when under stress. Inspired by the exceptionally strong and ductile structure of byssal threads found in certain mussels, we have designed and manufactured a multi-hierarchical steel, based on an inexpensive austenitic stainless steel, which defeats this "conflict" by possessing both superior strength and ductility. These excellent mechanical properties are realized by structurally introducing sandwich structures at both the macro- and nano-scales, the latter via an isometric, alternating, dual-phase crystal phases comprising nano-band austenite and nano-lamellar martensite, without change in chemical composition. Our experiments (transmission and scanning electron microscopy, electron back-scattered diffraction, nano-indentation and tensile tests) and micromechanics simulation results reveal a synergy of mechanisms underlying such exceptional properties. This synergy is key to the development of vastly superior mechanical properties, and may provide a unique strategy for the future development of new super strong and tough (damage-tolerant), lightweight and inexpensive structural materials.

Gradient learning algorithms for ontology computing.

The gradient learning model has been raising great attention in view of its promising perspectives for applications in statistics, data dimensionality reducing, and other specific fields. In this paper, we raise a new gradient learning model for ontology similarity measuring and ontology mapping in multidividing setting. The sample error in this setting is given by virtue of the hypothesis space and the trick of ontology dividing operator. Finally, two experiments presented on plant and humanoid robotics field verify the efficiency of the new computation model for ontology similarity measure and ontology mapping applications in multidividing setting.

Bifunctional magnetic nanoparticles for analysis of aldehyde metabolites in exhaled breath of lung cancer patients.

We report here the preparation of dual-functionalized magnetic nanoparticles, with the nanoparticles as extraction sorbents, a magnetic solid phase extraction method was developed and applied for the analysis of trace amount of aldehydes in human exhaled breath condensate. In the material, octyl-functionalized internal surface provided hydrophobic groups for extraction, non-ionic surfactant (Tween-20)-coated outer surface offered hydrophilic network structure to prevent the access of macromolecules, strong magnetic property of nanoparticles simplified the analytical procedure. The experimental results showed that the prepared nanoparticles exhibited good dispersibility in aqueous solution and excellent extraction efficiency toward aldehydes. Six aldehydes were derivatized with 2,4-dinitrophenylhydrazine and then the formed hydrazones were extracted by the nanoparticles and analyzed by high-performance liquid chromatography-photo diode array detector. Under the optimal conditions, the method provided low limits of detection (2.9-21.5 nmol L(-1)), satisfactory reproducibility (relative standard deviations, 2.9-13.1%) and acceptable recoveries (73.7-133.1%). The developed method was applied successfully to determine the aldehydes metabolites in the exhaled breath condensate samples of healthy people and lung cancer patients. The dual-functionalized material is suitable for biological sample analysis. The proposed method provides an alternative approach for quantification of aldehyde metabolites in complex biological samples.

NO treated TiO2 as an efficient visible light photocatalyst for NO removal.

In this study, we report that nitrogen doped TiO(2) could be achieved via thermal treatment of Degussa P25 TiO(2) in NO atmosphere directly (P25-NO). The samples were characterized with XRD, XPS, and FT-IR. The characterization results suggested that nitrogen species were interstitially doped in P25-NO during the NO thermal treatment process. In comparison with P25, the P25-NO exhibited significantly enhanced photocatalytic activities under visible light irradiation (λ>420 nm) for gaseous NO removal. On the basis of electronic band structure theory, we proposed a possible mechanism for the enhanced visible light driven photocatalytic oxidation process over the interstitial N doping P25-NO samples. This work could not only deepen understanding of the enhanced photoactivity originated from interstitial N doping in TiO(2), but also provide a facile route to prepare nitrogen doped TiO(2) for environmental and energy applications.