Ultrastrong and Deformable Aluminum-Based Composite Nanolaminates with Transformable Binary Intergranular Films.

Nanostructured metals with conventional grain boundaries or interfaces exhibit high strength yet usually poor ductility. Here we report an interface engineering strategy that breaks the strength-ductility dilemma via externally incorporating graphene oxide at lamella boundaries of aluminum (Al) nanolaminates. By forming the binary intergranular films where graphene oxide was sandwiched between two amorphous alumina layers, the Al-based composite nanolaminates achieved ultrahigh compressive strength (over 1 GPa) while retaining excellent plastic deformability. Complementing experimental results with molecular dynamics simulation efforts, the ultrahigh strength was interpreted by the strong blocking effect of the binary intergranular films on dislocation nucleation and propagation, and the excellent plasticity was found to originate from the stress/strain-induced crystalline-to-amorphous transition of graphene oxide and the synergistic deformation between Al nanolamellas and the binary intergranular films.

Multiplex Detection of Foodborne Pathogens using 3D Nanostructure Swab and Deep Learning-Based Classification of Raman Spectra.

Proactive management of foodborne illness requires routine surveillance of foodborne pathogens, which requires developing simple, rapid, and sensitive detection methods. Here, a strategy is presented that enables the detection of multiple foodborne bacteria using a 3D nanostructure swab and deep learning-based Raman signal classification. The nanostructure swab efficiently captures foodborne pathogens, and the portable Raman instrument directly collects the Raman signals of captured bacteria. a deep learning algorithm has been demonstrated, 1D convolutional neural network with binary labeling, achieves superior performance in classifying individual bacterial species. This methodology has been extended to mixed bacterial populations, maintaining accuracy close to 100%. In addition, the gradient-weighted class activation mapping method is used to provide an investigation of the Raman bands for foodborne pathogens. For practical application, blind tests are conducted on contaminated kitchen utensils and foods. The proposed technique is validated by the successful detection of bacterial species from the contaminated surfaces. The use of a 3D nanostructure swab, portable Raman device, and deep learning-based classification provides a powerful tool for rapid identification (≈5 min) of foodborne bacterial species. The detection strategy shows significant potential for reliable food safety monitoring, making a meaningful contribution to public health and the food industry.

Direct Observation of Three-Dimensional Atomic Structure of Twinned Metallic Nanoparticles and Their Catalytic Properties.

We determined a full 3D atomic structure of a dumbbell-shaped Pt nanoparticle formed by a coalescence of two nanoclusters using deep learning assisted atomic electron tomography. Formation of a double twin boundary was clearly observed at the interface, while substantial anisotropy and disorder were also found throughout the nanodumbbell. This suggests that the diffusion of interfacial atoms mainly governed the coalescence process, but other dynamic processes such as surface restructuring and plastic deformation were also involved. A full 3D strain tensor was clearly mapped, which allows direct calculation of the oxygen reduction reaction activity at the surface. Strong tensile strain was found at the protruded region of the nanodumbbell, which results in an improved catalytic activity on {100} facets. This work provides important clues regarding the coalescence mechanism and the relation between the atomic structure and catalytic property at the single-atom level.

A Study on Dislocation Mechanisms of Toughening in Cu-Graphene Nanolayered Composite.

We investigated the role of graphene interfaces in strengthening and toughening of the Cu-graphene nanocomposite by a combination of in situ transmission electron microscopy (TEM) deformation and molecular dynamics (MD) simulations. In situ TEM directly showed that dislocation plasticity is strongly confined within single Cu grains by the graphene interfaces and grain boundaries. The weak Cu-graphene interfacial bonding induces stress decoupling, which results in independent plastic deformation of each Cu layer. As confirmed by the MD simulation, the localized deformation made by such constrained dislocation plasticity results in the nucleation and growth of voids at the graphene interface, which acts as a precursor for crack. The graphene interfaces also effectively block crack propagation promoted by easy delamination of Cu layers dissipating the elastic strain energy. The toughening mechanisms revealed by the present study will provide valuable insights into the optimization of the mechanical properties of metal-graphene nanolayered composites.

Mechanical Robustness of Metal Nanocomposites Rendered by Graphene Functionalization.

Nanocarbon materials, such as graphene, carbon nanotubes, and their derivatives, are considered highly effective reinforcing agents in metals. Copious experimental and computational observations suggest that the nature of the interfaces may significantly affect the mechanical behavior of nanocarbon-metal composites, while the exact correlation between the interfacial structure and the deformation and failure mechanisms of the composite remains elusive. Using a nanolaminated graphene-aluminum (Al) composite as the model material, we designed and created composites with distinct interfacial structures and bonding states via graphene functionalization. The mechanical behavior of the composites was strongly affected by the structure of the functionalized graphene (FG)/Al interface, and the optimum strength-ductility synergy came from the composite with the intermediate extent of functionalization. Complementing experimental results with molecular dynamics and phase-field simulation efforts, we interpreted these results by the combined effects of the intrinsic strength of FG nanosheets and the FG/Al interfacial bonding state.

Simple and Multiplexed Detection of Nucleic Acid Targets Based on Fluorescent Ring Patterns and Deep Learning Analysis.

Simple diagnostic tests for nucleic acid targets can provide great advantages for applications such as rapid pathogen detection. Here, we developed a membrane assay for multiplexed detection of nucleic acid targets based on the visualization of two-dimensional fluorescent ring patterns. A droplet of the assay solution is applied to a cellulose nitrate membrane, and upon radial chromatographic flow and evaporation of the solvent, fluorescent patterns appear under UV irradiation. The target nucleic acid is isothermally amplified and is immediately hybridized with fluorescent oligonucleotide probes in a one-pot reaction. We established the fluorescent ring assay integrated with isothermal amplification (iFluor-RFA = isothermal fluorescent ring-based radial flow assay), and feasibility was tested using nucleic acid targets of the receptor binding domain (RBD) and RNA-dependent RNA polymerase (RdRp) genes of SARS-CoV-2. We demonstrate that the iFluor-RFA method is capable of specific and sensitive detection in the subpicomole range, as well as multiplexed detection even in complex solutions. Furthermore, we applied deep learning analysis of the fluorescence images, showing that patterns could be classified as positive or negative and that quantitative amounts of the target could be predicted. The current technique, which is a membrane pattern-based nucleic acid assay combined with deep learning analysis, provides a novel approach in diagnostic platform development that can be versatilely applied for the rapid detection of infectious pathogens.

Direct strain correlations at the single-atom level in three-dimensional core-shell interface structures.

Nanomaterials with core-shell architectures are prominent examples of strain-engineered materials. The lattice mismatch between the core and shell materials can cause strong interface strain, which affects the surface structures. Therefore, surface functional properties such as catalytic activities can be designed by fine-tuning the misfit strain at the interface. To precisely control the core-shell effect, it is essential to understand how the surface and interface strains are related at the atomic scale. Here, we elucidate the surface-interface strain relations by determining the full 3D atomic structure of Pd@Pt core-shell nanoparticles at the single-atom level via atomic electron tomography. Full 3D displacement fields and strain profiles of core-shell nanoparticles were obtained, which revealed a direct correlation between the surface and interface strain. The strain distributions show a strong shape-dependent anisotropy, whose nature was further corroborated by molecular statics simulations. From the observed surface strains, the surface oxygen reduction reaction activities were predicted. These findings give a deep understanding of structure-property relationships in strain-engineerable core-shell systems, which can lead to direct control over the resulting catalytic properties.

Foliar-Applied Glutathione Mitigates Cadmium-Induced Oxidative Stress by Modulating Antioxidant-Scavenging, Redox-Regulating, and Hormone-Balancing Systems in Brassica napus.

The antioxidant glutathione (GSH) mitigates adverse physio-metabolic effects and defends against abiotic types of stress, such as cadmium (Cd) stress. However, its function and role in resisting Cd phytotoxicity by leveraging plant antioxidant-scavenging, redox-regulating, and hormone-balancing systems have not been comprehensively and systematically demonstrated in the Cd-hyperaccumulating plant Brassica napus L. cv. Tammi (oilseed rape). In this study, the effects of exogenously applied GSH to the leaves of B. napus seedlings exposed to Cd (10 µM) were investigated. As a result, Cd stress alone significantly inhibited growth and increased the levels of reactive oxygen species (ROS) and the bioaccumulation of Cd in the seedlings compared with those in unstressed controls. Furthermore, Cd stress induced an imbalance in plant stress hormone levels and decreases in endogenous GSH levels and GSH redox ratios, which were correlated with reductions in ascorbate (AsA) and/or nicotinamide adenine dinucleotide phosphate (NADPH) redox states. However, the exogenous application of GSH to Cd-stressed B. napus seedlings reduced Cd-induced ROS levels and enhanced antioxidant-scavenging defenses and redox regulation by both increasing seedling AsA, GSH, and NADPH concentrations and rebalancing stress hormones, thereby enhancing Cd uptake and accumulation. These results demonstrate that GSH improved plant redox status by upregulating the AsA-GSH-NADPH cycle and reestablishing normal hormonal balance. This indicates that exogenously applied GSH can mitigate Cd phytotoxicity in B. napus and possibly other plants. Therefore, GSH can potentially be applied to Cd-polluted soil for plant remediation.

First-principles study of the ternary effects on the plasticity of [Formula: see text]-TiAl crystals.

We studied the effects of important ternary elements, such as Cr, Nb, and V, on the plasticity of [Formula: see text]-TiAl crystals by calculating the point defect formation energy and the change in the generalized stacking fault energy (GSFE) surface from first-principles calculations. For all three elements, the point defect formation energies of the substitutional defects are lower in the Ti site than in the Al site, which implies that substitution on the Ti site is energetically more stable. We computed the GSFE surfaces with and without a substitutional solute and obtained the ideal critical resolved shear stress (ICRSS) of each partial slip. The change in the GSFE surface indicates that the substitution of Ti with Cr, Nb, or V results in an increase in the yield strength because the ICRSS of the superlattice intrinsic stacking fault (SISF) partial slip increases. Interestingly, we find that Cr substitution on an Al site could occur owing to the small difference between the substitutional defect formation energies of the Ti and Al sites. In that case, the reduction of ICRSSs of the SISF partial slip and twinning would lead to improved twinnability. We discuss the implications of the computational predictions by comparing them with experimental results in the literature.

Ascorbate-Mediated Modulation of Cadmium Stress Responses: Reactive Oxygen Species and Redox Status in Brassica napus.

The role of ascorbate (AsA) in antioxidant defense system-associated resistance to cadmium (Cd) in oilseed rape plants has not yet been clearly demonstrated. The present study investigated the critical role of exogenous AsA on the physiological and biochemical responses of reactive oxygen species (ROS) and antioxidant scavenging defense systems in oilseed rape (Brassica napus L. cv. Tammi) seedlings exposed to Cd. Cd (10 µM) treatment led to significant reductions in plant growth; increases in the levels of superoxide anion radical, hydrogen peroxide, and malondialdehyde; and increases in Cd uptake and accumulation by the roots and shoots in hydroponically grown 10-day-old seedlings. Moreover, it reduced AsA content and AsA redox ratios, which have been correlated with reductions in glutathione (GSH) and/or nicotinamide adenine dinucleotide phosphate (NADPH) redox status. However, exogenously applying AsA to Cd-exposed seedlings decreased Cd-induced ROS, improved antioxidant defense systems by increasing AsA, GSH, and NADPH contents, and increased Cd uptake and accumulation in both roots and shoots of the plants. These results provided evidence that the enhancement in AsA redox status can be linked to an increase in the GSH and/or NADPH redox ratios through the induction of the AsA-GSH-NADPH cycle. Thus, these results suggest that exogenous AsA application to oilseed rape seedlings under Cd stress might alleviate the overall Cd toxicity by regulating the homeostasis of the AsA-GSH-NADPH cycle, which reestablishes the steady-state cellular redox status.

Systematic investigation of the deformation mechanisms of a γ-TiAl single crystal.

We propose a theoretical framework to predict the deformation mechanism of the γ-TiAl single crystal without lattice defects by combining the generalized stacking fault energy and the Schmid factor. Our theory is validated against an excellent testbed, the single crystal nanowire, by correctly predicting four major deformation mechanisms, namely, ordinary slip, super slip, twinning, and mixed slip/fracture observed during the tensile and compressive tests along 10 different orientations using molecular dynamics simulations. Interestingly, although lattice defects are not taken into account, the theoretical predictions match well with existing experiments on bulk specimen with only a few exceptions; the exceptions are discussed based on the size-dependent deformation mechanism in the presence of preexisting dislocation sources. We expect that the method in this paper can be generalized to study various ductile intermetallic crystals where conventional Schmid law does not hold well.

Evaluation of sediment capping with activated carbon and nonwoven fabric mat to interrupt nutrient release from lake sediments.

The aim of this study was to assess the potential application of activated carbon (AC) and nonwoven fabric mats (NWFM) for thin-layer capping in remediation of sediments containing high amounts of carbon, nitrogen, and phosphorus. Laboratory column incubation experiments were performed to analyze the efficiencies of AC and NWFM for blocking nutrients. Under uncapped conditions, dissolved oxygen (DO) was exhausted within three days but under NWFM/AC capping conditions (with NWFM above the AC capping layer), the presence of DO was prolonged until Day 33. Chemical oxygen demand (COD) was lower under all capped conditions than under uncapped conditions, with lowest COD observed with NWFM/AC capping. NH4-N occupied the highest percentage of total nitrogen in the overlying water and its percentage increased as the DO concentration decreased. The capping efficiencies for NH4-N, T-N, and PO4-P with NWFM/AC capping were (66.0, 54.2, and 73.1) %, respectively, which were higher than for other capping conditions. In the case of T-P, capping efficiencies under all capping conditions were almost 100%, indicating that both AC and NWFM effectively interrupted phosphorus release from sediments. Placing NWFM above the AC capping layer was more effective than the opposite arrangement. It can be concluded that NWFM and AC can be successfully used for remediation of lake sediments with high amounts of nitrogen and phosphorus.

Phosphoiodyns A and B, unique phosphorus-containing iodinated polyacetylenes from a Korean sponge Placospongia sp.

Two unprecedented phosphorus-containing iodinated polyacetylenes, phosphoiodyns A and B (1-2), were isolated from a Korean marine sponge Placospongia sp. Their structures were elucidated by spectroscopic data analysis. Phosphoiodyn A exhibited potent agonistic activity on human peroxisome proliferator-activated receptor delta (hPPARδ) with an EC(50) of 23.7 nM.