Structural superlubricity at the interface of penta-BN2.

Two-dimensional (2D) materials have been widely used as lubricants due to their weak interlayer interaction and low shear resistance for interlayer sliding. Composed entirely of five-membered rings, penta-BN2 monolayer has excellent thermal and mechanical stability, higher hardness and a negative Poisson's ratio. In this work, we investigate the frictional properties at both the commensurate and incommensurate contacting interfaces of penta-BN2 by adopting the molecular dynamics (MD) simulation method. Our calculations demonstrate robust superlubricity at the incommensurate contacting interface of penta-BN2. The ultra-low friction is explained by the potential energy surface (PES) fluctuations, interlayer binding energy and out-of-plane motion amplitude of the sliding layer. In addition, our calculations show that the anisotropy of friction at the commensurate contacting interface is more obvious compared with that at the incommensurate contacting interface. Finally, the influences of the size of the Moiré pattern, normal force, temperature and sliding velocity on the friction are examined. Our results show that 2D penta-BN2 is a promising solid lubricant, enriching the family of 2D lubrication materials.

Charge density fluctuation determined the interlayer friction in bilayer MN4 (M = Be, Mg, and Pt).

MN4 (M = Be, Mg, and Pt) represents a new class of van der Waals materials. These materials are characterized by exceptional electrical and thermal conductivities, remarkable intralayer mechanical strength, and weak interlayer interactions, making them prone to shearing and slipping. Therefore, MN4 has significant potential applications as a solid lubricant. However, until now, there have been only limited comprehensive theoretical investigations focusing on the frictional properties of MN4 systems. Here, the frictional performances of MN4 are systematically analyzed by applying first-principles high-throughput calculations. The results reveal that interlayer friction of MN4 decreases from MgN4 to BeN4 and then to PtN4. The friction is directly determined by charge density variations during the sliding processes. The periodic formation and breaking of quasi-σ bonds in bilayer MgN4 leads to substantial variations in charge density and large interlayer friction. In contrast, the weak charge density alternations in PtN4 lead to rather low frictions in PtN4. Moreover, surface functionalization effectively diminishes friction within bilayer MgN4, but amplifies interlayer friction within bilayer PtN4, and under surface functionalization interlayer friction can be efficiently modulated by out-of-plane polarizations. Interestingly, HBr-MgN4 exhibits two orders of magnitude lower COF compared to intrinsic bilayer MgN4, leading to a phenomenon resembling superlubricity. These results significantly contribute to our understanding of the friction properties, offering valuable guidance for the practical implementation of MN4 in solid lubricants.

A randomized trial of Bacteroides fragilis 839 on preventing chemotherapy-induced myelosuppression and gastrointestinal adverse effects in breast cancer patients.

BACKGROUND AND OBJECTIVES: To evaluate the potential benefits of Bacteroides fragilis 839 (BF839), a next-generation probiotics, in reducing myelosuppression and gastrointestinal toxicity associated with chemotherapy in breast cancer patient. METHODS AND STUDY DESIGN: 40 women with early breast cancer were randomly assigned to the BF839 (n=20) or placebo (n=20) during the administration of adjuvant chemotherapy (4 cycles of epirubicin 100mg/m2 and cyclophosphamide 600mg/m2). Myelosuppression and gastrointestinal adverse effects were monitored in both groups. RESULTS: Throughout the four treatment cycles, the percentage of patients experiencing myelosuppression was 42.5% in the BF839 group, significantly lower than the 66.3% observed in the control group (p=0.003). Two patients in the BF839 group and three patients in the placebo group received recombinant human granulocyte colony-stimulating factor (rhG-CSF) due to leuko-penia/neutropenia. When considering an ITT analysis, which included all patients regardless of rhG-CSF treatment, the BF839 group exhibited less reduction from baseline in white blood cells (-0.31±1.19 vs -1.15±0.77, p=0.012) and neutrophils (0.06±1.00 vs -0.84±0.85, p=0.004) compared to the placebo group. The difference became even more significant when excluding the patients who received rhG-CSF injections. Throughout the four treatment cycles, compared to the placebo group, the BF839 group had significantly lower rates of 3-4 grade nausea (35.0% vs 71.3%, p=0.001), vomiting (20.0% vs 45.0%, p=0.001), and diarrhea (15.0% vs 30.0%, p=0.023). CONCLUSIONS: These findings suggest that BF839 has the potential to effectively mitigate myelosuppression and gastrointestinal toxicity associated with chemotherapy in breast cancer patients.

Switchable Anomalous Hall Effects in Polar-Stacked 2D Antiferromagnet MnBi2Te4.

van der Waals (vdW) assembly of two-dimensional (2D) materials allows polar layer stacking to realize novel properties switchable by the induced electric polarization. Here, based on symmetry analyses and density-functional calculations, we explore the emergence of the anomalous Hall effect (AHE) in antiferromagnetic MnBi2Te4 films assembled by polar layer stacking. We demonstrate that breaking P̂T̂ symmetry in an MnBi2Te4 bilayer produces a magnetoelectric effect and a spontaneous AHE switchable by electric polarization. We find that reversible polarization at one of the interfaces in a three-layer MnBi2Te4 film drives a metal-insulator transition, as well as switching between the AHE and quantum AHE (QAHE). Finally, we predict that engineering interlayer polarization in a three-layer MnBi2Te4 film allows converting MnBi2Te4 from a trivial insulator to a Chern insulator. Overall, our work emphasizes the topological properties in 2D vdW antiferromagnets induced by polar layer stacking, which do not exist in a bulk material.

CO2 coverage on Pd catalysts accelerates oxygen removal in oxy-combustion systems.

Oxy-combustion systems result in enriched CO2 in exhaust gases; however, the utilization of the concentrated CO2 stream from oxy-combustion is limited by remnant O2. CH4 oxidation using Pd catalysts has been found to have high O2-removal efficiency. Here, the effect of excess CO2 in the feed stream on O2 removal with CH4 oxidation is investigated by combining experimental and theoretical approaches. Experimental results reveal complete CH4 oxidation without any side-products, and a monotonic increase in the rate of CO2 generation with an increase in CO2 concentration in the feed stream. Density-functional theory calculations show that high surface coverage of CO2 on Pd leads to a reduction in the activation energy for the initial dissociation of CH4 into CH3 and H, and also the subsequent oxidation reactions. A CO2-rich environment in oxy-combustion systems is therefore beneficial for the reduction of oxygen in exhaust gases.

Cu-doped SnS2 nanosheets with superior visible-light photocatalytic CO2 reduction performance.

Photocatalytic CO2 reduction utilizing solar energy is a clean, environment-friendly strategy converting CO2 into hydrocarbon fuels to solve the energy crisis and climate issues. Herein, we report the synthesis of Cu-doped SnS2 nanosheets via a simple hydrothermal method. The prepared Cu-doped SnS2 composite displays superior photocatalytic CO2 reduction activity. The optimized CH3OH yield of the composite is two times higher than that of pure SnS2. The enhanced photocatalytic performance is attributed to effective charge separation resulting from the thinner nanosheets and delocalization of electrons from SnS2 to Cu, high visible light utilization efficiency, enlarged SBET, negative shift of the flat-band potential and reduced charge transfer resistance with the introduction of Cu atoms. This work suggests the potential application of Cu-doped SnS2 in photocatalytic CO2 reduction.

Tunable electrical properties and multiple-phases of ferromagnetic GdS2, GdSe2 and Janus GdSSe monolayers.

With the continuous miniaturization and integration of spintronic devices, the two-dimensional (2D) ferromagnet coupling of ferromagnetic and diverse electrical properties has become increasingly important. Herein, we report three ferromagnetic monolayers: GdS2, GdSe2 and Janus GdSSe. They are bipolar magnetic semiconductors and demonstrate ferroelasticity with a large reversible strain of 73.2%. Three monolayers all hold large magnetic moments of about 8µB f.u.-1 and large spin-flip energy gaps in both the conduction and valence bands, which are highly desirable for applications in bipolar field effect spin filters and spin valves. Our calculations have testified to the feasibility of the experimental achievement of the three monolayers and their stability. Additionally, intrinsic valley polarization occurs in the three monolayers owing to the cooperative interplay between spin-orbit coupling and magnetic exchange interaction. Moreover, we identified square lattices for GdS2 and GdSe2 monolayers. The new and stable square lattices of GdS2 and GdSe2 monolayers show robust ferromagnetism with high Curie temperatures of 648 and 312 K, respectively, and the characteristics of spin-gapless semiconductors. Overall, these findings render GdS2, GdSe2 and Janus GdSSe monolayers promising candidate materials for multifunctional spintronic devices at the nanoscale.

Spontaneous Seed Formation during Electrodeposition Drives Epitaxial Growth of Metastable Bismuth Selenide Microcrystals.

Materials with metastable phases can exhibit vastly different properties from their thermodynamically favored counterparts. Methods to synthesize metastable phases without the need for high-temperature or high-pressure conditions would facilitate their widespread use. We report on the electrochemical growth of microcrystals of bismuth selenide, Bi2Se3, in the metastable orthorhombic phase at room temperature in aqueous solution. Rather than direct epitaxy with the growth substrate, the spontaneous formation of a seed layer containing nanocrystals of cubic BiSe enforces the metastable phase. We first used single-crystal silicon substrates with a range of resistivities and different orientations to identify the conditions needed to produce the metastable phase. When the applied potential during electrochemical growth is positive of the reduction potential of Bi3+, an initial, Bi-rich seed layer forms. Electron microscopy imaging and diffraction reveal that the seed layer consists of nanocrystals of cubic BiSe embedded within an amorphous matrix of Bi and Se. Using density functional theory calculations, we show that epitaxial matching between cubic BiSe and orthorhombic Bi2Se3 can help stabilize the metastable orthorhombic phase over the thermodynamically stable rhombohedral phase. The spontaneous formation of the seed layer enables us to grow orthorhombic Bi2Se3 on a variety of substrates including single-crystal silicon with different orientations, polycrystalline fluorine-doped tin oxide, and polycrystalline gold. The ability to stabilize the metastable phase through room-temperature electrodeposition in aqueous solution without requiring a single-crystal substrate broadens the range of applications for this semiconductor in optoelectronic and electrochemical devices.

CGR-Block: Correlated Feature Extractor and Geometric Feature Fusion for Point Cloud Analysis.

Point cloud processing based on deep learning is developing rapidly. However, previous networks failed to simultaneously extract inter-feature interaction and geometric information. In this paper, we propose a novel point cloud analysis module, CGR-block, which mainly uses two units to learn point cloud features: correlated feature extractor and geometric feature fusion. CGR-block provides an efficient method for extracting geometric pattern tokens and deep information interaction of point features on disordered 3D point clouds. In addition, we also introduce a residual mapping branch inside each CGR-block module for the further improvement of the network performance. We construct our classification and segmentation network with CGR-block as the basic module to extract features hierarchically from the original point cloud. The overall accuracy of our network on the ModelNet40 and ScanObjectNN benchmarks achieves 94.1% and 83.5%, respectively, and the instance mIoU on the ShapeNet-Part benchmark also achieves 85.5%, proving the superiority of our method.

Direct Observation and Control of Surface Termination in Perovskite Oxide Heterostructures.

Interfacial behavior of quantum materials leads to emergent phenomena such as quantum phase transitions and metastable functional phases. Probes for in situ and real time surface-sensitive characterization are critical for control during epitaxial synthesis of heterostructures. Termination switching in complex oxides has been studied using a variety of probes, often ex situ; however, direct in situ observation of this phenomena during growth is rare. To address this, we establish in situ and real time Auger electron spectroscopy for pulsed laser deposition with reflection high energy electron diffraction, providing structural and compositional surface information during film deposition. Using this capability, we show the direct observation and control of surface termination in heterostructures of SrTiO3 and SrRuO3. Density-functional-theory calculations capture the energetics and stability of the observed structures, elucidating their electronic behavior. This work demonstrates an exciting approach to monitor and control the composition of materials at the atomic scale for control over emergent phenomena and potential applications.

Peptide-Based Capture of Chikungunya Virus E2 Protein Using Porous Silicon Biosensor.

The detection of pathogens presents specific challenges in ensuring that biosensors remain operable despite exposure to elevated temperatures or other extreme conditions. The most vulnerable component of a biosensor is typically the bioreceptor. Accordingly, the robustness of peptides as bioreceptors offers improved stability and reliability toward harsh environments compared to monoclonal antibodies that may lose their ability to bind target molecules after such exposures. Here, we demonstrate peptide-based capture of the Chikungunya virus E2 protein in a porous silicon microcavity biosensor at room temperature and after exposure of the peptide-functionalized biosensor to high temperature. Contact angle measurements, attenuated total reflectance-Fourier transform infrared spectra, and optical reflectance measurements confirm peptide functionalization and selective E2 protein capture. This work opens the door for other pathogenic biomarker detection using peptide-based capture agents on porous silicon and other surface-based sensor platforms.

Photonic crystal nanobeam biosensors based on porous silicon.

Photonic crystal (PhC) nanobeams (NB) patterned on porous silicon (PSi) waveguide substrates are demonstrated for the specific, label-free detection of oligonucleotides. These photonic structures combine the large active sensing area intrinsic to PSi sensors with the high-quality (Q) factor and low-mode volume characteristic of compact resonant silicon-on-insulator (SOI) PhC NB devices. The PSi PhC NB can achieve a Q-factor near 9,000 and has an approximately 40-fold increased active sensing area for molecular attachment, compared to traditional SOI PhC NB sensors. The PSi PhC NB exhibits a resonance shift that is more than one order of magnitude larger than that of a similarly designed SOI PhC NB for the detection of small chemical molecules and 16-base peptide nucleic acids. The design and fabrication of PSi PhC NB sensors are compatible with CMOS processing, sensor arrays, and integration with lab-on-chip systems.

A smartphone biosensor based on analysing structural colour of porous silicon.

We report a smartphone compatible, low-cost porous silicon biosensor, which correlates the structural colour of a porous silicon microcavity (PSiM) to spectral peak position. Molecules captured in the PSiM cause a colour change that can be quantified through image analysis. Minimal external accessories are employed. Spectrometer measurements of the PSiM reflectance spectrum shifts are carried out concurrently with the smartphone measurements to benchmark the accuracy of the smartphone biosensor. We estimate that the smartphone biosensor supports an equivalent accuracy of 0.33 nm for the detection of colour changes corresponding to spectral shifts of the PSiM. Biosensing functionality is demonstrated using a biotin-streptavidin assay with an estimated detection limit of 500 nM. The PSiM-smartphone biosensor is a promising platform for label-free point of care diagnostics.

Digital gene expression analysis in the gills of Ruditapes philippinarum after nitrite exposure.

Due to the overload of pollutants from highly intensive anthropic activities, nitrite accumulates in offshore seawater and has been a long-lasting pollutant to the healthy aquaculture of the mollusk. In the present study, Ruditapes philippinarum was used as the target bivalve to receive nitrite exposure at environmental concentration for 1 and 7 days. Differentially expressed genes (DEGs) were detected and analyzed by a digital gene expression (DGE) approach to describe the toxicity of nitrite on the bivalve at the gene level. In the N1 group, 185 DEGs were generated and enriched in six Gene Ontology (GO) terms, including oxidoreductase activity, heme binding, tetrapyrrole binding, iron ion binding, metal binding and cation binding. The DEGs in the N1 group were also enriched in two Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, e.g., arachidonic acid metabolism and ovarian steroidogenesis. In the N7 group, 81 DEGs were generated without any GO enrichment but were enriched in five KEGG pathways, including protein processing in the endoplasmic reticulum, protein export, prion diseases, thyroid hormone synthesis and arachidonic acid metabolism. This suggested that nitrite exposure might cause adverse effects to the clams in several aspects, including oxidative damage, depressed immunity, and disorders in cell proliferation, hormone metabolism and tissue regeneration. Evaluation of oxidative stress indicated that nitrite exposure actually induced redox state imbalance by enhancing the contents of thiobarbituric acid reactive substances (TBARSs) and glutathione (GSH), and the activity of glutathione peroxidase (GSH-PX) but not superoxide dismutase (SOD). These results will provide valuable gene references for further study on the toxicology mechanism of bivalves under environmental nitrite stress.

First-Principles Calculation of Third-Order Elastic Constants via Numerical Differentiation of the Second Piola-Kirchhoff Stress Tensor.

A general method is presented to calculate from first principles the full set of third-order elastic constants of a material of arbitrary symmetry. The method here illustrated relies on a plane-wave density functional theory scheme to calculate the Cauchy stress and the numerical differentiation of the second Piola-Kirchhoff stress tensor to evaluate the elastic constants. It is shown that finite difference formulas lead to a cancellation of the finite basis set errors, whereas simple solutions are proposed to eliminate numerical errors arising from the use of Fourier interpolation techniques. Applications to diamond, silicon, aluminum, magnesium, graphene, and a graphane conformer give results in excellent agreement with both experiments and previous calculations based on fitting energy density curves, demonstrating both the accuracy and generality of our new methodology to investigate nonlinear elastic behaviors of materials.

A Reduced Graphene Oxide/Disodium Terephthalate Hybrid as a High-Performance Anode for Sodium-Ion Batteries.

As a promising candidate for large-scale energy storage systems, sodium-ion batteries (SIBs) are experiencing a rapid development. Organic conjugated carboxylic acid anodes not only have tailorable electrochemical properties but also are easily accessible. However, the low stability and electrical conductivity hamper their practical applications. In this study, disodium terephthalate (Na2 TP), the most favorable organic conjugated carboxylic acid anode material for SIBs, was proposed to integrate with graphene oxide (GO) by an anti-solvent precipitation process, which ensures the uniform and tight coating of GO on the Na2 TP surface. GO is electrochemically reduced during the first several cycles of the electrochemical measurement, which buffers the volume change and improves the electrical conductivity of Na2 TP, resulting in a better cyclic and rate performance. The incorporation of only 5 wt % GO onto Na2 TP leads to a reversible capability of 235 mA h g-1 after 100 cycles at a current rate of 0.1 C, which is the best among the state of the art organic anodes for SIBs. The one-step synthesis together with the low costs of the raw materials show a promise for the scalable preparation of anode materials for practical SIBs.

A strain or electric field induced direct bandgap in ultrathin silicon film and its application in photovoltaics or photocatalysis.

The indirect bandgap character of silicon greatly limits its applications in electronic or optoelectronic devices, and direct bandgaps are highly desirable in all silicon allotropes. The successful synthesis of ultrathin or even monolayer silicon films experimentally has opened new opportunities to further modulate the electronic structure of silicon through external modulation. In this work, strain or electric field effects on the electronic structure of ultrathin silicon film (USF) are systematically explored. The results demonstrate that all USFs are indirect band-gap semiconductors; interestingly, tensile strain or electric field efficiently tunes the USFs into direct band gap semiconductors. The indirect to direct band gap transition in the USFs not only extends their light adsorption spectra into the visible light region but also greatly enhances the adsorption intensity. Because of this, strained USFs have great potential to be used as a high-performance photovoltaic material. Furthermore, the high stability, moderate band-gap and proper band edge positions demonstrate that monolayer and bilayer USFs can also be used as photocatalysts for water splitting.

Research and experimental verification on the mechanisms of cellular senescence in triple-negative breast cancer.

Background: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with high heterogeneity, poor prognosis, and a low 10-year survival rate of less than 50%. Although cellular senescence displays extensive effects on cancer, the comprehensions of cellular senescence-related characteristics in TNBC patients remains obscure. Method: Single-cell RNA sequencing (scRNA-seq) data were analyzed by Seurat package. Scores for cellular senescence-related pathways were computed by single-sample gene set enrichment analysis (ssGSEA). Subsequently, unsupervised consensus clustering was performed for molecular cluster identification. Immune scores of patients in The Cancer Genome Atlas (TCGA) dataset and associated immune cell scores were calculated using Estimation of STromal and Immune cells in MAlignantTumours using Expression data (ESTIMATE) and Microenvironment Cell Populations-counter (MCP-counter), Tumor Immune Estimation Resource (TIMER) and Estimating the Proportion of Immune and Cancer cells (EPIC) methods, respectively. Immunotherapy scores were assessed using TIDE. Furthermore, feature genes were identified by univariate Cox and Least Absolute Shrinkage and Selection Operator (LASSO) regression analyses; these were used to construct a risk model. Additionally, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and transwell assay were conducted for in vitro validation of hub genes. Result: TNBC was classified into three subtypes based on cellular senescence-related pathways as clusters 1, 2, and 3. Specifically, cluster 1 showed the best prognosis, followed by cluster 2 and cluster 3. The levels of gene expression in cluster 2 were the lowest, whereas these were the highest in cluster 3. Moreover, clusters 1 and 3 showed a high degree of immune infiltration. TIDE scores were higher for cluster 3, suggesting that immune escape was more likely in patients with the cluster 3 subtype who were less likely to benefit from immunotherapy. Next, the TNBC risk model was constructed and validated. RT-qPCR revealed that prognostic risk genes (MMP28, ACP5 and KRT6A) were up-regulated while protective genes (CT83) were down-regulated in TNBC cell lines, validating the results of the bioinformatics analysis. Meanwhile, cellular experiments revealed that ACP5 could promote the migration and invasion abilities in two TNBC cell lines. Finally, we evaluated the validity of prognostic models for assessing TME characteristics and TNBC chemotherapy response. Conclusion: In conclusion, these findings help to assess the efficacy of targeted therapies in patients with different molecular subtypes, have practical applications for subtype-specific treatment of TNBC patients, and provide information on prognostic factors, as well as guidance for the revelation of the molecular mechanisms by which senescence-associated genes influence TNBC progression.

Two-dimensional MN4 materials as effective multifunctional electrocatalysts for the hydrogen-evolution, oxygen-evolution, and oxygen-reduction reactions.

Two-dimensional (2D) materials confining single atoms (SAs) for catalysis, such as graphene confining metal single atoms (M-N-C), integrate both aspects of 2D materials and single-atom catalysts (SACs). Significant advantages have been established in this new category of catalysts, which have seen rapid development in recent years. Recent studies have suggested a new class of novel 2D materials with a chemical formula of MN4 naturally holding a uniformly distributed M-N4 moiety. We investigated MN4 monolayers as multifunctional catalysts for the hydrogen-evolution reaction (HER), oxygen-evolution reaction (OER), and oxygen-reduction reaction (ORR). Among them, the IrN4 monolayer demonstrated high catalytic activity towards these three reactions. The CoN4 monolayer was predicted to be an excellent bifunctional catalyst for the OER and ORR. A uniformly distributed and short-distanced M-N4 moiety on the MN4 monolayer made reactions between the intermediates during the OER and ORR possible, facilitating the release of O2 and H2O, respectively. In addition, the M atom of the MN4 monolayer having electronic states located at the Fermi level was active for catalyzing the HER. More importantly, changes in the Gibbs free energy of the two key intermediates of adsorption (ΔGOH* and ΔGOOH*) correlated closely with the Bader charge on the M atom (BM).

Protein Identification and Quantification Using Porous Silicon Arrays, Optical Measurements, and Machine Learning.

We report a versatile platform based on an array of porous silicon (PSi) thin films that can identify analytes based on their physical and chemical properties without the use of specific capture agents. The ability of this system to reproducibly classify, quantify, and discriminate three proteins separately is demonstrated by probing the reflectance of PSi array elements with a unique combination of pore size and buffer pH, and by analyzing the optical signals using machine learning. Protein identification and discrimination are reported over a concentration range of two orders of magnitude. This work represents a significant first step towards a low-cost, simple, versatile, and robust sensor platform that is able to detect biomolecules without the added expense and limitations of using capture agents.