Structural transition and migration of incoherent twin boundary in diamond.

Grain boundaries (GBs), with their diversity in both structure and structural transitions, play an essential role in tailoring the properties of polycrystalline materials1-5. As a unique GB subset, {112} incoherent twin boundaries (ITBs) are ubiquitous in nanotwinned, face-centred cubic materials6-9. Although multiple ITB configurations and transitions have been reported7,10, their transition mechanisms and impacts on mechanical properties remain largely unexplored, especially in regard to covalent materials. Here we report atomic observations of six ITB configurations and structural transitions in diamond at room temperature, showing a dislocation-mediated mechanism different from metallic systems11,12. The dominant ITBs are asymmetric and less mobile, contributing strongly to continuous hardening in nanotwinned diamond13. The potential driving forces of ITB activities are discussed. Our findings shed new light on GB behaviour in diamond and covalent materials, pointing to a new strategy for development of high-performance, nanotwinned materials.

Coherent interfaces govern direct transformation from graphite to diamond.

Understanding the direct transformation from graphite to diamond has been a long-standing challenge with great scientific and practical importance. Previously proposed transformation mechanisms1-3, based on traditional experimental observations that lacked atomistic resolution, cannot account for the complex nanostructures occurring at graphite-diamond interfaces during the transformation4,5. Here we report the identification of coherent graphite-diamond interfaces, which consist of four basic structural motifs, in partially transformed graphite samples recovered from static compression, using high-angle annular dark-field scanning transmission electron microscopy. These observations provide insight into possible pathways of the transformation. Theoretical calculations confirm that transformation through these coherent interfaces is energetically favoured compared with those through other paths previously proposed1-3. The graphite-to-diamond transformation is governed by the formation of nanoscale coherent interfaces (diamond nucleation), which, under static compression, advance to consume the remaining graphite (diamond growth). These results may also shed light on transformation mechanisms of other carbon materials and boron nitride under different synthetic conditions.

Hierarchically structured diamond composite with exceptional toughness.

The well known trade-off between hardness and toughness (resistance to fracture) makes simultaneous improvement of both properties challenging, especially in diamond. The hardness of diamond can be increased through nanostructuring strategies1,2, among which the formation of high-density nanoscale twins - crystalline regions related by symmetry - also toughens diamond2. In materials other than diamond, there are several other promising approaches to enhancing toughness in addition to nanotwinning3, such as bio-inspired laminated composite toughening4-7, transformation toughening8 and dual-phase toughening9, but there has been little research into such approaches in diamond. Here we report the structural characterization of a diamond composite hierarchically assembled with coherently interfaced diamond polytypes (different stacking sequences), interwoven nanotwins and interlocked nanograins. The architecture of the composite enhances toughness more than nanotwinning alone, without sacrificing hardness. Single-edge notched beam tests yield a toughness up to five times that of synthetic diamond10, even greater than that of magnesium alloys. When fracture occurs, a crack propagates through diamond nanotwins of the 3C (cubic) polytype along {111} planes, via a zigzag path. As the crack encounters regions of non-3C polytypes, its propagation is diffused into sinuous fractures, with local transformation into 3C diamond near the fracture surfaces. Both processes dissipate strain energy, thereby enhancing toughness. This work could prove useful in making superhard materials and engineering ceramics. By using structural architecture with synergetic effects of hardening and toughening, the trade-off between hardness and toughness may eventually be surmounted.

Flexible and Robust Core-Shell PANI/PVDF@PANI Nanofiber Membrane for High-Performance Electromagnetic Interference Shielding.

Developing high-performance electromagnetic interference (EMI) shielding materials that are lightweight and flexible and have excellent mechanical properties is an ideal choice for modern integrated electronic devices and microwave protection. Herein, we report the preparation of core-shell polyaniline (PANI)-based nanofiber membranes for EMI shielding through seed polymerization. Electrospinning a PANI solution leads to homogeneously dispersed PANI on the nanofiber surface, with abundant attachment sites for aniline through electrostatic adsorption and hydrogen bonding interaction, allowing PANI to grow on the nanofiber surfaces. This stable core-shell heterostructure provides more interfaces for reflecting and absorbing microwaves. The PANI/PVDF@PANI membranes achieved a shielding efficiency (SE) of 44.7 dB at a thickness of only 1.2 mm, exhibiting an exceptionally high specific EMI shielding effectiveness (SE/t) of 372.5 dB cm-1. Furthermore, the composite membrane exhibits outstanding mechanical stability, durability, air permeability, and moisture permeability, also making it suitable for applications such as EM shielding clothing.

A Color-Changing Biomimetic Material Closely Resembling the Spectral Characteristics of Vegetation Foliage.

Multispectral/hyperspectral technologies can easily detect man-made objects in vegetation by subtle spectral differences between the object and vegetation, and powerful reconnaissance increases the demand for camouflage materials closely resembling vegetation spectra. However, previous biomimetic materials have only presented static colors that cannot change color, and camouflage in multiple bands is difficult to achieve. To address this challenge, inspiration is drawn from the color change of foliage, and a color-change model is proposed with active and static pigments embedded in a matrix medium. The color of a composite material is dominated by the colored active pigment, which conceals the color of the static pigments and the color is revealed when the active pigment fades. A color-changing biomimetic material (CCBM) is developed with a solution casting method by adopting microcapsuled thermochromic pigments and chrome titanate yellow pigments as fillers in a base film with polyvinyl alcohol and lithium chloride. A Kubelka-Munk four-flux model is constructed to optimize the component proportions of the CCBM. The material has a reversible color change, closely resembles the foliage spectrum in UV-vis-NIR ranges, and imitates the thermal behavior of natural foliage in the mid-infrared regime. These results provide a novel approach to multispectral and hyperspectral camouflage.

Self-healing of fractured diamond.

Materials that possess the ability to self-heal cracks at room temperature, akin to living organisms, are highly sought after. However, achieving crack self-healing in inorganic materials, particularly with covalent bonds, presents a great challenge and often necessitates high temperatures and considerable atomic diffusion. Here we conducted a quantitative evaluation of the room-temperature self-healing behaviour of a fractured nanotwinned diamond composite, revealing that the self-healing properties of the composite stem from both the formation of nanoscale diamond osteoblasts comprising sp2- and sp3-hybridized carbon atoms at the fractured surfaces, and the atomic interaction transition from repulsion to attraction when the two fractured surfaces come into close proximity. The self-healing process resulted in a remarkable recovery of approximately 34% in tensile strength for the nanotwinned diamond composite. This discovery sheds light on the self-healing capability of nanostructured diamond, offering valuable insights for future research endeavours aimed at enhancing the toughness and durability of brittle ceramic materials.

Ultrastrong conductive in situ composite composed of nanodiamond incoherently embedded in disordered multilayer graphene.

Traditional ceramics or metals cannot simultaneously achieve ultrahigh strength and high electrical conductivity. The elemental carbon can form a variety of allotropes with entirely different physical properties, providing versatility for tuning mechanical and electrical properties in a wide range. Here, by precisely controlling the extent of transformation of amorphous carbon into diamond within a narrow temperature-pressure range, we synthesize an in situ composite consisting of ultrafine nanodiamond homogeneously dispersed in disordered multilayer graphene with incoherent interfaces, which demonstrates a Knoop hardness of up to ~53 GPa, a compressive strength of up to ~54 GPa and an electrical conductivity of 670-1,240 S m-1 at room temperature. With atomically resolving interface structures and molecular dynamics simulations, we reveal that amorphous carbon transforms into diamond through a nucleation process via a local rearrangement of carbon atoms and diffusion-driven growth, different from the transformation of graphite into diamond. The complex bonding between the diamond-like and graphite-like components greatly improves the mechanical properties of the composite. This superhard, ultrastrong, conductive elemental carbon composite has comprehensive properties that are superior to those of the known conductive ceramics and C/C composites. The intermediate hybridization state at the interfaces also provides insights into the amorphous-to-crystalline phase transition of carbon.

Hard Copper Boride with Exceptional Conductivity.

Copper and boron seldom engage in reaction at ambient pressure. The few reports on copper-doped boron compounds that exist in the literature often lack definitive stoichiometry. Here, we report successful synthesis of Cu_{2-δ}B_{25} single crystals (δ∼0.03, indicating Cu understoichiometry) via a high-pressure melting method using copper and ß-rhombohedral boron as precursors. Crystals thus synthesized are characterized by a tetragonal boron sublattice, within which Cu atoms are either partially or fully situated at different interstices between B_{12} icosahedra. The crystals possess a high Vickers hardness of 26.5 GPa and an unusually high electrical conductivity of 1.19×10^{5} S/m-the highest conductivity among the icosahedron-based borides. Hall measurements reveal a notable p-n conduction type transition around 30 GPa. This transition, alongside the remarkable conductivity, is potentially modulated by the copper content and its valence states within the structure. The synthesis of Cu_{2-δ}B_{25} not only broadens the spectrum of hard materials but also opens new avenues for innovative modulation of electronic properties in boron-rich compounds, with promising technological implications.

High-performance presurgical differentiation of glioblastoma and metastasis by means of multiparametric neurite orientation dispersion and density imaging (NODDI) radiomics.

OBJECTIVES: To evaluate the performance of multiparametric neurite orientation dispersion and density imaging (NODDI) radiomics in distinguishing between glioblastoma (Gb) and solitary brain metastasis (SBM). MATERIALS AND METHODS: In this retrospective study, NODDI images were curated from 109 patients with Gb (n = 57) or SBM (n = 52). Automatically segmented multiple volumes of interest (VOIs) encompassed the main tumor regions, including necrosis, solid tumor, and peritumoral edema. Radiomics features were extracted for each main tumor region, using three NODDI parameter maps. Radiomics models were developed based on these three NODDI parameter maps and their amalgamation to differentiate between Gb and SBM. Additionally, radiomics models were constructed based on morphological magnetic resonance imaging (MRI) and diffusion imaging (diffusion-weighted imaging [DWI]; diffusion tensor imaging [DTI]) for performance comparison. RESULTS: The validation dataset results revealed that the performance of a single NODDI parameter map model was inferior to that of the combined NODDI model. In the necrotic regions, the combined NODDI radiomics model exhibited less than ideal discriminative capabilities (area under the receiver operating characteristic curve [AUC] = 0.701). For peritumoral edema regions, the combined NODDI radiomics model achieved a moderate level of discrimination (AUC = 0.820). Within the solid tumor regions, the combined NODDI radiomics model demonstrated superior performance (AUC = 0.904), surpassing the models of other VOIs. The comparison results demonstrated that the NODDI model was better than the DWI and DTI models, while those of the morphological MRI and NODDI models were similar. CONCLUSION: The NODDI radiomics model showed promising performance for preoperative discrimination between Gb and SBM. CLINICAL RELEVANCE STATEMENT: The NODDI radiomics model showed promising performance for preoperative discrimination between Gb and SBM, and radiomics features can be incorporated into the multidimensional phenotypic features that describe tumor heterogeneity. KEY POINTS: • The neurite orientation dispersion and density imaging (NODDI) radiomics model showed promising performance for preoperative discrimination between glioblastoma and solitary brain metastasis. • Compared with other tumor volumes of interest, the NODDI radiomics model based on solid tumor regions performed best in distinguishing the two types of tumors. • The performance of the single-parameter NODDI model was inferior to that of the combined-parameter NODDI model.

Bottom-up design of carbon allotropes with tunable properties.

Carbon materials have received great attention owing to their numerous allotropes and rich properties. Structure design and property tuning of carbon materials is one of the tremendous challenges in the field of materials science research. Here we carried out a bottom-up approach and identified a series of carbon allotropes with similar structures but distinct properties. The structures designed in this work had comparable energy stability to those previously predicted using the top-down global structure search method. Theoretical property calculations demonstrated that the three carbon structures with pure sp3 hybridization possessed semiconductive and superhard properties, while the carbon structure with sp2 + sp3 hybridization exhibited metallic features. Also, they differed significantly in the anisotropy of the mechanical properties. These carbon structures had some match to the unidentified phases in the detonation soot and could hopefully be synthesized by thermal "degassing" of high-pressure Na-C products. Our results propose a strategy to regulate properties through structural tuning, thus paving a way for the design and synthesis of materials with desirable properties.

Extreme mechanical anisotropy in diamond with preferentially oriented nanotwin bundles.

Mechanical properties of covalent materials can be greatly enhanced with strategy of nanostructuring. For example, the nanotwinned diamond with an isotropic microstructure of interweaved nanotwins and interlocked nanograins shows unprecedented isotropic mechanical properties. How the anisotropic microstructure would impact on the mechanical properties of diamond has not been fully investigated. Here, we report the synthesis of diamond from superaligned multiwalled carbon nanotube films under high pressure and high temperature. Structural characterization reveals preferentially oriented diamond nanotwin bundles with an average twin thickness of ca. 2.9 nm, inherited from the directional nanotubes. This diamond exhibits extreme mechanical anisotropy correlated with its microstructure (e.g., the average Knoop hardness values measured with the major axis of the indenter perpendicular and parallel to nanotwin bundles are 233 ± 8 and 129 ± 9 GPa, respectively). Molecular dynamics simulation reveals that, in the direction perpendicular to the nanotwin bundles, the dense twin boundaries significantly hinder the motion of dislocations under indentation, while such a resistance is much weaker in the direction along the nanotwin bundles. Current work verifies the hardening effect in diamond via nanostructuring. In addition, the mechanical properties can be further tuned (anisotropy) with microstructure design and modification.

Radiomic texture analysis based on neurite orientation dispersion and density imaging to differentiate glioblastoma from solitary brain metastasis.

BACKGROUND: We created discriminative models of different regions of interest (ROIs) using radiomic texture features of neurite orientation dispersion and density imaging (NODDI) and evaluated the feasibility of each model in differentiating glioblastoma multiforme (GBM) from solitary brain metastasis (SBM). METHODS: We conducted a retrospective study of 204 patients with GBM (n = 146) or SBM (n = 58). Radiomic texture features were extracted from five ROIs based on three metric maps (intracellular volume fraction, orientation dispersion index, and isotropic volume fraction of NODDI), including necrosis, solid tumors, peritumoral edema, tumor bulk volume (TBV), and abnormal bulk volume. Four feature selection methods and eight classifiers were used for the radiomic texture feature selection and model construction. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of the models. Routine magnetic resonance imaging (MRI) radiomic texture feature models generated in the same manner were used for the horizontal comparison. RESULTS: NODDI-radiomic texture analysis based on TBV subregions exhibited the highest accuracy (although nonsignificant) in differentiating GBM from SBM, with area under the ROC curve (AUC) values of 0.918 and 0.882 in the training and test datasets, respectively, compared to necrosis (AUCtraining:0.845, AUCtest:0.714), solid tumor (AUCtraining:0.852, AUCtest:0.821), peritumoral edema (AUCtraining:0.817, AUCtest:0.762), and ABV (AUCtraining:0.834, AUCtest:0.779). The performance of the five ROI radiomic texture models in routine MRI was inferior to that of the NODDI-radiomic texture model. CONCLUSION: Preoperative NODDI-radiomic texture analysis based on TBV subregions shows great potential for distinguishing GBM from SBM.

Soft phonon modes lead to suppressed thermal conductivity in Ag-based chalcopyrites under high pressure.

Pressure is a powerful way to modulate physical properties. Understanding the effect of pressure on the thermal transport properties of thermoelectric materials is of great importance for the efficient design and optimization of thermoelectric performance. In this work, based on first-principles calculations and phonon Boltzmann transport theory, we find that the lattice thermal conductivities of Ag-based chalcopyrites AgXY2 (X = Al, Ga, and In; Y = S, Se, and Te) are dramatically suppressed by applying pressure. The inherent distorted tetrahedral configuration together with highly delocalized p-orbital electrons promotes the formation of metavalent bonding. The fact of metavalent bonding with a single bonding electron and small electron transfer between neighboring atoms leads to soft low-frequency optical phonons. With the increase of pressure, the softening of acoustic and low-frequency optical phonons induces enhanced anharmonicity and scattering channels. Such strong acoustic-optical phonon coupling results in larger phonon scattering rates and thus lowers the lattice thermal conductivity. These findings not only help unveil the underlying physical mechanisms for the anomalous thermal transport behaviors under high pressure, but also pave the way for the pressure tuning of high-performance Ag-based thermoelectric materials.

Hardness and electronic properties of Si-C-N structures.

Three novel hexagonal Si-C-N structures, namely SiC3N3, SiC7N6, and SiC13N14, were constructed on the basis of the α-Si3N4 crystal structure. The stability of the three structures is demonstrated by analyzing their elastic constants and phonon dispersion spectra and by calculating their formation energies. The calculated band structures and partial densities of states suggest that the SiC3N3 and SiC7N6 structures possess hole conductivity. The electron orbital analyses indicate that the SiC3N3 and SiC7N6 crystals possess three-dimensional and one-dimensional conductivity, respectively. SiC13N14 is a semiconductor with a wide bandgap of 4.39 eV. Based on two different hardness models and indentation shear stress calculations, the Vickers hardness values of SiC3N3, SiC7N6, and SiC13N14 are estimated to be 28.04/28.45/16.18 GPa, 31.17/34.19/20.24 GPa, and 40.60/41.59/36.40 GPa. This result indicates that SiC3N3 and SiC7N6 are conductive hard materials while SiC13N14 is a quasi superhard material.

Inhibition of human peptide deformylase by actinonin sensitizes glioblastoma cells to temozolomide chemotherapy.

Glioblastoma multiforme (GBM) is a common intracranial primary tumor of the central nervous system with high malignancy, poor prognosis, and short survival. Studies have shown that mitochondrial energy metabolism plays an important role in GBM chemotherapy resistance, suggesting that interrupting mitochondrial oxidative phosphorylation (OXPHOS) may improve GBM treatment. Human peptide deformylase (HsPDF) is a mitochondrial deformylase that removes the formylated methionine from the N-terminus of proteins encoded by mitochondrial DNA (mtDNA), thereby contributing to correct protein folding and participating in the assembly of the electron respiratory chain complex. In this study, we found that the expression of mtDNA-encoded proteins was significantly downregulated after treatment of GBM cells U87MG and LN229 with the HsPDF inhibitor, actinonin. In combination with temozolomide, a preferred chemotherapeutic medicine for GBM, the OXPHOS level decreased, mitochondrial protein homeostasis was unbalanced, mitochondrial fission increased, and the integrated stress response was activated to promote mitochondrial apoptosis. These findings suggest that HsPDF inhibition is an important strategy for overcoming chemoresistance of GBM cells.

A Lightweight Sentiment Analysis Framework for a Micro-Intelligent Terminal.

Sentiment analysis aims to mine polarity features in the text, which can empower intelligent terminals to recognize opinions and further enhance interaction capabilities with customers. Considerable progress has been made using recurrent neural networks or pre-trained models to learn semantic representations. However, recently published models with complex structures require increasing computational resources to reach state-of-the-art (SOTA) performance. It is still a significant challenge to deploy these models to run on micro-intelligent terminals with limited computing power and memory. This paper proposes a lightweight and efficient framework based on hybrid multi-grained embedding on sentiment analysis (MC-GGRU). The gated recurrent unit model is designed to incorporate a global attention structure that allows contextual representations to be learned from unstructured text using word tokens. In addition, a multi-grained feature layer can further enrich sentence representation features with implicit semantics from characters. Through hybrid multi-grained representation, MC-GGRU achieves high inference performance with a shallow structure. The experimental results of five public datasets show that our method achieves SOTA for sentiment classification with a trade-off between accuracy and speed.

Heterogeneous Diamond-cBN Composites with Superb Toughness and Hardness.

The traditional hardness-toughness tradeoff poses a substantial challenge for the development of superhard materials. Due to strong covalent bonds and intrinsic brittleness, the full advantage of microstructure engineering for enhanced mechanical properties requires further exploration in superhard materials. Here heterogeneous diamond-cBN composites were synthesized from a carefully prepared precursor (hBN microflakes uniformly wrapped by onion carbon nanoparticles) through phase transitions under high pressure and high temperature. The synthesized composites inherit the architecture of the precursors: cBN regions with an anisotropic profile that spans several micrometers laterally and several hundred nanometers in thickness are embedded in a nanograined diamond matrix with high-density nanotwins. A significantly high fracture toughness of 16.9 ± 0.8 MPa m1/2 is achieved, far beyond those of single-crystal diamond and cBN, without sacrificing hardness. A detailed TEM analysis revealed multiple toughening mechanisms closely related to the microstructure. This work sheds light on microstructure engineering in superhard materials for excellent mechanical properties.

Interfering with mitochondrial dynamics sensitizes glioblastoma multiforme to temozolomide chemotherapy.

Glioblastoma multiforme (GBM) is a primary tumour of the central nervous system (CNS) that exhibits the highest degree of malignancy. Radiotherapy and chemotherapy are essential to prolong the survival time of patients. However, clinical work has demonstrated that sensitivity of GBM to chemotherapy decreases with time. The phenomenon of multi-drug resistance (MDR) reminds us that there may exist some fundamental mechanisms in the process of chemo-resistance. We tried to explore the mechanism of GBM chemo-resistance from the perspective of energy metabolism. First, we found that the oxidative phosphorylation (OXPHOS) level of SHG44 and U87 cells increased under TMZ treatment. In further studies, it was found that the expression of PINK1 and mitophagy flux downstream was downregulated in GBM cells, which were secondary to the upregulation of TP53 in tumour cells under TMZ treatment. At the same time, we examined the mitochondrial morphology in tumour cells and found that the size of mitochondria in tumour cells increased under the treatment of TMZ, which originated from the regulation of AMPK on the subcellular localization of Drp1 under the condition of unbalanced energy supply and demand in tumour cells. The accumulation of mitochondrial mass and the optimization of mitochondrial quality accounted for the increased oxidative phosphorylation, and interruption of the mitochondrial fusion process downregulated the efficiency of oxidative phosphorylation and sensitized GBM cells to TMZ, which was also confirmed in the in vivo experiment. What is more, interfering with this process is an innovative strategy to overcome the chemo-resistance of GBM cells.

Adaptive Changes Allow Targeting of Ferroptosis for Glioma Treatment.

Ferroptosis is a type of regulated cell death that plays an essential role in various brain diseases, including cranial trauma, neuronal diseases, and brain tumors. It has been reported that cancer cells rely on their robust antioxidant capacity to escape ferroptosis. Therefore, ferroptosis exploitation could be an effective strategy to prevent tumor proliferation and invasion. Glioma is a common malignant craniocerebral tumor exhibiting complicated drug resistance and survival mechanisms, resulting in a high mortality rate and short survival time. Recent studies have determined that metabolic alterations in glioma offer exploitable therapeutic targets. These metabolic alterations allow targeted therapy to achieve some initial efficacy but have failed to inhibit glioma growth, invasion, and drug resistance effectively. It has been proposed that the reason for the high malignancy and drug resistance observed with glioma is that these tumors can effectively evade ferroptosis. Ferroptosis-inducing drugs were found to exert a positive effect by targeting this particular characteristic of glioma cells. Moreover, gliomas develop enhanced drug resistance through anti-ferroptosis mechanisms. In this study, we provided an overview of the mechanisms by which glioma aggressiveness and drug resistance are mediated by the evasion of ferroptosis. This information might provide new targets for glioma therapy as well as new insights and ideas for future research.

Novel insights into lattice thermal transport in nanocrystalline Mg3Sb2 from first principles: the crucial role of higher-order phonon scattering.

Zintl phase Mg3Sb2, which has ultra-low thermal conductivity, is a promising anisotropic thermoelectric material. It is worth noting that the prediction and experiment value of lattice thermal conductivity (κ) maintain a remarkable difference, troubling the development and application. Thus, we firstly included the four-phonon scattering processes effect and performed the Peierls-Boltzmann transport equation (PBTE) combined with the first-principles lattice dynamics to study the lattice thermal transport in Mg3Sb2. The results showed that our theoretically predicted κ is consistent with the experimentally measured, breaking through the limitations of the traditional calculation methods. The prominent four-phonon scatterings decreased phonon lifetime, leading to the κ of Mg3Sb2 at 300 K from 2.45 (2.58) W m-1 K-1 to 1.94 (2.19) W m-1 K-1 along the in (cross)-plane directions, respectively, and calculation accuracy increased by 20%. This study successfully explains the lattice thermal transport behind mechanism in Mg3Sb2 and implies guidance to advance the prediction accuracy of thermoelectric materials.