Class III aminotransferases represent a structurally and functionally unique subgroup. However, the contribution of specific loop elements to their active-site architecture and cofactor-dependent structural transitions remain underexplored. We elucidated the structural framework underlying the catalytic function of class III fold Pyridoxal 5′-phosphate-dependent aminotransferase from the Antarctic bacterium Hymenobacter sp. PAMC 26554 (HyAT), and report its crystal structure at 2.31 Å resolution. The structure revealed a canonical class III fold organized as a functional homotetramer. Structural analysis identified a proline-containing motif (P-x-P) within the α10-α11 loop, which induces intrinsic disorder at the active-site entrance in the apo-form and revealed that a cooperative disorder-to-order transition is requisite for active-site assembly upon cofactor binding. We propose that this flexible loop region may be involved in modulating substrate access. Notably, this proline motif was conserved in homologs from Hyperthermophiles, despite the cold-adapted nature of HyAT. This convergence implies a common evolutionary strategy where the geometric constraints of proline are exploited to decouple local active-site dynamics from global scaffold stability, thereby addressing the stability–activity trade-off across diverse thermal environments. Our findings provide new molecular insights into the structural dynamics of class III aminotransferases and highlight evolutionary strategies for tuning enzyme flexibility in extreme environments.
In this study, Se-excess Ge₂Sb₂SeₓTe₁ (GSST) thin films were synthesized via magnetron co-sputtering. The crystal structure, surface morphology, complex refractive index, and bandgap of the Se-excess GSST thin films were systematically investigated. Owing to the formation of higher-energy Sb–Se bonds at an annealing temperature of 350 °C, grain refinement occurred (the average dendrite trunk width decreased from 0.64 μm to 0.37 μm). Consequently, the extinction coefficient (k) in the crystalline state was reduced to 0.17, resulting in a figure of merit (FOM) of 8.76 at the telecommunications C-band wavelength of 1550 nm.
This study investigated the effects of progressive step-heating (300–500 °C) and direct heating (500 °C) on pinkish-orange and red tourmalines using colorimetric, spectroscopic, and chemical analyses. Heating progressively modified visible absorption and color, with treatment at 500 °C generally increasing lightness (L*) and substantially decreasing chroma (C*), accompanied by weakening of the broad absorption near 520 nm while strong pleochroism was retained. Chemical analyses revealed substantial compositional variability, particularly in Mn and Fe, although elemental abundance alone did not account for the observed optical responses. Color evolution was associated with changes in overlapping electronic absorption features, but the underlying microscopic processes could not be uniquely assigned to specific transition-metal ions or oxidation-state changes. Fourier transform infrared (FTIR) spectroscopy showed preservation of the principal framework-related vibrational features up to 500 °C, with no evidence of major structural disruption. Within the present step-heating series, 400 °C produced an intermediate outcome characterized by measurable lightening and desaturation while retaining more of the original pink-to-red chromatic component than after treatment at 500 °C, which produced substantially greater desaturation.
With continuing advances in interfacial sensing and tunable micro-optics, the potential applications of hemispherical nematic droplets in these fields have received increasing attention. Local variations in surface anchoring can modify their director configurations and thereby produce distinct optical responses. However, the specific manner in which anchoring conditions govern director configurations and defect formation remains poorly understood. Using the Landau–de Gennes theory, we investigate a model of a hemispherical droplet bounded by a curved surface and a planar base, with homeotropic easy-axis orientations prescribed at both interfaces. Four anchoring scenarios are compared: uniform anchoring, continuously varying curved-surface anchoring, localized weak-anchoring bands placed at different positions, and combinations of curved-surface and planar-base anchoring strengths. The results show that droplet size, spherical-cap height, and the strength and spatial position of anchoring all affect the director defect formation. Reducing the curved-surface anchoring strength near the contact line allows the director field to vary more continuously in this region, thereby suppressing the formation of the ring-shaped defect-core region. Distinct configurations, including a split-core structure near the symmetry axis, are obtained when the planar-base anchoring strength is varied under strong curved-surface anchoring.
A new nitro- and cyano-functionalized, tetradecyl-substituted benzothienoquinolizinium tetrafluoroborate was synthesized through oxidative photocyclisation of a pyridinium precursor and evaluated as a potential small molecule N-type organic semiconductor. The precursor and the photocyclised salts were characterized by UV–Vis absorption spectroscopy, DSC, 1H and 13C NMR, and cyclic voltammetry. Their optoelectronic properties were further investigated by DFT and TD-DFT calculations. Photocyclisation induced a marked bathochromic extension of the absorption profile, decreasing the optical band gap from 3.19 eV for the pyridinium precursor to 2.61 eV for the fused benzothienoquinolizinium salt. Cyclic voltammetry revealed a stabilized electrochemical LUMO level of approximately −3.87 eV, supporting the electron-deficient character of the nitro/cyano-substituted cationic scaffold. Frontier molecular orbital analysis showed that the HOMO and LUMO are mainly localized on the fused π-conjugated core and electron-withdrawing aryl substituents, with negligible contribution from the tetradecyl chain and BF4− counterion. TD-DFT and electron excitation analyses indicated that the monomeric low-energy transition has mixed local/charge-transfer character, whereas π-stacked dimers, especially the face-to-face arrangement, enhance charge transfer character and reduce electron–hole Coulombic attraction. Marcus type charge transport calculations revealed packing dependent behavior, with the face-to-face dimer displaying nearly ambipolar transport with a slight electron preference. A preliminary theoretical donor–acceptor model with hexaphenyl-substituted hexabenzocoronene further suggested energetic compatibility and strong intermolecular charge-transfer character. Overall, these results identify this benzothienoquinolizinium tetrafluoroborate as a promising electron-deficient cationic π-scaffold for future organic optoelectronic materials.
Porous multi-walled carbon nanotube (MWCNT) films combine strong optical absorption with thermal, Kerr-like, thermo-optical, and magneto-optical responses. However, these effects depend on film structure and may require different design conditions. In this work, a multiphysics model was used to analyze 12 MWCNT film configurations with dependance on thicknesses, porosity, and orientation parameters. The model included optical attenuation, transient heating, nonlinear refraction, thermo-optic modulation, magneto-optical response, and optical phase shift under irradiances of 7–20 MW cm−2 and magnetic fields up to 1 T. Optical density ranged from approximately 0.4 to 2.8, while transmittance showed negligible variation with irradiance. Thin and porous films produced the highest temperature rises, approximately 4.5 K, and the largest total refractive-index changes. In contrast, thicker films generated larger accumulated phase shifts. The thermo-optic contribution is dominated under nanosecond laser irradiation. As the pulse duration approached the picosecond regime, the lower deposited energy reduced the photothermal response, so the Kerr-like and magneto-optical terms accounted for a larger total refractive-index change. This predictive parametric study identifies architecture- and pulse-dependent trends for future experimental evaluation of multifunctional MWCNT films.
This study leverages multiple machine learning algorithms for defect detection in friction stir welding (FSW), utilizing force-derived features as model inputs. Furthermore, the underlying relationships between welding forces and defect formation were systematically investigated, alongside an evaluation of the efficacy of force-feature-driven defect detection models. Results indicated that the variations in the averages and waveforms in the traverse force (Fx), lateral force (Fy) and plunge force (Fz) are highly responsible for the defect formation in FSW joints, such that an increase in Fy causes waveform distortions in Fx and Fy. Fyavg is the most important feature for the defect formation for 724 sets of experimental data. Defect detection based on thresholding of Fyavg and Fzavg achieves an accuracy of 80.3%. In contrast, four machine learning algorithms—Decision Tree (DT), K-Nearest Neighbors (KNNs), Support Vector Machine (SVM), and Artificial Neural Network (ANN)—were employed to construct defect detection models using the extracted force features as inputs, yielding accuracies of 93.5%, 97.5%, 95.7% and 94.9%, respectively. These findings further elucidate the underlying mechanics, that is, Fx and Fy primarily originated from the extrusion and shear forces induced by the probe’s rotation and traverse, whereas Fz was predominantly attributed to the compressive action of the shoulder.
Ultrawide bandgap (UWBG) semiconductors are destined to become the foundation for next-generation power and radio-frequency (RF) electronic devices. Their superior qualities such as high thermal conductivity, strong critical electric field, and robust mechanical and radiation hardness are driving continuous and widespread research. Amongst the UWBG materials, aluminum nitride (AlN) is highly attractive due to its direct ultrawide bandgap of about 6.2 eV, resulting in one of the highest Baliga’s and Johnson’s figures of merit. Equally important as its properties are material availability and growth methods capable of producing large-diameter substrates. In this work we report on bulk growth of 100 mm AlN crystals using the physical vapor transport (PVT) technique. The thermal gradients were simulated and tailored to obtain adequate thermal stresses, resulting in substrates with narrow X-ray rocking curves and dislocation densities in the range of 102–105 cm−2. In addition, the room-temperature thermal conductivity measured in two directions, perpendicular and parallel to the c-axis, was confirmed to be 300 W m−1 K−1. AlN substrates also demonstrated high UV transparency with absorption coefficients as low as 10 cm−1 at 265 nm wavelength. These results, along with the availability of 100 mm substrates, demonstrate that AlN is ready for further exploration and development for the power and RF electronics industry.
This study employs molecular dynamics (MD) simulations to explore the high-speed impact behavior of double conical tungsten (W) fragments on titanium (Ti) target plates, focusing on fragment cloud formation, Ti damage evolution, and the effects of temperature and impact velocity. High-speed impact converts W fragments’ kinetic energy into internal energy, causing W fragmentation and the formation of a mixed-phase fragment cloud, which induces severe damage to the Ti target. Under double-particle impacts, W fragments penetrate the Ti target to form a multi-source fragment cloud, with Ti target damage (characterized by amorphous phase distribution) undergoing initiation and extension stages. Higher temperatures broaden the high-temperature damage zone and increase crater size but do not change the impact penetration evolution mode or penetration depth. Impact velocity determines damage modes: low velocity causes non-through internal damage with a rear bulge, while high velocity leads to full perforation with mixed W-Ti fragment ejection, and lateral crater size is almost unaffected by velocity. This study innovatively reveals the atomic-scale damage evolution mechanism of Ti targets under dual conical W fragment impact, which fills the research gap in conventional single-fragment impact studies. These findings clarify the high-speed impact mechanism of Ti alloys, providing theoretical support for the design of Ti-based protective structures in engineering.
Cavitation erosion is a phenomenon that causes the degradation of engineering components operating in fluids under oscillating pressure, and it occurs through the repeated implosion of cavitation bubbles adjacent to the solid surface. This complex phenomenon involves both the hydrodynamic factors of the liquid and the properties of the material being eroded. Cavitation erosion tests were performed using a vibratory apparatus with piezoceramic crystals, in accordance with the ASTM G32-2016 standard. As a reference material, a wrought aluminum-based alloy in the hot-rolled condition, EN AW-6082, was selected. For both alloys, mass losses were measured and erosion rates were calculated. The eroded surfaces were examined by X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results indicate that the cavitation erosion resistance of the AZ 31B alloy in the hot-rolled condition is approximately 3.77 times lower than that of the reference material. This behavior is attributed to its lower hardness and heterogeneous microstructure, consisting of an α solid solution matrix with a hexagonal close-packed crystal structure and intermetallic particles of the Mg17Al12 type, which exhibit pronounced brittleness. Cavitation pits are observed mainly within the α-Mg solid solution grains and at the interfaces between the intermetallic phases and the α-Mg matrix.
High-purity SiC powder is an important feedstock for SiC crystal growth, but thermal-field regulation becomes difficult during large-batch synthesis. This study examined an α-SiC powder-synthesis furnace with upper and lower induction-coil groups through numerical simulations and 70 kg synthesis experiments. A representative two-dimensional axisymmetric model was used to compare eight cases with different coil-turn or numerical power allocations. Redistributing the coil turns changed E1, E2, volumetric Joule heat density, Q, and the resulting temperature and calculated gas-phase velocity-magnitude fields. From C01 to C04, the maximum calculated temperature decreased from 2501.10 to 2359.13 K, while ΔT decreased from 242.57 to 76.20 K. Increasing the upper-coil numerical power raised the temperature level while reducing ΔT to 152.41 K. Increasing the lower-coil numerical power also raised the temperature level, but increased ΔT to 292.26 K. Equal-total-power comparisons showed that axial power allocation affected Tmax and ΔT. XRD identified 6H-SiC as the detected crystalline phase in both analyzed middle-region specimens, although X-ray-amorphous carbon could not be excluded. The specimens also differed in macroscopic appearance, measured impurity concentrations, and local nitrogen concentration profiles. Because the experimental conditions were maintained nominally unchanged except for the upper-coil current, these specimen-level differences may be associated with altered internal thermal conditions. Such changes may affect local equilibrium, supersaturation, and species transport, providing a possible link to the observed material differences. The numerical results identify coil-turn allocation and axial power allocation as variables for regulating the calculated furnace fields.
Silicon nitride (Si3N4) is an advanced structural ceramic with considerable potential for load-bearing biomedical applications owing to its excellent mechanical properties and favorable biological response. In this study, the effect of wollastonite (CaSiO3) addition on the microstructure, mechanical performance, and in vitro bioactivity of Si3N4–CaSiO3 ceramic composites was investigated. Composites containing 5–30 wt.% wollastonite were prepared by pressureless sintering at 1800 °C for 1 h and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density measurements, nanoindentation, Vickers hardness, fracture toughness, compressive strength, and simulated body fluid (SBF) immersion tests. Increasing the wollastonite resulted in progressive densification up to 20 wt.% CaSiO3, resulting in a maximum relative density of 96%, together with complete α→β-Si3N4 transformation and the development of elongated β-Si3N4 grains. The composition containing 20 wt.% wollastonite exhibited optimum mechanical performance, achieving a hardness of approximately 13 GPa, fracture toughness of ~5.5 MPa·m1/2, and compressive strength of ~2840 MPa. The results demonstrate that wollastonite plays a multifunctional role in Si3N4 ceramic composites by promoting densification during sintering and improving in vitro bioactivity while maintaining high mechanical performance. These findings highlight the potential of Si3N4–CaSiO3 ceramic composites as promising bioactive structural materials for load-bearing orthopedic and dental applications.
Effects of varying lanthanum (La) content on the melting characteristics, spreadability, mechanical properties of brazed joints, and microstructure of low-silver BAg5CuZn brazing filler metal were investigated. The results indicate that the addition of La has little effect on the solidus and liquidus temperatures of the filler metal, while an excessive amount of La slightly raises its liquidus temperature. An appropriate amount of La enhances the spreadability of the filler metal on both copper and stainless steel plates and simultaneously inhibits grain growth, refining the microstructure of the BAg5CuZn-xLa filler metal. When the La content in the filler metal reaches 0.3%, the shear strength of the 304 stainless steel/304 stainless steel joint brazed with BAg5CuZn-xLa filler metal reaches 492 MPa, which is 17.7% higher than that of the brazed joint without the La addition.
Composition criteria for refractory high-entropy alloys (RHEAs) reliably predict whether a candidate composition forms a single-phase body-centred-cubic (BCC) solid solution, but not which BCC-confirmed composition will be strongest. Here we revisit seven previously reported RHEA compositions on freshly arc-melted material of our own, confirm each as single-phase BCC using full-spectrum X-ray diffraction re-indexing, and screen ten descriptors obtainable before mechanical testing against their room-temperature compressive yield strength: five compositional (mean atomic radius r−, mixing enthalpy ΔHmix, atomic-size mismatch δ, VEC, and melting point Tm), two lattice-scale (Nelson–Riley parameter a0 and Williamson–Hall apparent microstrain ε) and three microstructural (KAM, ELM15, and grain ECD). Only ΔHmix ranks the strengths, and its direction inverts the usual expectation: the less negative the mixing enthalpy, the stronger the alloy. Refractoriness carries no ranking information, and the most refractory member, NbMoTaW, is second weakest of six. At n = 6 only a perfect ranking reaches a Benjamini–Hochberg q below 0.05 across ten descriptors, so the q of 0.167 obtained here measures cohort resolution: a ranking of this magnitude clears the corrected threshold from eight alloys upwards. Mean atomic radius separately predicts a0 across all seven alloys.
The Ti-6Al-4V alloy is widely used in aerospace and deep-sea applications due to its exceptional strength and corrosion resistance. However, its application is often constrained by high deformation resistance and a narrow hot-working temperature window, primarily attributed to its heat and mass transfer characteristics. To address these limitations, a novel Ti-6Al-1.3V-0.9Fe alloy was designed with an equivalent molybdenum content. In this study, Gleeble thermal simulation tests were conducted to investigate the impact of Fe on the hot deformation behavior under various conditions and to identify the optimal processing window for this alloy. The effects of deformation temperature and strain rate on the flow stress curves and peak stress were systematically analyzed, along with the role of Fe in microstructural evolution during hot deformation. The results demonstrate that the addition of Fe significantly refines the grain size of the Ti-6Al-1.3V-0.9Fe alloy. As expected, the flow stress decreases with increasing deformation temperature and increases at higher strain rates. Under high-temperature and low-strain-rate conditions, the alloy exhibits steady-state flow behavior, indicating improved hot workability. Based on the constitutive modeling, the apparent activation energy (Q) for hot deformation was calculated to be 503.81 kJ/mol. Finally, the optimal hot-working parameters for the Ti-6Al-1.3V-0.9Fe alloy were identified as a temperature range of 760 °C to 860 °C and a strain rate between 0.01 and 0.16 s−1.
Freeze–thaw cycling can strongly disturb the pore-water environment, soil fabric, and contaminant mobility of heavy-metal-contaminated loess, thereby threatening the long-term effectiveness of stabilization treatments in seasonally frozen regions. This study investigated the coupled hydro-environmental and geotechnical performance of Pb-contaminated loess (untreated control group, CK) treated with microbially induced calcium carbonate precipitation (MICP), graphene (GR)-assisted MICP, and graphene oxide (GO)-assisted MICP under controlled freeze–thaw cycles. One-dimensional consolidation tests, toxicity characteristic leaching procedure (TCLP) tests, zeta-potential measurements, X-ray fluorescence (XRF), and scanning electron microscopy (SEM) were conducted to evaluate compressibility evolution, Pb leaching behavior, interfacial electrochemical characteristics, mineralogical changes, and microstructural mechanisms. After 9 days of mineralization, MICP reduced the Pb leaching concentration from 38.05 to 23.00 mg L−1, achieving a 39.55% reduction compared with untreated Pb-contaminated loess. Freeze–thaw cycling increased the susceptibility of treated loess to structural degradation and pore collapse, especially under medium to high vertical stresses. Nevertheless, the void ratio generally followed the order of CK > MICP > MICP + GR > MICP + GO under comparable loading and freeze–thaw conditions, indicating progressively enhanced resistance to compressive deformation. GR-assisted MICP showed an optimum dosage of approximately 1.0%, beyond which Pb leaching increased because of sheet restacking, agglomeration, and non-uniform biomineralization. In contrast, under up to 13 freeze–thaw cycles, GO-assisted MICP maintained the lowest void ratio and the most stable Pb immobilization performance among all treatments, demonstrating improved resistance against freeze–thaw-induced structural degradation. The results suggest that GO-assisted MICP can simultaneously improve Pb leaching control and soil-fabric stability, providing a promising low-carbon strategy for remediating heavy-metal-contaminated loess exposed to water-mediated freeze–thaw disturbance.
The rapid development of wearable electronics has created a demand for flexible, lightweight, and sustainable power-supply technologies. The persistent temperature difference between the human body and the environment provides a low-grade thermal source for thermoelectric energy harvesting. However, traditional flexible thermoelectric devices still face limited self-supporting capabilities and difficulties in maintaining sufficiently low cold-side temperatures. Here, we designed a passively radiative-cooled thermoelectric film (PRT film) by integrating a PAM/PEDOT:PSS self-supporting thermoelectric composite layer with a polymer metamaterial radiative cooling (PMRC) film. The PAM/PEDOT:PSS layer serves as a self-supporting thermoelectric conversion component for harvesting low-grade heat, while the PMRC film layer acts as a passive cold-side regulator without energy input to lower the cold-side temperature and enhance the temperature gradient. By optimizing the PAM content, the PAM/PEDOT:PSS composite material with 85 wt% PAM achieved the highest power factor of 72.3 μW m−1 K−2. Under a temperature difference of 39 °C, the optimized PAM/PEDOT:PSS sample provided an open-circuit voltage of 0.47 V, a maximum output power of 1.1 μW, and a power density of 11.2 μW cm−2. According to the temperature-difference enhancement measured in experiments and the independently obtained load characteristics, the integration of PMRC films is expected to increase the maximum output power from 1.1 to 1.4 μW, with the corresponding power density rising from 11.2 to 14.25 μW cm−2, representing a 27.2% enhancement. This work demonstrates the feasibility of passive radiative cold-side regulation in enhancing low-level thermoelectric energy harvesting for wearable applications.
Transition metal phosphides (TMPs) have gained significant attention from researchers in the field of catalytic hydrogenation due to their excellent properties. However, existing studies have rarely explored the targeted regulation of the degree of crystal plane exposure of the Ni12P5 catalyst. It is difficult to significantly enhance the performance of this catalyst in the hydrogenation dechlorination (HDC) reaction of trichloroethylene by this strategy. This study proposes a regulatory approach: changing the ratio of ethylene glycol to water to precisely control the exposure ratio of the high-index (312) crystal plane of the Ni12P5 catalyst. Combined with the performance tests of trichloroethylene hydrogenation dechlorination at different reaction temperatures, the intrinsic relationship between the step atoms generated during the formation of the (312) crystal plane and the active sites of the catalyst was clarified. The study also utilized multiple characterization methods such as transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) to conduct a comprehensive property analysis of the prepared catalytic materials.
A comprehensive beyond density functional theory study of the structural, energetic, and electronic properties of the technologically most relevant SiC polytypes 3C, 2H, 4H, and 6H-SiC, together with the single Shockley-type stacking fault (1SSF or 31SSF) in 4H-SiC, was conducted. Lattice constants computed at the PBEsol and HSE06 level match experimental values within 0.1% accuracy. Total energies evaluated at the random-phase approximation level yield a physically consistent hierarchy of polytypes with 3C-SiC as the most stable phase, which is in agreement with low-temperature experimental results. Quasiparticle band gaps computed with both the single-shot G0W0@PBE and the partially self-consistent GW0@PBE formulations quantitatively match well with the experimental values. The band structure of 31SSF reveals fault-induced sub-gap band splitting at the M point of 0.21 eV at the GGA level, which increases to 0.28 eV upon G0W0 correction. To our knowledge, this provides the first GW-level treatment of the 31SSF electronic structure in 4H-SiC. These results collectively provide a many-body perturbation theory (MBPT) level reference dataset for SiC polytypes and the commonly found stacking fault in 4H-SiC.
This study used time-of-flight secondary ion mass spectrometry (TOF-SIMS) to comprehensively analyze the elemental composition, ion distribution, and signal variations in potassium dihydrogen phosphate (KDP) crystals at various sputtering depths after laser irradiation. Positive ion mass spectra were employed to identify the characteristic ions K+, Ca+, Fe+, Si+, and P+. These ions were assigned to their corresponding chemical species. Large-area two-dimensional chemical mapping and maximum count/total count (MC/TC) analysis combined and showed clear depth-dependent trends; all detected ions had significantly higher MC and TC values at larger sputtering depths. At a depth of 1.3 nm, Fe-related and O-related ion signals exhibited overlapping localized hotspots, whereas Ca species showed ring-like enrichment at the edges of the damage pits. These changes are attributed to the laser-induced decomposition of KDP crystals, in which metal inclusions absorb laser energy, generate localized high temperature and pressure, and promote material ejection and ion redistribution. These findings provide direct experimental evidence for understanding laser-induced elemental redistribution in KDP crystals and offer useful guidance for further optimization of their performance.
