Browse Articles

Direct oxidative carbonylation of methane to acetic acid via high-valent iron-oxo mediated water activation

Abstract Direct conversion of CH 4 into value-added chemicals is impeded by the inert C-H bonds and inefficient C-C coupling. We report a spatially separated Rh-O-Fe active-site architecture that decouples CH 4 and H 2 O activation through a high-valent-metal mediated radical mechanism, enabling selective CH 3 COOH synthesis. In-situ infrared, operando Mössbauer spectroscopy, and quasi in-situ high-field EPR reveal that O 2 oxidizes Rh and Fe to high valence states. Rh (III) activates CH 4 to •CH 3 , while Fe (IV)  = O dissociates H 2 O into •OH through a truncated water-gas shift pathway. •OH rapidly reacts with CO to form •COOH intermediates, which couples with •CH 3 within the zeolite to yield CH 3 COOH. This dual-site strategy circumvents kinetic limits of conventional water-gas shift and CO insertion steps. The catalyst achieves 18.2 mmol g cat -1 h -1 CH 3 COOH with 92% selectivity and 100-hour stability in continuous operation. This study establishes radical decoupling enabled by high-valent metal sites as a design principle for selective alkane oxidation.

Low through-plane thermal conductivity in amorphous HfO2/SiO2 nanolaminates

Accurate knowledge of thermal transport in amorphous oxides is essential for effective thermal management in advanced semiconductor and cryogenic electronic devices. In this work, we investigate the through-plane thermal conductivity (κz) of amorphous HfO2/SiO2 nanolaminates fabricated by atomic layer deposition across the temperature range from 30 to 315 K. These multilayers serve as a model system for studying heat transport in amorphous thin films, where interfacial effects may significantly influence thermal conduction. Thermal conductivities were determined using the differential 3ω method and analyzed within the framework of the heat equation. A composite model combining the minimum thermal conductivity approach for the individual amorphous layers with the diffuse mismatch model for interfacial effects quantitatively reproduces the experimental data. The multilayers exhibit low thermal conductivities of 0.77±0.08 and 0.050±0.0015Wm−1K−1 at 300 and 30 K, respectively.

Perivascular mesenchymal cells instruct ST2+ reparative macrophages to promote endovascular injury-induced neointimal hyperplasia in mice

The effect of annealing temperature, concentration of Ni salt, and number of deposition cycles on the size and density of NiSi2 nanocrystals grown from thermal activated diffusion of Ni atoms in single-crystal Si(001) wafers

In this work, we investigate the impact of annealing temperature (320–700 °C), Ni salt concentration in the Ni-doped precursor thin films, and multiple deposition cycles on the morphology and density of endotaxial NiSi2 nanoplates formed near the external surfaces of single-crystal Si(001) wafers. Grazing-incidence small-angle x-ray scattering measurements reveal that, after 2 h of thermal annealing at temperatures above 380 °C, the nanoplates exhibit similar average diameters (∼80 nm) and thicknesses (∼1.8 nm) across all samples, independent of annealing temperature and Ni concentration. We attribute this apparent size self-regulation to strain accumulation at the Si/NiSi2 interface arising from lattice mismatch and/or to the limited extent of stacking-fault edges that serve as preferential nucleation sites. Furthermore, repeated deposition cycles increase the nanoplate density linearly up to eight cycles, beyond which etching-driven SiO2 removal leads to a decrease in their number.

Spatio-spectral light-by-light moulding in multimode fibre

Effect of adding O2 on plasma characteristics of inductively coupled CF4/Ar plasma

High aspect ratio etching is crucial in semiconductor manufacturing, and its improvement relies on the stability and controllability of the plasma. In this study, we combine Langmuir probe diagnostics with a global model to investigate how O2 addition affects plasma characteristics in CF4/Ar radio frequency (RF) inductively coupled discharges. The key operational parameters include the CF4 mixing ratio (binary: 30%–90%, ternary: 10%–40%), working pressure (1–8 Pa), and RF power (200–500 W). The results show that in CF4/Ar discharge, the electron density decreases, whereas the effective electron temperature increases as the CF4 content is raised from 30% to 90%. When O2 is added to the CF4/Ar discharge with the Ar fraction fixed at 50%, the effective electron temperature also increases with the CF4 content in the range 10%–40%, while the electron density remains nearly constant. Analysis of the electron energy probability functions reveals that O2 addition results in low-energy electrons remaining constant with varying CF4 content. Global model calculations further indicate that O2 diversifies the plasma chemical composition and enhances the formation of F and F2 through reactions with CFx. The resulting high density of F2, combined with its large dissociative attachment cross section, makes dissociative attachment to F2 the dominant electron-loss pathway. Furthermore, as the pressure increases from 1 to 8 Pa, the electron density in CF4/Ar discharge exhibits a non-monotonic behavior characterized by an initial increase followed by a decrease. In contrast, it decreases monotonically in O2/CF4/Ar discharge. This work systematically reveals the influence of O2 addition on fluorocarbon plasma characteristics, offering guidance for optimizing plasma etching processes with improved stability and controllability.

Mapping global avian influenza risk patterns through waterbird activity entropy

Nanoscale analysis of MOCVD-grown Mg-doped Al <i>x</i> Ga1− <i>x</i> N/GaN quantum well infrared photodetector (QWIP): Insights into dopant distribution and device performance

Quantum well infrared photodetectors (QWIPs) have emerged as a high-performance and versatile platform for IR detection applications owing to their design flexibility, fast response time, and wavelength tunability across a wide spectral range. While research and development in this field have predominantly focused on GaAs-based QWIPs owing to their mature growth technique and well-understood material properties, III-nitride-based QWIPs can offer potential advantages such as a wider bandgap and strong polarization charges. However, the study of GaN-based QWIPs is still in its early stages and requires further exploration to achieve optimal device performance. Compared to n-QWIPs, p-QWIPs allow for normal-incident absorption, significantly reducing device complexity and size by eliminating the light coupler, which is particularly advantageous for hand-held and imaging applications. We perform detailed atomic-scale characterization of the distribution of Mg acceptors in layers and at interfaces of a Mg-doped AlGaN/GaN p-QWIP grown by metal organic chemical vapor deposition. Device design, device structure growth conditions, and electrical characterization of the QWIP are presented. Initial electrical characterizations revealed a small but noticeable increase in photocurrent upon illumination. We suspect that photoresponsivity (∼μA/W) is highly impacted by low or inefficient Mg incorporation in the QWIP, limiting the carrier population in quantum wells. Atom probe tomography was employed to study the Mg concentration and distribution in the Mg-doped AlGaN/GaN p-QWIP and revealed Mg segregation and clustering in QWIP layers. These findings provide critical insights and pathways to enhance photoresponsivity and overall device performance in QW-based devices that require Mg p-doping.

Estimating firms' emissions from asset level data helps revealing (mis)alignment to net zero targets

Abstract We develop a bottom-up methodology to estimate companies’ (mis)alignment to net-zero scenarios. The approach relies on asset-level data for individual production units, enabling a detailed estimation of corporate emissions trajectories. We apply the methodology to the steel sector globally and find that companies’ projected emissions for 2030 exceed those implied by the International Energy Agency’s (IEA) Net Zero Emissions (NZE) scenario by between 10% and 22%, depending on the assumptions about the future evolution of emission factors of steel production. Further, we find that projected emissions for 2030 exceed companies’ aggregate stated targets, even under the optimistic assumption of electricity supply decarbonization rate following the net-zero scenario, with the gap primarily driven by the largest steel companies. Our results show that a bottom-up asset-level approach allows for a reality check of companies’ contributions to national decarbonization plans. This, in turn, is crucial to inform more targeted industrial policies for decarbonization, and regulatory disclosure.

Digital discovery of distorted-P1 molybdenum ditelluride and its significance in resistive switching

We investigate the intricate polymorphism of 2D molybdenum ditelluride to unveil the elusive distorted metallic phase, which manifests intriguing non-volatile resistive switching. Employing an evolutionary ab initio structure search, we generate 1600 crystal structures and discover 14 unrecognized low-energy polymorphs, including a distorted metallic phase with P1 group symmetry, designated as DP1. This phase closely resembles the previously observed Hd phase in its diffraction pattern, yet it stands out due to its stability and distinct properties. Our comprehensive variable-cell nudged elastic band calculations reveal that the transition from the semiconducting hexagonal phase to DP1 is non-volatile, with charge doping capable of modulating the SET and RESET barriers. Additionally, phonon dispersion analysis and molecular dynamics simulations confirm DP1’s dynamic and structural resilience. Key findings of our study demonstrate that DP1 serves not as a transient, but as a stable, standalone phase with profound implications for memristor technology.

Electric double layer structure in concentrated aqueous solution

An intensive source of soft x-ray radiation based on laser produced plasma of sulfur

An intense source of soft x-ray radiation in the range of the water window and less intense in the range 1.2–15 Å based on sulfur laser plasma is demonstrated at a laser radiation power density on a target in the range of 1.2 × 1013–1014 W/cm2. A comparison with the radiation of nickel plasma showed that for the radiation of sulfur plasma, there is a sevenfold excess in the maximum value of the spectral energy density in the range of the water window. Nevertheless, experiments on recording the spatial distribution of plasma radiation on a streak camera in the spectral range of 1.2–15 Å in both the time-integral and time-scan modes demonstrated a more intense and widespread emission of nickel plasma compared to sulfur plasma emission. It has also been found that the size of the emitting area of the nickel plasma and the duration of the emission in the range mentioned above depend almost linearly on the power density of the laser radiation. A comparison of the experimental emission spectra of sulfur plasma with those calculated using the collisional–radiative model showed that their satisfactory correspondence occurs at an electron temperature of 160 eV and an electron concentration of (1.2–1.3) × 1020 cm−3. The results obtained and the presence of a large amount of sulfur on the planet together can simplify the task of widespread creation of a cheap and effective source of soft x-ray radiation in the spectral range of the water window.

Ballistic transport in nanodevices based on single-crystalline Cu thin films

Influence of transition-metal composition on anomalous Nernst effect in amorphous Tb–Fe–Co thin films

We conducted a comprehensive study on the transition-metal compositional dependence of the anomalous Nernst effect (ANE) in amorphous (amo.) Tb–Fe–Co thin films. The anomalous Nernst coefficient strongly depends not only on the Tb composition but also on the transition metal composition, reaching a maximum of 1.8 μV/K for amo. Tb11.0(Fe50.0Co50.0)89.0. By evaluating the electrical and thermoelectric properties, it was clarified that this maximum is achieved by the superposition of two large contributions: S1 arising from direct transverse electron conduction due to a temperature gradient and S2 resulting from the combined Seebeck and anomalous Hall effects. By examining the transition-metal composition dependence in detail, we discovered that, despite being amorphous structures, the 3d electrons of the transition metal could be sensitively contributing to the ANE and anomalous Hall effect as if they were electron-doped. Our research provides insights for enhancing the ANE in amorphous structures.

In-situ recomposition of polyethyleneimine additive enables a multiprocess long-lifetime thermocell

Tailoring transient flexural-wave propagation in transformed plates

The concept of transformation media has been primarily explored in the monochromatic regime, where device performance can deteriorate when applied to short pulses. Here, we review recent advances in tailoring transient flexural-wave propagation in transformed plates. Using the coordinate-transformation method, we implement practical solutions for a waveshifter, cloak, carpet cloak, and rotator for flexural waves, constructed from alternating thin layers of varying thicknesses within a plate. Time-resolved experiments, supported by full-wave simulations, confirm the effectiveness of these designs in bending, cloaking, and rotating flexural wave pulses while preserving their wavepackets. These results demonstrate how the traditional limitations of dispersion and impedance mismatch in transformed devices can be overcome.

A human cerebral organoid model of West Nile virus encephalitis shows innate immunocompetency

Abstract West Nile virus (WNV), an arbovirus of emerging global interest, can cause neuroinvasive disease in humans. Currently, no protective vaccine or specific treatment is available for human WNV encephalitis. The virus induces neuronal cell death, while astrocytes and microglia cells are suspected to contribute to WNV pathology. Hence, understanding their role is crucial for future treatment approaches. In this study, we establish a WNV encephalitis model using human cerebral organoids, generated with male iPSCs. Infection results in heterogeneous kinetics with an early strong replication potentially leading to viral clearance, while a late peak was associated with more long-term infection. Viral foci are seen in cortical-like areas, rich in neurons and astrocytes, however void of microglia. Pro-inflammatory cytokines (IL-6, TNF-α, IL-18), chemokines (CXCL10, CCL17, CX3CL1, CCL2) and biomarkers (IL-1RA, sTREM-1, sRAGE, BDNF) are increasingly released. Conclusively, human cerebral organoids make suitable WNV encephalitis models with valuable properties to study acute and long-term infection.

A distichous-opposite metamaterial beam and its asymmetric transmission

In this study, we present a novel metamaterial beam with asymmetric wave transmission properties under reciprocal conditions, termed the distichous-opposite metamaterial beam (DOMB), realized through a distichous-opposite arrangement of resonators. Based on the DOMB's mechanical characteristics in each propagation direction, the transfer matrices for forward and backward wave propagation are derived, and corresponding computational models are developed. An experimental test rig is designed and fabricated to investigate the DOMB's bidirectional vibration characteristics. Experimental measurements and transfer matrix method calculations consistently demonstrate that elastic waves exhibit strongly asymmetric transmission in the DOMB. Within specific frequency ranges, forward-propagating waves are significantly suppressed and blocked, while reverse-propagating waves transmit unimpeded, confirming the asymmetric wave transmission characteristics of the metamaterial beam. Analysis of the asymmetric transmission mechanism reveals that the resonators' bending moments act in opposite directions during forward and backward wave propagation, inducing distinct flexural wave responses in the main beam. As a result, a localized vibration mode emerges under backward propagation, but is absent in forward propagation, leading to the observed asymmetric wave transmission in the DOMB. Structural parametric studies reveal that the asymmetric transmission in the metamaterial beams maintains a consistent asymmetric transmission peak frequency under a designated resonator natural frequency, regardless of coupling beam stiffness. The DOMBs produce pronounced asymmetric bands with surrounding broadband gaps under varying unit cell counts, demonstrating stable directional wave control.

DNA Repair gene alterations and efficacy from gemcitabine and nab-paclitaxel with/without durvalumab and tremelimumab in metastatic pancreatic ductal adenocarcinoma

First-principles investigation of ordered structures in zinc blende III–V ternary semiconductors

We systematically investigate the impact of ordered configurations of group III atoms on the formation enthalpy of zinc blende III–V alloys using first-principles calculations. The study focuses on 12 quasibinary systems: AlxGa1−xN, AlxIn1−xN, GaxIn1−xN, AlxGa1−xP, AlxIn1−xP, GaxIn1−xP, AlxGa1−xAs, AlxIn1−xAs, GaxIn1−xAs, AlxGa1−xSb, AlxIn1−xSb, and GaxIn1−xSb. Since the spatial distribution of group III cations in the zinc blende structure is equivalent to that in a face-centered cubic (FCC) lattice, FCC-based ordered phases are employed to compare formation enthalpies across different configurations. For compositions of x = 0.25 and 0.75, we compare the formation enthalpies of three ordered structures—L12, D023, and D022—with those of a random solid solution (RSS), in which group III elements are randomly distributed. At x = 0.5, four ordered structures—L10, L11, Y2, and chalcopyrite—are evaluated in comparison with the RSS structure. Our results reveal that for AlxGa1−xP, AlxGa1−xAs, and AlxGa1−xSb at x = 0.25 and 0.75, the RSS structure exhibits the lowest formation enthalpy, indicating a thermodynamic preference for disordered configurations. In contrast, at x = 0.5, the L11 structure is the most stable for these systems. For the remaining quasibinary systems, the D022 and chalcopyrite structures are energetically favored. However, all minimum formation enthalpies remain positive, suggesting that the ordered phases are thermodynamically metastable across the studied compositions. These findings offer fundamental insights into the relationship between atomistic ordering and formation enthalpy in III–V alloys, thereby providing a theoretical basis for predictive modeling and guiding future experimental efforts in materials design.