Browse Articles

Cryogenic cyclical etching of Si using CF4 plasma passivation steps: The role of CF radicals

Ultraviolet (UV) absorption spectroscopy is used to monitor the CF radical density in CF4 inductively coupled plasma (ICP) plasmas as a function of the substrate temperature. The CF density decreases dramatically when the wafer temperature is reduced from 20 to −130 °C by applying identical plasma conditions, demonstrating that the CF surface sticking coefficient increases as the surface temperature is reduced. This suggests that CF4 plasma could be used to form sidewall passivation layers and perform anisotropic etching at cryogenic temperature, which is impossible at room temperature. Subsequently, a cyclical Bosch type etching process of silicon was evaluated at −100 °C using CF4 plasma to passivate the trench sidewalls. Anisotropic etch profiles were obtained with an etch rate of 4.4 μm/min. Compared to a typical Bosch process using highly polymerizing c-C4F8 plasma, chamber wall contamination could be significantly reduced, alleviating a major issue of this cyclic process. Furthermore, CF4 has a 28% lower global warming potential than c-C4F8.

Metabolic activities are selective modulators for individual segmentation clock processes

Abstract Numerous cellular and molecular processes during embryonic development prompt the fundamental question of how their tempos are coordinated and whether a common global modulator exists. While the segmentation clock tempo scales with the kinetics of gene expression and degradation processes of the core clock gene Hes7 across mammals, the coordination of these processes remains unclear. This study examines whether metabolic activities serve as a global modulator for the segmentation clock, finding them to be selective instead. Several metabolic inhibitions extend the clock period but affect key processes differently: glycolysis inhibition slows Hes7 protein degradation and production delay without altering intron delay, while electron transport chain inhibition extends intron delay without influencing the other processes. Combinations of distinct metabolic inhibitions exhibit synergistic effects. We propose that the scaled kinetics of segmentation clock processes across species may result from combined selective modulators shaped by evolutionary constraints, rather than a single global modulator.

Narrow-linewidth microcavity Brillouin laser based on pump-locked high-Q silica microsphere resonator

Microcavity-based Brillouin lasers are promising high-performance light sources for integrating photonics and optoelectronics. One method to lock the pump light frequency is to utilize a complex system with optoelectronic feedback, which requires a high-cost narrow-linewidth pump laser and limits the application of microlasers in integrated optoelectronic systems. Another method reported recently is all-optical feedback to achieve the locking of microcavity laser. We propose to utilize Rayleigh scattering of microcavities to lock the frequency of the pump laser to the resonant frequency of the Brillouin laser microcavity with the all-optical method. While compressing the linewidth of the pump laser, it can greatly improve the long-term stability of the optically pumped microcavity Brillouin laser. In the experiment, the linewidth of the semiconductor pump laser is compressed from the MHz level to the kHz level. The microcavity Brillouin laser achieves an ultra-narrow intrinsic linewidth of 100 Hz, with an ultra-low frequency noise of 35 Hz2/Hz. The constructed microlaser obtains a locking time up to 1 h, which does not require any temperature control or vibration isolation of the laser system. This work demonstrated an optically pump-locked microcavity Brillouin laser, which provides a stable and reliable low-cost experimental platform for ultra-narrow-linewidth lasers, precision laser sensors, microwave-photonic signal synthesizer, and optomechanical systems.

Asymmetric projection of introspection reveals a behavioural and neural mechanism for interindividual social coordination

Tunable qubit quantum battery with delta-pulse driving

A quantum battery consisting of two coupled qubits driven by a delta-pulse is investigated. By using the framework of open quantum system, we obtain analytically several quantities describing the performance of the quantum battery. In particular, we are interested in the stored energy and the extractable energy known as ergotropy. We discover that by tuning the driving strength and the coupling strength, we can isolate the origin of the ergotropy: quantum coherences, population inversion, or combination of them. Furthermore, increasing the coupling strength not only enhances the stored energy, the ergotropy and charging power, but also reducing the charging time, which boosts the performance of the quantum battery.

Zincophilic CuO as electron sponge to facilitate dendrite-free zinc-based flow battery

The common structure of multiple instability patterns on free liquid surfaces induced by charge injection

A previously disregarded electrohydrodynamic (EHD) instability pattern at the gas–liquid interface caused by charge injection is elaborately described and identified as the classical EHD instability. The characteristics and evolutionary processes of three classic EHD instability patterns were meticulously described experimentally. A Taylor cone-like conical structure is proposed as the common basis for the formation of all these patterns. A direct numerical model based on coupled hydrodynamic and electrodynamic equations is developed, and the evolution of the free liquid surface from static to classical EHD instability patterns is obtained from numerical simulations. The simulation results match the experiments, providing details that cannot be observed experimentally and proving the similarity between the conical structure and the Taylor cone. The comprehensive experimental observations and efficient numerical models can serve as a valuable inspiration and foundation for various applications related to EHD surface instability.

Engineering triple O-Ti-O vacancy associates for efficient water-activation catalysis

Ultrasensitive probing of nematic order parameter via weak measurement

Nematic order parameter S is one of the most crucial material parameters of the nematic phase, which governs all of the material's anisotropic properties. The enhancement of its measurement precision has always been a great concern. In this Letter, a weak measurement scheme with a modified shift pointer is presented to achieve an ultrasensitive probe of S or the director's orientational angle θ. Using this scheme, we have demonstrated a real-time monitoring of the orientational process of cellulose nano-crystal molecules in solutions and measured the orientational direction of polymer nanowires. A typical precision on the order of 10−3 is achieved in the measurement of S and θ. Compared with the current existing techniques, the present scheme not only offers higher measurement precision but also maintains extreme cost-efficiency, thereby holding significance for the research of orientational materials and devices.

Unveiling pelagic-benthic coupling associated with the biological carbon pump in the Fram Strait (Arctic Ocean)

Abstract Settling aggregates transport organic matter from the ocean surface to the deep sea and seafloor. Though plankton communities impact carbon export, how specific organisms and their interactions affect export efficiency is unknown. Looking at 15 years of eDNA sequences (18S-V4) from settling and sedimented organic matter in the Fram Strait, here we observe that most phylogenetic groups were transferred from pelagic to benthic ecosystems. Chaetoceros socialis, sea-ice diatoms, Radiolaria, and Chaetognatha are critical components of vertical carbon flux to 200 m depth. In contrast, the diatom C. socialis alone is essential for the amount of organic carbon reaching the seafloor. Spatiotemporal changes in community composition show decreasing diatom abundance during warm anomalies, which would reduce the efficiency of a diatom-driven biological carbon pump. Interestingly, several parasites are also tightly associated with carbon flux and show a strong vertical connectivity, suggesting a potential role in sedimentation processes involving their hosts, especially through interactions with resting spores, which could have implications for pelagic-benthic coupling and overall ecosystem functioning.

Sub-terahertz PAM4 modulator based on transmission characteristic reconstruction

In this paper, we propose a sub-terahertz PAM4 modulator based on transmission characteristic reconstruction by combining meta-unit, GaAs Schottky diode, and fan branch lines. This method combined the significant electromagnetic resonant characteristics of meta-unit, the high-speed controllability of GaAs Schottky diode, and the high integration of on-chip transmission line together to realize high-speed modulation. Then, we achieve transmission characteristic reconstruction by adjusting the resonance strength under different applied voltages through fan branch lines, enabling high-order amplitude modulation of sub-terahertz waves. The experimental results show that the PAM4 modulation of sub-terahertz waves is achieved with a nearly linear variation of the transmission coefficient in the whole voltage range and a maximum modulation rate of 21 Gbps, providing a promising prospect for the development and application of integrated sub-terahertz direct high-order modulation technology.

Sleeve gastrectomy reveals the plasticity of the human gastric epithelium

Stable magnetocaloric effect over an ultrawide temperature range of 146–320 K via hydrostatic pressure in kagome magnets

Solid-state refrigeration leveraging the magnetocaloric effect (MCE) presents a sustainable and energy-efficient alternative to traditional gas compression refrigeration technologies. However, the practical utility of most magnetocaloric materials is restricted by their narrow operational temperature window. In this work, a stable magnetocaloric effect across an ultrawide temperature range of 146–320 K was achieved in Hf0.85Ta0.15Fe2 magnet via the hydrostatic pressure manipulation. Furthermore, the underlying mechanism for the extended and stable MCEs under hydrostatic pressure has been revealed by magnetization measurements and first-principles calculations. The material systems characterized by strong spin–lattice coupling exhibit considerable potential for externally manipulated hybrid-field-tuned magnetic properties and magnetocaloric performance, providing a convenient and practical approach for advancing applications in magnetic refrigeration technologies.

Room-temperature phosphorescent transparent wood

Investigation of the 4<i>f</i>146<i>s</i>2 1<i>S</i>0−4<i>f</i>135<i>d</i>6<i>s</i>2 (<i>J</i> <b>=</b> 2) clock transition at 431 nm of 171Yb atoms trapped in an optical lattice

With the aid of an optical frequency divider based on an optical frequency comb, the frequency of a laser at 431 nm is divided from a cavity-stabilized laser at 578 nm. Using the frequency-stabilized 431 nm laser, we observe a 2.5 kHz linewidth 4f146s2 1S0−4f135d6s2 (J = 2) transition of 171Yb atoms trapped in an optical lattice. By measuring the lattice-induced frequency shift, we determine the magic wavelength of the optical lattice for the 431 nm transition to be 797.97(20) nm. The frequency of the 431 nm transition is measured to be 695 171 054 856.9(1.1) kHz by referencing to the 1S0−3P0 transition at 578 nm of Yb atoms.

Allylic C–H oxygenation of unactivated internal olefins by the Cu/azodiformate catalyst system

Abstract Allylic ethers and alcohols are essential structural motifs commonly present in natural products and pharmaceuticals. Direct allylic C–H oxygenation of internal alkenes is one of the most direct methods, bypassing the necessity for an allylic leaving group that is needed in the traditional Tsuji–Trost reaction. Herein, we develop an efficient and practical method for synthesizing (E)-allyl ethers from readily available internal alkenes and alcohols or phenols via selective allylic C–H oxidation. Key advances include the use of a Cu/Azodiformate catalyst system to facilitate remote allylic C–H activation and the achievement of excellent chemoselectivity through a dynamic ligand exchange strategy using a bis(sulfonamide) ligand. This method features a broad substrate scope and functional group tolerance, successfully applied to the synthesis of various challenging medium-sized cyclic ethers (7-10 members) and large-ring lactones (14-20 members), with high regioselectivity and stereoselectivity.

Voronoi diagrams metallic mesh for transparent EMI shielding

Recently, the transparent electromagnetic interference (EMI) shielding film, which is optical transparent, conductive, and EMI shielding, is widely employed in fields of display, solar cell, EMI shielding, and so on. Here, we utilized Voronoi diagram randomized metallic mesh and 3D printing technology to achieve transparent EMI shielding on curved surface. For the metal grid based on Voronoi diagram, one can realize highly homogeneous light transmission, with that optical performance is superior to that of regular and random quadrilateral mesh. The designed Voronoi diagram meshes were fabricated using aerosol jet (AJ) technology, which needs no mask and can achieve patterns on curved surfaces. The Voronoi metal meshes were fabricated on a 40 × 40 mm2 planar and a plano–convex lens with a diameter of 10 mm and a crown height of 3.7 mm. We investigated the optical transmittance of the Voronoi metal mesh grid and also the imaging performance of plano–convex lens with mesh grid. Furthermore, we analyzed the EMI shielding characteristics of the fabricated Voronoi mesh grids in the Ku-band (12–18 GHz) by using a vector network analyzer, which is higher than 23 dB. Therefore, the proposed Voronoi diagram and AJ technology can provide good diffraction uniformity and an effective method to fabricate the metal mesh grids on conformal surfaces.

Higher magnesium depletion score increases the risk of all‑cause and cardiovascular mortality in US adults with diabetes

Background Both dietary magnesium and serum magnesium are associated with the prognosis of diabetic patients. However, the impact of the magnesium depletion score (MDS), which assesses systemic magnesium deficiency, on the prognosis of diabetic patients remains unclear. This cohort study aims to explore the potential association between the MDS and all-cause and cardiovascular mortality in diabetic patients. Methods In this study, we analyzed data from 5,219 diabetic individuals from National Health and Nutrition Examination Survey (NHANES) 2003–2018. Participant mortality information was sourced from the National Death Index records. MDS was divided into lower MDS (0–1 points), middle MDS (2 points), and higher MDS (3–5 points) groups. Weighted multivariable Cox regression was utilized to explore the potential association between MDS and mortality in diabetic patients. Stratified analyses and sensitivity analyses were employed to validate the robustness of our findings. Results Among the 5,219 participants included in this study, 1,212 experienced all-cause mortality, and 348 experienced cardiovascular mortality. Weighted multivariable Cox regression indicated that higher MDS was strongly linked to a heightened risk of mortality in all models, including the fully adjusted model (all-cause mortality: HR = 1.58, 95% CI: 1.20–2.08; cardiovascular mortality: HR = 1.92, 95% CI: 1.28–2.88). In the stratified analysis, we found that the association between MDS and all-cause mortality was stronger among individuals aged &lt;60 years. No significant differences were found in the relationship between MDS and mortality within other subgroups. In the sensitivity analyses, our results remained robust. Conclusions An increase in MDS is significantly correlated with a higher risk of all-cause and cardiovascular mortality in diabetic patients. The risk of all-cause mortality was higher in diabetic patients aged &lt;60. Early monitoring and management of MDS, as well as optimizing magnesium nutritional status, may benefit diabetic patients.

Increasing certainty in projected local extreme precipitation change

Sub-cycle nanotip field emission of electrons driven by air plasma generated THz pulses

Terahertz pulses generated by two-color laser plasmas have reported peak field strengths exceeding MV/cm, and when illuminating metal nanotips, the near-field enhancement at the tip apex should result in extremely high bunch charges and electron energies via sub-cycle cold-field emission. Here, electron emission from tungsten nanotips driven by THz pulses generated by a long filament air-plasma is reported. Electron energies up to 1.1 keV and bunch charges up to 2×105 electrons per pulse were detected, well below values expected for peak field calculated via the time-averaged Poynting vector. Investigations revealed a failure in the use of the time-averaged Poynting vector when applied to long filament THz pulses, due to spatiotemporal restructuring of the THz pulse in the focus. Accounting for this restructuring significantly reduces the field strength to approximately 160 kV/cm, consistent with the observed electron bunch charges, peak energies, and their dependence on the tip position in the THz focus. Despite these findings, our results surpass previous THz plasma-driven electron generation by an order of magnitude in both electron energy and bunch charge, and a path to increasing these by an additional order of magnitude by modification of the THz optics is proposed.