bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevention and characterization of thin film defects induced by contaminant aggregates in initiated chemical vapor deposition
Authors: Shindler Simon , Franklin Trevor , Yang Rong
Published: April 2024

As initiated Chemical Vapor Deposition (iCVD) finds increasing application in precision industries like electronics and optics, defect prevention will become critical. While studies of non-ideal morphology exist in the iCVD literature, no studies investigate the role of defects. To address this knowledge gap, we show that the buildup of short-chain polymers or oligomers during normal operation of an iCVD reactor can lead to defects that compromise film integrity. We used atomic force microscopy to show that oligomer aggregates selectively prevented film growth, causing these hole-like defects. X-ray diffraction and optical microscopy demonstrated the crystallinity of the aggregates, pointing to a flat-on lamellar or mono-lamellar structure. To understand the origin of the aggregates, spectroscopic ellipsometry showed that samples exposed to the reactor consistently accrued low-volatility contaminants. X-ray photoelectron spectroscopy revealed material derived from polymerization in the contamination, while scanning electron microscopy showed the presence of defect-causing aggregates. We directly linked oligomeric/polymeric contamination with defect formation by showing an increased defect rate when a contaminant polymer was heated alongside the sample. Most importantly, we showed that starting a deposition at a high sample temperature (e.g., 50 °C) before reducing it to the desired setpoint (e.g., 9 °C) unilaterally prevented defects, providing a simple method to prevent defects with minimal impact on operations.
Compact high-Q Ka-band sapphire distributed Bragg resonator
Authors: Iltchenko Vladimir , Wang Rabi , Toennies Michael , Matsko Andrey
Published: April 2024

In a class of high quality (Q-) factor dielectric resonators with low radiative losses, including popular whispering-gallery mode (WGM) resonators with high azimuthal mode numbers, due to high confinement of modal field in dielectric, the Q-factor is limited by the value of inverse dielectric loss tangent of dielectric material. Metal enclosures necessary for device integration only marginally affect the Q-factor while eliminating the residual radiative loss and allowing the optimization of input and output coupling. While very high Q-factors ∼200000 are available in sapphire WGM resonators in X-band, at millimeter wave frequencies increasing dielectric loss limits the Q-factor to much smaller values, e.g. ∼50000 and ∼25000 for quasi-TE and quasi-TM modes, correspondingly, at 36 GHz. The use of distributed Bragg reflection (DBR) principle allows to push modal energy outside dielectric while also isolating it from Joule losses in metallic enclosure walls. Very high Q∼600000>tgδ has been demonstrated in X-band [C. A. Flory and R. C. Taber, IEEE Trans. Ultrason., Ferroelectr., Freq. Control 44, 486–495 (1997).] at the expense of impractically large dimensions. In this work, we report on the assembly and testing of a compact Ka-band sapphire distributed Bragg reflector cavity characterized with Q-factor seven times larger than one predicted by the material’s dielectric loss at the frequency of interest. An intrinsic Q-factor of ∼200000 is demonstrated at 36 GHz for the lowest order TM-mode of a sapphire DBR. The resonator has 50 cm3 volume, smaller than previously demonstrated DBRs.
Generalized Born–Huang expansion under macroscopic quantum electrodynamics framework
Authors: Tsai Hung-Sheng , Shen Chih-En , Hsu Liang-Yan
Published: April 2024

Born–Huang expansion is the cornerstone for studying potential energy surfaces and non-adiabatic couplings (NACs) in molecular systems. However, the traditional approach is insufficient to describe the molecular system, which strongly interacts with quantum light. Inspired by the work by Schäfer et al., we develop the generalized Born–Huang expansion theory within a macroscopic quantum electrodynamics (QED) framework. The theory we present allows us to describe electromagnetic vacuum fluctuations in dielectric media and incorporate the effects of dressed photons (or polaritons) into NACs. With the help of the generalized Born–Huang expansion, we clearly classify electronic nuclear NACs, polaritonic nuclear NACs, and polaritonic electronic NACs. Furthermore, to demonstrate the advantage of the macroscopic QED framework, we estimate polaritonic electronic NACs without any free parameter, such as the effective mode volume, and demonstrate the distance dependence of the polaritonic electronic NACs in a silver planar system. In addition, we take a hydrogen atom in free space as an example and derive spontaneous emission rates from photonic electronic NACs (polaritonic electronic NACs are reduced to photonic electronic NACs). We believe that this work not only provides an avenue for the theoretical exploration of NACs in a nucleus–electron–polariton coupled system but also offers a more comprehensive understanding for molecules coupled with quantum light.
Numerical simulation of the simultaneous propagation of multiple hydraulic fractures based on expanded finite element method
Authors: Chu Jinqi , Li Minghui , Huang Guopeng , Guo Tiankui , Zhou Fujian
Published: April 2024

Hydraulic fracturing technology with horizontal wells is a highly efficient approach to stimulate the unconventional reservoir by creating lots of fractures to increase the oil and gas recovery rate. However, some field monitoring data indicate that multiple fractures could not propagate uniformly due to stress interference, which leads to a lower stimulation volume and production capacity. Therefore, investigating the stress interference mechanism between multiple fractures is important to obtain a higher production capacity for unconventional reservoirs. In this study, a two-dimensional XFEM (expanded finite element method) model was established to investigate the influence of stress interference on the fracture propagation of multiple fractures in horizontal wells. The different injection parameters, completion parameters, and fracturing patterns were investigated by sixteen simulation cases. The results show that first the influencing degree of stress interference from different parameters is fracture spacing, injection flow rate, number of fractures, and fluid viscosity, respectively. Second, compared to the simultaneous fracturing and sequential fracturing, the zip fracturing pattern (sides fractures created first and then mid-fracture) could create more uniform fractures in the reservoir. Third, a small fracture spacing and a higher injection flow rate could lead to a faster stress interference, but the fluid viscosity and the number of fractures have little effect on the occur timing of stress interference. This study could provide some meaningful perspective on the field fracturing design in horizontal wells.
Multimode thermoacoustic system for heating and cooling
Authors: Hu Yiwei , Wang Benlei , Wu Zhanghua , Hu Jianying , Luo Ercang , Xu Jingyuan
Published: April 2024

Thermoacoustic technology emerges as a sustainable and low-carbon method for energy conversion, leveraging environmentally friendly working mediums and independence from electricity. This study presents the development of a multimode heat-driven thermoacoustic system designed to utilize medium/low-grade heat sources for room-temperature cooling and heating. We constructed both a simulation model and an experimental prototype for a single-unit direct-coupled thermoacoustic system, exploring its performance in heating-only, cooling-only, and hybrid heating and cooling modes. Internal characteristic analysis including an examination of internal exergy loss and a distribution analysis of key parameters was first conducted in the hybrid cooling and heating mode. The results indicated a positive-focused traveling-wave-dominant acoustic field within the thermoacoustic core unit, enhancing energy conversion efficiency. The output system performance was subsequently tested under different working conditions in the heating-only and cooling-only modes. A maximum output heating power of 2.3 kW and a maximum COPh of 1.41 were observed in the heating-only mode. Meanwhile, a cooling power of 748 W and a COPc of 0.4 were obtained in the typical cooling condition at 7 °C when operating in cooling-only mode. These findings underscore the promising potential of thermoacoustic systems for efficiently utilizing medium/low-grade heat sources for cooling and/or heating applications in the future.
Synchronization dynamics of phase oscillators on power grid models
Authors: Potratzki Max , Bröhl Timo , Rings Thorsten , Lehnertz Klaus
Published: April 2024

We investigate topological and spectral properties of models of European and US-American power grids and of paradigmatic network models as well as their implications for the synchronization dynamics of phase oscillators with heterogeneous natural frequencies. We employ the complex-valued order parameter—a widely used indicator for phase ordering—to assess the synchronization dynamics and observe the order parameter to exhibit either constant or periodic or non-periodic, possibly chaotic temporal evolutions for a given coupling strength but depending on initial conditions and the systems’ disorder. Interestingly, both topological and spectral characteristics of the power grids point to a diminished capability of these networks to support a temporarily stable synchronization dynamics. We find non-trivial commonalities between the synchronization dynamics of oscillators on seemingly opposing topologies.
A wideband high-gain dielectric resonator antenna based on mullite microwave dielectric ceramics
Authors: Du Chao , Bao Ziyan , Chen Hetuo , Zhou Guohong , Pang Yongqiang , Liu Haiwen , Jiang Huangfu , Zhou Tao , Xia Song , Zhou Di
Published: April 2024

In this paper, the high-quality factor mullite microwave dielectric ceramic is employed to introduce in dielectric resonator antenna (DRA). The microwave dielectric properties of ɛr ∼ 5.8, Q × f ∼ 31 240 at 9.66 GHz, and loss tangent tanδ = 1/Q ∼ 2.7 × 10−4 can be obtained by the solid-state reaction method in mullite microwave dielectric ceramic sintered at 1700 °C. On this basis, the resonant modes of the proposed broadband high-gain rectangular DRA are analyzed by using a dielectric waveguide theoretical model and the antenna performance is evaluated by a commercial CST Microwave Studio 2021® software. It has been found that the proposed rectangular DRA can provide a broad bandwidth of 35.9%, a maximum gain of 10 dBi at 3.61 GHz, and a radiation efficiency of 90% in the range of 3.13–4.42 GHz. For demonstration, adequate consistency between the simulation results and the measurement results was achieved. The proposed DRA has great application potential and value in 5G communication scenarios requiring wideband and high-gain antenna.
Optical and transport properties of plasma mixtures from ab initio molecular dynamics
Authors: White Alexander J. , Craven Galen T. , Sharma Vidushi , Collins Lee A.
Published: April 2024

Predicting the charged particle transport properties of warm dense matter/hot dense plasma mixtures is a challenge for analytical models. High accuracy ab initio methods are more computationally expensive, but can provide critical insight by explicitly simulating mixtures. In this work, we investigate the transport properties and optical response of warm dense carbon–hydrogen mixtures at varying concentrations under either conserved electronic pressure or mass density at a constant temperature. We compare options for mixing the calculated pure species properties to estimate the results of the mixtures. We find that a combination of the Drude model with the Matthiessen's rule works well for DC electron transport and low-frequency optical response. This breaks down at higher frequencies, where a volumetric mix of pure-species AC conductivities works better.
An analytic descriptor for determining the effect of grain-boundary structures of metals on solute segregation
Authors: Li Xin , Li Yujun , Gao Wang
Published: April 2024

The structure of grain boundaries (GBs) of metals is essential in determining the solute segregation at GBs; however, its complexity prohibits the understanding of the underlying mechanism. We propose a geometric descriptor of GB segregation based on the non-local coordination number of cut surfaces from GBs, which determines the segregation energies of solutes at the grain boundaries of metals across multidimensional GB space, different solutes, and different matrices. The effectiveness of the descriptor originates from the correlation between bonding strength, d-band width, and coordination number. This descriptor only depends on the bond length and angle of pre-segregation sites at GBs and can be readily used for description and prediction. Our scheme builds a novel picture for understanding the role of GB structures in segregation and provides a useful tool for the design of advanced alloys.
Improved hybrid approach of monotonic upstream-centered scheme for conservation laws and discontinuity sharpening technique for steady and unsteady flows
Authors: Fukushima Gaku , Kitamura Keiichi
Published: April 2024

In finite-volume methods, monotonic upstream-centered schemes for conservation laws (MUSCL) offer second-order spatial accuracy but tend to produce highly dissipative solutions for density discontinuity and weak shock waves. To address this limitation within a second-order framework, a novel strategy for hybridizing MUSCL with the tangent of the hyperbola interface capturing technique for both steady and unsteady compressible flows is presented. This hybridization optimizes the process based on the degree of nonlinearity and discontinuity around the target cells, providing a novel method to sharply resolve weak shock waves and robustly compute strong shock waves within the hybrid scheme. The proposed scheme sharply captures exceedingly weak shock waves that conventional MUSCL fails to resolve accurately due to excessive numerical dissipation. Furthermore, for resolving small vortices induced by instability at slip lines, computational results demonstrate high-resolution surpassing fifth-order spatial accuracy schemes within this second-order spatial accuracy framework with less computational cost. Moreover, the scheme exhibits commendable convergence and robustness when applied to steady-state problems featuring strong shock waves. This scheme offers a more precise and high-resolution alternative to conventional MUSCL for compressible flow computations, as it requires no additional stencil for reconstruction, unlike conventional fifth-order schemes.
Amplitude and phase modulation with electric quadrupole radiation
Authors: Zhang Jiawei , Shi Weijie , Liu Andong , Tang Lili , Zhang Shuyan , Dong Zhenggao
Published: April 2024

Optical metasurfaces can be used to realize various peculiar optical effects, and their mechanisms of the controlling optical phase can be roughly categorized into three types: resonant phase, geometric phase, and propagation phase, also known as the dynamic phase. Multiple mechanisms can be employed to manipulate the phase and amplitude of one metasurface. Therefore, discovering more profound and diverse methods can provide additional degrees of application freedom. This paper proposes a control principle based on electric multipole expansion. We found that for a unit structure formed by dual-metal bars on a metasurface, the radiation of its dipole is equivalent to the interference results of the dual-metal bars. Moreover, the radiation of the quadrupole enables independent control for amplitude and phase. Therefore, we used quadrupole radiation to manipulate the phase and amplitude of the light and even investigated some simple applications, including the realization of focusing light and anomalous refraction. Such a new mechanism of controlling light, combined with other methods, can provide significant insights into achieving challenging goals, like steganography and multifunctional metasurfaces.
Analysis of multi-bubble pulsations by the finite element method and bubble dynamics equations
Authors: Wang Yu , Chen Dehua , Wu Pengfei , Li Jiahui
Published: April 2024

Bubbles are widely used in industrial production, biomedical engineering, and many other fields. The analysis of the response of bubble clusters under acoustic waves is significant for the application of bubbles. In this paper, different bubble dynamics models are used to calculate the instantaneous radius of multi-bubbles, and the results corresponding to the different models are compared with those by the finite element method. In addition, the effect of bubble interactions on bubble pulsation is analyzed at different distances, and the effect of incident acoustic direction on the bubble's instantaneous radius is also investigated. The results show that time delays, which have often been neglected in previous work, should be considered except when the bubble spacing is minimal. The results calculated by the finite element method indicate that the attraction and repulsion between bubbles are alternating, which is related to the velocity field between bubbles. Moreover, the suppression or promotion of bubble interactions for bubble pulsation is affected by bubble distance under the same acoustic excitation conditions. Finally, for a bubble cluster with large bubble distances, its total scattered field relating to the incident acoustic wave can be approximated as the interference field of multiple secondary acoustic sources with the same waveform and different phases. If these bubbles are in random motion, the total scattered sound intensity of the bubble cluster is proportional to the number of bubbles.
QED in space–time varying materials
Authors: Pendry J. B. , Horsley Simon A. R.
Published: April 2024

Space–time variation spoils frequency conservation and brings negative frequencies into the picture. In addition, the quantum nature of light comes to the fore in a manner not evident in static systems. Here, we explore the quantum structure of these systems; propose a Hamiltonian; show that, in the Heisenberg picture, quantum field operators evolve according to classical equations; and discuss the uniquely quantum phenomenon of photon-pair creation.
Permutation entropy analysis of EEG signals for distinguishing eyes-open and eyes-closed brain states: Comparison of different approaches
Authors: Gancio Juan , Masoller Cristina , Tirabassi Giulio
Published: April 2024

Developing reliable methodologies to decode brain state information from electroencephalogram (EEG) signals is an open challenge, crucial to implementing EEG-based brain–computer interfaces (BCIs). For example, signal processing methods that identify brain states could allow motor-impaired patients to communicate via non-invasive, EEG-based BCIs. In this work, we focus on the problem of distinguishing between the states of eyes closed (EC) and eyes open (EO), employing quantities based on permutation entropy (PE). An advantage of PE analysis is that it uses symbols (ordinal patterns) defined by the ordering of the data points (disregarding the actual values), hence providing robustness to noise and outliers due to motion artifacts. However, we show that for the analysis of multichannel EEG recordings, the performance of PE in discriminating the EO and EC states depends on the symbols’ definition and how their probabilities are estimated. Here, we study the performance of PE-based features for EC/EO state classification in a dataset of N=107 subjects with one-minute 64-channel EEG recordings in each state. We analyze features obtained from patterns encoding temporal or spatial information, and we compare different approaches to estimate their probabilities (by averaging over time, over channels, or by “pooling”). We find that some PE-based features provide about 75% classification accuracy, comparable to the performance of features extracted with other statistical analysis techniques. Our work highlights the limitations of PE methods in distinguishing the eyes’ state, but, at the same time, it points to the possibility that subject-specific training could overcome these limitations.
2D electron gas formation on InAs wurtzite nanosheet surfaces
Authors: Benter S. , Bianchi M. , Pan D. , Zhao J. , Xu H. Q. , Timm R. , Hofmann Ph. , Mikkelsen A.
Published: April 2024

The two-dimensional electron gas (2DEG) that forms on a semiconductor surface can be used to explore a variety of phenomena in quantum physics and plays an important role in nanoscale electronics, such as transistors. Controlling its formation is, thus, relevant. Using angle-resolved photoemission spectroscopy (ARPES) and accumulating the signal over many nanocrystals, we find that on clean InAs nanosheets with non-polar surfaces and wurtzite (WZ) crystal structures, a 2DEG can be observed at the Γ-point. We suggest that the step morphology on the WZ InAs specimens facilitates the appearance of the electron gas, since previous studies on InAs nanowire surfaces with the same crystal facet and a similar defect density did not exhibit a 2DEG. Subsequently, bismuth deposition leads to the disappearance of the 2DEG as well as a shift of the valence band. This is in contrast to previous observations on InAs surfaces, in which metal deposition would lead to the formation of a 2DEG. The control of the 2DEG with the addition of Bi atoms is relevant for applications of InAs nanosheets in quantum technologies. This study also illustrates that ARPES accumulated over several 2D materials oriented randomly around their normal axis can provide valuable information on their band structure with a fast turnover and low irradiation.
Using leeward air-blowing to alleviate the aerodynamic lateral impact of trains at diverse yaw angles
Authors: Guo Zi-Jian , Chen Zheng-Wei , Che Zheng-Xin , Bordbar Amir , Ni Yi-Qing
Published: April 2024

The safety risks of high-speed trains in crosswind environments escalate with increasing train speeds. The present study employs the improved delayed detached eddy simulation method based on the shear stress transport k–ω turbulence model to evaluate an active control method targeting the reduction of lateral forces acting on the train. The effects of air blowing strategy on the leeward side of the train are examined considering different yaw angles and blowing speeds. The findings reveal that the active air blowing, mixed with the flow laterally downstream the train roof, induces the increase in the local turbulence and alters the surface pressure distribution. Within the investigated range of yaw angles, the active air blowing yields a lateral force reduction ranging from 1.0% to 8.8%. Varying the blowing speed can further decrease the lateral force of the entire train by 5.9% and 0.8% at yaw angles of 15° and 75°, respectively. The power invested in active blowing demonstrates maximum returns at a yaw angle near 45° while diminishing with increasing blowing speed.
Poling induced changes in polarization domain structure of polymer ferroelectrics for application in organic thin film transistors
Authors: Ghobadi Arash , Niavol Somayeh Saadat , Restuccia Evan , Meng Andrew C. , Guha Suchismita
Published: April 2024

While electrical poling of organic ferroelectrics has been shown to improve device properties, there are challenges in visualizing accompanying structural changes. We observe poling induced changes in ferroelectric domains by applying differential phase contrast (DPC) imaging in the scanning transmission electron microscope, a method that has been used to observe spatial distributions of electromagnetic fields at the atomic scale. In this work, we obtain DPC images from unpoled and electrically poled polyvinylidene fluoride trifluorethylene films and compare their performance in polymer thin film transistors. The vertically poled films show uniform domains throughout the bulk compared to the unpoled film with a significantly higher magnitude of the overall polarization. Thin film transistors comprising a donor–acceptor copolymer as the active semiconductor layer show improved performance with the vertically poled ferroelectric dielectric film compared with the unpoled ferroelectric dielectric film. A poling field of 80–100 MV/m for the dielectric layer yields the best performing transistors; higher than 100 MV/m is seen to degrade the transistor performance. The results are consistent with a reduction in deleterious charge carrier scattering from ferroelectric domain boundaries or interfacial dipoles arising from electrical poling.
Low experimental thermal conductivity of zirconium metal-organic framework UiO-66
Authors: Lai Hoa Thi , Tran Nhat Quang Minh , Nguyen Linh Ho Thuy , Le Thu Bao Nguyen , Nguyen Cuong Chi , Pham Anh Tuan Thanh , Doan Tan Le Hoang , Park Sungkyun , Hong Jongill , Snyder Gerald Jeffrey , Phan Thang Bach
Published: April 2024

Using laser flash analysis, the low thermal conductivity of the pressed Zirconium metal-organic framework (UiO-66) powder pellet was obtained. As a result, the density ρ, thermal diffusivity α, specific heat capacity cP, and low thermal conductivity κexp of the pressed UiO-66 powder pellet at 300 K are observed to be 1.258 g/cm3, 0.001 59 cm2/s, 0.7765 J/g K, and 0.156 W/m K, respectively. Due to the presence of the 12-coordinated nodes with six transfer pathways, the thermal transport of the UiO-66 particles is preferred through linkers to metal sites. The low thermal conductivity follows the trend of vacuum < argon (Ar) < air < helium (He) since the entrapped gas molecules provide additional heat transfer channels inside the particles and between the particles. The low thermal conductivity along with a weak temperature-dependent thermal conductivity are elucidated in terms of boundary scattering.
Simulating charged defects at database scale
Authors: Shen Jimmy-Xuan , Voss Lars F. , Varley Joel B.
Published: April 2024

Point defects have a strong influence on the physical properties of materials, often dominating the electronic and optical behavior in semiconductors and insulators. The simulation and analysis of point defects is, therefore, crucial for understanding the growth and operation of materials, especially for optoelectronics applications. In this work, we present a general-purpose Python framework for the analysis of point defects in crystalline materials as well as a generalized workflow for their treatment with high-throughput simulations. The distinguishing feature of our approach is an emphasis on a unique, unit cell, structure-only, definition of point defects which decouples the defect definition, and the specific supercell representation used to simulate the defect. This allows the results of first-principles calculations to be aggregated into a database without extensive provenance information and is a crucial step in building a persistent database of point defects that can grow over time, a key component toward realizing the idea of a “defect genome” that can yield more complex relationships governing the behavior of defects in materials. We demonstrate several examples of the approach for three technologically relevant materials and highlight current pitfalls that must be considered when employing these methodologies as well as their potential solutions.
Influence of reservoir physical properties on guar gum fracturing fluid damage in unconventional tight reservoirs
Authors: Chen Luojun , Gong Runpu , Wang Jie , Xu Hualei , Zhang Liangjun
Published: April 2024

Solid phase residue, fracturing fluid filtration, and incomplete backflow during hydraulic fracturing can easily cause damage to tight sandstone reservoir. Thus, it is necessary to explore the relationship between the physical properties of tight reservoirs and damage caused by fracturing fluids. Based on the identification of reservoir physical properties, the relationship between reservoir physical properties and fracturing fluid damage was studied by core displacement, computerized tomography, and nuclear magnetic resonance (NMR). The results show that the higher the clay mineral content is, the denser the formed core is, and the corresponding core porosity and permeability are lower. When the permeability and porosity of the rock core are relatively high, the overall radius of the pore throat in the rock core shifts to the left under the action of the gel breaking fracturing fluid, showing a decreasing trend. However, when the permeability and porosity of the rock core are relatively low, the frequency peak of the smaller size of the pore throat in the rock core under the action of the gel breaking fracturing fluid increases upwards. The corresponding core permeability decline rate of the two types of tight sandstone reservoirs is 9.91%–8.78% and 15.85%–14.74%. The porosity decline rates are 5.53%–5.84% and 10.40%–9.94%. According to NMR results, it is speculated that under the action of gel breaking fracturing fluid, the small pore throats in the rock core are blocked or even disappear, while the proportion of smaller pore throats increases and the proportion of larger pore throats decreases. The results of this study provide theoretical reference for reservoir protection during the fracturing process of tight sandstone reservoirs.
Thermal excitation-induced micro/nano fabrication and material modification of superconducting Nb films
Authors: Shi Zejun , Zhang Haohui , Zhou Han , Wu Yao , Zhao Lianjun , Zhang Deheng , Huang Yicong , Lin Jianxin
Published: April 2024

We report the thermal excitation-induced material modification and micro/nano fabrication based on the interactions between nano laser direct writing (NLDW) and superconducting films experimentally and by simulation. The niobium (Nb) films with a critical temperature of 9 K were deposited on silicon substrate via sputtering with the thickness of around 50 nm. The boundary between material modification and micro/nano fabrication was verified by changing the interaction time and laser power continuously. Specifically, as the laser power was fixed at 250 mW and the interaction time below 440 ns, the interaction is material modification. With the increasing interaction time further, the Nb films were etched away. As the interaction time was fixed at 500 ns and the laser power below 200 mW, the interaction is material modification too. With the increasing of laser power further, the Nb films were etched away. In the experiment, the oxygen content and current–voltage characteristic (IVCs) before and after laser irradiation were displayed to verify the material modification, which is in line with the simulation results. Considering the 50 nm resolution of NLDW, in the material modification region, one could trim trilayer junctions, tune shunt resistors, or adjust critical currents, etc. In the micro/nano fabrication region, one could fabricate various devices and exploit the properties of high spatial resolution, high flexibility, and fast processing.
Genomic population structure of great hammerhead sharks (Sphyrna mokarran) across the Indo-Pacific
Authors: Brunjes Naomi L. , Williams Samuel M. , Levengood Alexis L. , Broadhurst Matt K. , Raoult Vincent , Harry Alastair V. , Braccini Matias , Green Madeline E. , Spaet Julia L. Y. , Travers Michael J. , Holmes Bonnie J.
Published: April 2024

Context Currently, little information exists describing the population structure of great hammerhead sharks (Sphyrna mokarran) in Australian waters. Aims This study used single nucleotide polymorphisms to investigate fine-scale population structure in S. mokarran across the Indo-Pacific. Methods DNA was extracted from 235 individuals across six Australian locations and a Red Sea outgroup. Population parameters were calculated and visualised to test structuring across locations. Key results No fine-scale population structuring was observed for S. mokarran across the Indo-Pacific. However, population structuring occurred for all Australian locations when compared to the Red Sea outgroup. Conclusions Findings suggest a single stock is most likely for S. mokarran found in Australian waters. Results provide key information for understanding the broad range movements of S. mokarran and help to define the scale of management required to preserve genetic diversity in this species. The structuring between Australia and the Red Sea indicates limited gene flow and movement. Implications Results indicate that large-scale movements of S. mokarran could be occurring to facilitate genetic mixing. Future research focusing on individual tagging to corroborate movements would be highly beneficial to determine how far (and often) individuals are dispersing, and to note where cross-jurisdictional management, including from neighbouring regions in the Indo-West Pacific–Oceania region, are most critical.
Evolutionary and developmental specialization of foveal cell types in the marmoset
Authors: Zhang Lin , Cavallini Martina , Wang Junqiang , Xin Ruiqi , Zhang Qiangge , Feng Guoping , Sanes Joshua R. , Peng Yi-Rong
Published: April 2024

In primates, high-acuity vision is mediated by the fovea, a small specialized central region of the retina. The fovea, unique to the anthropoid lineage among mammals, undergoes notable neuronal morphological changes during postnatal maturation. However, the extent of cellular similarity across anthropoid foveas and the molecular underpinnings of foveal maturation remain unclear. Here, we used high-throughput single-cell RNA sequencing to profile retinal cells of the common marmoset (
Callithrix jacchus
), an early divergent in anthropoid evolution from humans, apes, and macaques. We generated atlases of the marmoset fovea and peripheral retina for both neonates and adults. Our comparative analysis revealed that marmosets share almost all their foveal types with both humans and macaques, highlighting a conserved cellular structure among primate foveas. Furthermore, by tracing the developmental trajectory of cell types in the foveal and peripheral retina, we found distinct maturation paths for each. In-depth analysis of gene expression differences demonstrated that cone photoreceptors and Müller glia (MG), among others, show the greatest molecular divergence between these two regions. Utilizing single-cell ATAC-seq and gene-regulatory network inference, we uncovered distinct transcriptional regulations differentiating foveal cones from their peripheral counterparts. Further analysis of predicted ligand–receptor interactions suggested a potential role for MG in supporting the maturation of foveal cones. Together, these results provide valuable insights into foveal development, structure, and evolution.
USP8-governed GPX4 homeostasis orchestrates ferroptosis and cancer immunotherapy
Authors: Li Haiou , Sun Yishuang , Yao Yingmeng , Ke Shanwen , Zhang Nannan , Xiong Wenjun , Shi Jie , He Chuan , Xiao Xiangling , Yu Haisheng , Dai Panpan , Xiang Bolin , Xing Xixin , Xu Gaoshan , Song Wenjing , Song Jiquan , Zhang Jinfang
Published: April 2024

Ferroptosis is an iron-dependent type of regulated cell death resulting from extensive lipid peroxidation and plays a critical role in various physiological and pathological processes. However, the regulatory mechanisms for ferroptosis sensitivity remain incompletely understood. Here, we report that homozygous deletion of
Usp8
(ubiquitin-specific protease 8) in intestinal epithelial cells (IECs) leads to architectural changes in the colonic epithelium and shortens mouse lifespan accompanied by increased IEC death and signs of lipid peroxidation. However, mice with heterozygous deletion of
Usp8
in IECs display normal phenotype and become resistant to azoxymethane/dextran sodium sulfate–induced colorectal tumorigenesis. Mechanistically, USP8 interacts with and deubiquitinates glutathione peroxidase 4 (GPX4), leading to GPX4 stabilization. Thus, USP8 inhibition destabilizes GPX4 and sensitizes cancer cells to ferroptosis in vitro. Notably, USP8 inhibition in combination with ferroptosis inducers retards tumor growth and enhances CD8
+
T cell infiltration, which potentiates tumor response to anti-PD-1 immunotherapy in vivo. These findings uncover that USP8 counteracts ferroptosis by stabilizing GPX4 and highlight targeting USP8 as a potential therapeutic strategy to boost ferroptosis for enhancing cancer immunotherapy.
Label-free and amplification-free viral RNA quantification from primate biofluids using a trapping-assisted optofluidic nanopore platform
Authors: Sampad Mohammad Julker Neyen , Saiduzzaman S. M. , Walker Zach J. , Wells Tanner N. , Wayment Jesse X. , Ong Ephraim M. , Mdaki Stephanie D. , Tamhankar Manasi A. , Yuzvinsky Thomas D. , Patterson Jean L. , Hawkins Aaron R. , Schmidt Holger
Published: April 2024

Viral outbreaks can cause widespread disruption, creating the need for diagnostic tools that provide high performance and sample versatility at the point of use with moderate complexity. Current gold standards such as PCR and rapid antigen tests fall short in one or more of these aspects. Here, we report a label-free and amplification-free nanopore sensor platform that overcomes these challenges via direct detection and quantification of viral RNA in clinical samples from a variety of biological fluids. The assay uses an optofluidic chip that combines optical waveguides with a fluidic channel and integrates a solid-state nanopore for sensing of individual biomolecules upon translocation through the pore. High specificity and low limit of detection are ensured by capturing RNA targets on microbeads and collecting them by optical trapping at the nanopore location where targets are released and rapidly detected. We use this device for longitudinal studies of the viral load progression for Zika and Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infections in marmoset and baboon animal models, respectively. The up to million-fold trapping-based target concentration enhancement enables amplification-free RNA quantification across the clinically relevant concentration range down to the assay limit of RT-qPCR as well as cases in which PCR failed. The assay operates across all relevant biofluids, including semen, urine, and whole blood for Zika and nasopharyngeal and throat swab, rectal swab, and bronchoalveolar lavage for SARS-CoV-2. The versatility, performance, simplicity, and potential for full microfluidic integration of the amplification-free nanopore assay points toward a unique approach to molecular diagnostics for nucleic acids, proteins, and other targets.
Three-Channel Interference Interpretation of Fano Profile
Authors: Li 李 Bo 波 , Li 李 Tian-Jun 天钧 , Ma 马 Zi-Ru 子茹 , Wang 王 Xi-Yuan 希源 , Huang 黄 Xin-Chao 新朝 , Zhu 朱 Lin-Fan 林繁
Published: April 2024

Fano resonance is a ubiquitous phenomenon, and it is commonly interpreted as a two-channel interference of the discrete and continuous channels. The present work investigates the Fano profile from a perspective of the temporal evolution of the wave function. By exciting the atom with a δ pulse and calculating the evolution of the wave function, the Fano formula is deduced. The results clearly show that the Fano resonance is of a three-channel interference, which is different from the traditional understanding. The three channels are revealed as the ground-continuum, ground-discrete-continuum, and a previously unmentioned third channel, i.e., ground-continuum-discrete-continuum. The present three-channel interpretation can be easily generalized to other physical systems, contributing to a deeper understanding of the Fano profile.
The bismar scale and elastic collisions: a geometrical analogy
Authors: Prado Xabier , Paredes Angel , Area Iván , Domínguez Castiñeiras José Manuel , Mira Jorge
Published: April 2024

Throughout history, scales have served as instrumental tools for quantifying the weight of objects, relying on a comparative assessment against a specified reference weight. Scales featuring uneven arms, such as the bismar scale, have proven particularly adept at gauging masses within a specific range relative to a predetermined reference mass. On the other hand, the kinematics of elastic collisions hinge on the inertial masses of the colliding entities. By observing the aftermath of a collision between a known reference mass and an object of unknown mass, one can deduce the latter’s mass. In this contribution, we highlight a fascinating and clear analogy between these two methodologies. We do so by adapting a geometric approach, initially applicable to the bismar scale, to both non-relativistic and relativistic elastic collisions, encompassing phenomena such as Compton scattering.
Stellar interferometer experiment by measuring visibilities at different wavelengths
Authors: Barata J , Illarramendi M A , Grandes J , Zubia J , Arrospide E
Published: April 2024

In this work we develop an experiment wherein the variation of the fringe visibilities with wavelength provides insights into the geometry of various stellar sources or components. The experiment is based on the Michelson stellar interferometer in which a filter wheel has been inserted between a detecting camera and a telescope obscured by a double-aperture lid. The spatial and temporal incoherent light emitting from stellar sources has been simulated using polymer optical fibres and a broadband light-emitting diode. By measuring the visibilities of the central fringe at different wavelengths we are able to determine the morphology of the analysed light sources, provided that the baseline used is sufficiently long. The experiment is suitable for postgraduate students seeking to delve deeper into light coherence theory and to gain practical experience in optical stellar interferometry.
Energy performance and power application of low-gradient thermo-electrochemical cells
Authors: Liu Zi Yang , Dong Jinfeng , Zhu Qiang , Loh Xian Jun , Xu Jianwei , Wang Xizu , Yan Qingyu
Published: April 2024

Amidst the growing demand for sustainable and clean energy sources, the need for efficient and scalable technologies capable of harnessing low-temperature thermal gradients has become increasingly crucial. Low-gradient thermopower cells emerge as a promising solution to this challenge, offering the ability to generate electricity from the small temperature differences encountered in diverse applications, including industrial processes, waste heat recovery, and environmental monitoring. These novel thermal energy conversion power cells, developed based on the principles of thermo-electrochemical reaction potential difference, charge thermal diffusion, and other characteristics, exhibit enhanced conversion efficiency and hold immense application potential. Some work has reported maximum instantaneous power over 0.5 mW K−2 m−2, already reaching practical power output levels. However, there are still many challenges to overcome regarding continuous power output, stability, and efficiency of the device. Based on their power generation capabilities, we explore the potential applications of these thermopower cells in real-world scenarios, such as powering remote sensors, IoT devices, and integrating them into industrial processes for waste heat recovery.
Study of operation mode and breakdown characteristics for multi-stage gas switch
Authors: Shang Wei , Cheng Jie , Su Jiancang , Zeng Bo , Li Rui , Li Mei , Yu Binxiong , Qiu Xudong , Li Yongdong
Published: April 2024

Multi-stage gas switches (MSGSs) are widely used in megavolt pulsed power systems due to their advantages of high withstand voltage, fast establishing time and relatively high operating frequency. Multiple operation modes, which are induced by the different breakdown sequences at each stage, are found to affect the breakdown characteristics of the gas switch. Based on the theoretical analysis of the working principle, the classification of the operation mode and the factors determining the operation mode of the MSGS are proposed. Methods for investigating the output waveform for MSGS are established by simulating lumped parameters and studying the breakdown time sequence of individual stages. In comparison with the intended mode of operation, the disadvantages of the unintended modes of operation for MSGS, including error-breakdown and non-triggering mode, are revealed. For unintended modes, the distortion of the output waveform, which determines the efficiency of energy transmission through the switch and the increased delay time jitter, which determines the synchronization of the gas switch, are further investigated. The possibility of non-triggering and its mechanism on surface flashovers induced by drifting electrons are also analyzed. Based on this study, design principles and methods are proposed to ensure the intended operation of the MSGS.
Towards in-situ water quantification via neutron imaging: insights from NeXT-Grenoble
Authors: Nemati Arash , Lukić Bratislav , Tengattini Alessandro , Briffaut Matthieu , Séchet Philippe
Published: April 2024

Neutron imaging has gained increasing attention in recent years. A notable domain is the in-situ study of flow and concentration of hydrogen-rich materials. This demands precise quantification of the evolving concentrations. Several implementations deviate from the ideal conditions that allow the direct applicability of the Beer–Lambert law to assess this concentration. The objective of this work is to address these deviations by applying both calibration and correction procedures to ensure and validate accurate quantitative measurements during 2D and 3D neutron imaging conducted at the cold neutron source at the NeXT instrument of the Institute Laue–Langevin, Grenoble, France. Linear attenuation coefficients and non-linear correlations have been proposed to measure the water concentration based on the sample-to-detector distance. Furthermore, the effectiveness of the black body grid correction method, introduced by Boillat et al (2018 Opt. Express
26 15769), is evaluated which accounts for spurious deviations arising from the scattering of neutrons from the sample and the surrounding environment. The applicability of the Beer–Lambert law without any data correction is found to be reasonable within limited equivalent thickness (e.g. below 4 mm of water) beyond which the correction algorithm proves highly effective in eliminating spurious effects. Notably, this correction method maintains its effectiveness even with transmissions below 1%. We examine here the impact of grid location and resolution with respect to sample heterogeneity.
Multi-stage exponential model based on subspace clustering distribution for bearing remaining useful life prediction
Authors: Wang Hu , Ding Xiaoxi , Huang Zhao , Zhen Hebin , Yu Wennian , Huang Wenbin
Published: April 2024

As one of the key components in rotating machinery, the rolling element bearing has been widely used in actual production, such as wind turbines, vehicles and machine tools. A bearing’s remaining useful life (RUL) is an important indicator for its performance assessment, which is related to maintenance and production safety. To overcome the insensitivity of the conventional health indicator (HI) on bearing degradation assessment, this study proposes a subspace clustering method based on manifold learning to evaluate the evolution of health status, which describes the degenerate distribution via a two-class model and realizes the identification of the degradation of each stage. Motivated by the inconsistent degradation process in the application of actual bearing, this study proposes a multi-stage degradation identification criterion in an adaptive way, which can effectively identify different degradation rates of bearing. Based on the different degradation states, a multi-stage degradation exponential model is established to accurately predict the RUL. The effectiveness of the proposed method is validated through open datasets. The experimental results prove that the proposed method can effectively identify different degradation rates and accurately give the boundary time of the multi-stage degradation. The RUL prediction accuracy is significantly improved compared with traditional HI.