bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation effect of linear shear flow, wind, and dissipation on freak wave generation in finite water depth
Authors: Li Shaofeng , Xie Xiaohui , Chen Dake , Song Jinbao
Published: September 2023

This paper studies the modulation effect of linear shear flow (LSF), comprising a uniform flow and a shear flow with constant vorticity, combined with wind and dissipation on freak wave generation in water of finite depth. A nonlinear Schrödinger equation (NLSE) modified by LSF, strong wind, and dissipation is derived. This can be reduced to consider the effects of LSF, light wind, and dissipation, and further reduced to include only LSF. The relation between modulational instability (MI) of the NLSE and freak waves represented as a modified Peregrine Breather solution is analyzed. When considering only LSF, the convergence (divergence) effect of uniform up-flow (down-flow) and positive (negative) vorticity increases (decreases) the MI growth rate and promotes (inhibits) freak wave generation. The combined effect of LSF and light wind shows that a light adverse (tail) wind can restrain (amplify) MI and bury (trigger) freak waves. Under the effect of a light tailwind, LSF has the same effect on the MI growth rate and freak wave generation as the case without any wind. The combination of LSF and strong wind enables both adverse and tail winds to amplify MI and trigger freak waves. In the presence of strong wind, LSF has the opposite effect to the case of a light tailwind.
An algorithm to find the optimal oriented external electrostatic field for annihilating a reaction barrier in a polarizable molecular system
Authors: Bofill Josep Maria , Severi Marco , Quapp Wolfgang , Ribas-Ariño Jordi , Moreira Ibério de P. R. , Albareda Guillermo
Published: September 2023

The use of oriented external electric fields (OEEFs) to promote and control chemical reactivity has motivated many theoretical and computational studies in the last decade to model the action of OEEFs on a molecular system and its effects on chemical processes. Given a reaction, a central goal in this research area is to predict the optimal OEEF (oOEEF) required to annihilate the reaction energy barrier with the smallest possible field strength. Here, we present a model rooted in catastrophe and optimum control theories that allows us to find the oOEEF for a given reaction valley in the potential energy surface (PES). In this model, the effective (or perturbed) PES of a polarizable molecular system is constructed by adding to the original, non-perturbed, PES a term accounting for the interaction of the OEEF with the intrinsic electric dipole and polarizability of the molecular system, so called the polarizable molecular electric dipole (PMED) model. We demonstrate that the oOEEF can be established by locating a point in the original PES with unique topological properties: the optimal barrier breakdown or bond-breaking point (oBBP). The essential feature of the oBBP structure is the fact that this point maintains its topological properties for all the applied OEEFs, also for the unperturbed PES, thus becoming much more relevant than the commonly used minima and transition state structures. The PMED model proposed here has been implemented in an open access package and is shown to successfully predict the oOEEF for two processes: an isomerization reaction of a cumulene derivative and the Huisgen cycloaddition reaction.
Continuous beam steering with a varactor-based reconfigurable intelligent surface in the Ka-band at 31 GHz
Authors: Wolff Alexander , Franke Lars , Klingel Steffen , Krieger Janis , Mueller Lukas , Stemler Ralf , Rahm Marco
Published: September 2023

Varactor diodes have been proposed as active tuning elements of reconfigurable metasurfaces in the Ka-band. However, their experimental realization in this frequency range has not been demonstrated yet. We report the implementation of such a reconfigurable intelligent surface (RIS) made of 20×20 unit cells. By active tuning of the bias voltage of the varactors, the phase of the backward diffracted wave can be continuously tuned between 0° and 180°. Thus, the phase tuning can be independently controlled for each unit cell. The frequency working range of the RIS is 1.1 GHz (from 30.6 to 31.7 GHz). As an illustration of the practical use, we demonstrate continuous beam steering of microwave radiation at 31 GHz in a defined propagation plane.
Phase transitions and the magnetocaloric effect in (Gd,Tb)5Si2Ge2 compounds doped with Ti
Authors: Ovchenkova I. А. , Kurganskaya A. A. , Ovchenkova A. E. , Morozkin А. V. , Tereshina I. S. , Nikitin S. A.
Published: September 2023

We have conducted the study of structural, magnetic, magnetothermal, and magnetoelastic properties of four rare-earth compounds: Gd4.5Tb0.5Si2Ge2, Gd4TbSi2Ge2, Gd4.4Tb0.5Ti0.1Si2Ge2, and Gd3.9TbTi0.1Si2Ge2 in the vicinity of magnetically induced phase transitions. We demonstrate that the introduction of Ti into the rare-earth sublattice separates the structural and magnetic phase transitions and changes the order of magnetic phase transition from type I to II, while preserving high values of magnetocaloric effect (MCE). Additionally, incorporating a small quantity of Tb enables the creation of compounds with enhanced MCE values over a specific temperature range of 240–290 K. The observed phenomena can be attributed to the combined effects of forced magnetization and alteration of magnetic susceptibility during the structural phase transition that accompany the magnetic phase changes in these compounds.
New explicit formula for inertial lift in confined flows
Authors: Su Jinghong , Zheng Xu , Hu Guoqing
Published: September 2023

Inertial migration has proven effective for high-throughput manipulation of tiny particles in confined flows. However, complex and even controversial relationships between hydrodynamic forces and flow conditions hinder the development of an explicit formula for inertial lift acting on finite-sized particles at Reynolds numbers in the hundreds. Herein, we reveal the different scaling laws for shear gradient-induced inertial lift and wall-induced inertial lift by separating the contributions of pressure stress and viscous stress. A direct result of this treatment is a new explicit formula for the total inertial lift, valid for Reynolds numbers up to 400 and particle blockage ratios up to 0.25. This study provides an alternative way to understand inertial lift, thereby greatly facilitating the prediction of particle migration in practical microfluidic applications.
Effects of micron–nano composite iron particle powders on the tribological properties of magnetic fluids used for a nonlinear energy sink vibration absorber
Authors: Nie Songlin , Gong Fei , Ji Hui , Zhang Le , Ma Zhonghai , Yin Fanglong
Published: September 2023

Low-frequency vibration control is a crucial challenge within the realm of fluid physics, and in this paper, a novel magnetic compound fluid (MCF) has been developed to produce a magnetic fluid nonlinear energy sink (MF-NES) with optimum energy consumption efficiency. The mixed doping of bi-dispersed nano-sized iron particles (NIPs) and micrometer-sized carbonyl iron particles (CIPs) can generate a load-bearing structure between the inertial mass and the MF-NES shell with a reduced friction coefficient. The effectiveness and sensitivity of the MF-NES mechanism is significantly enhanced, particularly in responding to low frequency vibrations. To predict and quantify the friction coefficient of the MF, a novel hybrid approach combining data handling and a genetic algorithm model was developed and rigorously validated through empirical data obtained from the experiments and demonstrated that the bi-dispersed NIPs/CIPs MCF had a notably lower friction coefficient, making it adept at responding to low-frequency and even ultra-low-frequency vibrations.
Fourfold magnetic anisotropy varied by interfacial exchange coupling in epitaxial Fe/IrMn bilayers
Authors: Feng Xinwei , Wang Yangping , Meng Jing , Lin Haoyu , Zhu Xiaoyan , Xie Yali , Jiang Dongmei , Xu Yang , Shang Tian , Zhan Qingfeng
Published: September 2023

We report variable in-plane fourfold magnetic anisotropy in epitaxial exchange-biased Fe/IrMn bilayers with different layer thicknesses. The fourfold magnetic anisotropy of the bilayers continuously decreases and even appears negative as the thickness of the Fe layer decreases, indicating a change in the easy axes from Fe 100 to Fe 110, which can be interpreted by the competition between the intrinsic magnetocrystalline anisotropy along Fe 100 and the extrinsic fourfold magnetic anisotropy along Fe 110 induced by the interfacial exchange coupling to IrMn. As the IrMn thickness increases, the fourfold magnetic anisotropy of the bilayers decreases rapidly from a value close to the intrinsic magnetocrystalline anisotropy of Fe and then gradually reaches saturation. The extrinsic fourfold magnetic anisotropy depends on the amount of the induced uncompensated IrMn spins near the edge of antiferromagnetic domains. In contrast, the exchange bias is determined by the net difference of the opposite uncompensated IrMn spins.
Numerical simulation and intelligent prediction of thermal transport of a water-based copper oxide nanofluid in a lid-driven trapezoidal cavity
Authors: Bibi Aneela , Xu Hang
Published: September 2023

This article investigates the fluid dynamics and heat transfer properties in a trapezoidal enclosure containing a heated cylindrical object. It involves the interaction of multiple physical processes such as the magnetic field, thermal radiation, porous materials, and aqueous copper oxide nanoparticles. The governing partial differential equations are analyzed numerically through the continuous Galerkin finite element algorithm. The analysis takes into account various physical parameter factors, including the Richardson number (0–5), the Hartmann number (5−40), the Darcy number (0.001−0.1), thermal radiation parameter (0.5−2), and nanoparticle volume concentration (0.01−0.1). The physical mechanism of thermal and mass transfer in the enclosure caused by various factors is fully explored. In addition, the multiple expression programming (MEP) technique is implemented to report a comparative analysis of flow profiles and thermal distribution. The findings demonstrated that at low Ri, the primary flow within the cavity is driven by the shear friction generated by the moving walls. The growing importance of radiative heat transfer reduces the effectiveness of convective heat transfer, resulting in a decline in the average Nusselt number with R. The heat transfer rate rises up to 27.7% as ϕ augments; however, its value declines by 9.37% against Ha. The expected results obtained by the MEP approach are very consistent with the numerical ones. There is no doubt that the new MEP concept provides a valuable tool for researchers to predict the heat transfer behavior of any data set in cavities of different shapes. It is expected to provide new idea for the development of efficient cooling systems and the improvement of energy efficiency in various engineering applications.
Effect of thermal boundary condition and turbulent models on the combustion simulation of ethylene-fueled scramjet combustor
Authors: Sun Yujia , Zheng Shu , Jiang Lin , Wang Shunyao
Published: September 2023

Wall thermal boundary conditions and turbulent models can affect flow and combustion simulations but are seldom considered in the turbulent modeling of supersonic combustors. This work investigated the effect of thermal boundary conditions and four turbulent models on turbulent combustion in a cavity-stabilized scramjet combustor. Results showed that the thermal boundary condition had a noticeable influence on the temperature fields. Changing the thermal boundary condition from zero gradient to a fixed lower temperature considerably reduced the maximum temperature but did not affect the temperature distribution. The fixed temperature boundary condition generated a slightly larger reaction heat release near the upper region of the cavity. However, the mass fraction of carbon dioxide was low for a fixed low temperature. The pressure increased near the rear of the cavity but decreased elsewhere at a fixed temperature. Reynolds-averaged models (k-epsilon, k-omega, and realizable k-epsilon) tend to over-predict the temperature and turbulent kinetic energy but under-predict the mass fraction of carbon dioxide. The detached Eddy simulation also under-predicts carbon dioxide but predicts a more accurate temperature.
Microparticle electrical conductivity measurement using optoelectronic tweezers
Authors: Ren Wei , Zaman Mohammad Asif , Wu Mo , Jensen Michael Anthony , Davis Ronald Wayne , Hesselink Lambertus
Published: September 2023

When it comes to simulate or calculate an optoelectronic tweezer (OET) response for a microparticle suspended in a given medium, a precise electrical conductivity (later referred to as conductivity) value for the microparticle is critical. However, there are not well-established measurements or well-referenced values for microparticle conductivities in the OET realm. Thus, we report a method based on measuring the escape velocity of a microparticle with a standard OET system to calculate its conductivity. A widely used 6 μm polystyrene bead (PSB) is used for the study. The conductivity values are found to be invariant around 2×10-3 S/m across multiple different aqueous media, which helps clarify the ambiguity in the usage of PSB conductivity. Our convenient approach could principally be applied for the measurement of multiple unknown OET-relevant material properties of microparticle-medium systems with various OET responses, which can be beneficial to carry out more accurate characterization in relevant fields.
Allostatic load in children: The cost of empathic concern
Authors: Phua Desiree Y. , Chen Helen , Yap Fabian , Chong Yap Seng , Gluckman Peter D. , Broekman Birit F. P. , Eriksson Johan G. , Meaney Michael J.
Published: September 2023

Early-life adversity affects long-term health outcomes but there is considerable interindividual variability in susceptibility to environmental influences. We proposed that positive psychological characteristics that reflect engagement with context, such as being concerned about people or performance on tasks (i.e., empathic concern), could moderate the interindividual variation in sensitivity to the quality of the early environment. We studied 526 children of various Asian nationalities in Singapore (46.6% female, 13.4% below the poverty line) with longitudinal data on perinatal and childhood experiences, maternal report on empathic concern of the child, and a comprehensive set of physiological measures reflecting pediatric allostatic load assessed at 6 y of age. The perinatal and childhood experiences included adversities and positive experiences. We found that cumulative adverse childhood experience was positively associated with allostatic load of children at 6 y of age at higher levels of empathic concern but not significantly associated at lower levels of empathic concern. This finding reveals evidence for the importance of empathic concern as a psychological characteristic that moderates the developmental impact of environmental influences, serving as a source for vulnerability to adversities in children.
Dual-functional single-atomic Mo/Fe clusters–decorated C
3
N
5
via three electron-pathway in oxygen reduction reaction for tandemly removing contaminants from water
Authors: Dong Chencheng , Wang Zhi-qiang , Yang Chao , Hu Xiaomeng , Wang Pei , Gong Xue-qing , Lin Lin , Li Xiao-yan
Published: September 2023

Inspired by the development of single-atom catalysts (SACs), the fabrication of multimetallic SACs can be a promising technical approach for the in situ electro-Fenton (EF) process. Herein, dual-functional atomically dispersed Mo–Fe sites embedded in carbon nitride (C
3
N
5
) (i.e., MoFe/C
3
N
5
) were synthesized via a facile SiO
2
template method. The atomically isolated bimetallic configuration in MoFe/C
3
N
5
was identified by combining the microscopic and spectroscopic techniques. The MoFe/C
3
N
5
catalyst on the cathode exhibited a remarkable catalytic activity toward the three electron-dominated oxygen reduction reaction in sodium sulfate, leading to a highly effective EF reaction with a low overpotential for the removal of organic contaminants from wastewater. The new catalyst showed a superior performance over its conventional counterparts, owing to the dual functions of the dual-metal active sites. Density functional theory (DFT) analysis revealed that the dual-functional 50-MoFe/C
3
N
5
catalyst enabled a synergistic action of the Mo–Fe dual single atomic centers, which can alter the adsorption/dissociation behavior and decrease the overall reaction barriers for effective organic oxidation during the EF process. This study not only sheds light on the controlled synthesis of atomically isolated catalyst materials but also provides deeper understanding of the structure–performance relationship of the nanocatalysts with dual active sites for the catalytic EF process. Additionally, the findings will promote the advanced catalysis for the treatment of emerging organic contaminants in water and wastewater.
High rates of rock organic carbon oxidation sustained as Andean sediment transits the Amazon foreland-floodplain
Authors: Dellinger Mathieu , Hilton Robert G. , Baronas J. Jotautas , Torres Mark A. , Burt Emily I. , Clark Kasey E. , Galy Valier , Ccahuana Quispe Adan Julian , West A. Joshua
Published: September 2023

The oxidation of organic carbon contained within sedimentary rocks (“petrogenic” carbon, or hereafter OC
petro
) emits nearly as much CO
2
as is released by volcanism, thereby playing a key role in the long-term global C budget. High erosion rates in mountains have been shown to increase OC
petro
oxidation. However, these settings also export unweathered material that may continue to react in downstream floodplains. The relative importance of OC
petro
oxidation in mountains versus floodplains remains difficult to assess as disparate methods have been used in the different environments. Here, we investigate the sources and fluxes of rhenium (Re) in the Rio Madre de Dios to quantify OC
petro
oxidation from the Andes to the Amazon floodplain using a common approach. Dissolved rhenium concentrations (n = 131) range from 0.01 to 63 pmol L
−1
and vary depending on lithology and geomorphic setting. We find that >75% of the dissolved Re derives from OC
petro
oxidation and that this proportion increases downstream. We estimate that in the Andes, OC
petro
oxidation releases 11.2
+4.5
/
−2.8
tC km
−2
y
−1
of CO
2
, which corresponds to ~41% of the total OC
petro
denudation (sum of oxidized and solid OC
petro
). A Re mass balance across the Rio Madre de Dios shows that 46% of OC
petro
oxidation takes place in the Andes, 14% in the foreland-lowlands, and 40% in the Andean-fed floodplains. This doubling of OC
petro
oxidation flux downstream of the Andes demonstrates that, when present, floodplains can greatly increase OC
petro
oxidation and CO
2
release.
Distinct regions of the kinesin-5 C-terminal tail are essential for mitotic spindle midzone localization and sliding force
Authors: Gergely Zachary R. , Jones Michele H. , Zhou Bojun , Cash Cai , McIntosh J. Richard , Betterton Meredith D.
Published: September 2023

Kinesin-5 motor proteins play essential roles during mitosis in most organisms. Their tetrameric structure and plus-end-directed motility allow them to bind to and move along antiparallel microtubules, thereby pushing spindle poles apart to assemble a bipolar spindle. Recent work has shown that the C-terminal tail is particularly important to kinesin-5 function: The tail affects motor domain structure, ATP hydrolysis, motility, clustering, and sliding force measured for purified motors, as well as motility, clustering, and spindle assembly in cells. Because previous work has focused on presence or absence of the entire tail, the functionally important regions of the tail remain to be identified. We have therefore characterized a series of kinesin-5/Cut7 tail truncation alleles in fission yeast. Partial truncation causes mitotic defects and temperature-sensitive growth, while further truncation that removes the conserved BimC motif is lethal. We compared the sliding force generated bycut7mutants using a kinesin-14 mutant background in which some microtubules detach from the spindle poles and are pushed into the nuclear envelope. These Cut7-driven protrusions decreased as more of the tail was truncated, and the most severe truncations produced no observable protrusions. Our observations suggest that the C-terminal tail of Cut7p contributes to both sliding force and midzone localization. In the context of sequential tail truncation, the BimC motif and adjacent C-terminal amino acids are particularly important for sliding force. In addition, moderate tail truncation increases midzone localization, but further truncation of residues N-terminal to the BimC motif decreases midzone localization.
mitoSplitter: A mitochondrial variants-based method for efficient demultiplexing of pooled single-cell RNA-seq
Authors: Lin Xinrui , Chen Yingwen , Lin Li , Yin Kun , Cheng Rui , Lin Xin , Wang Xiaoyu , Guo Ye , Wu Zhaorun , Zhang Yingkun , Li Jin , Yang Chaoyong , Song Jia
Published: September 2023

Single-cell RNA-seq (scRNA-seq) analysis of multiple samples separately can be costly and lead to batch effects. Exogenous barcodes or genome-wide RNA mutations can be used to demultiplex pooled scRNA-seq data, but they are experimentally or computationally challenging and limited in scope. Mitochondrial genomes are small but diverse, providing concise genotype information. We developed “mitoSplitter,” an algorithm that demultiplexes samples using mitochondrial RNA (mtRNA) variants, and demonstrated that mtRNA variants can be used to demultiplex large-scale scRNA-seq data. Using affordable computational resources, mitoSplitter can accurately analyze 10 samples and 60,000 cells in 6 h. To avoid the batch effects from separated experiments, we applied mitoSplitter to analyze the responses of five non-small cell lung cancer cell lines to BET (Bromodomain and extraterminal) chemical degradation in a multiplexed fashion. We found the synthetic lethality of
TOP2A
inhibition and BET chemical degradation in BET inhibitor-resistant cells. The result indicates that mitoSplitter can accelerate the application of scRNA-seq assays in biomedical research.
HP6/Umbrea is dispensable for viability and fertility, suggesting essentiality of newly evolved genes is rare
Authors: Grill Sherilyn , Riley Ashley , Selvaraj Monica , Lehmann Ruth
Published: September 2023

The newly evolved gene Heterochromatin Protein 6 (
HP6
), which has been previously classified as essential, challenged the dogma that functions required for viability are only seen in genes with a long evolutionary history. Based on previous RNA-sequencing analysis in Drosophila germ cells, we asked whether HP6 might play a role in germline development. Surprisingly, we found that CRISPR-generated
HP6
mutants are viable and fertile. Using previously generated mutants, we identified an independent lethal allele and an RNAi off-target effect that prevented accurate interpretation of
HP6
essentiality. By reviewing existing data, we found that the vast majority of young genes that were previously classified as essential were indeed viable when tested with orthologous methods. Together, our data call into question the frequency with which newly evolved genes gain essential functions and suggest that using multiple independent genetic methods is essential when probing the functions of young genes.
Remote control of mechanochemical reactions under physiological conditions using biocompatible focused ultrasound
Authors: Yao Yuxing , McFadden Molly E. , Luo Stella M. , Barber Ross W. , Kang Elin , Bar-Zion Avinoam , Smith Cameron A. B. , Jin Zhiyang , Legendre Mark , Ling Bill , Malounda Dina , Torres Andrea , Hamza Tiba , Edwards Chelsea E. R. , Shapiro Mikhail G. , Robb Maxwell J.
Published: September 2023

External control of chemical reactions in biological settings with spatial and temporal precision is a grand challenge for noninvasive diagnostic and therapeutic applications. While light is a conventional stimulus for remote chemical activation, its penetration is severely attenuated in tissues, which limits biological applicability. On the other hand, ultrasound is a biocompatible remote energy source that is highly penetrant and offers a wide range of functional tunability. Coupling ultrasound to the activation of specific chemical reactions under physiological conditions, however, remains a challenge. Here, we describe a synergistic platform that couples the selective mechanochemical activation of mechanophore-functionalized polymers with biocompatible focused ultrasound (FUS) by leveraging pressure-sensitive gas vesicles (GVs) as acousto-mechanical transducers. The power of this approach is illustrated through the mechanically triggered release of covalently bound fluorogenic and therapeutic cargo molecules from polymers containing a masked 2-furylcarbinol mechanophore. Molecular release occurs selectively in the presence of GVs upon exposure to FUS under physiological conditions. These results showcase the viability of this system for enabling remote control of specific mechanochemical reactions with spatiotemporal precision in biologically relevant settings and demonstrate the translational potential of polymer mechanochemistry.
Disassembly of bundled F-actin and cellular remodeling via an interplay of Mical, cofilin, and F-actin crosslinkers
Authors: Rajan Sudeepa , Yoon Jimok , Wu Heng , Srapyan Sargis , Baskar Raju , Ahmed Giasuddin , Yang Taehong , Grintsevich Elena E. , Reisler Emil , Terman Jonathan R.
Published: September 2023

Cellular form and function are controlled by the assembly and stability of actin cytoskeletal structures—but disassembling/pruning these structures is equally essential for the plasticity and remodeling that underlie behavioral adaptations. Importantly, the mechanisms of actin assembly have been well-defined—including that it is driven by actin’s polymerization into filaments (F-actin) and then often bundling by crosslinking proteins into stable higher-order structures. In contrast, it remains less clear how these stable bundled F-actin structures are rapidly disassembled. We now uncover mechanisms that rapidly and extensively disassemble bundled F-actin. Using biochemical, structural, and imaging assays with purified proteins, we show that F-actin bundled with one of the most prominent crosslinkers, fascin, is extensively disassembled by Mical, the F-actin disassembly enzyme. Furthermore, the product of this Mical effect, Mical-oxidized actin, is poorly bundled by fascin, thereby further amplifying Mical’s disassembly effects on bundled F-actin. Moreover, another critical F-actin regulator, cofilin, also affects fascin-bundled filaments, but we find herein that it synergizes with Mical to dramatically amplify its disassembly of bundled F-actin compared to the sum of their individual effects. Genetic and high-resolution cellular assays reveal that Mical also counteracts crosslinking proteins/bundled F-actin in vivo to control cellular extension, axon guidance, and Semaphorin/Plexin cell-cell repulsion. Yet, our results also support the idea that fascin-bundling serves to dampen Mical’s F-actin disassembly in vitro and in vivo—and that physiologically relevant cellular remodeling requires a fine-tuned interplay between the factors that build bundled F-actin networks and those that disassemble them.
Quantum gravity phenomenology from the perspective of quantum general relativity and quadratic gravity
Authors: Menezes Gabriel
Published: September 2023

Multi-messenger astronomy provides us with the possibility of discovering phenomenological signatures of quantum-gravity effects. This should be of paramount importance in the pursuit of an elusive quantum theory for the gravitational interactions. Here we discuss feasible explorations within the effective field theory (EFT) treatment of general relativity. By exploring current techniques borrowed from modern amplitude methods, we calculate leading quantum corrections to the classical radiated momentum and spectral waveforms. The lessons drawn from these low-energy results are that phenomenological applications in gravitational-wave physics can be discussed in line with the EFT approach. In turn, we also examine possible phenomenological surveys from the perspective of a UV completion for quantum gravity which employs the metric as the fundamental dynamical variable, namely quadratic gravity. Being more specific, by resorting to the eikonal approximation, we compute the leading-order time delay/advance in the scattering of light by a heavy object and find a possible significant deviation from the standard general-relativity prediction. This allows us to probe causal uncertainty due to quantum fluctuations of the gravitational field as a genuine prediction from Planck-scale physics.
A Fock space structure for the diffeomorphism invariant Hilbert space of loop quantum gravity and its applications
Authors: Sahlmann Hanno , Sherif Waleed
Published: September 2023

Loop quantum gravity (LQG) is a quantization program for gravity based on the principles of QFT and general covariance of general relativity. Quantum states of LQG describe gravitational excitations based on graphs embedded in a spatial slice of spacetime. We show that, under certain assumptions on the class of diffeomorphisms, the space of diffeomorphism invariant states carries a Fock space structure. The role of one-particle excitations for this structure is played by the diffeomorphism invariant states based on graphs with a single (linked) component. This means, however, that a lot of the structure of the diffeomorphism invariant Hilbert space remains unresolved by this structure. We show how the Fock structure allows to write at least some condensate states of group field theory as diffeomorphism invariant coherent states of LQG in a precise sense. We also show how to construct other interesting states using this Fock structure. We finally explore the quantum geometry of single- and multi-particle states and tentatively observe some resemblance to geometries with a single or multiple components, respectively.
Strong and controlled photonic spin Hall effect in a van der Waals semiconducting transition metal oxide slab
Authors: Da Haixia , Ye Huapeng
Published: September 2023

A natural biaxial van der Waals material α-MoO3 hosts the in-plane anisotropy as well as the ultra-low-loss polaritons, which hold great potential in the applications of subwavelength focusing, planar nanooptics as well as polarization converters. Here, we show that the simple α-MoO3 slab supports giant spin shifts of the reflected wave for either the horizontal (H) or vertical (V) polarized incident waves at specific frequencies and the low as well as large incident angle regions, whose maximum values can reach their theoretical upper limit. Such obtained giant spin shifts at the low and large incident angles are governed by the intrinsically in-plane anisotropy of α-MoO3 and the zero values of the reflectance at the transverse magnetic or electric wave. In addition, we also examine how the orientation of the optical axis of α-MoO3 slab controls the sign and magnitude of the reflected spin shifts and find that the positions where the maximum spin shifts of the reflected wave happen can be switched by rotating it. Our results on the reflected spin shifts in the α-MoO3 slab lay a foundation for unraveling the photonic spin Hall effects of anisotropic van der Waals crystals.
Electrical breakdown dynamics in an argon bubble submerged in conductive liquid for nanosecond pulsed discharges
Authors: L Sponsel Nicholas , Gershman Sophia , Stapelmann Katharina
Published: September 2023

This study delves into the dynamics of cold atmospheric plasma and their interaction within conductive solutions under the unique conditions of nanosecond pulsed discharges (22 kV peak voltage, 10 ns FWHM, 4.5 kV ns−1 rate-of-rise). The research focuses on the electrical response, breakdown, and discharge propagation in an argon bubble, submerged in a NaCl solution of varying conductivity. Full or partial discharges were observed at conductivities of 1.5 µS cm−1 (deionized water) to 1.6 mS cm−1, but no breakdown was observed at 11.0 mS cm−1 when reducing the electrode gap. It is demonstrated that at higher conductivity electric breakdown is observed only when the gas bubble comes into direct contact with the electrode and multiple emission nodes were observed at different timescales. These nodes expanded in the central region of the bubble over timescales longer than the initial high-voltage pulse. This work offers a temporal resolution of 2 ns exposure times over the first 30 ns of the initial voltage pulse, and insight into plasma formation over decaying reflected voltage oscillations over 200 ns.
A broadband microwave absorber with properties optimized by an all-dielectric structure
Authors: Feng Fan , Wu Zhuang , Luo Jie , Chen Xiqiao , Zhang Zilong , Zou Yanhong
Published: September 2023

Impedance matching is the premise of obtaining a perfect absorbing effect. Through improving the impedance matching condition of the grid-structured absorber by covering a layer of 0.5 mm thick 3D printed disk structure. The bandwidth of the new structure with the reflection loss less than −10 dB is optimized from 5.3–10.2 GHz and 14.8–18 GHz to 5.3–18 GHz. And the total thickness is 3.5 mm. The experimental results further validated the simulation results. The broadband absorption attributes to the synergistic effect of the dielectric loss and magnetic loss. Additionally, the optimized impedance matching is the critical precondition. Due to the 3D printing technology, the printing layer all-dielectric structure can be flexibly fabricated. The tailored strategy of optimizing the impedance matching by the 3D printed all-dielectric plays a guiding role in the realization of broadband absorption.
Thermophysical properties and atomic structure of liquid Zr–Nb alloys investigated by electrostatic levitation and molecular dynamics simulation
Authors: Zuo D D , Chang J , Wang Q , Wang H P
Published: September 2023

The investigation of the thermophysical properties of liquid Zr–Nb alloys holds great significance for theoretical research and technical application in liquid physics. However, the high temperatures involved make their experimental measurement challenging. In this study, the densities of liquid Zr-x wt.% Nb (x= 1.0, 2.5, 6.0) alloys were examined by electrostatic levitation and molecular dynamics calculation. Remarkably, the alloys achieved maximum undercooling of 335 K, 311 K and 326 K, respectively. Correspondingly, the densities are 6.20, 6.22 and 6.26 g·cm−3 at the liquidus temperatures (T
L), respectively. The corresponding temperature coefficients are 2.61 × 10−4, 2.75 × 10−4 and 2.84 × 10−4 g·cm−3·K−1, respectively. Notably, the experimental density results align well with the simulated results. Moreover, the molar volume (V
m), thermal expansion coefficient (α) and diffusion coefficient (D) were derived based on the experimental data and simulations. The thermal expansion coefficients reduce linearly with decreasing temperature. The analysis of the pair distribution function, coordination number (CN) and the radial distribution function reveals the temperature-dependent evolution of the atomic structure. The CN
total and CN
Zr–Zr initially increase and then decrease with decreasing temperature, while the change trends for CN
Zr–Nb and CN
Nb–Nb varied among the three alloys. The radial distribution function of three liquid alloys reveals that the atomic number density increases as the temperature drops. Additionally, the total diffusion coefficients decrease with the reduction of temperature and the rise of Nb content from 1.0 wt.% Nb to 6.0 wt.% Nb.
A closer look at how symmetry constraints and the spin–orbit coupling shape the electronic structure of Bi(111)
Authors: Alcántara Ortigoza Marisol , Rahman Talat S
Published: September 2023

Fully relativistic density-functional-theory calculations of Bi(111) thin films are analyzed to revisit their two metallic surface-states branches. We first contrast these metallic branches with surface states arising at gaps in the valence band opened by the spin–orbit coupling (SOC). We find that the two metallic branches along

Γ
M

‾

do not overlap with the bulk band at the zone boundary, M. We show that the spin texture observed in such states cannot be traced to the lifting of Kramers’ degeneracy. Instead, we track them to the

m
j

=
±
1

/

2

–

m
j

=
±
3

/

2

SOC splitting, the potential anisotropy for in-plane and out-of-plane states, and the coupling between the opposite surfaces of a slab occurring near M, which is driven by a spatial redistribution of the four metallic states composing the two metallic branches. Each of these branches appears to be non-degenerate at the tested surface, yet each is degenerate with another state of opposite spin at the other surface. Nevertheless, the four metallic states bear some contribution on both surfaces of the film because of their spatial redistribution near M. The overlapping among these states near M, afforded by their spatial redistribution on both surfaces, causes a hybridization that perpetuates the splitting between the two branches, makes the film’s electronic structure thickness dependent near M, extinguishes the magnetic moment of the metallic states avoiding the magnetic-moment discontinuity at M, and denies the need or expectancy of the metallic branches becoming degenerate at M. We propose that the opposite spin polarization observed for the two metallic branches occurs because the surface atoms retain their covalent bonds and thus cannot afford magnetic polarization. We show that the Rashba-splitting of the metallic states for inversion-asymmetric films does not have a fixed magnitude but can be tuned by changing the perturbation breaking inversion symmetry.
Evaluation of receiver calibration based on clock-steering for time–frequency transfer
Authors: Guo Wenfei , Chen Jinxin , Gong Xiaopeng , Liu Jingnan
Published: September 2023

Calibrating the global navigation satellite system (GNSS) time–frequency transfer system is crucial for accurate GNSS time–frequency transfer. The most commonly used relative calibration method relies on the common-clock to eliminate clock differences. However, it cannot eliminate the changes in clock signal reference point delay (REFDLY). The changes in REFDLY during calibration could not be ignored, especially for ordinary users in an unstable environment. To address this issue, we use the GNSS real-time single-difference time synchronization calibration based on clock-steering, which can detect the change in REFDLY. According to this method, the clock differences and REFDLY are eliminated simultaneously. We installed two GNSS antennas on the roof of the Xinghu Building of Wuhan University and designed a clock synchronization terminal to evaluate the performance of this method. The data were collected on Day of Year 152–156, 167–171, 222–226, 231–235, 244, 258, 260, and 262 in 2022. In accordance with the calibration results, the standard deviation better than 100 ps, and the stability reaches

10

−
15

@

10
000

s

. Also, the time variance better than 60 ps, and the uncertainty

u

CAL

better than 0.5 ns. Compared to the common-clock calibration, one of the most significant benefits is the elimination of REFDLY, which leads to decreased uncertainty and better stability over both the short-term and long-term.
Measuring porous media velocity fields and grain bed architecture with a quantitative PLIF-based technique
Authors: Hilliard Brandon , Budwig Ralph , Skifton Richard S , Durgesh Vibhav , Reeder William J , Bhattarai Bishal , Martin Benjamin T , Xing Tao , Tonina Daniele
Published: September 2023

Porous media flows are common in both natural and anthropogenic systems. Mapping these flows in a laboratory setting is challenging and often requires non-intrusive measurement techniques, such as particle image velocimetry (PIV) coupled with refractive index matching (RIM). RIM-coupled PIV allows the mapping of velocity fields around transparent solids by analyzing the movement of neutrally buoyant micron-sized seeding particles. The use of this technique in a porous medium can be problematic because seeding particles adhere to grains, which causes the grain bed to lose transparency and can obstruct pore flows. Another non-intrusive optical technique, planar laser-induced fluorescence (PLIF), can be paired with RIM and does not have this limitation because fluorescent dye is used instead of particles, but it has been chiefly used for qualitative flow visualization. Here, we propose a quantitative PLIF-based methodology to map both porous media flow fields and porous media architecture. Velocity fields are obtained by tracking the advection-dominated movement of the fluorescent dye plume front within a porous medium. We also propose an automatic tracking algorithm that quantifies 2D velocity components as the plume moves through space in both an Eulerian and a Lagrangian framework. We apply this algorithm to three data sets: a synthetic data set and two laboratory experiments. Performance of this algorithm is reported by the mean (bias error, B) and standard deviation (random error, SD) of the residuals between its results and the reference data. For the synthetic data, the algorithm produces maximum errors of B & SD = 32% & 23% in the Eulerian framework, respectively, and B & SD = −0.04% & 3.9% in the Lagrangian framework. The small-scale laboratory experimental data requires the Eulerian framework and produce errors of B & SD = −0.5% & 33%. The Lagrangian framework is used on the large-scale laboratory experimental data and produces errors of B & SD = 5% & 44%. Mapping the porous media architecture shows negligible error for reconstructing calibration grains of known dimensions.
DIG-SLAM: an accurate RGB-D SLAM based on instance segmentation and geometric clustering for dynamic indoor scenes
Authors: Liang Rongguang , Yuan Jie , Kuang Benfa , Liu Qiang , Guo Zhenyu
Published: September 2023

Simultaneous localization and mapping (SLAM) has emerged as a critical technology enabling robots to navigate in unknown environments, drawing extensive attention within the robotics research community. However, traditional visual SLAM ignores the presence of dynamic objects in indoor scenes, and dynamic point features of dynamic objects can lead to incorrect data correlation, making the traditional visual SLAM is difficult to accurately estimate the camera’s pose when the objects in the scenes are moving. Using only point features cannot fully extract geometric information in dynamic indoor scenes, reducing the system’s robustness. To solve this problem, we develop a RGB-D SLAM system called DIG-SLAM. Firstly, the objects’ contour regions are extracted using the YOLOv7 instance segmentation method, serving as a prerequisite for determining dynamic objects and constructing a semantic information map. Meanwhile, the line features are extracted using the line segment detector algorithm, and the redundant line features are optimized via K-means clustering. Secondly, moving consistency checks combined with instance partitioning determine dynamic regions, and the point and line features of the dynamic regions are removed. Finally, the combination of static line features and point features optimizes the camera pose. Meanwhile, a static semantic octree map is created to provide richer and higher-level scene understanding and perception capabilities for robots or autonomous systems. The experimental results on the Technische Universität München dataset show that the average absolute trajectory error of the developed DIG-SLAM is reduced by 28.68% compared with the dynamic semantic SLAM. Compared with other dynamic SLAM methods, the proposed system shows better camera pose estimation accuracy and system’s robustness in dynamic indoor environments and better map building in real indoor scenes.
Sub-10 nm HfZrO ferroelectric synapse with multiple layers and different ratios for neuromorphic computing
Authors: Chen Bo , Wang Chengcheng , Zhan Xuepeng , Wu Shuhao , Tai Lu , Mei Junyao , Wu Jixuan , Chen Jiezhi
Published: September 2023

To break the von Neumann bottleneck, emerging non-volatile memories have gained extensive attention in hardware implementing neuromorphic computing. The device scaling with low operating voltage is of great importance for delivering a high-integrating and energy-efficient neuromorphic system. In this paper, we fabricated sub-10 nm ferroelectric capacitors based on HfZrO (HZO) film with varying HfO and ZrO components. Compared to the conventional HZO capacitors (a constant component of 1:1), the varying component ferroelectric capacitors show similar remnant polarization but a lower coercive electric field (Ec). This enables the partial domain switching processed at a lower pulse amplitude and width, which is essential for emulating typical synaptic features. In the MNIST recognition task, the accuracy of sub-10 nm ferroelectric artificial synapse can approach ∼85.83%. Our findings may provide great potential for developing next-generation neuromorphic computing-based ultra-scaled ferroelectric artificial synapses.
Electroactive poly(thionine) as imprinted polymer and reference probe simultaneously for ratiometric ion imprinted electrochemical Pb2+ sensor
Authors: Liu Jiawei , Zou Jin , Deng Linbo , Peng Guanwei , Liu Shuwu , Rui Peixin , Wang Xiaoqiang , Wang Linyu , Gao Yansha , Lu Limin
Published: September 2023

In this work, an electrochemical sensor based on ion-imprinted polymer/Au nanoparticles/porous biochar (IIP/AuNPs/PBC) composite was proposed for the highly selective and sensitive detection of Pb2+. In this work, poly (thionine) (pTHI) served simultaneously as imprinted polymer and reference probe. It could not only realize the specific detection of Pb2+, but also provide an internal reference signal to eliminate the influence of human and environmental factors on the detection signal and further improve the stability of the sensor. In addition, the AuNPs/PBC composite with large specific surface area, excellent electron transport and electrocatalytic performance could effectively enhance the detection signal as a carrier material. At the same time, the AuNPs on the PBC surface would promote the formation of uniform and stable IIP through Au–S bonds. The synergistic effect between IIP, AuNPs/PBC and ratiometric signal mode gave the Pb2+ sensor excellent performance, including a wide linear range (0.1–1000 μg l−1), low detection limit (0.03 μg l−1, S/N = 3), excellent selectivity and stability. All these results indicate that the proposed sensor could provide a meaningful reference for highly selective detection of heavy metal ions (HMIs).