bluuebunny/crossref_metadata_2025 huggingface dataset:
Performant automatic differentiation of local coupled cluster theories: Response properties and ab initio molecular dynamics
Authors: Zhang Xing , Li Chenghan , Ye Hong-Zhou , Berkelbach Timothy C. , Chan Garnet Kin-Lic
Published: July 2024

In this work, we introduce a differentiable implementation of the local natural orbital coupled cluster (LNO-CC) method within the automatic differentiation framework of the PySCFAD package. The implementation is comprehensively tuned for enhanced performance, which enables the calculation of first-order static response properties on medium-sized molecular systems using coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)]. We evaluate the accuracy of our method by benchmarking it against the canonical CCSD(T) reference for nuclear gradients, dipole moments, and geometry optimizations. In addition, we demonstrate the possibility of property calculations for chemically interesting systems through the computation of bond orders and Mössbauer spectroscopy parameters for a [NiFe]-hydrogenase active site model, along with the simulation of infrared spectra via ab initio LNO-CC molecular dynamics for a protonated water hexamer.
Development of a diamagnetic loop in KAIMIR
Authors: Choe M. , Oh D. , Bak J. G. , Baek G. W. , Sung C.
Published: July 2024

We developed a diamagnetic loop for the estimation of plasma stored energy in the KAIST Magnetic Mirror magnetic mirror device [Oh et al., J. Plasma Phys. 90, 975900202 (2024)]. Diamagnetic loops are used to estimate the plasma stored energy from measurements of the diamagnetic flux in plasma with an applied external magnetic field. However, diamagnetic flux measurements are accompanied by the vacuum flux, which generally exceeds the diamagnetic flux by over 10 000 times. Therefore, it is critical to attain a high signal-to-noise ratio with minimized noise in diamagnetic flux measurements. In this study, we employed a novel method to reduce background noise and improve the signal-to-noise ratio. Using two identical loops with opposite polarities, we successfully removed parasitic capacitive noise from the external insulation while amplifying the inductive signal two times. To eliminate the vacuum flux, we utilized two coaxial loops with different radii positioned at the same axial location. Results obtained from six paired loops confirmed the successful removal of the vacuum flux. The plasma stored energy was also found to agree well with Langmuir probe measurements, which verifies the diamagnetic flux measurements using the developed loop.
Isochronous bifurcations of magnetic islands in tokamaks
Authors: Fraile André C. , Roberto Marisa , Canal Gustavo P. , Caldas Iberê L.
Published: July 2024

On a rational magnetic surface, an isochronous bifurcation transforms one island chain into another chain with the same winding number. This transformation has been the subject of recent studies in tokamak plasmas. Namely, visco-resistive magnetohydrodynamic simulations of NSTX-U and DIII-D plasmas showed the onset of bifurcations with new magnetic isochronous islands for two competing helical perturbations on the same rational magnetic surface. To investigate these bifurcations, we use a cylindrical plasma model, with first-order correction for toroidicity, subject to externally applied magnetic perturbations, generated by a pair of resonant helical windings (RHWs) on the external wall and superposed to a helical current sheet (HCS) located on a rational plasma surface. We numerically integrate the magnetic field line equation and show that isochronous islands emerge when the perturbation created by the HCS increases. We present examples of such bifurcations on primary and secondary magnetic surfaces for different RHW configurations.
Influence of bow shape and model scale on the natural transition in boundary layers on underwater axisymmetric bodies with a superhydrophobic surface
Authors: Liu Bin , Zhang Yongming , Liu Jianhua
Published: July 2024

This study uses numerical methods to investigate the influence of bow shape and model scale on the natural transition in bow boundary layers on underwater axisymmetric bodies with a superhydrophobic surface. The transition locations for eight bow shapes and four model scales are predicted by using the eN method, which is based on a linear stability theory. The results show that the superhydrophobic surface always stabilizes the boundary layer and delays the transition for different bow shapes and model scales. However, differences are observed in the basic laminar flow, boundary-layer stability, and transition location when different bow shapes are used. These differences are not prominent at the small model scale, but become significant at the medium and large model scales. As the model scale increases, the transition location in the boundary layer on the superhydrophobic surface moves upstream and then downstream, leading to a “dangerous” scale, at which the transition location is closest to the leading edge. Furthermore, this study provides the optimal bow shape with the latest transition location at each model scale, and the optimal bow shape with the longest transition delay distance.
A diagnostic method of radial electron density distribution based on microwave transmission of cylindrical plasma along multipath
Authors: Zhao Chengwei , Li Xiaoping , Gao Jingru , Wei Qiang , Liu Yanming , Bao Weimin
Published: July 2024

Based on the multipath propagation phase shift of electromagnetic wave in cylindrical plasma, a method to obtain the radial electron density distribution of non-uniform cylindrical plasma is proposed in this paper. Focused lens antennas are used in multipath transmission distribution diagnosis (MTDD), where the propagation area in the plasma is approximately the size of the focal spot. The equivalent propagation thickness at each layer can be calculated for each path based on the propagation region and layer thickness. Combining with Fermat's shortest wavelength principle, electromagnetic waves propagate in a straight line between different layers. The phase shift caused by the propagation of electromagnetic waves in each layer, starting from the outermost layer, can obtain layer by layer electron density. To validate the MTDD method, multipath transmission propagation phase shift was simulated in CST, and the electron density distribution was obtained, which has a good agreement with the preset electron density. In addition, the MTDD method was applied to inductively coupled plasma, and the diagnostic results showed high agreement with the Langmuir probe results. The proposed MTDD method has higher spatial resolution than the transmission diagnosis method and can provide more precise plasma parameter information.
Influence of the rigid water column assumption on hydrodynamic system stability
Authors: Zhang Jian , Wang Qin-yi , Chen Long , Yao Tian-yu , Liu Yi , Xu Hui , Qiu Wei-xin
Published: July 2024

When analyzing the hydraulic vibration stability of hydrodynamic systems, a real elastic water column (EWC) is often simplified as a rigid water column (RWC) to derive theoretical stability criteria. This method is believed to yield results that deviate quantitatively from reality without causing qualitative errors. To examine this approach, this study first established a reservoir-pipe-valve-turbine system. Next, a theoretical stability criterion based on the RWC assumption was derived. Finally, the theoretical stability criterion of the real EWC (which was proven using the method of characteristics) was proposed to test the correctness of the RWC assumption, both numerically and theoretically. Results indicated discrepancies between RWC-based predictions and EWC time-domain outcomes, lacking consistent similarities. Specifically, in some cases, the RWC formula indicated instability, while the EWC theoretical criterion and numerical verification suggested stability. In other cases, the RWC formula indicated stability, while the EWC theoretical criterion and numerical verification suggested instability. Meanwhile, there were also cases where both the RWC formula and EWC theoretical criterion yielded consistent results. As the RWC assumption disregards water-hammer wave propagation and hydrodynamic system reflection effects, the validity of its conclusion is uncertain. Hence, when the RWC-based system stability contradicts the EWC theoretical criterion, the latter should guide system design decisions.
Hydrogen bubble evolution and gas transport mechanism on a microelectrode determined by cathodic potential and temperature
Authors: Lu Xinlong , Yadav Devendra , Wang Jiale , Jing Li , Zhu Yizhou , Ma Lijing , Jing Dengwei
Published: July 2024

Enhancing the efficiency of hydrogen production by optimizing gas product transfer within water electrolysis systems is essential. Employing high-speed photography and electrochemical techniques, the entire process of single hydrogen bubble evolution on a Pt microelectrode surface was measured. Results reveal a notable reduction in both bubble detachment radius and growth time with decreasing absolute potential (from −7 to −3 V) and increasing reaction temperature (from 30 °C to 50 °C). Additionally, a comprehensive model estimating bubble coverage on the microelectrode is presented, incorporating bubble radius and current as key influencing factors. This enables an accurate evaluation of mass transfer coefficients during bubble evolution in the absence of forced flow. Furthermore, findings reveal the dominance of bubble-induced micro-convection as the primary mass-transfer mechanism for gas products at high current densities [O (105–106 A/m2)]. The results also indicate that the mass transfer coefficient increases during the inertia-controlled growth stage of bubbles and decreases during the stage controlled by chemical reactions.
Optically controllable deformation and phase change in VO2/Si3N4/Au hybrid nanostructures with polarization selectivity
Authors: Zhang Xiaochen , Li Yuan , Dong Weikang , Liang Qinghua , Sun Haozhe , Wang Yang , Li Xiaowei , Jiang Lan , Zhang Xinping , Ma He , Li Jiafang
Published: July 2024

Optically spatial displacement and material modification hold great potential for the appealing applications in nanofabrication and reconfiguration of functional optical devices. Here, we propose and demonstrate a scheme to achieve simultaneous deformation and phase change in vanadium dioxide (VO2)/Si3N4/Au hybrid nanostructures by laser stimuli. Low triggering threshold and significant deformation characteristics of VO2, based on controllable phase transition, are demonstrated in microscale cantilevers. The plasmonic properties of the nanostructure array are further utilized to achieve a polarization-selective dynamic response. The persistence of deformation and dynamical optical modulation are further demonstrated. Such high-precision fabrication methods and non-contact reconfiguration methods are useful for future applications in dynamic optical manipulation.
Acoustic-streaming driven liquid filling patterns inside through-glass vias
Authors: Sun Yadong , Li Jingjun , Wang Xiukun , Lu Wanting , Chai Xinyu , Zhang Lei
Published: July 2024

Filling through-glass vias (TGVs) with liquid remains a significant challenge in IC packaging technology. This study presents an acoustic-streaming method to modulate the wetting behavior as well as the interfacial dynamics to fill the TGVs. We categorize the incomplete filling into three typical patterns: (a) neck wetting, (b) head and end wetting, and (c) bubble wrapping. Experimental results show that the ultrasonic driving at 522.5 kHz/160  V can effectively achieve ideal filling of these patterns in TGVs (aspect ratio of 1:2/1:3). The filling processes are elucidated from a new perspective: the liquid flow induced by acoustic streaming regulates the moving of contact line to complete wetting on sidewalls, while the acoustic wave impacts the gas–liquid interface to cause oscillations for pushing bubbles out. A Lattice Boltzmann model is constructed to reveal the mechanism. This method offers a viable and promising solution to promote liquid filling of TGVs.
Non-Oberbeck–Boussinesq effects on a differentially heated vertical cavity with high-Prandtl number fluid
Authors: Pan Xiaomin
Published: July 2024

This study explores the non-Oberbeck–Boussinesq (NOB) effects on hydrodynamics and heat transport in two-dimensional glycerol-filled differentially heated vertical cavity (DHVC). The simulations span Rayleigh numbers (Ra) from 2×103 to 5×109 and temperature difference (Δθ̃) up to 50 K at a Prandtl number (Pr) of 2547. We showed the emergence of stratified flow structures, delineated the NOB effects on temperature distribution symmetry, and analyzed the scaling behaviors of the Nusselt number (Nu), Reynolds number (Re), and thermal boundary layer (BL) thicknesses (λ¯hθ and λ¯cθ) against Ra. For Ra≥3×105, the stratification number (S) shows reduced sensitivity to changes in Ra, stabilizing around 0.5. Additionally, the center temperature (θcen) appears to be unaffected by Ra and increases linearly with Δθ̃ for Ra>106, satisfying θcen≈2.99×10−3K−1Δθ̃. Our results also revealed that Nu∼Raγ Nu and Re∼RaγRe with 0.2649≤γ Nu≤0.2654 and 0.3633≤γ Re≤0.3643, respectively, where γ Nu and γ Re exhibit a monotonic decrease as NOB effects intensify. For all investigated Ra values, NuNOB/NuOB<1 and ReNOB/ReOB>1 hold consistently, with deviations from OB predictions capped at 6.38% and 2.63% for Ra≥108, respectively. The analysis of thermal BL thickness reveals distinct scaling behaviors, characterized by λ¯h,cθ∼Raγ λ¯ h, c, with scaling exponents ranging from −0.2690 to −0.2669 for both OB and NOB scenarios. Notably, it reveals a divergence from water-based DHVC trends, showing linear decreases in the hot wall's scaling exponent and increases for the cold wall.
Correcting force error-induced underestimation of lattice thermal conductivity in machine learning molecular dynamics
Authors: Wu Xiguang , Zhou Wenjiang , Dong Haikuan , Ying Penghua , Wang Yanzhou , Song Bai , Fan Zheyong , Xiong Shiyun
Published: July 2024

Machine learned potentials (MLPs) have been widely employed in molecular dynamics simulations to study thermal transport. However, the literature results indicate that MLPs generally underestimate the lattice thermal conductivity (LTC) of typical solids. Here, we quantitatively analyze this underestimation in the context of the neuroevolution potential (NEP), which is a representative MLP that balances efficiency and accuracy. Taking crystalline silicon, gallium arsenide, graphene, and lead telluride as examples, we reveal that the fitting errors in the machine-learned forces against the reference ones are responsible for the underestimated LTC as they constitute external perturbations to the interatomic forces. Since the force errors of a NEP model and the random forces in the Langevin thermostat both follow a Gaussian distribution, we propose an approach to correcting the LTC by intentionally introducing different levels of force noises via the Langevin thermostat and then extrapolating to the limit of zero force error. Excellent agreement with experiments is obtained by using this correction for all the prototypical materials over a wide range of temperatures. Based on spectral analyses, we find that the LTC underestimation mainly arises from increased phonon scatterings in the low-frequency region caused by the random force errors.
Unsteady wake and heat transfer characteristics of three tandem circular cylinders in forced and mixed convection flows
Authors: Zhu Hongjun , Zhong Jiawen , Liu Bin , Zhou Tongming
Published: July 2024

In natural convection (high Richardson number Ri), a high Prandtl number (Pr) leads to thinner thermal boundary layers, enlarging the thermal gradient and hence the enhancement of buoyancy effect. In forced convection (low Ri), a high Pr introduces thicker velocity boundary layers. In mixed convection scenarios, where both forced and natural convection are significant, the interaction between Pr and Ri determines the resultant flow pattern and heat transfer characteristic. Three tandem circular cylinders with an identical spacing ratio of 4.0 in both forced and mixed convection flows were numerically investigated by using finite element method. The computations were carried out in the range of Pr = 5–50 and Ri = 0–2 at a low Reynolds number of Re = 150. The results of the squared strain rate and the vorticity shed light on the enstrophy transfer process. Thermal plume structures in the far wake originate from the upper dispersed vortices due to the high superimposed buoyancy at low Pr, while they are suppressed at high Pr. The increase in Pr plays a role as the flow stabilization, while the growth of Ri plays the reverse role. The time-averaged velocity, pressure coefficient, and temperature become more asymmetrical at high Ri. The Nusselt number of the upstream cylinder is approximately equal to the empirical result without the consideration of thermal buoyancy. Due to the thermal buoyancy, the migration of shear layers along the cylinder surface leads to the frequency alteration and harmonic frequency in the drag, lift, and Nusselt coefficients.
Permittivity measurement of high-frequency substrate based on the double-sided parallel-strip line resonator method
Authors: Shen Ronghua , Gao Chong , Chen Nan , Zhu Hui , Zhou Yang , Yu Chengyong , Li En , Zhang Yunpeng
Published: July 2024

With the development of 5G technology, the accurate measurement of the complex permittivity of a printed circuit board (PCB) in the wide frequency range is crucial for the design of high-frequency circuits. In this paper, a microwave measurement device and method based on the double-sided parallel-strip line (DSPSL) resonator have been developed to measure the complex permittivity of typical PCBs in the vertical direction. The device includes the DSPSL resonator, the DSPSL coupling probe, a pressure monitor, a Farran C4209 vector network analyzer (100 K to 9 GHz), and a FEV-10-PR-0006 frequency multiplier (75–110 GHz). Based on transmission line theory, the physical model of the DSPSL resonator was established, and the relative permittivity and loss angle tangent value of the dielectric substrate were calculated using conformal transformation. To excite the resonator, the DSPSL coupling probe with a good transmission effect was designed, which consists of DSPSL microstrip line (MSL) transition structure and an MSL-WR10 rectangular waveguide converter. To reduce the air gap between the sample and the metal guide band and dielectric support block, and to improve test accuracy, a mechanical pressure device is added to the top of the DSPSL resonator. Based on the DSPSL resonator, we have used the device to test four typical PCBs, namely, polytetrafluoroethylene, Rogers RT/duroid®5880, Rogers RO3006®, and Rogers RO3010®. The results show that the maximum error of the relative permittivity is less than 3.05%, and the maximum error of the loss angle tangent is less than 1.27 × 10−4.
Detection of the irrotational boundary using machine learning methods
Authors: Tao Shancong , Xie Yuanliang , Shi Xiaotian , Zhou Yi
Published: July 2024

Four machine learning methods, i.e., self-organizing map (SOM), Gaussian mixture model (GMM), eXtreme gradient boosting (XGBoost), and contrastive learning (CL), are used to detect the irrotational boundary (IB), which represents the outer edge of the turbulent and non-turbulent interface layer. To accurately evaluate the detection methods, high-resolution databases from direct numerical simulations of a temporally evolving turbulent plane jet are used. It is found that except for the SOM method, the general contour of the IB appears to be effectively captured using the GMM, XGBoost, and CL methods, which indicate the turbulent and non-turbulent regions can be roughly recognized. Furthermore, the intrinsic features of the detected IB using the GMM, XGBoost, and the CL methods are quantitatively evaluated. Unlike the conventional vorticity norm method, the three machine learning methods do not rely on a single threshold of vorticity magnitude to separate the turbulent and non-turbulent regions. A small part of the detected IB using the three machine learning methods is characterized by the rotational motions, which are expected to be only found inside the turbulent sublayer and turbulent core region. Compared to the vorticity norm and XGBoost methods, the fractal dimensions of the IB detected by the GMM and CL methods are relatively small, which are related to the missing detection of some highly contorted elements. With the three machine learning methods, a large part of the detected IB is characterized by a convex shape, similarly as with the vorticity norm. However, the probability density function profiles of the local curvature of the detected IB differ greatly between the three machine learning methods and the vorticity norm. A mild variation of the mean conditional distributions of the vorticity magnitude can be observed across the detected IB by the three machine learning methods. This study first implies that using the machine learning methods the turbulent and non-turbulent regions can be roughly distinguished, but it is still challenging to obtain the intrinsic features of the detected IB.
Construction of a cryogenic dual scanner magnetic force microscope equipped with piezoresistive cantilever
Authors: Lee Jungsub , Kim Jeehoon
Published: July 2024

We present a low-temperature magnetic force microscope (MFM) incorporating a piezoresistive cantilever and a dual-range scanner for experiments across a wide temperature range from cryogenic levels to room temperature. The piezoresistor-based MFM eliminates the need for optical readjustment, typically required due to thermal expansion at varying temperatures, thereby providing a more stable and precise measurement environment. The integration of a dual scanner system expands the versatility of scanning operations, enabling accurate sample positioning for detailed exploration of magnetic and superconducting properties under diverse thermal conditions. To demonstrate the capabilities of our MFM, we show detailed imaging of Fe3GaTe2, a van der Waals ferromagnet, and Yb0.7Y0.3CuAs2, a ferromagnetic cluster glass material. These studies demonstrate the potential of our MFM in revealing intricate details of magnetic domain dynamics and contribute to our understanding of materials exhibiting the anomalous Hall effect as well as superconducting phenomena.
Vertical coherence of coherent structures during sand and dust storms: A multi-height synchronous observation study
Authors: Li Xuebo , Hu Lan , Hu Xin , Li Peng , Xu Xiaowei
Published: July 2024

An experiment was conducted on the Qingtu Lake Observation Array (QLOA) to measure wind and dust information at various wall-normal heights during the sand and dust storm (SDS) process. According to the indicators of the non-stationary features in the flow field, the SDS process can be divided into three stages: ascending, stabilizing, and descending. Based on this division, the Hilbert–Huang transform (HHT) is employed to extract dominant flow structures, which carries a significant portion of the turbulent kinetic energy. Moreover, the HHT spectrum of stream-wise velocity component reveals that the scales of the dominant structures are approximately hundreds of meters in the horizontal direction, and hence suggests the presence of large and very large-scale coherence during the SDS. The hypotheses of Townsend [The Structure of Turbulent Shear Flow (Cambridge University Press, 1976)] and Davenport [“The spectrum of horizontal gustiness near the ground in high winds,” Q. J. R. Meteorol. Soc. 87, 194–211 (1961)] are utilized to demonstrate the vertical coherence of turbulence, which suggests the wall-similarity and evolution of inner/outer interactions for coherent structures during the SDS. Finally, the coherence spectrum [γL2=exp(−2c1Δz/λx)] and the linear transfer kernel [|HL2|=exp(d1−d2Δz/λx)] are parameterized, where c1, d1, d2 are fitting parameters, Δz is wall-normal offset, and λx refers to streamwise wavelength, to illustrate the evolution of the interactions between near-wall and outer regions during the SDS, which highlights the strong connections during the stabilizing stage. In general, the present study analyzed horizontal and wall-normal structures for a comprehensive SDS process, and thus, these findings present abundant features of wall-attached eddies which further be used to improve/enrich existing near-wall models.
Preliminary investigation of yaw stability in undulatory fish propulsion using stability derivatives
Authors: Zhou TianYi , Xu MengFan , Yu YongLiang
Published: July 2024

Fish are capable of maintaining a stable forward direction without yawing during long-distance movements. This long-term yaw stability has been investigated using static derivatives, revealing that undulatory locomotion is highly unstable. However, the present simulation of the perturbation development process shows that the yaw perturbation growth rate of the undulatory fish is an order of magnitude smaller than that of non-undulatory one. This study investigates the yaw stability of two-dimensional fish body undergoing the carangiform undulatory deformation by considering both the mean static and dynamic derivatives method. The results indicate that the yaw instability always occurs when the fish body is in undulatory propulsion or coasting model, and the undulation has stabilizing effect compared with the body straight in the uniform incoming flow. Analysis of the mean derivatives reveals that the stabilizing effect is due to the negative value of the dynamic derivative, which plays the role of damping, although the static derivative indicates that the yaw is unstable. Utilizing mean derivatives method can analyze qualitatively the linear stability at the equilibrium point, which cannot provide an assessment of overall stability.
Complex dynamics of partially freezable confined water revealed by combined experimental and computational studies
Authors: Steinrücken Elisa , Weigler Max , Kloth Sebastian , Vogel Michael
Published: July 2024

We investigate water dynamics in mesoporous silica across partial crystallization by combining broadband dielectric spectroscopy (BDS), nuclear magnetic resonance (NMR), and molecular dynamics simulations (MDS). Exploiting the fact that not only BDS but also NMR field-cycling relaxometry and stimulated-echo experiments provide access to dynamical susceptibilities in broad frequency and temperature ranges, we study both the fully liquid state above the melting point Tm and the dynamics of coexisting water and ice phases below this temperature. It is found that partial crystallization leads to a change in the temperature dependence of rotational correlation times τ, which occurs in addition to previously reported dynamical crossovers of confined water and depends on the pore diameter. Furthermore, we observe that dynamical susceptibilities of water are strongly asymmetric in the fully liquid state, whereas they are much broader and nearly symmetric in the partially frozen state. Finally, water in the nonfreezable interfacial layer below Tm does not exhibit a much debated dynamical crossover at ∼220 K. We argue that its dynamics is governed by a static energy landscape, which results from the interaction with the bordering silica and ice surfaces and features a Gaussian-like barrier distribution. Consistently, our MDS analysis of the motional mechanism reveals a hopping motion of water in thin interfacial layers. The rotational correlation times of the confined ice phases follow Arrhenius laws. While the values of τ depend on the pore diameter, freezable water in various types of confinements and mixtures shows similar activation energies of Ea ≈ 0.43 eV.
Emergence of boundary conditions in the heat equation
Authors: Chung Jaywan , Kang Seungmin , Kim Ho-Youn , Kim Yong-Jung
Published: July 2024

The Dirichlet and Neumann conditions are commonly employed as boundary conditions for the heat equation, yet their legitimacy is debatable in certain scenarios. This paper aims to demonstrate that, in fact, diffusion laws autonomously select boundary conditions. To illustrate this, we incorporate the bounded domain into a larger domain with a diffusivity parameter ϵ > 0 and examine the solution’s behavior at the interface. Our findings reveal that homogeneous Neumann or Dirichlet boundary conditions emerge as ϵ → 0, contingent upon the type of the heterogeneous diffusion.
High-resolution urban temperature simulation method considering various spatiotemporal boundary impacts
Authors: Zhu Hao-Cheng , Xi Chang , Ren Chen , Wang Junqi , Cao Shi-Jie
Published: July 2024

Climate change has heightened the frequency and intensity of extreme heat events in cities, greatly impacting human health, the environment, and socio-economic activities, particularly in densely populated areas. Canopy temperature (T2m) is a key indicator of whether urban area extreme heat is occurring, with significant implications for public health, energy consumption, and pollution levels. However, the diverse urban topography, functional layout, and human activities contribute to significant variations in the distribution of T2m. While computational fluid dynamics (CFD) models offer high-resolution T2m simulations, complexities in urban spatial and temporal dynamics make accurately defining boundary conditions challenging, potentially leading to large simulation errors. This study addressed the challenge of determining precise boundary conditions for urban CFD simulations by employing the Weather Research and Forecasting model to integrate meteorological reanalysis data. Different meteorological reanalysis datasets used to simulate T2m were compared, including Final Operational Global Analysis, Global Forecast System, and European Centre for Medium-Range Weather Forecasts Reanalysis v5. When combined with the reanalysis data, the minimum mean relative error of simulated T2m was 4%, which is a threefold improvement in accuracy compared to traditional meteorological boundary conditions. This study provides technical support for refined zoning of urban extreme heat risk and urban management in the context of climate change.
Enumerating low-frequency nonphononic vibrations in computer glasses
Authors: Lerner Edan , Moriel Avraham , Bouchbinder Eran
Published: July 2024

In addition to Goldstone phonons that generically emerge in the low-frequency vibrational spectrum of any solid, crystalline or glassy, structural glasses also feature other low-frequency vibrational modes. The nature and statistical properties of these modes—often termed “excess modes”—have been the subject of decades-long investigation. Studying them, even using well-controlled computer glasses, has proven challenging due to strong spatial hybridization effects between phononic and nonphononic excitations, which hinder quantitative analyses of the nonphononic contribution DG(ω) to the total spectrum D(ω), per frequency ω. Here, using recent advances indicating that DG(ω)=D(ω)−DD(ω), where DD(ω) is Debye’s spectrum of phonons, we present a simple and straightforward scheme to enumerate nonphononic modes in computer glasses. Our analysis establishes that nonphononic modes in computer glasses indeed make an additive contribution to the total spectrum, including in the presence of strong hybridizations. Moreover, it cleanly reveals the universal DG(ω)∼ω4 tail of the nonphononic spectrum, and opens the way for related analyses of experimental spectra of glasses.
Internal strain identification of seed-layered ZrO2, aluminum-, and yttrium-doped ZrO2 thin films via grazing incidence x-ray diffraction
Authors: Seo Haengha , Park Han Sol , Cho Seong Tak , Shin Jonghoon , Lim Junil , Kim Tae Kyun , Paik Heewon , Song Haewon , Hwang Cheol Seong
Published: July 2024

Grazing incidence x-ray diffraction reveals that conventional post-deposition-annealed ZrO2 and in situ crystallized (by local epitaxy) ZrO2 thin films (<15 nm) have different internal strain states. A comparison between single- and two-step grown films enables the diverse strain components to be discretely identified. In particular, thickness-dependent intrinsic growth strain is unevenly distributed within the film according to the Volmer–Weber growth. Furthermore, extrinsic thermal strain, locally present in the annealed seed layer, does not spread over the in situ crystallized upper main layer of the two-step film. Post-deposition annealing of the two-step film renders the strain state identical to the single-step films by imposing thermal strain on the in situ crystallized main layer. Local strains created by diffused aluminum and yttrium dopants are also examined. Since each stress factor plays a vital role in the phase formation and electrical behaviors of ZrO2 and other fluorite-structure films, this method will pave the way for understanding the film's internal strain distribution and accompanying performance engineering.
Numerical study of the effects of discontinuous ice on three-dimensional wings
Authors: Chen Jiawei , Zhang YuFei , Fu Song
Published: July 2024

Ice accretion has adverse effects on aircraft, so it is very important to study the flow field of iced wings. Unlike previous studies that typically focused on continuous ice, this paper conducts a numerical study of the flow field around discontinuous ice. A modified laminar-turbulent transition model that incorporates large separation correction is employed for the study of discontinuous ice. An iced swept wing was chosen to validate the modified model's capability in predicting aerodynamic performance. The impact of discontinuous ice on both straight and swept wings was studied. For the straight wing, the effect of discontinuous ice with different gap widths on aerodynamic characteristics was investigated. The results show that the reduction in lift caused by discontinuous ice is typically lower than that caused by continuous ice. However, at angles of attack less than 7°, small-gap discontinuous ice causes more substantial reductions in lift compared to continuous ice. This is because small-gap ice causes greater separation at the leading edge, significantly reducing the suction peak of pressure. For the swept wing, the effect of sweep on discontinuous ice was studied. It was found that the swept effect causes asymmetric separation behind the ice shape. At higher angles of attack (greater than 4°), the impact of different ice configurations on lift shows an opposite trend on swept wings compared to straight wings.
On the onset of splashing of liquid metal drops in a viscous non-oxidizing environment
Authors: Agarwal Rahul , Mohamad A. A.
Published: July 2024

This Letter explores the onset of splashing of liquid metal drops and the underlying phenomenological reasons using a numerical approach. Validation is performed using experimental measurements, threshold splashing parameters, and by comparing splashing patterns. A significant observation is made: The ejection of the daughter droplet occurs toward the center of the mother drop instead of radially ejecting it outward. In the presence of a viscous medium, a significantly higher ejection angle of the daughter droplet between 90° and 130° is measured, compared to an air medium (average ejection angle of ∼10.6°). This work opens new avenues for further exploration of the broader topic of drop impact on a surface in viscous environments.
A highly sensitive modified triple split ring metamaterial-based sensor for blood sample detection based on dielectric property alteration
Authors: Al Mahfazur Rahman Abdullah , Islam Mohammad Tariqul , Kirawanich Phumin , Bais Badariah , Alsaif Haitham , Maash Abdulwadoud A. , Hoque Ahasanul , Moniruzzaman Md. , Islam Md. Shabiul , Soliman Mohamed S.
Published: July 2024

This research paper demonstrates a metamaterial (MTM) based sensing technique to detect various blood samples by analyzing their dielectric properties. The performance of this MTM-based sensor is evaluated with the help of mimicked human blood samples that closely resemble the dielectric properties of actual human blood samples. Moreover, the ISM band frequency of 2.4 GHz is chosen as one of the reference resonance frequencies due to its various industrial and medical applications. The resonating patch is developed on the FR-4 substrate with a dimension of 10 × 20 mm2 that provides sharp reference resonances of 2.4 and 4.72 GHz for the spectra of the transmission coefficient with a good quality factor (Q-factor). The MTM sensor can detect the mimicked blood samples with a maximum frequency deviation of up to 650 MHz at 2.4 GHz and up to 850 MHz at 4.72 GHz, with maximum sensitivity of 0.917 and 0.707, respectively. The measured results using the prototype of the sensor support the simulation result with good agreement, indicating high sensing capability. Due to its high sensitivity, figure of merit (FoM), and frequency shifting with dielectric property changes in blood samples, the developed MTM-based sensor can be implemented effectively for quick sensing of infected blood samples and biomedical applications.
Unveiling unconventional CH4–Xe compounds and their thermodynamic properties at extreme conditions
Authors: Zhang Pan , Ding Yuelong , Cui Wenwen , Hao Jian , Shi Jingming , Li Yinwei
Published: July 2024

Inert gases (e.g., He and Xe) can exhibit chemical activity at high pressure, reacting with other substances to form compounds of unexpected chemical stoichiometry. This work combines first-principles calculations and crystal structure predictions to propose four unexpected stable compounds of CH4Xe3, (CH4)2Xe, (CH4)3Xe, and (CH4)3Xe2 at pressure ranges from 2 to 100 GPa. All structures are composed of isolated Xe atoms and CH4 molecules except for (CH4)3Xe2, which comprises a polymerization product, C3H8, and hydrogen molecules. Ab initio molecular dynamics simulations indicate that pressure plays a very important role in the different temperature driving state transitions of CH4–Xe compounds. At lower pressures, the compounds follow the state transition of solid–plastic–fluid phases with increasing temperature, while at higher pressures, the stronger Xe–C interaction induces the emergence of a superionic state for CH4Xe3 and (CH4)3Xe2 as temperature increases. These results not only expand the family of CH4–Xe compounds, they also contribute to models of the structures and evolution of planetary interiors.
Generalized quantum master equations can improve the accuracy of semiclassical predictions of multitime correlation functions
Authors: Sayer Thomas , Montoya-Castillo Andrés
Published: July 2024

Multitime quantum correlation functions are central objects in physical science, offering a direct link between the experimental observables and the dynamics of an underlying model. While experiments such as 2D spectroscopy and quantum control can now measure such quantities, the accurate simulation of such responses remains computationally expensive and sometimes impossible, depending on the system’s complexity. A natural tool to employ is the generalized quantum master equation (GQME), which can offer computational savings by extending reference dynamics at a comparatively trivial cost. However, dynamical methods that can tackle chemical systems with atomistic resolution, such as those in the semiclassical hierarchy, often suffer from poor accuracy, limiting the credence one might lend to their results. By combining work on the accuracy-boosting formulation of semiclassical memory kernels with recent work on the multitime GQME, here we show for the first time that one can exploit a multitime semiclassical GQME to dramatically improve both the accuracy of coarse mean-field Ehrenfest dynamics and obtain orders of magnitude efficiency gains.
Ultralow-field MRI machine could cost less than a car
Authors: Lopatka Alex
Published: July 2024

The prototype medical device, whose AI-processed images show features similar to those from a typical instrument with a strong magnetic field, could increase MRI access.
Metabolic adaptation to lactation of dairy cows in two contrasting facilities involving partial confinement plus grazing or total confinement
Authors: Mendina G. R. , Damián J. P. , Meikle A. , Méndez M. N. , Chilibroste P. , Adrien M. L.
Published: July 2024

Context The increasing intensification of pasture-based systems has subjected the cows to different productive environments, which could affect physiological responses and, consequently, their productive performance. Aims The aim was to determine the effect of contrasting housing facilities (outdoor soil-bedded vs compost-bedded pack barn) used in partial confinement in pasture-based systems, on the metabolic adaptation during early lactation and its impact on productive and reproductive performance of autumn- and spring-calving dairy cows, having as a positive control a zero-grazing confined system in compost barn. Methods Multiparous Holstein dairy cows that calved in autumn (n = 36) and spring (n = 48) were distributed in the following three treatments from calving to 90 days in milk (DIM): outdoor soil-bedded–grazing (OD-GRZ), compost barn–grazing (CB-GRZ), compost barn–total mixed ration (CB-TMR). Milk production, total milksolids (TMS), body condition score, non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), cholesterol, insulin, insulin-like growth factor-1 (IGF-1), and the proportion of cows with corpus luteum were determined in repeated measurements. Key results In both calving seasons, milk production and TMS yields did not differ between OD-GRZ and CB-GRZ, but were greater in CB-TMR (P < 0.0001). In autumn, NEFA and BHB were not affected by treatments, but cholesterol increased faster in CB-TMR (P = 0.0500). In spring, NEFA and cholesterol concentrations were not affected by treatment, but BHB remained greater in OD-GRZ until 90 DIM than in the other treatments. IGF-1 and insulin did not differ between treatments in autumn, but in spring, IGF-1 was greater in CB-TMR (P < 0.0001). The proportion of cows with corpus luteum was not different between pasture-based treatments, but both were greater than CB-TMR up to 40 DIM in autumn (P = 0.0489) and during the entire study in spring CB-TMR (P = 0.0285). Conclusions Although no differences were found among housing facilities in partial confinement, except that in spring OD-GRZ cows had greater BHB concentrations, confined cows prioritised milk production instead of reproductive function, despite presenting better energy indicators than did pasture-based cows. Implications Outdoor housing combined with grazing can increase the risk of greater BHB concentrations, indicative of subclinical ketosis, under heat-stress conditions, when compared with indoor housing. Confined cows increased milk production but had a delay in the resumption of ovarian cyclicity, even having a better energy status than pasture-based cows.
A typology of HIV self-testing support systems: a scoping review
Authors: Tran Arron , Tran Nghiep , Tapa James , Tieosapjaroen Warittha , Fairley Christopher K. , Chow Eric P. F. , Zhang Lei , Baggaley Rachel C. , Johnson Cheryl C. , Jamil Muhammad S. , Ong Jason J.
Published: July 2024

To maximise the benefits of HIV self-testing (HIVST), it is critical to support self-testers in the testing process and ensure that they access appropriate prevention and care. To summarise systems and tools supporting HIVST (hereafter, ‘support systems’) and categorise them for future analysis, we synthesised the global data on HIVST support systems and proposed a typology. We searched five databases for articles reporting on one or more HIVST support systems and included 314 publications from 224 studies. Across 189 studies, there were 539 reports of systems supporting HIVST use; while across 115 studies, there were 171 reports of systems supporting result interpretation. Most commonly, these were pictorial instructions, followed by in-person demonstrations and in-person assistance while self-testing or reading self-test results. Less commonly, virtual interventions were also identified, including online video conferencing and smartphone apps. Smartphone-based automated result readers have been used in the USA, China, and South Africa. Across 173 studies, there were 987 reports of systems supporting post-test linkage to care; most commonly, these were in-person referrals/counselling, written referrals, and phone helplines. In the USA, Bluetooth beacons have been trialled to monitor self-test use and facilitate follow-up. We found that, globally, HIVST support systems use a range of methods, including static media, virtual tools, and in-person engagement. In-person and printed approaches were more common than virtual tools. Other considerations, such as linguistic and cultural appropriateness, may also be important in the development of effective HIVST programs.
Capturing alterations of intracellular–extracellular lactate distribution in the brain using diffusion-weighted MR spectroscopy in vivo
Authors: Malaquin Sophie , Lerchundi Rodrigo , Mougel Eloïse , Valette Julien
Published: July 2024

While the intracellular–extracellular distribution of lactate has been suggested to play a critical role in the healthy and diseased brain, tools are lacking to noninvasively probe lactate in intracellular and extracellular spaces. Here, we show that, by measuring the diffusion of lactate with diffusion-weighted magnetic resonance (MR) spectroscopy in vivo and comparing it to the diffusion of purely intracellular metabolites, noninvasive quantification of extracellular and intracellular lactate fractions becomes possible. More specifically, we detect alterations of lactate diffusion in the APP/PS1 mouse model of Alzheimer’s disease. Data modeling allows quantifying decreased extracellular lactate fraction in APP/PS1 mice as compared to controls, which is quantitatively confirmed with implanted enzyme-microelectrodes. The capability of diffusion-weighted MR spectroscopy to quantify extracellular–intracellular lactate fractions opens a window into brain metabolism, including in Alzheimer’s disease.
High burden of viruses and bacterial pathobionts drives heightened nasal innate immunity in children
Authors: Watkins Timothy A. , Green Alex B. , Amat Julien A.R. , Cheemarla Nagarjuna R. , Hänsel Katrin , Lozano Richard , Dudgeon Sarah N. , Germain Gregory , Landry Marie L. , Schulz Wade L. , Foxman Ellen F.
Published: July 2024

Studies during the COVID-19 pandemic showed that children had heightened nasal innate immune responses compared with adults. To evaluate the role of nasal viruses and bacteria in driving these responses, we performed cytokine profiling and comprehensive, symptom-agnostic testing for respiratory viruses and bacterial pathobionts in nasopharyngeal samples from children tested for SARS-CoV-2 in 2021–22 (n = 467). Respiratory viruses and/or pathobionts were highly prevalent (82% of symptomatic and 30% asymptomatic children; 90 and 49% for children <5 years). Virus detection and load correlated with the nasal interferon response biomarker CXCL10, and the previously reported discrepancy between SARS-CoV-2 viral load and nasal interferon response was explained by viral coinfections. Bacterial pathobionts correlated with a distinct proinflammatory response with elevated IL-1β and TNF but not CXCL10. Furthermore, paired samples from healthy 1-year-olds collected 1–2 wk apart revealed frequent respiratory virus acquisition or clearance, with mucosal immunophenotype changing in parallel. These findings reveal that frequent, dynamic host–pathogen interactions drive nasal innate immune activation in children.
STAT3 gain of function: Too much of a good thing in the skin!
Authors: Ma Cindy S. , Tangye Stuart G.
Published: July 2024

Germline activating mutations in STAT3 cause a multi-systemic autoimmune and autoinflammatory condition. By studying a mouse model, Toth et al. (https://doi.org/10.1084/jem.20232091) propose a role for dysregulated IL-22 production by Th17 cells in causing some aspects of immune-mediated skin inflammation in human STAT3 GOF syndrome.