bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dissipation on the characteristics of small Josephson junctions. Suppression of Bloch oscillations
Authors: Odintsov A. A.
Published: January 2025

The IV characteristics of a Josephson junction of low capacitance subjected to a harmonic signal of frequency Ω are determined in the strong-bond limit for an arbitrary value of the ohmic dissipation α. It is shown that for α < 1, the interaction of external signal harmonics with Bloch oscillations results in the appearance of “voltage steps” in IVC at currents In = neΩ/π. With increasing α, these steps are smeared because of a suppression of Bloch oscillations by dissipation.
Low-temperature peculiarities of the spectrum of binary amorphous ferromagnets
Authors: Naimark M. B. , Dovgopol S. P.
Published: January 2025

The change in the low-temperature excitation spectrum due to amorphization of a binary ferromagnetic system is calculated by using the model of collective magnetic coordinates. The dependence of the Curie temperature on the nonmagnetic component concentration is plotted both for a binary amorphous and a binary crystalline system. A roton minimum is shown to appear in the excitation spectrum of a binary amorphous system for a magnetic component concentration close to the critical concentration of ferromagnetism.
Magnetic field induced anisotropy of resistance in YBa2Cu3Ox polycrystals
Authors: Glukhov A. M. , Fogel’ N. Ya. , Dmitrenko I. M. , Pokhila A. S. , Braude I. S. , Demirskii V. V. , Dotsenko V. I.
Published: January 2025

A magnetic field induced anisotropy of resistance for different current directions relative to the magnetic field in the superconducting transition region is observed for YBa2Cu3Ox polycrystals with a random equiprobable angular distribution of monocrystalline grain orientations. The anisotropy is shown to be mainly due to the anisotropy in the normal resistance of grains constituting a polycrystal. A stronger anisotropy of the opposite sign is observed in samples with pronounced texture. The anisotropy in isotropic polycrystals vanishes on approaching the percolation threshold and in the vicinity of the superconducting transition temperature.
Fluctuation effects in specific heat of YBa2Cu3O7−δ single crystals
Authors: Babich I. M. , Mikitik G. P.
Published: January 2025

An explanation is offered for the results obtained by S. E. Inderhees et al. [Phys. Rev. Lett. 60, 1178 (1988)] who studied experimentally the fluctuation contribution to the specific heat of YBa2Cu3O7−δ single crystals.
Point contact spectroscopy of superconductors with a strong electron–phonon interaction
Authors: Omel’yanchuk A. N. , Beloborod’ko S. I. , Kulik I. O.
Published: January 2025

It is shown that as in the case of tunnel junctions, the nonlinearity of the current–voltage characteristics (IVC) of superconducting point contacts can be used to obtain the dependence of the order parameter on energy and to reconstruct the electron–phonon interaction (EPI) function through an inversion of the Eliashberg equations. The effect of the electron spectrum renormalization due to EPI on the steady-state IVC of an S–c-N contact is studied. This effect leads to a nonlinear conductivity which is manifested in the form of peaks in the region of characteristic phonon energies. The correction to the point-contact current, which is a manifestation of the elastic scattering of electrons by nonequilibrium phonons generated by the electron flow in the region of a microconstriction, is determined: The correction fixes the phonons near the Van-Hove singular points on the phonon spectrum.
Properties of CO-Ar solid solutions near the critical concentration point
Authors: Brodyanskii A. P. , Prokhvatilov A. I. , Yantsevich L. D.
Published: January 2025

Detailed X-ray diffraction studies of the temperature-concentration dependence of the lattice parameters and molar volumes of hcp solid solutions of CO–Ar have been carried out near the critical concentration point. The value of the critical index is calculated and found to be β = 0.50 ± 0.05. Such a behavior of solid CO–Ar solutions is explained. It is shown that the obtained experimental data and the results of calculations of the orientational pressure in solid solutions on the curve of coexistence of isomorphic phase and in the supercritical region point towards the orientational nature of the emergence of the critical concentration point observed in the CO–Ar system.
Thermal conductivity of superconducting YBa2Cu3O6.9 ceramic samples
Authors: Efimov V. B. , Levchenko A. A. , Mezhov-Deglin L. P. , Nikolaev R. K. , Sidorov N. S.
Published: January 2025

The results of measurements of thermal conductivity T in YBa2Cu3O6.9 ceramic samples in the temperature interval from 0.4 to 150 K and their electrical conductivity above Tc are presented. The maxima on the T (T) curves in the superconducting state at T≃0.5Tc may be related to the electron–phonon interaction as in the case of metal superconductors with a strong electron–phonon interaction.
An investigation of silver-nanoparticle-modified TiO2 substrates for photocatalytic oxidation in wastewater treatment
Authors: Arulsamy Jackson Joseph , Henry Prunier Joy Prabu , Arockiasamy Felix Sahayaraj , Irudhayaraj Johnson , Thaninayagam Ebenezer , Ravi Gopi Rajakannu , Selvam Snowlin Venice
Published: January 2025

This research aims to explore the decoration of TiO2 substrates with silver nanoparticles as a means of enhancing the photocatalytic oxidation of organic compounds. The results show that decorated TiO2 substrates exhibit significantly higher photocatalytic activity in sunlight than undecorated substrates. Morphological analysis is performed, followed by optical and structural characterizations. Scanning electron microscopy analysis of the TiO2 reveals many nanotubular structures with particle sizes of ∼134.4, 148.8, and 132.7 nm at random locations. TiO2 is also found to have an absorbance range of 397.6 nm, from which it is known that the photocatalyst reacts in the presence of an ultraviolet source. From the Miller indices of the x-ray diffraction peaks, the preferred crystal orientation is found to be associated with a face-centered cubic structure with a crystallite size of 3.76 nm. Using these promising results, photocatalytic analysis is performed, revealing good degradation characteristics. This investigation reveals that TiO2 substrates coated with Ag nanoparticles possess significant potential for application in the photocatalytic oxidation of methylene blue dye, which is a crucial step toward establishing a cleaner environment.
Improving the surface quality in die steel electrical discharge machining using liquid ultrasonic cavitation
Authors: Qi Li , Liu Yang , Song Mancang
Published: January 2025

Polymer microfluidic chips are a common tool in biomedical research, and the production of mold inserts with microscale structures represents a crucial step in the precise molding of these chips. Electrical discharge machining (EDM) can achieve high-quality machining of microstructures on high-hardness mold steel inserts. This can reduce the manufacturing cost of microfluidic chip molds and extend the service life of molds. However, the EDM process is susceptible to the formation of poor-quality surfaces due to the occurrence of abnormal discharges. To address this issue, this paper presents in-depth research on a novel ultrasonic cavitation-assisted electrical discharge machining method. An ultrasonic transducer is placed in an electrical discharge working fluid to promote the removal of electrical corrosion products through the cavitation effect of the liquid. This can also reduce the occurrence of poor discharge, thereby improving the machining surface quality. The aluminum foil corrosion method is employed to investigate the distribution of ultrasonic action in the electric discharge working fluid. The attenuation law of ultrasonic action in the electric discharge working fluid is also investigated. The range of ultrasonic action is determined, providing a reference for subsequent ultrasonic vibration electric discharge working fluid processing experiments. The results of the aluminum foil tests are used to inform the selection of NAK80 mold steel as the experimental object. The effects of cavitation at three ultrasonic frequencies on the surface microstructure are investigated. The experimental results indicate that ultrasonic cavitation can facilitate the movement of corrosion products in electrical machining, reduce the occurrence of abnormal discharges caused by carbon deposition or the secondary re-melting of metals, and thereby enhance the machining surface quality.
Open-boundary molecular dynamics of ultrasound using supramolecular water models
Authors: Lah Maša , Ntarakas Nikolaos , Potisk Tilen , Papež Petra , Praprotnik Matej
Published: January 2025

Ultrasound can be used to manipulate protein function and activity, as well as for targeted drug delivery, making it a powerful diagnostic and therapeutic modality with wide applications in sonochemistry, nanotechnology, and engineering. However, a general particle-based approach to ultrasound modeling remains challenging due to the significant disparity between characteristic time scales governing ultrasound propagation. In this study, we use open-boundary molecular dynamics to simulate ultrasound waves in liquid water under ambient conditions by employing supramolecular water models, i.e., the Martini 3, dissipative particle dynamics, and many-body dissipative particle dynamics models. We demonstrate that our approach successfully reproduces the solution of the traveling wave equation and captures the velocity dispersion characteristic of high-frequency ultrasound waves.
Experimental discrimination of domain switching behaviors within interfacial and bulk layers in the LiNbO3 domain-wall memory
Authors: Zhang Wen Di , Jiang An Quan
Published: January 2025

Multilevel resistance states with respect to the volume of the reversed domains in ferroelectric tunneling junctions and erasable conducting domain walls in an insulating ferroelectric matrix enable high-speed and energy-efficient ferroelectric synapses, memories, and transistors. According to the domain nucleation model, the operation speeds of these devices are assumedly limited by domain nucleation time while the subsequent domain growth time is neglected. Unfortunately, these two times cannot be separated from the experiment yet. Here, we observed independent switching behaviors of domain nucleation and growth at two discrete coercive fields for a mesa-like memory cell formed at the surface of a LiNbO3 single crystal. After the application of an in-plane electric field to two side electrodes, we observed the on currents upon antiparallel domain reversals via the creation of conducting domain walls between them. Once the applied electric field is removed, the domains within the interfacial layers between the two side electrodes and the cell are volatile and switch back into their initial orientations automatically, unlike the nonvolatile bulk domain encoding digital information. In consideration of volatile and nonvolatile natures of the two domains, we separately observed their switching behaviors from the measurements of frequency-dependent domain switching hysteresis loops after programing various write and read pulses. It is found that all coercive fields with the involvement of domain nucleation at the interfaces are always frequency-dependent, unlike domain forward growth within the bulk layer that is frequency-independent. This provides the direct evidence that the operation speed of the low-dimensional ferroelectric device is limited by the domain nucleation rate at the interface.
Design and characterization of a novel plasma actuator with combined spanwise and vertical effects for turbulent skin-friction drag reduction
Authors: Liu Hongrui , Su Zhi , Liang Hua , Zong Haohua , Wei Biao , Fang Ziqi
Published: January 2025

A plasma actuator with adjustable jet direction based on the combination of dielectric barrier discharge (DBD) and corona discharge is proposed and characterized for turbulent drag reduction applications. The results show that an oblique jet and corresponding vortex series are formed through the interaction of the vertical jet by corona discharge and the horizontal jet by DBD. By changing the power input of DBD and corona discharge, both the velocity amplitude and the deflection angle of the oblique jet can be adjusted swiftly, and the maximum deflection angle of the coupled jet is 66.74°. The maximum velocity of the coupled jet reaches 1.77 m/s at a total power consumption of 23.09 W. Keeping the corona discharge parameters constant and increasing the DBD voltage, the relative distance of the vortex core decreases monotonically. There exists an optimal power ratio, making the total vortex intensity maximized. The actuator can provide combined spanwise and vertical control in a complex turbulent boundary layer to achieve better drag reduction.
Energy efficiency and air distribution characteristics of jet ventilation in crossflow for long-narrow mining working faces
Authors: Wang Jue , Jiang Cheng , Yang Guang , Meng Fankang , Kang Jiayu , Yu Shixuan , Bai Gang
Published: January 2025

Long-term exposure to extreme heat in mines jeopardizes worker health and reduces productivity. This study introduces and evaluates the air distribution of jet ventilation in crossflow (JVIC) mode for localized mine cooling. Experimental and numerical simulations reveal two distinct wake structures: single wakes for wall-attached and impinging jets, and double wakes for deflected jets, influenced by counter-rotating vortex pair (CVP) structures, which accelerate cooling loss. Key parameters—jet-to-crossflow velocity ratio (R), vent equivalent diameter-to-roadway height ratio (C), and jet-to-crossflow Reynolds number ratio—govern flow modes and CVP dynamics, while jet-to-crossflow temperature ratio (T) primarily affects cooling distribution within the jet, confirming a velocity-dominated flow field. A quantitative model was developed to characterize JVIC air distribution, detailing boundaries, diffusion widths, and velocity and temperature trajectories. The model demonstrates that wall-attached and highly deflected jets enable more stable cooling with slower diffusion and reduced energy loss. Under conditions of R = 1 and C = 3, the jet achieves the highest local cooling effectiveness (εt), maintaining a cooling efficiency of 29.9% at x/dm = 3, demonstrating JVIC's ability to maintain effective cooling over extended distances. A practical evaluation shows that the novel JVIC mode achieves a cooling load of 184.9 kW, reducing energy consumption by 86.7% compared to traditional full-air cooling (1387 kW). These findings highlight JVIC's potential for efficient, targeted mine ventilation, advancing cooling efficiency and energy conservation.
Morphological and mechanistic study of a continuous flash boiling liquid ammonia spray
Authors: Liu Jiawen , Zhang Meng , An Zhenhua , Chen Jian , Wang Jinhua , Tang Chenglong , Huang Zuohua
Published: January 2025

As a zero-carbon fuel with superior properties, ammonia has attracted much attention from the combustion industry in recent years. In ammonia combustion for gas turbines (GTs), direct combustion of liquid ammonia (LNH3) is considered a way to increase power, simplify the system, and reduce energy consumption. However, due to the low boiling point and high vaporization latent heat of ammonia, LNH3 is prone to flash boiling under GT conditions, leading to significant changes in its spray characteristics. The current understanding of such a special spray is still insufficient. In this paper, particle droplet image analysis, Mie scattering, and thermocouple temperature measurement were conducted for continuous flash LNH3 spray in normal pressure. Furthermore, large eddy simulation was carried out. The quantitative characterization and detailed study of its spray morphology, parameter distribution, mass transfer, and heat transfer process were investigated. Combining this with the evaporation process, the formation reason for its spray morphology was explained, and suggestions for optimizing the combustion organization of the flash boiling spray were given. The results show that the spray angle θ decreases rapidly from 86° to about 10°, the spray SMD is 16 μm and the diameter spatial distribution is uniform. The spray temperature is 238.1 K at the nozzle exit, which is lower than the boiling point (239.8 K), and subsequently drops to approximately 209 K downstream the spray. The bubble behavior inside the nozzle and the gas diffusion in the near field of spray led to the expansion of near-field spray, and further changed the nozzle characteristics. The spray can be divided into three regions: Spray-core-region, Spray-main-region, and Spray-edge. The extremely high concentration of gaseous ammonia in Spray-core-region significantly deteriorates evaporation. The difference of droplet velocity and evaporation ability between Spray-main-region and Spray-edge leads to the formation of “willow leaf” shaped spray.
Hydrodynamic performance of a novel dual floating protective device
Authors: Xie Canrong , Liu Xi , Wu Zhiwen , Hu Yichan , Peng Linxin , Yang Yi , Garg Ankit , Mei Guoxiong
Published: January 2025

Individual floating breakwaters have limited impact on wave dissipation, particularly concerning medium- and long-period waves. However, the incorporation of a dual floating breakwater significantly enhances wave dissipation performance. This study introduces a novel design—a dual floating protective device—aimed at enhancing both wave dissipation and current attenuation. The hydrodynamic behavior of this dual floating protective device is rigorously examined through experimental investigations conducted using a large wave–current flume. A comprehensive sensitivity analysis of key parameters, including relative draft, spacing between floats, and wave–current characteristics, is performed to explore their effects under regular and irregular wave conditions, as well as combined wave–current coupling action. Additionally, the appropriate application of particle image velocimetry is utilized, and a discussion of current field and water particle velocity vectors in front of, within, and behind the dual floating protective device is provided. The results indicate that the wave dissipation performance of the dual floating protective device can be enhanced by 125.4% under regular wave–current interactions. Notably, when the spacing of the dual floating protective device is adjusted to twice, once, or two-thirds of the wavelength, superior attenuation capabilities are observed. The current transmission coefficient of the dual floating protective device initially increases before decreasing as current velocity rises. Furthermore, under the influence of mid- to long-period waves, significant coupling and collision phenomena occur between the dual floating protective devices, endowing it with robust capabilities for attenuating such waves. This study provides valuable insights for future practical applications in the field of marine engineering.
Wall effects in fishes-like undulating hydrofoils
Authors: Dutta Soumitra , Lakkaraju Rajaram , Roy Somnath
Published: January 2025

Researchers have been inspired to study the mechanics of aquatic animals to develop advanced underwater vehicles and robots, as they demonstrate swimming abilities that are far superior to those of human-made propulsion devices. Autonomous underwater vehicles (AUVs) designed for military, scientific, and environmental applications often require efficient propulsion near boundaries, motivating the study of boundary effect in swimming organisms. This research investigates the hydrodynamic characteristics of wall effects in undulating hydrofoils, exploring variations in undulation wavelength (λ), Strouhal number (St), wall clearance (h/c), and Reynolds number (Re). Our current work aims to elucidate how these parameters influence lift coefficient, drag coefficient, power consumption, and swimming efficiency compared to the free-stream conditions. We have explained how the kinematics of the undulating hydrofoils affect the direction of forces over their different locations and result in variations of lift and drag with the kinematic parameters. We have also explored the interaction of vortices shed from the trailing edge and their influences on the flow characteristics in swimmers near boundaries. Comparative analyses with rigid pitching hydrofoils highlight distinct hydrodynamic behaviors in undulatory motion, emphasizing the importance of flexibility and kinematic adjustments near boundaries. The wall effect increases viscous drag across the parameters explored in this study. Pressure thrust is appreciably enhanced at higher values of (St) and (λ). However, while the amplitude of lift increases monotonically with the wall clearance ratio for all λ, the time-averaged lift departs from a monotonic trend with clearance at lower λ ranges. Swimming power consumption increases near boundaries, but swimming efficiency decreases with lower wall clearance in moderate Reynolds number scenarios.
Study on acoustic streaming characteristics around elliptical heat exchanger tubes at different angles of attack
Authors: Zhou Yu , Jiang Genshan , Sun Jianhao , Jiang Yu , Zhou Zishu , Li Hao
Published: January 2025

The distribution of acoustic streaming outside the tube in a planar standing wave field is calculated by numerical simulation using an elliptical heat exchanger tube at the low-temperature heating surface of a 600 MW unit as an example. The study discusses the impact of angle of attack (AOA), Strouhal number (St0), and Reynolds number (Re0) on the external acoustic streaming characteristics of the tube from structural, intensity, and scale perspectives. The results indicate that the strong nonlinearity of the second-order acoustic streaming in the Stokes boundary layer is driven by the first-order acoustic field. As the AOA increases, the external acoustic streaming vortices exhibit a phenomenon of inner and external vortex merging. Along the direction of the inner vortex center, the acoustic streaming velocity shows peak and valley fluctuations influenced by the vortices. In the normal direction, the acoustic streaming is significantly weakened, and the velocity distribution characteristics vary at different distances s. The inner vortices i = 1 and 2 achieve maximum and minimum values around AOA = 60° and 30°, respectively. The relative Nusselt number NU and relative shear rate SH quantify heat transfer and ash removal effects, respectively. Both small St0 and large Re0 enhance the heat transfer effectiveness. The SH shows a similar variation pattern to the scale of the acoustic streaming under the corresponding cases. The conclusion aligns well with the requirements of enhanced heat transfer and ash resistance for low-temperature heating surfaces, providing important reference for the selection of AOA for elliptical heat exchange tubes.
Machine learning accelerated nonadiabatic dynamics simulations of materials with excitonic effects
Authors: Wang Sheng-Rui , Fang Qiu , Liu Xiang-Yang , Fang Wei-Hai , Cui Ganglong
Published: January 2025

This study presents an efficient methodology for simulating nonadiabatic dynamics of complex materials with excitonic effects by integrating machine learning (ML) models with simplified Tamm–Dancoff approximation (sTDA) calculations. By leveraging ML models, we accurately predict ground-state wavefunctions using unconverged Kohn–Sham (KS) Hamiltonians. These ML-predicted KS Hamiltonians are then employed for sTDA-based excited-state calculations (sTDA/ML). The results demonstrate that excited-state energies, time-derivative nonadiabatic couplings, and absorption spectra from sTDA/ML calculations are accurate enough compared with those from conventional density functional theory based sTDA (sTDA/DFT) calculations. Furthermore, sTDA/ML-based nonadiabatic molecular dynamics simulations on two different materials systems, namely chloro-substituted silicon quantum dot and monolayer black phosphorus, achieve more than 100 times speedup than the conventional linear response time-dependent DFT simulations. This work highlights the potential of ML-accelerated nonadiabatic dynamics simulations for studying the complicated photoinduced dynamics of large materials systems, offering significant computational savings without compromising accuracy.
Aerodynamic characteristics and flow topology of tapered symmetrical airfoil equipped with Clark-Y shaped vortex generators
Authors: Seyhan Mehmet
Published: January 2025

The aerodynamic characteristics and surface flow topology of tapered swept-back National Advisory Committee for Aeronautics 0020 airfoil equipped with Clark-Y shaped vortex generators (CsVGs) are researched. The force and surface oil flow visualization for the tapered swept-back wing having a swept angle of 25° and a taper ratio of 0.4 is performed at a Reynolds number (Re) of 1.2×105 via CsVGs at x/c = 0.2, 0.3, 0.4, and 0.5. The airfoil equipped with CsVGs at x/c = 0.2 [T2 at an angle of attack (AoA) of 13°] showed a 15.53% improvement in the maximum CL and a delaying stall by 2° comparison with the baseline [at AoA of 11°]. According to oil flow visualization, the T2 model enhanced the post stall characteristics via CsVGs by increasing the attached flow region from the root to the tip as compared to the baseline. While the straight laminar separation bubble (LSB) for the baseline was observed, a wavy LSB for T2 occurred due to the interaction of LSB with CsVGs located at 0.2c. Primary attach flow regions on the downstream of each CsVG, attached flow regions on the downstream of CsVG pairs, and interaction line due to the interaction of primary and attached flow region were identified via oil flow visualization.
Solitary wave structure of transitional flow in the wake of a sphere
Authors: Niu Lin , Dou Hua-Shu , Zhou Changquan , Xu Wenqian
Published: January 2025

The soliton-like coherent structure (SCS), which has been verified to exist in both transitional and turbulent boundary layers [Y. S. Kachanov, “Physical mechanisms of laminar-boundary-layer transition,” Annu. Rev. Fluid Mech. 26, 411–482 (1994); C. Lee, “New features of CS solitons and the formation of vortices,” Phys. Lett. A 247, 397–402 (1998); C. Lee and J. Z. Wu, “Transition in wall-bounded flows,” Appl. Mech. Rev. 61, 030802 (2008); and C. Lee and X. Jiang, “Flow structures in transitional and turbulent boundary layers,” Phys. Fluids 31, 111301 (2019)], still poses a challenge in the understanding of its formation and behavior. In our previous study [Niu et al., “Turbulence generation in the transitional wake flow behind a sphere,” Phys. Fluids 36, 034127 (2024)], the SCS was also found to exist in the transitional wake flow behind a sphere. In the present study, the formation and evolution of the SCS is further investigated at various Reynolds numbers by numerical simulation. The results show that at the early stage of the turbulence transition, the SCS appears as a form of wave packet during the Tollmien–Schlichting (T–S) wave stage. With the increase in the Reynolds number, the SCS reaches its maximum amplitude downstream where the velocity discontinuity occurs. This position is located after the breakdown of the T–S wave and the three-dimensional structure is formed. Then, the SCS conserves its shape and amplitude over a long distance downstream. The relationships among the SCS, the spikes, the vortex structures, and the high-shear layers are further analyzed. It is found that the SCS in the wake flow has similarities to the phenomena observed in boundary layer flows during the turbulent transition. The vortex structures and high-shear layers mostly wrap around the border of the SCS. The vortex structure is considered to be a consequence of the development of the SCS rather than its cause.
Young people’s preferences and motivations for STI partner notification: observational findings from the 2024 Sex, Drugs and Rock ‘n’ Roll survey
Authors: Munari Stephanie C. , Goller Jane L. , Coombe Jacqueline , Orozco Ana , Eddy Sarah , Hocking Jane , Hellard Margaret , Lim Megan S. C.
Published: January 2025

Background Partner notification is an important step in the control of sexually transmissible infections (STIs). STIs remain at high rates among young people and can have serious reproductive consequences if left untreated. This study aimed to determine the preferences and motivations for partner notification among young people in Australia. Methods Quantitative and free-text qualitative data were collected through the 2024 Sex, Drugs and Rock ‘n’ Roll survey, an annual cross-sectional survey conducted among people aged 15–29 years old in Victoria, Australia. Respondents were recruited using convenience sampling through social media advertisements. Counts and proportions were calculated for the preferences and motivations for partner notification by regular and casual sexual partners as well as methods of communication. Inductive content analysis was used to analyse free-text responses. Results The partner notification module of the survey was completed by 1163 people (60.3% identified as women, 40.2% as heterosexual) who provided a total of 1720 free-text responses. The majority, 1056 (90.8%) stated that they would notify their sexual partners and 1142 (98.2%) would want to be notified by a sexual partner of an STI risk. Qualitative analysis highlighted that respondents felt that partner notification is the responsible thing to do to look after their own and their partner’s health and protect others by reducing transmission. Few stated that embarrassment and fear of repercussions may make them less likely to notify their partners or that it would depend on the type of relationship. Most preferred to notify regular partners face-to-face (941, 80.9%) and casual partners via text message (785, 67.5%). Conclusion Almost all young people want to notify and be notified by partners of an STI risk regardless of age, gender or sexual identity. Tailoring resources by communication method and partner type is one way in which practitioners and public health authorities can support young people in undertaking this important step in STI control.
Turbulence in the tropical stratosphere, equatorial Kelvin waves, and the quasi-biennial oscillation
Authors: Atlas Rachel , Podglajen Aurélien , Wilson Richard , Hertzog Albert , Plougonven Riwal
Published: January 2025

The tropical stratosphere is the gateway to the global stratosphere and a commonly proposed location for solar geoengineering. The dynamics of this remote and difficult to observe region are poorly understood, particularly at turbulent length scales. Existing observational estimates of turbulence frequency and strength vary widely. Furthermore, the sources of turbulence and the relationship between turbulence and the mean flow are largely unknown. We assembled a 21-y database of high vertical resolution (10 m) radiosonde data from four equatorial sites in two ocean basins to study tropical stratospheric turbulence frequency, variability, and sources. Turbulent layers thicker than 200 m are identified using subcritical Richardson number as a proxy for turbulence. We show that the turbulent fraction of the tropical stratosphere is strongly modulated by the quasi-biennial oscillation (QBO). Turbulence is enhanced during the QBO phase shifts, and the atmosphere is most turbulent right before the QBO phase switches from negative to positive, where turbulent instabilities typically occur within specific phases of Kelvin waves. Turbulence is less common when the QBO phase is well established, and the atmosphere is least turbulent during the negative phase of the QBO. The turbulent fraction of the equatorial lower stratosphere varies over a factor of ten depending on QBO phase. This relationship provides a robust observational constraint on the multiscale dynamics within this region, which is useful for evaluating atmospheric models, studying wave-mean flow interactions in the context of the QBO, and informing the operation of stratospheric aircraft and the injection of aerosol for geoengineering.
Measurements of Gravitational Attractions at small Accelerations
Authors: Bartel W , Elvers C W , Jönsson L , Kempf G , Krause H , Loehr B , Lohrmann E , Meyer H , Steffen P , Wuensch E
Published: January 2025

Gravitational interactions were studied by measuring the influence of small external field masses on a microwave resonator. It consisted of two spherical mirrors, which acted as independent pendulums individually suspended by strings. Two identical field masses were moved along the axis of the resonator symmetrically and periodically between a near and a far position. Their gravitational interaction altered the distance between the mirrors, changing the resonance frequency, which was measured and found consistent with Newton’s law of gravity. The acceleration of a single mirror caused by the two field masses at the closest position varied from

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Timing advanced receiver autonomous integrity monitoring augmented by BDSBAS
Authors: Xue Yu , Zheng Fu , Deng Liangcheng , Lin Yuanhui , Shi Chuang
Published: January 2025

Global navigation satellite system (GNSS) provides sufficiently accurate and affordable time and frequency information for timing and synchronization (T&S) equipment, which is widely used in modern infrastructures such as 5 G, small cells, and data centers. However, ensuring the integrity of GNSS timing service faces challenges due to the inherent vulnerability of GNSS signals and the complexity of user environments. Advanced receiver autonomous integrity monitoring (ARAIM) provides integrity monitoring of GNSS services at the user side, while BeiDou satellite-based augmentation systems (BDSBAS) improves GNSS service integrity from the service side by broadcasting corrections and integrity information. This study explores the potential of integrating ARAIM with dual-frequency multi-constellation (DFMC) BDSBAS for the integrity monitoring of GNSS timing services, as both technologies use DFMC signals and complement each other at different service levels. Several key improvements are made to the ARAIM algorithm, including risk allocation, solution estimation, and protection level (PL) calculation, to enable its application in the integrity monitoring of timing services. The improved algorithm, referred to as the timing ARAIM (T-ARAIM) algorithm, provides a quality control solution for high-precision timing applications. Furthermore, the T-ARAIM algorithm is enhanced by incorporating the correction and integrity parameters from DFMC BDSBAS messages, further improving the accuracy and reliability of timing services. The performance of the T-ARAIM algorithm augmented by BDSBAS is thoroughly validated and analyzed through simulation experiments, real-world experiments, and BDSBAS augmentation experiments. Simulation results indicate that when the receiver antenna position is estimated, the coverage of T-ARAIM (availability greater than 99.9%) using GPS + BDS-3 reaches 37.2%, with further improvement to 54.3% upon fixing the inter-satellite bias (ISB). In scenarios where the receiver antenna position is fixed, T-ARAIM coverage can achieve 100% even with a single constellation. Real-world experiments utilizing raw observations from seven globally distributed GNSS stations reveal that fixing the receiver antenna position reduces timing errors and time protection levels (TPL) by over 40%. Fixing the ISB does not affect the accuracy of the timing solution but slightly reduces TPL by about 2 ns. Fixing the receiver antenna position and/or ISB increases observation redundancy, significantly improving T-ARAIM availability. The integration of BDSBAS augmentation information further improves the timing solution, with timing accuracy increasing by approximately 4.4%–5.8% and T-ARAIM availability rising by about 11.7%–13.4% when the receiver antenna position is estimated. In fixed-position scenarios, the improvements in timing accuracy are more pronounced, approximately 20.0% to 28.5%, with T-ARAIM availability reaching 100%.
Fiber Bragg grating-based method for underwater object angular measurement
Authors: Li Hanyang , Song Yeshuai , Wang Jianwei , Dou Xinyu
Published: January 2025

In this paper, we present a underwater object angular measurement method that is composed of a novel fluid pressure sensor and a algorithm for angle measurement. The innovative pressure sensing structure, incorporating four fiber Bragg gratings, demonstrates remarkable sensitivity to fluid pressure, achieving a resolution of 1.3 pm μϵ
−1 . Based on this unique structure, we have developed an algorithm that utilize the characteristics of Bragg grating signal to determine the angular position of the vibration source. Through several different experiments, we evaluated the performance of pressure sensor and accuracy of angular algorithm. The results indicated that our algorithm achieves a mean absolute error of 2.3 degrees, coupled with a root mean square error of 3.1 degrees, demonstrating its high precision in determining the angular position of the vibration source. Furthermore, the practicality and robustness of this method has been validated in complex flow fields, demonstrating its promising application in underwater environment monitoring.
A non-isothermal phase-field crystal model with lattice expansion: analysis and benchmarks
Authors: Punke Maik , Salvalaglio Marco , Voigt Axel , Wise Steven M
Published: January 2025

We introduce a non-isothermal phase-field crystal model including heat flux and thermal expansion of the crystal lattice. The fundamental thermodynamic relation between internal energy and entropy, as well as entropy production, is derived analytically and further verified by numerical benchmark simulations. Furthermore, we examine how the different model parameters control density and temperature evolution during dendritic solidification through extensive parameter studies. Finally, we extend our framework to the modeling of open systems considering external mass and heat fluxes. This work sets the ground for a comprehensive mesoscale model of non-isothermal solidification including thermal expansion within an entropy-producing framework, and provides a benchmark for further meso- to macroscopic modeling of solidification.
Asymmetric hysteresis characteristics of magnetorheological elastomer embedding the tilt chain-like structure on the translational shear test: experiment and modeling
Authors: Lin Dezhao , Gong Di , Yang Fan , Li Ruihong , Zhang Weiqiang
Published: January 2025

The magnetorheological elastomer (MRE) with tilt chain-like structure can significantly enhance the magnetorheological effect, but its hysteresis nonlinearity in the stress–strain responses is still unclear, especially the effect of the chain-like structure angle, which is essential for effective designs of controllable MRE-based devices. In this study, the hysteresis characteristics of the tilt chain-like structure MRE in the stress–strain curve of the translational shear test are investigated through the experiment and modeling. The experimental results of shear testing indicated that the stress–strain relationships of MRE with the tilt chain-like structure show an asymmetric hysteresis loop together with an obvious offset, which is different from the isotropic MRE and anisotropic MRE with the symmetric chain-like structure. In order to describe the asymmetric hysteresis loop in the translational shear characteristic, a stop operator-based modified Prandtl–Ishlinskii (PI) model is established considering a hyperbolic-tangent envelope function. The comparisons between model-predicted and measured data demonstrate that the established modified PI model can accurately describe the asymmetric hysteresis loops of MRE with different chain-like structure angles for wide ranges of excitation conditions and magnetic fields.
Quantum Field Theory of black hole perturbations with backreaction. Part III. Spherically symmetric 2nd order Maxwell sector
Authors: Neuser J. , Thiemann T.
Published: January 2025

In this paper we extend reduced phase space approach to black hole perturbation theory to
Maxwell matter. We expand the resulting reduced Hamiltonian to second order in the graviton and
photon perturbations and find that the corresponding equations of motion match the ones derived in
the literature. Accordingly our approach reproduces previous results at second order. Its real
virtue lies in the fact that it extends to any order in perturbation theory in a manifestly gauge
invariant fashion, includes backreaction effects and covers the black hole interior due to
working in the regular Painlevé Gullstrand gauge.
Cosmological constraints on anisotropic Thurston geometries
Authors: Smith Ananda F. , Copi Craig J. , Starkman Glenn D.
Published: January 2025

Much of modern cosmology relies on the Cosmological Principle, the assumption that the Universe is isotropic and homogeneous on sufficiently large scales, but it remains worthwhile to examine cosmological models that violate this principle slightly.
We examine a class of such spacetimes that maintain homogeneity but break isotropy through their underlying local spatial geometries.
These spacetimes are endowed with one of five anisotropic model geometries of Thurston's geometrization theorem, and their evolution is sourced with perfect fluid dust and cosmological constant.
We show that the background evolution of these spacetimes induces fluctuations in the observed cosmic microwave background (CMB) temperature with amplitudes coupled to the curvature parameter Ω
K
.
In order for these fluctuations to be compatible with the observed CMB angular power spectrum, we find |Ω
K
| ≲ 10-5.
This strongly limits the cosmological consequences of these models.
In situ swelling of low-friction, high load-bearing self-bending bilayer hydrogels inspired by articular cartilage
Authors: Chen Jianfeng , Li Chuan , Chen Xiaoxiao , Zhou Kui , Li Hanjing , Peng Kai , Yang Yinong , Dai Yichuan , Huang Ben
Published: January 2025

The articular cartilage is characterized by its gradient hierarchical structure, which exhibits excellent lubrication and robust load-bearing properties. However, its inherent difficulty in self-repair after damage presents numerous formidable challenges for cartilage repair. Inspired by the unique structure of articular cartilage, a biomimetic bilayer hydrogel composed of PAM (polyacrylamide) and PAM/SA (sodium alginate) is prepared using a two-step in-situ swelling method. The bilayer hydrogel demonstrates exceptional structural stability due to the interlayer in-situ chemical cross-linking. Compared to monolayer hydrogels, the PAM-PAM/SA bilayer hydrogel demonstrates superior mechanical attributes, exhibiting a compressive strength of 1 MPa and a compressive modulus of 0.22 MPa. Furthermore, exploration of the tribological performance of the PAM-PAM/SA bilayer hydrogel have revealed its low-friction performance under high loads, with a coefficient of friction as low as 0.032. Finally, leveraging the differential swelling properties between the distinct layers of the PAM-PAM/SA bilayer hydrogel, a self-bending biomimetic cartilage capable of conforming to complex joint surfaces is fabricated. This highly lubricating, mechanically robust, and conformal biomimetic cartilage provides an effective means for addressing cartilage defects and joint diseases.
An ecofriendly approach to explore the physical and mechanical properties of cement mortar reinforced with Abutilon indicum fibres
Authors: Aarthipriya V , Umarani C
Published: January 2025

Cement composites are inherently characterized by low tensile strength and limited fracture resistance. The fibres have the potential of improving the tensile properties and lessen cracking. In recent years, a substantial increase in the utilization of plant-based fibres over synthetic fibres was observed primarily because of their abundant availability, which is also found to enhance the mechanical characteristics of cement composites. This study aims to examine the performance of Abutilon indicum fibre reinforced cement mortar with varied fibre contents and fibre lengths based on physical, mechanical and microstructural properties. Three different fibre lengths, 5, 10 and 15 mm and varying fibre contents of 0.5, 1.0, 1.5 and 2.0 wt% were considered. Experimental tests were carried out to find the physical and mechanical properties and the results revealed that the flexural and tensile strengths of mortar mixes were significantly improved by the addition of fibres with increased fibre lengths and contents. Conversely, the cement mortar experienced significant decrease in compressive strength as the dosage and length of fibres increased, attributed to a decrease in density, as well as the agglomeration and clustering of fibres within the mortar mixture. Multicriterial decision making method was employed to optimize and evaluate the overall technical performance of the fibre reinforced cement mortar. The mortar reinforced with 5 mm fibre length and 1% fibre addition was found to be potentially beneficial and considered as an optimum mix with respect to all mechanical properties. Microstructural analysis on the optimum mix revealed the existence of proper and sufficient interfacial bonding between the fibres and cement matrix and therefore it is recommended to use Abutilon indicum fibre in cement mortar for repair and other construction applications and the optimum mix proportion is reported.
Distributing quantum correlations through local operations and classical resources
Authors: Hawkins Adam G , McAleese Hannah , Paternostro Mauro
Published: January 2025

Distributing quantum correlations to each node of a network is a key aspect of quantum networking. Here, we present a robust, physically motivated protocol by which global quantum correlations, as characterized by the discord, can be distributed to quantum memories using a mixed state of information carriers which possesses only classical correlations. In addition, such distribution is done using only bilocal unitary operations and projective measurements, with the degree of discord being measurement-outcome independent. We explore the scaling of the performance of the proposed protocol with the size of the network and illustrate the structure of quantum correlations that are shared by the nodes, showing its dependence on the local operations performed. Finally, we find the counterintuitive result that even more discord can be generated when the resource state undergoes correlated dephasing noise, allowing high fidelities with mixtures of the Bell basis such as Werner states.
4D printing of direct-driven deformable wheel with multiple programmable configurations
Authors: Tian Huichun , Chu Guanghao , Zhou Bin , Zhou Dekai , Qiao Jing , Li Longqiu
Published: January 2025

Conventional deformable wheel systems in robots and other mechatronic systems face significant challenges in achieving miniaturization, intelligence, and integration. To address these issues, we propose a novel integrated structural design method and four-dimensional printing strategy for deformable wheels capable of shaping among multiple programmable direct-driven deformation configurations. The load-bearing capacity of the printed wheel is strengthened by employing deformed components in various locations and actuated states. Additionally, a novel analytical design method is presented to determine the structure, actuation, and deformation parameters of each component under complex coupled deformation. Our findings reveal that the designed wheel can transform into three different configurations, exhibiting desired deformations of 12.5% in the radial direction and 19.6% in the axial direction. It also demonstrates robust deformation behavior and structural stability under multi-directional loads. By integrating a terrain sensing system, the designed wheel exhibits highly adaptive deformation capabilities on various terrains, showing great potential for exploring complex environments.