Critical Current Research Articles

Probing Abrikosov vortices in niobium with single nitrogen-vacancy centers in nanodiamonds

Abrikosov vortices play a fundamental role in the magnetic and electric properties of superconductors. The study of their pinning forces is essential to better understand the stability of vortex lattices, with the aim of increasing critical currents in superconductors. However, the study of vortices is challenging because of their nanometric sizes and the large variation in the pinning forces. In this Letter, we use a single nitrogen-vacancy center in a nanodiamond as a nanoscale magneto sensor to locally probe single vortices and their pinning effects in a thin niobium film. This simple, far-field optical approach also offers the possibility of manipulating a single spin with a single flux quantum.

Two-Stream Modality-Based Deep Learning Approach for Enhanced Two-Person Human Interaction Recognition in Videos.

Human interaction recognition (HIR) between two people in videos is a critical field in computer vision and pattern recognition, aimed at identifying and understanding human interaction and actions for applications such as healthcare, surveillance, and human-computer interaction. Despite its significance, video-based HIR faces challenges in achieving satisfactory performance due to the complexity of human actions, variations in motion, different viewpoints, and environmental factors. In the study, we proposed a two-stream deep learning-based HIR system to address these challenges and improve the accuracy and reliability of HIR systems. In the process, two streams extract hierarchical features based on the skeleton and RGB information, respectively. In the first stream, we utilised YOLOv8-Pose for human pose extraction, then extracted features with three stacked LSM modules and enhanced them with a dense layer that is considered the final feature of the first stream. In the second stream, we utilised SAM on the input videos, and after filtering the Segment Anything Model (SAM) feature, we employed integrated LSTM and GRU to extract the long-range dependency feature and then enhanced them with a dense layer that was considered the final feature for the second stream module. Here, SAM was utilised for segmented mesh generation, and ImageNet was used for feature extraction from images or meshes, focusing on extracting relevant features from sequential image data. Moreover, we newly created a custom filter function to enhance computational efficiency and eliminate irrelevant keypoints and mesh components from the dataset. We concatenated the two stream features and produced the final feature that fed into the classification module. The extensive experiment with the two benchmark datasets of the proposed model achieved 96.56% and 96.16% accuracy, respectively. The high-performance accuracy of the proposed model proved its superiority.

Critical current degradation of commercial REBCO coated conductors under thermomechanical loads

Abstract The process to obtain a superconducting joint between Coated Conductors (CCs) involves the simultaneous application of temperature and transverse compressive pressure to promote the joining of the two adjacent REBCO layers. We performed experiments to simulate this procedure by subjecting samples from commercial CCs to different combinations of pressure, and temperature. The objective was to understand the effects of the thermomechanical cycles on the critical current (Ic) and, therefore, determine the upper limit for the achievable current in a superconducting joint between CCs. We observed a reduction of the Ic across the investigated parameter range that is accelerated at higher temperatures and pressures. For instance, the average reduction of Ic measured at 77 K in self-field varied from 45% to 90% when increasing the pressure for samples heated at 820 °C, as compared to samples heated at the same temperature without applied pressure. As a complement to electrical transport measurements, we carried out TEM and EDX investigations to study the relation between the degradation of Ic and alterations in the microstructure of REBCO. These analyses indicate that the concurrent application of temperature and pressure accelerates the decomposition of the REBCO phase. The EDX data suggests that the decomposition products could correspond with a peritectic reaction of the REBCO occurring at lower temperatures, accelerated by the presence of an external pressure. This early decomposition occurs in localized areas of the REBCO layer, constricting the available cross-section for current flow and thereby diminishing the critical current.

Effect of different core diameters on the current-carrying performance of CORC cables with REBCO multi-filamentary tapes

The second generation of high temperature superconductivity (HTS) is one of the candidate materials for future superconducting cables (such as CORC), CICC conductors and high field magnets due to its high current carrying performance and excellent mechanical strength. Currently, it has been demonstrated that the utilization of REBCO multi-filamentary tapes in the fabrication of CORC cables can further reduce AC losses. This study involved the preparation of various types of REBCO multi-filamentary tapes through reel-to-reel ultraviolet picosecond laser cutting technology, as well as the manual winding of multiple single-layer CORC cable samples. This work focused on the impact of core diameter on the current-carrying performance of REBCO multi-filamentary tapes under self-field conditions at 77 K. The results indicate that the critical current (IC) of REBCO multi-filamentary tapes decreases as the core diameter decreases. Furthermore, the decrease in IC becomes more significant with an increasing number of cores. When the cable core diameter is 4.6 mm, the critical current of the 3-filament tape is 180.49 A with an n-value of 24.84, which is only a 3.1 % recession compared to the critical current of the commercialized tape. The conclusion of this paper will provide a certain data reference for the subsequent selection of CORC cable core size prepared by REBCO multi-filamentary tapes.

Bibliometric Analysis of Studies on Delirium in Critical Care

Background Delirium leads to prolongation in intensive care unit (ICU) and hospital length of stay and an increase in ICU costs and mortality. As a result of this, the number of studies on delirium in ICUs has recently increased significantly, and many articles have been published. Objectives The aim of this study was to evaluate the articles related to “delirium” in “critical care” field in the Web of Science database and the first hundred most cited articles on this subject. Methods The Web of Science database was searched for articles relevant to “delirium” in the critical care medicine field published between 1980 and 2024. Text analytics and network models used in bibliometric mapping were used for prolific authors, annual trend, citation, and countries. Results In our study, it was determined that a total of 1834 articles in the field of delirium in critical care medicine were included. It was determined that the annual citation average was 42.79 and the H-index value was 134. There is a general upward trend over the years, and it was observed that it has intensified in the last 5 to 6 years. With the Reference Spectroscopy analysis, it was determined that the most intensively cited studies on delirium were the studies of 2013 and 2010. The distribution of keywords in recent years has focused on analgosedation, acute brain injury, older patient, COVID-19, and fragility. When examined for the top 100 cited articles, it was seen that mobilization, guidelines, pain, activities of daily living, anesthesia, sedation, and haloperidol have become prominent in recent years. Conclusion In recent years, there has been a noticeable increase in the volume of research focusing on delirium studies within the field of critical care medicine. Staying current with trends, incorporating findings from frequently cited studies, and customizing interventions to suit modern difficulties can all improve the quality of care offered to critically ill patients and lead to better outcomes.

Growing Need for Web-Based Simulation in Low and Middle-Income Countries: A Narrative Review

Web-based simulation programs are poised to offer a productive means of delivering asynchronous training in healthcare professionals’ education. Similarly, web-based simulation programs could also sponsor specialty-specific, web-based fellowships for clinicians of low- and middle-income countries. Web-Based Simulation has been utilized for instruction in critical care fields such as emergency medicine and pediatric anesthesia. Studies have shown that enhanced self-reported knowledge and confidence have been achieved through tele simulation which is in line with in-person simulation. During the COVID-19 pandemic, simulations have helped clinicians hone their use of personal protective equipment and other infection control measures. Additionally, it has helped them in learning new and expanded roles, like processing equipment and assisting infected patients in prone position experiencing respiratory failure. However, web-based simulation programs also have unique challenges that must be satisfied: reliable broadband internet network access, multilingual capability, and programming quality. Studies indicate that cost-effective simulation training can be delivered to learners in remote, low-resource areas worldwide, including South Asia, where access to such education is limited. We aimed to explore the effectiveness, challenges, and strategies for implementing web-based simulation education in low- and middle-income countries, based on a thorough PubMed search focused on web-based simulation programs in medical education.

Iron-Based Superconductors for High-Field Applications: Realization of High Engineering Critical Current Density.

Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (Je) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba0.6K0.4Fe2As2 (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport Je were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport Je of 4.1 × 104 A/cm2 (Ic = 350 A) at 4.2 K, 10 T, marking the highest Je reported for Ba-122 wires and tapes to date. Our results show that high transport Je can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications.

Josephson Critical Currents and Related Effects in Ultracold Atomic Superfluid Sytems

The Josephson and Proximity effects play a pivotal role in the design of superconducting devices for the implementation of quantum technology, ranging from the standard Al based to the more exotic twisted high-Tc junctions. Josephson critical currents have been recently investigated also in ultracold atomic systems where a potential barrier acts as a weak link. The unifying feature of the above systems, apart from being superconducting/superfluid, is the presence of spatial inhomogeneity, a feature that has to be properly taken into account in any theoretical approach employed to investigate them. In this work, we review the novel (dubbed LPDA for Local Phase Density Approximation) approach based on a coarse graining of the Bogoliubov–de Gennes (BdG) equations. Non-local and local forms of this coarse graining were utilized when investigating Proximity and Josephson effects. Moreover, the LPDA approach was further developed to include pairing fluctuations at the level of the non-self-consistent t-matrix approximation. The resulting approach, dubbed mLPDA (modified LPDA), can be used whenever inhomegeneity and fluctuations effects simultaneously play an important role.

Microwave Kinetic Inductance Detector Made of Molecular Beam Epitaxy (MBE)-Grown MgB2 Film.

We present a MgB2-based Microwave Kinetic Inductance Detector (MKID) featuring a quality factor Qi ~ 105 and noise equivalent power NEP ~ 10-14 W/Hz at 2 K. In comparison to YBCO-based MKIDs, the MgB2 detector shows greater sensitivity to both temperature and magnetic field, a result of its two-gap nature and relatively low critical Hc2 field. Our data indicate that MgB2 is more advantageous for MKID applications at temperatures lower than 3 K.

Double-pancake superconducting coil integrated with DFIG-based wind power systems under voltage-dip events: Design and performance analysis study

The doubly fed induction generator (DFIG)-based wind turbine provides massive development in power generation. Uncertain power oscillations and voltage-dip events affect the stability of the DFIG. To mitigate the effect of voltage-dips in short period, superconducting magnetic energy storage (SMES), which possess rapid energy exchange and high power density, is integrated with large-scale renewable power systems. SMES is integrated at the DC link of the DFIG to ensure the power balance and fault ride-through (FRT) capability. During this operation, frequent current changes occur in the high-temperature superconducting (HTS) coil, which leads to an increase in AC losses. As a remedy, an additional power converter structure controlled with a model-predictive controller (MPC) is proposed. Firstly, a scale-down HTS double-pancake coil model is designed using a finite element model by which transport current loss and magnetic field formulation are studied. Additionally, the critical coil current is also verified through experimental studies. The effectiveness of the proposed MPC-based SMES integrated DFIG on DC link voltage and grid current under IEC-61000-4-11 standard, symmetrical and asymmetrical voltage-dip cases are investigated. The obtained results demonstrate that the proposed system effectively reduces transients in DC link voltage and improves the FRT capabilities of the grid.

The Meissner effect in neutron stars

Abstract We present the first model aimed at understanding how the Meissner effect in a young neutron star affects its macroscopic magnetic field. In this model, field expulsion occurs on a dynamical timescale, and is realised through two processes that occur at the onset of superconductivity: fluid motions causing the dragging of field lines, followed by magnetic reconnection. Focussing on magnetic fields weaker than the superconducting critical field, we show that complete Meissner expulsion is but one of four possible generic scenarios for the magnetic-field geometry, and can never expel magnetic flux from the centre of the star. Reconnection causes the release of up to ∼5 × 1046 erg of energy at the onset of superconductivity, and is only possible for certain favourable early-phase dynamics and for pre-condensation fields 1012 G ≲ B ≲ 5 × 1014 G. Fields weaker or stronger than this are predicted to thread the whole star.

Non-equilibrium plasma distribution in the wake of a slender blunted-nose cone in hypersonic flight and its effect on the radar cross section

This paper presents numerical results in hypersonic aerothermodynamics, a critical field within aerospace engineering, traditionally focusing on reentry capsules and more recently, slender hypersonic vehicles. While capsules typically undergo near-field analysis to assess heat flux and pressure distributions for Thermal Protection System sizing, slender bodies demand additional attention to wake dynamics due to plasma presence. Plasma can significantly affect the Radar Cross Section (RCS) of these vehicles, which require tracking during flight due to their maneuvering and sustained flight capability.Utilizing Computational Fluid Dynamics tools, we explore plasma distribution around a slender blunted cone, considering altitudes and Mach number regimes that may characterize gliding or sustained atmospheric hypersonic flight, emphasizing its impact on RCS. Our study integrates an aerothermodynamic model incorporating non-equilibrium relaxation equations for gas composition and energy. By evaluating characteristic plasma quantities, we underscore the importance of wake plasma for subsequent electromagnetic wave analysis, crucial for understanding RCS. Furthermore, we highlight the necessity for collaborative efforts between Computational Fluid Dynamics (CFD) and Computational Electro-Magnetics (CEM) disciplines to address this challenging interdisciplinary problem.

Giant enhancement and quick stabilization of capacitance in antiferroelectrics by phase transition engineering

The antiferroelectric-ferroelectric phase transition is a basic principle that holds promise for antiferroelectric ceramics in high capacitance density nonlinear capacitors. So far, the property optimization based on antiferroelectric-ferroelectric transition is solely undertaken by chemical composition tailoring. Alternately, here we propose a phase transition engineering tactic by applying pulsed electric stimulus near the critical electric field, which finally results in ~54.3% enhancement and quick stabilization of capacitance density in Pb0.97La0.02(Zr0.35Sn0.55Ti0.10)O3 antiferroelectric ceramics. Ex-situ and in-situ structural characterizations show that electric stimuli can induce the charming successive structural evolution, including domain evolution from multidomain to monodomain state, and modulation period change from 7.49 to 7.73. Structure-property correlation indicates that the antiferroelectric-ferroelectric phase transition engineering mainly stems from the unexpected irreversible recovery of the modulated structures. The present findings would deepen the understanding of the structural phase transition and provoke composition-independent post-treatment property innovation in the incommensurate antiferroelectric materials and devices.

Long-range phase coherence and tunable second order φ0-Josephson effect in a Dirac semimetal 1T-PtTe2

Superconducting diode effects have recently attracted much attention for their potential applications in superconducting logic circuits. Several pathways have been proposed to give rise to non-reciprocal critical currents in various superconductors and Josephson junctions. In this work, we establish the presence of a large Josephson diode effect in a type-II Dirac semimetal 1T-PtTe2 facilitated by its helical spin-momentum locking and distinguish it from extrinsic geometric effects. The magnitude of the Josephson diode effect is shown to be directly correlated to the large second-harmonic component of the supercurrent. We denote such junctions, where the relative phase between the two harmonics can be tuned by a magnetic field, as ‘tunable second order φ0-junctions’. The direct correspondence between the second harmonic supercurrents and the diode effect in 1T-PtTe2 junctions at relatively low magnetic fields makes it an ideal platform to study the Josephson diode effect and Cooper quartet transport in Josephson junctions.

Spin-orbit proximity in MoS2/bilayer graphene heterostructures

Van der Waals heterostructures provide a versatile platform for tailoring electronic properties through the integration of two-dimensional materials. Among these combinations, the interaction between bilayer graphene and transition metal dichalcogenides (TMDs) stands out due to its potential for inducing spin–orbit coupling (SOC) in graphene. Future devices concepts require the understanding of the precise nature of SOC in TMD/bilayer graphene heterostructures and its influence on electronic transport phenomena. Here, we experimentally confirm the presence of two distinct types of SOC – Ising (ΔI = 1.55 meV) and Rashba (ΔR = 2.5 meV) – in bilayer graphene when interfaced with molybdenum disulfide. Furthermore, we reveal a non-monotonic trend in conductivity with respect to the electric displacement field at charge neutrality. This phenomenon is ascribed to the existence of single-particle gaps induced by the Ising SOC, which can be closed by a critical displacement field. Our findings also unveil sharp peaks in the magnetoconductivity around the critical displacement field, challenging existing theoretical models.

An Investigation into the Utilisation of CNN with LSTM for Video Deepfake Detection

Video deepfake detection has emerged as a critical field within the broader domain of digital technologies driven by the rapid proliferation of AI-generated media and the increasing threat of its misuse for deception and misinformation. The integration of Convolutional Neural Network (CNN) with Long Short-Term Memory (LSTM) has proven to be a promising approach for improving video deepfake detection, achieving near-perfect accuracy. CNNs enable the effective extraction of spatial features from video frames, such as facial textures and lighting, while LSTM analyses temporal patterns, detecting inconsistencies over time. This hybrid model enhances the ability to detect deepfakes by combining spatial and temporal analysis. However, the existing research lacks systematic evaluations that comprehensively assess their effectiveness and optimal configurations. Therefore, this paper provides a comprehensive review of video deepfake detection techniques utilising hybrid CNN-LSTM models. It systematically investigates state-of-the-art techniques, highlighting common feature extraction approaches and widely used datasets for training and testing. This paper also evaluates model performance across different datasets, identifies key factors influencing detection accuracy, and explores how CNN-LSTM models can be optimised. It also compares CNN-LSTM models with non-LSTM approaches, addresses implementation challenges, and proposes solutions for them. Lastly, open issues and future research directions of video deepfake detection using CNN-LSTM will be discussed. This paper provides valuable insights for researchers and cyber security professionals by reviewing CNN-LSTM models for video deepfake detection contributing to the advancement of robust and effective deepfake detection systems.

Hurricanes, reconstruction, and resistance: thinking through vulnerability in the Caribbean.

This paper critically analyses events that surrounded the reconstruction of the Colombian archipelago of San Andrés, Providencia, and Santa Catalina islands after Hurricane Iota struck in 2020. Discussing the historical-structural and conjunctural dimensions within which the archipelago's history, various hurricanes, and reconstructions must be set, this paper draws on two theoretical conversations from Latin American and Caribbean critical thought and the critical humanitarian field that understand humanitarian governance as an 'arena of dispute'. Through mainly archival research of different sources, this paper assesses reconstruction and what it laid bare: structural vulnerability largely produced by the long lasting coloniality of power. In addition, it describes the active mediations and negotiations and the plethora of actions and repertoires in response to these centralised plans. Ultimately, we offer a vision whereby what is negotiated concerns not only the priorities and directions of the reconstruction, but also the design of a different future for the islands.

Impact ionization coefficients along 4H-SiC ⟨11-20⟩ in a wide temperature range

Abstract The impact ionization coefficients along 4H-SiC ⟨11-20⟩ were determined in a wide temperature range from 294 K to 473 K. 4H-SiC (11-20) p-n diodes were fabricated and photomultiplication measurements were conducted on two types of photodiodes to measure the multiplication factors of carriers. The extracted impact ionization coefficients of both electrons and holes along 4H-SiC ⟨11-20⟩ decreased at high temperatures, which can be ascribed to the enhanced phonon scattering. On the basis of the results above, the critical electric field along 4H-SiC ⟨11-20⟩ calculated from the obtained impact ionization coefficients increased with the temperature.

Performance evaluation of a racetrack high temperature superconductor winding in an HTS levitation platform

Abstract High temperature superconducting (HTS) is a key technology of next generation high-speed railway systems, which guarantees high current and highly efficient traction power supply. HTS devices can reduce system weight and thus improve loads of vehicles. On high-speed maglev trains, HTS windings wound by second-generation (2G) HTS tapes play an important role in suspension and traction. However, in complex ferromagnetic environments, the performances of windings are notably influenced by the varying magnetic fields. In this paper, a new maglev platform is designed and comprised of a winding of six racetrack HTS coils, an E shape iron core and a magnetic guide rail. The air core structure of the winding is modeled，tested and the electromagnetic characteristics are analyzed for three dimensional (3D) finite element analysis of the platform. An A formulation is used to calculate magnetic vectors A and infer magnetic flux densities and current densities for the structures. After the winding is installed on the iron core and the magnetic guide rail is suspended above the iron core, the air gap between the iron core and the rail is varied from 0 mm to 20 mm in models and experiments. The magnetic fields, critical currents and losses of the winding in cases of the air core and the iron core conditions are used for analysis. The comparison between the air core and the iron core conditions confirms the reliability of the proposed models. This study provides means for analysis of complex superconducting maglev systems.

The Evolution of Potable Water Security: A Temporal Analysis of Key Indices and Trends

Water security is a critical global issue that has gained increasing attention from researchers, policymakers, and practitioners over the past few decades. This paper presents a comprehensive overview of the evolution of potable water security indices from the 1980s to the 2020s, focusing on the key research themes, trends, and influential factors in the field. We conducted a comprehensive search of the relevant literature and examined the development of water security indices to provide insights into the current state of research and identify future research directions. This paper will explore the historical context, key indicators, sector-specific challenges, climate change implications, governance and policy considerations, technological advancements, community engagement efforts, and future directions for research in this critical field. Researchers and policymakers will find this review valuable as it offers insights into the existing knowledge and the areas that require further exploration to address global water security challenges.