Curve Evolution Research Articles

Regulating structural stability and photoelectrical properties of FAPbI3via formamidine cation orientation.

Organic cations play a significant role in the structural stability and photoelectrical properties of organic-inorganic hybrid perovskites. The orientation of organic cations impacts its interaction with inorganic octahedrons [PbI]6-, subsequently modifying the atomic structure and electronic and optical properties of perovskite materials. However, it is still challenging to regulate the stability of perovskites with different orientations. In this work, density functional theory calculations were performed to investigate the effects of the formamidine cation (FA+) located at the angles of 0°, 45°, 90° and 180° (relative to the normal of the crystal plane) along the typical crystal directions ([001], [010], [110] and [111]) on the structural stability and photoelectrical properties of formamidine lead iodide (FAPbI3). The results show that when FA+ is located at 45° along the [111] direction, FAPbI3 achieves the highest stability and excellent photoelectrical properties. The energy evolution curves display that the system with the orientation of [111] has the minimum energy value, signifying stronger stability than the other orientations. Especially, when FA+ is located at 45° along the [111] direction. it exhibits a stronger hydrogen bond between H and I atoms, shorter Pb-I bond length and smaller [PbI]6- octahedral tilt bond angle. The band gap in the [110] direction changes from direct to indirect while FAPbI3 with other FA+ orientations still maintains the direct band structure located at the high symmetric R point. Furthermore, FA+ orientation drives the redshift of FAPbI3 towards the long wavelength region in the [111] crystal direction, which enhances the light absorption coefficient. This work can offer guidance in employing molecular regulation technology for the development of stable perovskite solar cells.

ADVANCED AUTOMATIC SYSTEM FOR REMOTE CONTROL IN THE OIL AND GAS INDUSTRY

The purpose of this work is to design and implement a cascade control system of the level with the flow rate, with remote supervision, in an industrial type installation, located in the Laboratory of Measurement Techniques, Department of Automation, Computers and Electronics, within the Faculty of Mechanical and Electrical Engineering. The operating parameters of the installation are as follows: suction pressure: 0 – 2 bar; discharge pressure: 0 -10 bar; water flow: 0-30 m3/h; transported liquid: water. The automation system is structured on three hierarchical levels: level 1: the instrumentation mounted on the installation (transducers, signaling devices, etc.); level 2: includes the TGA System; level 3: constitutes the upper hierarchical level and includes the HMI (Human Machine Interface). The TGA system is a computerized system that ensures the monitoring, command and control functions of all the stand's component elements. It contains a programmable logic controller PLC 1214 – Siemens, which communicates via an Ethernet IP network with an operator interface and with the network of the Faculty of Mechanical and Electrical Engineering, which allows remote control of the installation. It also includes the protection system in case of failure, which involves stopping the rotating equipment, isolating the pipes by closing the control valve and alarming the operators. The HMI (Human Machine Interface) interface presents 3 options on the start page, from where the operator can select which application he wants to test: flow control loop application; level adjustment loop application; cascade adjustment loop application. The HMI equipment integrates SCADA functions, database update, evolution curves of analog quantities, sound and monitor alarm system, keyboard command, periodic records, event records, alarm records and technological schemes at the human-machine interface. The entire software is made in an open architecture, recommended by ISO norms. The PLC communicates in the network by adopting the protocol TCP/IP. An executable program used for the real-time application program was developed.

HNBR and NBR gasket rubbers for plate heat exchangers: Thermo‐oxidative aging and service lifetime prediction

AbstractAmong several available rubbers used in gaskets for plate heat exchangers, the selection of the appropriate material for each operation window is crucial. This work evaluated nitrile butadiene rubber (NBR) and hydrogenated butadiene rubber (HNBR) gaskets aged at high temperatures for up to 60 days. The properties assessed of compression set (CS), hardness, and cross‐link density demonstrated superior degradation rates for the NBR specimens. Fourier transform infrared analysis showed that the hydrogenation process predominantly affected CC double bonds. Compress stress relaxation highlighted the impact of aging on the counterforce of rubber over time. Furthermore, indentation modulus profile analysis showed heterogeneous degradation for both materials at 140°C for NBR and 170°C for HNBR. The end‐of‐life criteria of 79% CS for both materials were determined through sealing tests of the aged samples. The service lifetime prediction, using the time–temperature superposition and Arrhenius methods through the CS evolution curves, demonstrated a higher degradation resistance of HNBR gaskets, that have a superior service lifetime of at least 3.5 times at 80°C concerning those of NBR, proving a superior behavior for the hydrogenated elastomer. In addition, the evaluation of the lifetime prediction enables the verification of which rubber gasket is recommended for each operational condition in terms of material cost, service lifetime, and maintenance costs.

Comprehensive surface integrity evaluation during early stages of gear contact fatigue

The study aims to evaluate the microstructural sensitive aspects of contact fatigue crack initiation and its evolution during the gear lifetime. Tests were performed to evaluate different stages in the evolution curve of gear contact fatigue. The magnetic Barkhausen noise (MBN) technique was used to characterize variations in the magnetic response in gears during the incipient gear contact fatigue mechanisms initiation. For a complete comprehension of the surface degradation, residual stresses, microstructure, and microhardness were explored. A substantial increase in the MBN signal is identified before the fatigue failure occurs, indicating the occurrence of microstructural alterations that change the magnetic properties. The early stages of contact fatigue are accompanied by a surface softening in the near-surface region, up to approximately 40 µm depth. These phenomena were also followed by a less compressive residual stress region at 20 µm depth. A lower influence of microstrains on the diffractogram can be observed by the full width at half maximum parameter (FWHM), indicating a higher amount of dislocation annihilation during the appearance of the initial stages of the contact fatigue mechanism. The study concludes by proposing a comprehensive approach to understand the mechanisms behind the early stages of gear contact fatigue and how the MBN signal can be used to detect fatigue damage.

Evolution of the South China Sea geo-pattern based on the “geo-potential-strategic triangle” framework

The South China Sea region is one of the most important international geopolitical problem regions. Against the background of international power transfer and China's peaceful rise, the changes in the South China Sea geo-pattern based on the power game not only concern China's national territorial sovereignty and maritime rights and interests, but also profoundly affect the security order of the Asia-Pacific region and even the world. In order to better study the evolution of the South China Sea geo-pattern and to judge the overall security situation, this study constructs a “geo-potential-strategic triangle” analytical framework to explore the evolution of the South China Sea geo-pattern from 2000 to 2018. The study shows that: (1) the geo-potential of each geo-actor shows a generally increasing trend. Based on the evolution curve of the South China Sea geo-pattern obtained from the geo-potential comparison, the South China Sea geo-pattern during the study period can be divided into the overall stabilization stage (2000–2010) and the tense phase(2010–2018). (2) through the mutual corroboration analysis of the evolution curve of the South China Sea geo-pattern and the interaction facts of related geo-actors, the assessment results coincide with the development of the security situation in the South China Sea region. This validates the applicability of the analytical framework in the geo-strategic intersection areas. The study aims to provide a new way of thinking for the quantitative assessment and analysis of the geo-pattern in the South China Sea region and other geo-strategic intersection areas. The study can help to objectively depict the evolution of the South China Sea geo-pattern, grasp the security situation in the South China Sea, and provide decision-making aids for sustainable peace and security, and differences management among the nations in the South China Sea region. This will further promote the construction of the regional ocean governance system and the construction of a closer “maritime community with a shared future”.

A shock flash breaking out of a dusty red supergiant.

Shock-breakout emission is light that arises when a shockwave, generated by the core-collapse explosion of a massive star, passes through its outer envelope. Hitherto, the earliest detection of such a signal was at several hours after the explosion1, although a few others had been reported2-7. The temporal evolution of early light curves should provide insights into the shock propagation, including explosion asymmetry and environment in the vicinity, but this has been hampered by the lack of multiwavelength observations. Here we report the instant multiband observations of a type II supernova (SN 2023ixf) in the galaxy M101 (at a distance of 6.85 ± 0.15 Mpc; ref. 8), beginning at about 1.4 h after the explosion. The exploding star was a red supergiant with a radius of about 440 solar radii. The light curves evolved rapidly, on timescales of 1-2 h, and appeared unusually fainter and redder than predicted by the models9-11 within the first few hours, which we attribute to an optically thick dust shell before it was disrupted by the shockwave. We infer that the breakout and perhaps the distribution of the surrounding dust were not spherically symmetric.

Essential stressing state characteristics of H-section steel beams in fire revealed by modeling tested response data

This study finds out the essential behavior features of H-section steel beams in fire by analyzing the response data applying structural stressing state theory. Firstly, the deformation data are transformed into the generalized work of force (GWF) values called the state variables. Then, the state variables are used to build the stressing state mode and the parameter characterizing the mode called the stressing state characteristic pair. Next, the characteristic points in the evolution curve of the characteristic parameter are distinguished by the Mann-Kendall criterion. Further, the investigation into the evolution curve of the stressing state mode verifies the characteristic points. Thus, the starting points of the beams’ failure processes are revealed from the tested data and the corresponding loads are defined as the failure loads. Also, the other characteristic point called the elastoplastic branch (EPB) point is revealed from the evolution curves of the stressing state characteristic pair. Both characteristic points are the embodiment of the natural law from quantitative change to qualitative change of any system, which provides the new reference to update the analysis and design of H-section steel beams in fire. Finally, the formulas are fitted to calculate the failure loads and the EPB loads of the beams in fire with a verification.

Thermal process of a silicon wafer under a CW laser and 100–10000 Hz pulsed laser irradiation

The thermal process of a (001) silicon wafer subjected to a continuous-wave (CW) laser and 100–10000 Hz pulsed laser irradiation is investigated experimentally and numerically. The temperature evolution of the spot center is measured using an infrared radiation pyrometer. The waveforms of the temperature evolution curves provide valuable information about melting, solidification, vaporization, and fracture. To gain a better understanding of the thermal process, a three-dimensional finite element model is established, and numerical simulations are conducted to analyze the temperature, stress, and dislocation field. The results show that the 10 kHz laser exhibits the highest heating efficiency before vaporization, but the lowest ablation efficiency after vaporization due to the shielding effect of vapor. The diffusion time of vapor is found to be more than 50 µs. Fracture occurs during 1 kHz laser irradiation. The motion of liquid may play a significant role, but it cannot be evidenced by a simulation due to complex dependence of material parameters on dislocation. This issue should be addressed as a priority in future studies.

ICFormer: A Deep Learning model for informed lithium-ion battery diagnosis and early knee detection

Accurate diagnosis of lithium-ion battery (LIB) degradation is critical for safe and reliable operation in real-world applications. In recent years, data-driven approaches powered by Machine Learning algorithms emerged as a promising solution, among which Deep Learning methods were proven to be effective for various tasks such as State of Charge and State of Health estimation and Remaining Useful Life prediction, however, their application for knee point estimation is still at an early stage. While experimental techniques, were demonstrated to be successful for detecting knees, current methods focus on tracking individual cycles rather than analyzing the overall trajectory of degradation, which could potentially offer better performance. In this paper, we introduce ICFormer, a novel Deep Learning model based on a Transformer encoder that leverages self-attention on the evolution of incremental capacity curves to accurately identify relevant changes in LIB degradation trajectories. The proposed model not only detects knees, but also anticipates them while also outperforming state-of-the-art approaches in diagnosing degradation modes. The effectiveness of the model is validated using both synthetic and experimental data. We demonstrate that the method can provide valuable knowledge on the factors contributing to capacity loss and offer advanced insights for battery management and predictive maintenance strategies.

Power law exponents for single bubbles growth in nucleate pool boiling at zero gravity

Nucleate pool boiling is an important boiling mode used in various fields of application. Bubble detachment and new bubble generation at the nucleation site is an important aspect of the process under terrestrial conditions. This sequence prevents prolonged observation of bubble growth phenomena. The problem can be circumvented by performing single bubble growth experiments under zero gravity conditions. Many experiments of this type are performed in a specially designed cell on board the International Space Station. Several combinations of boiling experimental parameters (pressure, heat flux, waiting time, degrees of subcooling) are tested. The bubble size evolution curve was found to represent the influences off the individual parameters best. Fitting attempts show that the experimental bubble growth curves can be nicely described by power law correlations. An analytical solution is given for the evolution of the liquid temperature field within the experimental test cell, in the absence of boiling incidents. It is shown that the time evolving difference between the solid/liquid interfacial temperature and the liquid saturation temperature is the basic factor that determines the bubble growth exponent. As an outcome, the whole experimental information on the bubble growth curves of 160 different boiling conditions is compressed in the form of tables that include the corresponding power law factors. These tables not only allow the reconstruction of the examined boiling curves but can also generate boiling curves in a dense grid of boiling conditions through interpolation of existing boiling data. The latter offers coherence and continuity in boiling computer codes over a broad range of conditions.

Unveiling the intricacies of attracting zones in magnetic binary systems: Investigating the impact of Yukawa correction

This study delves into the restricted three-body problem with a Yukawa correction to Newtonian gravitational forces, focusing on magnetic binary systems. We scrutinize the influence of Yukawa correction parameters (α, β) and the ratio of magnitude of magnetic moments (λ) on the system’s equilibrium points and their stability, zero-velocity curves. In our case, there exist of five and seven equilibrium points and all are found to be unstable for given range of parameters. Our examination extends to the basins of convergence and the existence of fractal under the influence of α and λ. Graphs drawn with the help of Wolfram Mathematica software vividly portray the parameter-driven evolution of equilibrium points, zero-velocity curves and basins of convergence. Furthermore, we explore the fractal characteristics within the basins of convergence, offering valuable insights into the complex dynamics of magnetic binary systems with Yukawa correction.

Strontium isotope compositions of Late Permian evaporites from the northernmost Thuringian Basin (Germany) indicate continental influence on the marine Zechstein Sea

In the Late Permian Zechstein Sea of Central Europe, up to 2000 m of evaporitic rocks were deposited in at least four consecutive cycles. The age of these evaporitic rocks could not yet be precisely determined, because they are virtually fossil-free and do not contain radiometrically datable volcanic layers. A chemostratigraphic age of the succession can be determined by comparing 87Sr/86Sr ratios of marine gypsum and anhydrite to the worldwide marine strontium evolution curve. Unfortunately, published 87Sr/86Sr data of the Zechstein succession are characterized by frequent outliers towards higher ratios, making an age assignment challenging. The scatter in 87Sr/86Sr ratios might be induced by different processes like the contribution of meteoric water to the brine, in-situ Rb decay, or post-depositional hydrothermal or diagenetic overprint. Here, we present a dataset of 26 new gypsum and anhydrite 87Sr/86Sr ratios from drill cores situated at “Alter Stolberg” in the northernmost Thuringian Basin. Evaporites of the Werra-, Staßfurt-, and Leine cycles were sampled. The close proximity of the drillings allows a very accurate assignment of the stratigraphic position of each sample, so that trends and outliers in 87Sr/86Sr ratios can easily be recognized. While the entire Werra Formation obviously revealed non-marine 87Sr/86Sr ratios, the lowermost 87Sr/86Sr ratios in the Staßfurt and Leine Formations can be assumed to represent marine ratios and allow estimating a chemostratigraphic age of 257‒254 Ma. The combination of the 87Sr/86Sr data with the mineral composition of the samples suggests a contribution of meteoric water, probably river water, to the Zechstein Sea as the main reason for the observed increase in 87Sr/86Sr ratios. Additional in-situ Rb decay, related to the riverine input of clay minerals, cannot be excluded. Modelling the amounts of sea water and meteoric water in the brine indicates that 83‒99% of meteoric water would be necessary to explain the highest 87Sr/86Sr ratios observed in the Werra Formation.Graphical abstract

Seismic stressing state evolution features of a FRP-BF structure revealed by modelling tested strain data

Researchers have been pursuing the accurate prediction of structural seismic capacity applying various theories and methods. Recently, structural stressing state theory explores a new way to assess structural anti-seismic capacity accurately. In this study, the new theory combining the modeling method in thermodynamic system is applied to investigate the dynamic strain data recorded in the shaking table test of a 1/5-scale four-story bottom frame model reinforced by fiber-reinforced polymer (FRP-BF structure), in order to reveal its definite stressing state features. The dynamic strain data at individual levels of white noise loading are modeled as state variables similar to a set of observations of the thermodynamic system. For the columns with fewer strain samples, the stressing state mode and its characteristic parameter curves are built based on the similarity between dynamic strain values. For the walls with more strain samples, the stressing state mode and characteristic parameter are derived by the differences of the accumulated state variables. Then, integrating the modes and characteristic parameters for columns and walls can obtain the stressing state mode and characteristic parameter of the FRP-BF structure. Further, the definite phase transition points are revealed by applying the clustering analysis criterion to detect the evolution curves of the characteristic parameters and to verify the evolution curves of the stressing state modes. The characteristic points define the elastoplastic branch point and the failure starting point of the FRP-BF structure. Both characteristic points surely exist in the tested strain data of structural seismic working process as the specific embodiment of the natural law from quantitative change to qualitative change of a system. Thus, the elastoplastic branch point and the failure starting point provide the new reference to the design and safety estimation of the FRP-BF structures.

A multi-layer nanocased model to explain the U-shaped evolution of shale gas permeability at constant confining pressure

Understanding the evolution of shale permeability is critical in efficiently recovering gas from shale reservoirs. Two representative profiles of permeability evolution are typically experimentally observed under constant confining pressure and incremented gas pressure – “U-shape” with increasing gas pressure but sometimes absent the second upright limb of the “U” at high gas pressures. Current models fail to address these two different profiles, potentially leading to inappropriate explanation of experiment observations or inaccurate predictions of gas production. In order to determine the mechanistic reason, a multi-layer nanocased model, in which transmissive nanotubes are embedded within a cylindrical sheath of matrix, is proposed. In the model, permeability evolution is defined as a function of the evolving nanotube radius within a total matrix radius. The ensemble structure governs the transition from local deformation of the nanotube wall to the global deformation of the matrix sheath, particularly as sorbing/swelling gas gradually permeates the sheath wall. The finite element method is employed to calculate permeability evolution from an initial equilibrium state to final equilibrium. We develop a series of permeability evolution curves that match various experimental profiles. Contrasting observed permeability responses are attributed to the competition between nanotube strain and matrix global strain. The former term enlarges the nanotube radius while the latter term swells the matrix declining the permeability value. Therefore, when the matrix global strain dominates at late time, permeability decreases. Conversely, a permeability recovery stage is barely observed in the late stage because in most cases global swelling dominates the permeability evolution and an extended observational period is necessary before this swelling appears. This is also the reason why the observed final permeability ratio is rarely greater than unity. A small nanotube radius or a large adsorption strain favors a significant decrease in permeability. When the nanotubes are located within the inorganic matrix, the permeability profile conforms to poro-elastic theory and the decreasing permeability stage is barely apparent or absent. The proposed model thus provides insight into the controls on permeability evolution in shales and the controlling impact of shale matrix properties by considering the inhomogeneities of the shale matrix.

Experimental and numerical studies on low-velocity impact of laminated C/SiC structures

Laminated C/SiC(carbon fiber reinforced silicon carbide composites) has the complicated nature of composite failure which include cracks for void defects at the meso and micro scales, complex cracks propagation of tunnel cracks, matrix cracks, delaminations and fiber cracks, orthotropic, and pseudoplastic behavior. It has technical challenge to solve all of them for complicated-mechanics problems by using multi-scale methodology. This paper focused tackling it by a model that lies between macro and meso scales, and proposed a new conceptual 3D FE-PDM(Finite Element - Progressive Damage Method). 3D FE-PDM was validated by the experiments of low-velocity impact of 2D C/SiC and 3D needled C/SiC. Damage initiation and evolution were controlled by strain in order to preventing stress chaos which could occur as cracks leading local stress relief. The multi-linear constitutive relations were adopted in orthotropic directions. The coupled effects of stresses between in-plane and out-of-plane were computed by adding damage coefficients into stiffness matrix. Cohesive Zone Method was used for delamination. The PDM approach was introduced for the 3D elements for intralaminar and cohesive elements for the interfaces. A parametric inversion methodology was put forward to determine the model parameters iteratively by comparing simulation results with the load-time curves, damage CT details of the experiments. Validation implies that, with small number of parameters, 3D FE-PDM is able to predict damage initiation of each phase knee, damage evolution, and load–displacement curve with good convergence for the low-velocity impact case. 2D woven and 3D needled non-woven C/SiC both have impact energy threshold and different damage evolution types.

Learning Curve in Robotic Stereoelectroencephalography: Single Platform Experience

Learning curve, training, and cost impede widespread implementation of new technology. Neurosurgical robotic technology introduces challenges to visuospatial reasoning and requires the acquisition of new fine motor skills. Studies detailing operative workflow, learning curve, and patient outcomes are needed to describe the utility and cost-effectiveness of new robotic technology. A retrospective analysis was performed of pediatric patients who underwent robotic stereoelectroencephalography (sEEG) with the Medtronic Stealth Autoguide. Workflow, total operative time, and time per electrode were evaluated alongside target accuracy assessed via error measurements and root sum square. Patient demographics and clinical outcomes related to sEEG were also assessed. Robot-assisted sEEG was performed in 12 pediatric patients. Comparison of cases over time demonstrated a mean operative time of 363.3 ± 109.5 minutes for the first 6 cases and 256.3 ± 59.1 minutes for the second 6 cases, with reduced operative time per electrode (P= 0.037). Mean entry point error, target point error, and depth point error were 1.82 ± 0.77 mm, 2.26 ± 0.71 mm, and 1.27 ± 0.53 mm, respectively, with mean root sum square of 3.23 ± 0.97 mm. Error measurements between magnetic resonance imaging and computed tomography angiography found computed tomography angiography to be more accurate with significant differences in mean entry point error (P= 0.043) and mean target point error (P= 0.035). The epileptogenic zone was identified in 11 patients, with therapeutic surgeries following in 9 patients, of whom 78% achieved an Engel class I. This study demonstrated institutional workflow evolution and learning curve for the Autoguide in pediatric sEEG, resulting in reduced operative times and increased accuracy over a small number of cases. The platform may seamlessly and quickly be incorporated into clinical practice, and the provided workflow can facilitate a smooth transition.

Multilevel thresholding image segmentation algorithm based on Mumford–Shah model

Abstract Image segmentation is one of the important tasks of computer vision and computer image processing, and the purpose of image segmentation is to achieve the extraction and recognition of the target image region. The classical Mumford–Shah (MSh) image segmentation model is used to achieve the segmentation of images. With the goal to get the best segmentation effect on images by minimizing the MSh energy generalization function, a level set strategy is developed, and a model with global information infinite curve evolution is utilized. However, considering the low efficiency of this model for processing level set curves and the general quality of image segmentation. A multi-layer threshold search scheme is proposed to achieve rapid convergence of the target image level set curve. The experimental results showed that the multi-level thresholding image segmentation algorithm based on the MSh model can significantly improve the segmentation effect of images and reduce the segmentation time. The suggested MSK method outperforms the MPO algorithm, SSA algorithm, and EMO algorithm in the picture segmentation convergence time test, respectively, in terms of runtime efficiency by 356, 289, and 71%. Additionally, it performs superbly in both threshold searches and picture quality tests. The research topic has significant reference value for the study of contemporary computer vision imaging technologies.

Adhesive and rheological properties of fresh mortar with manufactured sand as replacement of river sand

This paper investigates the adhesive properties of fresh mortar with manufactured sand (Msand) as replacement of river sand (Rsand). Adhesive properties were evaluated by normal force evolution curves from the tack test. Both static and dynamic yield stress were measured to elaborate the influence of Msand replacing Rsand on the adhesive properties. Results indicate that Msand increases the adhesive force, critical displacement, stiffness, and adhesive failure energy whereas shortens the debonding duration. Replacement of Rsand by Msand gradually promotes the transition of failure mode from cohesive rupture to adhesive rupture. The adhesive force of mixtures showing cohesive rupture is highly related to their static yield stress values.

Pullout behavior of geogrid reinforcement in calcareous sand

This study conducts a series of large-scale pullout tests to explore the pullout behavior of the biaxial geogrid-calcareous sand interface. It investigates the effects of normal stress, relative density, and embedded length on the interface pullout behavior of geogrid reinforcement in calcareous sand. In addition, this research examines changes in interface shear strength and the interface friction coefficient. The interface interaction mechanism of geogrid reinforcement in calcareous sand and the evolution of pullout force-clamp displacement curves are determined. The results indicated that the pullout force-clamp displacement curve primarily exhibits softening and hardening behaviors. The passive resistance of the geogrid mesh significantly influences the softening behavior, while shear friction predominantly affects the hardening behavior. The interface friction coefficient ranged from 0.28 to 0.88 for embedded lengths of 300 − 460 mm. The effects of relative density and embedded length on interface cohesion are more pronounced than those on the interface friction angle. When the embedded length increased from 300 to 460 mm, the rise in interface cohesion ranged from 42.0% to 47.7%, whereas the increase in internal friction angle ranged from 9.5% to 14.5%.

Description and outcomes of Afro-Caribbean children treated for multisystem inflammatory syndrome in the French West Indies

IntroductionSeveral studies have reported a higher frequency and greater morbidity and mortality of multisystem inflammatory syndrome in children (MIS-C) of black African descent. ObjectivesWe aimed to describe the clinical, laboratory and echocardiographic characteristics as well as outcomes of children with MIS-C requiring admission to a pediatric intensive care unit (PICU) in the French West Indies (FWI), where the majority of the population is Afro-Caribbean. MethodsAmbidirectional observational cohort study between April 1, 2020 and August 31, 2022. Children (age ≤18 years) with MIS-C and organ failure were included. Every patient was monitored and treated following the same protocol, with repeated biological tests, echocardiography, intravenous steroids and polyvalent immunoglobulins. The primary outcomes were clinical, laboratory and echocardiography characteristics. ResultsForty children (median age 7 years, range: 5–11) were included. The majority (77 %) were included prospectively. Thirty-five (87 %) had gastrointestinal symptoms, 30 (75 %) presented initial heart failure (with persisting diastolic dysfunction at day 7) and 18 (45 %) had pericarditis. Sixteen (40 %) were in cardiogenic shock and required inotropic support. Median duration of inotropic support and hospitalization in PICU were respectively 4 and 5 days. The evolution curves of the inflammatory variables matched after treatment. The clinical outcomes were favorable. The Delta variant was associated with the highest incidence of MIS-C. ConclusionThis is the first description of MIS-C course among children of Afro-Caribbean descent. The outcomes were good, without any death or cardiac sequelae. Our work does not support an ethnic susceptibility for severity of MIS-C in Afro-Caribbean population.