bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical modelling of macrosegregation in three-dimensional continuous casting of steel billets
Authors: Mramor K , Vertnik R , Šarler B
Published: May 2023

Macrosegregation presents a considerable defect in the continuous casting of billets and can critically affect the final properties of the product. The numerical modelling can help to predict and better understand the segregation and flow patterns inside the mould. The process is modelled with a physical model described by a set of conservation equations describing the t heat transfer, turbulence, fluid flow, solidification and segregation. A two-equation low-Re k-epsilon model and Abe-Kondoh-Nagano closures are used to close governing equations in this incompressible fluid flow example. The Boussinesq approximation is applied to account for the thermo-solutal buoyancy effects, and the Darcy approximation is applied for the description of the flow through the porous mushy zone. On a microscale, a lever rule solidification model is used to couple liquid fraction, temperature and concentration. The three-dimensional model is solved with the method based on local collocation with multiquadric radial basis functions on seven-nodded subdomains. The aim of this contribution is to explore the three-dimensional macrosegregation patterns of 0.51 wt% carbon steel in the solidified shell of the steel in the mould.
How electromagnetic stirring influences fluid flow in continuous casting of steel
Authors: Fainberg Jakob , Hepp Erik , Shvydkii Evgenii
Published: May 2023

State-of-art simulation models provide quantitative insights into flow, solidification and stress formation for continuous casting processes. This includes the entire process, from the tundish and the flow into the mold to the solidifying strand, which is withdrawn through various cooling zones. Process simulation and optimization provides important information about quality and productivity to evaluate process alternatives. This is only be possible if all relevant process parameters can be taken into account. The use of electromagnetic stirring is a technology which plays a significant role in the majority of continuous casting processes worldwide and its effects cannot be neglected in simulation models. This paper will discuss the modeling of electromagnetic stirring (EMS) and its impact on steel slab continuous casting.

Two cases with and without EMS are presented. The theoretical background to calculate the Lorentz force are described. The EMS calculation described here works with traveling (linear) magnetic fields. The effect of the EMS on the flow behavior, solidification and macrosegregation is shown on an industrial-scale slab casting.

This information leads to a better understanding of the EMS process in industrial applications to avoid casting defects, improve the quality of the final product, and increase the efficiency of the casting process.
Non-metallic inclusion (NMI) deposition in a slide-gate submerged entry nozzle (SEN)
Authors: Shibly K U R M , Tullis S , Phillion A B
Published: May 2023

Clogging of the submerged entry nozzle (SEN) is a common and persistent issue in the continuous casting process for steel alloys. The dominant clogging mechanism has been attributed to the deposition and accumulation of non-metallic inclusions (NMI) in the steel melt. Prior studies of NMI deposition assume that every collision between an inclusion and the nozzle wall results in adhesion, which is unrealistic. In this study, a macroscopic transport model for fluid and NMI motion is combined with a microscale model for NMI adhesion and applied to a slide-gate nozzle. Eight NMI sticking probabilities (S) and three slide-gate linear opening positions are explored. Simulation results indicated that the more closed the slide-gate, the greater the total deposition of NMI. When the slide-gate was partially open, the particle area number density was highest above, within and just below the slide-gate. But when the slide-gate was fully opened the deposition was concentrated in the upper tundish nozzle. Deposition behaviour fell into two regimes based on S. When S ≤ 0.05, the particle deposition was low and increased rapidly with sticking probability. When S ≥ 0.05, the particle deposition was high but changed very little with sticking probability. Changes to sticking probability did not significantly affect the deposition locations or relative distribution of particles within the nozzle.
In situ observation of solidification in peritectic steels and evaluation of the strains induced in the solidifying shell
Authors: Yasuda H , Narumi T , Katsube R , Nanri Y
Published: May 2023

In the continuous casting of peritectic steels, unevenness and cracks of the solidifying shell are typical casting defects. This study focuses on the ferrite–austenite transformation and the influence of the transformation on the solidifying shell deformation. In situ observations revealed that the austenite hardly nucleated and, consequently, the undercooled ferrite massively transformed to the austenite in the solid state. Simultaneously, the austenite rapidly solidified in the remaining liquid. The volume changes due to the ferrite–austenite transformation and the solidification shrinkage were measured using time-resolved tomography. On the basis of the observations and measurements, a model that includes the ferrite–austenite transformation and the austenite solidification was proposed to evaluate the volumetric strains in the solidifying shell. There was a sharp peak in the volumetric strains derived from the model at hypo-peritectic compositions. This work demonstrates the need to include the ferrite–austenite transformation in the solid state and the rapid austenite solidification for understanding the solidifying shell deformation in peritectic steels.
Flow-enhanced remelting of settling/floating globular crystals during mixed columnar-equiaxed solidification
Authors: Wu M , Zhang Z , Zhang H , Ludwig A , Kharicha A
Published: May 2023

Previously, the authors have used a mixed columnar-equiaxed solidification model, successfully ‘reproduced’ the solidification benchmark experiments on the Sn-10wt.%Pb alloy under natural/forced convections (travelling magnetic stirring) as performed at SIMAP laboratory [Int. J. Heat Mass Transf. 85 (2015) 438-54]. The current contribution is to address the flow-effect on the remelting of settling/floating crystals during the mixed columnar-equiaxed solidification. The re-melting or growth is controlled by diffusion of solute in the liquid boundary layer. The diffusion length due to the flow-effect is modelled as a function of Schmidt and Reynolds numbers. The modelling results show that remelting rate of the floating/settling crystals, which originate from fragmentation and then brought to the superheated region by the forced flow, can be enhanced by the flow. In turn the released latent heat can reduce the temperature locally (even globally), hence to speed up the solidification of the columnar structure. Additionally, the solidification-migration-remelting of equiaxed grains present an important macrosegregation mechanism. By solidification of a crystal in the cold region it rejects solute, while by remelting of the crystal it dilutes the surrounding melt. These phenomena are found critical in many engineering castings with mixed columnar-equiaxed solidification.
A mathematical examination of the impact of mould transparency to infrared radiation on solidification during the investment casting process
Authors: Jones C A , Jarfors A E W , Rogers E , Vrethed P , Silva P , Jolly M R
Published: May 2023

Investment casting is a highly dynamic process during which multiple competing physical phenomena are at work. Those seeking to understand and simulate such processes computationally are confronted with a considerable task, balancing accuracy with efficiency. Approximations and models based on well-understood and documented fundamental physics are powerful tools in a modeller’s arsenal. Driven by observed discrepancies between experimental thermocouple measurements and simulation predictions of casting temperatures, this work explores the additional alloy cooling mechanism of mould transparency to infrared radiation, targeting a new mathematical approximation applicable in such situations. Direct attenuation, scattering from coarse sand, sand distribution in the mould and material temperatures play a role in the extent of radiation transparency that must be considered. From this model, estimation of the additional cooling rate resulting from expected mould transparency can be determined and applied as a corrective measure to computation fluid dynamics (CFD) simulation results that do not capture this phenomenon.
Multiphase flow model of semi solid solidification of novel Al-15Mg2Si-Si composite
Authors: Das Prosenjit
Published: May 2023

In this work, a volume averaging technique based Eulerian multiphase flow CFD (Computational Fluid Dynamics) model is developed to simulate the semi-solid solidification of the cooling slope generated Al-15Mg2Si-4.5Si composite slurry. The four phases considered here are liquid (l), primary solid (Mg2Si), secondary solid (α-Al) and air (a). Whereas latent heat release during solidification is tackled via a temperature correction scheme. The effect of recalescence is also observed in the present solidification model. The simulation findings include shape and size of the α-Al and primary Mg2Si grains, solid fraction, temperature, melt viscosity etc. The developed multiphase flow model of cooling slope casting (semi solid solidification) is applied to a test case having melt pouring temperature (into the slope) of 650°C (923K). The simulation findings are then validated with the help of measurements of microstructural features observed in the experimental (optical) micrographs of the solidified samples.
Integrated property predictions during casting and heat treatment of Al-Si-Cu-Mg alloys by precipitation simulation
Authors: Mao Fengxin , Weidt Moritz , Roeser Frank , Thorborg Jesper , Barrales-Mora Luis
Published: May 2023

The production and manufacture of aluminium castings typically involves multiple heat treatment process steps. Simulation tools are very useful to help predict the evolution of mechanical properties, to improve process parameters and as a guideline for casting design. In this study, a kinetic model, based on Nucleation and Growth Theory (CNGT), was developed and implemented for modelling heat treatment in a casting process simulation tool. Starting from information generated from the simulation of solidification and cooling of the casting, simulation was carried out to predict further precipitation behaviour of multiple Cu or Mg-Si -containing phases during solution treatment, quenching, and artificial ageing processes in heat treatment of Al alloys. Model validation was carried out within the research cluster “Advance Metals and Processes” in Aachen, Germany. Heat treatments were performed on two different Al-Si-Cu-Mg alloys with different quench methods and at different ageing temperatures. Experimental investigations including atom probe, wavelength dispersive X-ray spectroscopy, and tensile tests were conducted to calibrate and validate the model. The simulations showed good agreement for the studied conditions and a promising modelling approach for integrated simulation of casting and heat treatment for industrial applications.
Development of a data assimilation system for the investigation of the dendrite solidification process by integrating in situ X-ray imaging and phase-field simulation
Authors: Yamamura A , Sakane S , Ohno M , Yasuda H , Takaki T
Published: May 2023

The dendrite solidification process has been observed and simulated using state-of-the-art techniques, such as time-resolved X-ray tomography (4D-CT) and high-performance phase-field (PF) simulations. 4D-CT has enabled the direct observation of the 3D dendrite growth in opaque alloys. However, the spatiotemporal resolution is not sufficient for investigating fast phenomena because a 3D solidification structure is obtained using hundreds of transmission images during the 180° rotation of a sample. High-performance PF simulations have enabled the simulation of multiple 3D dendrite growth phenomena. However, the material properties required in PF solutions of alloys are often unavailable. Therefore, integrating in situ X-ray observations with PF simulations using data assimilation is a promising approach for simultaneously solving these issues. In this study, we developed a data assimilation system with an ensemble Kalman filter, in which the solid fraction along the thickness of a sample was used as observation data to enable data assimilation using X-ray transmission images. The performance of the developed data assimilation system was evaluated via twin experiments for columnar dendrite growth during the directional solidification of a binary alloy in a thin film. The results showed that data assimilation using the solid fraction as observation data estimated the material properties and solidification morphologies with reasonable accuracy.
Modelling of major phases formation during solidification of Ferro-Silicon-Magnesium
Authors: Gouttebroze S , Marthinsen A , Kroka B , Götz A , Ott E
Published: May 2023

Ductile cast iron, also known as nodular cast iron, is a graphite-rich cast iron with high impact and fatigue resistance, due to its nodular graphite inclusions. Ductile cast iron is produced by incorporating additives (often FeSi alloys) to the iron base metal at different production steps to obtain the desired graphite shape. A crucial step is the addition of Magnesium to promote the spheroidization of the graphite. The most common method is by adding crushed and sized Ferro-Silicon-Magnesium (FSM). The alloy composition, microstructure, and sizing are assumed to affect the key parameters of this reaction, namely, reactivity, recovery, and slag formation. Therefore, the study of the solidification of FSM is important to understand and predict its performance at the foundries. The present work aims at understanding and predicting numerically the formation of the major phases during the solidification process. Two approaches have been used: thermodynamic calculations through Thermo-Calc solver and phase field modelling using MICRESS. The models have been calibrated by comparison with advanced statistical characterization of the microstructure. The results indicate a competitive growth of the major phases and transformation of phases in solid state that can be emulated by the model.
Numerical study on the formation of spurious grains and freckles during the directional solidification of superalloys
Authors: Zhang H , Wu M , Liu X , Ma D , Song M , Ludwig A , Kharicha A
Published: May 2023

Freckles, a significant issue encountered during the directional solidification of superalloys, are recognised by a trail of equiaxed grains parallel to the direction of gravity accompanied by local eutectic enrichment. In the current study, a mixed-columnar-equiaxed multiphase volume-average solidification model was employed to study the formation of freckles in superalloy casting. Fragments produced via flow-driven and capillary-driven fragmentation mechanisms are considered as the source of spurious grains. The transport and the growth/remelting of the fragments are considered. According to the simulation results, some segregation channels develop at the corners of the casting. Flow-driven fragments are produced in/around the segregation channels, whereas capillary-driven fragments are produced at a certain depth of the mushy zone across the entire section of the casting. The fragmentation rate caused by the flow-driven mechanism is several orders of magnitude larger than that caused by the capillary-driven mechanism, i.e. the flow-driven fragmentation mechanism is dominant for the currently investigated sample. After the solidification process, four freckles formed at the casting corners on the shadowed side, whereas it was freckle-free on the bright side.
Phase field simulation of segregation and precipitates formation during steel solidification
Authors: Santillana B , Paruchuri V , Prahl U
Published: May 2023

Multi-phase field modelling using MICRESS® has been used to perform simulations of the nucleation and evolution microstructure in a 2D domain as function of fundamental thermo-physical parameters, time, cooling rate and chemical composition during solidification. In order to have a better understanding of primary precipitates evolution during solidification in a case hardening steel and the precipites chosen were niobium-carbides (NbC) and manganese sulphides (MnS), simulations were done including the nucleation and growth of precipitates and coupled through thermodynamic databases. The results show a good comparison with the experimental microstructure measured with SEM-EDX measurements. The simulated time dependent segregation profiles of Nb and Mn in the interdendritic regions, and the precipitates composition, have a good similarity with the measurements. Even when the size and morphology of the NbC and MnS particles has a difference in the both simulated and experimental situations, this can be explained by the low resolution used in the simulation. This publication shows the modelling results and the comparison with the experimental measurements.
Tracking the evolution of hot tears in aluminium alloys using high-speed X-ray imaging
Authors: Han Insung , Feng Shikang , Lui Andrew , Wilde Fabian , Grant Patrick S , Liotti Enzo
Published: May 2023

Hot tears are detrimental defects forming during the final stage of solidification when the remaining liquid loses the capacity to compensate for liquid to solid volume shrinkage. Although a mature semi-quantitative description of hot tearing has been developed, little is known about the dynamic evolution of hot tears as experimental studies have been conducted mostly post-solidification or in semi-static in-situ conditions. Here, we present a methodology to investigate the evolution of hot tears with high spatial and temporal resolution using synchrotron-based X-ray radiography. We develop a novel hot tear detection and tracking algorithm for quantification of hot tear density, area fraction and merging from the analysis of radiographic sequences of the solidification of thin metal samples. The methodology is demonstrated for an Al-5wt%Cu alloy and examples of the results and new insights that can be achieved are described.
Revealing and simulating the effect of hidden damage on local and full-field deformation behaviour of cast aluminium
Authors: Olofsson Jakob , Bogdanoff Toni , Tiryakioğlu Murat
Published: May 2023

Pores have been the main focus of quality assurance in castings. Latest research has shown that in aluminium castings pores can form only if there is existing entrainment damage, i.e., pores are merely the visible parts of the entrainment damage, and usually invisible damage is much more extensive. However, its effect on deformation behaviour has not been previously established or observed in-situ. This work applies 2D Digital Image Correlation (DIC) to an in-situ full-field stress-strain analysis of tensile samples with a non-conventional heterogeneous stress distribution. The observations reveal that the effect of hidden damage extends far beyond its impact on fracture behaviour and is responsible for initiating local strain concentrations during deformation. By extracting local stress-strain data, FE simulations have been performed to mimic the effect of local hidden damage on the heterogeneous stress-strain field. SEM and FIB-SEM analysis has been applied to investigate the cause for the strain concentrations. The combined results show that hidden damage in the form of oxide films is not only responsible for premature fracture, but also affects the deformation behaviour of tensile samples by introducing dispersed strain concentrations.
Integrated fatigue life predictions of aluminium castings using simulated local microstructure and defects
Authors: Olofsson Jakob
Published: May 2023

In this work, an integrated simulation approach previously developed for static FE analyses is extended to microstructure- and defect-based fatigue life assessments of castings. The approach,the closed chain of simulations for cast components, combines casting process simulation with microstructure modelling and local material characterisation to generate heterogeneous material data for FE analysis and fatigue life assessment. The method is demonstrated on a High-Pressure Die Cast aluminium component. Areas with a high risk of defects are identified based on the simulated solidification conditions, and heterogeneous material data for the fatigue life analysis is generated. Fatigue testing has been performed with different levels of porosities to quantify the effect of defects on the element-specific Wöhler curves. Pore characteristics are assessed using 2D X-ray, fracture surface analysis and Kitagawa diagram. The results highlight the importance of taking the risk of defect formation into consideration when designing industrial aluminium castings subjected to fatigue loads.
A microphysiological model of bone development and regeneration
Authors: Whelan Ian T , Burdis Ross , Shahreza Somayeh , Moeendarbary Emad , Hoey David A , Kelly Daniel J
Published: May 2023

Endochondral ossification (EO) is an essential biological process than underpins how human bones develop, grow, and heal in the event of a fracture. So much is unknown about this process, thus clinical manifestations of dysregulated EO cannot be adequately treated. This can be partially attributed to the absence of predictive in vitro models of musculoskeletal tissue development and healing, which are integral to the development and preclinical evaluation of novel therapeutics. Microphysiological systems, or organ-on-chip devices, are advanced in vitro models designed for improved biological relevance compared to traditional in vitro culture models. Here we develop a microphysiological model of vascular invasion into developing/regenerating bone, thereby mimicking the process of EO. This is achieved by integrating endothelial cells and organoids mimicking different stages of endochondral bone development within a microfluidic chip. This microphysiological model is able to recreate key events in EO, such as the changing angiogenic profile of a maturing cartilage analogue, and vascular induced expression of the pluripotent transcription factors SOX2 and OCT4 in the cartilage analogue. This system represents an advanced in vitro platform to further EO research, and may also serve as a modular unit to monitor drug responses on such processes as part of a multi-organ system.
3D bioprinting of tyramine modified hydrogels under visible light for osteochondral interface
Authors: Senturk Efsun , Bilici Cigdem , Afghah Ferdows , Khan Zaeema , Celik Suleyman , Wu Chengtie , Koc Bahattin
Published: May 2023

Recent advancements in tissue engineering have demonstrated a great potential for the fabrication of three-dimensional (3D) tissue structures such as cartilage and bone. However, achieving structural integrity between different tissues and fabricating tissue interfaces are still great challenges. In this study, an in situ crosslinked hybrid, multi-material 3D bioprinting approach was used for the fabrication of hydrogel structures based on an aspiration-extrusion microcapillary method. Different cell-laden hydrogels were aspirated in the same microcapillary glass and deposited in the desired geometrical and volumetric arrangement directly from a computer model. Alginate and carboxymethyl cellulose were modified with tyramine to enhance cell bioactivity and mechanical properties of human bone marrow mesenchymal stem cells-laden bioinks. Hydrogels were prepared for extrusion by gelling in microcapillary glass utilizing an in situ crosslink approach with ruthenium (Ru) and sodium persulfate photo-initiating mechanisms under visible light. The developed bioinks were then bioprinted in precise gradient composition for cartilage-bone tissue interface using microcapillary bioprinting technique. The biofabricated constructs were co-cultured in chondrogenic/osteogenic culture media for three weeks. After cell viability and morphology evaluations of the bioprinted structures, biochemical and histological analyses, and a gene expression analysis for the bioprinted structure were carried out. Analysis of cartilage and bone formation based on cell alignment and histological evaluation indicated that mechanical cues in conjunction with chemical cues successfully induced MSC differentiation into chondrogenic and osteogenic tissues with a controlled interface.
Performance analysis of various training algorithms of deep learning based controller
Authors: Prasad Bhawesh , Kumar Raj , Singh Manmohan
Published: May 2023

Advances in artificial neural networks (ANN), specifically deep learning (DL), have widened the application domain of process control. DL algorithms and models have become quite common these days. The training algorithm is the most important part of an ANN that affects the performance of the controller. Training algorithms optimize the weights and biases of the ANN according to the input-output patterns. In this paper, the performance of different training algorithms was evaluated, analysed, and compared in a feed-forward backpropagation architecture. The training algorithms were simulated on MATLAB R2021b with license number 1075356. Training data were generated using two benchmark problems of the process control system. The performance, gradient, training error, validation error, testing error, and regression of the different training algorithms were obtained and analysed. The data shows that the Levenberg-Marquardt (LM) algorithm produced the best validation performance with a value of 2.669*10−14 at 2000 epochs, while ‘traingd’ and ‘traingdm’ algorithms did not improve beyond their initial values. The LM algorithm tends to produce better results than other algorithms. These results indicate that the LM backpropagation best suits these types of benchmark problems. The results also suggest that the choice of training algorithm can significantly impact the performance of a neural network.
Conduction and entropy analysis of a mixed memristor-resistor model for neuromorphic networks
Authors: Cipollini Davide , Schomaker Lambert R B
Published: May 2023

To build neuromorphic hardware with self-assembled memristive networks, it is necessary to determine how the functional connectivity between electrodes can be adjusted, under the application of external signals. In this work, we analyse a model of a disordered memristor-resistor network, within the framework of graph theory. Such a model is well suited for the simulation of physical self-assembled neuromorphic materials where impurities are likely to be present. Two primary mechanisms that modulate the collective dynamics are investigated: the strength of interaction, i.e. the ratio of the two limiting conductance states of the memristive components, and the role of disorder in the form of density of Ohmic conductors (OCs) diluting the network. We consider the case where a fraction of the network edges has memristive properties, while the remaining part shows pure Ohmic behaviour. We consider both the case of poor and good OCs. Both the role of the interaction strength and the presence of OCs are investigated in relation to the trace formation between electrodes at the fixed point of the dynamics. The latter is analysed through an ideal observer approach. Thus, network entropy is used to understand the self-reinforcing and cooperative inhibition of other memristive elements resulting in the formation of a winner-take-all path. Both the low interaction strength and the dilution of the memristive fraction in a network provide a reduction of the steep non-linearity in the network conductance under the application of a steady input voltage. Entropy analysis shows enhanced robustness in selective trace formation to the applied voltage for heterogeneous networks of memristors diluted by poor OCs in the vicinity of the percolation threshold. The input voltage controls the diversity in trace formation.
The Effect of Rhinoplasty Dissection Planes (Sub-SMAS, Subperichondrial, and Subperiosteal) on the Viability of Diced Cartilage Grafts in a Rabbit Model
Authors: Eravci Fakih Cihat , Kaplan Ömer , Oltulu Pembe , Arbağ Hamdi , Eryilmaz Mehmet Akif , Aricigil Mithat , Dündar Mehmet Akif
Published: May 2023

Background

Dorsal preservation surgeries in which the subperichondral and subperiosteal planes are used to elevate the soft tissue envelope of the nose have become increasingly widespread because they can reduce postoperative edema and promote faster healing. However, the effects of surgical dissection planes on the viability of cartilage grafts are not known.

Objective

The aim of this study was to determine, in a rabbit model, the viability of diced cartilage grafts in different rhinoplasty dissection planes (sub–superficial musculoaponeurotic system [SMAS], subperichondral, subperiosteal).

Methods

Diced cartilage samples were placed in the sub-SMAS, subperichondrial, and subperiosteal planes, and after 90 days, histopathologic analysis was performed. Cartilage graft viability was evaluated based on the loss of chondrocyte nuclei in the lacuna, the presence of peripheral chondrocyte proliferation, and the loss of matrix metachromasia in the chondroid matrix.

Results

The median [interquartile range] percentages of live chondrocyte nucleus viability in the sub-SMAS, subperichondrial, and subperiosteal groups were 67.5% [18.75%] (range, 60%-80%), 35% [17.5%] (range, 20%-45%), and 20% [30.0%] (range, 10%-45%), respectively; and the percentages of peripheral chondrocyte proliferation were 80.0% [22.5%] (range, 60%-90%), 30% [28.75%] (range, 15%-60%), and 20% [28.75%] (range, 5%-60%), respectively. There was strong statistical significance in both parameters (P = .001). Intergroup examination revealed a difference between the sub-SMAS and the other surgical planes (P = .001 for both parameters). A smaller loss of chondrocyte matrix was observed in the sub-SMAS group compared with the other 2 groups, which supports the findings of cartilage viability (P = .006).

Conclusions

Elevating the soft tissue envelope of the nose in the sub-SMAS surgical plane preserves the viability of cartilage grafts better than subperichondrial and subperiosteal elevation.
Comparison and benchmark of structural variants detected from long read and long-read assembly
Authors: Lin Jiadong , Jia Peng , Wang Songbo , Kosters Walter , Ye Kai
Published: May 2023

Structural variant (SV) detection is essential for genomic studies, and long-read sequencing technologies have advanced our capacity to detect SVs directly from read or de novo assembly, also known as read-based and assembly-based strategy. However, to date, no independent studies have compared and benchmarked the two strategies. Here, on the basis of SVs detected by 20 read-based and eight assembly-based detection pipelines from six datasets of HG002 genome, we investigated the factors that influence the two strategies and assessed their performance with well-curated SVs. We found that up to 80% of the SVs could be detected by both strategies among different long-read datasets, whereas variant type, size, and breakpoint detected by read-based strategy were greatly affected by aligners. For the high-confident insertions and deletions at non-tandem repeat regions, a remarkable subset of them (82% in assembly-based calls and 93% in read-based calls), accounting for around 4000 SVs, could be captured by both reads and assemblies. However, discordance between two strategies was largely caused by complex SVs and inversions, which resulted from inconsistent alignment of reads and assemblies at these loci. Finally, benchmarking with SVs at medically relevant genes, the recall of read-based strategy reached 77% on 5X coverage data, whereas assembly-based strategy required 20X coverage data to achieve similar performance. Therefore, integrating SVs from read and assembly is suggested for general-purpose detection because of inconsistently detected complex SVs and inversions, whereas assembly-based strategy is optional for applications with limited resources.
A-140 MANAGEMENT OF NON-METASTATIC DUODENAL NEUROENDOCRINE TUMOURS
Authors: Christou N , Mekkan Bouv-Hez M , Derbey L , de Mestier L , Lorenzo D , Walter T , Perrier M , Cadiot G , Goichot B , Pracht M , Lièvre A , Coriat R , Valancot S , Guimbaud R , Carrere N , Bacoeur-Ouzillou O , Belleannée G , Smith D , Laboureau S , Hescot S , Julie C , Teissier-Clément M , Thereaux J , Ferru A , Evrad C , Mathonnet M ,   GTE, Endocrine Tumors Group
Published: May 2023

Background

The management of duodenal neuroendocrine tumours (NET) between 1 and 2 cm is not codified. Currently, depending on the centre, endoscopic (ER) or surgical (SR) resection is offered.

The main objective of our study was to describe the management of non-metastatic duodenal NETs in France.

Methods

A study was conducted on 153 patients with non-metastatic duodenal NET diagnosed between 2000 and 2019 in 14 French centres by the GTE group (Endocrine Tumors Group).

Results

58 (37.9%) patients treated with ER and 95 (62.1%) patients treated with SR were found. Surgery allowed significantly more complete resection than endoscopy (p < 0.001). ER margins were significantly less well-defined than SR margins (p < 0.001). Among the 51 patients with positive lymph node dissection, tumour size was ≤ 1 cm in 25 cases, between 1 and 2 cm in 14 cases and ≥ 2 cm in 12 patients. No difference in survival was demonstrated regardless of type of treatment. Surgical complications were more numerous than endoscopic complications (p = 0.001). Regardless of the type of incomplete resection, there was no significant difference between the two groups according to the criteria of location, size, grade, or adenopathy. In the subgroup analysis of duodenal NETs between 11 and 19 mm, the tumour stages were equivalent in pre-procedure between the two groups. In contrast, there was a difference in post-procedure after anatomopathological analysis (p = 0.001).

Conclusion

Based on the study results, the type of endoscopic or surgical resection of duodenal NETs has no impact on the long-term results. Lymph node invasion is independent of tumour size.
A-217 IMPACT OF PREOPERATIVE LUGOL'S IODINE ON SURGERY FOR GRAVES DISEASE. SHORT-TERM RESULTS FROM LIGRADIS MULTICENTER RANDOMISED CLINICAL TRIAL
Authors: Villar-del-Moral J M , Guadarrama González F J , Valdés de Anca A , Muñoz-Pérez N , Rubio-Manzanares Dorado M , Marín Velarde C , Moreno-Llorente P , Gamborino Caramés E , Martí Fernández R , de la Quintana Basarrate A , Ros-López S , García-Carrillo M , Mercader Cidoncha E , Lorente Poch L , Vidal-Pérez O , Febrero Sánchez B , Franch-Arcas G , Luengo Pierrard P , Artes Caselles M , Muñoz-de-Nova J L
Published: May 2023

Background

Many clinical guidelines recommend the preoperative administration of Lugol's solution (LS) for patients undergoing thyroidectomy for Graves’ disease (GD), mainly based on low-quality evidence. Our aim was to assess its influence on intra and postoperative outcomes in patients undergoing total thyroidectomy (TT) for GD.

Methods

We performed a nationwide multicentre randomised controlled trial including euthyroid patients scheduled for TT due to GD. Patients were randomised for either receiving or not preoperative LS. Surgeons were blinded for treatment assignment. The primary outcome was the overall rate of postoperative complications. Secondary outcomes were intraoperative events and permanent morbidity.

Results

136 patients were included (68 in each arm), without preoperative differences among groups. The rate of patients who developed any complication was 51.5% in LS arm vs. 50% in controls (p=1). Postoperative hypocalcaemia appeared in 45.6% vs. 38.2% (p=0.487). The rate of postoperative vocal cord palsy was 6.1% vs. 3.3% (p=0.682). Median Thyroidectomy Difficulty Scale score was slightly higher in the LS group (10 vs. 9; p=0.031). No differences among groups were observed regarding surgical time, intraoperative bleeding, gland weight, or the rate of loss of signal in neuromonitoring. Long-term results have not yet been evaluated.

Conclusion

Preoperative iodine preparation can be safely obviated facing TT for GD, regarding the intraoperative difficulty and postoperative complications. If long-term results sustain these results, current advice for presurgical preparation in GD could be challenged.
A-310 18F-FLUOROCHOLINE-PET/CT IS THE BETTER TOOL TO LOCALISE “NEGATIVE” PARATHYROID ADENOMAS – INTRAOPERATIVE CORRELATION AND 12 MONTH POSTOPERATIVE RESULTS
Authors: Smaxwil C , Busch M , Naddaf A , Wagner J , Zielke A
Published: May 2023

Background

To characterise the diagnostic performance of 18F-Fluorocholine PET/CT (FCH-PET/CT) to localise parathyroid adenomas (PA) in primary hyperparathyroidism (pHPT) when ultrasound (US) and MIBI-Scan (MS) failed - intraoperative correlation and one year follow up.

Methods

Beginning in 07/2017 FCH-PET/CT was employed in patients with proven pHPT in whom US and MS delivered either incongruent or negative findings. All patients were offered cervical explorations with intraoperative PTH-monitoring (IO-PTH) and followed for 12 months postoperatively. Imaging results were correlated to operative findings and histopathologic reports and to short term biochemical outcome as well as one-year postoperative follow-up data.

Results

From 07/2017 to 11/2022, 1085 patients were operated for pHPT. In this period, 215 FCH-PET/CT were performed suggesting PA(s) in 176, 6 false positive, and 33 false negative (sensitivity 84.2%, PPV 96.7%). Of the 95 cases were US and MIBI both gave negative results, FCH-PET/CT accurately localised PA(s) to the respective side of the neck in all the 72 FEC-PET-positive cases (global sensitivity of 75.8%); and was negative in 23 (24.2%). In the 12-month postoperative follow up (currently matched by 61/95) there was no biochemical persistent disease. However, 3 patients exhibited PTH or calcium at the upper limit of norme, thus, a recurrence cannot be reliably excluded so far.

Conclusion

FCH-PET/CT allows for planned unilateral and focused as opposed to bilateral explorations, especially when preoperative parathyroid localisation with US and MiBI fails. We, therefore, suggest FCH-PET/CT as the preferred tool for the localisation of the “negative” PA.
Early threat perception is independent of later cognitive and behavioral control. A virtual reality-EEG-ECG study
Authors: Lu Juanzhi , Kemmerer Selma K , Riecke Lars , de Gelder Beatrice
Published: May 2023

Research on social threat has shown influences of various factors, such as agent characteristics, proximity, and social interaction on social threat perception. An important, yet understudied aspect of threat exposure concerns the ability to exert control over the threat and its implications for threat perception. In this study, we used a virtual reality (VR) environment showing an approaching avatar that was either angry (threatening body expression) or neutral (neutral body expression) and informed participants to stop avatars from coming closer under five levels of control success (0, 25, 50, 75, or 100%) when they felt uncomfortable. Behavioral results revealed that social threat triggered faster reactions at a greater virtual distance from the participant than the neutral avatar. Event-related potentials (ERPs) revealed that the angry avatar elicited a larger N170/vertex positive potential (VPP) and a smaller N3 than the neutral avatar. The 100% control condition elicited a larger late positive potential (LPP) than the 75% control condition. In addition, we observed enhanced theta power and accelerated heart rate for the angry avatar vs. neutral avatar, suggesting that these measures index threat perception. Our results indicate that perception of social threat takes place in early to middle cortical processing stages, and control ability is associated with cognitive evaluation in middle to late stages.
Protein arginine methyltransferase 5–mediated arginine methylation stabilizes Kruppel-like factor 4 to accelerate neointimal formation
Authors: Liu He , Dong Xiaoliang , Jia Kunpeng , Yuan Baohui , Ren Zhengnan , Pan Xiaohua , Wu Jianjin , Li Jiahong , Zhou Jingwen , Wang Ru-Xing , Qu Lefeng , Sun Jia , Pan Li-Long
Published: May 2023

Aims

Accumulating evidence supports the indispensable role of protein arginine methyltransferase 5 (PRMT5) in the pathological progression of several human cancers. As an important enzyme-regulating protein methylation, how PRMT5 participates in vascular remodelling remains unknown. The aim of this study was to investigate the role and underlying mechanism of PRMT5 in neointimal formation and to evaluate its potential as an effective therapeutic target for the condition.

Methods and results

Aberrant PRMT5 overexpression was positively correlated with clinical carotid arterial stenosis. Vascular smooth muscle cell (SMC)-specific PRMT5 knockout inhibited intimal hyperplasia with an enhanced expression of contractile markers in mice. Conversely, PRMT5 overexpression inhibited SMC contractile markers and promoted intimal hyperplasia. Furthermore, we showed that PRMT5 promoted SMC phenotypic switching by stabilizing Kruppel-like factor 4 (KLF4). Mechanistically, PRMT5-mediated KLF4 methylation inhibited ubiquitin-dependent proteolysis of KLF4, leading to a disruption of myocardin (MYOCD)–serum response factor (SRF) interaction and MYOCD–SRF-mediated the transcription of SMC contractile markers.

Conclusion

Our data demonstrated that PRMT5 critically mediated vascular remodelling by promoting KLF4-mediated SMC phenotypic conversion and consequently the progression of intimal hyperplasia. Therefore, PRMT5 may represent a potential therapeutic target for intimal hyperplasia–associated vascular diseases.
Emotional factors, medical interventions and mode of birth among low-risk primiparous women in Poland
Authors: Nenko Ilona , Kopeć-Godlewska Katarzyna , Towner Mary C , Klein Laura D , Micek Agnieszka
Published: May 2023

Background and objectives

Birth is a critical event in women’s lives. Since humans have evolved to give birth in the context of social support, not having it in modern settings might lead to more complications during birth. Our aim was to model how emotional factors and medical interventions related to birth outcomes in hospital settings in Poland, where c-section rates have doubled in the last decade.

Methodology

We analysed data from 2363 low-risk primiparous women who went into labor with the intention of giving birth vaginally. We used a model comparison approach to examine the relationship between emotional and medical variables and birth outcome (vaginal or c-section), including sociodemographic control variables in all models.

Results

A model with emotional factors better explained the data than a control model (ΔAIC = 470.8); women with continuous personal support during labor had lower odds of a c-section compared to those attended by hospital staff only (OR = 0.12, 95% CI = 0.09 − 0.16). A model that included medical interventions also better explained the data than a control model (ΔAIC = 133.6); women given epidurals, in particular, had increased odds of a c-section over those who were not (OR = 3.55, 95% CI = 2.95 − 4.27). The best model included variables for both the level of personal support and the use of epidural (ΔAIC = 598.0).

Conclusions and implications

Continuous personal support during childbirth may be an evolutionarily informed strategy for reducing complications, including one of the most common obstetrical complications in modern hospital settings, the c-section.
C1 COMPLETE HEART BLOCK AS A RARE MANIFESTATION OF GRANULOMATOSIS WITH POLYANGITIS: A CASE REPORT
Authors: Manai R , Cingolani M , Raineri C , Frea S , Bocchino P , De Ferrari G
Published: May 2023

A 42–year–old male with prior smoking habit presented at our emergency department after atraumatic syncope preceded by severe pain in the left lower limb. One month prior to presentation, due to persistence of nonproductive cough he underwent a chest computed tomography (CT), which showed 2 pulmonary nodules with hypercaptation at PET performed later (figure 1). The 12–lead electrocardiogram showed sinus rhythm with complete atrioventricular block and ventricular escape rhythm at 40 bpm (figura 1). Ecofast revealed a mildly impaired left ventricular systolic function (left ventricular ejection fraction [LVEF] 45%) with basal septal hypokinesis. Laboratory assessment showed leukocytosis (marked neutrophilia and eosinophilia), thrombocytosis anemia, elevated C–reactive protein (193 mg/dl), troponin I (18483 ng/L), NTproBNP (14627 ng/l) and creatinine (2.27 mg/dL) levels. The patient was transported to the catheterization laboratory for temporary pacemaker insertion and coronary angiography, which depicted distal occlusion of the first septal branch (Figure 2A), the first diagonal branch (Figure 2B) and the obtuse marginal branch (Figure 2C). After the procedure due to persistent ischemia of the left lower limb, several unsuccessful procedures to restore limb vascularization by means of locoregional thrombolysis and percutaneous angioplasty were attempted, but a leg amputation above the knee was eventually performed after few days. Neoplastic markers, blood cultures and urine cultures resulted negative, urine sediment examination showed cylinders, leucocytes and microhematuria. A brain/facial bones CT scan was performed, showing left maxillary sinusitis (figure 1). A rheumatologic screening was also performed, showing high titer of cANCA(125 UI/ml) hinting at a systemic vasculitis. The histopathological results of the amputated limb depicted marked necrotizing vasculitis with extensive involvement of small–medium caliber and larger caliber arterial vessels (figure 2). Based on these clinical and laboratory findings, a diagnosis of granulomatosis with polyangiitis (GPA) was made. The patients was treated with ev methylprednisolone and rituximab. After the induction therapy, chest CT scan showed a marked reduction of the size of the pulmonary nodule (Figure 3); renal function progressively improved and physiological atrioventricular conduction being restored