bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid-Solid coupling analysis of PTFE impeller in hydraulic turbines for sewage resource utilization
Authors: Wang Shenghui , Kou Jiawen , Luo Xianwu , Xiao Yexiang , Wang Chengpeng , Li Jiacheng
Published: October 2024

Hydraulic turbines, vital energy-saving devices, convert pressure energy from liquid fluids into mechanical energy. As wastewater resource utilization and zero discharge industries proliferate, relevant research is of great interest. In order to design a suitable medium and low pressure hydraulic turbine for industrial water treatment, we conducted a study analyzing the stress and strain characteristics of a PTFE turbine impeller by means of bi-directional fluid-structure coupling numerical simulation. Our findings suggest that the impeller’s maximum equivalent stress and maximum deformation fall within acceptable material limits, with stress concentration at the blade-cover plate interface. The blade experiences maximum deformation at its midpoint due to high liquid pressure on the volute periphery. Fluid solid coupling reduces the maximum equivalent stress of the impeller by about 1.65MPa and the maximum deformation of the blade by about 0.05mm. The equivalent stress at the sampling point fluctuates periodically, with a significant change in stress amplitude at the sampling point of the cover plate on one side of the support surface, increasing susceptibility to fatigue damage.
Capacitor State Monitoring of MMC Photovoltaic Grid Connected Inverter Based on Capacitance Voltage Difference
Authors: Guo Xiaoxuan , Sun Huijie , Zhou Milu
Published: October 2024

Due to the high degree of modularity and high energy transmission efficiency, MMC is widely used in the field of photovoltaic grid connection. This paper focuses on the abnormal fluctuations of capacitor voltage caused by capacitor aging in MMC submodule, and comes up with a capacitance monitoring method based on the voltage fluctuation difference of submodule capacitors. The validity of the raised method is validated through simulation and experiments.
A video speed measurement method for UAV targeting ground targets based on kalman filtering
Authors: Wu Yuxin , Zhang Zhilong
Published: October 2024

Measuring the velocity information of moving targets, as an application scenario for drone target velocity measurement, is an important focus in the process of drone intelligence reconnaissance. To improve the speed and accuracy of unmanned aerial vehicles (UAVs) in locating and measuring moving targets, a reliable target localization and velocity model based on UAV reconnaissance video frames and Kalman filtering is proposed. This algorithm model can complete the localization and velocity measurement tasks of moving targets under complex conditions without the need to obtain ranging information from drones. To verify the algorithm, the Monte Carlo simulation method was used for simulation experiments. The experimental results show that the error of this velocity measurement algorithm can meet the accuracy requirements of unmanned aerial vehicles for ground-moving targets.
Orientation method based on lunar hour angle
Authors: Wang Zhihui , Ding Xiaoqiu , Wang Fangcao , Xu Shunfu
Published: October 2024

Astronomical orientation is a crucial technique for obtaining high-precision azimuths. However, at night, this often relies on the North Star, which can be challenging to locate and identify. An orientation method is proposed based on the lunar hour angle as an alternative. By applying theories from astronomy and geodesy, we conduct an in-depth study of the key points and calculation steps for using a theodolite to measure the moon. By observing the moon’s edge and center and combining this with the observer’s geographic location and observation time, we calculate the lunar hour angle to determine the true north azimuth. To improve computational efficiency, an application has been developed to assist with observation and data processing. Practical applications and tests have validated the feasibility and effectiveness of this lunar hour angle-based orientation method. This method addresses the limitations of traditional North Star orientation, offering an efficient and convenient approach to orientation.
APMP Pilot Study on High Transmittance Haze
Authors: Liu Wen-Chun , Koo Annette , Molloy Ellie , Wu Houping , Leecharoen Rojana , Zhang Jing , Liu Yuanjie , Suryani Dini , Yu Hsueh-Ling
Published: October 2024

This article presents the results of the Asia Pacific Metrology Programme (APMP) pilot comparison on high transmittance haze (TH), specifically TH >40 %. Various methods, including ASTM D1003, ISO 14782, the double beam method, and the double compensation method were employed. The results revealed that ASTM D1003 is still influenced by failure to compensate for sphere throughput, even in high TH artefacts. In contrast, the other methods exhibit good consistency, as expected. This article also analyses the total transmittance (TT) and diffuse transmittance (DT) obtained using the double compensation method, theoretically capable of determining accurate TT, DT, and TH, discussing the possibility of inconsistency in the reflectance between the sphere wall and the white plate affecting the agreement.
Characterisation of an LED-based integrating sphere source for detection of changes of AERONET Europe radiometers
Authors: Schwind K.M. , Nevas S. , Sperfeld P. , Pape S.
Published: October 2024

Within the framework of the EMPIR project 19ENV04 MAPP “Metrology for aerosol optical properties” an LED-based source was built for monitoring responsivity changes of Cimel filter radiometers from the AERONET Europe network. The developed LED device was flanged to integrating spheres to fill the field of view of the radiometers. Here we present the characterisation results of the LED-based integrating sphere source. The spectra of the radiant flux leaving a BaSO4-based integrating sphere showed positive wavelength dependent drift, which had not been reported in literature yet and did not appear by using incandescent lamps with the integrating spheres. This report shows approaches to reduce such drifts and an alternative using a PTFE-based integrating sphere, which was also tested for stability, reproducibility and homogeneity.
Innovative design of hole-carrying materials utilizing spiro-OMeTAD for halide hybrid perovskite solar cells
Authors: Yang Li , Zhao Liqian , Cai Liyun , Miao Jinniu , Qu Yandong , Guo Huiying , Yang Mingming , Du Peng
Published: October 2024

During the enhancement of photovoltaic conversion efficiency of perovskite cells, the study of hole transporting materials that match them is crucial. This work uses quantum mechanical calculation methods to systematically study 40 spiro [fluorene-9,9’-xanthene] (SFX) and spirobixanthene (SBX) spiro-core structure molecules designed based on spiro-OMeTAD as research objects. It systematically studies the effects of heteroatoms, methoxy and diphenylamine substitutions at different positions on the geometric conformation, molecular orbitals and energy levels, molecular reorganization energy, and UV-visible absorption spectra of all designed molecules. Based on the above research, the objective of this research is to furnish theoretical guidance for the design and development of hole transporting materials that can match various new types of perovskite materials.
Effect of different heat inputs on the microstructure and mechanical properties of the laser welded joint of CLF-1 steel
Authors: Shi Haicheng , Zhang Guoyu , Cao Dongxu , Li Wuhong , Xu Guojian
Published: October 2024

In this study, we examined the effects of various heat inputs on the microstructure and mechanical properties of the laser-welded joints of CLF-1 low-activation ferritic/martensitic steel medium-thick plates, which are used in the Test Blanket Module (TBM). The results indicate that under four different welding heat inputs (2727 J/cm, 3000 J/cm, 3563 J/cm, and 4500 J/cm), the weld microstructure is primarily composed of a large amount of lath martensite and a small amount of δ-Fe. As the heat input increases, the average width of lath martensite in the weld microstructure progressively increases, while the average volume fraction and width size of δ-Fe experience a significant increase. When the heat input surpasses 3563 J/cm, δ-Fe exhibits a dense aggregation. The tensile properties of the joints created under different heat inputs are superior to those of the base material. At the lowest heat input, the maximum impact toughness of the weld reaches 40 J.
Mechanical and electrical properties of two-dimensional BN doped with carbon group elements: first-principles calculations
Authors: Liu Heng , Xing Mengjiang , Fan Qingyang
Published: October 2024

Research of low-dimensional nanomaterials provides a direction for solving the problems of energy and environmental pollution. In this work, the regulation mechanism of doping carbon group elements X (X = C, Si, Ge, Pb, Sn) on mechanical and electrical properties of 2D monolayer BN are investigated by first-principles calculations. Two doping sites were selected, replace B atoms (B15N16X) or N atoms (B16N15X). Lower relative enthalpies and the elastic constants, which conforming to the mechanical stability standard, fully prove the stability of the doping system. Compared with B15N16X, B16N15X has larger structural distortion, smaller elastic constants and modulus, and is more inclined to ductility. With the increase of atomic radius, the deformation degree increases and the elastic parameters decrease. C-doped by replacing B atoms improves the elastic mechanical properties of monolayer BN. Sn-doped and Pb-doped modulate the monolayer BN into ductility. More importantly, all doped configurations exhibit magnetism. The indirect band gap of the undoped system can also be modulated into a direct band gap, B15N16C, B16N15Si and B16N15Ge all have direct band gaps in the spin-down direction. Asymmetric impurity energy levels DOS further verify the magnetism of the reference system.
Simultaneous detection of carbendazim and pendimethalin residues using a compact Raman spectrometer
Authors: Zhang Peng , Feng Zheng , Du Liangguang , Pan Weifan , Younus Junaid , Guo Xiaowei , Yang Xue
Published: October 2024

Surface-enhanced Raman spectroscopy (SERS) exhibits significant latent capacity in the prompt and accurate detection of minute concentrations of pesticides. In this study, carbendazim and pendimethalin were simultaneously detected within tobacco foliage by utilizing a PS@Ag composite substrate coupled with a compact Raman spectrometer. The detection limits for carbendazim is 0.1 mg/kg, and for pendimethalin, it is 5 mg/kg. The recovery rates for carbendazim within tobacco foliage ranged from 85.2% to 112.12%. And the recovery rates for pendimethalin ranged from 90.38% to 113.42%. The combination of the PS@Ag composite substrate in conjunction with a Raman spectrometer provides a highly effective means for the concurrent identification of pesticides in tobacco foliage.
Research on residual stress control in polycarbonate molding based on orthogonal analysis
Authors: Deng Zhaohu , Huang Jian
Published: October 2024

Residual internal stress is a primary factor affecting the performance and quality of transparent food containers formed by polycarbonate injection molding. Adjusting the injection molding process parameters stands out as the most effective means to control residual internal stress. This study employs numerical simulation to analyze the influence of injection molding process parameters on material internal stress during the polymer injection molding process, providing a reference for optimizing molding process parameters. Initially, through an analysis of the mechanism of internal stress formation, it is determined that the internal stress of beverage containers is mainly composed of cooling internal stress. Consequently, a mathematical model based on thermo-viscoelastic constitutive relations is selected to numerically simulate and calculate the formation of cooling internal stress during the injection molding process of PC materials. Numerical simulation results are obtained accordingly. Building upon this, orthogonal experiments are conducted based on the analysis data from numerical simulation, and through experimental comparison, the consistency between numerical simulation results and experimental results is validated. Finally, combining the results of experiments with numerical simulation, it is concluded that melt temperature is the primary factor influencing molding internal stress, followed by mold temperature and holding pressure, with injection speed being the least influential factor on residual stress.
Analysis of green energy-saving retrofit for air-conditioning system in UHVDC converter stations
Authors: Wang Hui , Li Chenxi , MA Shiwen , Yin Xiwei , Yu Mingduo , Lu Mengxue
Published: October 2024

The air-conditioning system in ultra-high-voltage direct current (UHVDC) converter stations uses hydrofluorocarbons (HFCs) as refrigerants currently, which pose a certain environmental hazard. Moreover, the cooling system of the converter valves contains a great deal of low-grade thermal energy, with waste heat being directly discharged into the air, resulting in significant energy wastage and air pollution. In light of the functional characteristics and energy wastage situation of current converter station buildings, a green energy-saving retrofit scheme for the air-conditioning system in UHVDC converter stations is proposed. It adopts a transcritical CO2 cycle system for building cooling and introduces an ejector into the system to improve its performance. Simultaneously, the heat pump technology is used to elevate the grade of waste heat from the converter valves, which is then utilized for heating in the control building. Simulation results demonstrate that this scheme is effective in enhancing ecological and environmental benefits while promoting green development of the converter station.
IEC104 protocol-based substation data upload IoT cloud platform implementation
Authors: Yang Chao , Chen Deji , Hu Hongyuan
Published: October 2024

The Industrial Internet of Things (IoT) has been developing rapidly under the background of Internet technology, and the most crucial part of its realization is the unified collection and access of heterogeneous data from multiple sources across networks and regions. For the access of substation system data, this paper designs a scheme to read data from IEC 60870-5-104 protocol and upload the data to IOT cloud platform by converting the data to data format supported by Kafka protocol, solving the problem of incompatibility between communication protocols, obtaining data from 104 secondary stations by connecting to them, parsing and processing the data in different formats, and converting the data to JSON format by processing and sending it to the IOT cloud platform. The data is converted into JSON format through processing and sent to the Kafka server, and the cloud platform obtains its data by subscribing to the corresponding topics. This approach makes substation data access more convenient, and efficiently and effectively saves the cost of hardware gateway, solves the incompatibility and interoperability between the underlying equipment access protocol and the cloud platform communication protocol, and builds a bridge for the remote transmission of the underlying equipment data of the Industrial Internet of Things.
Efficiency evaluation of electricity demand prediction models in lower-income countries: a case study of panama
Authors: Dong Youliang , Yan Changshun
Published: October 2024

Electricity plays a crucial role in the development of countries, serving as the foundation for the functioning of modern societies and as a key indicator of a nation’s level of modernization and overall strength. Predicting a country’s electricity demand provides valuable insights into the evolving patterns of electrical energy provision and usage and helps to improve the flexibility of the energy distribution network. In addition, it provides early warnings and decision support for governments, businesses, and individuals about future electricity consumption. This plays a pivotal function in optimizing power distribution, adjusting the proportion of power generation sources, and ensuring a continuous and secure electricity supply. This paper uses the example of electricity demand in Panama and uses the LSTM model and Prophet model to compare their predictions for electricity demand in lower-income countries, with the aim of improving accuracy. Furthermore, it introduces a data set representing the electricity demand of higher-income countries, using the United Kingdom as a representative, to compare the forecast results between the two countries. The results indicate that within the Panama data set, the Prophet model exhibits better accuracy than the LSTM model. On the contrary, in the data set representing higher-income countries with the United Kingdom as a representative, the LSTM model outperforms the Prophet model. This leads to the conclusion that the selection of a predictive model is specific to each country, influenced by factors such as development status, geographic location, policies, energy markets, and more. A specific model may not be universally applicable due to these unique conditions, requiring tailored-modeling approaches for precise and efficient allocation and scheduling of electricity resources. This approach ensures the improvement of residents’ living standards and quality of life while meeting the typical demands of a country’s economic and social development.
Evaluation of power system instability probability considering output randomness of grid-connected converter
Authors: Wang Liqiang , Liu Hongqing , Wang Qi , Cong Yu , Zheng Xiuxian
Published: October 2024

In recent years, there has been a notable increase in the installed capacity of new energy sources. Nevertheless, the random nature of the output power of G-CCs may potentially result in power system instability. This paper presents a closed-loop interconnection model comprising a G-CC as a feedback subsystem and a VSC-HVDC system as a feedforward subsystem. The instability condition of the closed-loop system is derived from the open-loop mode resonance theory. Subsequently, a mathematical model is developed to represent the random output of the G-CC. This approach allows the probability of open-loop mode resonant instability of the power system to be evaluated, as well as the risk of sub-synchronous resonant instability caused by the output randomness of the G-CC. Finally, validation is performed by building a simulation example system and a time-domain simulation system in MATLAB.
Large-signal stability analysis of an islanded DC microgrid with constant power loads based on mixed potential function
Authors: Zhang Shaojie , Wen Sufang , Wang Shunli
Published: October 2024

In DC microgrids, power electronic converters are widely used to connect loads and renewable energy sources to generate different voltages. These loads operate as constant power loads (CPL) within a closed control loop. When voltage fluctuates, these loads display negative impedance characteristics, potentially leading to system instability. Therefore, the analysis of the impact of CPL on DC microgrids during large disturbances is crucial. This paper employs mixed potential theory to study the large disturbance stability of DC microgrids under CPL. Deriving the stability criterion for the system under significant perturbations reveals the impact of load types and control parameters on system stability and provides a detailed analysis of how specific system parameters affect stability. Consequently, the stability criterion can ensure the system’s stability under large disturbances without the need for repeated calculations and simulations. Simulation results verify the correctness of this stability criterion.
Numerical investigation of the effective mechanical properties of architected structures: a comparative study of flexural stiffness, homogenization, and elastic anisotropy
Authors: García-Gutiérrez Magali E , Giraldo Betancur Astrid L , Cuan-Urquizo Enrique , Alvarado-Orozco Juan M , González-Hernández Jesús
Published: October 2024

The mechanical behavior of architected structures is influenced by various parameters, including the topology of their unit cells. This anisotropic nature requires the determination of the mechanical properties under different loading scenarios. This study employs numerical investigation to characterize the influence of topology on the mechanical properties of eight architected structures, focusing on effective elastic properties and anisotropic elastic behavior. The analyzed topologies encompass four based on struts (lattices) and four based on triply periodic minimal surfaces (TPMS), comprising Sheet and Network phases. Initially, beams composed of architected structures are subjected to flexure, with Euler–Bernoulli and Tymoshenko’s theories utilized in a first numerical approach to determine their effective properties. Subsequently, a numerical homogenization method along with the Voigt-Reuss-Hill scheme is employed in a second approach. A more substantial influence of topology on the effective properties is observed in low relative densities. The study revealed that for a relative density of 10%, the appropriate selection of the topology increases the stiffness of a structure by up to ∼126%. The EBT approach underestimated the stiffness by up to ∼26% due to neglecting the impact of shear on beam deflection. The tensorial anisotropy index revealed up to ∼27% higher anisotropy compared to the Zener index. These findings provide a valuable numerical tool for the comparison and selection of architected structures suitable for diverse applications.
Multi-channel machine learning based nonlocal kinetic energy density functional for semiconductors
Authors: Sun Liang , Chen Mohan
Published: October 2024

The recently proposed machine learning-based physically-constrained nonlocal (MPN) kinetic energy density functional (KEDF) can be used for simple metals and their alloys (Sun and Chen 2024 Phys. Rev. B 109 115135). However, the MPN KEDF does not perform well for semiconductors. Here we propose a multi-channel MPN (CPN) KEDF, which extends the MPN KEDF to semiconductors by integrating information collected from multiple channels, with each channel featuring a specific length scale in real space. The CPN KEDF is systematically tested on silicon and binary semiconductors. We find that the multi-channel design for KEDF is beneficial for machine-learning-based models in capturing the characteristics of semiconductors, particularly in handling covalent bonds. In particular, the CPN5 KEDF, which utilizes five channels, demonstrates excellent accuracy across all tested systems. These results offer a new path for generating KEDFs for semiconductors.
The Armed Debtor
Authors: Jones Corredera Edward
Published: October 2024

This chapter studies the structuring role of debates over colonial and war debts in the construction of Argentina. The United Provinces, constituted as independent and sovereign states, drew on principles of the law of nations to undermine Buenos Aires’ pursuit of domination over the region. The failure to unite the two sides led to the fragmentation of Argentina into two federations, the Unitarian League and the Federalist League. This division prompted debates over who ought to pay the debts incurred during the revolution. When France blockaded the port of Buenos Aires over unpaid claims, exiled thinkers sought to harness foreign interest in the region to topple Juan Manuel de Rosas. This outlook on debt and intervention informed the mid-nineteenth-century constitutional and diplomatic efforts of Juan Bautista Alberdi. Alberdi sought to resolve dilemmas that had emerged from the lack of resolution regarding war debts and the foreign loans before Argentina’s internal divisions led to his demise. During some of the toughest years of his life, he received a letter from Carlos Calvo. This letter triggered an intellectual exchange between the two jurists which led Alberdi to condemn international law as a threat to Latin America.
China
Authors: Prontera Andrea
Published: October 2024

This chapter analyses the Chinese green foreign energy policy and green power strategy. First, the chapter explains the shift in China’s energy policy from traditional energy security concerns, which have not disappeared, to technological dominance. This process has unfolded in parallel with the unexpected rise of China in several sectors that are key to the current energy transition, from manufacturing to critical minerals. Next, the chapter focuses on the structuring of the Chinese green energy state and explains how it has influenced the country’s green foreign engagements. A special focus is placed on the green components of the Belt and Road Initiative and on recent innovations introduced under Xi Jinping. Finally, the chapter discusses the greening of the Chinese global strategy as renewables and low-carbon technology are increasingly embedded in Beijing’s wider approach to extending its influence within the current international system.
Clinical utility of EBV DNA testing of blood in immunocompetent and immunocompromised patients: A single-center experience
Authors: Gupta Simran , Turbett Sarah E , Klontz Erik , Kotton Camille N
Published: October 2024

Objectives

Epstein-Barr virus (EBV) causes different clinical presentations in immunocompetent and immunocompromised persons, and thus indications for testing vary between these populations. We reviewed our institution’s EBV DNA testing across these populations to understand its clinical utility and appropriateness.

Methods

We conducted a retrospective chart review of adult patients with positive EBV nucleic acid amplification (NAAT) testing from November 2022 to 2023. We recorded demographics, indications for testing, EBV-related diagnosis, laboratory results, and whether testing influenced patient treatment.

Results

Of 3560 EBV NAAT tests, 187 (5.3%) were positive, representing 124 unique adult patients (51 immunocompetent and 73 immunocompromised). Reactivation of EBV was the most common diagnosis in both populations, followed by acute EBV infection in the immunocompetent and non-posttransplant lymphoproliferative disorder malignancies in the immunocompromised. In immunocompromised patients, positive tests led to treatment changes more frequently than in immunocompetent patients (27.4% vs 11.7%, P = .06). Testing affected clinical management in 0% to 2% of cases when sent for sepsis/shock and nonspecific viral syndromes compared to 37% to 49% of cases when sent for posttransplant and malignancy screening/monitoring.

Discussion

EBV NAAT testing infrequently influenced clinical management in immunocompetent individuals but had a notable impact in immunocompromised patients, particularly those undergoing posttransplant or malignancy screening. This underscores the need for targeted testing to optimize resource utilization and cost-effectiveness.
How does lexical coverage affect the processing of L2 texts?
Authors: Pellicer-Sánchez Ana , Webb Stuart , Wang Andi
Published: October 2024

Lexical coverage, i.e. the extent to which words in a text are known, is considered an important predictor of reading comprehension, with studies suggesting 98% lexical coverage leads to adequate comprehension. However, no studies to date have examined how the various lexical coverage percentages suggested in the literature are reflected by the cognitive effort involved in processing text and the attention that is devoted to the unknown vocabulary. This study used eye-tracking to examine how lexical coverage affects the processing of text (global measures) and unknown vocabulary (word-level measures), as well as the relationship between processing time on unknown vocabulary and learning. Advanced L2 learners of English read a text in one of four lexical coverage conditions (90%, 95%, 98%, 100%) while their eye movements were recorded. Knowledge of unknown pseudowords in the texts was assessed via an immediate, meaning recall post-test. Results showed that only one of the three global measures examined showed a processing advantage for the 98% condition, reflected by longer saccades and less effortful reading than the 90% and 95% conditions. Crucially, lexical coverage did not have a significant impact on the amount of attention spent on unknown vocabulary. Processing times were found to significantly predict vocabulary gains.
Constructing the dynamic transcriptional regulatory networks to identify phenotype-specific transcription regulators
Authors: Guo Yang , Xiao Zhiqiang
Published: October 2024

The transcriptional regulatory network (TRN) is a graph framework that helps understand the complex transcriptional regulation mechanisms in the transcription process. Identifying the phenotype-specific transcription regulators is vital to reveal the functional roles of transcription elements in associating the specific phenotypes. Although many methods have been developed towards detecting the phenotype-specific transcription elements based on the static TRN in the past decade, most of them are not satisfactory for elucidating the phenotype-related functional roles of transcription regulators in multiple levels, as the dynamic characteristics of transcription regulators are usually ignored in static models. In this study, we introduce a novel framework called DTGN to identify the phenotype-specific transcription factors (TFs) and pathways by constructing dynamic TRNs. We first design a graph autoencoder model to integrate the phenotype-oriented time-series gene expression data and static TRN to learn the temporal representations of genes. Then, based on the learned temporal representations of genes, we develop a statistical method to construct a series of dynamic TRNs associated with the development of specific phenotypes. Finally, we identify the phenotype-specific TFs and pathways from the constructed dynamic TRNs. Results from multiple phenotypic datasets show that the proposed DTGN framework outperforms most existing methods in identifying phenotype-specific TFs and pathways. Our framework offers a new approach to exploring the functional roles of transcription regulators that associate with specific phenotypes in a dynamic model.
Modified throughput ninhydrin method for the qualitative assessment of dietary protein absorption in pig plasma
Authors: Pierzynowska Kateryna , Zaworski Kamil , Wychowański Piotr , Donaldson Janine , Woliński Jarosław , Borowitz Drucy , Gallotto Robert , Pierzynowski Stefan
Published: October 2024

Protein maldigestion and malabsorption lead to malnutrition and are a feature of exocrine pancreatic insufficiency (EPI). Although it is the current standard, measurement of nitrogen in stool to assess protease activity is indirect. Up to 80% of hydrolysed proteins appear in blood in the form of peptides, so we developed a method to measure peptide-derived amino acids in plasma as a relevant measure of proteolysis, verified its accuracy, precision, and linearity, and validated it in a porcine model. We modified a ninhydrin method. Large proteins were eliminated from plasma with 10 kDa-cut-off centrifugal filters. Free and total amino acids were measured in permeate before and after its hydrolysis. Peptide-derived amino acids were quantified by subtracting free amino acids from total amino acids. We verified the method in vitro and by comparing results in healthy and EPI pigs. The accuracy of the analysis was close to 100%, with excellent precision (mean relative standard deviation for low, medium, and high amino acid levels = 0.88%) and with stringent linearity (r2 = 0.986, %RE = 5.23). The high-throughput ninhydrin method detected levels of peptide-derived amino acids in vivo with maximal changes seen approximately 2 hours postprandially in young pigs. The AUC and Cmax were significantly higher in healthy compared to EPI pigs (P = .0026 and P = .0037, respectively). The high-throughput ninhydrin method is a sensitive, reliable, and practical method for the estimation of dietary peptide-derived amino acids. This assay endpoint could serve as a direct biomarker of protein digestion and absorption.
Shared parameter modeling of longitudinal data allowing for possibly informative visiting process and terminal event
Authors: Thomadakis Christos , Meligkotsidou Loukia , Pantazis Nikos , Touloumi Giota
Published: October 2024

Joint modeling of longitudinal and time-to-event data, particularly through shared parameter models (SPMs), is a common approach for handling longitudinal marker data with an informative terminal event. A critical but often neglected assumption in this context is that the visiting/observation process is noninformative, depending solely on past marker values and visit times. When this assumption fails, the visiting process becomes informative, resulting potentially to biased SPM estimates. Existing methods generally rely on a conditional independence assumption, positing that the marker model, visiting process, and time-to-event model are independent given shared or correlated random effects. Moreover, they are typically built on an intensity-based visiting process using calendar time. This study introduces a unified approach for jointly modeling a normally distributed marker, the visiting process, and time-to-event data in the form of competing risks. Our model conditions on the history of observed marker values, prior visit times, the marker’s random effects, and possibly a frailty term independent of the random effects. While our approach aligns with the shared-parameter framework, it does not presume conditional independence between the processes. Additionally, the visiting process can be defined on either a gap time scale, via proportional hazard models, or a calendar time scale, via proportional intensity models. Through extensive simulation studies, we assess the performance of our proposed methodology. We demonstrate that disregarding an informative visiting process can yield significantly biased marker estimates. However, misspecification of the visiting process can also lead to biased estimates. The gap time formulation exhibits greater robustness compared to the intensity-based model when the visiting process is misspecified. In general, enriching the visiting process with prior visit history enhances performance. We further apply our methodology to real longitudinal data from HIV, where visit frequency varies substantially among individuals.
The prognostic value of epicardial and pericoronary adipose tissue in heart failure with preserved ejection fraction using coronary computed tomography angiography
Authors: Lin Shuangxiang , Liu Chenjia , Wang Shuyue , Ding Xingfa , Wu Jiaxing , Wang Xinhong , Jianzhong Sun
Published: October 2024

Objectives

To assess the prognostic significance of epicardial adipose tissue volume (EATv) and pericoronary adipose tissue attenuation (PCATa) in patients with heart failure with preserved ejection fraction (HFpEF).

Methods

This retrospective study was based on HFpEF and controls who underwent coronary CT angiography (CCTA) screening to rule out coronary disease. Comparisons of EATv and PCATa were made between HFpEF patients and a control group, using statistical analyses including Kaplan-Meier and Cox regression to assess prognostic significance.

Results

A total of 224 patients were retrospectively analysed. The EATv was 56.1 ± 11.9 cm3 and PCATa in the right coronary artery (PCATa-RCA) was −74.7 HU ± 3.82 in HFpEF patients, which increased significantly compared with controls. Among them, 112 HFpEF patients (mean age: 71.9 ± 8.5 years; 40% male) were followed up for a median of 27 ± 0.6 months (range 2-47 months). EATv and PCATa-RCA were predictive of outcome with an optimal threshold of 56.29 cm3 and −71.17 HU, respectively. In Kaplan-Meier analysis, the high EATv and PCATa-RCA attenuation had significantly higher rates of composite outcomes (log-rank test, all P < .01). EATv and PCATa-RCA were independently predictive of outcome following adjustment for confounding variables (EATv: hazard ratio [HR] 1.03; 95% CI (1.01-1.06); P < .01, PCTAa-RCA: HR 1.44; 95% CI 1.27-1.62; P < .001)).

Conclusions

Increased EATv and PCATa-RCA are associated with worse clinical outcomes in HFpEF patients.

Advances in knowledge

This study highlights the potential of CCTA-derived adipose tissue metrics as novel, non-invasive biomarkers for risk stratification in HFpEF.
Novel risk loci in LGI1-antibody encephalitis: genome-wide association study discovery and validation cohorts
Authors: Binks Sophie N M , Elliott Katherine S , Muñiz-Castrillo Sergio , Gilbert Edmund , Kawasaki de Araujo Tânia , Harper Andrew R , Brown Andrew C , Chong Amanda Y , Band Gavin , Peris Sempere Vicente , Pinto Anne-Laurie , Costantino Felicie , Rayner N William , Mentzer Alexander J , Delanty Norman , Rogemond Veronique , Picard Géraldine , Handel Adam E , Melzer Nico , Titulaer Maarten J , Lee Soon-Tae , Leypoldt Frank , Kuhlenbaeumer Gregor , Honnorat Jérôme , Mignot Emmanuel , Cavelleri Gianpiero L , Knight Julian C , Irani Sarosh R
Published: October 2024

Encephalitis with antibodies to leucine-rich glioma-inactivated 1 (LGI1-Ab-E) is a common form of autoimmune encephalitis, presenting with seizures and neuropsychiatric changes, predominantly in older males. More than 90% of patients carry the human leukocyte antigen (HLA) class II allele, HLA-DRB1*07:01. However, this is also present in 25% of healthy controls. Therefore, we hypothesized the presence of additional genetic predispositions.

In this genome-wide association study and meta-analysis, we studied a discovery cohort of 131 French LGI1-Ab-E and a validation cohort of 126 American, British and Irish LGI1-Ab-E patients, ancestry-matched to 2613 and 2538 European controls, respectively.

Outside the known major HLA signal, we found two single nucleotide polymorphisms at genome-wide significance (P < 5 × 10−8), implicating PTPRD, a protein tyrosine phosphatase, and LINC00670, a non-protein coding RNA gene. Meta-analysis defined four additional non-HLA loci, including the protein coding COBL gene. Polygenic risk scores with and without HLA variants proposed a contribution of non-HLA loci. In silico network analyses suggested LGI1 and PTPRD-mediated interactions via the established receptors of LGI1, ADAM22 and ADAM23.

Our results identify new genetic loci in LGI1-Ab-E. These findings present opportunities for mechanistic studies and offer potential markers of susceptibility, prognostics and therapeutic responses.
Epidemiological, clinical and histological characteristics of melanoma in young adults: a 30-year retrospective study (1993–2022)
Authors: Rodríguez-Sánchez Belén , Rodríguez-Lomba Enrique , Avilés-Izquierdo José Antonio
Published: October 2024

Background

Melanoma in young adults significantly impacts the survival of individuals in this age group. There are few studies that analyse melanoma characteristics in young patients.

Objectives

To describe the epidemiological, clinical and histological characteristics of melanoma in young adults and the temporal trends in these characteristics in recent decades.

Methods

A retrospective observational study was conducted, involving 399 patients with melanoma aged 18–44 years, over a 30-year period (1993–2022). Patients were divided into two groups based on their date of diagnosis (period 1, 1993–2007; period 2, 2008–2022).

Results

Age at diagnosis was higher in period 2 than period 1 (34.3 vs. 36.7 years; P < 0.001). Over time, there was a reduction in median thickness (1.0 vs. 0.68 mm; P = 0.01), a rise in melanomas located on the head and neck [n = 15/230 (6.5%) vs. n = 25/169 (14.8%)] and extremities [n = 97/230 (42.2%) vs. n = 76/169 (45.0%)], and a decrease in melanomas on the trunk [n = 118/230 (51.3%) vs. n = 68/169 (40.2%); P = 0.009]. There was also an increase in lentigo maligna [n = 5/230 (2.3%) vs. n = 5/169 (3.0%)] and superficial spreading melanomas [n = 176/230 (76.5%) vs. n = 142/169 (84.0%)], along with a reduction in nodular types [n = 37/230 (16.1%) vs. n = 10/169 (5.9%); P = 0.01]. In comparison with men, women had a higher prevalence of limb melanoma [n = 125/222 (56.3%) vs. n = 48/177 (27.1%); P < 0.001] and family history of melanoma [n = 26/222 (11.7%) vs. n = 9/177 (5.1%); P = 0.02], thinner melanomas (0.69 vs. 1.10 mm; P = 0.001) and a better prognosis [n = 32/222 (14.4%) vs. n = 37/169 (20.9%) deaths; P = 0.01].

Conclusions

Melanoma diagnoses in young adults are occurring at progressively advanced ages, with a rise in melanomas situated on the head and extremities and in histological types linked to prolonged sun exposure. Strategies such as minimizing sun exposure from a young age and encouraging self-examination could lead to improved survival rates.
3D transoesophageal echocardiographic assessment of acute reverse remodelling of the tricuspid annulus after transcatheter edge-to-edge repair
Authors: Cammalleri Valeria , Antonelli Giorgio , De Luca Valeria Maria , Piscione Mariagrazia , Carpenito Myriam , Gaudio Dario , Nusca Annunziata , Cocco Nino , Mega Simona , Grigioni Francesco , Ussia Gian Paolo
Published: October 2024

Aims

Our study aims to evaluate the acute remodelling of the tricuspid valve annulus immediately after the tricuspid transcatheter edge-to-edge repair (T-TEER) by using intraprocedural transoesophageal 3D echocardiography.

Methods and results

We prospectively enrolled 62 consecutive symptomatic patients with at least severe tricuspid regurgitation (TR), who underwent T-TEER with the TriClip System between March 2021 and June 2024. The following parameters were assessed using a multiplanar reconstruction analysis performed off-line using a 3D data set: septal–lateral (SL) and antero–posterior (AP) annulus diameters; annulus area; annulus perimeter; and eccentricity index. The acute procedural success was achieved in 85.5%. We observed an acute reduction in SL (from a median of 43 to 38 mm, P < 0.0001), AP (from a median of 46 to 45 mm, P < 0.0001), area (from a median of 17.9 to 15.95 cm2, P < 0.0001), perimeter (from a median of 145.5 to 137 mm, P < 0.0001), and eccentricity index (from 0.92 to 0.87, P < 0.0001). The tricuspid valve (TV) annulus was progressively larger in patients with higher residual TR. Analysis of the subgroups according to procedural success showed an acute inverse remodelling of the TV annulus independent of the acute procedural success.

Conclusion

The TV geometry necessitates the use of 3D echocardiography for accurate assessment of annular remodelling post T-TEER. The reduction in TR grade and TV annulus dimensions begins immediately after TriClip implantation. Concurrently, the baseline TV geometry influences the procedural results.
Comparison between invasive cardiac output and left ventricular assist device flow parameter
Authors: Segev Amitai , Copeland Viana , Sokolski Mateusz , Azaria Sivan , Morgan Avi , Maor Elad , Jura Maksym , Wilk Mateusz , Przybylski Roman , Freimark Dov , Tal-Ben Ishay Rotem , Regev Udi , Fardman Alexander , Grupper Avishay
Published: October 2024

OBJECTIVES

To evaluate the correlation between left ventricular assist device flow parameter and invasive cardiac output measurements.

METHODS

We retrospectively evaluated right heart catheterization examinations performed in left ventricular assist device patients from 2 tertiary medical centres. We evaluated the correlation between cardiac output measurement methods (indirect Fick and thermodilution) and pump flow parameter using linear regression, and the agreement was graphically displayed using Bland–Altman plot technique. Clinical, echocardiographic, pump and haemodynamic parameters were compared between patients with and without discordance, defined as at least a 20% difference between measurements.

RESULTS

The study population consisted of 102 patients [median age 58 (51–64), 86% males, 17 ± 12 months post left ventricular assist device implantation] with a total of 544 measurements compared. Discordance between measurements was present in 102 of 226 (45%) comparisons between indirect Fick and pump flow and in 72 of 161 (48%) between thermodilution and pump flow. A comparison of indirect Fick and left ventricular assist device exhibited a statistical correlation of R = 0.751, and that of thermodilution and left ventricular assist device of R = 0.789. Parameters associated with the presence of discordance between cardiac output measurements included a higher rate of aortic valve opening, lower indirect Fick and higher thermodilution cardiac output. After excluding the lowest tertile of indirect Fick cardiac output values, the correlation between measurements improved (thermodilution: R = 0.879 and indirect Fick: R = 0.843, P < 0.001).

CONCLUSIONS

The current left ventricular assist device flow parameter provides an estimation of cardiac output that correlates well with indirect Fick and exhibits the strongest correlation with thermodilution. This correlation was stronger after excluding lower cardiac output values.
Clinical risk prediction, coronary computed tomography angiography, and cardiovascular events in new-onset chest pain: the PROMISE and SCOT-HEART trials
Authors: Rasmussen Laust Dupont , Schmidt Samuel Emil , Knuuti Juhani , Vrints Christiaan , Bøttcher Morten , Foldyna Borek , Williams Michelle C , Newby David E , Douglas Pamela S , Winther Simon
Published: October 2024

Background and Aims

Whether index testing using coronary computed tomography angiography (CTA) improves outcomes in stable chest pain is debated. The risk factor weighted clinical likelihood (RF-CL) model provides likelihood estimation of obstructive coronary artery disease. This study investigated the prognostic effect of coronary CTA vs. usual care by RF-CL estimates.

Methods

Large-scale studies randomized patients (N = 13 748) with stable chest pain to coronary CTA as part of the initial work-up in addition to or instead of usual care including functional testing. Patients were stratified according to RF-CL estimates [RF-CL: very-low (≤5%), low (>5%–15%), and moderate/high (>15%)]. The primary endpoint was myocardial infarction or death at 3 years.

Results

The primary endpoint occurred in 313 (2.3%) patients. Event rates were similar in patients allocated to coronary CTA vs. usual care [risk difference (RD) 0.3%, hazard ratio (HR) 0.84 (95% CI 0.67–1.05)]. Overall, 33%, 44%, and 23% patients had very-low, low, and moderate/high RF-CL. Risk was similar in patients with very low and moderate/high RF-CL allocated to coronary CTA vs. usual care [very low: RD 0.3%, HR 1.27 (0.74–2.16); moderate/high: RD 0.5%, HR 0.88 (0.63–1.23)]. Conversely, patients with low RF-CL undergoing coronary CTA had lower event rates [RD 0.7%, HR 0.67 (95% CI 0.47–0.97)]. The number needed to test using coronary CTA to prevent one event within 3 years was 143.

Conclusions

Despite an overall good prognosis, low RF-CL patients have reduced risk of myocardial infarction or death when allocated to coronary CTA vs. usual care. Risk is similar in patients with very-low and moderate/high likelihood.