bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced 3D-DXA insights into bone density changes in hyperparathyroidism
Authors: Guerra Francesco Saverio , Palladino Nicola , Winzenrieth Renaud , Guglielmi Giuseppe
Published: August 2024

Objectives

Primary hyperparathyroidism (PHPT) is a disorder marked by chronic parathyroid hormone hypersecretion, which affects bone turnover and remodelling processes. With a loss of bone density and an increase in bone porosity, the cortical compartment is most severely impacted. The study's goal is to assess PHPT's effects on the volumetric bone mineral density (vBMD) of the femur's trabecular compartment as well as the vBMD and thickness of the cortical bone.

Methods

This is a retrospective case–control study, valuating age, biochemical doses, anthropometric measurements, and bone measurements. Between 2011 and 2016, 74 Caucasian Italian women and men with PHPT were sought out. Biochemical analyses were added to bone mineral density (BMD) values found in the lumbar spine and femoral neck. Proximal femur parameters such as cortical and trabecular volumetric (v) BMD, cortical thickness (CTh) and surface (s) BMD were analyzed by 3D-DXA software (3D-SHAPER Medical, Spain).

Results

The findings showed a negative correlation between PHPT patients and controls, which was equally affecting the cortical and trabecular compartments. This correlation was especially evident in the areal BMD (aBMD) and vBMD measurements. Nonetheless, no appreciable correlation was found between the cortical level and the thickness of the cortical bone.

Conclusions

Parathormone (PHT) levels had an adverse effect on the cortical, trabecular volumetric density in this investigation, as was expected. Cortical thickness, however, is unaffected significantly. The literature and these findings are consistent.
The level of dental fear and anxiety is higher in children with both severe Molar-Incisor Hypomineralisation and active dental caries lesions compared to children without these conditions
Authors: Rodríguez Ó. A. , Laverde M. , Rojas-Gualdrón D. F. , Cárdenas J. M. , Mejía J. D. , de Farias A. L. , Santos-Pinto L. , Restrepo M.
Published: August 2024

Purpose

To assess levels of dental fear and anxiety (DFA) in children with and without Molar-Incisor Hypomineralisation (MIH) and dental caries lesions.

Methods

In this cross-sectional observational study, 159 children between 8 and 12 years of age were included. For the evaluation of DFA, children responded to the validated version of the Children’s Fear Survey Schedule-Dental Subscale. MIH was assessed using the MIH Index. To evaluate the activity of dental caries lesions and dental caries experience, the Nyvad criterion and the dmft/DMFT index were used, respectively. Dental hypersensitivity was evaluated using air stimulation and a Visual Analogue Scale. The association between MIH and dental caries with DFA was assessed using the generalised linear model with Poisson family, identity link function and robust variance estimation. The significance level was set at 5%.

Results

The mean DFA score was 28.3 (SD = 13.4) with scores ranging from 15 to 64. Amongst children presenting both MIH and dental caries, the perception of DFA was notably higher compared to those with either MIH or dental caries alone. The activity of caries lesion in patients with MIH also influenced DFA levels (diff: 18.6; 95% CI: 12.0–25.2; p < 0.001). Dental caries experience in the primary dentition also demonstrated statistical significance concerning DFA (95% CI: 0.8–13.3; p value = 0.027).

Conclusion

Children with MIH exhibit higher levels of DFA than children without MIH. The experience of dental caries and the activity of caries lesions significantly influence the perception of DFA in children with MIH.
Malocclusion in deciduous dentition: a cross-sectional study in a Portuguese preschool population
Authors: Esperancinha C. , Mendes S. , Bernardo M.
Published: August 2024

Purpose

To determine the prevalence of malocclusion in Portuguese preschool children, to characterise occlusion in the deciduous dentition, and to study the relationship between malocclusion, sex, and age.

Methods

This cross-sectional study included 3–6 years old children, from 25 randomly selected kindergartens from the Lisbon district. Data were collected through an oral examination. Malocclusion was defined as the presence of any type of occlusion anomaly (anterior crossbite, edge-to-edge, increased overjet, open bite, deep overbite, posterior crossbite, scissor bite), spacing anomaly (crowding), or dentition anomaly (supernumerary teeth, agenesis, malformations). Canine class, terminal plane of the deciduous second molars and type of Baume arch were also recorded. Statistical analysis included descriptive and chi-squared test (α = 0.05).

Results

The sample included 426 children with a global prevalence of malocclusion of 60.6%. Occlusion anomalies were the most prevalent (59.2%), the most frequent being deep overbite (27%), increased overjet (22.1%) and posterior crossbite (14.1%). Crowding had a prevalence of 1.6% and agenesis of 1.4%. Class I canine (57.3%), straight second molar terminal plane (60.1%) and type I Baume arch (53.3%) were the most common. The mean overjet was 2.6 mm (sd = 2.1) and the mean overbite was 2.2 mm (sd = 2.1). Age was associated with the presence of occlusion anomalies (p = 0.03), and increased overjet prevalence was found to be higher in girls (p = 0.03).

Conclusions

The prevalence of malocclusion was high, with occlusion anomalies being the most prevalent. It is important to identify modifiable risk factors associated with malocclusion to prevent this condition in both the deciduous and permanent dentitions.
Modeling static friction behavior of elastic–plastic spherical adhesive microcontact in full-stick condition
Authors: Xiang Guo , Goltsberg Roman , Etsion Izhak
Published: August 2024

The static friction behavior of an elastic–plastic spherical adhesive microcontact between a rigid flat and a deformable sphere under combined normal and tangential loading is studied by the finite element method (FEM). The contact between the sphere and the rigid flat is assumed to be full-stick, and the sliding inception is related to a loss of tangential stiffness. The intermolecular force between the rigid flat and the sphere is assessed by the Lennard–Jones (LJ) potential, which is applied to the sphere and the rigid flat by a user subroutine. The evolution of the adhesive force with tangential displacement in the full-stick condition is revealed. The results indicate that the increasing effect of adhesive energy on the static friction coefficient gradually diminishes with an increase in the adhesive energy and the external normal load. Finally, based on an extensive parametric study, an empirical dimensionless expression is obtained to predict the static friction coefficient of the spherical adhesive microcontact considering the intermolecular force.
Fabrication of PMMA nanocomposite biomaterials reinforced by cellulose nanocrystals extracted from rice husk for dental applications
Authors: Fouly Ahmed , Daoush Walid M. , Elqady Hesham I. , Abdo Hany S.
Published: August 2024

The primary objective of global studies is to develop the properties and durability of polymers for various applications. When it comes to dental disability, denture base materials must have sufficient mechanical and tribological performance in order to withstand the forces experienced in the mouth. This work aims to investigate the effects of the addition of low content of cellulose nanocrystals (CNC) on the mechanical and tribological performance of the polymethyl methacrylate (PMMA) nanocomposites. Different weight percent of CNC (0, 0.2, 0.4, 0.6, and 0.8 wt%) were added to the PMMA matrix followed by ball milling to evenly distribute the nanoparticles reinforced phase in the matrix phase. The findings emphasize the significant impact of CNC integration on the performance of PMMA nanocomposites. By increasing the content of the CNC nanoparticles, the mechanical properties of PMMA were improved. In addition, the tribological outcomes demonstrated a significant reduction in the friction coefficient besides an enhancement in the wear resistance as the weight percentage of nanoparticles increased. The surface of the worn samples was investigated by utilizing SEM to identify the wear mechanisms corresponding to the different compositions. In addition, a finite elment model (FEM) was developed to ascertain the thickness of the worn layer and the generated stressed on the surfaces of the nanocomposite throughout the friction process.
Introducing a Synchronous Workshop Feedback Model for OSCE Development in an International Education Partnership
Authors: Gondhalekar Anjali , Arfeen Zakia , Mohsen Lamiaa , Shabrawy Marwa el , Mokhtar Hend , Rashid Mohammed Ahmed
Published: August 2024

University College London (UCL) and Newgiza University (NGU) have been in an academic collaboration since 2016. We describe the introduction of a real-time feedback model for OSCE assessments within this partnership. We developed a workshop for faculty members at UCL and NGU to co-develop OSCE stations for use in final year summative exams at NGU. Structured discussions in small groups about content and logistics of each proposed station enabled the teams to jointly finalise the assessment blueprint and station list. A synchronous workshop model has since become a popular method to improve assessment quality and co-develop assessments in international settings.
Hydrogen Plasma for Low-Carbon Extractive Metallurgy: Oxides Reduction, Metals Refining, and Wastes Processing
Authors: Satritama B. , Cooper C. , Fellicia D. , Pownceby M. I. , Palanisamy S. , Ang A. , Mukhlis R. Z. , Pye J. , Rahbari A. , Brooks G. A. , Rhamdhani M. A.
Published: August 2024

Carbon-rich sources, such as coal and carbon monoxide gas, have been extensively used in the metal industry as the reducing agent of metal oxides and as the energy source for metal production. Consequently, the extractive metal sector contributes to approximately 9.5% of global greenhouse gas emissions. Hydrogen gas offers a promising alternative to using carbon in metallurgical processes as an eco-friendly reductant and energy provider that produces water vapor as a by-product. However, molecular hydrogen has some barriers to implementation. These primarily concern the thermodynamics and kinetics of metal oxide reduction. To address these issues, researchers have explored the use of hydrogen plasma, which is generated by applying high energy to molecular hydrogen to produce atomic, ionic, and excited hydrogen species. Hydrogen plasma has thermodynamic and kinetic advantages over molecular hydrogen and carbon-based reductants since it exhibits a lower standard Gibbs free energy of reaction for H2O formation and a lower activation energy. Hydrogen plasma is also a versatile reductant as it is proven on a laboratory scale to produce metal in fewer steps, process a wide range of oxides feed and feed sizes, and be used to refine metals. There are, however, some limitations to using hydrogen plasma in extractive metallurgy. These include the cost of electricity, potential back reactions or reoxidation, and industrial scale-up challenges such as heat utilization or heat loss minimization. This study undertakes a comprehensive review of prior research on the use of hydrogen plasma for metal oxides reduction and reviewing state-of-the-art techniques for its use in extractive metallurgy applications. An overview of hydrogen plasma utilization for producing and refining several metals from primary or secondary feed materials, the many types of plasma reactors, and the commonly used parameters for each metal production process are also presented. Prospects and potential feasibility of the hydrogen plasma route are also discussed.

Graphical Abstract
Vibration Control of Smooth and Discontinuous Oscillator via Negative Derivative Feedback
Authors: Amer Y. A. , Abdullah R. E. , khaled O. M. , Mahdy A. M. S. , El-Salam M. N. Abd
Published: August 2024

Purpose

The desired of this study is to decrease the vibrations of smooth and discontinuous (SD) oscillator using negative derivative feedback (NDF) controller.

Methods

The system has been analyzed approximately employing the method of multiple scales to derive the solution up to the first approximation.

Conclusion

The impact of negative derivative feedback (NDF) controller on smooth and discontinuous (SD) oscillator has been investigated under the condition of a simultaneous resonance $$(\Omega=\omega_1, \omega_1=\omega_2)$$

(
Ω
=

ω
1

,

ω
1

=

ω
2

)

.The influence of various parameters has been elucidated numerically using MATLAB. The results demonstrate a strong agreement between the approximate solution and the numerical solution.
Evolution of a solitary wave: optical soliton, soliton molecule and soliton crystal
Authors: Singh Prashant , Senthilnathan K.
Published: August 2024

This review embarks on a captivating odyssey of tracing the birth of light from the Big Bang to its intricate interplay with materials. It delves into the fundamental truth that nonlinearity is ubiquitous, and induces fascinating spatiotemporal structures, chaos, and complexity in the medium. After a brief exploration of waves and the effect of nonlinearity in diverse domains, the review article focuses on the field of photonics. This comprehensive review dives into the captivating physics of solitons. This study explores the formation of solitons in optical fibers due to specific nonlinear effects within the material, such as the Kerr effect, the fundamental behaviour of solitons in integrable models, diverse interactions, and the formation of intricate soliton molecules, soliton complexes, and soliton crystals within the dissipative optical systems. We analyse key research on optical solitons and highlight the control of optical solitons for advancements in communication systems, signal processing, optical computing, quantum technologies, etc. Through a meticulous research survey, we find that there is a limited understanding of weak soliton interactions. Further, more theoretical models to be investigated for exploring anisotropy of material and optomechanical interplay. Bridging these gaps will definitely propel future soliton research.
Pluralist economics in an era of polycrisis
Authors: Schulz Jan , Hötte Kerstin , Mayerhoffer Daniel M.
Published: August 2024

Interacting crises at economic, societal, ecological, and geopolitical levels reveal the fragility of connected global systems and give momentum to pluralist economic thinking as a suitable approach to address the complexity and uncertainty of today’s economy. This special issue (SI) explores how young economists, educated in this era, study economic phenomena through pluralist lenses. Due to the structure of interdependent crises and inherent uncertainty, pluralism of values, theory and methods may benefit the academic and policy debate on solutions for today’s political, social, and scientific challenges. Applied to the crisis context, this SI shows a range of research methods and interdisciplinary approaches, reflecting a shift in economic thinking that embraces the complexity, limited predictability, and fragility of socioeconomic systems. The SI aims to promote a dialogue across schools of economic thought to enhance our understanding and contribute to robust and inclusive policy.
Signals, Systems, and Signal Processing
Authors: Vaidyanathan P. P.
Published: August 2024

This innovative introduction to the foundations of signals, systems, and transforms emphasises discrete-time concepts, smoothing the transition towards more advanced study in Digital Signal Processing (DSP). A digital-first approach, introducing discrete-time concepts from the beginning, equips students with a firm theoretical foundation in signals and systems, while emphasising topics fundamental to understanding DSP. Continuous-time approaches are introduced in later chapters, providing students with a well-rounded understanding that maintains a strong digital emphasis. Real-world applications, including music signals, signal denoising systems, and digital communication systems, are introduced to encourage student motivation. Early introduction of core concepts in digital filtering, DFT and FFT provide a frictionless transition through to more advanced study. Over 325 end-of-chapter problems, and over 50 computational problems using Matlab. Accompanied online by solutions and code for instructors, this rigorous textbook is ideal for undergraduate students in electrical engineering studying an introductory course in signals, systems, and signal processing.
Obsidian Tool Function and Maya Lithic Economy at Terminal Classic Pook's Hill, Belize: Subsistence, Domestic Activities, and Craft Production
Authors: Stemp W. James , Helmke Christophe , Braswell Geoffrey E. , Awe Jaime J.
Published: August 2024

The typological, technological, and use-wear analyses of obsidian artifacts from Terminal Classic Pook's Hill (AD 830–950+) provide opportunities to better reconstruct socioeconomic activities in this plazuela group, including long-distance trade, tool production, subsistence practices, domestic tasks, and the organization of craft production. Based on visual sourcing, most of the obsidian originated from highland Guatemala, specifically El Chayal. The majority of obsidian artifacts were prismatic blades, although both casual and bipolar reduction of blade cores and the recycling of blades from earlier occupations occurred at the site. Use-wear analysis reveals that obsidian tools were mainly used for subsistence and domestic household activities; however, the concentrations of tools with specific wear patterns (bone, ceramic, plants, and shell) at some locations in the plazuela provide evidence for local craft production among the population. Further support for craft production is provided by comparable use-wear on chert/chalcedony tools from these same locations. The products of low-level craft production were used within Pook's Hill itself and may have been distributed to neighboring communities within the Roaring Creek and Upper Belize River Valleys. Despite the sociopolitical and socioeconomic disruptions to lifeways that accompanied the Terminal Classic period, the Pook's Hill Maya seem to have experienced minimal upheaval in their daily lives and continued local low-level craft production. However, one important change in the Terminal Classic appears to be the increased difficulty in obtaining obsidian at Pook's Hill and the growing need for tool recycling and raw material conservation.
Implications of Rock Art Aesthetics in Olmec Sculpture
Authors: Mollenhauer Jillian
Published: August 2024

The development of freestanding stone sculpture by the Olmec people of Mesoamerica's Gulf lowlands has long been considered one of the defining artistic achievements of the Formative period. However, by the Middle Formative period the production of freestanding sculpture was often eclipsed by the contemporaneous creation of rock art outside the Gulf lowlands. In this article I argue that Gulf Olmec sculptors and audiences occasionally co-opted the aesthetic and ritual treatments of rock art at topographic shrines to construct and reinforce the sacred geographies of primary site cores. In so doing, Olmec elites converted the ideological power of the wild and the animate earth into a form of political capital.
The Constitutionally Illogical Whig Presidency
Authors: Cash Jordan T.
Published: August 2024

This article examines the Whig Party’s conception of the presidency and argues that it failed to take hold because the idea of an executive which is subordinate or deferential to the legislative branch is fundamentally at odds with the Constitution. To show this, I assess the four presidents from the Whig Party: William Henry Harrison, John Tyler, Zachary Taylor, and Millard Fillmore. Each of these presidents entered office supporting the Whigs’ ideological vision of legislative supremacy and weak executive power, yet quickly abandoned that vision once in office. I contend that this demonstrates the constitutional logic of the presidency and the way it shapes the officeholder’s perspective, orienting presidents toward a robust understanding of executive power. In short, presidents do not act like Whigs because the Constitution directs them not to.
The Roman siege system of Masada: a 3D computerized analysis of a conflict landscape
Authors: Ashkenazi Hai , Ze'evi-Berger Omer , Gross Boaz , Stiebel Guy D.
Published: August 2024

The 1st-c. CE Roman siege system of Masada exhibits a high degree of preservation due to its remote location and the arid climate. However, unlike the thoroughly excavated Masada fortress, the siege system has not received due attention. This article is part of a research project aimed at advancing our understanding of the conflict landscape around Masada using contemporary archaeological methods. Following a comprehensive surface survey and photogrammetric 3D modelling, we show that the circumvallation wall stood to a height of 2–2.5 m and served several functions – as an obstacle, a means of psychological warfare, and a platform from which to mount counterattacks. Based on our measurements and workload estimations, we argue that the construction of the siege wall and the camps around Masada occurred fairly quickly.
Exploring stigma, shame, and safety behaviours in social anxiety and paranoia amongst people diagnosed with schizophrenia
Authors: Aunjitsakul Warut , Jongbowonwiwat Kreuwan , Lambe Sinead , Freeman Daniel , McLeod Hamish J. , Gumley Andrew
Published: August 2024

Background:

Social anxiety and paranoia are connected by a shared suspicion framework. Based on cognitive-behavioural approaches, there is evidence for treating social anxiety and psychosis. However, mechanisms underlying the relationship between social anxiety and paranoia remain unclear.

Aims:

To investigate mediators between social anxiety and paranoia in schizophrenia such as negative social appraisals (i.e. stigma or shame; Hypothesis 1), and safety behaviours (i.e. anxious avoidance or in situ safety behaviours; Hypothesis 2).

Method:

A cross-sectional study was conducted among Asian out-patients with schizophrenia (January–April 2020). Data on social anxiety, paranoia, depression, shame, stigma, anxious avoidance, and in situ behaviours were collected. Associations between social anxiety and paranoia were investigated using linear regressions. Mediation analysis via 10,000 bias-corrected bootstrap samples with 95% confidence intervals (CI) was used to test the indirect effects (ab) of mediators.

Results:

Participants (n=113, 59.3% male) with a mean age of 44.2 years were recruited. A linear relationship between social anxiety and paranoia was found. In multiple mediation analyses (co-varying for depression), stigma and shame (Hypothesis 1) did not show any significant indirect effects with ab=.004 (95%CI=–.013, .031) and –.003 (–.023, .017), respectively, whereas in situ behaviours (Hypothesis 2) showed a significant effect with ab=.110 (.038, .201) through the social anxiety–paranoia relationship.

Conclusions:

Social anxiety and paranoia are positively correlated. In situ safety behaviours fully mediated the social anxiety and paranoia relationship. Targeted interventions focusing on safety behaviours could help reduce paranoia in psychosis. Symptom severity should be measured to help characterise the participants’ characteristics.
Unraveling massive star and binary physics in the nearby low-Z galaxy SMC as a proxy for high-redshift galaxies
Authors: Pauli Daniel
Published: August 2024

Low metallicity (Z) massive stars are among the main feedback agents in the early Universe and in present-day blue dwarf galaxies. The nearby star-forming SMC galaxy offers conditions which resemble those at redshift z∼2 i.e. where modern galaxies formed and star formation peaked. Here we present the recent results about the nature of the eclipsing O-type binary in the SMC, AzV 476, to gain insights on the properties of massive stars and binaries at earlier cosmic epochs. We find that the primary has surprisingly low mass while being much brighter and hotter than the secondary. To place the measured stellar properties in the evolutionary context we modeled the system and confirm that AzV 476 is a post-interaction binary with the primary already being core helium (He) burning, while still having a hydrogen-rich (H-rich) envelope. These results constrain massive binary evolutionary scenarios and guide the searches of stripped stars in low-Z environments.
Binarity in Massive Young Stellar Objects
Authors: Shenton Robert G. , Oudmaijer René D. , Lumsden Stuart L.
Published: August 2024

Most massive stars (up to 100%) are thought to be in binary systems. The multiplicity of massive stars seems to be intrinsically linked to their formation and evolution, and so Massive Young Stellar Objects are key in observing this early stage of star formation. We have surveyed hundreds of MYSOs across the Galaxy from the RMS catalogue, using UKIDSS and VVV point source data. Preliminary results show binary fractions of 44±3% for the UKIDSS sample and 32±3% for the VVV sample. In addition we use the K-band magnitudes as a proxy for the companion mass, and find a significant fraction of the detected companions have estimated mass ratios greater than 0.5, which suggests a deviation from the capture formation scenario.
Observations and modeling of two Type IIP supernovae in M61: similar yet so different
Authors: Teja Rishabh Singh , Anupama G. C. , Sahu D. K.
Published: August 2024

We present photometric and spectroscopic studies of two type IIP SNe (SN 2008in and SN 2020jfo), to infer their physical parameters. These SNe exploded in the same host galaxy, M 61 (NGC 4303), at different epochs. SN 2008in was a normal Type IIP event with plateau length of ∼ 100 d and MV= –16.4 ± 0.4 mag, whereas SN 2020jfo was a short plateau (∼60 d) event with MV= –17.4 ± 0.4 mag. Hydrodynamical modeling on these events using the MESA+STELLA framework suggests that the progenitors of both the objects were Red Super Giant (RSG) stars with mass , but with different evolutionary history and environment.
Very Massive Stars: Near and Far
Authors: Martinet Sébastien , Meynet Georges , Ekström Sylvia , Georgy Cyril , Haemmerlé Lionel , Nandal Devesh , Hirschi Raphael
Published: August 2024

In addition to being spectacular objects, very massive stars (VMS) are suspected to have a tremendous impact on their environment and on the whole cosmic evolution. The nucleosynthesis both during their advanced stages and their final explosion likely contribute greatly to the overall enrichment of the Universe. Their resulting Supernovae are candidates for the most superluminous events and their extreme conditions lead also to very important radiative and mechanical feedback effects, from local to cosmic scale. With the recent implementation of a new equation of state in the GENEC stellar evolution code, appropriate for describing the conditions in the central regions of very massive stars in the advanced phases, we present new results on VMS evolution from Population III to solar metallicity. We explore their evolution and final fate as potential (P)PISNe across the cosmic time. We compare our results to recent spectroscopic observations of VMS in the Large Magellanic Cloud (LMC). We also underline the important radiative feedback of Population III VMS during the reionization epoch and the chemical contribution of these stars at high metallicity, especially for short-lived radionuclei.
MUSE 3D spectroscopy of BA-type supergiants in NGC 300
Authors: González-Torà Gemma , Urbaneja Miguel A. , Przybilla Norbert , Dreizler Stefan , Roth Martin M. , Kamann Sebastian , Castro Norberto
Published: August 2024

We present the results obtained using spectroscopic data taken with the intermediate-resolution Multi Unit Spectroscopic Explorer (MUSE) of B and A-type supergiants and bright giants in the Sculptor Group galaxy NGC 300. For our analysis, a hybrid local thermodynamic equilibrium (LTE) line-blanketing+non-LTE method was used to improve the previously published results for the same data. In addition, we present some further applications of this work, which includes extending the flux-weighted gravity luminosity relationship (FGLR), a distance determination method for supergiants. This pioneering work opens up a new window to explore this relation, and also demonstrates the enormous potential of integral field spectroscopy (IFS) for extragalactic quantitative stellar studies.
Plaskett’s Star: a fundamental revision of the architecture of the system
Authors: Stacey E. , Wade G. A. , Grunhut J. H. , Folsom C. P. , Kochukhov O.
Published: August 2024

A century of study has characterized Plaskett’s Star (HD 47129) as an evolved, massive, short-period, equal mass O+O binary system. The discovery of a magnetic field in the broad-line component by Grunhut et al. (2013) renewed interest in the study of this system and led to its establishment as the most rapidly rotating magnetic O-type star. Grunhut et al. (2021) observed the circular polarization signatures of the magnetic star to exhibit no radial velocity variations while the narrow-line star demonstrates radial velocity variations consistent with the established orbital period. This has raised fundamental questions about the architecture of this system and the nature of the magnetic star which have led to a major shift in our understanding of HD 47129.
MAGIC Intensity Interferometer as a powerful tool to understand massive stars
Authors: Jiménez Martínez Irene , Acciari V. A. , Colombo E. , Cortina J. , Delgado C. , Díaz C. , Fink D. , Fiori M. , Guberman D. , Hassan T. , Lyard E. , Mangano S. , Mariotti M. , Martínez G. , Mirzoyan R. , Naletto G. , Njoh Ekoume T. , Produit N. , Polo M. , Rodríguez J. J. , Schweizer T. , Walter R. , Wunderlich C. , Zampieri L. ,   for the MAGIC collaboration
Published: August 2024

The Intensity Interferometry technique consists of measuring the spatial coherence (visibility) of an object via its intensity fluctuations over a sufficient range of telescope separations (baselines). This allows us to study the size, shape and morphology of stars with an unprecedented resolution. Cherenkov telescopes have a set of characteristics that coincidentally allow for Intensity Interferometry observations: very large reflective surfaces, sensitivity to individual photons, temporal resolution of nanoseconds and the fact that they come in groups of several telescopes. In the recent years, the MAGIC Collaboration has developed a deadtime-free Intensity Interferometry setup for its two 17 m diameter Cherenkov telescopes that includes a 4-channel GPU-based real-time correlator, 410–430 nm filters and new ways of splitting its primary mirrors into submirrors using Active Mirror Control (AMC). With this setup, MAGIC can operate as a long-baseline optical interferometer in the baseline range 40–90 m, which translates into angular resolutions of 0.5-1 mas. Additionally, thanks to its AMC, it can simultaneously measure the zero-baseline correlation or, by splitting into submirrors, access shorter baselines under 17 m in multiple u-v plane orientations. The best candidates to observe with this technique are relatively small and bright stars, in other words, massive stars (O, B and A types). We will present the science cases that are currently being proposed for this setup, as well as the prospects for the future of the system and technique, like the possibility of large-scale implementation with CTA.
Apsidal Motion in Massive Binaries: CPD-41° 7742, an Extreme Case?
Authors: Rosu S. , Rauw G. , Nazé Y. , Gosset E. , Sterken C.
Published: August 2024

We study the apsidal motion in close eccentric massive binaries. Measuring the rate of apsidal motion in such a system gives insight into the internal structure and evolutionary state of the stars. We focus on CPD-41° 7742, for which independent studies in the past showed large discrepancies in the longitude of periastron of the orbit, hinting at the presence of apsidal motion. We perform a consistent analysis of all observational data to solve this apparent discrepancy and report the first determination of apsidal motion in this system. This study confirms the need for enhanced mixing in the stellar evolution models of the primary star to reproduce the observational properties. This points towards larger convective cores than usually considered.
Metal-poor Wolf-Rayet star enriching the ISM by nitrogen in the galaxy NGC 4068
Authors: Yarovova Anastasiya , Egorov Oleg , Moiseev Alexei , Maryeva Olga
Published: August 2024

We discovered a nebula in the low-metallicity (Z=0.1 ) nearby ( Mpc) dwarf galaxy NGC 4068, which reveals broad Hα line profile and unusual emission line fluxes in its spectrum. The object also shows significant nitrogen overabundance, not typical for metal-poor environment. We assumed that the nebula could be ionized by an evolved massive star with , Wolf-Rayet or Blue Supergiant, and built models of the nebula using Cloudy and CMFGEN codes. Our models successfully reproduce the optical emission spectrum of the object, including the peculiar [SII]/[NII] ratio and the presence of the HeII λ4686 line.
PION: Simulating bow shocks and circumstellar nebulae around massive stars
Authors: Mackey Jonathan , Green Samuel , Moutzouri Maria , Haworth Thomas J. , Kavanagh Robert D. , Celeste Maggie , Brose Robert , Zargaryan Davit
Published: August 2024

Expanding nebulae are produced by mass loss from stars, especially during late stages of evolution. We describe the algorithms and methods implemented in the radiation-magnetohydrodynamics (MHD) code PION for highly scalable simulations using static mesh-refinement. We present results from 3D MHD simulations of bow shocks around runaway massive stars, and of the expansion of a fast wind from a Wolf-Rayet star into the slow wind from a previous red supergiant phase of evolution. PION is free software that can be downloaded from https://www.pion.ie/
Revisiting the Cygnus OB associations
Authors: Quintana Alexis L. , Wright Nicholas J.
Published: August 2024

We have studied the validity of the historical Cygnus OB associations and have found that many do not show the kinematic coherence expected for true OB associations. We have revisited these groups by photometrically identifying thousands of OB stars across the region with an SED fitting process which combines photometry, astrometry, spectral and evolutionary models. We applied a flexible clustering method and identified seven kinematically-coherent new OB associations. We observe a distinct correlation between position and velocity for two sets of these associations that suggests an expansion pattern. Tracing the motion of the stars back in the past we find that the sets were at their closest around 7.9 and 8.5 Myr ago. We discuss whether this expansion is a natural by-product of the commonly observed size - velocity dispersion relation of molecular clouds, or requires feedback to initiate the dispersal.
In-Situ Field Massive Star Formation in the Small Magellanic Cloud
Authors: Vargas-Salazar I. , Oey M. S. , Barnes J. R. , Chen X. , Castro N. , Kratter K. M. , Faerber T. A.
Published: August 2024

A fundamental question for theories of massive star formation is whether OB stars can form in isolation. We assess the contribution of any in-situ OB star formation by using 210 field OB stars in the Small Magellanic Cloud (SMC) from the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4). We search for tiny, sparse clusters around our target OB stars using cluster-finding algorithms. Employing statistical tests, we compare these observations with random-field data sets. We find that ∼5% of our target fields do show evidence of higher central stellar densities, implying the presence of small clusters. This frequency of small clusters is low and within errors, it is also consistent with the field OB population being composed entirely of runaway and walkaway stars. Assuming this small cluster fraction is real, it implies that some OB stars may form in highly isolated conditions. The low frequency could be caused by these clusters evaporating on a short timescale. However, another interpretation is that the low fraction of small clusters is observed because these form rarely, or not at all, implying a higher cluster lower-mass limit and generally consistent with a relationship between maximum stellar mass (mmax) and the cluster mass (Mcl).
Open questions in massive star research
Authors: Langer N.
Published: August 2024

In discussing open question in the field of massive stars, I consider their evolution from birth to death. After touching upon massive star formation, which may be bi-modal and not lead to a zero-age main sequence at the highest masses, I consider the consequences of massive stars being close to their Eddington limit. Then, when discussing the effects of a binary companion, I highlight the importance of massive Algols and contact binaries for understanding the consequences of mass transfer, and the role of binaries in forming Wolf-Rayet stars. Finally, a discussion on pair instability supernovae and of superluminous supernovae is provided.
ASSESSing evolved massive stars in NGC 6822 and IC 10
Authors: Munoz-Sanchez G. , Maravelias G. , Bonanos A. Z. , Tramper F. , de Wit S. , Yang M.
Published: August 2024

The role of mass loss from massive stars, especially episodic mass loss, is one of the outstanding open questions facing stellar evolution theory. Multiple lines of evidence are pointing to violent, episodic mass-loss events being responsible for removing a large part of the massive stellar envelope, especially in low-metallicity galaxies. The ERC ASSESS project aims to determine whether episodic mass loss is a dominant process in the evolution of the most massive stars by conducting the first extensive, multi-wavelength survey of evolved massive stars in the nearby Universe. The project hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We aim to investigate the properties of evolved targets in nearby galaxies and estimate the amount of ejected mass, which will constrain evolutionary models. In this work we present some of our first observational results from the galaxies NGC 6822 and IC 10 obtained with OSIRIS (GTC).
A SITELLE view of the Galactic Wolf-Rayet Nebulae NGC6888 and NGC2359
Authors: St-Louis N. , Dumontier C. , Ruest M. , Drissen L.
Published: August 2024

In this paper, we present a glimpse of our observations of two Wolf-Rayet (WR) nebulae, NGC2359 and NGC6888 obtained with the SITELLE imaging Fourier transform spectrograph. The data are of unprecedented spatial coverage and cover a broad wavelength range.
X-raying massive stars and their feedback near and far
Authors: Oskinova Lidia
Published: August 2024

Massive stars emit X-rays. Despite modest X-ray luminosities of single hot massive stars, the ongoing large observing campaigns combining X-ray and UV spectroscopy provide a tomographic view of stellar winds. It is now established that X-ray radiation is modulated with stellar rotation and shows the same period as discrete absorption components (DACs) in the UV resonance lines. The latter are associated with corotating interaction regions (CIRs) in stellar winds, therefore the mechanisms responsible for generation of X-rays and CIRs appear to be physically linked. Binary massive stars with accreting compact companions – high-mass X-ray binaries (HMXBs) – are routinely observed by modern X-ray observatories at Mpc distances. Joint observations in X-ray and UV allow to determine realistic properties of these systems. The brightest sources among HMXBs are ultraluminous X-ray sources (ULXs). Their powerful radiation is an important source of stellar feedback. HMXBs are the products of massive binary evolution and are typically found in the vicinity of young massive star clusters. The superstar clusters blow hot superbubbles which fill large areas in star-forming dwarf galaxies. Recent models show that X-ray emission from superbubbles is likely the dominant source of He ii ionization in metal-poor star-forming dwarf galaxies. To conclude, X-ray observations provide an important window for studying massive stars and their feedback near and far.
Clumping and X-rays in cool B-Supergiants
Authors: Bernini-Peron Matheus , Marcolino W. L. F. , Sander A. A. C.
Published: August 2024

B supergiants (BSGs) lie on the cool end of line-driven wind regime, such that the study of their atmospheres can help us to understand the physics of line-driven winds. So far key features of their spectra, especially in the UV region, could not be reproduced consistently with atmosphere models. This represents a significant gap in our knowledge of their physical properties and behavior, which is particularly striking for BSGs on the cool side of the Bi-Stability Jump (cooler than B1). To address this problem, we analysed a sample of Galactic cool BSGs, with sufficient UV and optical coverage. None of our targets are detected in X-rays with only upper limits existing for some of them.
Rapid Identification of Greigite in Lacustrine Sediments Using SIRM/χ and χARM: Insights From the Cuo E Core, Tibetan Plateau, China
Authors: Ding Shengchang , Dekkers Mark J. , Li Mingkun , Zhao Qi , Yan Yi , Zhu Zhaoyu
Published: August 2024

The Cuo E (CE) core contains the entire Quaternary stratigraphy of the CE Lake (31°24′–31°.32′ N, 91°28′–91°33′E, Tibetan Plateau, China). Here, we study the magnetic properties of 1,748 samples from the CE core, combined with scanning electron microscopy and X‐ray energy dispersive spectrometer analysis on selected samples. The main magnetic minerals appear to be magnetite and greigite. To further quantify the presence of greigite in CE core, 84 samples were analyzed using rock magnetism in more detail including: susceptibility (χ) versus temperature, coercivity component analysis of acquisition curves of the isothermal remanent magnetization (IRM), and principal component analysis of the first‐order reversal curve (FORC) diagrams. The greigite content and saturation IRM over susceptibility (SIRM/χ) appear to be exponentially related. SIRM/χ can be used as greigite concentration indicator. We also propose a rapid way to identify greigite in the CE core: When SIRM/χ increases and anhysteretic remanent susceptibility (χARM) increases only slowly, the sample contains greigite. Samples with SIRM/χ < 15 kA/m also follow this relation. This greigite detection method has a lower limit of detection than the traditionally used SIRM/χ parameter. It is also faster than FORC analysis and thus particularly suitable for analysis of large sample collections. Twenty greigite‐bearing layers were identified in the CE core using this method. The location of the Jaramillo subchron in the CE core is controversial in the currently available magnetostratigraphy, possibly related to the presence of greigite in this core interval.
Geodetic Matched Filter Slow Slip Event Detection Along the Northern Japan Subduction Zones
Authors: Marill Lou , Marsan David , Rousset Baptiste , Socquet Anne
Published: August 2024

We apply a template matching method on GNSS data for stations located in Honshu, Japan, to detect slow slip events associated with the subducting Philippine Sea and Pacific plates during the period from 1997 to 2020. A measure of the minimum detectable moment magnitude is proposed, from which we infer that the method could potentially detect SSEs as small as Mw 5.2 on the westernmost part of the Philippine Sea plate and Mw 6 on the Pacific plate below Honshu eastern coastline. We find 12 slow slip events on the Philippine Sea plate, among which eight are located on the known Boso slow slip event asperity and the four others are located offshore north‐east relative to the Boso SSEs, at the transition with the Pacific plate. We find 9 SSEs on the Pacific plate, mainly on the northern section, offshore Iwate prefecture. A clear gap with no SSEs coincides with the main asperity that broke during the 2011 Tohoku earthquake. Most event locations correlate with low locking areas. We do not find any clear temporal pattern apart from the regular occurrence of the largest Boso SSEs.
Assimilating Morning, Evening, and Nighttime Greenhouse Gas Observations in Atmospheric Inversions
Authors: Monteiro V. C. , Turnbull J. C. , Miles N. L. , Davis K. J. , Barkley Z. , Deng A.
Published: August 2024

Improved urban greenhouse gas (GHG) flux estimates are crucial for informing policy and mitigation efforts. Atmospheric inversion modeling (AIM) is a widely used technique combining atmospheric measurements of trace gas, meteorological modeling, and a prior emission map to infer fluxes. Traditionally, AIM relies on mid‐afternoon observations due to the well‐represented atmospheric boundary layer in meteorological models. However, confining flux assessment to daytime observations is problematic for the urban scale, where air masses typically move over a city in a few hours and AIM therefore cannot provide improved constraints on emissions over the full diurnal cycle. We hypothesized that there are atmospheric conditions beyond the mid‐afternoon under which meteorological models also perform well. We tested this hypothesis using tower‐based measurements of CO2 and CH4, wind speed observations, weather model outputs from INFLUX (Indianapolis Flux Experiment), and a prior emissions map. By categorizing trace gas vertical gradients according to wind speed classes and identifying when the meteorological model satisfactorily simulates boundary layer depth (BLD), we found that non‐afternoon observations can be assimilated when wind speed is >5 m/s. This condition resulted in small modeled BLD biases (<40%) when compared to calmer conditions (>100%). For Indianapolis, 37% of the GHG measurements meet this wind speed criterion, almost tripling the observations retained for AIM. Similar results are expected for windy cities like Auckland, Melbourne, and Boston, potentially allowing AIM to assimilate up to 60% of the total (24‐hr) observations. Incorporating these observations in AIMs should yield a more diurnally comprehensive evaluation of urban GHG emissions.