bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring and modulation of respiratory drive in patients with acute hypoxemic respiratory failure in spontaneous breathing
Authors: Mocellin Anna , Guidotti Federico , Rizzato Simone , Tacconi Matteo , Bruzzi Giulia , Messina Jacopo , Puggioni Daniele , Patsoura Athina , Fantini Riccardo , Tabbì Luca , Castaniere Ivana , Marchioni Alessandro , Clini Enrico , Tonelli Roberto
Published: August 2024

Non-invasive respiratory support, namely, non-invasive ventilation, continuous positive airway pressure, and high-flow nasal cannula, has been increasingly used worldwide to treat acute hypoxemic respiratory failure, giving the benefits of keeping spontaneous breathing preserved. In this scenario, monitoring and controlling respiratory drive could be helpful to avoid patient self-inflicted lung injury and promptly identify those patients that require an upgrade to invasive mechanical ventilation. In this review, we first describe the physiological components affecting respiratory drive to outline the risks associated with its hyperactivation. Further, we analyze and compare the leading strategies implemented for respiratory drive monitoring and discuss the sedative drugs and the non-pharmacological approaches used to modulate respiratory drive during non-invasive respiratory support. Refining the available techniques and rethinking our therapeutic and monitoring targets can help critical care physicians develop a personalized and minimally invasive approach.

Graphical abstract
Education as Liberation: Using Archaeology to Serve Modern Working Class Needs
Authors: Westmont V. Camille
Published: August 2024

The working classes have been overlooked as a population that could benefit from social-justice-oriented critical public archaeology approaches. The Anthracite Heritage Program sought to address this gap by targeting educational attainment among students in the historically working class, chronically underserved northeastern Pennsylvania region. Public archaeology initiatives to promote interest and knowledge about undergraduate education revealed that the archaeologists’ greatest contribution was our own (class-based) knowledge of the intricacies of university admissions, funding, and life in the United States. In this way, the project ended up serving underserved communities in the ways that they needed help the most: securing the knowledge to attain class mobility.
Identifying students with dyslexia: exploration of current assessment methods
Authors: Daniel Johny , Clucas Lauryn , Wang Hsuan-Hui
Published: August 2024

Early identification plays a crucial role in providing timely support to students with learning disabilities, such as dyslexia, in order to overcome their reading difficulties. However, there is significant variability in the methods used for identifying dyslexia. This study aimed to explore and understand the practices of dyslexia identification in the UK. A survey was conducted among 274 dyslexia professionals, including educational psychologists and dyslexia specialists, to investigate the types of assessments they employ, their approach to utilizing assessment data, their decision-making processes, and their conceptualization of dyslexia. Additionally, the study examined whether these professionals held any misconceptions or myths associated with dyslexia. Analysis of the survey data revealed substantial variability in how professionals conceptualize dyslexia, as well as variations in assessment methods. Furthermore, a significant proportion of the survey respondents subscribed to one or more misconceptions regarding dyslexia; the most common misconception identified among professionals was the belief that children with dyslexia read letters in reverse order. The findings highlight the need for standardized approaches to dyslexia identification and debunking prevailing misconceptions. The implications of these findings are discussed, emphasizing the importance of informed policy and practice in supporting students with dyslexia. Recommendations are provided to enhance consistency and accuracy in dyslexia identification, with the aim of facilitating early intervention and support for affected students.
Emigration of Juvenile Tarpon Megalops atlanticus from Ephemerally Connected Coastal Ponds
Authors: Bunting Matthew S. , Stevens Philip W. , Blewett David A. , Tuckett Quenton M. , Hill Jeffrey E. , Poulakis Gregg R. , Shea Colin P. , Saari Courtney R.
Published: August 2024

Worldwide, coastal wetlands are threatened by disrupted hydrology, urbanization, and sea-level rise. In southwest Florida, coastal wetlands include tidal creeks and coastal ponds, which are the primary habitats used by juvenile Tarpon, Megalops atlanticus, an important sport fish. Coastal ponds can occur near uplands and are ephemerally connected to the open estuary, creating conditions of variable dissolved oxygen and salinity. Juveniles can tolerate wide-ranging abiotic conditions, but little is known about how they egress from their remote nursery habitats, which often requires them to cross > 1 km of mangrove forest to reach the open estuary. The objective of this study was to (1) compare Tarpon body condition among ponds close to the open estuary versus those ponds farther away on the Cape Haze peninsula of Charlotte Harbor, Florida, and (2) using acoustic telemetry determine what factors contribute to Tarpon emigration from the ponds to open estuarine waters. We tested the hypothesis that distinct groups of Tarpon occur in isolated ponds, leading to variation in fish length and body condition, and that opportunities for emigration from these ponds hinge on high water events. No pond stood out as having Tarpon of low body condition. Factors contributing to increased probabilities of Tarpon emigration were low barometric pressure, high-water level, and Tarpon body length. Tarpon emigrated from ponds near tidal creeks during summer king tides, while tropical cyclone conditions were needed to allow for movement from ponds farther in the landscape. The juvenile Tarpon were later detected at the mouths of large rivers 30 km up-estuary. The characterizations of water levels and event criteria needed for successful Tarpon nurseries should aid in habitat conservation and the creation of Tarpon nursery habitat in restoration designs.
Importance of genetic clarification in cytopenia syndromes (childhood myelodysplastic syndrome forms)
Authors: Novak Wolfgang , Kroiss Doris , Karlhuber Susanne , Frohne Alexandra , Segarra-Roca Anna , Simonitsch-Klupp Ingrid , Boztug Heidrun , Engstler Gernot , Kager Leo , Boztug Kaan , Dworzak Michael
Published: August 2024

Childhood myelodysplastic syndrome (cMDS) is a rare clonal hematopoietic disorder characterized by peripheral cytopenia, with refractory cytopenia of childhood (RCC) being the most prevalent form. In children presenting with pancytopenia and significantly reduced bone marrow cellularity, RCC, severe aplastic anemia (SAA), and inherited bone marrow failure syndromes (IBMFS) are critical differential diagnoses, with accurate distinction being pivotal for effective treatment decisions. While histopathological analysis remains fundamental in differentiating these conditions, genetic and molecular testing are playing an increasingly important role. Reflecting this importance, two new classifications for cMDS were introduced in 2022: the WHO 5th edition and the International Consensus Classification (ICC). Both classifications have broadened the scope to include additional gene mutations, highlighting advances in understanding the genetic underpinnings of cMDS. However, significant differences in terminology persist: while the WHO 5th edition redefined RCC, replacing it with the term childhood MDS with low blasts (cMDS-LB), the ICC retained the RCC designation. This paper presents two cases that illustrate the current challenges in diagnosing and treating disorders in the spectrum of cMDS. One case describes a patient with germline GATA2 deficiency, highlighting the difficulties of distinguishing between SAA and cMDS in a timely manner. The other case underscores the importance of whole exome sequencing to differentiate between IBMFS and cMDS in the presence of a histomorphological RCC pattern.
Data Sovereignty in Inter-organizational Information Systems
Authors: Opriel Sebastian , Möller Frederik , Strobel Gero , Otto Boris
Published: August 2024

Car manufacturers and suppliers in the Automotive industry increasingly face the issue of optimization of highly complex supply chains that need to accommodate each customer's precise demands, requiring a vast array of parts and information to be available at the right place and at the right time. This involves data sharing between organizations, which is hindered by various issues, such as fear of data misappropriation by the data receiver or the involuntary disclosure of business secrets. The paper proposes design principles for a novel type of Inter-Organizational Information System, which addresses these challenges through the technical implementation of data sovereignty. The study reports on an Action Design Research study in the Automotive industry between a car manufacturer and a 1st-tier supplier. It contributes (a) design requirements, (b) design features, (c) an instantiation, and (d) design principles for this type of data sovereign inter-organizational information system.
Effect of Pistachio Shell Biochar and Organic Cow Manure Application on Plant Growth, Water Retention Capacity and Nutrient Stress Mitigation
Authors: Pradhan Snigdhendubala , Parthasarathy Prakash , Mackey Hamish R. , Al-Ansari Tareq , McKay Gordon
Published: August 2024

Sustainable crop production supports food security by mitigating water and nutrient stress from manures by excessively drained water. Cow manure is a good nutrient resource to enhance soil fertility and plant growth but requires a suitable amender to reduce the nutrients loss by leaching. Worldwide more than 20,400 metric tonnes of pistachios were consumed where roughly 30% of the weight of the nut is the shell which could be a good feedstock for biochar production. Therefore, this study was conducted to produce biochar from pistachio shell by pyrolysis process at three different temperatures 350 to 550 °C and based on various properties characterization, the biochar at 450 °C was amended with 0% (control), 2%, 4% and 8% to the cow manure for eggplant growth (Solanum melongena). Out of all fractions of biochar application, 2% biochar has virtuous performance to increase 5.63 ± 1.45 cm of plant height, 1.33 ± 4.79 cm leaf length and 1.90 ± 4.43 cm leaf width over the control. The leaf chlorophyl content and plant biomass were also significantly (p = 0.02) increased compared to the control. The lower fraction of biochar application showed almost similar water retention capacity with control (p > 0.11) due to the better plant growth. Based on the findings of this study, it is proposed that lower fraction of biochar application with manure is a constructive solution to improve soil quality, reduce nutrient loss and eggplant growth. Under the circular economy and frameworks of sustainability, pistachio shell biochar production has a high legislative attention on valorizing nutshell wastes.

Graphical Abstract
Body fluid multiomics in 3PM-guided ischemic stroke management: health risk assessment, targeted protection against health-to-disease transition, and cost-effective personalized approach are envisaged
Authors: Chen Ruofei , Wang Xiaoyan , Li Na , Golubnitschaja Olga , Zhan Xianquan
Published: August 2024

Because of its rapid progression and frequently poor prognosis, stroke is the third major cause of death in Europe and the first one in China. Many independent studies demonstrated sufficient space for prevention interventions in the primary care of ischemic stroke defined as the most cost-effective protection of vulnerable subpopulations against health-to-disease transition. Although several studies identified molecular patterns specific for IS in body fluids, none of these approaches has yet been incorporated into IS treatment guidelines. The advantages and disadvantages of individual body fluids are thoroughly analyzed throughout the paper. For example, multiomics based on a minimally invasive approach utilizing blood and its components is recommended for real-time monitoring, due to the particularly high level of dynamics of the blood as a body system. On the other hand, tear fluid as a more stable system is recommended for a non-invasive and patient-friendly holistic approach appropriate for health risk assessment and innovative screening programs in cost-effective IS management. This article details aspects essential to promote the practical implementation of highlighted achievements in 3PM-guided IS management.
Modeling fisheries and carbon sequestration ecosystem services under deep uncertainty in the ocean twilight zone
Authors: Oostdijk Maartje , Elsler Laura G. , Van Deelen Julie , Auping Willem L. , Kwakkel Jan , Schadeberg Amanda , Vastenhoud Berthe M. J. , Nedelciu Claudiu Eduard , Berzaghi Fabio , Prellezo Raul , Wisz Mary S.
Published: August 2024

Mesopelagic fishes are a vital component of the biological carbon pump and are, to date, largely unexploited. In recent years, there has been an increased interest in harvesting the mesopelagic zone to produce fish feed for aquaculture. However, great uncertainties exist in how the mesopelagic zone interacts with the climate and food webs, presenting a dilemma for policy. Here, we investigate the consequences of potential policies relating to mesopelagic harvest quotas with a dynamic social-ecological modeling approach, combining system dynamics and global sensitivity analyses informed by participatory modeling. Our analyses reveal that, in simulations of mesopelagic fishing scenarios, uncertainties about mesopelagic fish population dynamics have the most pronounced influence on potential outcomes. The analysis also shows that prioritizing the development of the fishing industry over environmental protection would lead to a significantly higher social cost of climate change to society. Given the large uncertainties and the potential large impacts on oceanic carbon sequestration, a precautionary approach to developing mesopelagic fisheries is warranted.
The role of traditional ecological knowledge, given the transformation of pastoralism in Central and Eastern Mongolia
Authors: Peter Sophie , Niess Sarah , Batjav Batbuyan , Dejid Nandintsetseg , Drees Lukas , Jäschke Yun , Kasymov Ulan , Damdindorj Sugar , Dorjoo Khishigdorj , Gonchigsumlaa Ganzorig , Matias Denise Margaret S. , Müller Thomas , Mehring Marion
Published: August 2024

Mongolian nomadic herders traditionally pass on ecological knowledge intergenerationally, mainly within families. However, little is known about how current societal transformation processes may impact the application and transfer of traditional ecological knowledge (TEK) amongst herders. Combining quantitative household survey data with qualitative interviews, we show that TEK is still widely applied amongst herders. Our data show that households living under conditions of greater societal transformation apply TEK more often in order to adapt to the situation than households under lower transformation pressure. High transformation pressure goes along with high human population and livestock density and thus competition for good pastureland. In addition, our results show that intragenerational knowledge transfer between families is gaining more importance nowadays. For Mongolia, we recommend facilitating access to and strengthening the exchange of TEK to prepare herders for the future due to the high level of uncertainty accompanying societal transformations.
Microwave Photonic Systems for Demodulation of Optical Fiber Interference Signals
Authors: Chen Yuru , Lei Xiaohua , Liu Xianming , Zhang Peng
Published: August 2024

Fiber optic sensors have been gradually used in aerospace, petrochemical, electronic power, civil engineering, and biomedical fields because of their many advantages such as the anti-electromagnetic interference, corrosion resistance, light weight, small size, high accuracy, and easy reuse. In recent years, sensing and demodulation technologies based on microwave photonics have attracted widespread attention. Optical fiber sensing combined with microwave photonics has higher sensitivity and flexibility, which is important for the demodulation of interferometric signals. This article introduces and analyzes the principle, structure, and performance of the demodulation technology of fiber optic interferometric signals based on microwave photonics from the perspective of system structures, such as filters, oscillators, and interferometers, and discusses the future research and development directions.
Effect of environmental factors on modal identification of a hydroelectric dam’s hollow-gravity concrete block
Authors: Ardila-Ardila Yeny V. , Gómez-Araújo Iván D. , Villalba-Morales Jesús D. , Aracayo Luis A.
Published: August 2024

Dams are a type of civil infrastructure that can directly impact people’s well-being, as their function is energy production, flood control, or water supply. Therefore, it is worth generating strategies to assess its current condition, since structural changes may occur during its useful life. One highly effective approach for evaluating the structural integrity of dams involves monitoring alterations in modal parameters. This method enables the identification of abnormal changes that may arise from structural degradation. Numerous studies have revealed the strong influence of environmental factors on modal parameters, resulting in variations unrelated to structural damage. This paper investigates the effects of environmental factors such as upstream water level and air temperature on the temporal evolution of the identified modal parameters of a hydroelectric dam’s hollow-gravity concrete block. Modal identification is performed through an automatic procedure of estimating modal parameters to 30-min acceleration time series over 3 years of operation. Correlation analysis reveals a distinct relationship between the identified modal parameters and environmental factors. Changes in air temperature exhibit a direct proportional impact on natural frequencies, while fluctuations of the upstream level have an inverse effect. Furthermore, a time lag was observed in the natural frequencies concerning air temperature. Multiple linear regressions were fitted to mitigate the induced effects, incorporating as predictors the upstream water level and the averages of air temperature segments measured prior to the predicted frequency. A reduction in variability of more than 50% was achieved in an out-of-sample 8-month period for the modes linked to the natural frequencies most influenced by environmental factors.
An AI-Based Method for Estimating the Potential Runout Distance of Post-Seismic Debris Flows
Authors: Qiu Chenchen , Su Lijun , Bian Congchao , Zhao Bo , Geng Xueyu
Published: August 2024

The widely distributed sediments following an earthquake presents a continuous threat to local residential areas and infrastructure. These materials become more easily mobilized due to reduced rainfall thresholds. Before establishing an effective management plan for debris flow hazards, it is crucial to determine the potential reach of these sediments. In this study, a deep learning-based method—Dual Attention Network (DAN)—was developed to predict the runout distance of potential debris flows after the 2022 Luding Earthquake, taking into account the topography and precipitation conditions. Given that the availability of reliable precipitation data remains a challenge, attributable to the scarcity of rain gauge stations and the relatively coarse resolution of satellite-based observations, our approach involved three key steps. First, we employed the DAN model to refine the Global Precipitation Measurement (GPM) data, enhancing its spatial and temporal resolution. This refinement was achieved by leveraging the correlation between precipitation and regional environment factors (REVs) at a seasonal scale. Second, the downscaled GPM underwent calibration using observations from rain gauge stations. Third, mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE) were employed to evaluate the performance of both the downscaling and calibration processes. Then the calibrated precipitation, catchment area, channel length, average channel gradient, and sediment volume were selected to develop a prediction model based on debris flows following the Wenchuan Earthquake. This model was applied to estimate the runout distance of potential debris flows after the Luding Earthquake. The results show that: (1) The calibrated GPM achieves an average MAE of 1.56 mm, surpassing the MAEs of original GPM (4.25 mm) and downscaled GPM (3.83 mm); (2) The developed prediction model reduces the prediction error by 40 m in comparison to an empirical equation; (3) The potential runout distance of debris flows after the Luding Earthquake reaches 0.77 km when intraday rainfall is 100 mm, while the minimum distance value is only 0.06 km. Overall, the developed model offers a scientific support for decision makers in taking reasonable measurements for loss reduction caused by post-seismic debris flows.
Pin-on-disc tribological characterization of single ingredients used in a brake pad friction material
Authors: Carlevaris Davide , Varriale Francesco , Wahlström Jens , Menapace Cinzia
Published: August 2024

Researchers have long been studying the effects of the modification of friction material compositions on their tribological properties. Predictive models have also been developed, but they are of limited use in the design of new compositions. Therefore, this research aims to investigate the tribological behaviour of single ingredients in friction materials to develop a tribological dataset. This dataset could then be used as a foundation for a cellular automaton (CA) predictive model, intended to be a tool for designing friction materials. Tribological samples were almost entirely composed of four distinct friction material ingredients, and one sample composed of their mixture was successfully produced. Pin-on-disc (PoD) tribometer testing and scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDXS) analysis were used for the tribological characterization. Each material showed distinct tribological properties and evolution of the contact surface features, and the synergistic effect of their mutual interaction was also demonstrated by their mixture.
Tribological behavior of TiN, AlTiN, and AlTiCrN coatings in atmospheric and vacuum environments
Authors: Hwang Youn-Hoo , Seo Kuk-Jin , Kim Tae-Hyeong , Min You Jin , Liu Yuzhen , Kim Dae-Eun
Published: August 2024

In this study, the tribological characteristics of TiN, AlTiN, and AlTiCrN coatings sliding against a SUS420J1 stainless steel pin were investigated in atmospheric and vacuum environments. The coatings were deposited on SUS440C substrates using the arc-physical vapor deposition technique. The friction and wear behavior of the coatings were evaluated based on the systematic analyses of the friction coefficient data as well as the physical and chemical state of the wear track. The results revealed that the friction coefficients of the SUS440C specimen and AlTiCrN coatings increased, whereas those of the TiN and AlTiN coatings decreased when the environment was changed from atmospheric to vacuum. It was confirmed that the formation of an oxide layer and adsorption of oxides on the surface were dominant factors that influenced the tribological behavior in the atmospheric environment. On the other hand, the compatibility, oxidation inhibition, and droplets of the surface mainly affected the frictional characteristics in the vacuum environment. The results of this work are expected to aid in the selection of proper coating materials for tribological systems operating in a vacuum.
Advancing Rapid Arsenic (III) Detection Through Device-Integrated Colorimetry
Authors: Bonthula Sumalatha , Devarajan Surya , Maurya Muni Raj , Al-Maadeed Somaya , Maalej Ramzi , Chaari Mohamed Zied , Sadasivuni Kishor Kumar
Published: August 2024

It is essential to detect precise traces of inorganic arsenic ions when utilized, which may increase the risks of several health issues such as lung, bladder, skin cancer, and diabetes diseases. In this study, bromocresol green, chlorophenol red, and cresol red dyes were examined to detect the presence of arsenic (III). Further, we present a colorimetric arsenic (III) detection using a cost-effective paper-based sensor and portable device method. The calibration plot from UV-Vis absorption exhibited a detection limit of ∼0.054 µM of arsenic (III) in the detection range of 0–10 mM. The selectivity study establishes this method for visual on-site detection of arsenic (III) combined with the simultaneous presence of common coexisting ions. The paper and device-based dual strategy to detect arsenic (III) offered high sensitivity and selectivity under room conditions. Both the paper sensor and the proposed device have a potential for rapid on-site detection of arsenic (III). Therefore, it could provide a viable solution for the design of affordable, sensitive, and portable tools for the environmental monitoring of arsenic (III).
The lasting impact of virtual interviews on surgical fellowship applicants
Authors: Becker Ellen R. , Xu Catherine T. , Pratt Catherine G. , Whitrock Jenna N. , Frasier Lane L. , Van Haren Robert M. , Quillin Ralph C.
Published: August 2024

Purpose

Surgical fellowship interviews shifted to a virtual platform in 2020 due to the COVID-19 pandemic. While virtual interviews provide convenience, they also pose difficulties for programs and raise potential barriers for applicants. This study compares in-person to virtual interviews and characterizes the impact on programs and applicants.

Methods

In-person (2007–2019) and virtual (2020–2022) fellowship application data were extracted from publicly available NRMP Specialties Matching Service data. Fellowship programs included surgical critical care, surgical oncology, colorectal, pediatric, thoracic, and vascular surgery. Competitiveness was assessed using a validated normalized competitiveness index (NCI).

Results

Since virtual interviews, rankings per applicant, a surrogate for program interview workload, increased for all fellowships except pediatric surgery. The most competitive subspecialties now include colorectal, pediatric, and thoracic surgery. For non-US MDs in these subspecialties, applicants per position decreased (pediatric), match rate decreased (thoracic), and NCI increased (thoracic) under virtual interviewing. However, for the least competitive subspecialties, non-US MDs had increased rankings per applicant (critical care and vascular), increased match rate (critical care and surgical oncology), and decreased NCI (surgical oncology) with virtual interviewing.

Conclusions

Since the virtual platform was implemented, applicants have interviewed at and ranked more programs, subsequently increasing program workload. While this is positive for many applicants, a differential pattern of securing a fellowship emerged for non-US MD applicants. This finding is important for fellowship program directors to consider and ensure non-US MD applicants are not marginalized with the virtual platform.

Level of Evidence

III
Improving Access Trust in Healthcare Through Multimodal Deep Learning for Affective Computing
Authors: Sakthidevi I. , Fathima G.
Published: August 2024

In healthcare domain, access trust is of prime importance paramount to ensure effective delivery of medical services. It also fosters positive patient-provider relationships. With the advancement of technology, affective computing has emerged as a promising approach to enhance access trust. It enables systems to understand and respond to human emotions. The research work investigates the application of multimodal deep learning techniques in affective computing to improve access trust in healthcare environment. A novel algorithm, "Belief-Emo-Fusion," is proposed, aiming to enhance the understanding and interpretation of emotions in healthcare. The research conducts a comprehensive simulation analysis, comparing the performance of Belief-Emo-Fusion with existing algorithms using simulation metrics: modal accuracy, ınference time, and F1-score. The study emphasizes the importance of emotion recognition and understanding in healthcare settings. The work highlights the role of deep learning models in facilitating empathetic and emotionally intelligent technologies. By addressing the challenges associated with affective computing, the proposed approach contributes to the development of more effective and reliable healthcare systems. The findings offer valuable insights for researchers and practitioners seeking to leverage deep learning techniques for enhancing trust and communication in healthcare environments.
Violent Competition and Terrorist Restraint
Authors: Polo Sara M.T. , Welsh Blair
Published: August 2024

A large literature has argued that domestic competition increases a militant organization's use and severity of terrorism to differentiate their “brand” and “outbid” other organizations. However, most empirical analyses infer such competition from the quantity of groups present in a geographic area. This approach neglects specific group relationships, such as cooperation, rhetorical or violent rivalry, or peaceful coexistence. We introduce a behavioral measure of group competition and argue that variation in the quality, rather than the quantity, of competition affects the violence profile of militant groups in unexpected ways. Violent competition, where militants attack one another, imposes significant constraints on group resources and increases groups’ dependence on civilian support, which exacerbates the costs of a popular backlash against brutality. Moreover, violent competition effectively substitutes for crowding out rivals via outbidding. As competition becomes extreme, we posit that groups increasingly opt for a strategy of terrorist restraint and reduce the share of high-profile attacks on soft civilian targets. We test this argument at the macro and micro levels with cross-national data on 290 organizations in civil war (1970–2018) and granular data on the subnational targeting strategy of the Islamic State in Syria (2013–2018). Both analyses provide robust support for our argument. The findings shed light on the strategic limitations of outbidding and provide important insights for research and policy.
One step closer to the First Stars: +150 OB stars in the metal-poor galaxy Sextans A
Authors: Lorenzo Marta , Garcia Miriam , Najarro Francisco
Published: August 2024

Local Group (LG) very metal-poor massive stars are the best proxy for the First Stars of the Universe, fundamental to model the early evolution of the first galaxies, and key to unravelling new evolutionary pathways restricted to low metallicities, such as chemically homogeneous evolution. Yet, due to the great leap in distance required to reach metal-poor galaxies of the LG and vicinity, no comprehensive spectroscopic studies have been carried out at sub-$$$$ metallicities so far.

We focus on the massive star population of the 1/10Ȯ galaxy Sextans A. After five observing campaigns at the 10.4-m Gran Telescopio Canarias (GTC), we have assembled a spectroscopic catalogue of more than 150 OB stars. This catalogue will be fundamental to test stellar evolution at very low metallicity, to detect the first binary systems at 1/10Ȯ and to unveil the most recent star formation history of this galaxy.
Luminous blue variables and B[e] supergiants
Authors: Mehner Andrea
Published: August 2024

Luminous blue variables (LBVs) and B[e] supergiants (B[e]SGs) are some of the most massive stars that display extreme and puzzling behavior. Their rarity indicates that they belong to short evolutionary phases or short-lived phenomena in the post-main sequence evolution of massive stars. However, their strong mass loss and episodic mass eruptions may be crucially impacting massive star evolution. LBVs are a group of evolved massive stars that exhibit irregular variability and eruptive mass loss. Various subtypes, including S Doradus variables, giant eruptions, and pre-supernova outbursts, exist. The physical cause of the LBV phenomenon remains heavily debated. B[e]SGs have strong forbidden line emission and infrared excess from dust that are thought to arise in a circumstellar disk or torus. The formation mechanism of their disk-like structures is yet to be settled. The evolutionary phases of LBVs and B[e]SGs and their connection to other evolved massive stars are important unanswered questions in massive star evolution.
On the elusive detection of O-type stars close to the ZAMS: the empirical birthline of massive stars
Authors: Holgado G. , Simón-Díaz S. , Haemmerlé L.
Published: August 2024

In this contribution we present the results from a1 homogeneous quantitative spectroscopic analysis of ∼400 Galactic O-type stars targeted by the IACOB and OWN surveys. The ultimate objective is to perform a modern reassessment of one of the long-standing problems in the field of massive stars: the elusive detection of mid O-type stars close to the “canonical” theoretical ZAMS. We first provide statistically significant evidence of the existence of a clear lack of stars in our sample populating the region of the spectroscopic HR diagram approximately delimited by the theoretical ZAMS, the ∼ 40 and ∼ 70 M⊙ single evolutionary tracks and the 2 Myr isochrone. We then evaluate if this empirical result could be a result of possible limitations of our analysis strategy and/or the existence of potential observational biases affecting the compiled sample. Once both explanations are investigated, we evaluate the possibility that a modification of the efficiency of mass accretion during the star formation process could lead to a new (corrected) theoretical ZAMS in better accordance with our empirical results.
Low-frequency radio view of a fast-blue optical transient - AT 2018cow
Authors: Nayana A. J. , Chandra Poonam
Published: August 2024

We present low-frequency (0.40 – 1.25 GHz) radio observations and modeling of a Fast Blue Optical Transient (FBOT), AT2018cow [Nayana & Chandra(2021)]. Our data are best modeled as an inhomogeneous synchrotron emitting region expanding into an ionized circumstellar medium. We estimate the mass-loss rate of the progenitor star and shock parameters at multiple epochs post-explosion and find that the progenitor has gone through an enhanced phase of mass-loss close to its end-of-life.
Constraining the dynamical mass of the massive binary 9 Sagittarii
Authors: Fabry Matthias , Hawcroft Calum , Frost Abigail J. , Mahy Laurent , Marchant Pablo , Le Bouquin Jean-Baptiste , Sana Hugues
Published: August 2024

Especially in the upper Hertzsprung-Russell diagram, where stellar physics is least understood, obtaining model independent masses is of great value. Spectroscopic binaries that are also resolved astrometrically are an excellent alternative to eclipsing double-lined spectroscopic binaries where dynamical masses can be measured. 9 Sgr is such a massive binary. However, its characterization is troubled by conflicting conclusions from the spectroscopic analysis on the one hand and the interferometric one on the other hand. In this work, we attempt to resolve this tension by applying a novel approach to spectral disentangling of the spectroscopic data to constrain better the mass of 9 Sgr.
The enigmatic winds of Wolf-Rayet stars: Results from dynamically consistent atmosphere modelling
Authors: Sander Andreas A. C.
Published: August 2024

Line-driven stellar winds are ubiquitous among hot massive stars. In some cases they can become so strong, that the whole star is cloaked by an optically thick wind. The strong outflow gives rise to large emission lines, defining the class of so-called Wolf-Rayet (WR) stars. While being major players in the evolution of massive stars, the formation of heavy black holes, and the distribution of elements, the occurrence and nature of WR winds is still quite enigmatic.

A promising instrument towards a better theoretical understanding are stellar atmospheres allowing for a consistent inclusion of the hydrodynamics. By coupling stellar and wind parameters and the inclusion of a detailed non-LTE radiative transfer, they allow us to go beneath the observable layers and study the onset of WR-type winds. Establishing larger sets of models, we were able to make ground-breaking progress by identifying trends with mass and metallicity that deviate significantly from present empirical descriptions. Our modelling efforts reveal a complex picture for WR-type winds with strong, non-linear dependencies. Besides covering metallicity and mass, we further identify surface hydrogen as an important ingredient to retain WR-type mass loss at lower metallicity. Here, we present a summary of recent insights on the nature and onset of WR-type winds in massive stars including the consequences for stellar evolution, remaining open questions, and current efforts to overcome them.
Dissecting the very metal-poor galaxy SBS0335-052E with MUSE: massive stars vs. nebular HeII emission
Authors: Kehrig C. , Vílchez J. M. , Guerrero M. A. , Iglesias-Páramo J. , Hunt L. K. , Duarte Puertas S. , Ramos-Larios G.
Published: August 2024

Nebular Heii emission implies the presence of energetic photons (E≽54 eV). Despite the great deal of effort dedicated to understanding Heii ionization, its origin has remained mysterious, particularly in metal-deficient star-forming galaxies. Unfolding Heii-emitting, metal-poor starbursts at z∼0 can yield insight into the powerful ionization processes occurring in the primordial universe. Here we present a study on the origin of the extended nebular Heii emission in SBS 0335-052E, one of the most metal-poor (Z ∼ 3% Z⊙ Heii-emitter starbursts known locally. Based on optical VLT/MUSE spectroscopic and Chandra X-ray observations, and current stellar models we found that the Heii-ionization budget of SBS 0335-052E can only be produced by peculiar, nearly metal-free ionizing stars (called here “PopIII-like” stars) with a top-heavy initial mass function. This result is in line with recent simulations for PopIII star formation down to z=0.
Spins of stripped B stars support magnetic internal angular momentum transport
Authors: Schürmann Christoph , Langer Norbert , Xu Xiao-Tian , Wang Chen
Published: August 2024

The galactic binary star LB-1 contains a recently stripped B-type star. Comparing its properties to detailed binary star models shows that tidal braking and magnetic torques lead to low surface rotational velocities in the stripped donors after Roche-lobe overﬃow. Models without magnetic torques cannot reproduce the observed low surface rotation.
First results of a magnetic survey of classical Cepheids
Authors: Barron James A. , Wade Gregg A. , Folsom Colin P. , Kochukhov Oleg
Published: August 2024

We report recent ESPaDOnS and HARPSpol spectropolarimetric observations from our ongoing magnetic survey of the brightest twenty-five classical Cepheids. Stokes V magnetic signatures are detected in eight of fifteen targets observed to date. The Stokes V profiles show a diversity of morphologies with weak associated longitudinal field measurements of order 1 G. Many of the Stokes V profiles are difficult to interpret in the context of the normal Zeeman effect. They consist of approximately unipolar single or double lobe(s) of positive or negative circular polarization. We hypothesize that these unusual signatures are due to the Zeeman effect modified by atmospheric velocity or magnetic field gradients. In contrast, the Stokes V profiles of Polaris and MY Pup appear qualitatively similar to the complex magnetic signatures of non-pulsating cool supergiants, possibly due to the low pulsation amplitudes of these two stars.
Alicante Survey of Massive Stars in H ii regions (A-SMASHER)
Authors: Marco A. , Negueruela I. , de la Fuente D. , Patrick L. R. , Herrero A. , Eikenberry S. S.
Published: August 2024

The aim of this survey is the homogeneous characterization of a large sample of H ii regions with active star formation in order to detect observational trends supporting the two main models of massive star formation.
The multiplicity of Galactic Wolf-Rayet stars
Authors: Dsilva Karan , Shenar Tomer , Sana Hugues , Marchant Pablo
Published: August 2024

We present the results of a magnitude-limited spectroscopic survey of Galactic Wolf-Rayet stars with the HERMES spectrograph mounted on the Mercator telescope. Using cross-correlation to measure radial velocities, we measured the observed binary fractions of the Galactic carbon- (WC) and nitrogen-rich (WN) Wolf-Rayet stars to be and . We used Monte-Carlo simulations with a Bayesian framework to derive the intrinsic multiplicity properties and found and . We find that the majority of WN binaries reside in short-period systems, similar to O stars. However, the orbital period distribution of the Galactic WC population peaks at 5000 d, a discrepancy that challenges our current understanding of binary evolution in Wolf-Rayet stars.
Analytic, Turbulent Pressure Driven Mass Loss from Red Supergiants
Authors: Kee N. Dylan ,   the MAESTRO Project
Published: August 2024

Despite the important role mass loss in the red supergiant phase plays in controlling stellar evolution and massive stars’ final supernova fates, a theoretical explanation of the mechanism driving this mass loss has been elusive. In this contribution we present a recent breakthrough [Kee et∼al., 2021] showing that turbulent pressure alone is sufficient to markedly extend the atmospheres of red supergiants and allow a wind to be launched. The resulting theory provides a fully analytic prescription for red supergiant mass-loss rates. Moreover, the theoretical mass-loss rates computed from observationally inferred turbulent velocities are in overall good agreement with observationally inferred red supergiant mass loss. A particularly interesting aspect of this theory is that it is not sensitive to metallicity, providing important implications for stellar evolution and the so-called “red-supergiant problem” for supernova progenitors in various environments.
ULLYSES and Complementary Surveys of Massive Stars in the Magellanic Clouds
Authors: Crowther Paul A.
Published: August 2024

An overview is provided of the scientific goals of the Magellanic Cloud component of the STScI Directors Discretionary UV initiative ULLYSES, together with the complementary spectroscopic survey XShootU (VLT/Xshooter) and other ancillary datasets. Together, ULLYSES and XShootU permit the first comprehensive, homogeneous study of wind densities and velocities in metal-poor massive stars, plus UV/optical spectroscopic libraries for population synthesis models and a large number of interstellar sight-lines towards the Magellanic Clouds.
Constraining massive star mass loss through supernova radio properties
Authors: Moriya Takashi
Published: August 2024

Supernova properties in radio strongly depend on their circumstellar environment and they are an important probe to investigate the mass loss of supernova progenitors. Recently, core-collapse supernova observations in radio have been assembled and the rise time and peak luminosity distribution of core-collapse supernovae in radio has been obtained. In this talk, we will discuss the constraints on the mass-loss prescriptions of red supergiants obtained from the assembled radio properties of Type II supernovae. We take a couple of mass-loss prescriptions for red supergiants, calculate the rise time and peak luminosity distribution based on them, and compare the results with the observed distribution. We found that the widely spread radio rise time and peak luminosity distribution of Type II supernovae can only be explained by mass-loss prescriptions having strong dependence on the luminosity. Red supergiant mass-loss prescriptions should have steep luminosity dependence in the supernova progenitor range.
The largest and most ambitious quantitative spectroscopic analysis of B-type supergiants in the Milky Way
Authors: de Burgos Abel , Simon-Díaz Sergio , Urbaneja Miguel A.
Published: August 2024

Empirical constraints are master keys for testing theoretical evolutionary model predictions. In massive stars, the region in the Hertzsprung-Russell diagram (HRD) in which the Blue Supergiants (BSGs) are located sets several important constraints to the models, and in particular to the theoretical end of the main sequence (MS). So far, we are missing from a full quantitative spectroscopic analysis (QSA) of a sample of BSGs large enough to be statistically significant and without observational biases. We present results from a QSA of a sample of ∼700 Galactic BSGs for which we have high-resolution multi-epoch optical spectra.
NGC 3125-A1 revisited at higher spectral resolution with COS G160M
Authors: Wofford A. , Sixtos A. , Smith L. , Charlot S. , Bruzual G.
Published: August 2024

Super star cluster (SSC) A1 in starburst galaxy NGC 3125 has the strongest broad He II λ1640 emission line ever observed in the nearby Universe and constitutes an important template for interpreting observations of galaxies that are located out to a redshift of z∼3. We use observations of SSC A1 obtained with the Cosmic Origins Spectrograph (COS) on board of the Hubble Space Telescope (HST) in order to check if there is a contribution of nebular emission to the He II line. In addition, we compare the COS G130M + G160M observations of A1 (1150 – 1750∘A) to the latest Charlot & Bruzual population synthesis models, which account for Very Massive Stars (VMS) of up to 300 Mȯ. A model with Z = 0.008 and age = 2.4 Myr provides a very reasonable fit to the C III λ1175, N V λ1240, C IV λ1550, He II λ1640, and N IV λ1718 stellar-wind features, although the O V λ1371 line is not well reproduced. Overall, our results show the great improvement of stellar evolution and population synthesis models over the past decade, and in particular, the improved formulation of stellar mass loss rates.
Variable mass loss on 100 yr timescales from massive yellow hypergiants
Authors: Oudmaijer René D. , Koumpia Evgenia
Published: August 2024

This contribution presents new results on two members of the class of post-Red Supergiants, IRAS 17163-3907, the central star of the Fried Egg nebula and IRC +10420. New optical spectra in the blue spectral range confirm their spectral type to be of A-supergiant class. Our VLTI/GRAVITY K-band interferometry reveals that the neutral Na i 2.2 μm line emitting region is smaller than that of the hydrogen Brγ emission. This can be explained with the hydrogen emission the result of collisional excitation populating the higher levels in a neutral region instead them being populated through recombination in an ionised environment as mostly inferred in stellar winds. Finally, the central star of the Fried Egg nebula, has undergone 3 distinct mass loss episodes over the last hundreds of years. As it is likely that at least the last mass loss event occurred when the star was already a Yellow Hypergiant and not a Red Supergiant, we put forward the bi-stability mechanism as explanation for the mass loss.
Supplying angular momentum to the jittering jets explosion mechanism using convection in inner star layers
Authors: Shishkin Dmitry
Published: August 2024

The jittering jets explosion mechanism of core collapse supernovae proposes that stochastic convective motion, amplified by instabilities, results in intermittent accretion disk that launches jittering jets that explode the star. We conduct one-dimensional simulations of a wide range of stellar masses and show that the convective motion in the pre-collapse stellar core, when scaled to corresponding three-dimensional simulations, supply sufficient angular momentum fluctuation to form the intermittent accretion disk the launches the jittering jets. The resulting neutron star masses are consistent with observations.