bluuebunny/crossref_metadata_2025 huggingface dataset:
Adverse fetal/neonatal and obstetric outcomes in pregnancies with both maternal and fetal heart disease
Authors: Fernandez-Campos Beatriz A. , Grewal Jasmine , Kiess Marla , Siu Samuel C. , Pfaller Birgit , Sermer Mathew , Mason Jennifer , Silversides Candice K. , Haberer Kim
Published: July 2024

Objective

To investigate fetal/neonatal and obstetric events in pregnancies with both maternal and fetal heart disease.

Study design

From the CARPREG database, singleton pregnancies (>24 weeks) in patients with structural heart disease that underwent fetal/neonatal echocardiograms were selected and separated in two groups: maternal heart disease only (M-HD) and maternal and fetal heart disease (MF-HD). Differences in adverse fetal/neonatal (death, preterm birth, and small for gestational age) and obstetric (preeclampsia/eclampsia) outcomes between groups were analyzed.

Results

From 1011 pregnancies, 93 had MF-HD. Fetal/neonatal events (38.7% vs 25.3%, p = 0.006) and spontaneous preterm birth (10.8% vs 4.9%, p = 0.021) were more frequent in MF-HD compared to M-HD, with no difference in obstetric events. MF-HD remained as a significant predictor of fetal/neonatal events after adjustment (OR:1.883; 95% CI:1.182–3.000; p = 0.008).

Conclusions

Pregnancies with MF-HD are at risk of adverse fetal/neonatal events and spontaneous preterm birth. Larger studies are needed to determine their association with preeclampsia.
The genetic basis of divergent melanic pigmentation in benthic and limnetic threespine stickleback
Authors: Tapanes Elizabeth , Rennison Diana J.
Published: July 2024

Pigmentation is an excellent trait to examine patterns of evolutionary change because it is often under natural selection. Benthic and limnetic threespine stickleback (Gasterosteus aculeatus) exhibit distinct pigmentation phenotypes, likely an adaptation to occupation of divergent niches. The genetic architecture of pigmentation in vertebrates appears to be complex. Prior QTL mapping of threespine stickleback pigmentation phenotypes has identified several candidate loci. However—relative to other morphological phenotypes (e.g., spines or lateral plates)—the genetic architecture of threespine stickleback pigmentation remains understudied. Here, we performed QTL mapping for two melanic pigmentation traits (melanophore density and lateral barring) using benthic-limnetic F2 crosses. The two traits mapped to different chromosomes, suggesting a distinct genetic basis. The resulting QTLs were additive, but explained a relatively small fraction of the total variance (~6%). QTLs maps differed by F1 family, suggesting variation in genetic architecture or ability to detect loci of small effect. Functional analysis identified enriched pathways for candidate loci. Several of the resulting candidate loci for pigmentation, including three loci in enriched pathways (bco1, sulf1, and tyms) have been previously indicated to affect pigmentation in other vertebrates. These findings add to a growing body of evidence suggesting pigmentation is often polygenic.
Insights from EEG analysis of evoked memory recalls using deep learning for emotion charting
Authors: Dar Muhammad Najam , Akram Muhammad Usman , Subhani Ahmad Rauf , Khawaja Sajid Gul , Reyes-Aldasoro Constantino Carlos , Gul Sarah
Published: July 2024

Affect recognition in a real-world, less constrained environment is the principal prerequisite of the industrial-level usefulness of this technology. Monitoring the psychological profile using smart, wearable electroencephalogram (EEG) sensors during daily activities without external stimuli, such as memory-induced emotions, is a challenging research gap in emotion recognition. This paper proposed a deep learning framework for improved memory-induced emotion recognition leveraging a combination of 1D-CNN and LSTM as feature extractors integrated with an Extreme Learning Machine (ELM) classifier. The proposed deep learning architecture, combined with the EEG preprocessing, such as the removal of the average baseline signal from each sample and extraction of EEG rhythms (delta, theta, alpha, beta, and gamma), aims to capture repetitive and continuous patterns for memory-induced emotion recognition, underexplored with deep learning techniques. This work has analyzed EEG signals using a wearable, ultra-mobile sports cap while recalling autobiographical emotional memories evoked by affect-denoting words, with self-annotation on the scale of valence and arousal. With extensive experimentation using the same dataset, the proposed framework empirically outperforms existing techniques for the emerging area of memory-induced emotion recognition with an accuracy of 65.6%. The EEG rhythms analysis, such as delta, theta, alpha, beta, and gamma, achieved 65.5%, 52.1%, 65.1%, 64.6%, and 65.0% accuracies for classification with four quadrants of valence and arousal. These results underscore the significant advancement achieved by our proposed method for the real-world environment of memory-induced emotion recognition.
Revisiting the Heider and Simmel experiment for social meaning attribution in virtual reality
Authors: Marañes Carlos , Gutierrez Diego , Serrano Ana
Published: July 2024

In their seminal experiment in 1944, Heider and Simmel revealed that humans have a pronounced tendency to impose narrative meaning even in the presence of simple animations of geometric shapes. Despite the shapes having no discernible features or emotions, participants attributed strong social context, meaningful interactions, and even emotions to them. This experiment, run on traditional 2D displays has since had a significant impact on fields ranging from psychology to narrative storytelling. Virtual Reality (VR), on the other hand, offers a significantly new viewing paradigm, a fundamentally different type of experience with the potential to enhance presence, engagement and immersion. In this work, we explore and analyze to what extent the findings of the original experiment by Heider and Simmel carry over into a VR setting. We replicate such experiment in both traditional 2D displays and with a head mounted display (HMD) in VR, and use both subjective (questionnaire-based) and objective (eye-tracking) metrics to record the observers’ visual behavior. We perform a thorough analysis of this data, and propose novel metrics for assessing the observers’ visual behavior. Our questionnaire-based results suggest that participants who viewed the animation through a VR headset developed stronger emotional connections with the geometric shapes than those who viewed it on a traditional 2D screen. Additionally, the analysis of our eye-tracking data indicates that participants who watched the animation in VR exhibited fewer shifts in gaze, suggesting greater engagement with the action. However, we did not find evidence of differences in how subjects perceived the roles of the shapes, with both groups interpreting the animation’s plot at the same level of accuracy. Our findings may have important implications for future psychological research using VR, especially regarding our understanding of social cognition and emotions.
Exceptional performance with minimal data using a generative adversarial network for alzheimer's disease classification
Authors: Wong Pui Ching , Abdullah Shahrum Shah , Shapiai Mohd Ibrahim
Published: July 2024

The classification of Alzheimer's disease (AD) using deep learning models is hindered by the limited availability of data. Medical image datasets are scarce due to stringent regulations on patient privacy, preventing their widespread use in research. Moreover, although open-access databases such as the Open Access Series of Imaging Studies (OASIS) are available publicly for providing medical image data for research, they often suffer from imbalanced classes. Thus, to address the issue of insufficient data, this study proposes the integration of a generative adversarial network (GAN) that can achieve comparable accuracy with a reduced data requirement. GANs are unsupervised deep learning networks commonly used for data augmentation that generate high-quality synthetic data to overcome data scarcity. Experimental data from the OASIS database are used in this research to train the GAN model in generating synthetic MRI data before being included in a pretrained convolutional neural network (CNN) model for multistage AD classification. As a result, this study has demonstrated that a multistage AD classification accuracy above 80% can be achieved even with a reduced dataset. The exceptional performance of GANs positions them as a solution for overcoming the challenge of insufficient data in AD classification.
Employee innovation during office work, work from home and hybrid work
Authors: Gibbs Michael , Mengel Friederike , Siemroth Christoph
Published: July 2024

The Covid-19 pandemic forced firms globally to shift workforces to working from home [WFH]. Firms are now struggling to implement a return to working from the office [WFO], as employees enjoy the significant benefits of WFH for their work-life balance. Therefore many firms are adopting a hybrid model in which employees work partly from the office and partly from home. We use unique and detailed data from an Indian IT services firm which contains a precise measure of innovation activity of over 48,000 employees in these three work environments. Our key outcomes are the quantity and quality of ideas submitted by employees. Based on an event study design, the quantity of ideas did not change during the WFH period as compared to WFO, but the quality of ideas suffered. During the later hybrid period, the quantity of submitted ideas fell. In the hybrid phase innovation suffered particularly in teams which were not well coordinated in terms of when they worked at the office or from home. Our findings suggest that remote and hybrid work modes may inhibit collaboration and innovation.
Using climate envelopes and earth system model simulations for assessing climate change induced forest vulnerability
Authors: Martes Leam , Pfleiderer Peter , Köhl Michael , Sillmann Jana
Published: July 2024

Changing climatic conditions threaten forest ecosystems. Drought, disease and infestation, are leading to forest die-offs which cause substantial economic and ecological losses. In central Europe, this is especially relevant for commercially important coniferous tree species. This study uses climate envelope exceedance (CEE) to approximate species risk under different future climate scenarios. To achieve this, we used current species presence-absence and historical climate data, coupled with future climate scenarios from various Earth System Models. Climate scenarios tended towards drier and warmer conditions, causing strong CEEs especially for spruce. However, we show that annual averages of temperature and precipitation obscure climate extremes. Including climate extremes reveals a broader increase in CEEs across all tree species. Our study shows that the consideration of climate extremes, which cannot be adequately reflected in annual averages, leads to a different assessment of the risk of forests and thus the options for adapting to climate change.
Reversible acetylation of HDAC8 regulates cell cycle
Authors: Sang Chaowei , Li Xuedong , Liu Jingxuan , Chen Ziyin , Xia Minhui , Yu Miao , Yu Wei
Published: July 2024

HDAC8, a member of class I HDACs, plays a pivotal role in cell cycle regulation by deacetylating the cohesin subunit SMC3. While cyclins and CDKs are well-established cell cycle regulators, our knowledge of other regulators remains limited. Here we reveal the acetylation of K202 in HDAC8 as a key cell cycle regulator responsive to stress. K202 acetylation in HDAC8, primarily catalyzed by Tip60, restricts HDAC8 activity, leading to increased SMC3 acetylation and cell cycle arrest. Furthermore, cells expressing the mutant form of HDAC8 mimicking K202 acetylation display significant alterations in gene expression, potentially linked to changes in 3D genome structure, including enhanced chromatid loop interactions. K202 acetylation impairs cell cycle progression by disrupting the expression of cell cycle-related genes and sister chromatid cohesion, resulting in G2/M phase arrest. These findings indicate the reversible acetylation of HDAC8 as a cell cycle regulator, expanding our understanding of stress-responsive cell cycle dynamics.
Synthesis, Properties, and Biological Applications of 1,3-Thiazoles
Authors: Darekar N. R. , Khedkar V. M. , Gadekar P. K. , Mhaske S. D. , Takate S. J. , Akolkar H. N.
Published: July 2024

In the field of medicinal chemistry, thiazole, a heterocycle containing sulfur and nitrogen atoms, plays a significant role. It is a key core scaffold found in numerous naturally occurring (e.g. vitamin B1 or thiamine) and synthesized compounds that exhibit significant medicinal value. The 1,3-thiazole scaffold is the mainstay of numerous clinically used drugs, such as nizatidine, meloxicam, ritonavir, tiazofurin, bleomycin, and nitazoxanide. Molecules containing thiazole nuclei are attractive targets in medicinal chemistry attributed to their broad spectrum of biological functions, such as antiproliferative, antioxidant, antitubercular, anti-inflammatory, and antimicrobial activities. This chapter discusses the different synthesis pathways of thiazole-embodying molecules and their anticancer, antitubercular, antioxidant, and antimicrobial activities, reflecting upon numerous biological applications.
Synthesis, Properties, and Biological Applications of Benzothiazepines
Authors: Kumari Puja , Dwivedi Yashi , Chandrashekharappa Sandeep
Published: July 2024

Benzothiazepines are attracting interest in the fields of medicinal and pharmaceutical chemistry because they serve as the core structure of certain drugs, particularly calcium channel blockers. This core structure is used to treat conditions such as high blood pressure and angina (chest pain) by modulating the flow of calcium ions in cells, particularly in the cells of the heart and blood vessels. One of the well-known drugs based on the benzothiazepine structure is diltiazem, which is used as a calcium channel blocker. This class of compounds is important for treating cardiovascular diseases. One of the classes of benzothiazepines is 1,4-benzothiazepine, which is a little-explored compound. Only a few members belonging to this group are known in the literature. This class has been widely explored in chemical synthesis rather than biological evaluation. A diverse range of 1,4-benzothiazepines have been synthesized by multistep synthesis, heterogeneous catalysis, microwave-aided approach, and ultrasonic synthesis. Few researchers reported the 1,4-benzothiazepine scaffold as a central nervous system (CNS) depressant, bile acid absorption inhibitor, anxiolytic drug, anti-HIV agent, and antitumor agent. This study reveals several methods that have been used to synthesize 1,4-benzothiazepine derivatives. Furthermore, it can help in new drug discovery.
Exploring Natural Product Chemistry
Authors: Hanley A. Bryan
Published: July 2024

Global warming and, even more recently, the COVID pandemic have brought into public focus our dependence on science and the lens with which it considers the world. Science is providing opportunities for new ways of thinking and has always opened new avenues for creative thought and advances.

This book examines and summarises the developments and changes in approaches to organic and natural product chemistry as seen through the published works of the author and seeks to place them in a philosophical and societal context. Demonstrating and explaining how scientists and, more particularly, chemists arrive at a world view, it will show how this is predicated not just by scientific advances but also by societal influences. The author uses personal experience to detail progress through science. Techniques used in such investigations are alluded to but not described in detail since the interested reader can access the full published papers if required.

Interesting both to the general, scientifically literate reader and to the specialist wanting information on natural product chemistry, the book does not create a rulebook for carrying out natural product chemistry but rather examines the processes that lie beneath the development of natural product chemistry and how this enables chemists to examine and interpret the world. Students of chemistry (whatever their age or stage of career) may also be interested in reading how peer reviewed and published material relates to the wider society view.
Embracing heterogeneous photocatalysis: evolution of photocatalysts in annulation of dimethylanilines and maleimides
Authors: Liu Yan , Li Rui , Lv Qiyan , Yu Bing
Published: July 2024

We summarize the recent advances in the photocatalytic annulation of tertiary amines and maleimides for the synthesis of tetrahydroquinolines.
Chemical fixation of CO2/CS2 to access iodoallenyl oxazolidinones and allenyl thiazolidine-thiones
Authors: Li Xuejian , Liu Qinglong , Song Wangze
Published: July 2024

CO2/CS2 was used to prepare iodoallenyl- and allenyl heterocycles with high yields and diastereoselectivities in a metal-free manner under mild conditions.
Chemical bonding within AIIIBVI materials under uniaxial compression
Authors: Stepanov Roman S. , Radina Aleksandra D. , Tantardini Christian , Kvashnin Alexander G. , Kolobov Alexander V.
Published: July 2024

Conducted theoretical analysis of AIIIBV structures using quantum chemical topology, elucidating chemical bonding peculiarities and enhancing understanding of phase transitions. This is crucial for fine-tuning their electronic properties.
Analysis of protein–protein and protein–membrane interactions by isotope-edited infrared spectroscopy
Authors: Tatulian Suren A.
Published: July 2024

This article highlights the power of isotope-edited FTIR spectroscopy in resolving important problems encountered in biochemistry, biophysics, and biomedical research, focusing on protein–protein and protein membrane interactions.
Fluorescence and lasing of neutral nitrogen molecules inside femtosecond laser filaments in air: mechanism and applications
Authors: Mei Haicheng , Jiang Hongbing , Houard Aurélien , Tikhonchuk Vladimir , Oliva Eduardo , Mysyrowicz André , Gong Qihuang , Wu Chengyin , Liu Yi
Published: July 2024

High power femtosecond laser pulses launched in air undergo nonlinear filamentary propagation, featuring a bright and thin plasma channel in air with its length much longer than the Rayleigh length of the laser beam.
Surface termination effects on Raman spectra of Ti3C2Tx MXenes: an in situ UHV analysis
Authors: Plaickner Julian , Petit Tristan , Bärmann Peer , Schultz Thorsten , Koch Norbert , Esser Norbert
Published: July 2024

This work provides new insights into the interpretation of Raman spectra of Ti3C2Tx MXenes by thermal desorption of surface terminations in vacuum. Despite broad spectral features, the contribution of the fluorine termination is clearly identified.
Interplay between anion–receptor and anion–solvent interactions in halide receptor complexes characterized with ultrafast infrared spectroscopies
Authors: Dean Jessika L. S. , Cramer Caroline G. , Fournier Joseph A.
Published: July 2024

The effects of solute–solvent interactions on anion–receptor H-bonding interactions are characterized using ultrafast infrared spectroscopies.
Manganese catalysed reduction of nitriles with amine boranes
Authors: Weber Stefan , Blaha Ines , Kirchner Karl
Published: July 2024

The room temperature reduction of various nitriles using amine boranes catalysed by a manganese(i) alkyl complex is described. Based on experimental findings, a plausible mechanistic scenario is presented.
Synthesis, structure and redox properties of single-atom bridged diuranium complexes supported by aryloxides
Authors: Hsueh Fang-Che , Barluzzi Luciano , Rajeshkumar Thayalan , Scopelliti Rosario , Zivkovic Ivica , Maron Laurent , Mazzanti Marinella
Published: July 2024

Reduction of the neutral UIV–X–UIV (X = O or S) complexes supported by aryloxide ligands yielded the UIV/UIII and UIII/UIII analogues. Notably, UIII–S–UIII is the first example of a U(iii) sulphide-bridged complex.
Sensitive determination of neodymium isotope in seawater by multi-collector inductively coupled plasma mass spectrometry with ultrasound nebulization-dielectric barrier discharge vapor generation as sample introduction
Authors: Li Dongyong , Cui Guanghao , Chen Shanshan , Qiao Yifan , Liu Qian , Zhang Jing , He Qian
Published: July 2024

A highly sensitive Nd isotopic analysis method by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with ultrasound nebulization-dielectric barrier discharge (UNDBD) vapor generation as sample introduction is developed.
Metal-free nitro/azido cyclization of 1-acryloyl-2-cyanoindoles to access NO2/N3-featuring pyrrolo[1,2-a] indolediones
Authors: Liu Huaqing , Yan Qinqin , Zeng Yanzhao , Hou Xinyi , Wang Ying , Li Lijun , Li Zejiang
Published: July 2024

A simple radical nitro/azide cyclization of 1-acryloyl-2-cyanoindoles produced diverse NO2/N3-featuring pyrrolo[1,2-a] indolediones.
How upper secondary students figure chemistry
Authors: Niemann Jonas , Holmegaard Henriette , Madsen Lene Møller
Published: July 2024

The formation of chemistry identities among students is closely linked to the norms and practices prevalent in their chemistry learning environments. However, these norms may not be equally accessible or aligned with formal assessment criteria, leading to disparities for students in cultivating a positive chemistry identity. This study investigates how students conceptualise chemistry and the opportunities it affords for identity formation. Drawing upon the theoretical frameworks of figured worlds and science identity, data were collected from 45 upper secondary school students across three Danish schools through classroom observations and focus groups. The findings reveal that students perceive the laboratory and classroom settings as distinct in purpose, nature, and relevance, with varying degrees of celebration for enacted performance in each. While work in and related to the laboratory is highly valued by both students and teachers, individual enacted performance in the classroom is often equated with proficiency in chemistry. However, implicit norms for example governing the division of labour in laboratories indicate an inequitable distribution of tasks and underscore the need for a more equitable approach to identity formation in chemistry education.
Structural determination of covalent organic frameworks through diffraction methods
Authors: Lin En , Wang Zhifang , Zhang Zhenjie
Published: July 2024

As an emerging crystalline porous material constructed from organic building blocks linked by covalent bonds, covalent organic frameworks (COFs) have garnered significant interest due to their well-defined pore structures.
Design and application of rhodamine derivatives in redox biology: a roadmap of the last decade towards artificial intelligence
Authors: Mondal Moumita , Das Riyanka , Pal Rajeshwari , Nag Somrita , Banerjee Priyabrata
Published: July 2024

Reactive sulfur, oxygen and nitrogen species (reactive SON species) are important topics in redox biology and their recognition by rhodamine-derived probes is impactful in the bio-medical research field.
Hydrogels: a promising therapeutic platform for inflammatory skin diseases treatment
Authors: Cao Huali , Wang Ming , Ding Jianwei , Lin Yiliang
Published: July 2024

Hydrogels revolutionize treating chronic skin diseases by enhancing drug delivery and reducing side effects. This review explores hydrogel design, drug integration, and clinical trials, highlighting their potential to improve efficacy and safety.
Photoluminescence study of perovskite materials derived from tungsten- and lanthanide-containing aurivillius layered perovskite, Bi2Na0.63Ln0.37Ta1.75W0.25O9
Authors: Awaya Keisuke , Yamamoto Ayaka , Hatakeyama Kazuto , Ida Shintaro
Published: July 2024

The structure and photoluminescence properties of a W-containing perovskite nanosheet derived from an Aurivillius phase layered perovskite Bi2Na0.63Ln0.37Ta1.75W0.25O9 (Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Sm, Dy, Ho, Er, Tm, and Yb) were investigated.
Advances in the structural basis for angiotensin-1 converting enzyme (ACE) inhibitors
Authors: Acharya K. Ravi , Gregory Kyle S. , Sturrock Edward D.
Published: July 2024

Human somatic angiotensin-converting enzyme (ACE) is a key zinc metallopeptidase that plays a pivotal role in the renin–angiotensin–aldosterone system (RAAS) by regulating blood pressure and electrolyte balance. Inhibition of ACE is a cornerstone in the management of hypertension, cardiovascular diseases, and renal disorders. Recent advances in structural biology techniques have provided invaluable insights into the molecular mechanisms underlying ACE inhibition, facilitating the design and development of more effective therapeutic agents. This review focuses on the latest advancements in elucidating the structural basis for ACE inhibition. High-resolution crystallographic studies of minimally glycosylated individual domains of ACE have revealed intricate molecular details of the ACE catalytic N- and C-domains, and their detailed interactions with clinically relevant and newly designed domain-specific inhibitors. In addition, the recently elucidated structure of the glycosylated form of full-length ACE by cryo-electron microscopy (cryo-EM) has shed light on the mechanism of ACE dimerization and revealed continuous conformational changes which occur prior to ligand binding. In addition to these experimental techniques, computational approaches have also played a pivotal role in elucidating the structural basis for ACE inhibition. Molecular dynamics simulations and computational docking studies have provided atomic details of inhibitor binding kinetics and energetics, facilitating the rational design of novel ACE inhibitors with improved potency and selectivity. Furthermore, computational analysis of the motions observed by cryo-EM allowed the identification of allosteric binding sites on ACE. This affords new opportunities for the development of next-generation allosteric inhibitors with enhanced pharmacological properties. Overall, the insights highlighted in this review could enable the rational design of novel ACE inhibitors with improved efficacy and safety profiles, ultimately leading to better therapeutic outcomes for patients with hypertension and cardiovascular diseases.
Unraveling the untwisting process and upward mass transfer of a twisted prominence driven by vortex motion
Authors: Zhang X. F. , Zhou G. P. , Jin C. L. , Zhang Y. Z. , Li G. W. , Shang Z. H. , Li L. P. , Yang S. B. , Yang S. H. , Wang J. X.
Published: July 2024

Context. Solar filaments or prominences are common features in the Sun’s atmosphere that contain cool chromospheric material suspended within the hot corona. However, the intricate topology of these structures and the mechanisms driving their instability and upward material transfer are not well understood. Investigating these issues is essential for gaining insight into the fundamental laws that govern solar activity.

Aims. This study is to analyze a specific twisted prominence observed on February 10, 2021, and to explore its dynamics, including stability, motion, and material transfer. The study also aims to propose a mechanism, based on the Kármán Vortex Street instability, to explain the destabilization of the prominence.

Methods. The study utilizes high-resolution Hα observations from the 1-m New Vacuum Solar Telescope and space-borne observations from the Solar Dynamics Observatory. These observations capture the characteristics and behavior of the twisted prominence. We analyzed the data to investigate the equilibrium state, subsequent destabilization, vortex motion, oscillations, resonations, untwisting, and upward mass loading of the prominence. We also detected and measured the speeds of outflows surrounding the prominence.

Results. The study reveals that the observed twisted prominence exhibited a stretched and twisted structure at its apex, distinguishing it from familiar cloudy prominences. Following a period of more than 30 hours in equilibrium, the prominence underwent destabilization, leading to a series of dynamic phenomena, such as vortex motion, oscillations, resonations, untwisting, and the upward transfer of mass. Consequently, material from the top of the prominence was carried upward and deposited into the overlying magnetic arcades. Noteworthy, outflows surrounding the prominence were characterized by speeds exceeding 40 km s−1.

Conclusions. Based on these findings, we propose, for the first time, a mechanism rooted in the Kármán Vortex Street instability to explain the destabilization of the prominence. The estimated typical Strouhal Number of 0.23 ± 0.06, which is related to vortex shedding, falls within the expected range for the Kármán Vortex Street effect, as predicted by simulations. These discoveries provide new insights into the dynamics and fundamental topology of solar prominences and reveal a previously unknown mechanism for mass loading into the upper atmosphere.
Considering the incidence rate of RR Lyrae stars with non-radial modes
Authors: Netzel H. , Varga V. , Szabó R. , Smolec R. , Plachy E.
Published: July 2024

Context. Over recent years, additional low-amplitude non-radial modes have been detected in many first-overtone RR Lyrae stars. These non-radial modes form a characteristic period ratio with the dominant first overtone of around 0.61. The incidence rate of this phenomenon varies from population to population. It is also strongly dependent on the quality of the analyzed data. Current models aimed at explaining these additional signals involve non-radial modes of degrees of 8 and 9.

Aims. Using synthetic horizontal branch populations, we investigate the incidence rate of first-overtone RR Lyrae stars with non-radial modes, depending on the population properties, namely, ages and metallicities. We compare our results with the observed results for globular clusters and the vast collection of field first-overtone RR Lyrae stars to test the model predictions.

Methods. We used synthetic horizontal branches combined with pulsation models to predict how the incidence rate would depend on the age and metallicity of the population. To test whether the results based on synthetic horizontal branches are realistic, we compared them to incidence rates observed by TESS in first-overtone field RR Lyrae stars, using photometric metallicity values from a newly established calibration for TESS.

Results. The analysis of synthetic horizontal branches indicates that the incidence rate decreases with decreasing metallicity. We inferred the photometric metallicity for RR Lyrae stars observed by TESS and showed that the theoretical predictions are in agreement with the observations. Using the same method, we also concluded that the metallicity distribution of RR Lyrae stars showing an additional mode with a period-ratio around 0.68 appears to be different from that of 1) all first-overtone stars and 2) those showing additional non-radial modes.
Revisiting the massive star-forming complex RCW 122: New millimeter and submillimeter study
Authors: Duronea N. U. , Bronfman L. , Ortega M. , Suad L. A. , Baume G. , Mendoza E. , Carvajal M. , Cichowolski S. , Arnal E. M. , Finger R. , Merello M. , Gamen R.
Published: July 2024

In this paper, we present a new multifrequency study of the giant star-forming complex RCW 122. We used molecular data obtained with the ASTE 10 m and the APEX 12 m telescopes, along with infrared observations spanning from 3.6 µm to 870 µm, obtained from available databases. We also incorporated a range of public datasets, including the radio continuum at 3 GHz, narrowband Ha images, and deep JHK photometry. Our analysis focuses mostly on cataloged ATLASGAL sources, showcasing a spectrum of evolutionary stages from infrared dark cloud (IRDC)/high-mass protostellar object (HMPO) to ultra-compact HII region (UCHII), as inferred from preliminary inspections of the public dataset. Based on ASTE HCO+(4−3) and CO(3−2) data, we identified five molecular clumps, designated A, B, C, D, and E, as molecular counterparts of the ATLASGAL sources. These clumps have radial velocities ranging from ~−15 km s−1 to −10 km s−1, confirming their association with RCW 122. In addition, we report the detection of 20 transitions from 11 distinct molecules in the APEX spectra in the frequency ranges from 258.38 GHz to 262.38 GHz, 228.538 GHz to 232.538 GHz, and 218.3 GHz to 222.3 GHz, unveiling a diverse chemical complexity among the clumps. Utilizing CO(2−1) and C18O(2−1) data taken from the observations with the APEX telescope, we estimated the total LTE molecular mass, ranging from 200 M⊙ (clump A) to 4400 M⊙ (clump B). Our mid- to far-infrared (MIR-FIR) flux density analysis yielded minimum dust temperatures of 23.7 K (clump A) to maximum temperatures of 33.9 K (clump B), indicating varying degrees of internal heating among the clumps. The bolometric luminosities span 1.7×103 L⊙ (clump A) to 2.4×105 L⊙ (clump B), while the total (dust+gas) mass ranges from 350 M⊙ (clump A) to 3800 M⊙ (clump B). Our analysis of the molecular line richness, L/M ratios, and CH3CCH and dust temperatures reveals an evolutionary sequence of A/E→C→D/B, consistent with preliminary inferences of the ATLASGAL sources. In this context, clumps A and E exhibit early stages of collapse, with clump A likely in an early HMPO phase, which is supported by identifying a candidate molecular outflow. Clump E appears to be in an intermediate stage between IRDC and HMPO. Clumps D and B show evidence of being in the UCHII phase, with clump B likely more advanced. Clump C likely represents an intermediate stage between HMPO and HMC. Our findings suggest clump B is undergoing ionization and heating by multiple stellar and protostellar members of the stellar cluster DBS 119. Meanwhile, other cluster members may be responsible for ionizing other regions of RCW 122 that have evolved into fully developed HII regions, beyond the molecular dissociation stage.
XMM-Newton and NuSTAR discovery of a likely IP candidate XMMU J173029.8–330920 in the Galactic disc
Authors: Mondal Samaresh , Ponti Gabriele , Filor Luke , Bao Tong , Haberl Frank , Salcedo Ciro , Campana Sergio , Hailey Charles J. , Mori Kaya , Rea Nanda
Published: July 2024

Aims. We aim to characterise the population of low-luminosity X-ray sources in the Galactic plane by studying their X-ray spectra and periodic signals in the light curves.

Methods. We are performing an X-ray survey of the Galactic disc using XMM-Newton, and the source XMMU J173029.8–330920 was serendipitously discovered in our campaign. We performed a follow-up observation of the source using our pre-approved NuSTAR target of opportunity time. We used various phenomenological models in XSPEC for the X-ray spectral modelling. We also computed the Lomb-Scargle periodogram to search for X-ray periodicity. A Monte Carlo method was used to simulate 1000 artificial light curves in order to estimate the significance of the detected period. We also searched for X-ray, optical, and infrared counterparts of the source in various catalogues.

Results. The spectral modelling indicates the presence of an intervening cloud with NH ∼ (1.5 − 2.3)×1023 cm−2 that partially absorbs the incoming X-ray photons. The X-ray spectra are best fit by a model representing emission from a collisionally ionised diffuse gas with a plasma temperature of kT = 26−5+11 keV. Furthermore, an Fe Kα line at 6.47−0.06+0.13 keV was detected with an equivalent width of the line of 312 ± 104 eV. We discovered a coherent pulsation with a period of 521.7 ± 0.8 s. The 3–10 keV pulsed fraction of the source is around ∼50–60%.

Conclusions. The hard X-ray emission with plasma temperature kT = 26−5+11 keV, iron Kα emission at 6.4 keV, and a periodic behaviour of 521.7 ± 0.8 s suggest XMMU J173029.8–33092 to be an intermediate polar. We estimated the mass of the central white dwarf to be 0.94 − 1.4 M⊙ by assuming a distance to the source of ∼1.4 − 5 kpc.
A pilot study of Galactic radio recombination lines using FAST: Identification of diffuse ionized gas clumps and off-arm star-forming regions
Authors: Liu Bin , Wang Junzhi , Zhang Bo , Li Shanghuo , Liu Shu , Li Juan , Peng Bo , Fang Min , Mai Xiaofeng
Published: July 2024

Observing low-frequency decimeter hydrogen radio recombination lines (RRLs) with large single-dish telescopes, such as the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the L band, is a unique method for probing massive star formation on scales of hundreds of parsecs. This approach is particularly effective for detecting relatively weak and extended emissions from low-density gas ionized by massive stars. Deep, unbiased decimeter or centimeter RRL surveys with large single-dish telescopes can significantly enhance our understanding of the diffuse ionized gas along the Galactic plane. This, in turn, will improve our knowledge of the life cycle of matter in the interstellar medium and the dynamics of the Galaxy. In this context, we present a pilot project for such a blind L-band RRL survey targeting the Galactic plane and conducted using FAST. The results include the detection of RRL clumps and the identification of an off-arm active massive star-forming region near the Sagittarius-Carina arm. The ongoing and upcoming massive star formation in this region may be associated with the kink in the Sagittarius-Carina arm near 23° azimuth.
Metallicity distributions of halo stars: do they trace the Galactic accretion history?
Authors: Mori A. , Di Matteo P. , Salvadori S. , Khoperskov S. , Pagnini G. , Haywood M.
Published: July 2024

Context. The standard cosmological scenario predicts a hierarchical formation for galaxies. Many substructures have been found in the Galactic halo, usually identified as clumps in kinematic spaces, like the energy-angular momentum space (E − Lz), under the hypothesis that these quantities should be conserved during the interaction. If these clumps also feature different chemical abundances, such as the metallicity distribution function (MDF), these two arguments together (different kinematic and chemical properties) are often used to motivate their association with distinct and independent merger debris.

Aims. The aim of this study is to explore to what extent we can couple kinematic characteristics and metallicities of stars in the Galactic halo to reconstruct the accretion history of the Milky Way (MW). In particular, we want to understand whether different clumps in the E − Lz space with different MDFs should be associated with distinct merger debris.

Methods. We analysed dissipationless, self-consistent, high-resolution N-body simulations of a MW-type galaxy accreting a satellite with a mass ratio of 1:10, with different orbital parameters and different metallicity gradients, which were assigned a posteriori.

Results. We confirm that accreted stars from a ∼1:10 mass ratio merger event redistribute in a wide range of E and Lz, due to the dynamical friction process, and are thus not associated with a single region. Because satellite stars with different metallicities can be deposited in different regions of the E − Lz space (on average the more metal-rich ones end up more gravitationally bound to the MW), this implies that a single accretion of ∼1:10 can manifest with different MDFs, in different regions of the E − Lz space.

Conclusions. Groups of stars with different E, Lz, and metallicities may be interpreted as originating from different satellite galaxies, but our analysis shows that these interpretations are not physically motivated. In fact, as we show, the coupling of kinematic information with MDFs to reconstruct the accretion history of the MW can bias the reconstructed merger tree towards increasing the number of past accretions and decreasing the masses of the progenitor galaxies.
Towards characterising rocky worlds: Trends in chemical make-ups of M dwarfs versus GK dwarfs
Authors: Wang Haiyang S. , Quanz Sascha P. , Mahadevan Suvrath , Deal Morgan
Published: July 2024

Context. Elemental abundances of Sun-like stars have been shown to be crucial for understanding the detailed properties of planets surrounding them. However, accurately measuring elemental abundances of M stars, the most abundant class of stars in the solar neighbourhood, is challenging due to their faintness and pervasive molecular features in optical photospheric spectra. As a result, elemental abundances of Sun-like stars have been proposed to constrain those of M stars, particularly by scaling [X/H] given measured [Fe/H].

Aims. This work aims to test the robustness of this convenient practice based on two selected sets of M- and GK-dwarf stellar abundances and a set of rigorous statistical methods.

Methods. We compiled the elemental abundances of a sample of up to 43 M dwarfs for ten major rock-forming elements (Fe, C, O, Mg, Si, Al, Ca, Na, Ni, and Ti) from high-resolution near-infrared stellar surveys including APOGEE, CARMENES, and Subaru. We carried out bootstrap-based linear regressions on the selected sample of M dwarfs to constrain the statistical trends of [X/H] versus [Fe/H] and then compare them with those of GK dwarfs (sampled from the GALAH database). We then applied a two-sample, multivariate Mahalanobis Distance test to assess the significance of the differences in the [X/H]-[Fe/H] trends for individual elemental pairs between M and GK dwarfs.

Results. We find that the null hypothesis – that is, no significant difference in the chemical trends of [X/H] versus [Fe/H] between M and GK dwarfs – is strongly rejected for all elements except for Si, for which the rejection is marginal (p-value close to 0.05), and Na and Ni, for which the results are inconclusive. This finding suggests that assuming no difference may result in biased results, and thus inaccurate constraints on characterising rocky planets around M dwarfs by scaling the (unmeasured) chemical abundances of planet-hosting M dwarfs from the chemical trends of [X/H]–[Fe/H] determined by GK dwarfs.

Conclusions. It is therefore crucial for both the stellar and exoplanet communities to be aware of these observed differences. To better understand these differences, we advocate for dedicated modelling techniques for M-dwarf atmospheres and an increasing set of benchmark, homogeneous abundance analyses. Intermediately, our statistically constrained trends of [X/H]–[Fe/H] for M dwarfs provide a new constraint on estimating M-dwarf elemental abundances given measured [Fe/H] and further on characterising the detailed properties of M-dwarf-hosted rocky worlds.
A 260 pc resolution ALMA map of HCN(1–0) in the galaxy NGC 4321
Authors: Neumann Lukas , Bigiel Frank , Barnes Ashley T. , Gallagher Molly J. , Leroy Adam , Usero Antonio , Rosolowsky Erik , Bešlić Ivana , Boquien Médéric , Cao Yixian , Chevance Mélanie , Colombo Dario , Dale Daniel A. , Eibensteiner Cosima , Grasha Kathryn , Henshaw Jonathan D. , Jiménez-Donaire María J. , Meidt Sharon , Menon Shyam H. , Murphy Eric J. , Pan Hsi-An , Querejeta Miguel , Saito Toshiki , Schinnerer Eva , Stuber Sophia K. , Teng Yu-Hsuan , Williams Thomas G.
Published: July 2024

The property of star formation rate (SFR) is tightly connected to the amount of dense gas in molecular clouds. However, it is not fully understood how the relationship between dense molecular gas and star formation varies within galaxies and in different morphological environments. Most previous studies have typically been limited to kiloparsec-scale resolution such that different environments could not be resolved. In this work, we present new ALMA observations of HCN(1−0) at 260 pc scale to test how the amount of dense gas and its ability to form stars varies with environmental properties. Combined with existing CO(2−1) observations from ALMA and Hα from MUSE, we measured the HCN/CO line ratio, a proxy for the dense gas fraction, and SFR/HCN, a proxy for the star formation efficiency of the dense gas. We find a systematic > 1 dex increase (decreases) of HCN/CO (SFR/HCN) towards the centre of the galaxy, and roughly flat trends of these ratios (average variations < 0.3 dex) throughout the disc. While spiral arms, interarm regions, and bar ends show similar HCN/CO and SFR/HCN, on the bar, there is a significantly lower SFR/HCN at a similar HCN/CO. The strong environmental influence on dense gas and star formation in the centre of NGC 4321, suggests either that clouds couple strongly to the surrounding pressure or that HCN emission traces more of the bulk molecular gas that is less efficiently converted into stars. Across the disc, where the ISM pressure is typically low, SFR/HCN is more constant, indicating a decoupling of the clouds from their surrounding environment. The low SFR/HCN on the bar suggests that gas dynamics (e.g. shear and streaming motions) can have a large effect on the efficiency with which dense gas is converted into stars. In addition, we show that HCN/CO is a good predictor of the mean molecular gas surface density at 260 pc scales across environments and physical conditions.
Revealing the burning and soft heart of the bright bare active galactic nucleus ESO 141-G55: X-ray broadband and SED analysis
Authors: Porquet D. , Reeves J. N. , Hagen S. , Lobban A. , Braito V. , Grosso N. , Marin F.
Published: July 2024

Context. ESO 141-G55 is a nearby X-ray bright broad-line Seyfert 1 (BLS1) that has been classified as a bare active galactic nucleus (AGN) due to a lack of warm absorption along its line of sight, providing an unhampered view into its disc-corona system.

Aims. We aim to probe its disc-corona system thanks to the first simultaneous XMM-Newton and NuSTAR observation obtained October 1–2, 2022.

Methods. We carried out an X-ray broadband spectral analysis to determine the dominant process(es) at work as well as a spectral energy distribution (SED) analysis to determine the disc-corona properties.

Results. The simultaneous broadband X-ray spectrum of ESO 141-G55 is characterised by the presence of a prominent smooth soft X-ray excess, a broad Fe Kα emission line, and a significant Compton hump. The high-resolution reflection grating spectrometer spectra confirmed the lack of intrinsic warm-absorbing gas along our line of sight in the AGN rest frame, verifying that it is still in a bare state. However, soft X-ray emission lines were observed, indicating substantial warm gas out of our line of sight. The intermediate inclination of the disc-corona system (∼43°) may offer us a favourable configuration to observe ultra-fast outflows from the disc, but none were found in this 2022 observation, contrary to a previous 2007 XMM-Newton one. We ruled out relativistic reflection alone on a standard disc based on the X-ray broadband analysis, while a combination of soft and hard Comptonisation by a warm and hot corona (RELAGN) plus relativistic reflection (REFLKERRD) reproduces the ESO 141-G55 SED quite well. The hot corona temperature is very hot, ∼140 keV, and much higher than about 80% of AGNs, whereas the warm corona temperature, ∼0.3 keV, is similar to the values found in other sub-Eddington AGNs. ESO 141-G55 is accreting at a moderate Eddington accretion rate (∼10–20%).

Conclusions. Our analysis points to a significant contribution of an optically thick warm corona to both the soft X-ray and UV emission in ESO 141-G55, adding to the growing evidence that the accretion of AGNs (even at a moderate accretion rate) appears to deviate from standard disc theory.