bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Rotation of the Solar Chromosphere using multidecadal Ca ii K Spectroheliograms
Authors: Mishra Dibya Kirti , Routh Srinjana , Jha Bibhuti Kumar , Chatterjee Subhamoy , Banerjee Dipankar 
Published: December 2024

AbstractThe study of the differential rotation in the chromosphere of the Sun is of significant importance as it provides valuable insights into the rotational behaviour of the solar atmosphere at higher altitudes and the coupling mechanism between the various layers of the solar atmosphere. In this work, we employed the image correlation technique, explicitly focusing on plages, intending to estimate the chromospheric differential rotation. For this purpose, we have utilized Ca ii K spectroheliograms (1907 – 2007) from the Kodaikanal Solar Observatory (KoSO), recently calibrated with a better technique to ensure accuracy. Our analysis indicates that plages in the chromosphere exhibit faster rotation and a smaller latitudinal gradient when compared to the rotation rate obtained through sunspot tracking. Furthermore, we investigate the temporal analysis of the chromospheric differential rotation parameters across various solar cycles.
Chromospheric activities of pre-main-sequence stars
Authors: Yamashita Mai , Itoh Yoichi , Takagi Yuhei , Oasa Yumiko 
Published: December 2024

AbstractWe investigated chromospheric activities of pre-main-sequence (PMS) stars. First, we studied the Ca II infrared triplet emission lines with Subaru/HDS and other spectroscopic instruments. Most PMS stars have narrow Ca II lines whose intensities are as large as the maximum of the zero-age main-sequence (ZAMS) stars. The chromosphere of PMS stars is suggested to be filled by the Ca II emitting region. Second, we found many faint chromospheric emission lines such as Mg I and Fe I for more than half of the ZAMS stars. Third, we searched the periodic light variation caused by a starspot for the 26 PMS stars. Their TESS light variations and Ca II emission line strengths show the positive correlation, and are located on the extensions of the superflare stars. In summary, PMS stars have very active chromosphere driven by strong dynamo process due to the fast rotation and the long convection timescale.
Rotational shear in the low photosphere of the Sun
Authors: Corbard T. , Faurobert M. , Gelly B. , Douet R. , Laforgue D. 
Published: December 2024

AbstractWe present a new method to measure the rotational height gradient in the solar photosphere. The method is inspired from differential interferometric techniques, we applied it to spectroscopic observations in the FeI 630.15 nm obtained at the solar telescope THEMIS which is equipped with an efficient adaptive optics system. The spectroscopic data was used to obtain images of the granulation at different line cords formed at different heights in the photosphere. Cross-correlation allows us to measure small systematic shifts between similar images. When observations are performed out of the center of the solar disk, the perspective effect gives rise to a radial shift between images formed at different heights. The measurement of this shift provides us with their formation-height difference. At the center of the disk the perspective effect vanishes but we measured a systematic retrograde shift along the east/west direction of the images formed at higher heights. The measured shifts are proportional to the formation height of the images. We interpret these findings as the evidence of a decrease of the rotational velocity with height in the low photosphere of the Sun and we give an estimate of this gradient.
Magnetic activity under tidal influences in the 2+2 hierarchical quadruple system V815 Herculis
Authors: Kövári Zs. , Strassmeier K. G. , Kriskovics L. , Oláh K. , Borkovits T. , Seli B. , Vida K. , Radványi Á. 
Published: December 2024

AbstractTidal forces in close binaries and multiple systems that contain magnetically active component are supposed to influence the operation of magnetic dynamo. Through synchronization the tidal effect of a close companion helps maintain fast rotation, thus supporting an efficient dynamo. At the same time, it can also suppress the differential rotation of the convection zone, or even force the formation of active longitudes at certain phases fixed to the orbit. V815 Her is a four-star system consisting of two close binaries orbiting each other, one of which contains an active G-type main-sequence star. Therefore, the system offers an excellent opportunity to investigate the influence of gravitational effects on solar-type magnetic activity using different methods.
Analyzing Magnetic Network and its Variations over Solar Cycles 23, 24 and 25 Based on Magnetic Power Spectra
Authors: Luo Yukun , Jiang Jie , Wang Ruihui 
Published: December 2024

AbstractThe magnetic network is a typical magnetic structure of the quiet Sun. Investigating its cycle dependence is crucial for understanding its evolution. We aim to identify and analyze the spatial scales of the magnetic network within magnetic power spectra derived from high-resolution Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) and Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic Imager (HMI) synoptic magnetograms. The data sets cover the entirety of solar cycles 23, 24, and part of cycle 25. We find that the identified magnetic network sizes identified range from 26 Mm to 41 Mm. There seems to be no obvious dependence on the solar cycle, and the sizes are distributed uniformly within the identification range.
A new generation of solar dynamo model and its application to explore the stellar magnetic cycle
Authors: Zhang Zebin 
Published: December 2024

AbstractIn most of the Babcock–Leighton (BL) type solar dynamo models, the toroidal magnetic field is assumed to be generated in the tachocline. However, magnetic activity of fully convective stars and MHD simulations of global stellar convection have recently raised serious doubts about the importance of the tachocline in the generation of the toroidal field. We have developed a BL-type dynamo model operating in the bulk of the convection zone, and are extending this model to solar-type stars. In this study, we aim at exploring how the starspot properties affect the stellar magnetic cycle. Observations show that faster rotating stars tend to have stronger magnetic activity and shorter magnetic cycles. By considering the higher latitudes and larger tilt angles of starspots for faster rotators, our simulations reproduce observations that faster rotating stars have shorter magnetic cycle and stronger activity.
Short and long term spot evolution on EI Eri
Authors: Kriskovics L. , Kövári Zs. , Seli B. , Oláh K. , Vida K. , Henry G. W. , Granzer T. , Görgei A. 
Published: December 2024

AbstractWe investigate flare activity using photometric data obtained with the Transiting Exoplanet Survey Satellite (TESS). Long-term seasonal period analysis was applied on our APT (Automatic Photoelectric Telescopes af Fairborn observatory, Arizona) time series to study changes in the rotational period. We also looked for activity cycle-like changes with short-term Fourier-transform. We also studied the phase and frequency distribution of hand-selected flares on the available TESS data. The MUlti-SIte Continuous Spectroscopy (MUSICOS) campaign was designed in 1998 to achieve high-resolution, multi-wavelength spectroscopic observations from many sites around the globe, which meant that uninterrupted phase coverage of EI Eri became available. We use these data to reconstruct successive surface-temperature maps of the star in order to study the changes of starspots on a very short timescale. We applied our multi-line Doppler imaging code to reconstruct four consecutive Doppler images. These images were also used to measure surface differential rotation with our cross-correlation technique.
A 2D model for the excitation of the linearly stable inertial modes of the Sun by turbulent convection
Authors: Philidet J. , Gizon L. 
Published: December 2024

AbstractThe newly discovered inertial modes in the Sun offer the opportunity to probe the solar convective zone down to the tachocline. While linear analysis predicts the frequencies and eigenfunctions of the modes, it gives no information about their excitation or their amplitudes. We present here a theoretical formalism for the stochastic excitation of the solar inertial modes by turbulent convection. The amplitudes predicted by our model are in complete agreement with observations, thus supporting the assumption that they are stochastically excited. Our work also uncovers a qualitative transition in the shape of the inertial mode spectrum, between m ≲ 5 where the modes are clearly resolved in frequency, and m ≳ 5 where the modes overlap. This complicates the interpretation of the high-m data, and suggests that a model for the whole shape of the power spectrum is necessary to exploit the full seismic potential of solar inertial modes.
Signature of local (turbulent) dynamo on middle and small scales
Authors: Abramenko V. I. 
Published: December 2024

AbstractThe solar dynamo is a physical process of magnetic field generation due to conversion of kinetic energy of plasma flows into magnetic energy. However, in the mean-field dynamo theory, one needs to segregate scales and consider separately large-scale dynamo and small-scale dynamo. The large-scale dynamo produces the large-scale mean field and unavoidable fluctuations of the mean field. Both are cycle-dependent. The small-scale dynamo is supposed to produce only the small-scale field, and this field is cycle-independent. There is no sharp boundary between the intervals of the large-scale and small-scale dynamos. An unavoidable presence of a smooth transition implies that there is a region where the properties of the large-scale global dynamo and fluctuations inherent to small-scale dynamo co-exist on some intermediate scales. Recent achievements in observations of the small-scale dynamo operation on the smallest observable scales and on the intermediate scales of typical active regions are discussed in the review.
Topological Features in the Emerging Solar Magnetic Flux
Authors: Roth Ilan 
Published: December 2024

AbstractThe formation of highly structured, spatially localized complex structures during solar flux emergence facilitates adaptation of topological methods, extending the research of emerging macroscopic MHD fluxes into knots, links and braids. Combining mathematical considerations, remote images and in situ satellite observations at solar vicinity, we construct new characteristics of those braided/knotted magnetic structures, applying Braid and Knot Theory to physical configurations, deducing their topological invariants, constraining the evolution and stability while delineating the relaxation path to magnetized equilibria.
The Impact and Sources of Radio Frequency Interference on GNSS Signals
Authors: Yizengaw Endawoke 
Published: December 2024

AbstractThe utilization of the global navigation satellite systems (GNSS) services in both military and civilian applications as well as for scientific investigation has grown exponentially. However, the increasing reliance on GNSS applications has raised concerns about potential risks from intentional radio frequency interference (RFI) transmitters. RFI significantly affects GNSS's environmental monitoring capabilities by inflating the scintillation index and misleading the scientific community with scintillation indices not attributable to ionospheric dynamic events. Consequently, the existing climatological distribution of GNSS scintillations may require careful reevaluation, as it may not adequately filter out RFI induced scintillations. Thus, characterizing the global RFI occurrence regions and developing real‐time detection capabilities to mitigate its effects is critically important. Leveraging GNSS measurements from ground stations and six COSMIC‐2 satellite constellations, we have developed a technique to detect RFI events and identify RFI active regions. Additionally, for the first time, we have implemented techniques that differentiate RFI associated scintillations from scintillations caused by ionospheric turbulence.
Paleo‐Suture Zone Disrupted by Thrusting: Example From East Junggar (NW China), Southern Altaids
Authors: Zhang Ji'en , Chen Yichao , Xiao Wenjiao , Wakabayashi John , Gan Jingmin , Tan Yiying , Zhao Yulong 
Published: December 2024

AbstractUnderstanding the tectonic evolution of ancient orogens relies on reconstructing the primary architecture of suture zones that may be modified by post‐subduction events. Modifications in East Junggar, southern Altaids, have led to controversial interpretations about the Paleozoic tectonic evolution. To clarify these relationships, we report the Mesozoic thrust horizon in East Junggar that has displaced the Baishanbao Klippe, which contains siltstone, sandstone, conglomerate and biogeographical Tuva‐Mongolia Tuvaella fauna. This klippe is distinct from units in the footwall that contain Ordovician‐Early Devonian accretionary complexes with dismembered basalts, cherts and deep marine tuffaceous siltstones, Carboniferous volcanic rocks and granites, Middle‐Late Jurassic sediments, and Kazakhstan biogeographic Ordovician‐Late Devonian coral‐brachiopod‐ammonoid fauna. The thrust horizon and the aforementioned units are unconformably capped by Late Jurassic‐Early Cretaceous alluvial fan deposits; it constrains the thrust to a Mesozoic age. These two biogeographic domains were separated by the Paleo‐Asian Ocean until the Late Paleozoic, as evidenced by the 478 Ma Kujibai MOR‐type ophiolite that involved into subduction zone in the Carboniferous. This Mesozoic thrust transported the Baishanbao Klippe for over 100 km southwards from its root in the Altay‐Fuyun area and crossed a cryptic suture zone of the Paleo‐Asian Ocean as an allochthonous unit in East Junggar. It extensively disrupted the primary Paleozoic orogenic architecture of East Junggar that leads to misinterpretation of the regional tectonic evolution. A lesson from disruption of this Mesozoic thrusting is that care must be taken in studies of the architecture of paleo‐suture zones.
Inter-chromosomal transcription hubs shape the 3D genome architecture of African trypanosomes
Authors: Rabuffo Claudia , Schmidt Markus R. , Yadav Prateek , Tong Pin , Carloni Roberta , Barcons-Simon Anna , Cosentino Raúl O. , Krebs Stefan , Matthews Keith R. , Allshire Robin C. , Siegel T. Nicolai 
Published: December 2024

AbstractThe eukaryotic nucleus exhibits a highly organized 3D genome architecture, with RNA transcription and processing confined to specific nuclear structures. While intra-chromosomal interactions, such as promoter-enhancer dynamics, are well-studied, the role of inter-chromosomal interactions remains poorly understood. Investigating these interactions in mammalian cells is challenging due to large genome sizes and the need for deep sequencing. Additionally, transcription-dependent 3D topologies in mixed cell populations further complicate analyses. To address these challenges, we used high-resolution DNA-DNA contact mapping (Micro-C) in Trypanosoma brucei, a parasite with continuous RNA polymerase II (RNAPII) transcription and polycistronic transcription units (PTUs). With approximately 300 transcription start sites (TSSs), this genome organization simplifies data interpretation. To minimize scaffolding artifacts, we also generated a highly contiguous phased genome assembly using ultra-long sequencing reads. Our Micro-C analysis revealed an intricate 3D genome organization. While the T. brucei genome displays features resembling chromosome territories, its chromosomes are arranged around polymerase-specific transcription hubs. RNAPI-transcribed genes cluster, as expected from their localization to the nucleolus. However, we also found that RNAPII TSSs form distinct inter-chromosomal transcription hubs with other RNAPII TSSs. These findings highlight the evolutionary significance of inter-chromosomal transcription hubs and provide new insights into genome organization in T. brucei.
Contributing factors to the oxidation-induced mutational landscape in human cells
Authors: Cordero Cameron , Mehta Kavi P. M. , Weaver Tyler M. , Ling Justin A. , Freudenthal Bret D. , Cortez David , Roberts Steven A. 
Published: December 2024

Abstract8-oxoguanine (8-oxoG) is a common oxidative DNA lesion that causes G > T substitutions. Determinants of local and regional differences in 8-oxoG-induced mutability across genomes are currently unknown. Here, we show DNA oxidation induces G > T substitutions and insertion/deletion (INDEL) mutations in human cells and cancers. Potassium bromate (KBrO3)-induced 8-oxoGs occur with similar sequence preferences as their derived substitutions, indicating that the reactivity of specific oxidants dictates mutation sequence specificity. While 8-oxoG occurs uniformly across chromatin, 8-oxoG-induced mutations are elevated in compact genomic regions, within nucleosomes, and at inward facing guanines within strongly positioned nucleosomes. Cryo-electron microscopy structures of OGG1-nucleosome complexes indicate that these effects originate from OGG1’s ability to flip outward positioned 8-oxoG lesions into the catalytic pocket while inward facing lesions are occluded by the histone octamer. Mutation spectra from human cells with DNA repair deficiencies reveals contributions of a DNA repair network limiting 8-oxoG mutagenesis, where OGG1- and MUTYH-mediated base excision repair is supplemented by the replication-associated factors Pol η and HMCES. Transcriptional asymmetry of KBrO3-induced mutations in OGG1- and Pol η-deficient cells also demonstrates transcription-coupled repair can prevent 8-oxoG-induced mutation. Thus, oxidant chemistry, chromatin structures, and DNA repair processes combine to dictate the oxidative mutational landscape in human genomes.
Analysis of the operation of a photovoltaic hybrid system
Authors: Soanda N I , Spunei E , Chioncel C P , Matasaru G S , Piroi F 
Published: December 2024

Abstract
Recently, there has been a significant surge in the utilization of renewable sources for generating electricity. This growth has been so rapid that it can be described as almost exponential. As a result, numerous entities and organizations have become energy prosumers. When a specific energy source is linked to the power grid and interconnected with another energy source, we speak of hybrid systems, and we know that hybrid systems’ behavior deviate from the behavior of each individual system connected to the network. This paper analyzes a case study consisting of three photovoltaic systems of different powers and with different equipment characteristics (two of them), connected both to the national electricity power-grid and a to a diesel-generator group. We examine the electricity generation and usage of the complete photovoltaic system throughout a one-year time span. Subsequently, we assess the impact of the hybrid system on the power network during notable fluctuations while in load operation mode. The analysis shows that, over the period of one year, the photovoltaic system provided for 32.31% of the industrial user’s energy consumption. Considering the energy injected into the grid, the energy generated by the photovoltaic system accounts for 42.21% of the user’s total energy usage. Upon reviewing the data, we found that the photovoltaic system linked to the grid fails to meet the necessary quality standards concerning fluctuations in voltage supply.
Spatial-temporal patterns of changes in PM 2.5 concentration in atmospheric air of Ivano-Frankivsk region
Authors: Adamenko S Y , Arkhypova L M , Adamenko Y O , Moskalchuk N M , Glibovytska N I 
Published: December 2024

Abstract
The update of WHO recommendations on air quality based on the latest evidence on the impact of PM on health prompts increased attention to ambient air monitoring and compliance with quality standards. Currently, a new system of state monitoring of atmospheric air is being formed in Ukraine. Control of the level of PM differentiated by size (except PM10 and PM2.5) is not yet conducted at most observation posts. Therefore, missing data from official sources were replaced by public monitoring data. The database for the study included measurements of PM10 and PM2.5 concentration from 4 Ecocity public monitoring stations located in areas with different types and levels of anthropogenic pressure (in the urbanized area in the central part of Ivano-Frankivsk, in the village of Bovshiv near the TPP, in the village of Broshniv-Osada near the woodworking enterprise and in the conditionally clean landscape and recreation area of the village of Mykulychyn). The general regularity of the diurnal trend of PM2.5 and PM10 concentration in the city of Ivano-Frankivsk is a sharp increase in concentration at night with a peak around midnight, a decrease during the day (minimum around 5:00 p.m.). The level of air pollution for PM2.5 and PM10 in the city center did not exceed the quality standards. The conclusion about the main contribution of anthropogenic sources of emissions is confirmed by the fact that the lowest level of PM2.5 was observed within the landscape and recreation area in the village of Mykulychyn, and the maximum peak values (up to 80 μg/m³) were observed at the station in the village of Bovshiv near Burshtynska TPP. A clear interdependence of PM10 and PM2.5 particles has been proven in all types of territories. Both indicators have similar daily trends. Functional dependences of PM2.5 concentration on PM10 were obtained for instantaneous, average hourly, average daily and average weekly values. In all cases, the coefficient of determination for regression models is greater than 0.9. These observations indicate that the sources and processes that influence daytime concentrations of PM2.5 and PM10 are similar or interrelated and warrant further investigation.
The influence of layer height and nozzle diameter on the strength of elements manufactured using FDM technology
Authors: Ziółkowski D , Maćkowiak P , Marzec M 
Published: December 2024

Abstract
In recent years, there has been a dynamic development of technology FDM (Fused Deposition Modeling). This has opened up new possibilities for manufacturing components, both prototypes and final devices in low-volume production. Due to this, in addition to visual values, the mechanical properties of the manufactured elements are also becoming crucial. The aim of this work is to analyze the influence of selected FDM process parameters such as nozzle diameter and layer height on mechanical properties. The obtained results will allow for a more informed selection of parameters and shortening of the production time. The first part describes the influence of individual parameters on the production time and strength based on a review of publications. The second part presents the method and results of three-point bending tests for specimens differing in layer height and nozzle diameter used to produce them using FDM technology. The tests performed allowed us to determine the effect of these parameters on the obtained mechanical properties.