bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of Coulomb interactions on acoustic oscillations in the outer layers of low-mass stars
Authors: Brito Ana , Lopes Fuentes Ilídio
Published: December 2024

As is well known, low-mass stars constitute the most abundant class of stars in our galaxy. In stars less massive than the Sun, the density within stellar interiors increases as the stellar mass decreases. Therefore, for low-mass stars, the significance of electrostatic effects in stellar interiors cannot be neglected, as these interactions can alter the properties of matter.

In our study, we focus on exploring the outer layers of stars less massive than the Sun. We have computed a range of stellar models, ranging from 0.4 to 0.9 solar masses, to investigate the effects of two physical processes on the acoustic oscillations in the envelopes of these stars: partial ionization of chemical elements and electrostatic interactions between particles in the outer layers. In addition to partial ionization, we demonstrate that Coulomb effects also influence the acoustic oscillation spectrum. Our investigation reveals the following findings:

1. Coulomb effects can indeed influence the acoustic oscillations in low-mass stars.

2. The model with a mass of inline1 serves as a transition point. For models less massive than inline1, their acoustic spectrum is more affected by electrostatic interactions, whereas models more massive than inline1 have their acoustic spectrum more impacted by partial ionization processes.

Our work unveils the promising possibilities that future discoveries related to the detection of solar-like oscillations in stars less massive than the Sun could offer in terms of understanding the connections between the internal structure of low-mass stars and their observable characteristics.
Chromosphere activity: relations with Solar cycles (SC)
Authors: Koutchmy S. , Tavabi E.
Published: December 2024

The study’s focus on the modulation of geomagnetism by low latitude solar magnetically activity, including coronal mass ejections (CMEs), solar flares, and solar energetic particles (SEPs). It mentions the Babcock–Leighton (B-L) dynamo model used to predict sunspot numbers in Solar Cycle 25 (SC25) and highlights the challenges in understanding aspects such as the regeneration of the poloidal field and the occurrence of magnetic regions, active longitudes, and coronal holes. The abstract introduces the study’s concentration on the activity of polar regions using chromosphere jets activity proxies and other parameters like polar faculae density and cool ejection events. It also mentions the observation of chromospheric prolateness during the minimum solar activity periods.
Near-surface shear layer of solar rotation: origin and significance
Authors: Kitchatinov Leonid L.
Published: December 2024

Helioseismology has discovered a thin layer beneath the solar surface where the rotation rate increases rapidly with depth. The normalized rotational shear in the upper 10 Mm of the layer is constant with latitude. Differential rotation theory explains such a rotational state by a radial-type anisotropy of the near-surface convection and a short correlation time of convective turbulence compared to the rotation period. The shear layer is the main driver of the global meridional circulation.
The near-surface shear layer (NSSL) of the Sun: a theoretical model
Authors: Choudhuri Arnab Rai , Jha Bibhuti Kumar
Published: December 2024

We present a theoretical model of the near-surface shear layer (NSSL) of the Sun. Convection cells deeper down are affected by the Sun’s rotation, but this is not the case in a layer just below the solar surface due to the smallness of the convection cells there. Based on this idea, we show that the thermal wind balance equation (the basic equation in the theory of the meridional circulation which holds inside the convection zone) can be solved to obtain the structure of the NSSL, matching observational data remarkably well.
Recent Developments in the Babcock–Leighton Solar Dynamo Theory
Authors: Karak Bidya Binay
Published: December 2024

Babcock–Leighton process, in which the poloidal field is generated through the decay and dispersal of tilted bipolar magnetic regions (BMRs), is observed to be the major process behind the generating poloidal field in the Sun. Based on this process, the Babcock–Leighton dynamo models have been a promising tool for explaining various aspects of solar and stellar magnetic cycles. In recent years, in the toroidal to poloidal part of this dynamo loop, various nonlinear mechanisms, namely the flux loss through the magnetic buoyancy in the formation of BMRs, latitude quenching, tilt quenching, and inflows around BMRs, have been identified. While these nonlinearities tend to produce a stable magnetic cycle, the irregular properties of BMR, mainly the scatter around Joy’s law tilt, make a considerable variation in the solar cycle, including grand minima and maxima. After reviewing recent developments in these topics, I end the presentation by discussing the recent progress in making the early prediction of the solar cycle.
Modelling the rotation dependence of cycle variability in sun-like stars: Answering why only slowly rotating stars produce grand minima
Authors: Vashishth Vindya
Published: December 2024

The Sun and solar-type stars exhibit irregular cyclic variations in their magnetic activity over long time scales. To understand this irregularity, we employed the flux transport dynamo models to investigate the behavior of one solar mass star at various rotation rates. To achieve this, we have utilized a mean-field hydrodynamic model to specify differential rotation and meridional circulation, and we have incorporated stochastic fluctuations in the Babcock–Leighton source of the poloidal field to capture inherent fluctuations in the stellar convection. Our simulations successfully demonstrated consistency with the observational data, revealing that rapidly rotating stars exhibit highly irregular cycles with strong magnetic fields and no Maunder-like grand minima. On the other hand, slow rotators produce smoother cycles with weaker magnetic fields, long-term amplitude modulation, and occasional extended grand minima. We observed that the frequency and duration of grand minima increase with the decreasing rotation rate. These results can be understood as the tendency of a less supercritical dynamo in slow rotators to be more prone to produce extended grand minima. We further explore the possible existence of the dynamo in the subcritical regime in a Babcock–Leighton-type framework and in the presence of a small-scale dynamo.
Large-scale electric currents in processes in the solar atmosphere
Authors: Fursyak Yu. A. , Abramenko V. I. , Kutsenko A. S. , Plotnikov A. A.
Published: December 2024

In the late 80s of the 20th century, Crimean astronomers, studying the structure of transverse magnetic fields in active regions (ARs), discovered signs of the presence of large-scale vertical electric currents – global electric currents (Abramenko, Gopasyuk 1987). In 2018–2020, we finalized and adapted the method for detecting large-scale electric currents to the data of modern instruments for studying the Sun, and began studying their dynamics on time scales of 3–5 days (Fursyak et. al 2020). Our researches carried out during 2020–2023 showed that: 1) Large-scale electric currents with values of the order of ~ 1013 A exist in ARs with nonzero flare activity. 2) Large-scale electric currents extend to the upper layers of the solar atmosphere in one part of the AR, and close through the chromosphere and corona in the remaining part of the AR. This assumption for the AR NOAA 12192 is confirmed by the results of numerical simulations performed in 2016 (Jiang et al. 2016). 3) The greater the magnitude of the large-scale electric current, the higher the probability of occurrence of M- and X- class solar flares in the AR. 4) At the final stages of AR evolution, a nonzero large-scale electric current can have a stabilizing effect on the sunspot, preventing its decay by its own magnetic field. 5) Large-scale electric currents are involved in coronal heating processes. Ohmic dissipation of a large-scale electric current is one of the mechanisms of quasi-stationary heating of coronal plasma above the AR. Our research on large-scale electric currents and the processes in which they take part continues.
Imaging stellar surface features with optical interferometry
Authors: Haubois X.
Published: December 2024

In this contribution, I present a selected overview of optical interferometry imaging results that brought insights on stellar activity and mass loss in evolved stars. I briefly introduce the STELLIM project that aims to characterize stellar surfaces and circumstellar environments by producing fast and reliable interferometric images.
Prognostic opportunity of the shifted correlation between Wolf numbers and their time derivatives
Authors: Starchenko S. V. , Yakovleva S. V.
Published: December 2024

We correlate the annual Wolf numbers W and their time derivatives Wʹ by shifting time fragments of W and Wʹ relative to each other. The most significant (up to 0.874) correlation is with 3 years shifts for fragments covering 14 years. For longer and shorter periods, the correlation coefficients 0.771–0.855 with 2–3 years shift. The most significant 9 years shift corresponds to -0.852/-0.824 anti-correlation coefficient for 14/11 years period. The other periods are less significant. To evaluate predictive estimates, we use the times series fragments of W shifted back into the past. A forecast can be made using the leading graphs based upon the derived calibration factor. Test calculations show that the most effective is the calibration factor calculated for changing the phase of the cycle. The best linear pairwise correlation coefficient of the approximation is 0.94.
On origin of active/inactive branches on moderate rotating solar analogs
Authors: Pipin Valery V.
Published: December 2024

The fast rotating solar analogs show a decrease of the dynamo period with an increase of the rotation rate for the moderate stellar rotation periods in the range between 10 and 25 days. Simultaneously, observations indicate two branches: the “in-active” branch stars shows short dynamo cycles and the active branch stars show the relatively long magnetic cycles. We suggest that this phenomenon can be produced by effect of the doubling frequency of the dynamo waves, which is due to excitation of the second harmonic. It is generated because of the nonlinear B2 effects in the large-scale dynamo.
Modeling line-of-sight magnetograms of emerging active regions
Authors: Poisson M. , López–Fuentes M , Mandrini C. H. , Grings F. , Démoulin P.
Published: December 2024

Active regions (ARs) appear in the solar atmosphere as a consequence of the emergence of magnetic flux ropes (FRs). Due to the presence of twist, the photospheric line-of-sight (LOS) magnetograms of emerging ARs show an elongation of the polarities known as magnetic tongues. These tongues can affect the estimation of tilt angles during their emergence phase. In this work, we propose a Bayesian method to model LOS magnetograms of emerging ARs using a half-torus twisted FR model. We apply this model to 21 emerging ARs observed during Solar Cycle 23. We find that the Bayesian method corrects the tilt when compared to other methods, removing the spurious rotation of the polarities produced by the retraction of the tongues during the emergence. We find a variation in Joy’s law with the stage of the AR emergence and the method used for its estimation.
Detecting coronal mass ejections with machine learning methods
Authors: Vida K. , Seli B. , Szklenár T. , Kriskovics L. , Görgei A. , Kövári Zs.
Published: December 2024

Flares on the Sun are often associated with ejected plasma: these events are known as coronal mass ejections (CMEs). These events, although are studied in detail on the Sun, have only a few dozen known examples on other stars, mainly detected using the Doppler-shifted absorption/emission features in Balmer lines and tedious manual analysis. We present a possibility to find stellar CMEs with the help of high-resolution solar spectra.
Recent Progress in Time–Distance Helioseismology: Meridional Circulation, Far-side Imaging, and Sunquakes
Authors: Chen Ruizhu , Zhao Junwei
Published: December 2024

Time–distance helioseismology uses solar surface Doppler observations to measure areas that are not directly observable, such as solar interior, far side, and sunquake sources. In this work, we briefly review recent advancements in time–distance helioseismology, focusing on meridional circulation measurements, far-side imaging, and sunquakes. Solar deep meridional flows are crucial for understanding the dynamics of the solar interior, but precise measurements of these flows are challenging. This review explores recent developments in this area, particularly highlighting new findings related to systematic effects that have long challenged meridional circulation determination. We also review recent progress in solar far-side imaging, which is useful in improving space weather forecasting. Recent developments in far-side imaging using time–distance techniques and Deep Learning are introduced. Additionally, we review a new approach in sunquake reconstruction by incorporating observation-based Green’s functions constructed by time–distance helioseismology.
Stellar activity in open clusters
Authors: Görgei A. , Vida K. , Seli B. , Kriskovics L.
Published: December 2024

Stellar activity depends on multiple parameters one of which is the age of the star. The members of open clusters are good targets to observe the activity at a given age of the stars since their ages are more precisely determined than that of field stars. Choosing multiple clusters, each with different age, gives us insight to the change in activity during the lifetime of stars. With the analysis of these stars we can also refine the parameters of gyrochronology (Barnes 2003), which is a method for estimating the age of low-mass, main sequence stars from their rotation periods.
Flux emergence simulation and coronal response at ephemeral region scale
Authors: Wang Zi–Fan , Cameron R. H.
Published: December 2024

Flux emergence at different spatial scales and with different amounts of flux has been studied using radiative magnetohydrodynamics (rMHD) simulations. We use the radiative MHD code MURaM to simulate the emergence of an untwisted magnetic flux tube of ephemeral region scale with a density nonuniformity into a background atmosphere with a small unipolar open field. We find that the tube rises to the photosphere, forming complex loop structures seen in synthetic Atmospheric Imaging Assembly(AIA) 171 Å images. The atmosphere reaches 105K at 3Mm above the surface. Our simulation provides a reference example of a less twisted ephemeral region emergence and the atmospheric response.
Predicting the Emergence of Solar Active Regions Using Machine Learning
Authors: Kasapis Spiridon , Kitiashvili Irina N. , Kosovichev Alexander G. , Stefan John T. , Apte Bhairavi
Published: December 2024

To create early warning capabilities for upcoming Space Weather disturbances, we have selected a dataset of 61 emerging active regions, which allows us to identify characteristic features in the evolution of acoustic power density to predict continuum intensity emergence. For our study, we have utilized Doppler shift and continuum intensity observations from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The local tracking of 30.66 × 30.66-degree patches in the vicinity of active regions allowed us to trace the evolution of active regions starting from the pre-emergence state. We have developed a machine learning model to capture the acoustic power flux density variations associated with upcoming magnetic flux emergence. The trained Long Short-Term Memory (LSTM) model is able to predict 5 hours ahead whether, in a given area of the solar surface, continuum intensity values will decrease. The performed study allows us to investigate the potential of the machine learning approach to predict the emergence of active regions using acoustic power maps as input.
Observational Study of Reynolds Stresses Associated with Solar Inertial Modes
Authors: Mandowara Yash , Bekki Yuto , Bogart Richard S. , Gizon Laurent
Published: December 2024

We study the m = 1 high-latitude inertial mode and its contribution to the latitudinal transport of the Sun’s angular momentum. Ring-diagram helioseismology applied to 5° tiles is used to obtain the horizontal flows near the surface of the Sun. Using 10 years of data from SDO/HMI, we report on the horizontal eigenfunction and Reynolds stress
$\[{Q_{\theta \phi }} = \langle {u'_\theta }{u'_\phi }\rangle \]$
for the m = 1 high-latitude inertial mode (frequency –86.3 nHz, critical latitudes ±58°). We find that Qθφ takes significant values above the critical latitude and is positive (negative) in the northern (southern) hemisphere, implying equatorward transport of angular momentum. The Qθφ peaks above latitude 70° with a value of 38 m2/s2.
Probing the superadiabaticity of the solar convection zone with inertial modes
Authors: Dey Prithwitosh , Bekki Yuto , Gizon Laurent
Published: December 2024

Our understanding of solar convection is incomplete. A crucial gap is the unknown superadiabaticity in the solar convection zone, δ = ▽–▽ad. Global modes of oscillations in the inertial frequency range are sensitive to δ and serve as a novel tool to explore solar convection. Here, we address the forward problem where the superadiabaticity δ(r) varies with radius. We solve the 2.5D eigenvalue problem, considering the linearized equations for momentum, mass and energy conservation with respect to a realistic solar model. We find that the frequency and eigenfunction of the m = 1 high-latitude mode are influenced by δ in the lower convection zone. Our prescribed setup suggests that the superadiabaticity in the lower half of the convection zone is below 2.4×10-7 to reach a qualitative agreement with the observed eigenfunction.
Solar Inertial Modes
Authors: Gizon Laurent , Bekki Yuto , Birch Aaron C. , Cameron Robert H. , Fournier Damien , Philidet Jordan , Lekshmi B. , Liang Zhi–Chao
Published: December 2024

The Sun’s global inertial modes are very sensitive to the solar differential rotation and to properties of the deep solar convection zone which are currently poorly constrained. These properties include the superadiabatic temperature gradient, the latitudinal entropy gradient, and the turbulent viscosity. The inertial modes also play a key role in controlling the Sun’s large-scale structure and dynamics, in particular the solar differential rotation. This paper summarizes recent observations and advances in the (linear and nonlinear) modeling of the solar inertial modes.
Bit efficiency of distributed- and collocated-massive MIMO base station systems in OTA measurement and simulation
Authors: Kaneko Tomoya , Kuwabara Toshihide , Tawa Noriaki , Maruta Yasushi
Published: December 2024

This paper presents the bit efficiency of 28 GHz digital beamforming in over-the-air (OTA) measurements and simulations for distributed massive multiple-input–multiple-output (D-MIMO) and collocated massive multiple-input–multiple-output (C-MIMO) systems, as well as simulations for a 3.75 GHz small-cell scenario. Under the condition that users are randomly located in the line of sight coverage indoor area and spatially selected from each other by the normalized zero-forcing method, the OTA measured D-MIMO system exhibits an average of 4–7 dB better signal-to-noise ratio compared to C-MIMO when the number of simultaneously connected users “K” approaches the number of transceivers “M.” This means that the D-MIMO system provides higher bit efficiency than the C-MIMO system when K/M is large. Furthermore, the D-MIMO 3.75 GHz simulation predicts a relatively approximate 30% higher maximum efficiency than C-MIMO due to the shorter average distances between user equipment and access points in the D-MIMO system. To the best of the author’s knowledge, an earlier version of this paper has been presented at the 53rd European Microwave Conference as a first report on the 28 GHz OTA measured bit efficiency between C-MIMO and D-MIMO, highlighting D-MIMO’s advantage.
Design of polarization reconfigurable Koch fractal antenna for S-and C-band applications
Authors: Patel Khushbu , Behera Santanu Kumar
Published: December 2024

In this research, a novel polarization reconfigurable fractal antenna with high gain is proposed for wideband applications. This antenna consists of a Koch curve based hexagonal ring patch, two Positive-Intrinsic-Negative (PIN) diodes, and partial ground. The patch is positioned on a Rogers RT/Duroid 5880 substrate (ϵr = 2.2) with overall dimensions 33 × 30 × 1.6 mm3. It has three frequency bands with three different cases i.e., case I, 3–7.91 (90%); case II, 3–7.73 (88.16%); and case III, 3.54–6.7 GHz (61.7%). As a result, the proposed antenna’s impedance bandwidth (IBW) offers constant wideband coverage ranging from 3–7.91 GHz (90%). The axial ratio bandwidth (ARBW) is below 3 dB over 3.6–6.9 (62.86%) and 3.33–7.14 GHz (72.78%) for LHCP (Case I) and RHCP modes (Case II), respectively. The value for LP mode (Case III) is 3.54–6.7 GHz (61.7%). A peak realized gains of 4.75, 5.07, and 3.8 dBi are achieved at 6.2, 6.3, and 6 GHz for Case I, Case II, and Case III, respectively. Both linear and circular polarization prototype was developed and the performance was verified through measurements. The design confirms good polarization-reconfigurable characteristics within the band of 3.91 – 7.91 GHz.
Social disconnectedness, subsequent medical conditions, and, the role of pre-existing mental disorders: a population-based cohort study
Authors: Laustsen L. M. , Lasgaard M. , Momen N. C. , Chen D. , Gradus J. L. , Grønkjær M. S. , Jensen M. M. , Plana-Ripoll O.
Published: December 2024

Aims

Individuals with diminished social connections are at higher risk of mental disorders, dementia, circulatory conditions and musculoskeletal conditions. However, evidence is limited by a disease-specific focus and no systematic examination of sex differences or the role of pre-existing mental disorders.

Methods

We conducted a cohort study using data on social disconnectedness (loneliness, social isolation, low social support and a composite measure) from the 2013 and 2017 Danish National Health Survey linked with register data on 11 broad categories of medical conditions through 2021. Poisson regression was applied to estimate incidence rate ratios (IRRs), incidence rate differences (IRDs), and explore sex differences and interaction with pre-existing mental disorders.

Results

Among 162,497 survey participants, 7.6%, 3.5% and 14.8% were classified as lonely, socially isolated and with low social support, respectively. Individuals who were lonely and with low social support had a higher incidence rate in all 11 categories of medical conditions (interquartile range [IQR] of IRRs, respectively 1.26–1.49 and 1.10–1.14), whereas this was the case in nine categories among individuals who were socially isolated (IQR of IRRs, 1.01–1.31). Applying the composite measure, the highest IRR was 2.63 for a mental disorder (95% confidence interval [CI], 2.38–2.91), corresponding to an IRD of 54 (95% CI, 47–61) cases per 10,000 person-years. We found sex and age differences in some relative and absolute estimates, but no substantial deviations from additive interaction with pre-existing mental disorders.

Conclusions

This study advances our knowledge of the risk of medical conditions faced by individuals who are socially disconnected. In addition to the existing evidence, we found higher incidence rates for a broad range of medical condition categories. Contrary to previous evidence, our findings suggest that loneliness is a stronger determinant for subsequent medical conditions than social isolation and low social support.

A preregistered analysis plan and statistical code are available at Open Science Framework (https://osf.io/pycrq).
Dyeing of synthetic fiber-based wool blended fabrics in supercritical carbon dioxide
Authors: Mousa Abdalla A. , Mohamed Fatma A. , Abd El-Megied Saadia A. , Youssef Yehya A.
Published: December 2024

Development of supercritical carbon dioxide (SC-CO2) dyeing technology for natural fabrics and their blended fabrics is essential for the textile industry due to environmental and economic considerations. Wool (W), polyester (PET) and nylon (N) fabrics and their wool/polyester (W/PET) and wool/nylon (W/N) blended fabrics were dyed in SC-CO2 medium with a synthesized reactive disperse dye containing a vinylsulphone (VS) reactive group, which behaves as a disperse dye for synthetic fibers and a reactive dye for protein fibers. The SC-CO2 dyeing performance of all fabrics was investigated in terms of color strength, fixation, colorimetric and fastness measurements and compared with the conventional aqueous dyeing method. The results obtained indicate that the VS reactive disperse dye structure and non-polar PET component mainly improved colour strength (K/S) values of the dyed PET fabric and W/PET blended fabrics in SC-CO2 compared with those in the aqueous medium. Also, SC-CO2 dyeing has a notable influence on a*, b* and C* values of the dyed PET, N and W/PET fabrics and showed that the uptake of the VS reactive disperse dye and their appearance colors are higher and more saturated than the aqueous dyed samples. The levelling and fastness properties of all dyed fabrics in SC-CO2 medium are similar to those obtained in the aqueous medium. It was observed that VS reactive disperse dye penetrates well into the PET fabric and is chemically bound with the W fabric using both SC-CO2 and aqueous media and did not display significant color difference (∆E) values of W, PET and W/PET fabrics even after 20 washing cycles. The study claims that the VS reactive disperse dye structure and dyed PET-based wool blended fabric are good candidates for industrially SC-CO2 dyeing technology.
Expression of concern: Structural, morphological, electrical, and dielectric properties of Na2Cu5(Si2O7)2 for ASSIBs
Authors: Ben Bechir Mohamed , Akermi Mehdi
Published: December 2024

Expression of concern for ‘Structural, morphological, electrical, and dielectric properties of Na2Cu5(Si2O7)2 for ASSIBs’ by Mohamed Ben Bechir et al., RSC Adv., 2024, 14, 9228–9242, https://doi.org/10.1039/D4RA01454E.
Development of circadian rhythms in mammalian systems
Authors: Lee Junghyun , Goker Sevde , Lim Sookkyung , Hong Christian I.
Published: December 2024

In mammals, molecular mechanisms of circadian rhythms involve a time-delayed negative feedback loop generating autonomous oscillations of ∼24 h. Most cell types in mammals possess circadian rhythms regulating temporal organization of cellular and physiological processes. Intriguingly, pluripotent stem cells do not possess circadian rhythms and oscillations arise after a defined period of differentiation. Previous studies demonstrated that post-transcriptional regulations of core clock components, CLOCK and PER2, play critical roles in inducing circadian rhythms. In this article, we review the development of circadian rhythms in mammalian systems and provide a theoretical understanding of potential mechanisms regulating the birth of circadian rhythms using mathematical modeling.
Aerosol light absorption alleviates particulate pollution during wintertime haze events
Authors: Wu Jiarui , Bei Naifang , Wang Yuan , Su Xiaoli , Zhang Ningning , Wang Lili , Hu Bo , Wang Qiyuan , Jiang Qian , Zhang Chenchong , Liu Yangfan , Wang Ruonan , Li Xia , Lu Yuxuan , Liu Zirui , Cao Junji , Tie Xuexi , Li Guohui , Seinfeld John
Published: December 2024

Aerosol light absorption has been widely considered as a contributing factor to the worsening of particulate pollution in large urban areas, primarily through its role in stabilizing the planetary boundary layer (PBL). Here, we report that absorption-dominated aerosol–radiation interaction can decrease near-surface fine particulate matter concentrations ([PM
2.5
]) at a large-scale during wintertime haze events. A “warm bubble” effect by the significant heating rate of absorbing aerosols above the PBL top generates a secondary circulation, enhancing the upward motion (downward motion) and the convergence (divergence) in polluted (relatively clean) areas, with a net effect of lowering near-surface [PM
2.5
]. Furthermore, aerosol absorption of ultraviolet-wave light effectively reduces the photolysis of chemical species, i.e., aerosol–photolysis interaction, hindering ozone formation, reducing atmospheric oxidizing capability, and suppressing secondary aerosol concentrations. Our model assessment reveals that the synergetic two effects decrease near-surface [PM
2.5
] by around 7.4%, so the presence of light-absorbing aerosols can considerably alleviate particulate pollution during wintertime haze events. Such negative feedbacks to the aerosol loading should be considered in weather/climate prediction and health assessment models.
Earliest evidence of sedentism in the Antilles: Multiple isotope data from Canímar Abajo, Cuba
Authors: Chinique de Armas Yadira , Hernández Godoy Silvia Teresita , Viera Sanfiel Luis M. , Buhay William M. , Laffoon Jason E.
Published: December 2024

The early populations that inhabited the Antilles were traditionally understood as highly mobile groups of hunters/fishers and gatherers. Although more recent data have demonstrated that some populations engaged in the production of domestic plants and cultivars, questions remain about other aspects of their lifeways, including whether the adoption of domesticates was accompanied by a decrease in residential mobility. The level of sedentism in a population is an instrumental variable to understand community social relations and complexity, adaptations, and lifeways. Here, we combined enamel strontium (
87
Sr/
86
Sr), oxygen (δ
18
O
en
), and carbon (δ
13
C
en
) isotopes of 44 human teeth from the site of Canímar Abajo—where the oldest human remains from the insular Caribbean have been reported—to examine the mobility patterns of early Antillean groups. In contrast with traditional narratives, the homogeneous strontium isotope values observed in most individuals from the older funerary area of the site (cal. BC 2237–790) were consistent with the pattern expected for a sedentary population subsisting primarily on local resources obtained close to the coast. The isotopic evidence reveals that between cal. AD 403–1282, the mound was reused for funerary practices by both local communities and nonlocal individuals. The evidence suggests that this period saw higher population mobility, with influxes of individuals from more distant locations and diverse dietary and burial traditions. The isotope results from Canímar Abajo provide the earliest isotopic evidence of populations with low-level residential mobility in the Antilles.
Comparing cooperative geometric puzzle solving in ants versus humans
Authors: Dreyer Tabea , Haluts Amir , Korman Amos , Gov Nir , Fonio Ehud , Feinerman Ofer
Published: December 2024

Biological ensembles use collective intelligence to tackle challenges together, but suboptimal coordination can undermine the effectiveness of group cognition. Testing whether collective cognition exceeds that of the individual is often impractical since different organizational scales tend to face disjoint problems. One exception is the problem of navigating large loads through complex environments and toward a given target. People and ants stand out in their ability to efficiently perform this task not just individually but also as a group. This provides a rare opportunity to empirically compare problem-solving skills and cognitive traits across species and group sizes. Here, we challenge people and ants with the same “piano-movers” load maneuvering puzzle and show that while ants perform more efficiently in larger groups, the opposite is true for humans. We find that although individual ants cannot grasp the global nature of the puzzle, their collective motion translates into emergent cognitive skills. They encode short-term memory in their internally ordered state and this allows for enhanced group performance. People comprehend the puzzle in a way that allows them to explore a reduced search space and, on average, outperform ants. However, when communication is restricted, groups of people resort to the most obvious maneuvers to facilitate consensus. This is reminiscent of ant behavior, and negatively impacts their performance. Our results exemplify how simple minds can easily enjoy scalability while complex brains require extensive communication to cooperate efficiently.
Family relations of Moche elite burials on the North Coast of Peru (~500 CE): Analyses of the Señora de Cao and relatives
Authors: Quilter Jeffrey , Harkins Kelly , Fanco Jordan Régulo , Marsh Erik , Prieto Gabriel , Verano John , LeBlanc Steven , Broomandkhoshbacht Nasreen , Krigbaum John , Fehren-Schmitz Lars
Published: December 2024

The Moche archaeological culture flourished along Peru’s North Coast between the 4th and 10th centuries CE and was characterized by a complex social hierarchy dominated by political and religious elites. Previous archaeological evidence suggests kinship was a key factor in maintaining political authority within Moche society. To test this hypothesis, we applied archaeological, genetic, and isotopic methods to examine familial relationships between six individuals, including the prominent Señora de Cao (
~500 CE
), buried together in a pyramid-like, painted temple, Huaca Cao Viejo, in the Chicama Valley, Peru. Our findings reveal that all six individuals were biologically related, with varying degrees of kinship. The Señora de Cao was interred with a sacrificed juvenile, identified as a possible niece, and at least one, and potentially two siblings and a grandparent in separate tombs nearby. One of the male siblings was accompanied in death by his sacrificed son. Isotopic analysis indicates that while most individuals had diets rich in maize and animal protein and spent their childhoods in or near the Chicama Valley, the sacrificed juvenile accompanying the Señora had a distinct diet and geographic origin. These results demonstrate that Moche elites were interred with family members, including some raised far from their parental homes. This supports the hypothesis that kinship was central to transmitting status and authority. Moreover, sacrificing family members to accompany deceased elites underscores the significance of ritual sacrifice in reinforcing familial ties and linking the deceased to both ancestors and the divine.
Artificial intelligence entropy generation modelling of steam turbine control valves at extremely low steam mass flow
Authors: Strušnik D. , Avsec J.
Published: December 2024

Technological and ecological environmental regulations in the EU are increasingly focused on reducing greenhouse gas emissions. Consequently, older coal-fired thermal power plants are being compelled to cease operations or switch to more environmentally friendly primary energy sources. By replacing coal technology with gas technology, the production of steam, which drives the existing steam turbine, is significantly reduced. The existing coal boiler is replaced with a heat recovery steam generator that utilises the exhaust heat from the gas turbine, thus reducing the nominal steam input to the steam turbine from 64 kg/s to only 10 kg/s. This raises doubts about the feasibility of retaining the existing steam turbine, which is designed for higher flows. To address this, a simulation model has been created using artificial intelligence and real process data. The model calculates entropy generation and consequently the loss of available work energy (exergy) at the inlet throttling valves of the steam turbine under extremely low flow conditions. The generated entropy is closely related to the losses of available work energy or exergy. The model results show that due to the extreme throttling of the steam passing through the inlet control valves, exergy losses can amount to up to 1.12 MW. This is work energy permanently lost, which could otherwise have been used for electricity production.
Thermoelectric properties of multifunctional metashale mortar with carbon fiber dust
Authors: Hotěk P , Fiala L
Published: December 2024

The ability of thermoelectric geopolymer mortars to convert waste heat into electrical energy significantly expands their potential in civil engineering applications. The effectivity of this conversion, expressed by the figure of merit (ZT), is positively influenced by three material parameters, high electrical conductivity, the Seebeck coefficient, and low thermal conductivity. Doping a typically nonconductive geopolymer matrix with electrically conductive admixtures (ECAs) positively influences electrical conductivity, which is an important presumption to gain energy harvesting function. The paper deals with the design and material characterization of geopolymer metashale mortar doped with 5 wt.% of carbon fiber dust (CFD), with special emphasis on the determination of thermoelectric properties. On the basis of the observed thermoelectric voltage, the Seebeck coefficient and the ZT were calculated and discussed.
Self-heating potential of metashale mortar doped with carbon fiber dust
Authors: Hotěk P , Fiala L
Published: December 2024

Geopolymers are a very promising candidate to replace cementitious composites due to their significantly lower environmental impact and their potential for application in the field of multifunctional materials. New functional properties such as self-heating thus increase the possibility for geopolymers to be used in so-called smart structures. The ability to self-heat is directly affected by the electrical properties of the composite The key factor are the electrically conductive pathways within the material, which form an electrically conductive network through which electric current flows. Enhancement of the electrical properties can be achieved by applying electrically conductive additives such as carbon fibre dust (CFD). This paper is focused on the material characterization and verification of the self-heating ability of a multifunctional geopolymer mortar with CFD admixture. The sample was tested in AC mode to avoid polarization of the electrodes. With the AC power supply set at 30 V (RMS), the maximum temperature rise at the bottom of the sample from 23 to 32.1 °C was achieved in approximately 2 hours and the power meter recorded a power value of 2.6 W.
Mechanical and physical properties of traditional porcelain doped with waste glass
Authors: Ondruška J , Stančík M
Published: December 2024

The paper studies the effect of successive heating and the addition of waste glass on the properties of a traditional porcelain mixture. The porcelain consisted of 50 wt.% kaolinitic clay, 25 wt.% feldspar, and 25 wt.% quartz, with feldspar being gradually replaced by waste glass in amounts ranging from 5 to 25 wt.%. The thermal behavior of the samples was analyzed through successive heating up to 1100°C, focusing on the physical and structural changes in kaolinite, including water loss, dehydroxylation, and sintering effects.
The Effect of Biomass-based Fly Ash on Properties of Cement Pastes
Authors: Pokorný J
Published: December 2024

Portland cement constitutes the traditional binding material which is beneficial due to its relatively high initial strength and good resistance against different surrounding conditions. Nevertheless, its production relates to negative aspects, such as habitat disruption, biodiversity loss and considerable carbon footprint. The inclusion of biomass-based fly ash (BA) serving like ordinary Portland cement (OPC) substitution on behaviour of cement pastes was examined in this paper. Physical and mechanical properties, and liquid water transport of cement pastes with 10 – 20 mass% of BA content and maintained w/c of 0.4 were evaluated and compared with reference plain paste. Obtained experiment results pointed out on the active pozzolanic character and partial filler effect of BA particles in the combination with OPC. However, the optimal substitution of OPC with BA up to 15 mass% helped to reduce liquid water transport and to improve mechanical resistance of produced pastes.
Diffusion coefficient measurement using Dynamic Vapour Sorption method
Authors: Slávik R
Published: December 2024

Dynamic vapour sorption method (DVS) represents modern technique investigating interactions between the vapour and solid-state objects. This paper looks deeper into determination of the diffusion coefficient. The diffusion coefficient has significant importance in many technical fields and accurate data are often missing. Determination of diffusion coefficient is based on simplified theories, but real-world experiments expose their limits. Applications of dynamic vapour sorption method is demonstrated in the experiment with wooden material. It shows some pitfalls though. Further considerations for improving the accuracy and removal of errors are discussed further.
Development of a field experimental test house to study heat transfer in bio-based materials with microencapsulated PCM
Authors: Cieślikiewicz Ł , Dietrich F , Brzyski P , Łapka P
Published: December 2024

This paper presents the development of an experimental test house for real-world measurements of heat transfer in a building composite of hemp shive and magnesium binder with microencapsulated phase change material (PCM) to increase the thermal mass of the building material and improve internal thermal comfort. The test house was developed as a small building erected from prefabricated three-layer blocks with dimensions of 600×400×240 mm3 (length × width × height). The outer layers of the blocks had a density of approximately 400-450 kg/m3 and a thickness of 50 mm (without PCM) and 60 mm (with PCM), while the inner layer had a density of approximately 200-250 kg/m3 and a thickness of 290 mm. The building had dimensions of 2.60×3.10 m2 and a height of 3.36 m, with walls facing in the cardinal directions. A door was placed in the north wall. The east and south walls had a layer of PCM facing outwards, while the west wall faced inwards. The temperature inside the building was stabilized at 20°C using a specially designed heating/cooling system. Six temperature and relative humidity sensors (HDC 1080) were placed inside the two blocks in each wall, except the north wall. In addition, heat flux sensors were mounted under the internal plaster on the east and south walls. Indoor and outdoor air parameters, solar radiation, and wind speed were also monitored. In addition to the description of the test house, exemplary data for two measurements over a period of one week in two different months are discussed.
Possibilities of recycling of sideritic tailings in steel industry
Authors: Bobora A , Socalici A , Budiul Berghian A , Ardelean M , Birtok Baneasa C
Published: December 2024

In the context of the circular economy, the production of steel in electric arc furnaces is very well integrated. The promotion of recycling technologies that lead to improved product quality and the expansion of the raw and auxiliary material bay facilitates the closure of the recycling loop. The processing of powdered waste is the set of technological operations through which they are processed for their use under the conditions required by the beneficiaries. The paper presents a technological solution for valuing the sideritic tailings and the ferrous slats in the form of Carbofer by-product, usable in the steel industry when foaming slag in the electric arc furnace. Laboratory tests were carried out at the Faculty of Engineering Hunedoara using sterile sideritic recipes and iron steel sludge.
Microstructure analysis of non-metallic inclusions in continuous casted steels
Authors: Poenaru I O , Ardelean E
Published: December 2024

According to the current quality requirements in the steel production field, high purity of steel composition is required. For this reason, defect detection technology is developing significantly. The paper presents the analysis of 35 charges of continuous casted steel, highlighting the presence of defects by microstructure analyzing of non-metallic inclusions in the semi-finished steel composition. The purpose of using these products is the automotive industry, in the production of hydraulic cylinders. The quality of the steel is directly reflected in the quality of the final product, in the mechanical properties and the duration of the life cycle.
Understanding Flash Drought Dynamics: An Approach for Enhancing Sustainability in Resource Management
Authors: Lu Mengge , Sun Huaiwei , Qin Hui , Zhang Wenxin
Published: December 2024

Drought is a multifaceted phenomenon driven by both natural climate fluctuations and human activities. Unlike traditional, slow-developing droughts, flash droughts (FDs) emerge suddenly and intensify rapidly, posing significant challenges for natural resource management. The lack of effective tools to quantify FDs exacerbates stakeholders’ concerns, particularly due to the risks they pose to water management, food security, and environmental sustainability. Given their multifaceted nature, FDs evolve across both time and space, and traditional two-dimensional methods often fail to capture these dynamics. To address this issue, we developed a three-dimensional spatiotemporal framework for identifying flash droughts to analyse the spatial and temporal features and migration patterns of FDs. The results reveal that in China, flash droughts tend to migrate north and southeast, with this trend becoming increasingly pronounced as flash drought intensity increases. From 1982 to 2022, South China and Northwest China experienced significant increases in flash drought events. Flash droughts primarily occur during the growing season, with a rising proportion of events leading to heightened risks for crop yields and vegetation growth. Additionally, the percentage of flash droughts that begin within one pentad has significantly increased, indicating shorter onset times and an accelerated occurrence rate.
Determination of potential drought and frost resistance on the basis of studies with vegetative parts of plants of the genus Cercis L.
Authors: Babyn O , Pinchuk A , Derii A , Boyko O , Sovakov O
Published: December 2024

The role of green spaces in the urban system is important for creating a comfortable environment for the urban population. Most native species in urban environments have low resistance to pathogens and pests, due to the constant exposure to stressful abiotic and anthropogenic factors. Therefore, the issue of expanding the range of ornamental plants resistant to high temperatures, low moisture levels and the ability to withstand low winter temperatures is becoming relevant. The aim of the study was to determine the relative drought and frost resistance of plants of the genus Cercis L. by laboratory methods. In particular, determining the potential for drought tolerance by determining the level of vegetation, water yield per unit time, the level of water deficit of leaf blades and heat resistance, as well as determining frost resistance by laboratory freezing of annual shoots of experimental plants. These studies show that frost resistance and drought tolerance are closely related. Plants that had less drought tolerance eventually had a higher score of frost damage to shoot tissue. In our opinion, this is due to the fact that these species are more moisture-loving and their tissues are saturated with more moisture. It was found that drought tolerance varies not only between species, but also between cultivars of Cercis L. Thus, C. canadensis ‘Vanilla Twist’ had a higher level of frost resistance than C. canadensis ‘Ruby Falls’, but lower than Cercis canadensis L.