bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic hydrogen shows its true colours: correlations between H i and galaxy colour in simulations
Authors: Osinga Calvin K , Diemer Benedikt , Villaescusa-Navarro Francisco , D’Onghia Elena , Timbie Peter
Published: April 2024

Intensity mapping experiments are beginning to measure the spatial distribution of neutral atomic hydrogen H i to constrain cosmological parameters and the large-scale distribution of matter. However, models of the behaviour of H i as a tracer of matter are complicated by galaxy evolution. In this work, we examine the clustering of H i in relation to galaxy colour, stellar mass, and H i mass in IllustrisTNG at z  = 0, 0.5, and 1. We compare the H i-red and H i-blue galaxy cross-power spectra, finding that H i-red has an amplitude 1.5 times greater than H i-blue at large scales. The cross-power spectra intersect at ≈3 Mpc in real space and ≈10 Mpc in redshift space, consistent with z ≈ 0 observations. We show that H i clustering increases with galaxy H i mass and depends weakly on detection limits in the range MH i ≤ 108 M⊙. In terms of M⋆, we find massive blue galaxies cluster more than less massive ones. Massive red galaxies, however, cluster the weakest amongst red galaxies. These opposing trends arise from central-satellite compositions. Despite these M⋆ trends, we find that the cross-power spectra are largely insensitive to detection limits in galaxy surveys. Counter-intuitively, all auto and cross-power spectra for red and blue galaxies and H i decrease with time at all scales. We demonstrate that processes associated with quenching contribute to this trend. The complex interplay between H i and galaxies underscores the importance of understanding baryonic effects when interpreting the large-scale clustering of H i, blue, and red galaxies at z ≤ 1.
Large-scale motions and growth rate from forward-modelling Tully–Fisher peculiar velocities
Authors: Boubel Paula , Colless Matthew , Said Khaled , Staveley-Smith Lister
Published: April 2024

Peculiar velocities are an important probe of the mass distribution in the Universe and the growth rate of structure, directly measuring the effects of gravity on the largest scales and providing a test for theories of gravity. Comparing peculiar velocities predicted from the density field mapped by a galaxy redshift survey with peculiar velocities measured using a distance estimator such as the Tully–Fisher relation yields the growth factor for large-scale structure. We present a method for forward modelling a sample of galaxy magnitudes and velocity widths that simultaneously determines the parameters of the Tully–Fisher relation and the peculiar velocity field. We apply this to the Cosmicflows-4 Tully–Fisher data set, using the peculiar velocities predicted from the 2M++ redshift survey. After validating the method on mock surveys, we measure the product of the growth rate and mass fluctuation amplitude to be fσ8 = 0.35 ± 0.03 at an effective redshift of z = 0.017. This is consistent at 3σ with the Planck CMB prediction, even though the uncertainty does not fully account for all sources of sample variance. We find the residual bulk flow from gravitational influences outside the 2M++ survey volume to be |V| = 227 ± 11 km s−1, (l, b)  =  (303°, −1°) in Galactic polar coordinates and the CMB frame. Using simulations, we show that applying our methodology to the large new sample of Tully–Fisher peculiar velocities expected from the WALLABY H I survey of the southern sky can improve the constraints on the growth rate by a factor of 2–3.
MUSE observations of small-scale heating events
Authors: Breu C A , De Moortel I , Testa P
Published: April 2024

Constraining the processes that drive coronal heating from observations is a difficult task due to the complexity of the solar atmosphere. As upcoming missions such as the Multi-slit Solar Explorer (MUSE) will provide coronal observations with unprecedented spatial and temporal resolution, numerical simulations are becoming increasingly realistic. Despite the availability of synthetic observations from numerical models, line-of-sight effects and the complexity of the magnetic topology in a realistic set-up still complicate the prediction of signatures for specific heating processes. 3D magnetohydrodynamic (MHD) simulations have shown that a significant part of the Poynting flux injected into the solar atmosphere is carried by small-scale motions, such as vortices driven by rotational flows inside intergranular lanes. MHD waves excited by these vortices have been suggested to play an important role in the energy transfer between different atmospheric layers. Using synthetic spectroscopic data generated from a coronal loop model incorporating realistic driving by magnetoconvection, we study whether signatures of energy transport by vortices and eventual dissipation can be identified with future missions such as MUSE.
Scaling relations for gamma-ray burst afterglow light curves and centroid motion independent of jet structure and dynamics
Authors: van Eerten Hendrik J , Ryan Geoffrey S
Published: April 2024

Models for gamma-ray burst afterglow dynamics and synchrotron spectra are known to exhibit various scale invariances, owing to the scale-free nature of fluid dynamics and the power-law shape of synchrotron spectra. Since GRB 170817A, off-axis jet models including a lateral energy structure in the initial outflow geometry have gained in prominence. Here, we demonstrate how the scale invariance for arbitrary jet structure and dynamical stage can be expressed locally as a function of jet temporal light-curve slope. We provide afterglow flux expressions and demonstrate their use to quickly assess the physical implications of observations. We apply the scaling expressions to the Swift X-ray Telescope sample, which shows a spread in observed fluxes, binned by light-curve slope at time of observation, that increases with increasing light-curve slope. According to the scaling relations, this pattern is inconsistent with a large spread in environment densities if these were the dominant factor determining the variability of light curves. We further show how the late deep Newtonian afterglow stage remains scale-invariant but adds distinct spectral scaling regimes. Finally, we show that for given jet structure a universal curve can be constructed of the centroid offset, image size, and ellipticity (that can be measured using very large baseline interferometry) versus observer angle, in a manner independent of explosion energy and circumburst density. Our results apply to any synchrotron transient characterized by a release of energy in an external medium, including supernova remnants, kilonova afterglows, and soft gamma-repeater flares.
Bridging theory and observations in stellar pulsations: the impact of convection and metallicity on the instability strips of classical and type-II cepheids
Authors: Deka Mami , Bellinger Earl P , Kanbur Shashi M , Deb Sukanta , Bhardwaj Anupam , Randall Hugh Riley , Kalici Selim , Das Susmita
Published: April 2024

The effect of metallicity on the theoretical and empirical period–luminosity relations of Cepheid variables is not well understood and remains a highly debated issue. Here, we examine empirical colour–magnitude diagrams (CMDs) of Classical and Type-II Cepheids in the Magellanic Clouds and compare those with the theoretically predicted instability strip (IS) edges. We explore the effects of incorporating turbulent flux, turbulent pressure, and radiative cooling into the convection theory on the predicted IS at various metallicities using Modules for Experiments in Stellar Astrophysics – Radial Stellar Pulsations. We find that the edges become redder with the increasing complexity of convection physics incorporated in the fiducial convection sets, and are similarly shifted to the red with increasing metallicity. The inclusion of turbulent flux and pressure improves the agreement of the red edge of the IS, while their exclusion leads to better agreement with observations of the blue edge. About 90 per cent of observed stars are found to fall within the predicted bluest and reddest edges across the considered variations of turbulent convection parameters. Furthermore, we identify and discuss discrepancies between theoretical and observed CMDs in the low-effective temperature and high-luminosity regions for stars with periods greater than ∼20 d. These findings highlight the potential for calibrating the turbulent convection parameters in stellar pulsation models or the prediction of a new class of rare, long-period, ‘red Cepheids’, thereby improving our understanding of Cepheids and their role in cosmological studies.
3D physical structure and angular expansion of the remnant of the recurrent nova T Pyx
Authors: Santamaría E , Toalá J A , Guerrero M A , Ramos-Larios G , Sabin L
Published: April 2024

We present the analysis of archival Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) and multi-epoch Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) and Wide Field Camera 3/Ultraviolet-Visible Imaging Spectrograph (WFC3/UVIS) narrow-band observations of the remnant associated with the ejecta of the mid-nineteenth century outburst of the recurrent nova T Pyx. These data sets are used to investigate its true three-dimensional (3D) physical structure and the nebular expansion patterns along the line of sight and on the plane of the sky. The VLT MUSE emission line maps and 3D visualizations based on position–position–velocity diagrams reveal T Pyx as a bipolar nebula, with a knotty toroidal structure at its waist best seen in H $\beta$ and two open bowl-shaped bipolar lobes (a diabolo) best revealed by the [O iii] emission lines. The comparison of multi-epoch HST WFPC2 and WFC3/UVIS narrow-band images and VLT MUSE emission-line maps of T Pyx reveals the angular expansion of the remnant through the proper motion of individual knots and nebular features. The angular expansion is confirmed to be homologous in the period from 1994.2 to 2007.4 before the recent 2011 outburst, but there is suggestive evidence that the inner knots have experienced a higher expansion rate since then.
Beyond radial profiles: using log-normal distributions to model the multiphase circumgalactic medium
Authors: Dutta Alankar , Bisht Mukesh Singh , Sharma Prateek , Ghosh Ritali , Roy Manami , Nath Biman B
Published: April 2024

Recent observations and simulations reveal that the circumgalactic medium (CGM) surrounding galaxies is multiphase, with the gas temperatures spanning a wide range at most radii, ∼104 K to the virial temperature (∼106 K for Milky Way). Traditional CGM models using simple density profiles are inadequate at reproducing observations that indicate a broad temperature range. Alternatively, a model based on probability distribution functions (PDFs) with parameters motivated by simulations can better match multiwavelength observations. In this work, we use log-normal distributions, commonly seen in the simulations of the multiphase interstellar and circumgalactic media, to model the multiphase CGM. We generalize the isothermal background model by Faerman et al. to include more general CGM profiles. We extend the existing probabilistic models from 1D-PDFs in temperature to 2D-PDFs in density–temperature phase space and constrain its parameters using a Milky Way-like Illustris TNG50-1 halo. We generate various synthetic observables such as column densities of different ions, UV/X-ray spectra, and dispersion and emission measures. X-ray and radio (Fast Radio Burst) observations mainly constrain the hot gas properties. However, interpreting cold/warm phase diagnostics is not straightforward since these phases are patchy, with inherent variability in intercepting these clouds along arbitrary lines of sight. We provide a tabulated comparison of model predictions with observations and plan to expand this into a comprehensive compilation of models and data. Our modelling provides a simple analytical framework that is useful for describing important aspects of the multiphase CGM.
Patient perspectives on ionising radiation exposure from computed tomography in Saudi Arabia: a knowledge and perception study
Authors: Alashban Yazeed , Alghamdi Sami A
Published: April 2024

The objective of this study was to evaluate patient knowledge and understanding of ionising radiation and dosage, as well as the accompanying risks related to computed tomography scans. A total of 412 outpatients who underwent computed tomography (CT) scans were surveyed to assess their understanding of radiation dose and exposure risks. CT was correctly classified as an ionising radiation by 56.8% of the respondents. More than half of the patients reported that a CT scan increases the probability of inducing cancer. Awareness of varying radiation doses in different CT exams was noted in 75.2% of patients, but only 21.4% reported having discussions with their physician about radiation dose. Gender, age and employment were significantly correlated with knowledge levels. The survey findings indicate a limited understanding of the hazards associated with ionising radiation used in CT scans, highlighting a need for increased awareness and education on radiation protection to ensure informed consent.
The burden of cardiovascular disease attributable to high dietary sodium intake in Australia between 1990 and 2019
Authors: Moreno Sebastian V. , Grimes Carley , Bolton Kristy A. , Uddin Riaz , Siopis George , Maddison Ralph , Islam Sheikh Mohammed Shariful
Published: May 2024

Background:

Diets high in sodium are associated with adverse cardiovascular outcomes. We aimed to quantify the burden of cardiovascular disease (CVD) attributable to high dietary sodium consumption in the Australian population.

Methods:

Using data from the Global Burden of Disease (GBD) 2019, we estimated the age-standardised rates (per 100 000 population) and the total numbers of years lived with a disability (YLDs), years of life lost (YLLs), disability-adjusted life years (DALYs), and deaths for CVD attributable to high sodium (≥1000 mg/day) consumption in the Australian population, by sex and age groups (≥25 years) between 1990 and 2019. The study compared Australian estimates with similar high-income countries (Group of 20 [G20] members).

Results:

From 1990 to 2019, the age-standardized rates of CVD deaths, DALYs, YLDs, and YLLs per 100 000 population in Australia attributable to high sodium decreased. However, between 2013 and 2019, the total number of CVD deaths increased, and the number of CVD YLDs increased exponentially for both sexes for the whole period between 1990 and 2019. Men had a two-fold higher rate for high sodium CVD burden, compared to females between 1990 to 2019. Individuals aged between 80 and 84 years had the highest rates of CVD burden during the same period; however, older age groups reported the greatest decline in CVD burden compared to young and middle-aged adults in Australia. The age-standardised rates for high sodium attributable CVD consistently contributed more towards DALYs than YLDs in 2019 for both sexes. When compared to G20 countries, Australians displayed the lowest age-standardized rates for CVD deaths, DALYs, YLDs, and YLLs alongside Turkey, France, and the United Kingdom in 2019.

Conclusion:

While age-standardized CVD burden attributable to high sodium consumption decreased for both sexes over the past 30 years, the total number of CVD deaths showed an increase between 2013 and 2019. This study underscores the need for sustained efforts to address the rising absolute number of CVD deaths, especially among men and older people, and emphasizes the importance of continued vigilance in monitoring and implementing strategies to reduce the impact of high sodium consumption on cardiovascular health in Australia.
Impact of seasonal blood pressure changes on visit-to-visit blood pressure variability and related cardiovascular outcomes
Authors: Mancia Giuseppe , Schumacher Helmut , Böhm Michael , Grassi Guido , Teo Koon K. , Mahfoud Felix , Parati Gianfranco , Redon Josep , Yusuf Salim
Published: May 2024

Background:

Visit-to-visit blood pressure (BP) variability associates with an increased risk of cardiovascular events. We investigated the role of seasonal BP modifications on the magnitude of BP variability and its impact on cardiovascular risk.

Methods:

In 25 390 patients included in the ONTARGET and TRANSCEND trials, the on-treatment systolic (S) BP values obtained by five visits during the first two years of the trials were grouped according to the month in which they were obtained. SBP differences between winter and summer months were calculated for BP variability quintiles (Qs), as quantified by the coefficient of variation (CV) of on-treatment mean SBP from the five visits. The relationship of BP variability with the risk of cardiovascular events and mortality was assessed by the Cox regression model.

Results:

SBP was approximately 4 mmHg lower in summer than in winter regardless of confounders. Winter/summer SBP differences contributed significantly to each SBP-CV quintile. Increase of SBP-CV from Q1 to Q5 was associated with a progressive increase in the adjusted hazard ratio (HR) of the primary endpoint of the trials, i.e. morbid and fatal cardiovascular events. This association was even stronger after removal of the effect of seasonality from the calculation of SBP-CV. A similar trend was observed for secondary endpoints

Conclusions:

Winter/summer SBP differences significantly contribute to visit-to-visit BP variability. However, this contribution does not participate in the adverse prognostic significance of visit-to-visit BP variations, which seems to be more evident after removal of the BP effects of seasonality from visit-to-visit BP variations.
Be a Champion! An Approach to Medical Emergency Response In Situ Simulations in the Outpatient Setting
Authors: Hemann Michele , Carver Rachel , Sanchez Anna , Carter Bridget , McGee Abbie
Published: May 2024

Results from a needs assessment conducted by nursing professional development practitioners across several clinics in the Midwest showed current educational methods to prepare for medical emergencies were insufficient. A champion model was used to complete in situ medical emergency response simulations. This proved to be an effective method for staff preparation when resources were limited and identified opportunities for practice improvement.
The Clinical Experience in Temporal Branch of Facial Nerve Transient Injury After Reduction Malarplasty
Authors: Gao Jiaman , Yu Zheyuan , Duan Huichuan , Jiang Taoran , Wei Min , Zhou Sizheng , Li Dong , Cao Dejun , Yuan Jie , Xu Liang
Published: May 2024

Purpose:

During reduction malarplasty using both intraoral and preauricular incisions, the operative exposure of the preauricular incision can result in injury of the temporal branch of the facial nerve, a potentially serious complication. The purpose of this study was to determine the relative frequency of this injury and investigate potential methods of prevention by analyzing the related anatomic and functional details of the patients that sustained temporal branch injury.

Methods:

The study comprised a retrospective review of 93 patients who underwent L-shaped reduction malarplasty with osteotomy using intraoral and preauricular incisions between December 2018 and February 2021. Specifically, this included all patients with transient dysfunction of the temporal branch of the facial nerve 1 week postoperatively, which recovered with conservative treatment.

Results:

In 4 of the 93 operated cases, the postoperative evaluation revealed that the forehead lines disappeared, there was a failure of eyebrow lifting, double eyelids remained unchanged in 3 cases and narrowed in 1, but eye closure was not affected. However, using only conservative treatment, the symptoms of all patients improved and recovered.

Conclusions:

To avoid the temporal branch of facial nerve injury during reduction malarplasty with intraoral and preauricular incisions, surgeons need to be especially familiar with the anatomy of the temporal branch of the facial nerve and proceed with precise, atraumatic dissection. However, if facial paralysis is diagnosed postoperatively, active treatment should be undertaken as soon as possible.

Level of Evidence:

Level IV
Drivers of Variation in Opioid Prescribing after Common Surgical Procedures in a Large Multihospital Healthcare System
Authors: Zanocco Kyle , Romanelli Robert J , Meeker Daniella , Mariano Louis T , Shenoy Rivfka , Wagner Zachary , Kirkegaard Allison , Mudiganti Satish , Martinez Meghan , Watkins Katherine E
Published: May 2024

BACKGROUND:

Misuse of prescription opioids is a well-established contributor to the US opioid epidemic. The primary objective of this study was to identify which level of care delivery (ie patient, prescriber, or hospital) produced the most unwarranted variation in opioid prescribing after common surgical procedures.

STUDY DESIGN:

Electronic health record data from a large multihospital healthcare system were used in conjunction with random-effect models to examine variation in opioid prescribing practices after similar inpatient and outpatient surgical procedures between October 2019 and September 2021. Unwarranted variation was conceptualized as variation resulting from prescriber behavior unsupported by evidence. Covariates identified as drivers of warranted variation included characteristics known to influence pain levels or patient safety. All other model variables, including prescriber specialty and patient race, ethnicity, and insurance status were characterized as potential drivers of unwarranted variation.

RESULTS:

Among 25,188 procedures with an opioid prescription at hospital discharge, 53.5% exceeded guideline recommendations, corresponding to 13,228 patients receiving the equivalent of >140,000 excess 5 mg oxycodone tablets after surgical procedures. Prescribing variation was primarily driven by prescriber-level factors, with approximately half of the total variation in morphine milligram equivalents prescribed observed at the prescriber level and not explained by any measured variables. Unwarranted covariates associated with higher prescribed opioid quantity included non-Hispanic Black race, Medicare insurance, smoking history, later hospital discharge times, and prescription by a surgeon rather than a hospitalist or primary care provider.

CONCLUSIONS:

Given the large proportion of unexplained variation observed at the provider level, targeting prescribers through education and training may be an effective strategy for reducing postoperative opioid prescribing.
Radiative loss and ion-neutral collisional effects in astrophysical plasmas
Authors: Popescu Braileanu Beatrice , Keppens Rony
Published: April 2024

In this paper, we study the role of radiative cooling (RC) in a two-fluid model consisting of coupled neutrals and charged particles. We first analyse the linearized two-fluid equations where we include radiative losses in the energy equation for the charged particles. In a one-dimensional geometry for parallel propagation and in the limiting cases of weak and strong coupling, it can be shown analytically that the instability conditions for the thermal mode and the sound waves, the isobaric and isentropic criteria, respectively, remain unchanged with respect to one-fluid radiative plasmas. For the parameters considered in this paper, representative for the solar corona, the RC produces growth of the thermal mode and damping of the sound waves. In the weak coupling limit, the growth of the thermal instability and the damping of the sound waves is as derived in Field (Field 1965
Astrophys. J.
142
, 531 (
doi:10.1086/148317
)) using the charged fluid properties. When neutrals are included and are sufficiently coupled to the charges, the thermal mode growth rate and the wave damping both reduce by the same factor, which depends on the ionization fraction only. For a heating function that is constant in time, we find that the growth of the thermal mode and the damping of the sound waves are slightly larger. The numerical calculation of the eigenvalues of the general system of equations in a three-dimensional geometry confirm the analytic results. We then run two-dimensional fully nonlinear simulations that give consistent results: a higher ionization fraction or lower coupling will increase the growth rate. The magnetic field contribution is negligible in the linear phase. Ionization-recombination effects might play an important role because the RC produces a large range of temperatures in the system. In the numerical simulation, after the first condensation phase, when the minimum temperature is reached, the fraction of neutrals increases four orders of magnitude because of the recombination.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Magnetoacoustic cutoff effect in numerical simulations of the partially ionized solar atmosphere
Authors: Kuźma Blazej , Kadowaki Luis H. S. , Murawski Kris , Musielak Zdzislaw E. , Poedts Stefaan , Yuan Ding , Feng Xueshang
Published: April 2024

The cutoff effect is a significant determinant of solar magnetohydrodynamic wave propagation and hence pivotal in energy transfer studies, such as solar plasma heating and seismological diagnostics. Despite continuous efforts, no good agreement between observed waveperiods and theory or numerical simulations was found. Our objective is to investigate the magnetoacoustic cutoff effect in the partially ionized solar atmosphere, factoring in the two-fluid effects. We developed a two-fluid MHD numerical model and used it to simulate a quiet region of the Sun from the top of the convective zone to the low corona. Our findings show that the ongoing granulation excites a wide range of waves propagating into the upper atmospheric layers. The cutoff waveperiods strongly depend on the height. Two-fluid waveperiods obtained with numerical simulations reproduce the recent observations at a very good level of compliance. Furthermore, direct comparison with strongly coupled cases that imitate the single-fluid approximation have shown that the waveperiod propagation pattern is only present in fully two-fluid simulations. We conclude that the presence of neutrals and therefore collisional terms change the dynamics of the magnetized plasma, in comparison with the single-fluid approximation. This effect is more prominently seen in the upper photosphere and chromosphere.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Alfvén pulse driven spicule-like jets in the presence of thermal conduction and ion-neutral collision in two-fluid regime
Authors: Srivastava A. K. , Singh Anshika , Singh Balveer , Murawski K. , Zaqarashvili T. V. , Yuan D. , Scullion E. , Mishra Sudheer K. , Dwivedi B. N.
Published: April 2024

We present the formation of quasi-periodic cool spicule-like jets in the solar atmosphere using 2.5-D numerical simulation in two-fluid regime (ions+neutrals) under the presence of thermal conduction and ion-neutral collision. The nonlinear, impulsive Alfvénic perturbations at the top of the photosphere trigger field aligned magnetoacoustic perturbations due to ponderomotive force. The transport of energy from Alfvén pulse to such vertical velocity perturbations due to ponderomotive force is considered as an initial trigger mechanism. Thereafter, these velocity perturbations steepen into the shocks followed by quasi-periodic rise and fall of the cool jets transporting mass in the overlying corona.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Nonlinear coupling of Alfvén and magnetoacoustic waves in partially ionized plasmas: the effect of thermal misbalance on propagating waves
Authors: Ballester J. L. , Soler R. , Terradas J. , Carbonell M.
Published: April 2024

Partially ionized plasmas constitute an essential ingredient of the solar atmosphere, and ground- and space-based observations have pointed out the presence of oscillations in partially ionized solar plasmas such as chromosphere, photosphere, prominences or spicules, which have been interpreted in terms of magnetohydrodynamic waves. Our aim is to study the spatial behaviour of propagating weakly and fully nonlinear Alfvén waves, and the subsequent excitation of field-aligned motions and perturbations, when dissipative mechanisms, such as ambipolar diffusion and radiative losses, together with parametrized heating mechanisms, are taken into account. When only ambipolar diffusion is taken into account, first-order Alfvén waves as well as ponderomotive-driven perturbations are spatially damped, while field-aligned motions and perturbations representing propagating slow waves are undamped. These perturbations are damped when thermal effects are also considered and their damping lengths can be longer or shorter than those of ponderomotive-driven perturbations. Therefore, after the initial excitation, Alfvén waves and ponderomotive-driven perturbations could be quickly damped while slow waves still remain in the plasma, and vice versa.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Magnetohydrodynamic waves in the partially ionized solar plasma
Authors: Soler Roberto
Published: April 2024

This paper provides a comprehensive review of recent theoretical investigations concerning magnetohydrodynamic (MHD) waves in partially ionized solar plasma. First, we examine the properties of linear MHD waves in a uniform partially ionized plasma and discuss the relevant effects arising from partial ionization. Subsequently, we delve into MHD wave studies in the more intricate settings of the lower solar atmosphere and solar prominences. These investigations involve topics such as MHD waves in magnetic flux tubes, wave excitation, linear and nonlinear mode coupling and wave heating. We outline new challenges that future research should tackle.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Future prospects for partially ionized solar plasmas: the prominence case
Authors: Parenti S. , Luna M. , Ballester J. L.
Published: April 2024

Partially ionized plasmas (PIP) constitute an essential ingredient of our plasma universe. Historically, the physical effects associated with partial ionization were considered in astrophysical topics such as the interstellar medium, molecular clouds, accretion disks and, later on, in solar physics. PIP can be found in layers of the Sun’s atmosphere as well as in solar structures embedded within it. As a consequence, the dynamical behaviour of these layers and structures is influenced by the different physical effects introduced by partial ionization. Here, rather than considering an exhaustive discussion of partially ionized effects in the different layers and structures of the solar atmosphere, we focus on solar prominences. The reason is that they represent a paradigmatic case of a partially ionized solar plasma, confined and insulated by the magnetic field, constituting an ideal environment to study the effects induced by partial ionization. We present the current knowledge about the effects of partial ionization in the global stability, mass cycle and dynamics of solar prominences. We revise the identified observational signatures of partial ionization in prominences. We conclude with prospects for PIP research in prominences, proposing the path for advancing in the prominence modelling and theory and using new and upcoming instrumentation.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Parametric resonance of Alfvén waves driven by ionization-recombination waves in the weakly ionized solar atmosphere
Authors: Ballai I. , Forgács-Dajka E. , McMurdo M.
Published: April 2024

Parametric coupling of waves is one of the most efficient mechanisms of energy transfer that can lead to the growth or decay of waves. This transfer occurs at frequencies close to their natural frequencies. In partially ionized solar plasma, there are a multitude of waves that can undergo this process. Here, we study the parametric coupling of Alfvén waves propagating in a partially ionized solar plasma with ionization-recombination waves identified by our study to appear in a plasma in ionization non-equilibrium. Depending on the parameters that describe the plasma (density, temperature), coupling can lead to a parametric resonance. Our study determines the occurrence conditions of parametric resonance, by finding the boundaries between stable and unstable regions in the parameter space. Our results show that collisions and non-equilibrium recombination can both contribute to the onset of unstable behaviour of parametrically resonant Alfvén waves.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Kelvin–Helmholtz-induced mixing in multi-fluid partially ionized plasmas
Authors: Snow Ben , Hillier Andrew S.
Published: April 2024

Turbulence is a fundamental process that drives mixing and energy redistribution across a wide range of astrophysical systems. For warm (

T
≈

10
4

 

K

) plasma, the material is partially ionized, consisting of both ionized and neutral species. The interactions between ionized and neutral species are thought to play a key role in heating (or cooling) of partially ionized plasmas. Here, mixing is studied in a two-fluid partially ionized plasma undergoing the shear-driven Kelvin–Helmholtz instability to evaluate the thermal processes within the mixing layer. Two-dimensional numerical simulations are performed using the open-source (PIP) code that solves for a two-fluid plasma consisting of a charge-neutral plasma and multiple excited states of neutral hydrogen. Both collisional and radiative ionization and recombination are included. In the mixing layer, a complex array of ionization and recombination processes occur as the cooler layer joins the hotter layer, and vice versa. In localized areas of the mixing layer, the temperature exceeds the initial temperatures of either layer with heating dominated by collisional recombinations over turbulent dissipation. The mixing layer is in approximate ionization-recombination equilibrium, however the obtained equilibrium is different to the Saha–Boltzmann local thermal equilibrium. The dynamic mixing processes may be important in determining the ionization states, and with that intensities of spectral lines, of observed mixing layers.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
The influence of thermal pressure gradients and ionization (im)balance on the ambipolar diffusion and charge-neutral drifts
Authors: Gómez Míguez M. M. , Martínez Gómez D. , Khomenko E. , Vitas N.
Published: April 2024

Solar partially ionized plasma is frequently modelled using single-fluid (1F) or two-fluid (2F) approaches. In the 1F case, charge-neutral interactions are often described through ambipolar diffusion, while the 2F model fully considers charge-neutral drifts. Here, we expand the definition of the ambipolar diffusion coefficient to include inelastic collisions (ion/rec) in two cases: a VAL3C one-dimensional model and a 2F simulation of the Rayleigh–Taylor instability (RTI) in a solar prominence thread based on [Lukin
et al.
2024
Phil. Trans. R. Soc. A
382
, 20230417. (
doi:10.1098/rsta.2023.0417
)]. On one side, we evaluate the relative importance of the inelastic contribution, compared to elastic and charge-exchange collisions. On the other side, we compare the contributions of ion/rec, thermal pressure, viscosity and magnetic forces to the charge-neutral drift velocity of the turbulent flow of the RTI. Our analysis reveals that the contribution of inelastic collisions to the ambipolar diffusion coefficient is negligible across the chromosphere, allowing the classical definition of this coefficient to be safely used in 1F modelling. However, in the transition region, the contribution of inelastic collisions can become as significant as that of elastic collisions. Furthermore, we ascertain that the thermal pressure force predominantly influences the charge-neutral drifts in the RTI model, surpassing the impact of the magnetic force.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
On the ambipolar diffusion formulation for ion-neutral drifts in the non-negligible drift velocity limit
Authors: Hillier Andrew S.
Published: April 2024

The ambipolar diffusion approximation is used to model partially ionized plasma dynamics in a single-fluid setting. To correctly apply the commonly used version of ambipolar diffusion, a set of criteria should be satisfied including the requirement that the difference in velocity between charges and neutral species (known as drift velocity) is much smaller than the thermal velocity, otherwise the drift velocity will drive a non-negligible level of further collisions between the two species. In this paper, we explore the consequences of relaxing this assumption. We show that a new induction equation can be formulated without this assumption. This formulation reduces to the ambipolar induction equation in the case the drift velocity is small. In the large drift velocity limit, the feedback of the drift velocity on the collision frequency results in decreased diffusion of the magnetic field compared with the standard ambipolar diffusion approximation for the same parameters. This has a natural consequence of reducing the frictional heating that can occur. Applying this to results from flux emergence simulations where the expansion of the magnetic field leads to strong adiabatic cooling of the partially ionized chromosphere resulted in a noticeable reduction in the magnitude of the predicted drift velocities.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Mixing, heating and ion-neutral decoupling induced by Rayleigh–Taylor instability in prominence-corona transition regions
Authors: Lukin Vyacheslav S. , Khomenko Elena , Popescu Braileanu Beatrice
Published: April 2024

This study explores nonlinear development of the magnetized Rayleigh–Taylor instability (RTI) in a prominence-corona transition region. Using a two-fluid model of a partially ionized plasma, we compare RTI simulations for several different magnetic field configurations. We follow prior descriptions of the numerical prominence model (Popescu Braileanu
et al.
2021
Astron. Astrophys.
646
, A93 (
doi:10.1051/0004-6361/202039053
), Popescu Braileanu
et al.
2021
Astron. Astrophys.
650
, A181 (
doi:10.1051/0004-6361/202140425
) and Popescu Braileanu
et al.
2023
Astron. Astrophys.
670
, A31 (
doi:10.1051/0004-6361/202142996
)) and explore the charged-neutral fluid coupling and plasma heating in a two-dimensional mixing layer for different magnetic field configurations. We also investigate how the shear in magnetic field surrounding a prominence may impact the release of the gravitational potential energy of the prominence material. We show that the flow decoupling is strongest in the plane normal to the direction of the magnetic field, where neutral pressure gradients drive ion-neutral drifts and frictional heating is balanced by adiabatic cooling of the expanding prominence material. We also show that magnetic field within the mixing plane can lead to faster nonlinear release of the gravitational energy driving the RTI, while more efficiently heating the plasma via viscous dissipation of associated plasma flows. We relate the computational results to potential observables by highlighting how integrating over under-resolved two-fluid sub-structure may lead to misinterpretation of observational data.

This article is part of the theme issue ‘Partially ionized plasma of the solar atmosphere: recent advances and future pathways’.
Gravitational effect on the cell in bio-fluid suspension
Authors: Murali Anirudh , Sarkar Ram Rup
Published: April 2024

The fascination with space and human spaceflight has significantly increased in recent years. Nevertheless, microgravity has a significant impact on humans. Immune and red blood cells utilize hematic or lymphatic streams (bio-fluid) as their primary mode of transport, and these streams have been identified as a significant concern under microgravity. This study aims to quantitatively address the puzzle of how cells are influenced by gravity when they are suspended in bio-fluid. The Dissipative Particle Dynamics (DPD) approach was used to model blood and the cell by applying gravity as an external force along the vertical axis and varied from 0g to 2g during parameter sweeps. It was observed that the cell undergoes shape change and spatially aligns under the influence of gravity, and this was quantified with metrics such as Elongation and Deformation indices, pitch angle, and normalized center of mass. The Elongation Index and the normalized center of mass declined linearly with the applied gravity. Correlation analysis showed a strong correlation between applied gravity and the aforementioned variables. Forces exerted on the solid, specifically drag, shear stress, and solid forces, declined in magnitude as the gravitational force exerted on the cell was increased. Further analysis showed that increasing gravity affected the cell’s velocity, leading to extended proximity near the wall and increased viscous interaction with the surrounding fluid particles, triggering a shape change. This study marks a significant step in understanding gravity’s effects on blood cells.
Premature thymic involution in youngFoxn1laczmutant mice causes peripheral T cell phenotypes similar to aging-induced immunosenescence
Authors: Xiao Shiyun , Kang Seung Woo , Oliva Kimberly E. , Zhang Wen , Klonowski Kimberly D. , Manley Nancy R.
Published: April 2024

The thymus is a primary lymphoid organ generating self-restricted and self-tolerant naïve T-cells. Early in life the thymus starts to involute, resulting in decreased naïve T-cell output which may be more self-reactive, leading to an increased prevalence of autoimmunity. A decrease in the transcription factor FOXN1 is an early event in thymic involution. Using theFoxn1laczmodel, we studied how premature thymic involution affects the thymic microenvironment, thymocytes, and peripheral T cell immunity. We found that early thymic involution led to aged-like thymic epithelial cells that resulted in aged-like thymocyte phenotypes, with a significant decrease in CD4+ single-positive T-cells. We also observed severe lymphopenia inFoxn1laczmice caused by the premature decrease in T-cell production, resulting in a peripheral T-cell phenotype similar tode novoaged peripheral T-cells. Moreover, following T cell receptor stimulation,Foxn1laczperipheral T cells had reduced IL-2 secretion and strong initial IFN-g responses, resembling aged wild-type peripheral T-cell responses. Lastly, influenza response inFoxn1laczhad a reduction in some aspects of T cell responses to influenza infection, similar to thymectomized mice. Our study shows an independent and direct impact of premature thymic involution on both thymopoiesis and peripheral immune niches likely contributing to immunosenescence and inflammaging as observed in the elderly population.
Rapid Response of Neutrophils Determined by Shortest Differentiation Trajectory and New Insight into Cell Cycle Kinetics and Chronological Order of Progenitor States
Authors: Yue Yongjian
Published: April 2024

Despite substantial advances in our understanding of hematopoietic stem cell self-renewal, differentiation, and proliferation, the underlying mechanisms and cell cycle kinetics remain elusive. Neutrophils, as primary rapid responders during infections, quickly generate an enormous number of mature cells for immune defense. This immune phenomena is effected by cell cycle kinetics. Our previous study redefined progenitors and reformed the hierarchy of hematopoiesis. Here, we aim to elucidate the cell cycle kinetics and chronological order of progenitor states, providing new insights into immune phenomena. We revealed the changes in cell cycle kinetics from differentiation (lineage commitment) to proliferation in peripheral hematopoiesis. Differentiating hematopoietic progenitor cells (HPCs) are maintained in the G1 phase of cell cycle, regulated by DNA replication. Once the progenitors complete their commitment, cell cycle states of progenitors convert from G1 to S phase, switching from differentiation to proliferation with DNA replication begins. Differentiation and proliferation of MPCs are independent processes, and fate determination takes precedence over proliferation. Since the differentiating HPCs do not undergo cell division, a committing progenitor will destined to mature into only one committed progenitor cell on its selected differentiation path. The chronological order of quiescence, self-renewal, differentiation, and proliferation, is clearly delineated. Our study reveals that initial progenitors in adult peripheral blood exhibit self-renewal capabilities, which are absent after lineage commitment is completed during hematopoiesis. Furthermore,GATA2andCSF3Rwere confirmed as key transcription factors determining the co-segregation among neutrophils and other lineages, deciphering the underlying molecular mechanisms. Neutrophil present the shortest differentiation trajectory in the hematopoietic hierarchy, which decide their role as rapid responders. Our results provide a clear characterization of the cell cycle kinetics of HPCs’ differentiation and proliferation, facilitating advancements in inflammation and disease treatment.
Testing frameworks for early life effects: the developmental constraints and adaptive response hypotheses do not explain key fertility outcomes in wild female baboons
Authors: Rosenbaum Stacy , Malani Anup , Lea Amanda J. , Tung Jenny , Alberts Susan C. , Archie Elizabeth A.
Published: April 2024

In evolutionary ecology, two classes of explanations are frequently invoked to explain “early life effects” on adult outcomes. Developmental constraints (DC) explanations contend that costs of early adversity arise from limitations adversity places on optimal development. Adaptive response (AR) hypotheses propose that later life outcomes will be worse when early and adult environments are poorly “matched.” Here, we use recently proposed mathematical definitions for these hypotheses and a quadratic-regression based approach to test the long-term consequences of variation in developmental environments on fertility in wild baboons. We evaluate whether low rainfall and/or dominance rank during development predict three female fertility measures in adulthood, and whether any observed relationships are consistent with DC and/or AR. Neither rainfall during development nor the difference between rainfall in development and adulthood predicted any fertility measures. Females who were low-ranking during development had an elevated risk of losing infants later in life, and greater change in rank between development and adulthood predicted greater risk of infant loss. However, both effects were statistically marginal and consistent with alternative explanations, including adult environmental quality effects. Consequently, our data do not provide compelling support for either of these common explanations for the evolution of early life effects.