bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional and structural asymmetry suggest a unifying principle for catalysis in membrane-bound pyrophosphatases
Authors: Strauss Jannik , Wilkinson Craig , Vidilaseris Keni , de Castro Ribeiro Orquidea M , Liu Jianing , Hillier James , Wichert Maximilian , Malinen Anssi M , Gehl Bernadette , Jeuken Lars JC , Pearson Arwen R , Goldman Adrian 
Published: January 2024

AbstractMembrane-bound pyrophosphatases (M-PPases) are homodimeric primary ion pumps that couple the transport of Na+- and/or H+ across membranes to the hydrolysis of pyrophosphate. Their role in the virulence of protist pathogens like Plasmodium falciparum makes them an intriguing target for structural and functional studies. Here, we show the first structure of a K+-independent M-PPase, asymmetric and time-dependent substrate binding in time-resolved structures of a K+-dependent M-PPase and demonstrate pumping-before-hydrolysis by electrometric studies. We suggest how key residues in helix 12, 13, and the exit channel loops affect ion selectivity and K+-activation due to a complex interplay of residues that are involved in subunit-subunit communication. Our findings not only explain ion selectivity in M-PPases but also why they display half-of-the-sites reactivity. Based on this, we propose, for the first time, a unified model for ion-pumping, hydrolysis, and energy coupling in all M-PPases, including those that pump both Na+ and H+.
Diagnosis and classification of disturbances in the power distribution network by phasor measurement unit based on fuzzy intelligent system
Authors: Khosravi Marzieh , Trik Mohammad , Ansari Alireza 
Published: January 2024

AbstractThe dynamic nature of distribution networks raises fresh issues with how such electrical systems function. These networks have some characteristics that indicate the need for better monitoring and control capabilities, including dispersed generation employing renewable resources, changing load profiles, and rising reliability requirements. Phasor measurement units (PMUs) offer simultaneous voltage and current phasor measurements at various places and offer a variety of options for gauging the condition and health of the power distribution network. In this regard, a cost‐optimized PMU with some unique features for distribution systems is presented in this work. These features include a fuzzy inference system to determine the root cause of potential electrical disturbances and methods to estimate electrical parameters through measured field data, which are necessities. This study takes into account the modelling of PMUs, utilizing a process for fault detection and classification with a fuzzy inference network. The 9‐bus distribution network's dependability model is built once the components and their functions are first outlined. The proposed model is then used to calculate the availability of the presented model, which has been examined to provide an analogous reliability model for PMUs. Depending on the specific manufacturer, the PMU's design and specs will change. To extract phase and size measurement features for the proposed model adaptive neural‐fuzzy inference system network's training, two PMU structures and associated reliability models are described here. When merging input data for fuzzy neural network prediction using MATLAB software, fuzzy sets are taken into account for error classification analysis.
Confirmation of the presence of a CRSF in the NICER spectrum of X 1822-371
Authors: Iaria R. , Di Salvo T. , Anitra A. , Miceli C. , Barra F. , Leone W. , Burderi L. , Sanna A. , Riggio A. 
Published: January 2024

Aims. X 1822-371 is an eclipsing binary system with a period close to 5.57 h and an orbital period derivative Ṗorb of 1.42(3) × 10−10 s s−1. The extremely high value of its Ṗorb is compatible with a super-Eddington mass transfer rate from the companion star and, consequently, an intrinsic luminosity at the Eddington limit. The source is also an X-ray pulsar, it shows a spin frequency of 1.69 Hz and is in a spin-up phase with a spin frequency derivative of 7.4 × 10−12 Hz s−1. Assuming a luminosity at the Eddington limit, a neutron star magnetic field strength of B = 8 × 1010 G is estimated. However, a direct measure of B could be obtained observing a CRSF in the energy spectrum. Analysis of XMM-Newton data suggested the presence of a cyclotron line at 0.73 keV, with an estimated magnetic field strength of B = (8.8 ± 0.3)×1010 G.
Methods. Here we analyze the 0.3–50 keV broadband spectrum of X 1822-371 combining a 0.3–10 keV NICER spectrum and a 4.5–50 keV NuSTAR spectrum to investigate the presence of a cyclotron absorption line and the complex continuum emission spectrum.
Results. The NICER spectrum confirms the presence of a cyclotron line at 0.66 keV. The continuum emission is modeled with a Comptonized component, a thermal component associated with the presence of an accretion disk truncated at the magnetospheric radius of 105 km and a reflection component from the disk blurred by relativistic effects.
Conclusions. We confirm the presence of a cyclotron line at 0.66 keV inferring a NS magnetic field of B = (7.9 ± 0.5)×1010 G and suggesting that the Comptonized component originates in the accretion columns.
The bar pattern speed of the Large Magellanic Cloud
Authors: Jiménez-Arranz Ó. , Chemin L. , Romero-Gómez M. , Luri X. , Adamczyk P. , Castro-Ginard A. , Roca-Fàbrega S. , McMillan P. J. , Cioni M.-R. L. 
Published: January 2024

Context. The internal kinematics of the Large Magellanic Cloud (LMC) have been studied in unprecedented depth thanks to the excellent quality of the Gaia mission data, thus revealing the disc’s non-axisymmetric structure.
Aims. We seek to constrain the LMC bar pattern speed using the astrometric and spectroscopic data from the Gaia mission.
Methods. We applied three methods to evaluate the bar pattern speed by measuring it via: the Tremaine-Weinberg (TW) method, the Dehnen method, and a bisymmetric velocity (BV) model. These methods provide additional information on the bar properties, such as the corotation radius as well as the bar length and strength. We tested the validity of the methods with numerical simulations.
Results. A wide range of pattern speeds are inferred by the TW method, owing to a strong dependency on the orientation of the galaxy frame and the viewing angle of the bar perturbation. The simulated bar pattern speeds (corotation radii, respectively) are well recovered by the Dehnen method (BV model). Applied to the LMC data, the Dehnen method finds a pattern speed of Ωp = −1.0 ± 0.5 km s−1 kpc−1, thus corresponding to a bar that barely rotates and is only slightly counter-rotating with respect to the LMC disc. The BV method gives a LMC bar corotation radius of Rc = 4.20 ± 0.25 kpc, corresponding to a pattern speed of Ωp = 18.5−1.1+1.2 km s−1 kpc−1.
Conclusions. It is not possible to determine which global value best represents an LMC bar pattern speed with the TW method, due to the strong variation with the orientation of the reference frame. The non-rotating bar from the Dehnen method would be at odds with the structure and kinematics of the LMC disc. The BV method result is consistent with previous estimates and gives a bar corotation-to-length ratio of 1.8 ± 0.1, suggesting that the LMC is hosting a slow bar.
Spatial resolution effects on the solar open flux estimates
Authors: Milić I. , Centeno R. , Sun X. , Rempel M. , de la Cruz Rodríguez J. 
Published: January 2024

Context.Spectropolarimetric observations used to infer the solar magnetic fields are obtained with a limited spatial resolution. The effects of this limited resolution on the inference of the open flux over the observed region have not been extensively studied.Aims.We aim to characterize the biases that arise in the inference of the mean flux density by performing an end-to-end study that involves the generation of synthetic data, its interpretation (inversion), and a comparison of the results with the original model.Methods.We synthesized polarized spectra of the two magnetically sensitive lines of neutral iron around 630 nm from a state-of-the-art numerical simulation of the solar photosphere. We then performed data degradation to simulate the effect of the telescope with a limited angular resolution and interpreted (inverted) the data using a Milne-Eddington spectropolarimetric inversion code. We then studied the dependence of the inferred parameters on the telescope resolution.Results.The results show a significant decrease in the mean magnetic flux density – related to the open flux observed at the disk center – with decreasing telescope resolution. The original net magnetic field flux is fully resolved by a 1m telescope, but a 20 cm aperture telescope yields a 30% smaller value. Even in the fully resolved case, the result is still biased due to the corrugation of the photospheric surface.Conclusions.Even the spatially averaged quantities, such as the open magnetic flux in the observed region, are underestimated when the magnetic structures are unresolved. The reason for this is the presence of nonlinearities in the magnetic field inference process. This effect might have implications for the modeling of large-scale solar magnetic fields; for example, those corresponding to the coronal holes, or the polar magnetic fields, which are relevant to our understanding of the solar cycle.
Probing a magnetar origin for the population of extragalactic fast X-ray transients detected by Chandra
Authors: Quirola-Vásquez J. , Bauer F. E. , Jonker P. G. , Brandt W. N. , Eappachen D. , Levan A. J. , López E. , Luo B. , Ravasio M. E. , Sun H. , Xue Y. Q. , Yang G. , Zheng X. C. 
Published: January 2024

Context. Twenty-two extragalactic fast X-ray transients (FXTs) have now been discovered from two decades of Chandra data (analyzing ∼259 Ms of data), with 17 associated with distant galaxies (≳100 Mpc). Different mechanisms and progenitors have been proposed to explain their properties; nevertheless, after analyzing their timing, spectral parameters, host-galaxy properties, luminosity function, and volumetric rates, their nature remains uncertain.
Aims. We interpret a sub-sample of nine FXTs that show a plateau or a fast-rise light curve within the framework of a binary neutron star (BNS) merger magnetar model.
Methods. We fit their light curves and derive magnetar (magnetic field and initial rotational period) and ejecta (ejecta mass and opacity) parameters. This model predicts two zones: an orientation-dependent free zone (where the magnetar spin-down X-ray photons escape freely to the observer) and a trapped zone (where the X-ray photons are initially obscured and only escape freely once the ejecta material becomes optically thin). We argue that six FXTs show properties consistent with the free zone and three FXTs with the trapped zone.
Results. This sub-sample of FXTs has a similar distribution of magnetic fields and initial rotation periods to those inferred for short gamma-ray bursts, suggesting a possible association. We compare the predicted ejecta emission fed by the magnetar emission (called merger-nova) to the optical and near-infrared upper limits of two FXTs, XRT 141001 and XRT 210423 where contemporaneous optical observations are available. The non-detections place lower limits on the redshifts of XRT 141001 and XRT 210423 of z ≳ 1.5 and ≳0.1, respectively.
Conclusions. If the magnetar remnants lose energy via gravitational waves (GWs), it should be possible to detect similar objects with the current advanced LIGO detectors out to a redshift z ≲ 0.03, while future GW detectors will be able to detect them out to z ≈ 0.5.
Dust growth and pebble formation in the initial stages of protoplanetary disk evolution
Authors: Vorobyov Eduard I. , Kulikov Igor , Elbakyan Vardan G. , McKevitt James , Güdel Manuel 
Published: January 2024

Aims. The initial stages of planet formation may start concurrently with the formation of a gas-dust protoplanetary disk. This makes the study of the earliest stages of protoplanetary disk formation crucially important. Here we focus on dust growth and pebble formation in a protoplanetary disk that is still accreting from a parental cloud core.
Methods. We have developed an original three-dimensional numerical hydrodynamics code, which computes the collapse of rotating clouds and disk formation on nested meshes using a novel hybrid Coarray Fortran-OpenMP approach for distributed and shared memory parallelization. Dust dynamics and growth are also included in the simulations.
Results. We found that the dust growth from ~1 µm to 1–10 mm already occurs in the initial few thousand years of disk evolution but the Stokes number hardly exceeds 0.1 because of higher disk densities and temperatures compared to the minimum mass Solar nebular. The ratio of the dust-to-gas vertical scale heights remains rather modest, 0.2–0.5, which may be explained by the perturbing action of spiral arms that develop in the disk soon after its formation. The dust-to-gas mass ratio in the disk midplane is highly nonhomogeneous throughout the disk extent and is in general enhanced by a factor of several compared to the fiducial 1:100 value. Low St hinders strong dust accumulation in the spiral arms compared to the rest of the disk and the nonsteady nature of the spirals is also an obstacle. The spatial distribution of pebbles in the disk midplane exhibits a highly nonhomogeneous and patchy character. The total mass of pebbles in the disk increases with time and reaches a few tens of Earth masses after a few tens of thousand years of disk evolution.
Conclusions. We found that protoplanetary disks with an age ≤20 kyr can possess notable amounts of pebbles and feature dust-togas density enhancements in the disk midplane. Hence, these young disks can already be ripe for the planet formation process to start. Multidimensional numerical models of disk formation that consider the coevolution of gas and dust including dust growth are important to improve our understanding of planet formation.
A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere
Authors: Færder Ø. H. , Nóbrega-Siverio D. , Carlsson M. 
Published: January 2024

Context. Plasmoid-mediated reconnection plays a fundamental role in different solar atmospheric phenomena. Numerical reproduction of this process is therefore essential for developing robust solar models.
Aims. Our goal is to assess plasmoid-mediated reconnection across various numerical resistivity models in order to investigate how plasmoid numbers and reconnection rates depend on the Lundquist number.
Methods. We used the Bifrost code to drive magnetic reconnection in a 2D coronal fan-spine topology, carrying out a parametric study of several experiments with different numerical resolution and resistivity models. We employed three anomalous resistivity models: (1) the original hyper-diffusion from Bifrost, (2) a resistivity proportional to current density, and (3) a resistivity quadratically proportional to electron drift velocity. For comparisons, experiments with uniform resistivity were also run.
Results. Plasmoid-mediated reconnection is obtained in most of the experiments. With uniform resistivity, increasing the resolution reveals higher plasmoid frequency with weaker scaling to the Lundquist number, obtaining 7.9–12 plasmoids per minute for SL ∈ [1.8 × 104, 2.6 × 105] with a scaling of SL0.210 in the highest-resolution resistivity cases, transcending into Petschek reconnection in the high-SL limit (where the diffusive effects of the resistivity become small compared to the non-uniform viscosity) and Sweet-Parker reconnection in the low-SL limit. Anomalous resistivity leads to similar results even with lower resolution. The drift-velocity-dependent resistivity excellently reproduces Petschek reconnection for any Lundquist number, and similar results are seen with resistivity proportional to current-density though with slightly lower reconnection rates and plasmoid numbers. Among the different resistivity models applied on the given numerical resolution, the hyper-diffusion model reproduced plasmoid characteristics in closest resemblance to those obtained with uniform resistivity at a significantly higher resolution.
Dynamics of the β Pictoris planetary system and its falling evaporating bodies
Authors: Beust H. , Milli J. , Morbidelli A. , Lacour S. , Lagrange A.-M. , Chauvin G. , Bonnefoy M. , Wang J. 
Published: January 2024

Context. For decades, the spectral variations of β Pictoris have been modelled as the result of the evaporation of exocomets close to the star, termed falling evaporating bodies (FEBs). Resonant perturbations by a hypothetical giant planet have been proposed to explain the dynamical origin of these stargrazers. The disk is now known to harbour two giant planets, β Pic b and c, orbiting the star at 9.9 and 2.7 au. While the former almost matches the planet formerly suspected, the recent discovery of the latter complicates the picture.
Aims. We first question the stability of the two-planet system. Then we investigate the dynamics of a disk of planetesimals orbiting the star together with both planets to check the validity of the FEB generation mechanism.
Methods. Symplectic N-body simulations are used to first determine which regions of the planetesimal disk are dynamically stable and which are not. Then we focus on regions where disk particles are able to reach high eccentricities, mainly thanks to resonant mechanisms.
Results. The first result is that the system is dynamically stable. Both planets may temporarily fall in 7:1 mean-motion resonance (MMR). Then, simulations with a disk of particles reveal that the whole region extending between ~l.5 au and ~25 au is unstable to planetary perturbations. However, a disk below 1.5 au survives, which appears to constitute an active source of FEBs via high-order MMRs with β Pic c. In this new picture, β Pic b acts as a distant perturber that helps sustain the whole process.
Conclusions. Our new simulations rule out the preceding FEB generation mechanism model, which placed their origin at around 4–5 au. Conversely, FEBs are likely to originate from a region much further in and related to MMRs with β Pic c. That mechanism also appears to last longer, as new planetesimals are able to continuously enter the MMRs and evolve towards the FEB state. Subsequently, the physical nature of the FEBs may differ from that previously thought, and presumably may not be icy.
Exsolution process in white dwarf stars
Authors: Camisassa Maria , Baiko Denis A. , Torres Santiago , Rebassa-Mansergas Alberto 
Published: January 2024

Context. White dwarf stars are considered to be suitable cosmic laboratories for studying the physics of dense plasma. Furthermore, the use of white dwarf stars as cosmic clocks to date stellar populations and main sequence companions demands an appropriate understanding of the physics of white dwarfs in order to provide precise ages for these stars.
Aims. We aim to study exsolution in the interior of white dwarf stars, a process in which a crystallized ionic binary mixture separates into two solid solutions with different fractions of the constituents. Depending on the composition of the parent solid mixture, this process can release or absorb heat, thus leading to a delay or a speed-up of white dwarf cooling.
Methods. Relying on accurate phase diagrams for exsolution, we modeled this process in hydrogen(H)-rich white dwarfs with both carbon–oxygen (CO) and oxygen–neon (ONe) core composition, with masses ranging from 0.53 to 1.29 M⊙ and from 1.10 to 1.29 M⊙, respectively.
Results. Exsolution is a slow process that takes place at low luminosities (log(L/L⊙)≲ − 2.75) and effective temperatures (Teff ≲ 18 000 K) in white dwarfs. We find that exsolution begins at brighter luminosities in CO than in ONe white dwarfs of the same mass. Massive white dwarfs undergo exsolution at brighter luminosities than their lower-mass counterparts. The net effect of exsolution on white dwarf cooling times depends on the stellar mass and the exact chemical profile. For standard core chemical profiles and preferred assumptions regarding miscibility gap microphysics, the cooling delay can be as large as ∼0.35 Gyr at log(L/L⊙)∼ − 5. We neglect any chemical redistribution possibly associated with this process, which could lead to a further cooling delay. Although the chemical redistribution is known to accompany exsolution in binary solid mixtures on Earth, given the solid state of the matter, it is hard to model in a reliable way, and its effect may be postponed until very low luminosities.
Conclusions. Exsolution has a marginal effect on white dwarf cooling times and, accordingly, we find no white dwarf branches associated with it on the Gaia color–magnitude diagram. However, exsolution in massive white dwarfs can alter the faint end of the white dwarf luminosity function, thus impacting white dwarf cosmochronology.
Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X
Authors: Ponomarenko S. , Moseev D. , Stange T. , Krier L. , Stordiau P. , Braune H. , Gantenbein G. , Jelonnek J. , Kuleshov A. , Laqua H. P. , Lechte C. , Marsen S. , Nielsen S. K. , Oosterbeek J. W. , Plaum B. , Ragona R. , Rasmussen J. , Ruess T. , Salewski M. , Thumm M. , Zimmermann J. ,   W7-X Team
Published: January 2024

In this paper, we present the design and commissioning results of the upgraded collective Thomson scattering diagnostic at the Wendelstein 7-X stellarator. The diagnostic has a new radiometer designed to operate between the second and third harmonics of the electron cyclotron emission from the plasma at 171–177 GHz, where the emission background has a minimum and is of order 10–100 eV. It allows us to receive the scattered electromagnetic field with a significantly improved signal-to-noise ratio and extends the set of possible scattering geometries compared to the case of the original instrument operated at 140 GHz. The elements of the diagnostic are a narrowband notch filter and a frequency stabilized probing gyrotron that will allow measuring scattered radiation spectra very close to the probing frequency. Here, we characterize the microwave components applied to the radiometer and demonstrate the performance of the complete system that was achieved during the latest experimental campaign, OP2.1.
A comparison of QTP functionals against coupled-cluster methods for EAs of small organic molecules
Authors: Pavlicek Abigail , Windom Zachary W. , Perera Ajith , Bartlett Rodney J. 
Published: January 2024

EA-EOM-CCSD electron affinities and LUMO energies of various Kohn–Sham density functional theory (DFT) methods are calculated for an a priori IP benchmark set of 64 small, closed-shell molecules. The purpose of these calculations was to investigate whether the QTP KS-DFT functionals can emulate EA-EOM-CC with only a mean-field approximation. We show that the accuracy of DFT—relative to CCSD—improves significantly when elements of correlated orbital theory are introduced into the parameterization to define the QTP family of functionals. In particular, QTP(02), which has only a single range separation parameter, provides results accurate to a MAD of &lt;0.15 eV for the whole set of 64 molecules compared to EA-EOM-CCSD, far exceeding the results from the non-QTP family of density functionals.