bluuebunny/crossref_metadata_2025 huggingface dataset:
Delineating mechanisms underlying parvalbumin neuron impairment in different neurological and neurodegenerative disorders: the emerging role of mitochondrial dysfunction
Authors: Olkhova Elizaveta A. , Smith Laura A. , Dennis Bethany H. , Ng Yi Shiau , LeBeau Fiona E. N. , Gorman Gráinne S.
Published: April 2024

Given the current paucity of effective treatments in many neurological disorders, delineating pathophysiological mechanisms among the major psychiatric and neurodegenerative diseases may fuel the development of novel, potent treatments that target shared pathways. Recent evidence suggests that various pathological processes, including bioenergetic failure in mitochondria, can perturb the function of fast-spiking, parvalbumin-positive neurons (PV+). These inhibitory neurons critically influence local circuit regulation, the generation of neuronal network oscillations and complex brain functioning. Here, we survey PV+ cell vulnerability in the major neuropsychiatric, and neurodegenerative diseases and review associated cellular and molecular pathophysiological alterations purported to underlie disease aetiology.
High-resolution spectroscopy of the intermediate polar EX Hydrae
Authors: Beuermann K. , Reinsch K.
Published: April 2024

EX Hya is one of the best studied, but still enigmatic intermediate polars. We present phase-resolved blue VLT/UVES high-resolution (λ/Δλ ≃ 16.000) spectra of EX Hya taken in January 2004. Our analysis involves a unique decomposition of the Balmer line profiles into the spin-modulated line wings that represent streaming motions in the magnetosphere and the orbital-phase modulated line core that represents the accretion disk. Spectral analysis and tomography show that the division line between the two is solidly located at ∣υrad ∣   ≃  1200 km s−1, defining the inner edge of the accretion disk at rin ≃ 7  ×  109 cm or ∼10R1 (WD radii). This large central hole allows an unimpeded view of the tall accretion curtain at the lower pole with a shock height up to hsh ∼ 1R1 that is required by X-ray and optical observations. Our results contradict models that advocate a small magnetosphere and a small inner disk hole. Equating rin with the magnetospheric radius in the orbital plane allows us to derive a magnetic moment of the WD of μ1 ≃ 1.3  ×  1032 G cm3 and a surface field strength B1 ∼ 0.35 MG. Given a polar field strength Bp ≲ 1.0 MG, optical circular polarization is not expected. With an accretion rate Ṁ = 3.9 × 10−11 M⊙ yr−1, the accretion torque is Gacc ≃ 2.2  ×  1033 g cm2 s−2. The magnetostatic torque is of similar magnitude, suggesting that EX Hya is not far from being synchronized. We measured the orbital radial-velocity amplitude of the WD, K1 = 58.7 ± 3.9 km s−1, and found a spin-dependent velocity modulation as well. The former is in perfect agreement with the mean velocity amplitude obtained by other researchers, confirming the published component masses M1 ≃ 0.79 M⊙ and M2 ≃ 0.11 M⊙.
Infrared colours and bolometric corrections of SiO masing stars in the inner Milky Way
Authors: Messineo Maria
Published: April 2024

Aims. We analysed a sample of SiO-masing late-type stars located in the inner Galaxy with the goal of setting better constraints on their obscuration.

Methods. This reference sample has allowed us to define mathematical relations between their dereddened infrared colours and the observed colours (e.g. Ks-[8], Ks-[24]).

Results. The derived equations define a property (the locus) of these late-type stars. Therefore, they enable us to derive the interstellar extinction. With estimated spectral types, it is possible to decompose the total extinction in the two components (interstellar and envelope extinction).

Conclusions. These relations are useful for classifying extremely obscured late-type stars located in the inner Galaxy. Estimating the two extinction components can be performed on an individual late-type star, independently of its surroundings and even when few mid-infrared measurements are available.
Fine structure in the Sigma Orionis cluster revealed by Gaia DR3
Authors: Žerjal M. , Martín E. L. , Pérez-Garrido A.
Published: April 2024

Context. Sigma Orionis is an open cluster in the nearest giant star formation site – Orion. Its youth (3−5 Myr), low reddening, and relative vicinity make it an important benchmark cluster to study stellar and substellar formation and evolution.

Aims. Young star-forming sites are complex and hierarchical. Precision astrometry from Gaia DR3 enables the exploration of their fine structure.

Methods. We used the modified convergent point technique to kinematically re-evaluate the members in the Sigma Orionis cluster and its vicinity.

Results. We present clear evidence for three kinematically distinct groups in the Sigma Orionis region. The second group, the RV Orionis association, is adjacent to the Sigma Orionis cluster and is composed only of low-mass stars. The third group, the Flame association, whose age is comparable to that of Sigma Orionis, overlaps with the younger NGC 2024 in the Flame Nebula. In total, we have discovered 105 members of this complex not previously found in the literature (82 in Sigma Orionis, 19 in the Flame association, and 4 in the RV Orionis association).
Solar synthetic imaging: Introducing denoising diffusion probabilistic models on SDO/AIA data
Authors: Ramunno F. P. , Hackstein S. , Kinakh V. , Drozdova M. , Quétant G. , Csillaghy A. , Voloshynovskiy S.
Published: April 2024

For the luck of humanity, there are way less big solar flares than small ones. Even if these are good news, this makes it challenging to train machine learning algorithms able to model solar activity. As a result, solar monitoring applications, including flare forecasting, suffer from this lack of input data. To overcome this issue, generative deep learning models can be utilised to produce synthetic images representing solar activity and thus compensating the rarity of big events. This study aims to develop a method that can generate synthetic images of the Sun with the ability to include flare of a specific intensity. To achieve our goals, we introduce a Denoising Diffusion Probabilistic Model (DDPM). We train it with a carefully crafted dataset from the Atmospheric Image Assembly (AIA) instrument on the SDO spacecraft, specifically the 171 Å band, which captures images of coronal loops, filaments, flares, and active regions. GOES X-ray measurements are employed to classify each image based on the solar flare scale (A, B, C, M, X), after selecting the flaring images from AIA using the Heliophysics Event Knowledgebase, which allows for temporal localisation of the flaring events. The generative model performance is evaluated using cluster metrics, Fréchet Inception Distance (FID), and the F1-score. We demonstrate state-of-the-art results in generating solar images and conduct two experiments that use the synthetic images. The first experiment trains a supervised classifier to identify those events. The second experiment trains a basic solar flare predictor. The experiments demonstrate the effectiveness of additional synthetic samples to addressing the problem of imbalanced datasets. We believe this is only the beginning of DDPM use with solar data. It remains to gain a better understanding of the generation capabilities of the denoising diffusion probabilistic models in the contest of solar flare predictions and apply them to other deep learning and physical tasks, such as AIA to HMI () image translation.
Polarimetric differential imaging with VLT/NACO
Authors: de Regt S. , Ginski C. , Kenworthy M. A. , Caceres C. , Garufi A. , Gledhill T. M. , Hales A. S. , Huelamo N. , Kóspál Á. , Millar-Blanchaer M. A. , Pérez S. , Schreiber M. R.
Published: April 2024

Context. The observed diversity of exoplanets can possibly be traced back to the planet formation processes. Planet-disk interactions induce sub-structures in the circumstellar disk that can be revealed via scattered light observations. However, a high-contrast imaging technique such as polarimetric differential imaging (PDI) must first be applied to suppress the stellar diffraction halo.

Aims. In this work we present the PDI PiPelIne for NACO data (PIPPIN), which reduces the archival polarimetric observations made with the NACO instrument at the Very Large Telescope. Prior to this work, such a comprehensive pipeline to reduce polarimetric NACO data did not exist. We identify a total of 243 datasets of 57 potentially young stellar objects observed before NACO’s decommissioning.

Methods. The PIPPIN pipeline applies various levels of instrumental polarisation correction and is capable of reducing multiple observing setups, including half-wave plate or de-rotator usage and wire-grid observations. A novel template-matching method is applied to assess the detection significance of polarised signals in the reduced data.

Results. In 22 of the 57 observed targets, we detect polarised light resulting from a scattering of circumstellar dust. The detections exhibit a collection of known sub-structures, including rings, gaps, spirals, shadows, and in- or outflows of material. Since NACO was equipped with a near-infrared wavefront sensor, it made unique polarimetric observations of a number of embedded protostars. This is the first time detections of the Class I objects Elia 2-21 and YLW 16A have been published. Alongside the outlined PIPPIN pipeline, we publish an archive of the reduced data products, thereby improving the accessibility of these data for future studies.
Cygnus OB2 as a test case for particle acceleration in young massive star clusters
Authors: Menchiari S. , Morlino G. , Amato E. , Bucciantini N. , Beltrán M. T.
Published: April 2024

In this paper, we focus on the scientific case of Cygnus OB2, a young massive star cluster (YMSC) located in the northern sky towards the Cygnus X star-forming complex. We consider a model that assumes cosmic-ray acceleration occurring only at the termination shock of the collective wind of the YMSC and address the question of whether or not, and under what hypotheses, hadronic emission by the accelerated particles can account for the observations of Cygnus OB2 obtained byFermi-LAT and HAWC. To this end, we carefully review the available information on this source, also confronting different estimates of the relevant parameters with ad hoc developed simulations. Once other model parameters are fixed, the spectral and spatial properties of the emission are found to be very sensitive to the unknown properties of the turbulent magnetic field. Comparison with the data shows that our suggested scenario is incompatible with Kolmogorov turbulence. Assuming Kraichnan- or Bohm-type turbulence spectra, the model accounts well for the very high energy (VHE) data, but fails to reproduce the centrally peaked morphology observed byFermi-LAT, suggesting that additional effects might be important for lower energyγ-ray emission. We discuss how additional progress can be made with more detailed and extended knowledge of the spectral and morphological properties of the emission.
FINKER: Frequency Identification through Nonparametric KErnel Regression in astronomical time series
Authors: Stoppa F. , Johnston C. , Cator E. , Nelemans G. , Groot P. J.
Published: April 2024

Context. Optimal frequency identification in astronomical datasets is crucial for variable star studies, exoplanet detection, and astero-seismology. Traditional period-finding methods often rely on specific parametric assumptions, employ binning procedures, or overlook the regression nature of the problem, limiting their applicability and precision.

Aims. We introduce a universal- nonparametric kernel regression method for optimal frequency determination that is generalizable, efficient, and robust across various astronomical data types.

Methods. FINKER uses nonparametric kernel regression on folded datasets at different frequencies, selecting the optimal frequency by minimising squared residuals. This technique inherently incorporates a weighting system that accounts for measurement uncertainties and facilitates multi-band data analysis. We evaluated our method’s performance across a range of frequencies pertinent to diverse data types and compared it with an established period-finding algorithm, conditional entropy.

Results. The method demonstrates superior performance in accuracy and robustness compared to existing algorithms, requiring fewer observations to reliably identify significant frequencies. It exhibits resilience against noise and adapts well to datasets with varying complexity.
JWST Observations of Young protoStars (JOYS)
Authors: Tychoniec Łukasz , van Gelder Martijn L. , van Dishoeck Ewine F. , Francis Logan , Rocha Will R. M. , Caratti o Garatti Alessio , Beuther Henrik , Gieser Caroline , Justtanont Kay , Linnartz Harold , Le Gouellec Valentin J. M. , Perotti Giulia , Devaraj Rangaswamy , Tabone Benoît , Ray Thomas P. , Brunken Nashanty G. C. , Chen Yuan , Kavanagh Patrick J. , Klaassen Pamela , Slavicinska Katerina , Güdel Manuel , Östlin Goran
Published: April 2024

Context. Accretion and ejection dictate the outcomes of star and planet formation processes. The mid-infrared (MIR) wavelength range offers key tracers of processes that have been difficult to detect and spatially resolve in protostars until now.

Aims. We aim to characterize the interplay between accretion and ejection in the low-mass Class I protobinary system TMC1, comprising two young stellar objects: TMC1-W and TMC1-E at a 85 au separation.

Methods. Using the James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) observations in 5–28 μm range, we measured the intensities of emission lines of H2, atoms, and ions, for instance, the [Fe II] and [Ne II], and HI recombination lines. We analyzed the spatial distribution of the different species using the MIRI Medium Resolution Spectrometer (MRS) capabilities to spatially resolve emission at 0″​​.2–0″​​.7 scales. we compared these results with the corresponding Atacama Large Millimeter/submillimeter Array (ALMA) maps tracing cold gas and dust.

Results. We detected H2 outflow coming from TMC1-E, with no significant H2 emission from TMC1-W. The H2 emission from TMC1-E outflow appears narrow and extends to wider opening angles with decreasing Eup from S(8) to S(1) rotational transitions, indicating the disk wind as its origin. The outflow from TMC1-E protostar shows spatially extended emission lines of [Ne II], [Ne III], [Ar II], and [Ar III], with their line ratios consistent with UV radiation as a source of ionization. With ALMA, we detected an accretion streamer infalling from > 1000 au scales onto the TMC1-E component. The TMC1-W protostar powers a collimated jet, detected with [Fe II] and [Ni II], making it consistent with energetic flow. A much weaker ionized jet is observed from TMC1-E, and both jets appear strikingly parallel to each other, indicating that the disks are co-planar. TMC1-W is associated with strong emission from hydrogen recombination lines, tracing the accretion onto the young star.

Conclusions. MIRI-MRS observations provide an unprecedented view of protostellar accretion and ejection processes on 20 au scales. Observations of a binary Class I protostellar system show that the two processes are clearly intertwined, with accretion from the envelope onto the disk influencing a wide-angle wind ejected on disk scales. Finally, the accretion from the protostellar disk onto the protostar is associated with the source launching a collimated high-velocity jet within the innermost regions of the disk.
Supermassive Black Hole Winds in X-rays: SUBWAYS
Authors: Gianolli V. E. , Bianchi S. , Petrucci P.-O. , Brusa M. , Chartas G. , Lanzuisi G. , Matzeu G. A. , Parra M. , Ursini F. , Behar E. , Bischetti M. , Comastri A. , Costantini E. , Cresci G. , Dadina M. , De Marco B. , De Rosa A. , Fiore F. , Gaspari M. , Gilli R. , Giustini M. , Guainazzi M. , King A. R. , Kraemer S. , Kriss G. , Krongold Y. , La Franca F. , Longinotti A. L. , Luminari A. , Maiolino R. , Marconi A. , Mathur S. , Matt G. , Mehdipour M. , Merloni A. , Middei R. , Miniutti G. , Nardini E. , Panessa F. , Perna M. , Piconcelli E. , Ponti G. , Ricci F. , Serafinelli R. , Tombesi F. , Vignali C. , Zappacosta L.
Published: April 2024

The detection of blueshifted absorption lines likely associated with ionized iron K-shell transitions in the X-ray spectra of many active galactic nuclei (AGNs) suggests the presence of a highly ionized gas outflowing with mildly relativistic velocities (0.03c–0.6c) named ultra-fast outflow (UFO). Within the SUBWAYS project, we characterized these winds starting from a sample of 22 radio-quiet quasars at an intermediate redshift (0.1 ≤ z ≤ 0.4) and compared the results with similar studies in the literature on samples of local Seyfert galaxies (i.e., 42 radio-quiet AGNs observed with XMM-Newton at z ≤ 0.1) and high redshift radio-quiet quasars (i.e., 14 AGNs observed with XMM-Newton and Chandra at z ≥ 1.4). The scope of our work is a statistical study of UFO parameters and incidence considering the key physical properties of the sources, such as supermassive black hole (SMBH) mass, bolometric luminosity, accretion rates, and spectral energy distribution (SED) with the aim of gaining new insights into the UFO launching mechanisms. We find indications that highly luminous AGNs with a steeper X-ray/UV ratio, αox, are more likely to host UFOs. The presence of UFOs is not significantly related to any other AGN property in our sample. These findings suggest that the UFO phenomenon may be transient. Focusing on AGNs with UFOs, other important findings from this work include: (1) faster UFOs have larger ionization parameters and column densities; (2) X-ray radiation plays a more crucial role in driving highly ionized winds compared to UV; (3) the correlation between outflow velocity and luminosity is significantly flatter than what is expected for radiatively driven winds; (4) more massive black holes experience higher wind mass losses, suppressing the accretion of matter onto the black hole; (5) the UFO launching radius is positively correlated with the Eddington ratio. Furthermore, our analysis suggests the involvement of multiple launching mechanisms, including radiation pressure and magneto-hydrodynamic processes, rather than pointing to a single, universally applicable mechanism.
The history and mass content of cluster galaxies in the EAGLE simulation
Authors: Sifón Cristóbal , Han Jiaxin
Published: April 2024

Aims.We explore the mass content of galaxies residing in galaxy clusters atz = 0 in the EAGLE cosmological hydrodynamical simulation. We also explore the galaxies’ mass build-up through cosmic time.

Methods.We used a galaxy catalogue generated with theHBT+ algorithm, which identifies subhaloes consistently over time by tracking their dynamical evolution throughout the simulation.

Results.The satellite subhalo-to-stellar mass relation (SHSMR) is well described by a double power law, becoming increasingly steeper with stellar mass. At stellar masses 9 < logm⋆/M⊙ < 10, satellites have 20−25% the subhalo mass of central galaxies at fixed stellar mass. At high stellar masses,m⋆ > 2 × 1011 M⊙, the satellite SHSMR is consistent with that of centrals. The satellite SHSMR decreases steeply for satellites closer to the cluster centre, even in projection, broadly consistent with recent weak lensing measurements. The scatter in the satellite SHSMR is larger than that of central galaxies at all cluster masses and cluster-centric distancesR < R200m. The SHSMR scatter decreases with stellar mass by about 12% over an order of magnitude, but this dependence can be explained by the mixing of infall times when binning by stellar mass. By splitting satellites into direct and indirect infallers (those that fell into their current host as a central galaxy or as the satellite of an infalling group, respectively) we clearly show the impact of pre-processing separately on satellite galaxies’ dark and stellar mass. There is significant dark matter pre-processing; the most recent infallers into massive clusters (M200m ≳ 1014 M⊙) had already lost up to 50% of their dark matter by the time of infall, particularly if they fell in indirectly as satellites of another host. On the contrary, on average, satellite galaxies are still gaining stellar mass at the time of infall and they do so for another 2 Gyr afterwards, although we see evidence of a slowing growth for indirect infallers. How much and for how long they continue to gain stellar mass depends primarily on the gas mass fraction available at infall. Overall, pre- and post-processing have similar impacts on the satellite SHSMR. Finally, we provide a simple prescription to infer the mean mass loss experienced by satellites as a function of cluster-centric distance based on a comparison to central galaxies, convenient for observational weak lensing measurements.
Constraints on supermassive black hole binaries from JWST and NANOGrav
Authors: Padmanabhan Hamsa , Loeb Abraham
Published: April 2024

We use the recent statistics of dual active galactic nuclei (AGN) in the James Webb Space Telescope (JWST) data at z ∼ 3.4 to address two aspects of the feedback and evolution scenarios of supermassive black hole binaries. We find that the JWST data provide evidence for the members of a binary BH being ‘lit’ at the same time, rather than independently – a scenario which is consistent with gas-rich mergers being responsible for concurrent AGN activity. This conclusion is supported by the recent NANOGrav Pulsar Timing Array (PTA) measurements, whose upper limits on the stochastic gravitational wave strain amplitude lie below those expected from extrapolating the dual AGN fraction. The results indicate either a ‘stalling’ of the binaries at the separations probed by NANOGrav, or rapid gas-driven inspirals.
Populating the Milky Way
Authors: Boettner C. , Dayal P. , Trebitsch M. , Libeskind N. , Rice K. , Cockell C. , Tieleman B. I.
Published: April 2024

Context.Stellar populations and their distribution differ widely across the Galaxy, which is likely to affect planet demographics. Our local neighbourhood is dominated by young, metal-rich stars in the galactic thin disc, while the stellar halo and galactic bulge host a large fraction of older, metal-poor stars.

Aims.We study the impact of these variations on planet populations in different regions of the Galaxy by combining a high-resolution galaxy formation simulation with state-of-the-art planet population synthesis models.

Methods.We constructed a population model to estimate occurrence rates of different planet types, based on the New Generation Planet Population Synthesis (NGPPS). We applied this model to a simulated Milky Way (MW) analogue in the HESTIA galaxy formation simulation. We studied the planet occurrence rate in the metal-rich regions of the inner Galaxy, namely, in the galactic bulge and thin disc. We compared these result with the frequencies in the more distant, metal-poor region such as the thick disc and stellar halo.

Results.We find that the planet demographics in the central, metal-rich regions of the MW analogue differ strongly from the planet populations in the more distant, metal-poor regions. The occurrence rate of giant planets (>300M⊕) is 10–20 times larger in the thin disc compared to the thick disc, driven by the low amounts of solid material available for planet formation around metal-poor stars. Similarly, low-mass Earth-like planets around Sun-like stars are most abundant in the thick disc, being 1.5 times more frequent than in the thin disc. Moreover, low-mass planets are expected to be abundant throughout the galaxy, from the central regions to the outer halo, due to their formation processes being less dependent on stellar metallicity. The planet populations differ more strongly around Sun-like stars compared to dwarfs with masses 0.3–0.5M⊙, caused by a weaker correlation between [Fe/H] metallicity and planet mass. However, it is important to note that the occurrence rates of low-mass planets are still uncertain, making our findings strongly model-dependent. Massive planets are more comprehensively understood and our findings are more robust. Nonetheless, other systematic effects have the potential to alter the giant planet population that we have not addressed in this study. We discuss some of these limitations and offer further directions for future research.
The orbital parameters of theδCep inner binary system determined using 2019 HARPS-N spectroscopic data
Authors: Nardetto N. , Hocdé V. , Kervella P. , Gallenne A. , Gieren W. , Graczyk D. , Merand A. , Rainer M. , Storm J. , Pietrzyński G. , Pilecki B. , Poretti E. , Bailleul M. , Bras G. , Afanasiev A.
Published: April 2024

Context.An inner companion has recently been discovered orbiting the prototype of classical Cepheids,δCep, whose orbital parameters are still not fully constrained.

Aims.We collected new precise radial velocity measurements ofδCep in 2019 using the HARPS-N spectrograph mounted at the Telescopio NazionaleGalileo. Using these radial velocity measurements, we aimed to improve the orbital parameters of the system.

Methods.We considered a template available in the literature as a reference for the radial velocity curve of the pulsation of the star. We then calculated the residuals between our global dataset (composed of the new 2019 observations plus data from the literature) and the template as a function of the pulsation phase and the barycentric Julian date. This provides the orbital velocity of the Cepheid component. Using a Bayesian tool, we derived the orbital parameters of the system.

Results.Considering priors based on already publishedGaiaconstraints, we find for the orbital period a maximum a posteriori probability ofPorb = 9.32−0.04+0.03years (uncertainties correspond to the 95% highest density probability interval), and we obtain an eccentricitye = 0.71−0.02+0.02, a semimajor axisa = 0.029−0.003+0.002arcsec, and a center-of-mass velocityV0 = −17.28−0.08+0.08km s−1, among other parameters.

Conclusions.In this short analysis we derive the orbital parameters of theδCep inner binary system and provide a cleaned radial velocity curve of the pulsation of the star, which will be used to study its Baade–Wesselink projection factor in a future publication.
From giant clumps to clouds
Authors: Renaud Florent , Agertz Oscar , Romeo Alessandro B.
Published: April 2024

The clumpy nature of gas-rich galaxies at cosmic noon raises the question of universality of the scaling relations and average properties of the star-forming structures. Using controlled simulations of disk galaxies and varying only the gas fraction, we show that the influence of the galactic environments (large-scale turbulence, tides, and shear) contributes, together with the different regime of instabilities, to setting a diversity of physical conditions for the formation and evolution of gas clumps from low to high gas fractions. However, the distributions of gas clumps at all gas fractions follow similar scaling relations as Larson’s, suggesting the universality of median properties. Yet, we find that the scatter around these relations significantly increases with the gas fraction, allowing for the presence of massive, large, and highly turbulent clouds in gas-rich disks in addition to a more classical population of clouds. Clumps with an excess of mass for their size are slightly denser, more centrally concentrated, and host more abundant and faster star formation. We find that the star formation activity (rate, efficiency, and depletion time) correlates much more strongly with the excess of mass than with the mass itself. Our results suggest the existence of universal scaling relations for gas clumps but with redshift-dependent scatters, which calls for deeper and more complete census of the populations of star-forming clumps and young stellar clusters at cosmic noon and beyond.
Transition-Metal- and Photocatalyst-Free Photoinduced Formation of Carbon–Pnictogen (–N, –P) Bonds
Authors: Bhanja Rosalin , Bera Shyamal Kanti , Mal Prasenjit
Published: April 2024

Pnictogens, classified within group 15 elements, play a pivotal role in the constitution of a diverse array of drug molecules, natural products, and functional materials. Recent research has increasingly prioritized the exploration of mild conditions for synthesizing C–Pnictogen (C–N and C–P) bonds, highlighting a growing emphasis on efficient and sustainable synthetic methodologies. This Short Review explores fundamental mechanisms, addresses constraints, and assesses diverse methodologies, underscoring the potential of photocatalyst- and transition-metal-free photochemical reactions in advancing sustainability. Divided into two segments, it encompasses recent advancements in reactions facilitating C–N and C–P bond formation.

1 Introduction

2 Carbon–Nitrogen (C–N) Bond Formation

3 Carbon–Phosphorus (C–P) Bond Formation

4 Summary and Outlook
Culturally mixed co-branding product framing in China: the role of cultural sensitivity, product quality, and purchase probability
Authors: Chiu Candy Lim , Ho Han-Chiang , Xie Zhengqiao , Wu Qi , Yuan Yuqi
Published: April 2024

Chinese consumers have shown a strong preference for foreign brands (FBs) for many years. However, in recent years, rising patriotism has spurred Chinese consumers to source locally, indicating a shift in preference for patriotic brands (PBs). FBs operating in the world’s second-largest market are now framing their marketing strategies to appeal more to Chinese consumers. This study examines two culturally mixed co-branded product (CMCP) framing strategies:foreign × hostculture (FB × PB) andhost × foreignculture (PB × FB). The results show that the effects of product fit and cultural congruence on co-branding attitude forPB × FBis stronger than that ofFB × PB, and the influence of brand fit on co-branding attitude forFB × PBis stronger than that ofPB × FB. Additionally, the impact of the co-branding attitude on cultural sensitivity was significant forPB × FB, whereas that on product quality was significant for FB × PB. Furthermore, the effects of co-branding attitude on purchase probability were significant for both types of CMCP framing (FB × PB < PB × FB). Structural equation modeling was used to analyze the preferences of 479 Chinese consumers. This study provides significant recommendations for FBs and PBs to benefit from a strong wave of patriotism in China through culturally mixed framing and glocalization co-branding strategies.
Dispersion scan frequency resolved optical gating for consistency check of pulse retrieval
Authors: Guesmi Mariem , Veselá Petra , Žídek Karel
Published: April 2024

Many methods commonly used to characterize ultrafast laser pulses, such as the frequency-resolved optical gating (FROG) or the dispersion scan (d-scan), face problems when they are used on pulses with a spectrum or phase varying within the laser beam cross section or the acquisition time. The presence of such pulse shape variation leads to discrepancy between the measured FROG trace and its reconstructed counterparts. Nevertheless, it is difficult to reliably discern this shape variation because even the distorted experimental FROG trace can be reasonably reproduced by a realistic pulse shape. In this work, we examine and discern the variation of the pulse shape based on a new method, dispersion-scan FROG (D-FROG), which combines the idea of dispersion scanning with the FROG method. This technique provides a means of careful evaluation of the laser pulse based on a set of FROG traces connected by known dispersion changes. Therefore, this method can disclose seemingly correct pulse retrievals from distorted datasets. The D-FROG method can be used as a simple extension of the FROG technique to provide a consistency check able to identify the shortcomings in the pulse characterization.
On the Poisson equation for nonreversible Markov jump processes
Authors: Khodabandehlou Faezeh , Maes Christian , Netočný Karel
Published: April 2024

We study the solution V of the Poisson equation LV + f = 0 where L is the backward generator of an irreducible (finite) Markov jump process and f is a given centered state function. Bounds on V are obtained using a graphical representation derived from the Matrix Forest Theorem and using a relation with mean first-passage times. Applications include estimating time-accumulated differences during relaxation toward a steady nonequilibrium regime. That includes obtaining bounds for the quasipotential which controls the thermal response.
E-band telecom-compatible 40 dB gain high-power bismuth-doped fiber amplifier with record power conversion efficiency
Authors: Donodin Aleksandr , Manuylovich Egor , Dvoyrin Vladislav , Melkumov Mikhail , Mashinsky Valery , Turitsyn Sergei
Published: April 2024

Multi-band transmission is one of the key practical solutions to cope with the continuously growing demand on the capacity of optical communication networks without changing the huge existing fiber base. However, ultra-broadband communication requires the development of novel power efficient optical amplifiers operating beyond C- and L-bands, and this is a major research and technical challenge comparable to the introduction of the seminal erbium-doped fiber amplifiers that dramatically changed the optical communication sector. There are several types of optical fibers operating beyond C- and L-bands that can be used for the development of such amplifiers, specifically the fibers doped with neodymium, praseodymium, thulium, and bismuth. However, among these, Bi-doped fibers are of special interest as the most promising amplification medium because, unlike the others, different Bi-associated active centers allow amplification in an enormous band of overall width of 700 nm (1100–1800 nm). Such spectral coverage can be obtained by using different host materials, such as aluminosilicate, phosphosilicate, silica, and germanosilicate glasses. Here, we report a novel Bi-doped fiber amplifier with record characteristics for E-band amplification, including the highest power conversion efficiency among telecom-compatible E-band amplifiers reported to date. This bismuth-doped fiber amplifier (BDFA) features a maximum gain of 39.8 dB and a minimal noise figure of 4.6 dB enabled by 173 m Bi-doped fiber length. The maximum achieved power conversion efficiency of 38% is higher than that of L-band Er-doped fiber amplifiers. This performance demonstrates the high potential of BDFA for becoming the amplifier of choice in modern multi-band optical communication networks.
Efficient numerical algorithm for multi-level ionization of high-atomic-number gases
Authors: Cheng A. , Samulyak R. , Kupfer R. , Pérez-Ríos J. , Vafaei-Najafabadi N.
Published: April 2024

An efficient numerical algorithm for laser driven multi-level ionization of high-atomic-number gases is proposed and implemented in an electromagnetic particle-in-cell code SPACE. The algorithm is based on analytical solutions to the system of differential equations describing ionization evolution. Using analytical solutions resolves the multiscale issue of ionization due to different characteristic time scales of ionization processes and the main code time step. Algorithm efficiency and memory requirements are significantly improved by using a locally reduced system of differential equations. The algorithm also assigns proper orbital quantum numbers and their projections to ionization states. The algorithm is verified and validated using experimental data.
Computational investigation of structural, electronic, and spectroscopic properties of Ni and Zn metalloporphyrins with varying anchoring groups
Authors: Bashir Beenish , Alotaibi Maha M. , Clayborne Andre Z.
Published: April 2024

Porphyrins are prime candidates for a host of molecular electronics applications. Understanding the electronic structure and the role of anchoring groups on porphyrins is a prerequisite for researchers to comprehend their role in molecular devices at the molecular junction interface. Here, we use the density functional theory approach to investigate the influence of anchoring groups on Ni and Zn diphenylporphyrin molecules. The changes in geometry, electronic structure, and electronic descriptors were evaluated. There are minimal changes observed in geometry when changing the metal from Ni to Zn and the anchoring group. However, we find that the distribution of electron density changes when changing the anchoring group in the highest occupied and lowest unoccupied molecular orbitals. This has a direct effect on electronic descriptors such as global hardness, softness, and electrophilicity. Additionally, the optical spectra of both Ni and Zn diphenylporphyrin molecules exhibit either blue or red shifts when changing the anchoring group. These results indicate the importance of the anchoring group on the electronic structure and optical properties of porphyrin molecules.
Theory and inverse design of microperforated panels comprising arbitrary axial pore profiles for broadband low-frequency sound absorption
Authors: Vigneswar O. V. , Chandraprakash C.
Published: April 2024

Toward identifying efficient sound absorbers, we have formulated and analyzed the micro-perforated panels (MPPs) comprising cylindrical pores of arbitrary axial profiles for out-of-plane wave propagation. First, the forward problem was solved wherein an exact analytical expression for the absorption coefficient α was developed for these MPPs. The dependence of α was analyzed for various profiles comprising convex and concave-shaped sections including divergent and convergent linear and sinusoidal profiles, conic sections, Kilroy, and chirp shapes. The MPPs with pores having a diverging shape at the entrance were found to have higher sound absorption. The non-symmetric fluctuations in the profile led to fluctuations in the spectrum of α. Aiming to address the long-standing challenge of low-frequency sound absorption, we solved the inverse problem to identify the axial profile of the cylindrical pore for maximum sound absorption for frequencies up to 2500 Hz. Given the advances in additive manufacturing, the results of this comprehensive work help in designing MPPs comprising complex-shaped pores suitable for a particular spectral regime.
A versatile setup for nanosecond laser polishing processes with in situ analysis capabilities
Authors: Brockner F. , Lützenkirchen-Hecht D.
Published: April 2024

Laser polishing of material surfaces is a complex process depending on many variable parameters, such as, e.g., the properties of the used laser and optics (wavelength, pulse duration, fluence, and profile), as well as the processing (spot size, feed rate, and line or point overlap), and the thermodynamical properties of the material to be polished (heat capacity, heat conduction, etc.). For the successful laser polishing of any material, a systematic variation of all the process parameters is required to obtain satisfactorily polished surfaces with an appropriate set of parameters for the material of interest. In order to allow systematic studies of laser polishing processes, a new setup employing a highly stable nanosecond laser with an adjustable wavelength has been realized. The sample is located in a small high-vacuum chamber with the capability of introducing additional gases in a controlled manner, and the entire chamber is scanned in the beam to allow laser polishing of selected spots, lines, or larger areas. The setup is fully remote-controlled and allows in situ inspection of the initiated processes by means of a long-range microscope, electrical measurements, reflected laser light from the sample surface, and an analysis of the vacuum within the process chamber. The main properties of the setup will be presented, and some exemplary results on niobium and molybdenum metal samples will be discussed.
Breakdown dynamics and instability of underwater metallic aerosol bubble atomized by electrical explosion
Authors: Han Ruoyu , Yuan Wei , Cao Yuchen , Bai Jie , Wang Menglei , Wang Yongming , Li Liuxia
Published: April 2024

This study delves into the electrophysical processes and intricate fluid dynamics of an electrical-explosion-induced bubble in water. A fine copper wire is heated up and exploded to dense metallic aerosol (vapor–drop mixture) via a μs-timescale 10 kA current pulse, crossing a wide range of the density–temperature parametric space. High-speed photography along with discharge diagnostics reveals two modes for plasma development (restrike) inside explosion products: gas discharge and volume ionization. Experimental results indicate the metal–insulator transition of metal can easily throttle down circuit current at a moderate degree of vaporization, resulting in a free-expanding metallic aerosol in the presence of a quasi-direct current axial electric field of kV/cm level. After dozens of μs, an anode-directed, “ionization wave” is observed inside the aerosol bubble, propagating with a speed of 3–10 km/s. Remarkably, adjustments in the electric field permit the observation of cathode-directed discharge development. Increasing the charging voltage or wire diameter promotes the overheating degree, accompanied by partial ionized striation of electro-thermal instability. With sufficient high overheating of the wire (ξ > 1), the gas discharge disappears and restrike is dominated by volume ionization.
A shock-stable rotated-hybrid Riemann solver on rectangular and triangular grids
Authors: Phongthanapanich Sutthisak , Matthujak Anirut , Ohtani Kiyonobu , Moore Elvin J.
Published: April 2024

The rotated Riemann solver is robust against the carbuncle phenomenon, especially for multidimensional computation. Moreover, hybrid techniques are usually used to enhance the stability of an accurate scheme by combining an accurate scheme with a diffusive scheme. This paper proposes a rotated-hybrid Riemann solver named the rotated-HLLC+ scheme. The scheme is developed by hybridizing the Harten–Lax–van Leer contact (HLLC) scheme with the advection upstream splitting method based on a flux vector splitting (AUSMV+) scheme by following the rotated Riemann solver approach. The unit vector n1 is calculated from the velocity-difference vector, and the unit vector n2 is the orthogonal vector. The linearized analysis suggests that the HLLC scheme should be used in the direction of n1 and the AUSMV+ scheme in the direction n2. In this way, the hybrid scheme becomes shock-stable with less numerical dissipation. Moreover, the pressure-based method is used to detect the shock wave. Several numerical experiments suggest that the pressure cutoff parameter εp=0.01 may be generally suitable and provide a stable solution with little additional numerical dissipation. The last two numerical examples show that the computational performance of the rotated-HLLC+ scheme is comparable to the HLLC scheme for the weak shock reflection over convex double wedges. However, the scheme is approximately 9% faster than the HLLC scheme for the double Mach reflection of a strong shock wave. The proposed scheme gives fast, stable, and accurate solutions on rectangular and triangular grids.
Numerical investigation of the restored oyster reef flow field with the lattice Boltzmann method
Authors: Wu Fei , Yin Zegao , Wang Yanxu , Jiang Xiutao
Published: April 2024

Oyster reefs play a dual role in the ecological and economic sustainability of global estuarine resources. Due to human activity and climate change, the prevalence of cosmopolitan oyster reefs has noticeably declined in recent decades, triggering a global restoration movement. However, the hydrodynamic functions of oyster reefs during and after restoration, particularly the impacts of growth and morphology on the flow field, remain poorly understood. This study employs the lattice Boltzmann method coupled with large-eddy simulation to simulate unidirectional flow around restored oyster reef models using the open-source Palabos library. It examines the effects of unidirectional flow velocity and reef morphology on hydrodynamic characteristics. The research analyzes spatial and temporal variations in velocity, vorticity, and turbulence structure around the reef. The findings indicated significant flow field differences between the initially restored reefs and those post-restoration. The dimensionless wake region scale parameters of the initially restored reefs exhibit hysteresis effects, generating larger turbulence during the post-recruitment stage than in the initial stage. Areas of high turbulence in the wake are associated with above-canopy flow, bypass flow, and within-canopy flow. The presence of gaps and branches in the reef leads to complex turbulence structures and irregular vortex shedding in the reef's wake at the post-recruitment stage. These results are valuable for assessing oyster reef resilience and planning effective restoration interventions.
Efficient flow reconstruction between dual tidal turbines: Large eddy simulation and reduced order modeling approach
Authors: Pant Chandra Shekhar , Grande Javier , Frankel Steven H.
Published: April 2024

The present investigation seeks to analyze the fluid dynamics associated with tidal turbines in the context of the EU (European Union) project NEMMO (The Next Evolution in Materials and Models for Ocean Energy, nemmo.eu). A pair of counter-rotating tidal turbines is employed for propelling a ship. The separation between these turbines is approximately one rotor diameter. Consequently, the power output of the downstream turbine is adversely affected by the heightened turbulence generated by the rotation of the upstream turbine. This power imbalance poses a substantial challenge in terms of power management. Therefore, this study concentrates on conducting a flow analysis of these counter-rotating turbines. Large Eddy Simulation (LES) of a dual tidal turbine rotating in opposite directions is conducted using the actuator line method. The flow is scrutinized by employing proper orthogonal decomposition (POD). The flow field is then reconstructed using the reduced order method. It is observed that a reduced number of modes is sufficient to reconstruct the flow between the tidal turbines. However, more modes are necessary to replicate the flow beyond the downstream turbine. The utilization of fewer modes proves effective in comprehending the flow at the inlet of the downstream turbine, ultimately resulting in reduced computational power requirements through faster matrix operations and lower memory usage for the POD decomposition.
Simulation of cavitation erosion damage and structural evolution caused by nano-bubbles for iron
Authors: Tan Chao , Shang Jian , Li Zhen
Published: April 2024

In this work, the dynamic behavior of nano-bubbles near the surface of single crystal iron (Fe) was investigated using molecular dynamics simulations. The cavitation erosion behavior of single crystal Fe and the structural evolution of its eroded surface was examined at different bubble diameters. The results show that nano-bubble diameter is inversely correlated with impact pressure and diameter is positively correlated with nanojet energy. The volume, surface area, and depth of cavitation pits are nearly directly proportional to the bubble diameter with correlation linear fitting coefficients of R2 = 0.9837, R2 = 0.9922, and R2 = 0.9799, respectively. Additionally, cavitation erosion induces the structural evolution of iron atoms from bcc to fcc and hcp structures. The percentage of new phase transformed is related to the bubble diameter and the type of transformed structure, the percentage of fcc and hcp structures of Fe atoms exhibits an increasing trend with the increase in the bubble diameter, and the Fe atoms of fcc structures occur an obvious increase beyond a bubble diameter of 12 nm.