bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular cloud matching in CO and dust in M33
Authors: Keilmann Eduard , Kabanovic Slawa , Schneider Nicola , Ossenkopf-Okada Volker , Stutzki Jürgen , Kobayashi Masato I. N. , Simon Robert , Buchbender Christof , Riechers Dominik , Bigiel Frank , Tabatabaei Fatemeh
Published: November 2024

Understanding the physical properties such as mass, size, and surface mass density of giant molecular clouds or associations (GMCs/GMAs) in galaxies is crucial for gaining deeper insights into the molecular cloud and star formation (SF) processes. We determine these quantities for the Local Group flocculent spiral galaxy M33 using Herschel dust and archival 12CO(2 − 1) data from the IRAM 30 m telescope, and compare them to GMC/GMA properties of the Milky Way derived from CO literature data. For M33, we apply the Dendrogram algorithm on a novel 2D dust-derived NH2 map at an angular resolution of 18.2″ and on the 12CO(2 − 1) data and employ an XCO factor map instead of a constant value. Dust and CO-derived values are similar, with mean radii of ∼58 pc for the dust and ∼68 pc for CO, respectively. However, the largest GMAs have a radius of around 150 pc, similar to what was found in the Milky Way and other galaxies, suggesting a physical process that limits the size of GMAs. The less massive and smaller M33 galaxy also hosts less massive and lower-density GMCs compared to the Milky Way by an order of magnitude. Notably, the most massive (> a few 106 M⊙) GMC population observed in the Milky Way is mainly missing in M33. The mean surface mass density of M33 is significantly smaller than that of the Milky Way and this is attributed to higher column densities of the largest GMCs in the Milky Way, despite similar GMC areas. We find no systematic gradients in physical properties with the galactocentric radius in M33. However, surface mass densities and masses are higher near the center, implying increased SF activity. In both galaxies, the central region contains ∼30% of the total molecular mass. The index of the power-law spectrum of the GMC masses across the entire disk of M33 is α = 2.3 ± 0.1 and α = 1.9 ± 0.1 for dust- and CO-derived data, respectively. We conclude that GMC properties in M33 and the Milky Way are largely similar, though M33 lacks high-mass GMCs, for which there is no straightforward explanation. Additionally, GMC properties are only weakly dependent on the galactic environment, with stellar feedback playing a role that needs further investigation.
Expansion kinematics of young clusters
Authors: Armstrong Joseph J. , Tan Jonathan C.
Published: November 2024

Context. Most stars form in clusters or associations, but only a small number of these groups are expected to remain bound for longer than a few megayears. Once star formation has ended and the molecular gas around young stellar objects has been expelled via feedback processes, most initially bound young clusters lose the majority of their binding mass and begin to disperse into the Galactic field.

Aims. This process can be investigated by analysing the structure and kinematic trends in nearby young clusters, particularly by analyzing the trend of expansion, which is a tell-tale sign that a cluster is no longer gravitationally bound and dispersing into the field.

Methods. We combined Gaia DR3 five-parameter astrometry with calibrated RVs for members of the nearby young cluster λ Ori (Collinder 69).

Results. We characterised the plane-of-sky substructure of the cluster using the Q-parameter and the angular dispersion parameter. We find evidence that the cluster contains a significant substructure but that this is preferentially located away from the central cluster core, which is smooth and likely remains bound. We found strong evidence for expansion in λ Ori in the plane of sky by using a number of metrics, but we also found that the trends are asymmetric at the 5σ significance level, with the maximum rate of expansion being directed nearly parallel to the Galactic plane. We subsequently inverted the maximum rate of expansion of 0.144−0.003+0.003 kms−1 pc−1 to give an expansion timescale of 6.944−0.142+0.148 Myr, which is slightly larger than the typical literature age estimates for the cluster. We also found asymmetry in the velocity dispersion as well as signatures of cluster rotation, and we calculated the kinematic ages for individual cluster members by tracing their motion back in time to their closest approach to the cluster centre.
PKS 1424−418: A persistent candidate source of the mm–γ-ray connection?
Authors: Kim Dae-Won , Ros Eduardo , Kadler Matthias , Krichbaum Thomas P. , Zhao Guang-Yao , Rösch Florian , Lobanov Andrei P. , Anton Zensus J.
Published: November 2024

We present a long-term strong correlation between millimeter (mm) radio and γ-ray emission in the flat-spectrum radio quasar (FSRQ) PKS 1424−418. The mm–γ-ray connection in blazars is generally thought to originate from the relativistic jet close to the central engine. We confirm a unique long-lasting mm–γ-ray correlation of PKS 1424−418 by using detailed correlation analyses and statistical tests, and we find its physical meaning in the source. We employed ∼8.5 yr of (sub)mm and γ-ray light curves observed by ALMA and Fermi-LAT, respectively. From linear and cross-correlation analyses between the light curves, we found a significant, strong mm–γ-ray correlation over the whole period. We did not find any notable time delay within the uncertainties for the mm–γ-ray correlation, which means zero lag. The mm wave spectral index values (Sν  ∝  να) between the bands 3 and 7 flux densities indicate a time-variable opacity of the source at (sub)mm wavelengths. Interestingly, the mm wave spectral index becomes temporarily flatter (i.e., α > −0.5) when the source flares in the γ-rays. We relate our results with the jet of PKS 1424−418, and we discuss the origin of the γ-rays and opacity of the inner (sub)parsec-scale jet regions.
Boxy/peanut shaping of a mature galactic bar in action-angle space
Authors: Zozulia Viktor D. , Smirnov Anton A. , Sotnikova Natalia Ya. , Marchuk Alexander A.
Published: November 2024

We study vertical resonant trapping and resonant heating of orbits. These two processes both lead to the growth of a boxy/peanut-shaped bulge in a typical N-body model. For the first time, we study this by means of the action variables and resonant angles of the actual orbits that compose the model itself. We used the resonant angle instead of the frequency ratio, which allowed us to clearly distinguish between these two processes in numerical simulations. We show that trapping and heating occur simultaneously, at least at the stage of a mature bar, that is, some orbits quickly pass through vertical resonance while at the same time, a substantial number of orbits remains trapped into this stage for a long time. Half of all bar orbits spend more than 2.5 Gyr in vertical resonance over an interval of 4 Gyr. Half of the orbits trapped into the bar over the last 3 Gyr of simulation remain captured in vertical resonance for more than 2 Gyr. We conclude that in the later stages of the bar evolution, the process of vertical trapping dominates in the ongoing process that causes the boxy/peanut shape of a bar in a typical N-body model. This contradicts the results of several recent works.
DULAG: A DUal and Lensed AGN candidate catalog with the Gaia multipeak method
Authors: Wu Q. , Scialpi M. , Liao S. , Mannucci F. , Qi Z.
Published: November 2024

Context. A series of studies have demonstrated that the Gaia multipeak (GMP) method is a very efficient technique for selecting active galactic nucleus (AGN) pair candidates. The number of candidates is determined by the size of the input AGN catalog, and is usually limited to spectroscopically confirmed objects.

Aims. The objective of this work is to compile a larger and highly reliable catalog of GMP AGN pair candidates extracted from the six million objects of the Gaia AGN catalog, the majority of which lack spectroscopic information.

Methods. In order to ascertain the differences between GMP AGN pair candidates and normal AGNs in terms of their properties, we conducted an investigation using samples of GMP AGNs. These differences were employed to establish optimal selection criteria, which ultimately led to the identification of a highly reliable candidate catalog.

Results. We find significant differences between normal AGNs and GMP AGN pair candidates in terms of their astrometry and multi-band color distribution. We compiled the DUal and Lensed AGN candidate catalog with the GMP method (DULAG), which comprises 5286 sources, and is accompanied by a highly reliable Golden sample of 1867 sources. A total of 37 sources in the Golden sample have been identified as dual AGN or lensed AGN. For the majority of sources in the Golden sample, we provide reference redshifts and find three close AGN pair candidates among them.
Analytic insight into the physics of the standing accretion shock instability
Authors: Foglizzo T.
Published: November 2024

Context. During the core collapse of a massive star, and immediately before its supernova explosion, there is amplification of asymmetric motions by the standing accretion shock instability (SASI). This imprints a frequency signature on the neutrino flux and the gravitational waves that carries direct information about the explosion process.

Aims. The physical interpretation of this multi-messenger signature requires a detailed understanding of the instability mechanism.

Methods. We carried out a perturbative analysis to characterise the properties of SASI and assess the effect of the region of neutronization above the surface of the proto-neutron star. We compared the eigenfrequencies of the most unstable modes to those obtained in an adiabatic approximation where neutrino interactions are neglected above the neutrinosphere. We solved the differential system analytically using a Wronskian method and approximated it asymptotically for a large shock radius.

Results. The oscillation period of SASI is well fitted with a simple analytic function of the shock radius, the radius of maximum deceleration, and the mass of the proto-neutron star. The oscillation period is weakly dependent on the parameterised cooling function, but this latter does affects the SASI growth rate. We describe the general properties of SASI eigenmodes using an adiabatic model. In this approximation, the eigenvalue problem is formulated as a self-forced oscillator. The forcing agent is the radial advection of baroclinic vorticity perturbations and entropy perturbations produced by the shock oscillation. We reduced the differential system defining the eigenfrequencies to a single integral equation. Its analytical approximation sheds light on the radially extended character of the region of advective-acoustic coupling. The simplicity of this adiabatic formalism opens new perspectives for the investigation of the effect of stellar rotation and non-adiabatic processes on SASI.
Fine structure and kinematics of the ionized and molecular gas in the jet and disk around S255IR NIRS3 from high-resolution ALMA observations
Authors: Zinchenko I. I. , Liu S.-Y. , Su Y.-N.
Published: November 2024

Aims. We present observations of the high-mass star-forming region S255IR, which harbors the ~20 M⊙ protostar NIRS3, where a disk-mediated accretion burst was recorded several years ago. The angular resolution of these observations, of ~15 mas, corresponds to ~25 au, which is almost an order of magnitude better than in the previous studies of this object.

Methods. The observations were performed with the Atacama Large Millimeter/submillimeter Array (ALMA) at a wavelength of 0.9 mm in continuum and in several molecular lines.

Results. In the continuum, we detect the central bright source (brightness temperature of ~850 K) elongated along the jet direction and two pairs of bright knots in the jet lobes. These pairs of knots imply a double ejection from NIRS3 with a time interval of ~1.5 years. The orientation of the jet differs by ~20° from that on larger scales, as also mentioned in some other recent works. The 0.9 mm continuum emission of the central source represents a mixture of the dust thermal emission and free-free emission of the ionized gas. Certain properties of the free-free emission are typical of hypercompact H II regions. In the continuum emission of the knots in the jet, the free-free component apparently dominates. In the molecular lines, a sub-Keplerian disk is observed around NIRS3 of about 400 au in diameter. The absorption features in the molecular lines toward the central bright source may indicate an infall. The molecular line emission appears highly inhomogeneous at small scales, which may indicate a small-scale clumpiness in the disk.
Approximate computation of acoustic reflection and shadow effects using the Kirchhoff method
Authors: Rahier Gilles , Peyret Christophe
Published: November 2024

The article presents a fairly simple way to take solid bodies into account in acoustic radiation calculations using integral methods, while still using the free-space Green’s function. The approach is based on the Kirchhoff method and on a locally plane reflection assumption. It can be applied to both analytical noise sources and acoustic disturbances provided by numerical simulations, to fixed or mobile noise sources, concentrated or widely spread in a moving medium. The time-domain formulation is an important advantage for periodic signals rich in harmonics (rotors or propellers impulsive noise) and for broadband signals (profile or jet noise). The formulation and calculation algorithm are described in detail. The method’s accuracy and limitations are shown first by comparing the results with analytical solutions for the acoustic scattering of a point source by a sphere, for a fluid at rest. An application example is then given for a wing in a Mach 0.5 flow, and the results are compared with the numerical solution of the linearized Euler equations, in the presence of a mean flow. In addition, the article proposes expressions for direct calculation of the pressure gradient by Kirchhoff and Ffowcs Williams-Hawkings surface formulations.
Regime switching on the propagation speed of travelling waves of some size-structured myxobacteria population models
Authors: Calvez Vincent , El Abdouni Adil , Estavoyer Maxime , Madrid Ignacio , Olivier Julien , Tournus Magali
Published: November 2024

The spatial propagation of complex populations can depend on some structuring variables. In particular, recent developments in microscopy have revealed the impact of bacteria heterogeneity on the population motility. Biofilms of Myxococcus xanthus bacteria have been shown to be structured in clusters of various sizes, which remarkably, tend to move faster when they consist of a larger number of bacteria. We propose a minimal reaction-diffusion discrete-size structure model of a population of Myxococcus with two possible cluster sizes: isolated and paired bacteria. Numerical experiments show that this model exhibits travelling waves whose propagation speed depends on the increased motility of clusters, and the exchange rates between isolated bacteria and clusters. Notably, we present evidence of the existence of a characteristic threshold level θ*. on the ratio between cluster motility and isolated bacteria motility, which separates two distinct regimes of propagation speed. When the ratio is less or equal than θ*, the propagation speed of the population is constant with respect to the ratio. However, when the ratio is above θ*, the propagation speed increases. We also consider a generalised model with continuous-size structure, which also shows the same behaviour. We extend the model to include interactions with a resource population, which show qualitative behaviours in agreement to the biological experiments.
Virtual scale endoscope versus snares for accuracy of size measurement of smaller colorectal polyps: a randomized controlled trial
Authors: Djinbachian Roupen , Taghiakbari Mahsa , Alj Abla , Medawar Edgard , Sidani Sacha , Liu Chen Kiow Jeremy , Panzini Benoit , Bouin Mickael , von Renteln Daniel
Published: November 2024

Accurate measurement of polyp size during colonoscopy is crucial for informing clinical decisions such as resection technique and surveillance scheduling. This study aimed to compare the accuracy of polyp size measurement when using a virtual scale endoscope (VSE) or snare-based polyp size measurement.

This randomized controlled trial enrolled 221 patients undergoing screening, surveillance, or diagnostic outpatient colonoscopies. Study subjects were randomized to have polyps detected during the colonoscopy measured for size either using the VSE or a snare of known size to estimate the size of each polyp. All polyps were measured for reference size directly after their removal from the colon using a digital caliper and before formalin fixation.

93 polyps were included in the VSE group and 102 in the snare group. The VSE demonstrated significantly higher relative accuracy (80.0% [95%CI 77.0%–82.9%]) compared with snare-based size estimation (66.4% [95%CI 62.4%–70.5%]; P < 0.001). Misclassification rates were lower with the VSE for polyps >2 mm (13.1% vs. 39.3%) and >3 mm (22.6% vs. 55.4%). For diminutive polyps, the VSE better prevented misclassification of >5 mm polyps as 1–5 mm (21.4% vs. 73.0%). The VSE also outperformed snare-based estimation in measuring within 10% of the reference standard size (30.1% vs. 18.6%) and had lower rates of size underestimation (36.5% vs. 65.7%).

Using the VSE improves the accuracy of polyp size measurement during colonoscopy in comparison with snare-based size estimation. In clinical scenarios, the VSE reduced misclassifications at clinically relevant size thresholds 2, 3, and 5 mm, which is relevant for the correct choice of polypectomy technique or when implementing resect-and-discard strategies.
Coupling Reaction of Aryl Halides with Orthoformate Ester
Authors: Shigemura Saki , Kurahashi Takuya
Published: November 2024

Herein, we report that orthoformate ester and N,N-dimethylformamide di-tert-butyl acetal can be a source of alkoxy radicals. We have developed a coupling reaction with aryl halides as a way of utilizing them. This has led to the synthesis of aromatic ethers with tertiary alkoxy groups, which are generally considered difficult to synthesize.
Effect of Time-Lapse between Intermediate Restoration and Final Restoration on Survival Rate and Changing of Radiographic Periapical Lesion
Authors: Aguilar Panuroot , Hong Tanison , Tangthong Pantharee , Phuvoravan Chalermkwan , Pinchamnankool Kriangkrai , Phumpatrakom Panupat
Published: November 2024

Objective This study aimed to assess the impact of intermediate restoration time-lapse on the survival rate and changes in radiographic periapical lesions of endodontically treated teeth.

Materials and Methods The included treatment records and periapical films of 62 patients were divided into two groups based on the time-lapse of intermediate restoration: within 4 months group (≤4 m group) and more than 4 months group (>4 m group).

Statistical Analysis Survival analysis was conducted using Kaplan–Meier and log-rank test. The predictive clinical factors were assessed using a Cox regression model and hazard ratio, considering both clinical and radiographic outcomes from the latest recall appointment. Changes in periapical index (PAI) scores on radiographs were evaluated using the Chi-square test. Statistical significance was set at p < 0.05.

Results The mean survival rate of endodontically treated teeth was 77.4%. The survival rates of the ≤4 m group and >4 m group were 83.3 and 69.2%, respectively, without statistical significance. None of the clinical factors significantly affected the clinical outcome. However, the >4 m group exhibited significantly worse changes in PAI scores between the final restoration appointment and the latest recall.

Conclusion Different time-lapses for intermediate restoration did not significantly affect the survival rate. However, an intermediate restoration time-lapse of more than 4 months tended to result in worse changes in PAI scores.
Lingual Orthodontic Retreatment of an Adult Patient with Protruded Lips and a Missing Lower Incisor: A Case Report
Authors: Nguyen Viet Anh , Pham Thi Hanh , Nguyen Thuy Anh
Published: November 2024

Orthodontic retreatment in adult patients presents unique challenges and considerations. Previous dental intervention or even missing teeth may influence treatment planning and pose challenges for bracket bonding.

A 23-year-old female patient sought orthodontic retreatment to address her chief complaint of upper lip protrusion. She had previously completed fixed labial orthodontic treatment involving the extraction of a lower central incisor.

The diagnosis was a skeletal maxillary protrusion and mandibular dentoalveolar protrusion on dental class I and skeletal class II relationships.

A nonsurgical camouflage treatment option was chosen, which involved the removal of the upper first premolars and lower right first premolar. The lower left canine, lateral, and central incisor were substituted with the lower left first premolar, canine, and lateral incisor, respectively. Lingual self-ligating brackets, straight archwires, and temporary anchorage devices were utilized. The treatment was completed after 32 months with an improved facial profile and a stable occlusion.

This case report demonstrates the successful retreatment of an adult patient with lip protrusion and relapse of lower arch crowding using straight-wire lingual appliances and premolar extractions. This approach achieved optimal aesthetics and a stable occlusion, highlighting the effectiveness of lingual appliances in complex adult retreatment cases.
Endoscopic Septostomy for Treatment of Complex Hydrocephalus: A Single Center Retrospective Cohort
Authors: Perondi Gerson Evandro , Basso Luciano Silveira , Shuha Deborah Lumi , Lindner Rafaela Jucá , Rohde Marcelo Anchieta
Published: November 2024

Objective The objective was to present the initial experience with endoscopic septostomy in a Brazilian public hospital.

Methods A retrospective analysis was conducted on patients who underwent neuroendoscopic septostomy at the Department of Neurosurgery of Cristo Redentor Hospital in Porto Alegre from 2015 to 2021.

Results In the period analyzed, 14 patients underwent endoscopic septostomy. The mean age of the patients was 41.86 years; 11 were male and 3 were female. The etiologies of hydrocephalus included ventricular inflammatory conditions, neoplasms, neurocysticercosis, and intraventricular cysts. Following septostomy, 64% of the patients exhibited clinical and radiological improvement. Complications occurred in 29% of the cases, including intraventricular hemorrhage and thalamic contusion. Four deaths were observed, all related to clinical complications or progression of the underlying disease.

Conclusion Endoscopic septostomy is an effective and safe procedure for treating complex hydrocephalus of different etiologies. Surgical outcomes are related to the learning curve with neuroendoscopy, and the benefits for patients are evident, considering the possibility of safely and effectively performing simultaneous endoscopic procedures with septostomy.
Designing effective policy to achieve sustainable development impact of FDI: the case of Sub-Saharan Africa
Authors: Olabisi Nafisat , Wei Yingqi
Published: November 2024

To optimize the sustainable development impact of foreign direct investment (FDI), developing countries must attract FDI that aligns with sustainable development characteristics. This necessitates an understanding of host governments’ expectations and the design of policies tailored to these needs. This study aims to address the gap in international business policy research by assessing FDI policy designs and identifying conditions that influence their effectiveness in attaining sustainable development outcomes. Building on a policy design fit model, we develop propositions related to the coherence of policy goals (goal coherence), the consistency of policy means (mean consistency), and the congruence between goals and means. Using crisp-set qualitative comparative analysis, we evaluate FDI policies in selected Sub-Saharan African countries. Contrary to conventional expectations, our findings reveal that while the combination of goal coherence, mean consistency, and congruence between goals and means is typically considered pertinent for policy design effectiveness, goal coherence alone is sufficient to attain FDI policy design effectiveness in the sampled countries. These results suggest that policymakers should prioritize clear, coherent goals in FDI policies to enhance sustainable development impact, potentially reducing the need for overly complex policy designs. This has implications for the formulation of future FDI strategies in similar contexts.
Causes of anomalies in superconducting transition curves
Authors: Kaminskii G. G. , Pan V. M. , Prokhorov V. G. , Taborov V. F.
Published: November 2024

A mechanism is proposed which explains the occurrence of anomalies in the electrical resistance of superconducting materials near the critical temperature. The operation of an artificial “superconducting” electrical bridge is described.
Magnetoelectric waves in ferroelectric antiferromagnets with exchange coupled electric and magnetic polarizations
Authors: Chupis I. E.
Published: November 2024

The effect of an exchange interaction between the electric and magnetic subsystems of a ferroelectric antiferromagnet on its magnetoelectric spectrum is investigated. It is shown that this interaction results in a coupling of the ferroelectric and the low-frequency spin branches in an external magnetic field. The ferroelectric frequency varies insignificantly, while a change in the spin frequency can be appreciable in strong magnetic fields. The polarization of waves in different branches of the spectrum is investigated.
Shape of the electron paramagnetic resonance (EPR) spectrum in a linear ferromagnetic Heisenberg chain
Authors: Kashcheev V. N.
Published: November 2024

The wings of an EPR line have been found in the spin-diffusion approximation in a classical ferromagnetic Heisenberg chain at low temperatures in the absence of an external magnetic field. The temperature dependence of the line center (the resonance frequency) has been determined.
Noncentral interactions and thermodynamic properties of β-O2
Authors: Burakhovich I. A. , Freiman Yu. A.
Published: November 2024

The libron spectrum and librational heat capacity of solid β-oxygen have been calculated in the quasiharmonic approximation. An fcc structure with one molecule per unit cell, with molecular centers of mass fixed at the lattice sites, and the equilibrium direction of the axes coinciding with one of the third order axes, was considered as a model of β-O2. The noncentral interaction parameters of oxygen molecules were determined by comparing theoretical and experimental results.
Superconductivity of polar multivalley semiconductors and semimetals
Authors: Gabovich A. M. , Pashitskii É. A.
Published: November 2024

Superconductivity of multivalley degenerate semiconductors and intrinsic semimetals is investigated within the framework of the model of polar current-carrier interaction with longitudinal optical phonons, taking into account the virtual interband (intervalley) transitions. Dependences are found for the critical temperature of the superconducting transition T0 on the carrier concentration, which are in qualitative agreement with experimental results for SrTiO3 and BaPb1−xBixO3.
Conductivity of an ensemble of small metallic particles
Authors: Morozov Yu. G. , Petinov V. I.
Published: November 2024

Current-flow states in granular samples consisting of small particles of tin were studied; the samples differed only in the density of packing of the tin particles. Depending on the packing density, the samples had either metallic or activated conductivity. A metal-dielectric transition was observed. The volt-ampere characteristic (VAC) and the effect of electrical breakdown on the VAC and conductivity were investigated.
Shape of electromagnetic field splashes in a metal as the electrons drift away from the limiting point
Authors: Bruk V. A. , Kaner É. A.
Published: November 2024

An asymptotically exact theory is developed for the shape of electromagnetic field splashes within a metal caused by electrons drifting away from the limiting point of the Fermi surface in an oblique magnetic field. Diffuse electron scattering at the surface of the metal is considered and the field distribution in the skin layer is in turn taken into account. The asymptotic form of the splash in its wings is found.
Electrical conductivity in the solid phase of metal-ammonia solutions
Authors: Feher A. , Jánoš Š , Shchetkin I. S. , Tarasenko G. I. , Osika E. A. , Dmitrenko I. M.
Published: November 2024

It is shown that decomposition of a nonequilibrium quenched solid solution of sodium in ammonia occurs diffusively in two stages: In the temperature range 105–120°K the second stage of time decomposition occurs with an activation energy of 0.4 eV, which is twice the activation energy of the first decomposition stage in the temperature range 75–90°K. The mechanism proposed previously for interpretation of the features of electrical conductivity in solutions of sodium in ammonia is confirmed by an independent series of experiments. It is found that the kinetics of the increase with time of the resistance in solutions of potassium and calcium in ammonia differ from those determined for sodium. In lithium solutions quenched from the liquid phase no time dependence of resistance at a temperature of 77°K was observed. Resistance as a function of temperature for potassium, lithium and calcium also differs from the sodium case.
Isotope effects and thermodynamic characteristics of quantum crystals (solid hydrogens)
Authors: Geilikman B. T. , Ivanter I. G.
Published: November 2024

The phenomenological equation for the sound velocity of isotopes of solid molecular hydrogen, involving the effect of zero-point energy, has been solved. Equations of state are obtained for these isotopes, their energy, and the Debye temperature as a function of pressure.
Fatigue strength of lead in the normal and superconducting states
Authors: Verkin B. I. , Grinberg N. M. , Lyubarskii I. M. , Pustovalov V. V. , Yakovenko L. F.
Published: November 2024

The fatigue strength of 99.9995%-pure lead at a temperature of 4.2°K in the normal and superconducting states and subjected to cyclical bending is studied. It is shown that in the superconducting state durability of lead on the average is 40% less than its durability in the normal state. Plastic strain in the superconducting state is greater per cycle than in the normal state during the initial deformation cycles. It is proposed that this difference also exists in subsequent stages of the deformation and is one of the reasons that durability is a function of the state of a superconductor.
The effect of inelastic electron relaxation on characteristics of the resistive state in a superconductive channel
Authors: Galaiko V. P.
Published: November 2024

Using the τ approximation the effect of inelastic electron collisions on the value of the upper critical field Ec2 for Cooper instability of the normal current state in a superconductive channel is considered, together with the penetration depth of the nonresonant longitudinal electric field, determined by the kinetics of the electron and hole “mixing” process in the superconductor.
Effect of electron-electron and electron-phonon interaction parameters on the superconducting transition temperature in vanadium-based alloys with A15 structure
Authors: Shtol’ts A. K. , Surikov V. I. , Gel’d P. V.
Published: November 2024

The electron-phonon and electron-electron interaction coefficients as well as the real density of states are estimated at the Fermi level N0(EF) for (V1−xCrx)3Si, (V1−xCrx)3Gr, (V1−xNbx)3Ge, V3(Si1−xGey), and V3Ga alloys. The McMillan and Dynes equations and experimental data on spin susceptibility, electronic specific heat coefficient, the Debye temperature, and the superconducting transition temperature Tc were used in the calculation. It is shown that the values of Tc of the alloys studied are determined not only by N0(EF), but also by the electron-lattice and electron-electron interactions.
Mobility of positive ions in dilute degenerate He3-He4 solutions
Authors: Shikin V. B. , Veliev Z. A.
Published: November 2024

It is shown that the dependence of the positive ion mobility μF+ on impurity excitation energy in a dilute degenerate He3-He4 solution has the form μF+∼ϵF−3/2, unlike in the hard sphere model which leads to a μF+∼ϵF−2 dependence.
Electrical resistance of tantalum at low temperatures
Authors: Ermolaev A. M. , Zlobintsev G. M. , Krasnokutskii A. V. , Merisov B. A. , Khotkevich V. I.
Published: November 2024

Results of electrical resistance measurements on two tantalum specimens of differing purity over the range 4.2−273°K are evaluated. It is established that in the range 4.2−21 °K the resistivity of tantalum is described by the function ρ0+αT4.
Magnetoresistivity of bismuth in the phonon generation regime
Authors: Bogod Yu. A. , Valeev R. G.
Published: November 2024

The influence of quantization of the electron spectrum of bismuth in a magnetic field up to 150 kOe on the volt-ampere characteristics (VAC) is investigated in the phonon generation regime at helium and hydrogen temperatures. Oscillations of the transverse magnetoresistance are detected, whose extrema are located in the neighborhood of extrema of Shubnikov–de Haas (Sh–dH) oscillations. The oscillation amplitude in the phonon generation regime has an anomalous temperature dependence for the Sh–dH effect – it grows with the passage from helium to hydrogen temperatures. It is shown that the quantity Ec/H defining the coordinate of the break in the VAC depends significantly on the temperature and magnetic field, where it varies nonmonotonically in the magnetic field, similarly to the resistivity. An attempt is made to find the regularities of the effect of exciting current oscillations in the nonlinear regime E> Ec. It turns out that the dependence of the oscillation amplitude on the drift velocity duplicates the shape of the characteristic curve for the sound amplification coefficient. An analysis is made of the experimental results. In particular, it is shown that although it qualitatively describes some individual results the theory of the amplification of ultrasound is not able to give a consistent explanation of the whole set of observed effects.
Luminescence of solid binary inert gas solutions
Authors: Belov A. G. , Fugol’ I. Ya.
Published: November 2024

Results of measuring the vacuum ultraviolet (VUV) luminescence spectra of solid binary inert gas solution in the 10−3−102 mole% concentration range are presented. The temperature dependence of the luminescence is investigated in the range from 4.2°K to the crystal sublimation temperature. An analysis is performed of the electron excitation transport mechanisms in cryocrystals of inert elements, the diffusion coefficients and the diffusion lengths of excitation shift are estimated. Excitation relaxation processes in impurities are examined as a function of the temperature and concentration of the solid solution. Peculiarities of the emission of different impurity luminescence centers are discussed.
Nonlinear dynamic properties of superconductors
Authors: Kulik I. O.
Published: November 2024

A dynamic theory of superconductivity is formulated, based directly on the self-consistent field approximation in the real time representation. A kinetic equation is introduced, and the electron-phonon collision integral is obtained. Characteristic evolution times of the uniformly perturbed order parameter are determined. Depending on the initial quasiparticle distribution, the evolution of Δ can occur during times of the order of the inverse gap Δ-1, of the inverse energy spread γ-1 of the distribution function (if γ ≪ Δ), or during the inelastic (electron-phonon) collision time τe. These collisions become important for energy spreads γ∼△/τe.
Conduction mechanisms in wüstite
Authors: Eremenko V. V. , Checherskaya L. F. , Romanov V. P.
Published: November 2024

The temperature dependences of the electrical conduction and thermal emf of wüstite (Fe1-xO) specimens with different amounts of vacancies (0.046 ≤ x ≤0.083) are measured in the temperature interval 65° to 400°K. The free carrier mobility and its temperature behavior are determined. The polaron radius and binding energy and the electron-phonon interaction constant are estimated. A conduction mechanism is suggested.
Spin waves in electron systems with paramagnetic impurities
Authors: Krasil’nikov V. V. , Yatsenko A. A.
Published: November 2024

On the basis of collisionless kinetic equations, an investigation is carried out of a new branch of the spectrum of spin waves propagating in a system of electrons which interact by s-d exchange with paramagnetic impurities. Impurity ferromagnetic ordering is taken into account by using the effective selfconsistent fields acting on the impurity and electron spins.
Calibration of MAJIS (Moons and Jupiter Imaging Spectrometer). IV. Radiometric calibration (invited)
Authors: Langevin Y. , Poulet F. , Piccioni G. , Filacchione G. , Dumesnil C. , Tosi F. , Carter J. , Barbis A. , Haffoud P. , Tommasi L. , Vincendon M. , De Angelis S. , Guerri I. , Pilorget C. , Rodriguez S. , Stefani S. , Bolsée D. , Cisneros M. , Van Laeken L. , Pereira N. , Carapelle A.
Published: November 2024

The MAJIS (Moons and Jupiter Imaging Spectrometer) instrument is an imaging spectrometer on-board the JUICE (JUpiter ICy moons Explorer) spacecraft. MAJIS covers the spectral range from 0.5 to 5.54 μm with two channels [visible–near infrared (VISNIR) and IR]. A comprehensive campaign of on-ground MAJIS calibration was conducted in August and September 2021 in the IAS (Institut d’Astrophysique Spatiale, CNRS/Université Paris-Saclay) facilities. In this article, we present the results relevant for the radiometric calibration of MAJIS. Due to the specific characteristics of the MAJIS detectors (H1RG from Teledyne), an extensive detector characterization campaign was implemented for both the VISNIR and IR detectors before integration so as to validate readout procedures providing precision and accuracy. The characterization also provided critical information on linearity and operability as a function of the integration time and operating temperature. The radiometric calibration of the integrated MAJIS instrument focused on the determination of the instrument transfer function in terms of DN output per unit of radiance for each MAJIS data element as a function of its position in the field of view of MAJIS and its central wavelength. The radiometric calibration of the VISNIR channel required a specific procedure due to stray light at short wavelengths. Observations of an internal calibration source during calibration and after launch (April 14, 2023) showed that there were minor changes in both the VISNIR and IR channels. The instrument transfer functions to be used in flight have been updated on this basis.
Strain gradient induced thermal rectification in graphene
Authors: Sai Kavuri Dheeraj Venkata , Sathian Sarith P.
Published: November 2024

Thermal rectification (TR) has attracted significant research interest due to its potential to achieve active heat control in various nanoscale applications. In this study, we propose a novel graphene-based thermal rectifier under a strain gradient. Two kinds of strain gradients, namely, compressive and tensile, are considered. We observe that under a compressive strain gradient (CSGG), the heat flows preferentially from the high-compressed region to the lower, with a significant TR of 120%. But for a tensile strain gradient (TSGG), the direction of TR is dependent on its length. For a smaller system, the TR occurs from the high-strained to low-strained region, while for larger systems, the direction of TR is reversed. The strength and location of the standing wave in conjunction with the mismatch in the overlap of the density of states in forward and reverse bias are found to induce TR in TSGG and CSGG. The TR direction is observed to be altered by changing the location of the strain gradient. Additionally, we propose a series thermal rectifier by coupling graphene under strain gradient to asymmetric defective graphene (ADG). A significant increase in the series thermal rectifier is observed when compared to TR in ADG. Our results demonstrate the applicability of strain gradient as a feasible approach to control the thermal rectification ratio and its direction for various applications such as phononic devices and thermal logic circuits.
Performance-optimized and phase purity-improved high-n quasi-two-dimensional perovskite for green light-emitting diodes
Authors: Chen Naibo , Li Yabo , Lv Shenyu , Nie Qingmiao , Lv Bin , Hu Laigui , Yan Bo
Published: November 2024

Quasi-two-dimensional (quasi-2D) perovskite has the advantage of enlarging exciton binding energy and is more suitable for efficient perovskite light-emitting diodes (PeLEDs). However, the quasi-2D perovskite films deposited with solution methods are usually mixtures of multiple phases with different inorganic layer numbers (n), unfavorable to obtaining high emission efficiency. In this study, we selected formamidinium lead bromide (FAPbBr3) as the light emitter and (2-phenylethyl)ammonium cation (PEA+) as the long-chain organic spacer cation to prepare high-n (n = 9) quasi-2D perovskite films with improved phase purity. Based on the multiple cations mixed engineering, the quality of these films improved obviously by partly replacing FA+ with minute quantities of cesium cation (Cs+). The improvement focused on remarkably enhanced photoluminescence, few low-n phases, and decreased grain sizes. The green PeLED based on the performance-optimized and phase purity-improved high-n quasi-2D perovskite reached a high brightness of 28 960 cd/m2 together with a maximum current efficiency of 44.8 cd/A and a maximum external quantum efficiency of 9.99%.
Sputtering induced the architecture of “needle mushroom” shaped Cu2O–NiCo2O4 heterostructure with novel morphology and abundant interface for high-efficiency electrochemical water oxidation
Authors: Chen Kai , Park Jaehong , Yadav Sunny , Kim Gyucheol , Dao Vandung , Uthirakumar Periyayya , Lee In-Hwan
Published: November 2024

Oxygen evolution reaction (OER) is widely recognized as a bottleneck in the kinetics and activity of decomposition water. Unique geometric design and compositional regulation are important technologies for achieving significant activity and excellent kinetics, but they continue to face obstacles in reaction thermodynamics and kinetic response. Here, a “needle mushroom” shaped Cu2O–NiCo2O4 heterostructure with abundant active sites and optimized conductivity that is grown on the Nickel-foam (NF) (labeled as Cu2O–NiCo2O4/NF-2) is prepared using advanced magnetron sputtering strategies for electrochemical water oxidation. Based on the excellent geometric advantages and efficient charge transfer capabilities, the catalyst of Cu2O–NiCo2O4/NF-2 shows superior electrocatalytic activity (low overpotential) and kinetics (low electrochemical impedance) compared with nanoneedle shaped Cu2O–NiCo2O4/NF-1 and NiCo2O4/NF for OER in alkaline medium. This work demonstrates a practical and economical strategy toward the fabrication of ternary transition metal oxides for water oxidation.
Influence of cusp-shaped magnetic fields on plasma density and thrust in an RF plasma thruster with a magnetic nozzle
Authors: Furukawa Takeru , Shimasaki Kento , Nakamoto Satoshi , Takeno Hiromasa
Published: November 2024

In a radiofrequency (RF) plasma thruster device utilizing a cusp-shaped magnetic field, we investigate the dependence of plasma parameters on operational conditions. Among the conditions, this study focused on the cusp-field condition and found that the axial profiles of the plasma parameters vary depending on the field conditions. The plasma density profile is affected by the distance between the cusp point and the position of the RF antenna. When the cusp strength increases, the cusp condition enhances plasma density and the total thrust, which is the sum of the thrust components of the electron static pressure and diamagnetic current. We propose an ideal cusp point concerning the antenna position for optimal performance in the thruster device. This paper highlights how cusp-shaped magnetic fields influence electron dynamics as an operational index of the RF plasma thruster with a magnetic nozzle.
Hybrid neMD/MC lipid swapping algorithm to equilibrate membrane simulation with thermodynamic reservoir
Authors: Szczepaniak Florence , Dehez François , Roux Benoît
Published: November 2024

Molecular dynamics (MD) simulations based on detailed all-atom models offer a powerful approach to study the structure and dynamics of biological membranes. However, the complexity of biological membranes in terms of chemical diversity presents an outstanding challenge. Particularly, difficulties are encountered when a given lipid type is present at very low abundance. While considering a very large simulation system with a small number of the low abundance lipid may offer a practical solution in some cases, resorting to increasingly large system rapidly becomes computationally costly and impractical. More fundamentally, an additional issue may be encountered if the low abundance lipid displays a high affinity for some protein in the simulation system. What is needed is to treat the simulation box as an open system in which the number of lipids can naturally fluctuate, as in the Grand Canonical Monte Carlo (MC) algorithm. However, this approach, in which a whole lipid molecule needs to be inserted or annihilated, is essentially impractical in the context of an all-atom simulation. To enforce equilibrium between a simulated system and an infinite surrounding bath, we propose a hybrid non-equilibrium (neMD)–MC algorithm, in which a randomly chosen lipid molecule in the simulated system is swapped with a lipid picked in a separate system standing as a thermodynamic “reservoir” with the desired mole fraction for all lipid components. The neMD/MC algorithm consists in driving the system via short non-equilibrium trajectories to generate a new state of the system that are subsequently accepted or rejected via a Metropolis MC step. The probability of exchanges in the context of an infinite reservoir with the desired mole fraction for all lipid components is derived and tested with a few illustrative systems for phosphatidylcholine and phosphatidylglycerol lipid mixtures.