Theoretical Predictions Research Articles

Investigation of the Optical Performance of Microchannel Plate (MCP) Collimators for the eXTP-LAD Telescope

The Enhanced X-ray Timing and Polarimetry mission (eXTP) represents a next-generation flagship satellite for X-ray astronomy. A critical component of eXTP is the Large Area Detector (LAD), which consists of 40 modules, each equipped with a set of 4x4 microchannel plate (MCP) collimators. The optical characteristics of the MCP are essential for the observational capabilities of the eXTP-LAD. In this study, we provide a detailed description of the point-to-point soft X-ray test equipment. The measurements of the point spread function (PSF) of the collimators reveal discrepancies when compared to theoretical predictions. Specifically, the full width at half maximums (FWHM) and angular resolution are larger than expected, primarily due to the channel errors. The simulation results are consistent with the measured results and demonstrate that channel errors and inner wall roughness significantly impact the optical performance of collimators.

Electrochemically Switchable Sulfurized Polyacrylonitrile for Controllable Recovery of Copper in Wastewater Based on Reversible Adsorption/Desorption Regulation.

Within the context of circular economy and industrial ecology, adsorption offers an effective manner for recycling resources from wastewater, but controllable desorption remains a challenge. Inspired by metal-thiol binding and reversible thiol-disulfide redox transformation in biological systems, this study reports the development of a reversible adsorption/desorption (RAD) system for controllable recovery of copper based on electrochemically switchable sulfurized polyacrylonitrile (SPAN). Density functional theory calculations offered theoretical prediction for the formation of S-Cu bonds and reversible weak interaction between S-S bonds and Cu2+. The SPAN anchored onto titanium suboxide ceramic foam (SPAN@TiSO) could regulate Cu2+ adsorption/desorption stimulated by the electrode potential, indicated by the adsorption capacity of 243.3 mg g-1 (30 min) at 0.2 V vs SHE and a desorption efficiency of 98.4% (5 min) at 0.8 V vs SHE. Electrochemical analysis revealed that the reversible redox transformation of S-S/-S- groups in SPAN was responsible for selective adsorption and rapid desorption in response to the electrode potential. This study provides a proof-of-concept demonstration of an electrochemically switchable polymer to build up a reversible RAD system for controllable recovery of heavy metals in wastewater, making value-added resource recovery more efficient, more intelligent, and more sustainable.

Line-shape parameters and their temperature dependence for self-broadened CO2 lines in the 300 K- 1250 K range by requantized classical molecular dynamics simulations

Line-shape parameters for self-broadened CO2 transitions are predicted for temperatures ranging from 296 K to 1250 K, using requantized molecular dynamics simulations (rCMDS). The line broadening coefficient, the speed dependence component and the first-order line-mixing coefficient for lines with rotational quantum number from 2 to 100, have been determined from fits of the rCMDS spectra with the Voigt and speed dependent Voigt profiles. These parameters and their temperature dependences were compared with recent high-quality measurements at both room and high temperatures, showing good agreements for all considered parameters. In particular, this study highlights that the temperature dependence of the speed dependent Voigt line broadening coefficient in the HITRAN database needs to be corrected. Additionally, we demonstrate that the temperature dependence for the speed dependence of the line broadening differs from that of the line broadening, contrary to the assumption widely used in the literature. These findings confirm the quality of theoretical predictions using rCMDS. The data provided can be used to complete and improve spectroscopic databases for various applications.

Evaluation of the cross sections and photoelectron angular distribution parameters following atomic photoionization under extreme conditions

In this manuscript, we report on a theoretical study of the atomic structures, cross sections, and photoelectron angular distribution parameters following the atomic photoionization under extreme conditions. To achieve this goal, a relativistic approach using the Dirac-Coulomb Hamiltonian within the framework of relativistic configuration interaction, taking advantage of independent particle basis wave functions, is proposed. To describe the interaction of charged particles in the ideal and non-ideal plasmas, the Debye potential and the pseudopotential are implemented, the latter being derived from a progressive resolution of the Bogolyubov chain equations. Both bound and continuous state wave functions, essential for a comprehensive understanding of quantum systems, are determined from the modified local central potential, which is obtained in a self-consistent manner to represent the electronic shielding effect on the nuclear potential. The photoionization processes are evaluated using the relativistic distorted wave approach, which is consistent with the principles of relativistic Dirac theory and thus provides an accurate description of the dynamics. As a test desk, the present method is applied to the evaluation of the energies, ionization potentials, wave functions, cross sections, and photoelectron angular distribution parameters, using the single photon ionization of the Li-like Fe XXIV ions as the basis for analysis. Our results demonstrate that the plasma environment effect not only decreases the ionization potentials and increases the cross sections but also affects the photoelectron angular distribution parameters across different shells, leading to a more balanced and symmetrical photoelectron distribution pattern. A detailed comparison is made between our results, and the available well-established theoretical predictions and experimental data of the unshielded case in the literature shows a good agreement. The present work provides novel insights and theoretical models that not only help us to better understand the fundamental properties of the complex systems but are also beneficial for innovative applications in the study of astrophysical and laboratory plasmas.

Carbon-anchoring synthesis of Pt1Ni1@Pt/C core-shell catalysts for stable oxygen reduction reaction

Proton-exchange-membrane fuel cells demand highly efficient catalysts for the oxygen reduction reaction, and core-shell structures are known for maximizing precious metal utilization. Here, we reported a controllable “carbon defect anchoring” strategy to prepare Pt1Ni1@Pt/C core-shell nanoparticles with an average size of ~2.6 nm on an in-situ transformed defective carbon support. The strong Pt–C interaction effectively inhibits nanoparticle migration or aggregation, even after undergoing stability tests over 70,000 potential cycles, resulting in only 1.6% degradation. The stable Pt1Ni1@Pt/C catalysts have high oxygen reduction reaction mass activity and specific activity that reach 1.424 ± 0.019 A/mgPt and 1.554 ± 0.027 mA/cmPt2 at 0.9 V, respectively, attributed to the optimal compressive strain. The experimental results are generally consistent with the theoretical predictions made by our comprehensive microkinetic model which incorporates essential kinetics and thermodynamics of oxygen reduction reaction. The consistent results obtained in our study provide compelling evidence for the high accuracy and reliability of our model. This work highlights the synergy between theory-guided catalyst design and appropriate synthetic methodologies to translate the theory into practice, offering valuable insights for future catalyst development.

Data Analysis of LHC Heavy Ion Collision for QGP Study

Abstract. By recreating the first kind of matter in the history of the universe, the quark-gluon plasma (QGP), through PbPb collisions, scientists can study the state of the early universe after the big bang. In this paper, the data from PbPb collisions collected by the Alice experiment at Large Hardron Collider is analyzed to investigate the properties of the QGP. The team focused on Fourier decomposition of azimuthal and angular correlation analysis, using data at a center-of-mass energy of 5.02 TeV per nucleon pair. The distributions of the transverse momentum p_T, the pseudo-rapidity and the azimuth angle were plotted and analyzed. The shapes of plots didnt perfectly match the predictions because of data fluctuations and the limitations of detectors. However, the trend of positive correlation between the coefficients and the transverse momentum p_T was found. The results confirm previous research findings on the collective motion and anisotropic flow of QGP. The study provides insights into the QGP's behavior and supports the theoretical predictions about its properties.

GHz voltage amplification in a stack of piezoelectric ScAlN and non-piezoelectric SiO2 layers

Abstract GHz voltage amplification was found in a stacked structure of piezoelectric layers (such as ScAlN) and non-piezoelectric layers (such as SiO2). This allows for large-area fabrication using commercial equipment. This approach contributes to wireless sensor activation. The electromechanical coupling coefficients k t 2 of the input and output layers were found to be 17.6% and 13.7%, respectively. An experimental open-circuit voltage gain of 4.5 (+13 dB) at 0.8 GHz was observed, with a maximum transmission loss (S21) of −5 dB. The experimental result shows good agreement with the theoretical prediction simulated by the electromechanical transmission line model.

A theoretical investigation on wavefronts evolution governed by the modified Nagumo equation

A myelinated nerve fiber model with nonlinear membrane capacitance is considered, and the dynamics of the system is shown to be governed by the modified discrete Nagumo equation. Within the discrete limit, we examined saltatory conduction with the possibility of the capacitive feedback parameter influencing propagation failure. The time series solutions and profile of stationary impulses are equally investigated within the continuum limit approximation. This enhances our understanding of wavefronts initiation in the myelinated fiber under uniform and non-uniform excitabilities. We employed the Bilinear Hirota method and obtained wavefront solutions of the modified Nagumo equation. It is observed that an increase in the capacitive feedback parameter favors the narrowing of wavefronts, while its speed is rapidly increased; thereby enhancing excitability and transfer of neuronal information in the whole of the myelinated axon. The influence of capacitive feedback parameter on the stability of the homogeneous states, is equally brought into sharp focus. Results of numerical simulations of the modified discrete Nagumo equation, portrays a clear concordance with the analytical predictions. This is because the speed of the propagating anti-kink increases as the capacitive feedback parameter is gradually stepped up. We hope that future experimental investigations will validate the theoretical predictions highlighted in this study.

Toward first principles-based simulations of dense hydrogen

Accurate knowledge of the properties of hydrogen at high compression is crucial for astrophysics (e.g., planetary and stellar interiors, brown dwarfs, atmosphere of compact stars) and laboratory experiments, including inertial confinement fusion. There exists experimental data for the equation of state, conductivity, and Thomson scattering spectra. However, the analysis of the measurements at extreme pressures and temperatures typically involves additional model assumptions, which makes it difficult to assess the accuracy of the experimental data rigorously. On the other hand, theory and modeling have produced extensive collections of data. They originate from a very large variety of models and simulations including path integral Monte Carlo (PIMC) simulations, density functional theory (DFT), chemical models, machine-learned models, and combinations thereof. At the same time, each of these methods has fundamental limitations (fermion sign problem in PIMC, approximate exchange–correlation functionals of DFT, inconsistent interaction energy contributions in chemical models, etc.), so for some parameter ranges accurate predictions are difficult. Recently, a number of breakthroughs in first principles PIMC as well as in DFT simulations were achieved which are discussed in this review. Here we use these results to benchmark different simulation methods. We present an update of the hydrogen phase diagram at high pressures, the expected phase transitions, and thermodynamic properties including the equation of state and momentum distribution. Furthermore, we discuss available dynamic results for warm dense hydrogen, including the conductivity, dynamic structure factor, plasmon dispersion, imaginary-time structure, and density response functions. We conclude by outlining strategies to combine different simulations to achieve accurate theoretical predictions that are based on first principles.

Hints of New Physics for the Hubble Tension: Violation of Cosmological Principle

Discrepancy between the measurements of Hubble constant H 0 from the cosmic microwave background and the local distance ladder is the most serious challenge to the standard ΛCDM model. Recent research has pointed out that it might be related with the violation of cosmological principle. Here, we investigate the impact of dipole–monopole correction on the constraints of H 0 utilizing the dipole-fitting method based on the ΛCDM model and cosmography method. Our results show that the dipole–monopole correction can reduce the constraints of H 0 from a larger value consistent with SH0ES results to a smaller value consistent with Planck results. This finding can effectively alleviate the Hubble tension. Through making redshift tomography and model-independent analyses, we confirm that our findings are independent of the redshift and cosmological model. In addition, the theoretical prediction of H(z)/(1 + z) reconstructed by the constraints of the ΛCDM model with the dipole correction is in agreement with baryon acoustic oscillation (BAO) measurements, including five Dark Energy Spectroscopic Instrument BAOs within the 1σ range except a data point at z = 0.51. Our research suggests that the Hubble tension originates from new physics beyond the standard ΛCDM model, which might lead to a violation of the cosmological principle.

Three Decades of Failed Bank Acquisitions

Using more than 30 years of data, we document that the acquisition of failed US commercial banks through FDIC-managed Purchase and Assumption (P&A) transactions leads to long-term improvements in the profitability and loan risk of the combined entity and has no detrimental effects on its capital adequacy. These results are generally stronger for transactions with greater potential for economies of scale and efficiency gains. Furthermore, geographic similarity in the branch network of the acquirer and the target marginally improves the profitability of the combined entity, while a greater business similarity between the merged banks has no effect on deal outcomes. Additional tests show that the presence of regulatory subsidies also improves the profitability of the combined entity. Finally, we find no support for theoretical predictions about the misallocation of failed bank assets in the presence of widespread failures in local markets. Our findings are important for the understanding of the consequences of bank resolution through assisted M&As.

Experimental demonstration of two types of galaxies: matter galaxies and antimatter galaxies

This paper presents a novel analysis of galaxy formation through the lens of the Small Bang Model, which posits the existence of two distinct types of galaxies generated by micro black holes: matter galaxies generated by antimatter supermassive black holes (SMBHs) and antimatter galaxies generated by matter SMBHs. The relationship between the mass of galaxies and their respective SMBHs is explored, leading to the derivation of two specific mass ratios: 918 for matter galaxies and 324 for antimatter galaxies. By using a dataset of 100 galaxies from a reliable source, the research identifies two separate subsets of galaxies with low measurement error, totaling 41 galaxies. Among these, 31 galaxies (77%) are identified as matter galaxies with a mass ratio of 918, while 10 galaxies (23%) are classified as antimatter galaxies with a mass ratio of 324. The analysis reveals that, despite measurement noise, the data aligns closely with the theoretical predictions for these two distinct types of galaxies. The research provides a strong indication that galaxies and their SMBHs are governed by fixed mass relationships, challenging the idea that these relationships are random or nonlinear. This supports the Small Bang Model, which offers a compelling alternative to the Big Bang Model, with no initial singularity and a universe emerging from a low-energy state. The findings suggest that this model not only explains the formation of spiral galaxies but also accounts for the origin of supermassive black holes at the center of each galaxy. Further study is encouraged, as this discovery opens new avenues for understanding the role of antimatter in the universe and the formation of galaxies.

Chloroplast redox state mediates the short-term regulation of leaf isoprene emission.

Isoprene emission from plants not only confers thermoprotection, but also has profound impacts on atmospheric chemistry and the climate. Leaf isoprene emission is dynamically regulated in response to various environmental cues, but the exact mechanism remains unclear. It has been proposed that chloroplast redox/energy state or cytosolic phosphoenolpyruvate carboxylation regulates isoprene biosynthesis and consequently emission, and the latter has been disproven by recent literature. However, the possible covariation of chloroplast redox/energy state and cytosolic PEP carboxylation in previous experiments impedes the independent examination of the former hypothesis. We developed an index of chloroplast redox state and showed its validity by examining the relationships between the index and the rates of certain processes which have been demonstrated to be affected or unaffected by chloroplast redox/energy state. According to the former hypothesis alone, we modelled how isoprene emission rate (IER) responded to different short-term environmental variations, and compared theoretical predictions with experimental data. We predicted that no matter which environmental factor was varied, IER would respond to the index of chloroplast redox state with similar velocities. We found that IER showed comparable increasing rates in response to the increase in the index of chloroplast redox state caused by different environmental variations (0.0479, 0.0439 or 0.0319 when ambient CO2 concentration, photosynthetic photon flux density or leaf temperature was varied, respectively). These results support that chloroplast redox/energy state regulates isoprene biosynthesis, leading to dynamic isoprene emission in nature.

Evolutionary mechanism of Y-branches in acoustic Lichtenberg figures just below the water surface

The acoustic Lichtenberg figure (ALF) in an ultrasonic cleaner with a frequency of 28 kHz at different power levels was observed using high-speed photography. The nonlinear response of the cavitation structure was analyzed by the entropy spectrum in the ALF images, which showed the modulation influence of the primary acoustic field, exhibiting the fluctuations of the bubble distribution with time. Typical Y-branches predict the paths by which surrounding bubbles are attracted and converge into the structure, the branches are curved due to bubble-bubble interactions, and the curvature increases as the bubbles are approaching the main chain. The average travelling speed of bubbles along the branches is about 1.1 m/s, almost independent of power level of the ultrasonic cleaner. A theoretical model consisting of free bubbles and a straight bubble chain of finite length was developed to explore the evolutionary mechanism of branching. It was found that the bubble trajectories showed a bending tendency similar to the experimentally observed Y-branches, and the stationary straight bubble chain parallel to the main chain could evolve into a curved chain and eventually become a branch of the main chain. The theoretical predictions agree well with the experimental results, verifying the evolutionary mechanism of Y-branches in ALF.

Give it your all or hardly give? The role of mentors' beliefs about protégé advancement potential and gender in mentoring relationships

Our research challenges assumptions about equity in formal mentoring programs. Drawing on mentoring schema and diversified mentoring theory, we theorized that mentors' beliefs about their protégés' advancement potential predict the career support they provide and the quality of their relationship, and that these effects vary by gender. Using matched-pair designs, we tested our model in two field studies of mentors and their protégés (total n = 355 dyads). Supporting theoretical predictions, mentors showed less interest in their protégés' careers, provided less career guidance, experienced less respect, and were less satisfied with their relationship when they believed their protégé had low advancement potential. Protégés also experienced less respect in their relationship when their mentor perceived them as lacking potential. Gender played a nuanced role. While mentors saw female and male protégés as having equivalent advancement potential, female protégés were seen as having less potential and experienced less respect when assigned a male rather than a female mentor. Additionally, male mentors felt more respected in their relationship when they believed their assigned protégé had high potential. Our findings challenge assumptions about the career support and respect provided in mentoring programs, offer insights about the nuanced effects of gender, and call for interventions that help organizations fulfill the promise of mentoring.

Multiplet XPS analysis of the Mn 2p for Mn3O4 thin films

In this work, we performed a detailed analysis of the x-ray photoemission spectroscopy (XPS) of the Mn 2ppeak for Mn3O4(001) thin films. This is a challenging task since Mn3O4is composed of two different cations, Mn2+at tetrahedral and Mn3+at octahedral sites, which both contribute to the XPS spectra. The oxide spectra consist of many multiplets arising from the angular momentum coupling of the open Mn 2pand 3dshells, thus increasing the spectrums' complexity. Moreover, the energy spacing and intensities of the different multiplets also reflect the covalent mixing between Mn 3dand O 2pshells. However, we show that a detailed analysis, which provides relevant information about the cations in the oxide structure, is possible. We prepared experimentally different Mn3O4films on Au(111), and their structure was monitored with the diffraction pattern obtained with low-energy electron diffraction. The Mn 2pspectra were fit, guided by cluster model theoretical predictions, and checked for films prepared at different oxygen partial pressures. Therefore, we could observe the Mn2+and Mn3+cations' relative concentration in the Mn 2pmains peaks.

Calculation of collisional line-broadening and shifting of acetylene using Complex Robert–Bonamy–Ma approach

A comprehensive semi-classical study of the collisional line broadening and shift coefficients of C2H2 by several key perturbers (H2, He, N2, C2H2, CO, and CO2) for astronomical applications using the Complex Robert–Bonamy–Ma (CRBM) framework is presented. Following the CRBM computational protocol, the intermolecular interaction potentials are constructed from atom-atom and electrostatic interactions, and then fitted to reproduce experimental room-temperature line-broadening parameters taken from the literature. In total, 657 experimental values are used in the fitting. The empirical potentials are then used to predict line broadening coefficients over a wide temperature range. Reference collisional line widths γ0 and temperature exponents n for the commonly used single-power law are produced, as well as a set of parameters for the double-power law, which better reproduces the temperature dependence of theoretical predictions. The vibrational dependence of the line widths is studied using a new ab initio isotropic polarizability surface of C2H2 and is found to be negligible. The computed line broadening parameters are found to agree well with the experimental data, while the modelling of line shits of HCCH is not satisfactory when compared to the experiment. The new line broadening data of C2H2 with the J (or m) dependence have been used to populate the ExoMol database www.exomol.com as part of the ExoMol pressure-broadening diet and can be used to model opacities of atmosphere of (extrasolar) planets. The CRBM methodology tested here on C2H2 can be used for other similar (closed-shell) systems in ExoMol that are important for exoplanetary atmospheric studies.

The effect of aspect ratio and mass ratio on the flow-induced flutter of a thin flexible sheet

This study experimentally investigates the flow-induced flutter of a thin flexible sheet, focusing on how the sheet's aspect ratio and mass ratio affect its stability and flutter characteristics in the post-critical regime. The flutter frequency of the sheet was obtained using hotwire measurements, while flutter amplitude and mode shape were acquired through high-speed imaging. The flowfield around the flapping sheet was analyzed using particle image velocimetry (PIV). Based on experimental observations, we report the onset of flutter as a subcritical bifurcation with hysteresis. The dynamic characteristics of the sheet play a significant role in its flutter instability, with the onset and cessation of flutter occurring at a frequency close to the sheet's second-mode natural frequency. The results show that both aspect ratio and mass ratio significantly affect the critical wind speed and flutter characteristics in the post-critical regime. Both flutter frequency and amplitude decrease as the aspect ratio decreases. PIV measurements in various planes reveal the highly three-dimensional nature of the flow. Results from off-axis PIV show a pair of counter-rotating spiral vortices in the wake that oscillate and change orientation with the sheet's movement. Additionally, a theoretical analysis was conducted to derive an approximate analytical relationship between the aspect ratio and critical wind speed. Experimental results aligned well with theoretical predictions for sheets with low aspect ratios (aspect ratio ≤1) but deviated for sheets with higher aspect ratios (aspect ratio >1). The relevant scaling parameters have also been explored to represent the experimental data in a non-dimensional form.

Active Site Customizing of Metal-Organic Materials for Highly Efficient Oxygen Evolution.

Elucidating the correlation of active sites and catalytic activity in multi-component metal-organic frameworks (MOFs) is key to understanding the mechanism of oxygen evolution reaction (OER), yet it remains nebulous. Herein, a direct pathway combining theoretical prediction with anchoring high-valence metals is proposed on MOFs to reveal the mechanism of the OER reaction. Density functional theory (DFT) predicts that the co-modulation by Mo and Co atoms can enhance the conductance of CoMOF and optimize the adsorption-free energies of the OER intermediates. Guided by the theoretical prediction, the Co-based MOFs grown on Ni foams are doped with high valence Mo, which is used as model catalysts for the quantitative study of the composition-dependent OER performance. With Co/Mo in the ratio of 5:1 for the highest OER activity (impressively overpotential of 324mV at 100mA cm-2 and a Tafel slope of 96.07mV dec-1) and excellent stability (maintains for 200h at 100mA cm-2), the catalysts in this work is superior to commercial benchmarks electrocatalysts (RuO2/NF, 420mV, 199.12mV dec-1). This work sheds light on the tailoring of the active sites of MOFs, which is highly correlated with the activity of the OER.

Multifluid Theory of Electrostatic Ion Cyclotron Waves in Partially Ionized Plasmas

Partially ionized plasmas universally exist in various astrophysical environments, such as the solar atmosphere and the E region of the ionosphere. In these contexts, the existence and propagation of waves in plasmas could be significantly influenced by effects of weakly ionized plasma (e.g., ion–neutral collisions). In this work, we investigate electrostatic ion cyclotron (EIC) waves in partially ionized plasmas based on the multifluid model with adiabatic electrons. Two distinct branches of EIC waves coexist in partially ionized plasmas: one branch is the conventional EIC waves; the other branch propagates around the “effective ion cyclotron frequency” which originates from self-consistent ion–neutral collisions. Furthermore, theoretical predictions in the new branch of EIC waves are qualitatively consistent with laboratory observations. In addition, a comparison between our theory and the previous work is also performed. This work can aid in understanding the acceleration and transverse heating of ions in partially ionized astrophysical plasmas where the ion–neutral collisions are frequent.