bluuebunny/crossref_metadata_2025 huggingface dataset:
Jacobian-free variational method for computing connecting orbits in nonlinear dynamical systems
Authors: Ashtari Omid , Schneider Tobias M.
Published: July 2023

One approach for describing spatiotemporal chaos is to study the unstable invariant sets embedded in the chaotic attractor of the system. While equilibria, periodic orbits, and invariant tori can be computed using existing methods, the numerical identification of heteroclinic and homoclinic connections between them remains challenging. We propose a robust matrix-free variational method for computing connecting orbits between equilibrium solutions. Instead of a common shooting-based approach, we view the identification of a connecting orbit as a minimization problem in the space of smooth curves in the state space that connect the two equilibria. In this approach, the deviation of a connecting curve from an integral curve of the vector field is penalized by a non-negative cost function. Minimization of the cost function deforms a trial curve until, at a global minimum, a connecting orbit is obtained. The method has no limitation on the dimension of the unstable manifold at the origin equilibrium and does not suffer from exponential error amplification associated with time-marching a chaotic system. Owing to adjoint-based minimization techniques, no Jacobian matrices need to be constructed. Therefore, the memory requirement scales linearly with the size of the problem, allowing the method to be applied to high-dimensional dynamical systems. The robustness of the method is demonstrated for the one-dimensional Kuramoto–Sivashinsky equation.
Importance of temperature dependence of interface traps in high-k metal gate stacks for silicon spin-qubit development
Authors: Raffel Y. , Olivo R. , Simon M. , Vieler L. , Hoffmann R. , De S. , Kämpfe T. , Seidel K. , Lederer M.
Published: July 2023

While semiconductor-based spin qubits have demonstrated promising fidelities exceeding 99.9%, their coherence time is limited by the presence of charge noise. However, fast process optimization for reduced charge noise becomes challenging due to the time-consuming nature of cryogenic measurements. Hence, this work explores low frequency analysis methods to determine interface trap densities, their temperature dependence, and correlation with observed noise levels. The herein presented results provide evidence for strong temperature dependence of the interface trap density. Moreover, good agreement is observed between charge pumping and conductance-based methods. Finally, differences in temperature dependent trends of flicker noise are observed, indicating additional influences, which need to be considered for further device optimization.
RF plugging of multi-mirror machines
Authors: Miller Tal , Be'ery Ilan , Gudinetsky Eli , Barth Ido
Published: July 2023

One of the main challenges of fusion reactors based on magnetic mirrors is the axial particle loss through the loss cones. In multi-mirror (MM) systems, the particle loss is addressed by adding mirror cells on each end of the central fusion cell. Coulomb collisions in the MM sections serve as the retrapping mechanism for the escaping particles. Unfortunately, the confinement time in this system only scales linearly with the number of cells in the MM sections and requires an unreasonably large number of cells to satisfy the Lawson criterion. Here, it is suggested to reduce the outflow by applying a traveling radio frequency (RF) electric field that mainly targets the particles in the outgoing loss cone. The Doppler shift compensates for the detuning of the RF frequency from the ion cyclotron resonance mainly for the escaping particles resulting in a selectivity effect. The transition rates between the different phase space populations are quantified via single-particle calculations and then incorporated into a semi-kinetic rate equations model for the MM system, including the RF effect. It is found that for optimized parameters, the confinement time can scale exponentially with the number of MM cells, orders of magnitude better than a similar MM system of the same length but without the RF plugging, and can satisfy the Lawson criterion for a reasonable system size.
Relativistic electron bunches accelerated by radially polarized TW lasers from near-critical-density plasmas
Authors: Cheng Zhong-Ming , Wu Hui-Chun , Deng Da-Chao , Yu Ming-Young
Published: July 2023

By three-dimensional particle-in-cell simulation, we study electron acceleration by tightly focusing a few-cycle radially polarized laser onto near-critical-density plasmas. Laser ponderomotive force first pushes electrons into the target, forming a compressed electron layer and leaving behind a charge-separation field. Together with the strong longitudinal electric field of this radially polarized light, the charge-separation field accelerates the electrons backward and injects them into laser fields. The reflected light continuously accelerates these injected electrons by its longitudinal field. Simulations show that a tight quasi-monoenergetic electron bunch at 15 MeV is generated within a few micrometers.
Dynamic structure factors of polymer melts as observed by neutron spin echo: Direct comparison and reevaluation
Authors: Monkenbusch Michael , Kruteva Margarita , Richter Dieter
Published: July 2023

In this work, we compare the single chain dynamic structure factors for five different polymers: polyolefins (PE and PEP), poly-dienes (PB and PI), and a polyether (PEO). For this purpose, we have extended the De Gennes approximation for the dynamic structure factor. We describe the single chain dynamic structure factor in multiplying the coherent scattering functions for local reptation and Rouse motion within the Rouse blob. Important results are (i) the simple De Gennes structure factor S(Q, t)DG approximates within a few Å the outcome for the tube diameter of the more elaborate structure factor (exception PI); (ii) the extended De Gennes structure factor together with the Rouse blob describes the neutron spin echo spectra from the different polymers over the complete momentum transfer range and the full time regime from early Rouse motion to local reptation; and (iii) the representation of the scattering functions could significantly be improved by introducing non-Gaussianity corrections to the Rouse-blob dynamics. (iv) The microscopic tube step length in all cases is significantly larger than the rheological one; further tweaking the relation between tube length and entanglement blob size may indicate a possible trend toward an anisotropic lean tube with a step-length larger than the lateral extension. (v) All considered polymer data coincide after proper (Q, t) scaling to a universal behavior according to the length scale of the tube, while the relevant time scale is the entanglement time τe. (vi) In terms of the packing model, the required number of chains spanning the entanglement volume consistently is about 40% larger than that obtained from rheology.
Synchronization and stability analysis of an exponentially diverging solution in a mathematical model of asymmetrically interacting agents
Authors: Kato Yusuke , Kori Hiroshi
Published: July 2023

This study deals with an existing mathematical model of asymmetrically interacting agents. We analyze the following two previously unfocused features of the model: (i) synchronization of growth rates and (ii) initial value dependence of damped oscillation. By applying the techniques of variable transformation and timescale separation, we perform the stability analysis of a diverging solution. We find that (i) all growth rates synchronize to the same value that is as small as the smallest growth rate and (ii) oscillatory dynamics appear if the initial value of the slowest-growing agent is sufficiently small. Furthermore, our analytical method proposes a way to apply stability analysis to an exponentially diverging solution, which we believe is also a contribution of this study. Although the employed model is originally proposed as a model of infectious disease, we do not discuss its biological relevance but merely focus on the technical aspects.
Dynamical and statistical properties of estimated high-dimensional ODE models: The case of the Lorenz ’05 type II model
Authors: Pavšek Aljaž , Horvat Martin , Kocijan Juš
Published: July 2023

The performance of estimated models is often evaluated in terms of their predictive capability. In this study, we investigate another important aspect of estimated model evaluation: the disparity between the statistical and dynamical properties of estimated models and their source system. Specifically, we focus on estimated models obtained via the regression method, sparse identification of nonlinear dynamics (SINDy), one of the promising algorithms for determining equations of motion from time series of dynamical systems. We chose our data source dynamical system to be a higher-dimensional instance of the Lorenz 2005 type II model, an important meteorological toy model. We examine how the dynamical and statistical properties of the estimated models are affected by the standard deviation of white Gaussian noise added to the numerical data on which the estimated models were fitted. Our results show that the dynamical properties of the estimated models match those of the source system reasonably well within a range of data-added noise levels, where the estimated models do not generate divergent (unbounded) trajectories. Additionally, we find that the dynamics of the estimated models become increasingly less chaotic as the data-added noise level increases. We also perform a variance analysis of the (SINDy) estimated model’s free parameters, revealing strong correlations between parameters belonging to the same component of the estimated model’s ordinary differential equation.
Dynamic terahertz wave propagation through Al/Ni based multilayer spin valve structures
Authors: Acharyya Nityananda , Sajeev Vaishnavi , Rane Shreeya , Karmakar Subhajit , Roy Chowdhury Dibakar
Published: July 2023

Metal-based magnetic multilayers are primarily responsible for giant-magnetoresistance (GMR) that play a pivotal role in magnetic memory devices besides other spintronic applications. Spin-dependent conduction of electrons steered by spin-dependent scattering across interfaces of the ferromagnetic (FM)/nonmagnetic multilayers lies at the core of GMR phenomena. In this context, the thickness dependent magnetoresistive effect in five-layer Al/Ni/Al/Ni/Al spin valve structures is explored through contactless terahertz (THz) spectroscopy. Our experiments reveal magnetic field dependent conductivity enhancement in the multilayer configuration of a FM (nickel, Ni) layer and a nonmagnetic (aluminum, Al) spacer layer under the application of relatively low intensity magnetic fields (0–30 mT) manifesting a substantial ground for low power THz magnetism. In addition, influence of similar magnetic fields is probed for relatively thicker spacers (10 nm ≤ x ≤ 20 nm) that can form a platform for dynamically controllable THz devices. Our studies demonstrate a maximum THz peak amplitude modulation of around 48% for a 10 nm thick nonmagnetic spacer layer (Al layer) along with a significant relative modulation (∼97%) in THz conductivities. Such tuning of THz characteristics bears great potential in realizing dynamically reconfigurable THz and magnetoresistive devices by suitably exploiting multilayer spin valve configuration.
Investigation into aggregation types in a benzodithiophene–isoindigo copolymer
Authors: Asmare Eninges , Hone Fekadu Gashaw , Mammo Wendimagegn , Krüger Tjaart P. J. , Tegegne Newayemedhin A.
Published: July 2023

The type of aggregation in conjugated polymers determines their use in electronic devices. H-type aggregates are most suitable for solar cell applications, while J-type aggregates are recommended for light-emitting diodes. In this work, we used three methods to determine the type of aggregates in a benzodithiophene–isoindigo-based (PBDTI-DT) copolymer, namely, Huang–Rhys factor evolution with temperature, Franck–Condon analysis, and relative quantum yield (QY) calculation. All three methods indicate that both aggregation types are present, and the QY calculation clearly indicates that H-aggregates are more dominant. Time-dependent density functional theory was used to identify the two absorption bands of PBDTI-DT as local π − π* and intramolecular charge-transfer transitions.
Metal halide perovskites: A rising platform for gas sensing?
Authors: Hänsch Paul , Loi Maria A.
Published: July 2023

Sensing gases and volatile organic compounds is a highly requested ability in large economic fields, such as the food industry, agriculture, and health care. Depending on the foreseen specific application, electronic noses have to be sensitive, selective, highly reliable, and also robust and cheap. However, it is undoubted that rarely all these characteristics are met simultaneously and for every analyte. The current technology makes large use of metal oxide semiconductors, which exhibit many limitations, for example, in their selectivity and the need for very high temperatures to lower activation energies and reach high sensitivity [A. Dey, Mater. Sci. Eng., B 229, 206 (2018)]. This opens to investigations of further material platforms that may provide enhanced performance. Metal halide perovskites have shown a high sensitivity toward their environment, and the first gas-sensing behavior at room temperature was already demonstrated in 2016 [Fang et al., Sci. Adv. 2(7), e1600534 (2016)]. Recent reports show the huge potential of metal halide perovskites sensors for multiple gases and volatile organic compounds. Here, we will summarize what has been demonstrated until now with a metal halide perovskite and related system. We will discuss the physical mechanisms, which is the basis of sensing, and if these mechanisms have the potential to allow the development of sensors that are highly sensitive, selective, and efficient. Furthermore, we will conclude by giving a prospect for the future of gas sensors based on metal halide perovskites.
Improved voice acquisition using acoustic metamaterials
Authors: Cai Xiaobing , Wang Chunguang , Huang Zhandong , Jia Peipei , Yang Jun , Zhang Liwen
Published: July 2023

Voice acquisition and recognition are important, because sound is the most convenient and efficient media to realize seamless and hands-free human–machine interaction. Many applications, such as smart phones, humanoid robots, smart home, autonomous vehicles, and Internet of Things, demand for high-quality voice acquisition, especially in a noisy environment. In this report, we show that the evanescent portion of human voice can be amplified by setting an acoustic metamaterial in front of a microphone; thus, the signal to noise ratio can be enhanced remarkably. Such an effect is demonstrated through a double negative acoustic metamaterial slab with simultaneous negative density and bulk modulus induced by coexisting and coupled Helmholtz and Fabry–Pérot resonances. This work provides a passive and physical means, rather than the traditional active and algorithmic method, to improve the quality of voice sound acquisition.
Canard, homoclinic loop, and relaxation oscillations in a Lotka–Volterra system with Allee effect in predator population
Authors: Li Jun , Li Shimin , Wang Xiaoling
Published: July 2023

In this paper, we study the dynamics of a Lotka–Volterra model with an Allee effect, which is included in the predator population and has an abstract functional form. We classify the original system as a slow–fast system when the conversion rate and mortality of the predator population are relatively low compared to the prey population. In comparison to numerical simulation results that indicate at most three limit cycles in the system [Sen et al., J. Math. Biol. 84(1), 1–27 (2022)], we prove the uniqueness and stability of the slow–fast limit periodic set of the system in the two-scale framework. We also discuss canard explosion phenomena and homoclinic bifurcation. Furthermore, we use the enter–exit function to demonstrate the existence of relaxation oscillations. We construct a transition map to show the appearance of homoclinic loops including turning or jump points. To the best of our knowledge, the homoclinic loop of fast slow jump slow type, as classified by Dumortier, is uncommon. Our biological results demonstrate that under certain parameter conditions, population density does not change uniformly, but instead presents slow–fast periodic fluctuations. This phenomenon may explain sudden population density explosions in populations.
Point defect–dislocation interactions in BEOL-compatible Ge-on-Si epitaxy
Authors: Postelnicu Eveline , Wen Rui-Tao , Ma Danhao , Wang Baoming , Wada Kazumi , Michel Jurgen , Kimerling Lionel C.
Published: July 2023

Reduced thermal budget is required for back-end-of-line (BEOL) integration of application specific functionality into the multilevel metal stack of a processor “substrate.” We report 400 °C BEOL-compatible Ge-on-Si growth (LT Ge) that is epitaxial and single crystalline with a defect density similar to high temperature growth and a small 0.05% tensile strain. Room temperature methanol–iodine passivation is employed pre-growth in lieu of the typical 800 °C oxide removal step. Undoped LT Ge exhibits p-type conductivity initially and n-type conductivity conversion upon annealing. Hall effect measurements following post growth heat treatment between 400 and 600 °C reveal an acceptor removal reaction that follows first-order kinetics with an activation energy of 1.7 ± 0.5 eV and a pre-exponential factor of 2.3×107 s−1 consistent with a point defect, diffusion limited process. We also observe that 90° sessile dislocations identified via transmission electron microscopy are annihilated in the same temperature regime, which is evidence for point defect-mediated climb. Ensuring high-quality epitaxy by characterizing defect reactions in a BEOL-compatible Ge-on-Si process flow is key to enabling vertical integration of optical interconnects.
Steady-state junction current distribution in p-n GaN diodes measured using low-energy electron microscopy (LEEM)
Authors: Ho Wan Ying , Johnson Cameron W. , Tak Tanay , Sauty Mylène , Chow Yi Chao , Nakamura Shuji , Schmid Andreas , Peretti Jacques , Weisbuch Claude , Speck James S.
Published: July 2023

We report on the measurement of the lateral distribution of the junction current of an electrical biased p-n GaN diode by electron emission microscopy using a low-energy electron microscope. The vacuum level at the surface of the diode was lowered by deposition of cesium to achieve negative electron affinity, allowing overflow electrons at the surface of the biased diodes to be emitted and their spatial distribution imaged. The results were compared to the literature, and a good match with analytical solutions by Joyce and Wemple [J. Appl. Phys. 41, 3818 (1970)] was obtained.
Two-dimensional memristive hyperchaotic maps with different coupling frames and its hardware implementation
Authors: Wang Mengjiao , An Mingyu , He Shaobo , Zhang Xinan , Ho-Ching Iu Herbert , Li Zhijun
Published: July 2023

Continuous-time memristors have been used in numerous chaotic circuit systems. Similarly, the discrete memristor model applied to a discrete map is also worthy of further study. To this end, this paper first proposes a discrete memristor model and analyzes the voltage–current characteristics of the memristor. Also, the discrete memristor is coupled with a one-dimensional (1D) sine chaotic map through different coupling frameworks, and two different two-dimensional (2D) chaotic map models are generated. Due to the presence of linear fixed points, the stability of the 2D memristor-coupled chaotic map depends on the choice of control parameters and initial states. The dynamic behavior of the chaotic map under different coupled map frameworks is investigated by using various analytical methods, and the results show that different coupling frameworks can produce different complex dynamical behaviors for memristor chaotic maps. The dynamic behavior based on parameter control is also investigated. The numerical experimental results show that the change of parameters can not only enrich the dynamic behavior of a chaotic map, but also increase the complexity of the memristor-coupled sine map. In addition, a simple encryption algorithm is designed based on the memristor chaotic map under the new coupling framework, and the performance analysis shows that the algorithm has a strong ability of image encryption. Finally, the numerical results are verified by hardware experiments.
A new method based on pseudo-Zernike polynomials to analyze and extract dynamical and spectral information from the 2DIR spectra
Authors: Gurung Anit , Kuroda Daniel G.
Published: July 2023

Ultrafast two-dimensional infrared (2DIR) spectroscopy is a relatively new methodology, which has now been widely used to study the molecular structure and dynamics of molecular processes occurring in solution. Typically, in 2DIR spectroscopy the dynamics of a system is inferred from the evolution of 2DIR spectral features over waiting times. One of the most important metrics derived from the 2DIR is the frequency–frequency correlation function (FFCF), which can be extracted using different methods, including center and nodal line slope. However, these methods struggle to correctly describe the dynamics in 2DIR spectra with multiple and overlapping transitions. Here, a new approach, utilizing pseudo-Zernike moments, is introduced to retrieve the FFCF dynamics of each spectral component from complex 2DIR spectra. The results show that this new method not only produces equivalent results to more established methodologies in simple spectra but also successfully extracts the FFCF dynamics of individual component from very congested and unresolved 2DIR spectra. In addition, this new methodology can be used to locate the individual frequency components from those complex spectra. Overall, a new methodology for analyzing the 2D spectra is presented here, which allows us to retrieve previously unattainable spectral features from the 2DIR spectra.
A step toward correct interpretation of XPS results in metal oxides: A case study aided by first-principles method in ZnO
Authors: Li Jin , Nolan Michael , Detavernier Christophe
Published: July 2023

Metal oxide semiconductors constitute a vast group of materials whose physical properties are greatly affected by native defects. For decades, x-ray photoelectron spectroscopy (XPS) has been widely used in defect analysis. However, correct interpretation of XPS results remains a difficult task. In this work, we present a detailed first-principles study on the core-level shift of the most stable and commonly cited crystal imperfections in ZnO, including O and –OH species at the surface with different coverages and bulk defects, including O interstitial (Oi), O vacancy in the +2 charge state (Vo2+), and the neutral vacancy (Vo0). The O1s core level spectrum is simulated and compared with experiments to understand the correlation between local atomic structures and features in the O1s spectrum. In particular, our results indicate that the widely adopted assignment in the defect analysis of ZnO, which links the defect peak in XPS to Vo, the most stable defect, is very likely a misinterpretation. Theoretical analysis indicates that there are no distinguishable XPS features arising from the Vo defect. Furthermore, we show that the commonly observed defect-related peak instead arises due to Oi or specific surface configurations. Given the importance of native defects in materials performance, misinterpretation of XPS results may lead to erroneous conclusions regarding materials properties. This work provides a first-principles basis for the analysis of oxide defects through XPS.
Effect of the bottom electrode on the digital and analog resistive switching behavior of SiNx-based RRAM
Authors: Qian Mengyi , Gao Haixia , Duan Yiwei , Guo Jingshu , Bai Yifan , Zhu Shilong , Ma Xiaohua , Yang Yintang
Published: July 2023

This Letter is about the role of the bottom electrode in the resistive switching of SiNx-based resistive random-access memory. Titanium nitride (TiN) and platinum (Pt) are used as bottom electrodes to fabricate devices whose I–V characteristics are compared. The devices with Pt as the bottom electrode have digital resistive switching behavior with a main memory window. However, the devices with TiN as the bottom electrode provide an analog resistive switching with the gradual operation. We propose that this switching difference is due to the different work functions of the top and bottom electrodes and the nitrogen-rich layer formed at the SiNx/TiN interface. The work function of the bottom electrode is larger than the top electrode in the device with Pt electrodes, which are considered non-reactive. However, the difference in the work functions between the bottom and top electrodes is not much for the device with a TiN electrode. As the nitrogen-rich layer formed at the SiNx/TiN interface has nitrogen accommodation ability, the nitrogen ions are more likely to drift to the bottom electrode, and resistive switching changes from digital to analog for the device with TiN electrodes.
Temperature- and curvature-dependent surface tensions and Tolman lengths for real fluids: A mesoscopic investigation
Authors: Gong Shuai , Hu Zhiheng , Dong Lining , Cheng Ping
Published: July 2023

The curvature and temperature dependency of the liquid-vapor surface tension has a significant influence on the accurate prediction of the nanobubble/nanodrop nucleation process. In this work, a mesoscopic approach combining the pseudo-potential multiphase lattice Boltzmann method (LBM), the principle of dynamic similarity, and the van der Waals theory of corresponding states is adopted to quantitatively investigate the curvature and temperature dependency of the surface tension and Tolman length for real fluids (water and R134a). By Tolman length, we mean the distance from the surface of tension to the equimolar surface, which measures the extent by which the surface tension of a nanodrop/nanobubble deviates from the corresponding flat interface limit. We show that the Tolman lengths for flat liquid-vapor interfaces (δF) increase with the increase of temperature and are proportional to (1−Tr)−1.044. Equations for predicting surface tensions of water and R134a with effects of temperature and curvature radius taken into consideration are proposed. We demonstrate that the surface tensions increase while the Tolman lengths (δB) decrease with the increase of curvature for nanobubbles. For nanodroplets, however, the surface tensions decrease while the Tolman lengths (δD) increase with the increase of curvature. Effects of the equation of state for real fluids, which determines the interparticle interaction force in the pseudo-potential LBM, are also discussed. This mesoscopic approach can quantify the curvature dependency of liquid-vapor surface tensions for various real fluids in a wide temperature range with low computation costs, providing a new avenue for the accurate prediction of nucleation processes in micro-/nanoscale phase change heat transfer with applications to boiling, evaporation, and condensation.
Machine-learned dynamic disorder of electron transfer coupling
Authors: Wang Yi-Siang , Wang Chun-I , Yang Chou-Hsun , Hsu Chao-Ping
Published: July 2023

Electron transfer (ET) is a fundamental process in chemistry and biochemistry, and electronic coupling is an important determinant of the rate of ET. However, the electronic coupling is sensitive to many nuclear degrees of freedom, particularly those involved in intermolecular movements, making its characterization challenging. As a result, dynamic disorder in electron transfer coupling has rarely been investigated, hindering our understanding of charge transport dynamics in complex chemical and biological systems. In this work, we employed molecular dynamic simulations and machine-learning models to study dynamic disorder in the coupling of hole transfer between neighboring ethylene and naphthalene dimer. Our results reveal that low-frequency modes dominate these dynamics, resulting primarily from intermolecular movements such as rotation and translation. Interestingly, we observed an increasing contribution of translational motion as temperature increased. Moreover, we found that coupling is sub-Ohmic in its spectral density character, with cut-off frequencies in the range of 102 cm−1. Machine-learning models allow direct study of dynamics of electronic coupling in charge transport with sufficient ensemble trajectories, providing further new insights into charge transporting dynamics.
Influence of vibration on droplet dynamics in a three-dimensional porous medium
Authors: Ezzatneshan Eslam , Sadraei Reza
Published: July 2023

In this study, the effects of vibration on droplet dynamics inside a three-dimensional (3D) porous medium are investigated with a focus on frequency, amplitude, and surface wettability. A lattice Boltzmann method based on the Allen–Cahn equation (A-C LBM) is used. The results show that the volume of the drained drop and drainage duration of the droplet are significantly affected by the contact angle. The hydrophilic nature of the pores causes the droplet to spread inside the medium and resist the vibration force, resulting in a lower discharged liquid volume and delayed drainage. In contrast, a hydrophobic surface repels the droplet and leads to quicker drainage. It is also observed that the speed of droplet drained from the porous medium is higher for hydrophobic conditions, causing the separated drop to rebound and jump back toward the medium after impacting the surrounding wall boundaries. A thorough investigation is conducted on the combined implication of the surface adhesion, amplitude, and frequency of vibration on the first separation time of the droplet from the porous medium and full drainage duration. The results show that with increasing the hydrophobicity, the required vibration amplitude for complete drainage has decreased. In this way, the interplay between the adhesive force and the vibration force impedes the liquid phase separation from the hydrophilic porous medium at a low vibration amplitude. However, the results demonstrate that even in these conditions, an increase in the vibration frequency can enhance the separation and improve the drainage of the liquid phase from the pores.
Coupled three-dimensional quantum mechanical wave packet study of proton transfer in H2+ + He collisions on accurate ab initio two-state diabatic potential energy surfaces
Authors: Naskar Koushik , Ghosh Sandip , Adhikari Satrajit , Baer Michael , Sathyamurthy Narayanasami
Published: July 2023

We have carried out fully close-coupled three dimensional quantum mechanical wave packet dynamical calculations for the reaction He+H2+→HeH++H on the ground electronic adiabatic potential energy surface and on the lowest two electronic states of newly constructed ab initio calculated diabatic potential energy surfaces for the system [Naskar et al., J. Phys. Chem. A 127, 3832 (2023)]. With the reactant diatom (H2+) in its roto-vibrational ground state (v = 0, j = 0), the calculations have been carried out in hyperspherical coordinates to obtain the reaction attributes. Convergence profiles of the reaction probability with respect to the total angular momentum quantum number at different collision energies are presented for the title reaction. State-to-state as well as initial state selected integral reaction cross sections are calculated from the fully converged reaction probabilities over a range of collision energies. The integral cross section values computed using the two-state diabatic potential energy surfaces are significantly lower than those obtained using the ground electronic state adiabatic potential energy surface and are in much better agreement with the available experimental results than the latter for total energy greater than 1.1 eV. Therefore, it becomes clear that it is important to include the nonadiabatic coupling terms for a quantitative prediction of the dynamical observables.
Vibrational polariton transport in disordered media
Authors: Suyabatmaz Enes , Ribeiro Raphael F.
Published: July 2023

Chemical reactions and energy transport phenomena have been experimentally reported to be significantly affected by strong light–matter interactions and vibrational polariton formation. These quasiparticles exhibit nontrivial transport phenomena due to the long-range correlations induced by the photonic system and elastic and inelastic scattering processes driven by matter disorder. In this article, we employ the Ioffe–Regel criterion to obtain vibrational polariton mobility edges and to identify distinct regimes of delocalization and transport under variable experimental conditions of light–matter detuning, disorder, and interaction strength. Correlations between the obtained trends and recent observations of polariton effects on reactivity are discussed, and essential differences between transport phenomena in organic electronic exciton and vibrational polaritons are highlighted. Our transport diagrams show the rich diversity of transport phenomena under vibrational strong coupling and indicate that macroscopic delocalization is favored at negative detuning and large light–matter interaction strength. We also find the surprising feature that, despite the presence of dephasing-induced inelastic scattering processes, macroscopic lower polariton delocalization and wave transport are expected to persist experimentally, even in modes with small photonic weight.
Detecting driving potentials at the buried SiO2 nanolayers in solar cells by chemical-selective nonlinear x-ray spectroscopy
Authors: Horio Masafumi , Sumi Toshihide , Bullock James , Hirata Yasuyuki , Miyamoto Masashige , Nebgen Bailey R. , Wada Tetsuya , Senoo Tomoaki , Tsujikawa Yuki , Kubota Yuya , Owada Shigeki , Tono Kensuke , Yabashi Makina , Iimori Takushi , Miyauchi Yoshihiro , Zuerch Michael W. , Matsuda Iwao , Schwartz Craig P. , Drisdell Walter S.
Published: July 2023

We present an approach to selectively examine an asymmetric potential in the buried layer of solar cell devices by means of nonlinear x-ray spectroscopy. Detecting second harmonic generation signals while resonant to the SiO2 core level, we directly observe existence of the band bending effect in the SiO2 nanolayer, buried in the heterostructures of Al/LiF/SiO2/Si, TiO2/SiO2/Si, and Al2O3/SiO2/Si. The results demonstrate high sensitivity of the method to the asymmetric potential that determines performance of functional materials for photovoltaics or other optoelectronic devices.
Investigation of design parameters related to sloshing loads using smoothed particle hydrodynamics and rule-based estimations
Authors: Lee Jae-Min , Seo Hyun-Duk
Published: July 2023

This paper presents an investigation of sloshing loads acting on liquid cargo tanks based on classification rules and numerical simulations. For the design of liquid cargo tanks, sloshing load is one of the key factors that should be considered. To reduce the sloshing load and motion of the contained liquid, internal structures such as bulkheads and baffles are commonly installed in the tanks. In classification rules, methodologies to estimate the sloshing loads are proposed considering the design parameters related to these internal structure members. In this paper, we carefully investigate the limitation of classification rules through smoothed particle hydrodynamics. Our investigations focus on the impact of the design parameters on sloshing loads, the patterns of the free surface, and the characteristics of velocity distribution in the tank. Through the obtained results, it is identified that the existing classification rules lack consideration for the design parameters that affect the sloshing loads and fluid characteristics in the tank. This result provides a better understanding of the existing classification rules and their limitations. It can contribute to foundational data for the future revision of classification rules.
Single-shot quasi-phase-diversity wavefront sensing with a Fibonacci zone-plate module
Authors: Zhang Xiuping , Zhang Junyong , Li You , Zhang Yanli , Zhu Jianqiang
Published: July 2023

The phase-diversity wavefront sensor is a popular means for conducting quantitative wavefront measurements and image restoration from several desired intensity measurements. It has wide applications ranging from adaptive optics in telescopes to optical detection in high-power laser systems. In contrast to traditional phase diversity, we propose a modified version of single-shot quasi-phase-diversity wavefront sensing using a multifocal Fibonacci zone-plate module. The Fibonacci zone plate, designed to generate a specific separation distance between the in-focus and defocused diffraction planes, enables recording multiplanar diffraction patterns at a given position under a single exposure. Thus, this modified wavefront sensing can improve recovery accuracy and realize real-time measurements via a single exposure. In our experiment, a test object fabricated on a chrome plate was measured to verify the validity of the proposed single-shot quasi-phase-diversity wavefront sensing. With the advantages of simple real-time operation and improved measurement accuracy, this technique can be applied to various detection and imaging processes, such as wavefront measurements and image restoration.
Nb3SiT6 (T = S, Se, and Te) monolayers with the highly efficient catalytic performance for lithium–sulfur batteries: Insights from a first-principles study
Authors: Du Jiguang , Jiang Gang
Published: July 2023

The first-principles calculations were performed to investigate the performance of Li–S batteries on a series of two-dimensional (2D) monolayers, Nb3SiT6 (T = S, Se, and Te), Nb3GeTe6, and Ta3SiTe6. These monolayers show high kinetics of thermal stability and are accessible in the experiment. The S8/Li2Sn species can be efficiently anchored by these monolayers. The high-degree electron redistribution between Li2Sn and substrates is responsible for the moderate adsorption ability. The metallic behaviors of all monolayers studied are well maintained upon the adsorption of S8/Li2Sn. Notably, the high bifunctional catalytic activity of these monolayers is found in both the sulfur reduction reaction and the Li2S decomposition reaction. The Nb3SiT6 (T = S, Se, and Te), Nb3GeTe6, and Ta3SiTe6 monolayers with highly efficient catalytic performance could be promising anchoring materials in Li–S batteries.
Tuning the ATP–ATP and ATP–disordered protein interactions in high ATP concentration by altering water models
Authors: Mori Toshifumi , Yoshida Norio
Published: July 2023

The adenosine triphosphate (ATP)–protein interactions have been of great interest since the recent experimental finding of ATP’s role as a hydrotrope. The interaction between ATP and disordered proteins is fundamental to the dissolution of protein aggregates and the regulation of liquid–liquid phase separation by ATP. Molecular dynamics simulation is a powerful tool for analyzing these interactions in molecular detail but often suffers from inaccuracies in describing disordered proteins and ATPs in high concentrations. Recently, several water models have been proposed to improve the description of the protein-disordered states, yet how these models work with ATP has not been explored. To this end, here, we study how water models affect ATP and alter the ATP–ATP and ATP–protein interactions for the intrinsically disordered protein, α-Synuclein. Three water models, TIP4P-D, OPC, and TIP3P, are compared, while the protein force field is fixed to ff99SBildn. The results show that ATP over-aggregates into a single cluster in TIP3P water, but monomers and smaller clusters are found in TIP4P-D and OPC waters. ATP–protein interaction is also over-stabilized in TIP3P, whereas repeated binding/unbinding of ATP to α-Synuclein is observed in OPC and TIP4P-D waters, which is in line with the recent nuclear magnetic resonance experiment. The adenine ring-mediated interaction is found to play a major role in ATP–ATP and ATP–protein contacts. Interestingly, changing Mg2+ into Na+ strengthened the electrostatic interaction and promoted ATP oligomerization and ATP–α-Synuclein binding. Overall, this study shows that changing the water model can be an effective approach to improve the properties of ATP in high concentration.
Dopant ionization and efficiency of ion and electron ejection from helium nanodroplets
Authors: Asmussen Jakob D. , Ben Ltaief Ltaief , Sishodia Keshav , Abid Abdul R. , Bastian Björn , Krishnan Sivarama , Pedersen Henrik B. , Mudrich Marcel
Published: July 2023

Photoionization spectroscopy and mass spectrometry of doped helium (He) nanodroplets rely on the ability to efficiently detect ions and/or electrons. Using a commercial quadrupole mass spectrometer and a photoelectron–photoion coincidence spectrometer, we systematically measure yields of ions and electrons created in pure and doped He nanodroplets in a wide size range and in two ionization regimes—direct ionization and secondary ionization after resonant photoexcitation of the droplets. For two different types of dopants (oxygen molecules, O2, and lithium atoms, Li), we infer the optimal droplet size to maximize the yield of ejected ions. When dopants are ionized by charge-transfer to photoionized He nanodroplets, the highest yield of O2 and Li ions is detected for a mean size of ∼5×104 He atoms per nanodroplet. When dopants are Penning ionized via photoexcitation of the He droplets, the highest yield of O2 and Li ions is detected for ∼103 and ∼105 He atoms per droplet, respectively. At optimum droplet sizes, the detection efficiency of dopant ions in proportion to the number of primary photoabsorption events is up to 20% for charge-transfer ionization of O2 and 2% for Li, whereas for Penning ionization it is 1% for O2 and 4% for Li. Our results are instrumental in determining optimal conditions for mass spectrometric studies and photoionization spectroscopy of molecules and complexes isolated in He nanodroplets.
Implementing implants: delivery efficiency, contraceptive efficacy and population outcomes in two overabundant kangaroo populations
Authors: Coulson Graeme , Wilson Michelle E.
Published: July 2023

Context Overabundant native wildlife can pose serious challenges for managers. The most direct, immediate way to reduce density-dependent impacts is by culling, but lethal control often lacks public support. Fertility control offers a non-lethal management alternative. Aims We conducted two fertility-control projects on eastern grey kangaroos (Macropus giganteus), a common and widespread species in Australia. We aimed to evaluate three key components of an integrated fertility-control project, namely, delivery efficiency, contraceptive efficacy and population-level outcomes. Methods The two study sites on the urban fringe of Melbourne, Australia, were small reserves. Both had undergone an irruptive peak and subsequent crash, with negative impacts on animal health. Gresswell Forest (52 ha) is open forest habitat enclosed by a kangaroo-proof fence. Serendip Sanctuary (250 ha) is grassy woodland and retired pasture, with a boundary allowing kangaroo movement onto neighbouring properties. We captured kangaroos with a dart gun at night and treated all healthy adult females with subdermal levonorgestrel implants. Key results Delivery efficiency (catch-per-unit effort) was greater from a vehicle at Serendip Sanctuary than on foot at Gresswell Forest, with only a marginal decline over successive nights at both sites. Background fecundity was 91% at Serendip Sanctuary, but close to zero at Gresswell Forest. Treatment efficacy was high, being 86–100% infertility at Serendip Sanctuary and 96–100% at Gresswell Forest. At Serendip Sanctuary, the proportion of females treated never reached 75%, whereas only one female at Gresswell Forest remained untreated after 3 years. Population density at Serendip Sanctuary exceeded the target range 3 years after culling and fertility control. No culling occurred at Gresswell Forest, but fertility control apparently held population density at a moderate level, albeit much higher than the density target. Conclusions Future management at Serendip Sanctuary and Gresswell Forest will require a sustained fertility-control effort. Further culling may also be required to complement fertility control at Serendip Sanctuary, the larger, open site. Implications Contraceptive efficacy of levonorgestrel is high in kangaroos and implants can be delivered efficiently, but achieving control of a large, open population will be challenging.
Wrapping anisotropic microgel particles in lipid membranes: Effects of particle shape and membrane rigidity
Authors: Liu Xiaoyan , Auth Thorsten , Hazra Nabanita , Ebbesen Morten Frendø , Brewer Jonathan , Gompper Gerhard , Crassous Jérôme J. , Sparr Emma
Published: July 2023

Cellular engulfment and uptake of macromolecular assemblies or nanoparticles via endocytosis can be associated to both healthy and disease-related biological processes as well as delivery of drug nanoparticles and potential nanotoxicity of pollutants. Depending on the physical and chemical properties of the system, the adsorbed particles may remain at the membrane surface, become wrapped by the membrane, or translocate across the membrane through an endocytosis-like process. In this paper, we address the question of how the wrapping of colloidal particles by lipid membranes can be controlled by the shape of the particles, the particle–membrane adhesion energy, the membrane phase behavior, and the membrane-bending rigidity. We use a model system composed of soft core–shell microgel particles with spherical and ellipsoidal shapes, together with phospholipid membranes with varying composition. Confocal microscopy data clearly demonstrate how tuning of these basic properties of particles and membranes can be used to direct wrapping and membrane deformation and the organization of the particles at the membrane. The deep-wrapped states are more favorable for ellipsoidal than for spherical microgel particles of similar volume. Theoretical calculations for fixed adhesion strength predict the opposite behavior—wrapping becomes more difficult with increasing aspect ratio. The comparison with the experiments implies that the microgel adhesion strength must increase with increasing particle stretching. Considering the versatility offered by microgels systems to be synthesized with different shapes, functionalizations, and mechanical properties, the present findings further inspire future studies involving nanoparticle–membrane interactions relevant for the design of novel biomaterials and therapeutic applications.