bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Magnetic Resonance Direct Thrombus Imaging for the Diagnostic Management of Suspected Thrombosis in Routine Clinical Practice
Authors: de Jong Cindy M.M. , van Dam Lisette F. , Dronkers Charlotte E.A. , Eikenboom Jeroen , den Exter Paul L. , ter Haar Sophie N.M. , van Haren Guido R. , Huisman Menno V. , van Mens Thijs E. , Stöger J. Lauran , Kroft Lucia J.M. , Klok Frederikus A.
Published: June 2024

Background The noninvasive magnetic resonance direct thrombus imaging (MRDTI) technique can be used to diagnose acute deep vein thrombosis (DVT), without the use of intravenous contrast. MRDTI holds the potential to differentiate between acute and chronic DVT and could be helpful when diagnosing thrombosis is challenging.

Objectives Our objective was to evaluate the application of MRDTI in clinical practice, including the frequency and indications of MRDTI scans performed in practice-based conditions, results, impact on treatment decisions, and associated patient outcomes.

Methods A retrospective study was performed at the Leiden University Medical Center, the Netherlands. MRDTI scans performed since its implementation in patients aged ≥18 years as part of clinical practice for the diagnostic management of suspected thrombosis were evaluated.

Results Between October 2015 and September 2023, 36 patients had undergone MRDTI for the diagnostic evaluation of thrombosis. MRDTI application increased since 2019 (five–eight scans per year). The most common indication was to differentiate between acute and chronic thrombosis, mainly for suspected recurrent ipsilateral DVT after inconclusive compression ultrasonography. In over a third of patients, acute thrombosis was confirmed by MRDTI. MRDTI results determined treatment decisions in all except two patients. One patient had symptomatic thrombosis of the lower extremity within 3 months after an MRDTI of the upper extremity without signs of acute thrombosis (1/23; 4.3%, 95% confidence interval: 0.77–21).

Conclusion Over the past 4 years, MRDTI has been used increasingly in our hospital. MRDTI results guided treatment decisions, which confirms the clinical impact and feasibility of its application in daily practice.
Colorectal tumor comorbidity is common in patients with duodenal tumors: Exploratory cross-sectional study
Authors: Mizutani Mari , Kato Motohiko , Yamanoi Kazuhiro , Matsubara Akiko , Nakayama Atsushi , Fukuhara Kayoko , Iwata Kentaro , Miyazaki Kurato , Masunaga Teppei , Kubosawa Yoko , Hayashi Yukie , Takatori Yusaku , Akimoto Teppei , Matsuura Noriko , Bessho Rieko , Sujino Tomohisa , Takabayashi Kaoru , Ichikawa Hitoshi , Kashiwagi Kazuhiro , Takaishi Hiromasa , Sato Yasunori , Kanai Takanori , Kushima Ryoji , Yahagi Naohisa
Published: June 2024

Background and study aims The duodenum and colorectum are target organs for familial colorectal adenomatous polyposis, however, the association of duodenal epithelial tumors (DETs) and colorectal tumors is still controversial. The aim of our study was to elucidate the association between DET and colorectal tumor.

Patients and methods This was an exploratory cross-sectional study of patients with DETs treated by endoscopic resection at our hospital, between November 2018 and October 2022. Individuals who underwent colonoscopy as part of the health screening comprised the reference control group for comparison. In both groups, lesions suspected of being tumors were resected. The main outcome was the adenoma detection rate (ADR). Other outcomes were the detection rate for advanced neoplasia (AN) and risk factors for colorectal adenoma and AN, evaluated using univariate and multivariable analyses.

Results Analyses were based on data from 163 individuals in the DET group and 177 in the control group. ADR was higher in the DET (63.2%) than in the control (23.6%) group (P < 0.001). AN and invasive cancer rates were also significantly higher in the DET than in the control group (AN: 20.9% vs 3.4%, respectively, P < 0.001; invasive cancer: 3.1% vs 0%, respectively, P < 0.001). On logistic regression analysis, DET was found to be associated with a 5-fold increase in the detection rate of adenoma and 6-fold increase in AN detection.

Conclusions The study revealed significant association between DET and high ADR and a higher frequency of AN and invasive cancer. Screening colonoscopy is suggested for patients with DETs.
Efficient Synthesis of Fluorene Derivatives by Benzannulation of Indene Dienes with Benzoylacetonitrile Catalyzed by Lipase
Authors: Zhao Rui , Wang Zhi , Shi Wenhan , Wang Yiyao , Li Fengxi , Xie Hanqing , Wang Lei
Published: June 2024

An enzymatic method was developed for the synthesis of fluorene derivatives by benzannulation of indene dienes with benzoylacetonitrile in a nonaqueous solvent. Under the optimal reaction condition [indene diene (0.5 mmol), benzoylacetonitrile (0.5 mmol), ethanol (2 mL), lipase from porcine pancreas (5 mg), 50 °C, 24 h], fluorenes bearing various groups were obtained in satisfactory yields (83–93%). This method not only offers a significant advancement in the synthesis of fluorene derivatives, but also represents a new application of lipase in promiscuous enzyme catalysis.
Repetitive Subconcussive Head Impacts in Sports and Their Impact on
Brain Anatomy and Function: A Systematic Review
Authors: Hack Lukas , Singh Bhagyashree , Binkofski Ferdinand , Helmich Ingo
Published: June 2024

Repetitive subconcussive head impacts occur regularly in sports. However, the
exact relationship between their biomechanical properties and their consequences
on brain structure and function has not been clarified yet. We therefore
reviewed prospective cohort studies that objectively reported the biomechanical
characteristics of repetitive subconcussive head impacts and their impact on
brain anatomy and function. Only studies with a pre- to post-measurement design
were included. Twenty-four studies met the inclusion criteria. Structural white
matter alterations, such as reduced fractional anisotropy and an increase in
mean diffusivity values, seem to be evident in athletes exposed to repetitive
subconcussive head impacts exceeding 10 g. Such changes are observable after
only one season of play. Furthermore, a dose-response relationship exists
between white matter abnormalities and the total number of subconcussive head
impacts. However, functional changes after repetitive subconcussive head impacts
remain inconclusive. We therefore conclude that repetitive subconcussive head
impacts induce structural changes, but thus far without overt functional
changes.
Telephone-based application of the Activities of Daily Living Questionnaire in patients with Parkinson's disease
Authors: Rocha Rafaela Moura Santos , Faria-Fortini Iza de , Scalzo Paula Luciana
Published: June 2024

Background The Activities of Daily Living Questionnaire (ADLQ) focuses on assessing the ability to perform activities of daily living (ADLs) based on the self-perception of individuals with Parkinson's disease (PD). A Brazilian Portuguese version of the questionnaire is available (ADLQ-Brazil), and further investigation is needed to fully assess its measurement properties.

Objective To investigate construct and concurrent validity of the telephone-based administration of the ADLQ-Brazil with community individuals with PD.

Methods There were 50 adults with PD (mean age: 68 ± 9.5 years) invited to answer the ADLQ-Brazil on two randomized occasions, face-to-face and by telephone, 7 to 10 days apart. Clinical-based measures including the Movement Disorder Society-Sponsored Revision of the Unified Parkinson Disease Rating Scale, Timed Up and Go Test, Nine Hole Peg Test, Mini-Balance Evaluation Systems Test, Apathy Scale, Beck Depression Inventory, Modified Fatigue Impact Scale, and Parkinson Disease Quality of Life Questionnaire were applied during the first session, to establish construct validity.

Results The total scores on the ADLQ-Brazil were significantly associated with the clinical-based measures, thus providing evidence of construct validity. No significant differences were observed between the mean scores obtained with the face-to-face and telephone-based administration of the questionnaire (95%CI = 0.997). A high level of agreement was found in the total scores obtained between both applications of the ADLQ-Brazil (95%CI = 0.994–0.998), and most of the individual items had, on average, moderate agreement.

Conclusion The findings provide psychometric support for the ADLQ-Brazil as a telephone interview to assess the performance of ADLs in individuals with PD.
Effects of CSR-Related Media Coverage on Corporate Reputation
Authors: Ennenbach Sabrina , Barkela Berend
Published: June 2024

Based on framing and attribution theory, this study explores the mediator role of CSR skepticism within the relation of media coverage about corporate social responsibility (CSR) activities on reputation and brand attitudes. Within this investigation, we also explore framing and negativity effects. We conducted an experimental design (German speaking sample, N = 207) using media reports on environmental CSR of a (fictitious) airline company. Our results demonstrate that effects on reputation are fully mediated by CSR skepticism, and effects on brand attitudes are partly mediated by CSR skepticism. Additionally, reputation and brand attitudes are contingent with positive and negative valence of media framing and a negativity bias can be found for framing effects on brand attitudes.
CEO overseas experience, dynamic capabilities and corporate digital transformation: An imprinting theory perspective
Authors: Xu Zhaocheng , Hou Jingchuan
Published: June 2024

The drivers of corporate digital transformation have been the focus of industry and academic attention. To deeply explore the driving factors and influencing mechanisms of corporate digital transformation (CDT), this paper takes Chinese listed manufacturing companies from 2007–2021 as the research object, based on imprinting theory, adopts the Driscoll-Kraay standard error method, examines the impact of CEO overseas experience on CDT, analyzes the moderating mechanisms of market competition and organizational resources, as well as the mediating effect of dynamic capabilities. The study shows that CEO overseas experience significantly promotes CDT, while market competition intensity and organizational slack resources strengthen the above relationship. Dynamic capabilities play a mediating role in the relationship between CEO overseas experience and CDT. The above findings still hold after considering robustness tests and endogeneity treatments. Further research finds that the overseas working experience of a CEO outweighs the learning experience when it comes to CDT; a CEO with overseas experience has a more significant influence on CDT in the company with a low growth rate; when the CEO is also the chair of the board in the executive team of a company, the overseas experience matters more to CDT; the overseas experience of CEOs with deep academic backgrounds has a more significant impact on CDT. This paper states the driving mechanism of corporate digital transformation from the imprinting theory perspective, and the findings are proven to be substantial and offer practical value for the in-depth development of corporate digital transformation.
A meta-analysis of the effects of design thinking on student learning
Authors: Yu Qing , Yu Kun , Lin Rongri
Published: June 2024

Design thinking (DT) is becoming an innovative and popular teaching method. Recently, DT has been used as an unconventional method to develop skills of problem-solving, creativity, and innovation. However, its effects on student learning are unclear. This research aimed to examine the DT’s effects on student learning. The meta-analytic result based on 25 articles showed that DT positively affected student learning (r = 0.436, p < 0.001). Moreover, the learning outcome, treatment duration, grade level, DT model, and region had moderating effects. Additionally, moderator analysis suggested that DT instruction was more effective: (1) when class size is <=30; (2) on multidiscipline; (3) with long-term duration (>=3 months); (4) for secondary school and university students; (5) on student learning engagement, motivation, problem-solving skills, and academic achievement; (6) with the model of Observe, Synthesize, Ideate, and Prototype, and Empathize, Define, Ideate, Prototype, Test; (7) when team size is <=7; (8) on African and Asian students.
Key traits of top answerers on Korean Social Q&A platforms: insights into user performance and entrepreneurial potential
Authors: Jang Moonkyoung , Kim Seongcheol
Published: June 2024

Despite the proliferation of tools available to search for information online, such as search engines and generative artificial intelligence (AI), many people still actively use social question-and-answer (Q&A) platforms. This study examines the best answerers on Korean social Q&A platforms as key content producers and potential entrepreneurs. The characteristics of the best answerers, who are the core contributors to social Q&A platforms, were analysed based on the 903 best answerers from the social Q&A platform Naver Knowledge-iN, a leading social Q&A platform in South Korea. Research hypotheses were formulated based on three key dimensions: the intrinsic characteristics of the answers (length, immediacy, and similarity with the question), attributes of the answerer (self-introduction, credentials beyond the social Q&A platform), and level of engagement of the answerer on the platform (variety in the field of answers, diversity in role activities on the platform). An in-depth analysis using a multiple regression model was conducted to test the hypotheses. The findings of the analysis results indicate that enhanced user performance is positively correlated with several factors. Specifically, longer answers, high similarity between questions and answers, additional credentials beyond the social Q&A platform, a broader range of fields answered, and active participation as both asker and answerer all contribute to improved user performance. These findings highlight what sets social Q&A platforms apart from other search tools such as search engines or generative AI chatbots. This study has practical implications for social Q&A platforms seeking to identify the best contributors who are likely to produce quality content and are potential entrepreneurs.
Local modules in braided monoidal 2-categories
Authors: Décoppet Thibault D. , Xu Hao
Published: June 2024

Given an algebra in a monoidal 2-category, one can construct a 2-category of right modules. Given a braided algebra in a braided monoidal 2-category, it is possible to refine the notion of right module to that of a local module. Under mild assumptions, we prove that the 2-category of local modules admits a braided monoidal structure. In addition, if the braided monoidal 2-category has duals, we go on to show that the 2-category of local modules also has duals. Furthermore, if it is a braided fusion 2-category, we establish that the 2-category of local modules is a braided multifusion 2-category. We examine various examples. For instance, working within the 2-category of 2-vector spaces, we find that the notion of local module recovers that of braided module 1-category. Finally, we examine the concept of a Lagrangian algebra, that is a braided algebra with trivial 2-category of local modules. In particular, we completely describe Lagrangian algebras in the Drinfeld centers of fusion 2-categories, and we discuss how this result is related to the classifications of topological boundaries of (3 + 1)d topological phases of matter.
A geometric formulation of Schaefer’s theory of Cosserat solids
Authors: Németh Balázs , Adhikari Ronojoy
Published: June 2024

The Cosserat solid is a theoretical model of a continuum whose elementary constituents are notional rigid bodies, having both positional and orientational degrees of freedom. In this article, we present a differential geometric formulation of the mechanics of a Cosserat solid, motivated by Schaefer’s “motor field” theory. The solid is modeled as a special principal fiber bundle (a Cartan space) and its configurations are related by bundle maps. We show that the classical Lagrangian strain measure of a Cosserat solid is the difference of two Cartan connections on the bundle. The infinitesimal strain is derived by a rigorous linearization and is revealed to be the Lie derivative of a Cartan connection along the vector field representing the infinitesimal deformation. Incompatibilities in a Cosserat solid are characterised by a non-flat Cartan connection whose curvature is recognized as the density of topological defects. Stresses are defined as vector bundle-valued differential forms that are work-dual to strains and balance laws in the limit of vanishing inertia are obtained via a d’Alembert principle. Constitutive equations, with an emphasis on recent applications to active oriented solids, are briefly discussed.
Electric space charge threshold observation in polyurethane under high electric fields
Authors: Diguet Gildas , Cavaillé Jean-Yves , Coativy Gildas , Courbon Joel
Published: June 2024

Polyurethanes have been extensively studied for their strong electromechanical response. Previous studies have mainly investigated the impact of electrical charges on these polymers' DC conductivity, which was measured on the order of 10−10 S/m. The movement of electric charges is responsible for the macroscopic deformation of polymer films under an electric field. However, this study focused primarily on electric fields below 107 V/m, where the electric current complies with Ohm's law. In this paper, we examine the electric current above this field value and observe a deviation in the current from linearity with the applied field, especially for a high electric field of 106–107 V/m. This change is known in polymers under high electric fields but has never been observed in polyurethane. This suggests the injection of electrode charges into the polymer material. This article provides the threshold at which the transition occurs from linear (Ohm's law) to nonlinear conduction as a result of injected electric charges.
High-efficient spin injection in GaN through a lattice-matched tunnel layer
Authors: Chen Mingyu , Huang Shiming , Jiang Wei , Wu Qipeng , Tan Peng , Zhang Chenhao , Fu Deyi , Li Xu , Wu Zhiming , Wu Yaping , Zhang Rong , Kang Junyong
Published: June 2024

Semiconductor spintronics has brought about revolutionary application prospects in future electronic devices. The tunnel junction plays a key role in achieving efficient spin injection in semiconductors. This work employed the GaN semiconductor as a room-temperature spin injection system, taking advantage of its weak spin–orbit coupling and spin scattering. By introducing a lattice-matched AlN barrier layer to improve the tunneling interface, advanced spin injection and transport were realized compared with traditional oxide barriers. The spin polarization was further improved by modulating the applied bias, and a bias-controlled tunneling enhancement mechanism was revealed. Consequently, we demonstrated a high record of spin polarization of 20.5%. This work paves a feasible route for achieving efficient spin injection and transport in GaN, which will further promote the development of room-temperature and high-performance spintronic devices.
Rapid synthesis of MoS2 for transistors and memristors
Authors: Lin Weiyi
Published: June 2024

This study presents a rapid synthesis method using carbon fibers, converting ammonium tetrathiomolybdate to molybdenum disulfide films with controllable thickness (1–5 nm) and smooth surface (200 pm on average) in tens of seconds. Electronic devices based on these multilayers exhibit promising performance: memristors operate at an average of 1.5 V; field-effect transistors display electron mobility ranging from 0.1 to 0.4 cm2/V·s with a 103 on/off ratio. The electrical performance can be enhanced by optimizing annealing recipes. This scalable, time-efficient method holds the potential for large-scale production of multilayer two-dimensional semiconductors for electronics.
Mutual averaged non-commutativity of quantum operator algebras
Authors: Zanardi Paolo
Published: June 2024

We introduce an elementary measure of non-commutativity between two algebras of quantum operators acting on the same Hilbert space. This quantity, which we call Mutual Averaged Non-commutativity (MAN), is a simple generalization of a type of averaged Out-of-Time-Order-Correlators used in the study of quantum scrambling and chaos. MAN is defined by a Haar averaged squared norm of a commutator and for some types of algebras is manifestly of entropic nature. In particular, when the two algebras coincide the corresponding self-MAN can be fully computed in terms of the structural data of the associated Hilbert space decomposition. Properties and bounds of MAN are established in general and several concrete examples are discussed. Remarkably, for an important class of algebras, —which includes factors and maximal Abelian ones—MAN can be expressed in the terms of the algebras projections CP-maps. Assuming that the latter can be enacted as physical processes, one can devise operational protocols to directly estimate the MAN of a pair of algebras.
The QG limit of magnetohydrodynamic rotating shallow water system
Authors: Fang Yue , Wang Jiawei , Wang Xiao , Xu Xin
Published: June 2024

Magnetohydrodynamic rotating shallow water system (MRSW) is a proposed model for a thin layer of electrically conducting fluid, which plays an important role in astrophysical plasma studies. For the spatial periodic domain, a mathematically rigorous framework is developed for deriving reduced systems for MRSW equations with general unbalanced initial data. It is shown that the reduced slow dynamics are the magnetohydrodynamic quasi-geostrophic equations.
ENN's roadmap for proton-boron fusion based on spherical torus
Authors: Liu Min-sheng , Xie Hua-sheng , Wang Yu-min , Dong Jia-qi , Feng Kai-ming , Gu Xiang , Huang Xian-li , Jiang Xin-chen , Li Ying-ying , Li Zhi , Liu Bing , Liu Wen-jun , Luo Di , Peng Yueng-Kay Martin , Shi Yue-jiang , Song Shao-dong , Song Xian-ming , Sun Tian-tian , Tan Mu-zhi , Wang Xue-yun , Yang Yuan-ming , Yin Gang , Zhao Han-yue
Published: June 2024

ENN Science and Technology Development Co., Ltd. (ENN) is committed to generating fusion energy in an environmentally friendly and cost-effective manner, which requires abundant aneutronic fuel. Proton-boron (p-11B or p-B) fusion is considered an ideal choice for this purpose. Recent studies have suggested that p-B fusion, although challenging, is feasible based on new cross section data, provided that a hot ion mode and high wall reflection can be achieved to reduce electron radiation loss. The high beta and good confinement of the spherical torus (ST) make it an ideal candidate for p-B fusion. By utilizing the new spherical torus energy confinement scaling law, a reactor with a major radius R0=4 m, central magnetic field B0=6 T, central temperature Ti0=150 keV, plasma current Ip=30 MA, and hot ion mode Ti/Te=4 can yield p-B fusion with Q>10. A roadmap for p-B fusion has been developed, with the next-generation device named EHL-2. EHL stands for ENN He-Long, which literally means “peaceful Chinese Loong.” The main target parameters include R0≃1.05 m, A≃1.85, B0≃3 T, Ti0≃30 keV, Ip≃3 MA, and Ti/Te≥2. The existing ST device EXL-50 was simultaneously upgraded to provide experimental support for the new roadmap, involving the installation and upgrading of the central solenoid, vacuum chamber, and magnetic systems. The construction of the upgraded ST fusion device, EXL-50U, was completed at the end of 2023, and it achieved its first plasma in January 2024. The construction of EHL-2 is estimated to be completed by 2026.
A new hybrid reduced order modeling for parametrized Navier–Stokes equations in stream-vorticity formulation
Authors: Zhang Tao , Xu Hui , Guo Lei , Feng Xinlong
Published: June 2024

In the context of traditional reduced order modeling methods (ROMs), time and parameter extrapolation tasks remain a formidable challenge. To this end, we propose a hybrid projection/data-driven framework that leverages two subspaces to improve the prediction accuracy of traditional ROMs. We first obtain inaccurate mode coefficients from traditional ROMs in the reduced order subspace. Then, in the prior dimensionality reduced subspace, we correct the inaccurate mode coefficients and restore the discarded mode coefficients through neural network. Finally, we approximate the solutions with these mode coefficients in the prior dimensionality reduced subspace. To reduce the computational cost during the offline training stage, we propose a training data sampling strategy based on dynamic mode decomposition (DMD). The effectiveness of the proposed method is investigated with the parameterized Navier–Stokes equations in stream-vorticity formulation. In addition, two additional time extrapolation methods based on DMD are also proposed and compared.
Holistic characterization of an under-expanded high-enthalpy jet under uncertainty
Authors: Capriati M. , Turchi A. , Congedo P. M. , Magin T. E.
Published: June 2024

Elaborate methodologies have been developed to study the thermo-chemical response of materials in high-enthalpy flows. To reach the high magnitudes of heat flux encountered in some hypersonic applications, one can resort to supersonic jets. They involve several physical effects, such as detached shocks ahead of probes. Because of these features, characterizing supersonic flows is a challenging task, especially when one accounts for experimental and modeling uncertainties. Building on the development of stochastic approaches, we propose a holistic methodology to determine the quantities of interest in an optimal manner for an under-expanded high-enthalpy jet, using both experimental measurements and high-fidelity flow simulations. Given the high computational cost of the high-fidelity simulations needed to describe the flow, we built an adaptive/multi-fidelity surrogate model to replace the estimation of the costly computer solver. A Bayesian inference method then allowed for characterizing an experiment carried out in the von Karman Institute's Plasmatron facility, for which no robust methodology currently exists. We show that the reservoir pressure and temperature and the nitrogen catalytic recombination coefficient of the copper probes can be accurately determined from the available measurements. Contrarily, the test conditions do not allow us to estimate the oxygen catalytic recombination coefficient. Finally, the characterized uncertainties are propagated through the numerical solver, yielding an uncertainty-based high-fidelity representation of the hypersonic flow's structure variability.
Impacts of hot electron diffusion, electron–phonon coupling, and surface atoms on metal surface dynamics revealed by reflection ultrafast electron diffraction
Authors: He Xing , Ghosh Mithun , Yang Ding-Shyue
Published: June 2024

Metals exhibit nonequilibrium electron and lattice subsystems at transient times following femtosecond laser excitation. In the past four decades, various optical spectroscopy and time-resolved diffraction methods have been used to study electron–phonon coupling and the effects of underlying dynamical processes. Here, we take advantage of the surface specificity of reflection ultrafast electron diffraction (UED) to examine the structural dynamics of photoexcited metal surfaces, which are apparently slower in recovery than predicted by thermal diffusion from the profile of absorbed energy. Fast diffusion of hot electrons is found to critically reduce surface excitation and affect the temporal dependence of the increased atomic motions on not only the ultrashort but also sub-nanosecond times. Whereas the two-temperature model with the accepted physical constants of platinum can reproduce the observed surface lattice dynamics, gold is found to exhibit appreciably larger-than-expected dynamic vibrational amplitudes of surface atoms while keeping the commonly used electron–phonon coupling constant. Such surface behavioral difference at transient times can be understood in the context of the different strengths of binding to surface atoms for the two metals. In addition, with the quantitative agreements between diffraction and theoretical results, we provide convincing evidence that surface structural dynamics can be reliably obtained by reflection UED even in the presence of laser-induced transient electric fields.
Structural modeling of high-entropy oxides battery anodes using x-ray absorption spectroscopy
Authors: Marques Otavio J. , Segre Carlo U.
Published: June 2024

High-entropy oxides (HEOs) are single phase solid solutions where five or more metals share the same sublattice, giving rise to unexpected features in various fields of applications. Recently, HEOs have emerged as an alternative conversion electrode anode material for next-generation Li-ion batteries, where the combination of several different elements in a single solid solution can synergistically act to overcome some of its main drawbacks, improving performance. Due to their chemical complexity, x-ray absorption spectroscopy (XAS) emerges as an appropriate technique to study the electronic (x-ray absorption near edge structure, XANES) and local structure (extended x-ray absorption fine structure, EXAFS) of these compounds as a function of cycling. This work aims to highlight the capabilities of XAS as an element-specific probe to understand a material’s structure at the atomistic level through EXAFS modeling of (MgFeCoNiCuZn)O high-entropy system and how to extract valuable information about the bond distance, number of near neighbors, and local disorder, which are crucial to a full understanding of the electrochemical reaction mechanisms of such battery electrodes.
Depth resolution in piezoresponse force microscopy
Authors: Roeper Matthias , Seddon Samuel D. , Amber Zeeshan H. , Rüsing Michael , Eng Lukas M.
Published: June 2024

Piezoresponse force microscopy (PFM) is one of the most widespread methods for investigating and visualizing ferroelectric domain structures down to the nanometer length scale. PFM makes use of the direct coupling of the piezoelectric response to the crystal lattice, and hence, it is most often applied to spatially map the three-dimensional (3D) near-surface domain distribution of any polar or ferroic sample. Nonetheless, since most samples investigated by PFM are at least semiconducting or fully insulating, the electric ac field emerging from the conductive scanning force microscopy (SFM) tip penetrates the sample and, hence, may also couple to polar features that are deeply buried into the bulk of the sample under investigation. Thus, in the work presented here, we experimentally and theoretically explore the contrast and depth resolution capabilities of PFM, by analyzing the dependence of several key parameters. These key parameters include the depth of the buried feature, i.e., here a domain wall (DW), as well as PFM-relevant technical parameters such as the tip radius, the PFM drive voltage and frequency, and the signal-to-noise ratio. The theoretical predictions are experimentally verified using x-cut periodically poled lithium niobate single crystals that are specially prepared into wedge-shaped samples, in order to allow the buried feature, here the DW, to be “positioned” at any depth into the bulk. This inspection essentially contributes to the fundamental understanding in PFM contrast analysis and to the reconstruction of 3D domain structures down to a 1 μm-penetration depth into the sample.
Room temperature quantum emitters in aluminum nitride epilayers on silicon
Authors: Cannon Joseph K. , Bishop Sam G. , Eggleton Katie M. , Yağcı Huseyin B. , Clark Rachel N. , Ibrahim Sherif R. , Hadden John P. , Ghosh Saptarsi , Kappers Menno J. , Oliver Rachel A. , Bennett Anthony J.
Published: June 2024

Room temperature quantum emitters have been reported in aluminum nitride grown on sapphire, but until now they have not been observed in epilayers grown on silicon. We report that epitaxial aluminum nitride grown on silicon by either plasma vapor deposition or metal-organic vapor phase epitaxy contains point-like emitters in the red to near-infrared part of the spectrum. We study the photon statistics and polarization of emission at a wavelength of 700–750 nm, showing signatures of quantized electronic states under pulsed and CW optical excitation. The discovery of quantum emitters in a material deposited directly on silicon can drive integration using industry standard 300 mm wafers, established complementary metal-oxide-semiconductor control electronics, and low marginal-cost mass-manufacturing.
Fractal contours: Order, chaos, and art
Authors: McDonough John , Herczyński Andrzej
Published: June 2024

Over the recent decades, a variety of indices, such as the fractal dimension, Hurst exponent, or Betti numbers, have been used to characterize structural or topological properties of art via a singular parameter, which could then help to classify artworks. A single fractal dimension, in particular, has been commonly interpreted as characteristic of the entire image, such as an abstract painting, whether binary, gray-scale, or in color, and whether self-similar or not. There is now ample evidence, however, that fractal exponents obtained using the standard box-counting are strongly dependent on the details of the method adopted, and on fitting straight lines to the entire scaling plots, which are typically nonlinear. Here, we propose a more discriminating approach with the aim of obtaining robust scaling plots and extracting relevant information encoded in them without any fitting routines. To this goal, we carefully average over all possible grid locations at each scale, rendering scaling plots independent of any particular choice of grids and, crucially, of the orientation of images. We then calculate the derivatives of the scaling plots, so that an image is described by a continuous function, its fractal contour, rather than a single scaling exponent valid over a limited range of scales. We test this method on synthetic examples, ordered and random, then on images of algorithmically defined fractals, and finally, examine selected abstract paintings and prints by acknowledged masters of modern art.
Metal-support spin orders: Crucial effect on electrocatalytic oxygen reduction
Authors: Chen Yi-jie , Wen Jun , Luo Zhi-rui , Sun Fu-Li , Chen Wen-xian , Zhuang Gui-lin
Published: June 2024

Magnetic property (e.g. spin order) of support is of great importance in the rational design of heterogeneous catalysts. Herein, we have taken the Ni-supported ferromagnetic (FM) CrBr3 support (Nix/CrBr3) to thoroughly investigate the effect of spin-order on electrocatalytic oxygen reduction reaction (ORR) via spin-polarized density functional theory calculations. Specifically, Ni loading induces anti-FM coupling in Ni–Cr, leading to a transition from FM-to-ferrimagnetic (FIM) properties, while Ni–Ni metallic bonds create a robust FM direct exchange, benefiting the improvement of the phase transition temperature. Interestingly, with the increase in Ni loading, the easy magnetic axis changes from out-of-plane (2D-Heisenberg) to in-plane (2D-XY). The adsorption properties of Nix/CrBr3, involving O2 adsorption energy and configuration, are not governed by the d-band center but strongly correlate with magnetic anisotropy. It is noteworthy that the applied potential and electrolyte acidity triggers spin-order transition phenomena during the ORR and induces the catalytic pathway change from 4e− ORR to 2e− ORR with the excellent onset potential of 0.93 V/reversible hydrogen electrode, comparable to the existing most excellent noble-metal catalysts. Generally, these findings offer new avenues to understand and design heterogeneous catalysts with magnetic support.
How does an emulsion drop's viscosity influence its impact on various meshes?
Authors: Dutta Somen Kumar , Mandal Deepak Kumar
Published: June 2024

The impact of emulsion drops on a mesh is studied. These drops find applications in various fields, e.g., agricultural sprays, where the drop passes through a mesh for atomization. Both penetration (full or partial) and lateral spreading are observed in most cases. The maximum spread's variation with Weber number (We) shows liquid independence for drops impacting a given mesh. The variations can be concluded into one. However, when both lateral spread and penetration are concerned, the emulsion drop with the highest water content tested stands out as different. It shows dissimilar characteristics due to its higher viscosity. The drop's lateral spread Reynolds number is lower than the others, indicating a significant dependence on the liquid viscosity. Rising viscosity resists the lateral inertia. Surface tension (ST) and density do not have much influence. The balance between the downward and after-impact lateral inertia and their resistance makes the lateral spread on a given mesh independent of liquid. Three regimes, full, partial, and no penetration, can be defined. A dissimilarity in the after-penetration jet length is detected. The length is inversely proportional to the emulsion's rising water content. The drop with the highest viscosity, together with ST, provides the highest resistance to penetration. Thus, the length reduces abruptly. When the after-impact penetration cone angle is studied, the average angle reduces with We for the highest viscosity emulsions. An abrupt rise in resistance is detected. The study's novelty lies in bringing out the viscosity's influence on the emulsion drop's impact on a mesh.
Intercalation of quaternary ammonium cations as a key factor of electron storage in MoS2 thin films
Authors: Chen Bo-An , Kipkorir Anthony , Ptasinska Sylwia , Kamat Prashant V.
Published: June 2024

Electrochemical intercalation of cations within two-dimensional transition metal dichalcogenides presents a promising route for tailoring their optoelectronic properties. We have now succeeded in modulating the optical properties of MoS2 thin films through electrochemical intercalation of quaternary ammonium cations. The spectroelectrochemical experiments conducted with varying sizes of the intercalant revealed the size-dependent stability of the intercalated MoS2 nanosheets. The observed absorption change of the exciton bands is reversible and arises from the storage of electrons in MoS2 nanosheets and the subsequent weakening of interlayer van der Waals interactions following cation intercalation. This structural change is evidenced by the emergence of A*1g out-of-plane Raman mode. Additionally, the photoelectron spectroscopy reveals the emergence of a lower binding energy component of Mo 3d and the shift in Fermi level to higher energies, confirming the presence of stored electrons in cation intercalated-MoS2. The underlying mechanism of intercalation-induced property modifications in MoS2 discussed in the present study is useful in developing strategies for energy conversion devices.
Wake-induced vibration suppression for a circular cylinder using a pair of jets
Authors: Zhang Baoshou , Long Teng , Wang Ziyu , Wang Wei , Li Boyang , Shi Renhe
Published: June 2024

The wake-induced vibration (WIV) presents significant challenges to the structural integrity of multi-cylinder configurations. To effectively alleviate this problem, a numerical simulation is conducted to assess the effect of an active control technique that uses two jets located at the shoulder region of a cylinder to suppress WIV in two-degree-of-freedom. The equations of motion for the WIV response are solved using the Newmark-β method. The Newmark-β method is employed to solve the equations of motion governing the WIV response. Three kinds of angular position (β) on WIV suppression are investigated in detail, including 30°, 60°, and 90°. The angular position β is defined as the angle between the injection angle and the horizontal line. When the angular position (β) is 30°, the maximum cross-flow amplitude ratio (CFAR) is reduced from 0.9 (uncontrolled) to 0.5 (β = 30°), a reduction of approximately 44%. On the contrary, the maximum CFARs remain approximately 1.0 for the case 3 (β = 60°) and case 4 (β = 90°). Especially for the case 4, the cylinder showed the galloping response after the upper branch region. Since the jets are positioned on the vibration cylinder shoulders, the vortexes caused by the jets are opposite to the main vortexes induced by the cylinder. As a consequence, the jets shred the main vortexes in the wake of the cylinder, which leads to the driving force of the vibration reduction. Therefore, the cylinder's WIV amplitude is significantly suppressed.
Large-scale data generation for quantum cascade laser active-region design with automated wavefunction identification
Authors: Hu Y. , Suri S. , Kirch J. , Knipfer B. , Jacobs S. , Nair S. K. , Zhou Z. , Yu Z. , Botez D. , Mawst L. J.
Published: June 2024

We introduce an automated wavefunction-identification program to generate large-scale datasets for active-region (AR) design of quantum cascade lasers (QCLs) by using machine learning. Conventional QCL design methods rely on expert knowledge and extensive iterative testing; thus, they are inefficient AR design approaches. Our automated approach identifies crucial wavefunctions within a QCL band diagram rapidly and with high accuracy. Key wavefunctions in the optical-transition, injector-, and extractor-regions, which include, upper- and lower-laser levels, injecting levels, extractor levels, and high-energy leakage-path levels, are identified by using a refined k-means clustering algorithm and tailored probability formulas. We find that an accuracy of >95% can be achieved using this identification program. Leveraging our automated wavefunction identification program, we generated approximately 430 000 QCL structures, identified wavefunctions, and computed basic metrics such as energy differences between various levels. A nominally 8 μm-emitting QCL structure, with each stage comprising 24 layers and a fixed applied electric field of 40 kV/cm, which is expected to be close to that corresponding to the laser threshold, was used in the analysis. The compositions of InGaAs wells and AlInAs barriers were lattice-matched to InP, and only layer thicknesses were varied within empirically derived ranges. Using this dataset, we trained neural networks to map QCL structures to energy level differences and tested the performance. The promising results, with a coefficient of determination, R2, values around 90%, validate both the efficacy of our automated program for generating substantial, usable training data and the capability of our network for QCL-AR design.
Separation of terahertz and DC conductivity transitions in epitaxial vanadium dioxide films
Authors: Lu Chang , Gao Min , Liu Junxiao , Lu Yantong , Wen Tianlong , Lin Yuan
Published: June 2024

Terahertz (THz) light, probing electronic responses near the Fermi level, is closely linked to DC transport. In this study, we investigate the in situ THz and DC conductivity of epitaxial VO2 films near the heating-induced insulator–metal transition. We find that the THz conductivity transition occurs at lower temperatures than the DC conductivity transition, with the separation increasing with film thickness and crystallization quality. Analysis of the complex conductivity spectra attributes this separation to released carrier confinement at THz frequencies. Our findings contribute to a deeper understanding of electron dynamics in VO2 films.
Achieving semi-metallic conduction in Al-rich AlGaN: Evidence of Mott transition
Authors: Mondal Shubham , Kezer Pat , Wang Ding , Tanim Md Mehedi Hasan , Heron John T. , Mi Zetian
Published: June 2024

The development of high performance wide-bandgap AlGaN channel transistors with high current densities and reduced Ohmic losses necessitates extremely highly doped, high Al content AlGaN epilayers for regrown source/drain contact regions. In this work, we demonstrate the achievement of semi-metallic conductivity in silicon (Si) doped N-polar Al0.6Ga0.4N grown on C-face 4H-SiC substrates by molecular beam epitaxy. Under optimized conditions, the AlGaN epilayer shows smooth surface morphology and a narrow photoluminescence spectral linewidth, without the presence of any secondary peaks. A favorable growth window is identified wherein the free electron concentration reaches as high as ∼1.8 × 1020 cm−3 as obtained from Hall measurements, with a high mobility of 34 cm2/V·s, leading to a room temperature resistivity of only 1 mΩ·cm. Temperature-dependent Hall measurements show that the electron concentration, mobility, and sheet resistance do not depend on temperature, clearly indicating dopant Mott transition to a semi-metallic state, wherein the activation energy (Ea) falls to 0 meV at this high value of Si doping for the AlGaN films. This achievement of semi-metallic conductivity in Si doped N-polar high Al content AlGaN is instrumental for advancing ultrawide bandgap electronic and optoelectronic devices.
A DFT/MRCI Hamiltonian parameterized using only ab initio data: I. valence excited states
Authors: Costain Teagan Shane , Ogden Victoria , Neville Simon P. , Schuurman Michael S.
Published: June 2024

A new combined density functional theory and multi-reference configuration interaction (DFT/MRCI) Hamiltonian parameterized solely using the benchmark ab initio vertical excitation energies obtained from the QUEST databases is presented. This new formulation differs from all previous versions of the method in that the choice of the underlying exchange–correlation (XC) functional employed to construct the one-particle (orbital) basis is considered, and a new XC functional, QTP17, is chosen for its ability to generate a balanced description of core and valence vertical excitation energies. The ability of the new DFT/MRCI Hamiltonian, termed QE8, to furnish accurate excitation energies is confirmed using benchmark quantum chemistry computations, and a mean absolute error of 0.16 eV is determined for the wide range of electronic excitations included in the validation dataset. In particular, the QE8 Hamiltonian dramatically improves the performance of DFT/MRCI for doubly excited states. The performance of fast approximate DFT/MRCI methods, p-DFT/MRCI and DFT/MRCI(2), is also evaluated using the QE8 Hamiltonian, and they are found to yield excitation energies in quantitative agreement with the parent DFT/MRCI method, with the two methods exhibiting a mean difference of 0.01 eV with respect to DFT/MRCI over the entire benchmark set.
Localized wave structures: Solitons and beyond
Authors: Ostrovsky L. , Pelinovsky E. , Shrira V. , Stepanyants Y.
Published: June 2024

The review is concerned with solitary waves and other localized structures in the systems described by a variety of generalizations of the Korteweg–de Vries (KdV) equation. Among the topics we focus upon are “radiating solitons,” the generic structures made of soliton-like pulses, and oscillating tails. We also review the properties of solitary waves in the generalized KdV equations with the modular and “sublinear” nonlinearities. Such equations have an interesting class of solutions, called compactons, solitary waves defined on a finite spatial interval. Both the properties of single solitons and the interactions between them are discussed. We show that even minor non-elastic effects in the soliton–soliton collisions can accumulate and result in a qualitatively different asymptotic behavior. A statistical description of soliton ensembles (“soliton gas”), which emerges as a major theme, has been discussed for several models. We briefly outline the recent progress in studies of ring solitons and lumps within the framework of the cylindrical KdV equation and its two-dimensional extension. Ring solitons and lumps (2D solitons) are of particular interest since they have many features in common with classical solitons and yet are qualitatively different. Particular attention is paid to interactions between the objects of different geometries, such as the interaction of ring solitons and shear flows, ring solitons and lumps, and lumps and line solitons. We conclude our review with views of the future developments of the selected lines of studies of localized wave structures in the theory of weakly nonlinear, weakly dispersive waves.