bluuebunny/crossref_metadata_2025 huggingface dataset:
Decoration on Cubane with an Awareness of Chirality: Development of Substituted Cubane Syntheses
Authors: Matsubara Seijiro , Takebe Hiyori
Published: July 2023

Nearly 60 years have passed since Professor Eaton’s practical synthesis of cubane, and research using it as a unique molecular scaffold has since gained momentum. Since the early synthesis of polynitrocubane, it has been shown that up to eight substituents can be covalently assembled into a confined space. The arrangement of substituents on cubane has paved the way for the creation of unique asymmetric molecules. To put it another way, chirality is manifested by selectively introducing three or more diverse types of substituents at specific sites. Recently, there has also been a report on the synthesis of perfluorocubane, a molecule with intriguing electronic properties.

1 Introduction

2 General Information

3 Functionalization of Cubane

4 Preparation of Polysubstituted Cubanes

5 Conclusion
Palladium-Catalyzed Homo-Dimerization of Terminal Alkynes
Authors: Zhou Xiao-Yu , Bao Ming , Chen Xia , Guo Hong-Yu
Published: July 2023

The palladium-catalyzed homo-dimerization of terminal alkynes is a powerful and atom-economic method for the preparation of highly unsaturated four-carbon skeletons, which are key structural units found in natural and/or biologically active products and materials. However, during the homo-dimerization of terminal alkynes, a major issue is control of the chemo-, regio-, and stereoselectivity. Thus, over the past few decades, various strategies and methods have been developed that employ palladium catalytic systems for such homo-dimerizations. In this Short Review, we highlight important methods for the selective synthesis of these valuable four-carbon compounds, including conjugated 1,3-enynes, 1,3-diynes, and 1,3-dienes.

1 Introduction

2 Redox-Neutral Homo-Dimerization of Terminal Alkynes for the Synthesis of 1,3-Enynes

2.1 Head-to-Head Dimerization

2.2 Head-to-Tail Dimerization

3 Oxidative Homo-Dimerization of Terminal Alkynes for the Synthesis of 1,3-Diynes

3.1 Unsupported Palladium Catalysts

3.1.1 Choice of Oxidant

3.1.2 Choice of Ligand

3.1.3 Choice of Solvent

3.2 Supported Palladium Catalysts

4 Reductive Homo-Dimerization of Terminal Alkynes for the Synthesis of 1,3-Dienes

5 Conclusion
Metal-Loaded Semiconductor-Photocatalysis of Alcohols for Selective Organic Synthesis: A Personal Account
Authors: Mori Shogo , Naka Hiroshi , Saito Susumu , Sakurai Shu
Published: July 2023

In this account, we review our research over the last decade on metal-loaded semiconductor-photocatalyzed organic transformations using alcohols. Different from many reactions using alcohols as mere sacrificial electron donors, our study has demonstrated alcohols as useful organic building blocks incorporated into value-added products. Besides such recollections of previous results, we briefly introduce our ongoing project involving photocatalytic C–C bond-forming reactions via the C–C bond scission of tertiary alcohols.

1 Introduction

2 Dehydroxylative Hydrogenolysis of Allylic Alcohols

3 Acceptorless Dehydrogenation of Activated/Unactivated Alcohols

4 N-Alkylation of Amines using Alcohols as Alkylating Agents

5 Summary and Outlook
Study on Integrated Synthesis of Dimeric Pyranonaphthoquinones: Preparation of Versatile Synthetic Intermediate and Conversion into ent-Hemi-actinorhodin and ent-Hemi-γ-actinorhodin
Authors: Ando Yoshio , Suzuki Keisuke , Maturi Mark M. , Hoshino Taiju , Tanaka Nozomi , Sakai Takahiro , Ohmori Ken
Published: July 2023

For developing general synthetic access toward dimeric pyranonaphthoquinones including β-naphthocyclinone, actinorhodin, and γ-actinorhodin, we report stereodefined 6,9,10-trioxypyranonaphthalene as a versatile intermediate. Its robust preparation started from ethyl (S)-4-chloro-3-hydroxybutyrate. The pyranonaphthalene core was constructed by a Michael–Dieckmann sequence, and methylation using Me3Al and BF3·OEt2 established the required trans structure in a scalable manner. Conversion of this intermediate into ent-hemi-actinorhodin and into ent-hemi-γ-actinorhodin are also reported, in which the conditions for the oxidative lactonization were optimized.
Effectiveness of Neurofunctional Physical Therapy on the Quality of Sleep of Individuals with Parkinson's Disease: Case Series
Authors: Souza Rogério José de , Shigaki Isabela Andrelino de Almeida , Terra Marcelle Brandão , Barboza Natália Mariano , Bueno Maria Eduarda Brandão , Mesas Arthur Eumann , Smaili Suhaila Mahmoud
Published: July 2023

Objective Sleep disorders are disabling and highly prevalent comorbidities in Parkinson's disease (PD). This study's objective was to verify the effectiveness of neurofunctional physiotherapy in sleep quality, objectively and subjectively assessing it among individuals with PD.

Methods A sample of individuals with PD was assessed before and after 32 physiotherapy sessions and three months later (follow-up). The following instruments were used: Pittsburgh Sleep Quality Index (PSQI); Epworth Sleepiness Scale (ESS); Parkinson's Disease Sleep Scale (PDSS), and actigraphy.

Results Nineteen individuals aged 67.37 years old ( ±  8.03) on average were included. No differences were found in any of the variables measured by the actigraphy or the ESS. Improvement was found from pre- to post-intervention in terms of nocturnal movements (p = 0.04; d = 0.46) and total score (p = 0.03; d = 0.53) obtained on the PDSS. Improvement was also found in the PDSS sleep onset/maintenance domain (p = 0.001; d = 0.75) between pre-intervention and follow-up. The participants' total score obtained in the PSQI improved from pre- to post-intervention (p = 0.03; d = 0.44). Significant differences were found in nighttime sleep (p = 0.02; d = 0.51) and nocturnal movements (p = 0.02; d = 0.55), and in the PDSS total score (p = 0.04; d = 0.63) between pre- and post-intervention when only the poor sleepers subgroup (n = 13) was considered, while improvements were found in sleep onset/maintenance (p = 0.003; d = 0.91) between pre-intervention and follow-up.

Discussion Neurofunctional physiotherapy was ineffective in improving objective parameters of sleep but was effective in improving the perception of sleep quality subjectively assessed among individuals with PD, especially those who perceived themselves to be poor sleepers.
How to Identify Advanced Nonalcoholic Fatty Liver Disease in the Primary Care Setting
Authors: Golabi Pegah , Shah Dipam , Younossi Zobair M.
Published: July 2023

Nonalcoholic fatty liver disease (NAFLD) affects 30 to 40% of the population globally and is increasingly considered the most common liver disease. Patients with type 2 diabetes, obesity, and cardiovascular diseases are at especially increased risk for NAFLD. Although most patients with NAFLD do not have progressive liver disease, some patients progress to cirrhosis, liver cancer, and liver mortality. Given the sheer number of patients with NAFLD, the burden of disease is enormous. Despite this large and increasing burden, identification of NAFLD patients at risk for progressive liver disease in the primary care and diabetology practice settings remains highly suboptimal. In this review, our aim is to summarize a stepwise approach to risk stratify patients with NAFLD which should help practitioners in their management of patients with NAFLD.
Investigating the factors affecting ICT integration of in-service teachers in Henan Province, China: structural equation modeling
Authors: Peng Ran , Razak Rafiza Abdul , Halili Siti Hajar
Published: July 2023

The integration of Information and Communication Technology (ICT) can significantly improve teaching and learning outcomes, but various factors determine the degree to which ICT is integrated into educational practices. This study used quantitative methodology to examine four key factors that impact in-service teachers’ ICT integration and how they interact with each other. Data was collected through snowball sampling from 685 in-service teachers in Henan Province, China. Using partial least squares structural equation modeling (PLS-SEM), the study analyzed four factors from the Technology Acceptance Model 3 (TAM 3) and the Will-Skill-Tool model (WST model): attitudes (AT), self-efficacy (SE), digital competence (DC), and digital tools utilization (DTU). The findings revealed that all four elements exerted a noteworthy influence on the integration of ICT by in-service instructors. Meanwhile, attitudes, digital competence, and digital tools utilization have a mediating effect in this research. Additionally, the study examined how gender, age, and teaching experience influence these factors and ICT integration. The findings revealed that females exhibit higher levels of positive attitudes and digital competence than males, while teachers aged 31–35 years have stronger digital abilities, digital tool use, and ICT integration compared to younger or older teachers. Furthermore, teachers with less than three years of teaching experience exhibit significantly stronger attitudes, self-efficacy, digital competence, and ICT integration than those with more than ten years of experience. The implication of the study provides valuable insights for designing effective ICT-based instruction and developing teacher education and educational technology programs aimed at promoting ICT integration in the classroom.
Limit stationary measures of the stochastic magnetohydrodynamic system in a 3D thin domain
Authors: Zhong Wenhu , Chen Guanggan , Zhang Yuanyuan
Published: July 2023

This work is concerned with a stochastic magnetohydrodynamic (MHD) system in a 3D thin domain. Although the individual solution may be chaotic in fluid dynamics, the stationary measure is essential to capture complex dynamical behaviors in the view of statistics. We first borrow the α-approximation model to derive the stationary measure of the 3D stochastic MHD system. Then, we further prove that the stationary measure of the system converges weakly to the counterpart of the corresponding 2D stochastic MHD system as the thickness of the thin domain tends to zero.
Effects of high energy electrons on electron temperature measurements of asymmetric double Langmuir probes
Authors: Jin Chenyao , Yip Chi-Shung , Jiang Di , Zhang Wei , Xu Guo-Sheng
Published: July 2023

In this work, electron temperature was measured with both the asymmetric double Langmuir probe (ADLP) and the single Langmuir probe to investigate the reliability of the ADLP on the electron temperature measurement in multi-temperature Maxwellian plasmas. A series of I–V traces of the ADLP were obtained at various plasma conditions with different area ratios and analyzed with different methods including conventional ADLP analysis and two-temperature Maxwellian fitting with results measured by a single planar Langmuir probe analyzed with three-temperature Maxwellian fitting as reference. The measured Te of the ADLP is found to reflect that of the temperature of the degraded primary electrons when the area ratio of the probe tips is close to ∼16 and approaches the real effective electron temperature as the area ratio increases to a value of ∼30% higher than that measured by a single Langmuir probe, which occurs even when the area ratio is higher than the flux ratio of electrons and ions entering their respective sheaths. This effect is consistent with the distortion effect of Langmuir probe I–V traces caused by the presence of hotter electron species, which was computationally reconstructed and agreed well with the experimental observations. This result implies that an area ratio, possibly ∼20 times much larger than what was conventionally assumed, is needed for an ADLP to be reliably treated as a single Langmuir probe in practical settings, where electron energy distribution functions of plasmas are generally expected to be multi-temperature Maxwellian. This effect is also analogous to the current balance between a single Langmuir probe and the device wall, implying that this effect would also affect the application of the single Langmuir probe in plasmas, where the ion loss to the device wall can be reduced, such as plasmas in miniaturized devices, strong magnetic fields, or a highly ion-neutral collisional environment.
Ultra-generalized Wannier bases: Are they relevant to topological transport?
Authors: Moscolari Massimo , Panati Gianluca
Published: July 2023

We generalize Prodan’s construction of radially localized generalized Wannier bases [E. Prodan, J. Math. Phys. 56(11), 113511 (2015)] to gapped quantum systems without time-reversal symmetry, including, in particular, magnetic Schrödinger operators, and we prove some basic properties of such bases. We investigate whether this notion might be relevant to topological transport by considering the explicitly solvable case of the Landau operator.
Non-classical nucleation of ordered L12 precipitates in the FCC based Al0.25CoFeNi high entropy alloy
Authors: Dasari Sriswaroop , Sharma Abhishek , Gorsse Stéphane , Chesetti Advika , Banerjee Rajarshi
Published: July 2023

The complex interplay between competing phase stabilities of FCC, L12, BCC, and B2 phases in the Al0.25CoFeNi (7Al-31Co-31Fe-31Ni in at. %) high entropy alloy (HEA) leads to non-classical phase transformation pathways and resultant novel microstructures. Specifically, the competition between the homogenous precipitation of L12 and heterogenous precipitation of BCC/B2 can be studied at a temperature of 500 °C in the Al0.25CoFeNi alloy. Upon isothermally annealing the single FCC phase microstructure of this HEA at 500 °C up to 50 h, the transformation initiates with the formation of a transient ordered L12 phase with minor Ni–Al enrichment, which is far-from equilibrium, as revealed by atom probe tomography, and can be considered non-classical nucleation. The near equilibrium L12 phase eventually replaces the transient L12 during continued annealing at the same temperature. However, the resultant FCC + L12 microstructure is metastable because the true equilibrium for the Al0.25CoFeNi alloy at 500 °C is a mixture of L12 + B2 phases, as revealed by solution thermodynamics modeling. The higher nucleation barrier for the BCC-based ordered B2 phase coupled with the slower kinetics at 500 °C leads to the homogeneous precipitation of L12, while the B2 phase appears to sluggishly grow from grain boundaries acting as heterogeneous nucleation sites.
Stochastic reaction–diffusion system modeling predator–prey interactions with prey-taxis and noises
Authors: Bendahmane M. , Nzeti H. , Tagoudjeu J. , Zagour M.
Published: July 2023

In this paper, we are concerned with a new stochastic system of nonlinear partial differential equations modeling the Lotka–Volterra interactions of predators and preys in the presence of prey-taxis, spatial diffusion, and noises. The spatial and temporal variations of the predator’s velocity are determined by the prey gradient. In the first part, we derive a macroscopic model from stochastic kinetic equations by using the micro–macro decomposition method. In the second part, we sketch the proof of the existence of weak martingale solutions by using a Faedo–Galerkin method. In the last part, we develop a one- and two-dimensional finite volume approximation for the stochastic kinetic and macroscopic models, respectively. Our one-dimensional space numerical scheme is uniformly stable along the transition from kinetic to macroscopic regimes. We close with various numerical tests illustrating the convergence of our numerical method and some features of our stochastic macro-scale system.
Early detection of thermoacoustic instability in a staged single-sector combustor for aircraft engines using symbolic dynamics-based approach
Authors: Baba Kento , Kishiya Sena , Gotoda Hiroshi , Shoji Takeshi , Yoshida Seiji
Published: July 2023

We experimentally conduct an early detection of thermoacoustic instability in a staged single-sector combustor using a novel methodology that combines symbolic dynamics and machine learning. We propose two invariants in this study: the determinisms of the joint symbolic recurrence plots DJ and the ordinal transition pattern-based recurrence plots DT. These invariants enable us to capture the phase synchronization between acoustic pressure and heat release rate fluctuations associated with a precursor of thermoacoustic instability. The latent space consisting of DJ and DT, which is obtained by a support vector machine in combination with the k-means clustering method, can appropriately determine a transitional regime between stable combustion and thermoacoustic instability.
Topological edge state-induced enhancement of photonic spin Hall effect in a heterostructure with monolayer graphene
Authors: Qi Song , Da Haixia , Yan Xiaohong
Published: July 2023

Photonic spin Hall effect (PSHE) of the transmitted wave presents promising applications in photonic spintronic devices, including inter-chip optical circuitry and quantum computing devices. These applications can benefit from phenomena such as the photon tunneling effect, frustrated total internal reflection, and the resonant optical tunneling effect. However, the mechanisms for enhancing PSHE of the transmitted wave are limited. In this study, an alternative strategy is proposed, which involves the utilization of topological edge states to enhance PSHE without relying on the aforementioned means. To demonstrate this effect, a heterostructure is designed, comprising two one-dimensional photonic crystals (PhCs) and a monolayer graphene. By leveraging the topological edge state, a significant enhancement of PSHE in the transmitted wave is observed, surpassing several times the incident wavelength. Furthermore, it is shown that the enhanced PSHE can be controlled and fine-tuned by adjusting the Fermi energy of monolayer graphene and the repetition numbers of the two PhCs. The enhanced and controlled PSHE in this heterostructure introduces possibilities for the development of novel optical components, such as switches, filters, modulators, and sensors.
Effect of network nestedness on stability, diversity, and resilience of ecosystems
Authors: Duan Dongli , Zhai Yuchen , Hou Gege , Zhou Meng , Rong Yisheng
Published: July 2023

The structural nestedness has important effects on the ecosystem’s robustness, stability, and species diversity, but quantitative analysis tools are still lacking at present. According to the competitive and mutually beneficial interactions among ecosystems species, we designed a quantitative analysis tool of nestedness on ecosystems metrics by mapping the ecosystems into symbolic networks and calculating the network’s competitive nestedness and mutualistic nestedness with an overlap metric, respectively. The results of the real system and network models show that in the competitive and mutualistic coupling network, the competitive nestedness reduces the biodiversity and robustness of the network, but the mutualistic nestedness has the opposite effect. Moreover, the larger the competitive nestedness in the pure structural case, the more unstable the ecological network tends to be. However, once the dynamical governing mechanism is considered, the competitive nestedness would make the system more stable. Our work enables us to understand more specifically the effects of the network structure on ecosystems and helps reveal the mechanism that how nestedness can be changed to increase network stability, species diversity, and robustness.
Improved frequency comb operation of an InAs/GaAs hybrid multisection quantum dot laser on silicon
Authors: Renaud T. , Huang H. , Kurczveil G. , Liang D. , Beausoleil R. G. , Grillot F.
Published: July 2023

This work reports on a systematic investigation of the frequency comb enhancement in hybrid InAs/GaAs multisection quantum dot lasers on silicon. The colliding configuration provides an operating frequency at twice the fundamental frequency of the free-spectral range of the cold cavity. In particular, the contribution of the linewidth enhancement factor, or αH-factor, on the comb formation is investigated with respect to the reverse voltage and temperature conditions. When those parameters are varied, the formation of the combs is found to increase with respect to αH. In addition, we also demonstrate that this quantum dot laser exhibits a comb behavior, while the beatnote locking is not fully achieved. This effect is essentially due to the dispersion which is not fully compensated from the optical nonlinearities. These results bring further insights on comb and pulse formations in multisection quantum dot lasers, which is important for designing future light sources for on-chip and chip-to-chip optical interconnects.
Kinetic study of ion acoustic waves in Venusian ionosphere
Authors: Kamalam T. , Singh S. V. , Sreeraj T. , Lakhina G. S.
Published: July 2023

Kinetic dispersion of the ion acoustic waves has been explored for an unmagnetized five component plasma system comprising of Venusian protons, Venusian oxygen ions, Venusian electrons, solar wind protons, and kappa electrons. The solar wind protons and electrons are assumed to be streaming along the ambient magnetic field. The plasma parameters for this study have been obtained from Lundin et al. [Icarus 215(2), 751–758 (2011)] for the dawn dusk meridian of Venus Express with the data from the ASPERA-4 ion mass analyzer. Our analysis revealed that two modes, viz., ion acoustic mode and beam driven mode, are excited for the considered plasma parameters. The ion acoustic mode exists due to the Venusian ions, and its growth rate is influenced by the solar wind beam electrons. The beam driven mode's existence and its growth rate depend on the solar wind beam protons. We conjecture that the ion acoustic mode and the beam driven mode could be useful in explaining the electrostatic noise in the Venusian ionosphere in the range of several hundreds Hz to 1 kHz and several tens kHz, respectively.
Similarities and differences in the fermiology of kagome metals AV3Sb5 (A = K, Rb, Cs) revealed by Shubnikov–de Haas oscillations
Authors: Wang Zheyu , Zhang Wei , Wang Lingfei , Poon Tsz Fung , Tsang Chun Wai , Wang Wenyan , Xie Jianyu , Lam Siu Tung , Zhou Xuefeng , Zhao Yusheng , Wang Shanmin , Ai Ming-Zhong , Lai Kwing To , Goh Swee K.
Published: July 2023

Materials with AV3Sb5 (A = K, Rb, Cs) stoichiometry are recently discovered kagome superconductors with the electronic structure featuring a Dirac band, van Hove singularities, and flat bands. These systems undergo anomalous charge-density-wave transitions at TCDW∼80–100 K, resulting in the reconstruction of the Fermi surface from the pristine phase. Although comprehensive investigations of the electronic structure via quantum oscillations (QOs) have been performed on the sister compounds CsV3Sb5 and RbV3Sb5, a detailed QO study of KV3Sb5 is so far absent. Here, we report the Shubnikov–de Haas QO study in KV3Sb5. We resolve a large number of new frequencies with the highest frequency of 2202 T (occupying ∼54% of the Brillouin zone area in the kx–ky plane). The Lifshitz-Kosevich analysis further gives relatively small cyclotron effective masses, and the angular dependence study reveals the two-dimensional nature of the frequencies with a sufficient signal-to-noise ratio. Finally, we compare the QO spectra for all three AV3Sb5 compounds collected under the same conditions, enabling us to point out the similarities and the differences across these systems. Our results fill in the gap of the QO study in KV3Sb5 and provide valuable data to understand the band structure of all three members of AV3Sb5.
Grass-like alumina enhances transmittance and electrical conductivity of atomic layer deposited Al-doped ZnO for thermoelectric and TCO applications
Authors: Koskinen T. , Raju R. , Tittonen I. , Kauppinen C.
Published: July 2023

Transparent thermoelectric materials enable the integration of sensing and energy harvesting devices on various surfaces such as windows and user interfaces. A key constraint for device performance in such applications is the available surface area from which the thermoelectric power should be harvested without compromising the optical properties. Here, we demonstrate atomic layer deposition (ALD) of aluminum doped zinc oxide (AZO), the most prominent n-type thermoelectric material, on grass-like alumina (GLA), a high-performance, low-cost antireflective coating. The conformal nature of the ALD process enables the AZO growth to closely follow the topography of the underlying GLA film, therefore providing an increased effective surface area compared to a reference AZO film grown directly on plain glass. The films grown on GLA show an improved electrical conductivity attributed to additional doping by the GLA. The effect is pronounced at lower AZO thicknesses, resulting in a 228% increase in the electrical conductivity and an 80% increase in the thermoelectric power factor of 32 nm thick films. Moreover, the GLA-AZO films partly inherit the antireflective behavior of the GLA film, thus showing improved optical transparency compared to the reference AZO film on glass. Our results promote transparent thermoelectric devices with improved transparency and thermoelectric performance.
Role of coupling delay in oscillatory activity in autonomous networks of excitable neurons with dissipation
Authors: Bukh A. V. , Shepelev I. A. , Elizarov E. M. , Muni S. S. , Schöll E. , Strelkova G. I.
Published: July 2023

We study numerically effects of time delay in networks of delay-coupled excitable FitzHugh–Nagumo systems with dissipation. Generation of periodic self-sustained oscillations and its threshold are analyzed depending on the dissipation of a single neuron, the delay time, and random initial conditions. The peculiarities of spatiotemporal dynamics of time-delayed bidirectional ring-structured FitzHugh–Nagumo neuronal systems are investigated in cases of local and nonlocal coupling topology between the nodes, and a first-order nonequilibrium phase transition to synchrony is established. It is shown that the emergence of an oscillatory activity in delay-coupled FitzHugh–Nagumo neurons is observed for smaller values of the coupling strength as the dissipation parameter decreases. This can provide the possibility of controlling the spatiotemporal behavior of the considered neuronal networks. The observed effects are quantified by plotting distributions of the maximal Lyapunov exponent and the global order parameter in terms of delay and coupling strength.
Simulation study of the effects of polymer network dynamics and mesh confinement on the diffusion and structural relaxation of penetrants
Authors: Lin Tsai-Wei , Mei Baicheng , Schweizer Kenneth S. , Sing Charles E.
Published: July 2023

The diffusion of small molecular penetrants through polymeric materials represents an important fundamental problem, relevant to the design of materials for applications such as coatings and membranes. Polymer networks hold promise in these applications because dramatic differences in molecular diffusion can result from subtle changes in the network structure. In this paper, we use molecular simulation to understand the role that cross-linked network polymers have in governing the molecular motion of penetrants. By considering the local, activated alpha relaxation time of the penetrant and its long-time diffusive dynamics, we can determine the relative importance of activated glassy dynamics on penetrants at the segmental scale vs entropic mesh confinement on penetrant diffusion. We vary several parameters, such as the cross-linking density, temperature, and penetrant size, to show that cross-links primarily affect molecular diffusion through the modification of the matrix glass transition, with local penetrant hopping at least partially coupled to the segmental relaxation of the polymer network. This coupling is very sensitive to the local activated segmental dynamics of the surrounding matrix, and we also show that penetrant transport is affected by dynamic heterogeneity at low temperatures. To contrast, only at high temperatures and for large penetrants or when the dynamic heterogeneity effect is weak, does the effect of mesh confinement become significant, even though penetrant diffusion more broadly empirically follows similar trends as established models of mesh confinement-based transport.
Extraordinary permittivity characterization of 4H SiC at millimeter-wave frequencies
Authors: Li Lei , Reyes Steve , Asadi Mohammad Javad , Fay Patrick , Hwang James C. M.
Published: July 2023

For millimeter-wave power applications, GaN high-electron mobility transistors (HEMTs) are often grown epitaxially on a high-purity semi-insulating c-axis 4H-SiC substrate. For these anisotropic hexagonal materials, the design and modeling of microstrip and coplanar interconnects require detailed knowledge of both the ordinary permittivity ε⊥ and the extraordinary permittivity εǁ perpendicular and parallel, respectively, to the c-axis. However, conventional dielectric characterization techniques make it difficult to measure εǁ alone or to separate εǁ from ε⊥. As a result, there is little data for εǁ, especially at millimeter-wave frequencies. This work demonstrates techniques for characterizing εǁ of 4H SiC using substrate-integrated waveguides (SIWs) or SIW resonators. The measured εǁ on seven SIWs and eleven resonators from 110 to 170 GHz is within ±1% of 10.2. Because the SIWs and resonators can be fabricated on the same SiC substrate together with HEMTs and other devices, they can be conveniently measured on-wafer for precise material-device correlation. Such permittivity characterization techniques can be extended to other frequencies, materials, and orientations.
Mechanoluminescence of (Eu, Ho)-doped oxynitride glass-ceramics from the BaO-SiO2-Si3N4 chemical system
Authors: Duval Alexis , Houizot Patrick , Rocquefelte Xavier , Rouxel Tanguy
Published: July 2023

Mechanoluminescence is observed in oxynitride glass-ceramics from the BaO-SiO2-Si3N4 chemical system, doped with Eu and Ho. Light emission was investigated by means of uniaxial compression experiments on disks and parallelepipedic bars with constant loading rates ranging from 0.3 to 300 MPa s−1 up to about 500 MPa. In agreement with previous reports on SrAl2O4-based materials [Dubernet et al., Appl. Phys. Lett. 107, 151906 (2015) and Dubernet et al., Sci. Rep. 10, 19495 (2020)], the mechanoluminescence intensity is found proportional to the mechanical power. Nevertheless, in contrast with SrAl2O4, no gain in the intensity is observed at the onset of the unloading stage, but a drop of the photoluminescence intensity during unloading. This stems from different electron trapping populations and associated energy levels for the Ba4Si6O16 phase (the dominant crystallized phase in the present glass-ceramics), which are discussed in light of density functional theory calculations.
Anticipation dynamics of pedestrians based on the elliptical social force model
Authors: Hu Xiangmin , Chen Tao , Song Yushan
Published: July 2023

Humans have excellent predictive capabilities, and this anticipation would reflect in the interactions between people. In this work, we utilize the elliptical specification of the social force model (SFM) for pedestrian movements to study how anticipation affects motion dynamics. An elliptical potential determines the interaction between pedestrians not in contact. Anticipation is introduced by shaping the ellipse according to the relative velocity. By adjusting the time to extrapolate, we can control the strength of anticipation. Simulations are conducted in four typical scenarios, i.e., circular motion, crowd gathering, escape through a bottleneck, and free wander. In each case, the qualitative observations from visual animations are followed by quantitative analyses involving different indicators. Simulation results demonstrate that anticipation plays an important role in pedestrian dynamics in several aspects. Briefly, it helps stabilize the movement by reducing perturbations, facilitates a more ordered crowd configuration, and promotes spontaneous collective motion. The findings may set avenues for further research in anticipation dynamics.
Secondary electron spectrum of metals with different surface potential barriers
Authors: Hu Xiaochuan , Chen Yanzhang , Sun Guangzhe , Zhang Yimiao , Zhang Rui
Published: July 2023

The secondary electron spectrum (SES) contains complex surface information and is widely used in surface analysis technology. A theoretical model of the SES for metals was proposed to reveal the effect of the surface potential barrier on the SES. In our model, an improved inner secondary electron energy distribution was established according to the free electron gas model. The transmission coefficient of inner secondary electrons was determined by solving the density of electronic states. Finally, the model was verified by our experiments, and the effects of the coverage fraction and potential barrier height, width, and form on the SES were comprehensively analyzed. The results show that H2O adsorption lowers the barrier height and enhances the tunneling effect, resulting in the most probable energy shifting toward the low-energy end and full width at half maximum narrowing. In addition, increasing or broadening the barrier can weaken the secondary electron tunneling effect, reduce the secondary electron number, and increase the most probable energy and the full width at half maximum. The model in this paper provides a reliable analysis method for studying the SES under different surface barriers for metals. Relevant results have significant value for the analysis of scanning electron microscopy images and optimization of secondary electron detection systems.
Construct Schottky interface containing energy-filtering effect: An efficient strategy to decouple thermopower and conductivity
Authors: Lin Zizhen , Ping Xiaofan , Zhao Dongming , Wang Lichuang , Li Menglei , Cai Zihe , Zhang Yun , Li Xinlian , Zhang Xuankai
Published: July 2023

Organic/inorganic thermoelectric hybrids demonstrate great potential for wearable applications. However, their scalability is hindered by an inferior power factor (S2σ). Nowadays, achieving deep optimization of S2σ necessitates a strategy to decouple the Seebeck coefficient (S) and electrical conductivity (σ). In this work, we propose a strategy to break the coupling between S and σ by constructing a Schottky interface that exhibits an energy-filtering effect. We validate the feasibility of this approach using a PANI/TiN–TiO2/carbon paper. The results demonstrate a 1.16-fold increase in σ and a 1.08-fold increase in S in PANI/TiN–TiO2/carbon paper achieved through the construction of a Schottky-type TiN/TiO2 interface. The separation of hole/electron at the TiN/TiO2 interface serves as the scattering center for ionized impurity scattering and facilitates the transport pathway for charge carriers. These factors are crucial in determining the simultaneous optimization of S and σ, respectively. Additionally, the energy-filtering effect of the TiN/TiO2 interface plays a positive role in the ionized impurity scattering mechanism by selectively filtering out low-energy carriers. This further strengthens decoupling of the thermoelectric properties. The 14.9% PANI/11.2% TiN–14.5% TiO2/59.44% carbon paper displays the highest S2σ and achieves a high ZT value of 223.6 μVm−1 K−2 and 0.31 at 300 K, highlighting the advantages of PANI-based thermoelectric hybrids. This work provides valuable guidance for the design of thermoelectric hybrids incorporating multi-interface morphology.
Scrutinizing pre- and post-device fabrication properties of atomic layer deposition WS2 thin films
Authors: Coleman Emma , Monaghan Scott , Gity Farzan , Mirabelli Gioele , Duffy Ray , Sheehan Brendan , Balasubramanyam Shashank , Bol Ageeth A. , Hurley Paul
Published: July 2023

In this work, we investigate the physical and electrical properties of WS2 thin films grown by a plasma-enhanced atomic layer deposition process, both before and after device fabrication. The WS2 films were deposited on thermally oxidized silicon substrates using the W(NMe2)2(NtBu)2 precursor and a H2S plasma at 450 °C. The WS2 films were approximately 8 nm thick, measured from high-resolution cross-sectional transmission electron imaging, and generally exhibited the desired horizontal basal-plane orientation of the WS2 layers to the SiO2 surface. Hall analysis revealed a p-type behavior with a carrier concentration of 1.31 × 1017 cm−3. Temperature-dependent electrical analysis of circular transfer length method test structures, with Ni/Au contacts, yielded the activation energy (Ea) of both the specific contact resistivity and the WS2 resistivity as 100 and 91 meV, respectively. The similarity of these two values indicates that the characteristics of both are dominated by the temperature dependence of the WS2 hole concentration. Change in the material, such as in sheet resistance, due to device fabrication is attributed to the chemicals and thermal treatments associated with resist spinning and baking, ambient and UV exposure, metal deposition, and metal lift off for contact pad formation.
Recent advances in linearly polarized emission from organic light-emitting diodes
Authors: Ding Ran , Ye Gao-Da , Feng Jing
Published: July 2023

Since the first example of linearly polarized organic light-emitting diodes (LP-OLEDs) reported by Dyreklev et al. [Adv. Mater. 7, 43 (1995)], remarkable efforts have been devoted to the development of LP-OLEDs, particularly in recent years. LP-OLEDs, as a next-generation light source, have attracted increasing interest for their capability of directly generating linearly polarized light as well as for their wide potential applicability in optical data storage, high-contrast display, and three-dimensional (3D) imaging. In this review, we systematically summarize the recent advances in LP-OLEDs that are roughly divided into three categories, including mechanical treatment, structural assistance, and self-assembled materials. This review is expected to provide an updated and impressive perspective on high efficiency and high polarization LP-OLEDs for a broad range of scientists in a multi-disciplinary field and draw more attention to this growing research field.
Accurate simulation of direct laser acceleration in a laser wakefield accelerator
Authors: Miller Kyle G. , Palastro John P. , Shaw Jessica L. , Li Fei , Tsung Frank S. , Decyk Viktor K. , Joshi C. , Mori Warren B.
Published: July 2023

In a laser wakefield accelerator (LWFA), an intense laser pulse excites a plasma wave that traps and accelerates electrons to relativistic energies. When the pulse overlaps the accelerated electrons, it can enhance the energy gain through direct laser acceleration (DLA) by resonantly driving the betatron oscillations of the electrons in the plasma wave. The traditional particle-in-cell (PIC) algorithm, although often the tool of choice to study DLA, contains inherent errors due to numerical dispersion and the time staggering of the electric and magnetic fields. Furthermore, conventional PIC implementations cannot reliably disentangle the fields of the plasma wave and laser pulse, which obscures interpretation of the dominant acceleration mechanism. Here, a customized field solver that reduces errors from both numerical dispersion and time staggering is used in conjunction with a field decomposition into azimuthal modes to perform PIC simulations of DLA in an LWFA. Comparisons with traditional PIC methods, model equations, and experimental data show improved accuracy with the customized solver and convergence with an order-of-magnitude fewer cells. The azimuthal-mode decomposition reveals that the most energetic electrons receive comparable energy from DLA and LWFA.
Fe-intercalated Fe3GeTe2: Potential quasi-van der Waals magnets
Authors: Huang Xiaokun , Mo Yunying , Xu Jinlin , Hu Jiangnan , Nie Xin , Chen Chao , Liu Jiaqian , Jiang Xiangping , Liu Jun-Ming
Published: July 2023

In recent years, with the fast development of magnetic devices for information technology, the demands of magnetic thin films with both high functional stability and integration flexibility rapidly increase. It is believed that building a magnet with complementary advantages of van der Waals (vdW) and non-vdW magnets, which can be described as a “quasi-vdW magnet,” will be highly appreciated. One may expect a quasi-vdW magnet to have chemical bonding between the neighboring sublayers for strong magnetic coupling, but to preserve clean surfaces with vdW feature for flexible interface engineering. For this purpose, an intercalation of magnetic atoms into the interlayer gaps of vdW magnets, as a powerful method for tuning the interlayer coupling, can be a practical approach. In this work, using the first-principles calculations, we study the potential to utilize the Fe-intercalation to transform the vdW magnets Fe3GeTe2 (FGT) into quasi-vdW magnets. As two extreme cases, it is revealed that: (i) the Fe-intercalated FGT bilayer Fe-[Fe3GeTe2]2 (Fe-[FGT]2) does have remarkable interlayer ferromagnetic coupling based on covalent bonding between the intercalated Fe atom and FGT monolayers and retains low exfoliation energy with vdW feature, suggesting that the Fe-[FGT]2 bilayer can be regarded as a quasi-vdW magnet; and (ii) the Fe-intercalation can transform the vdW FGT bulk into a non-vdW Fe-Fe3GeTe2 (Fe-FGT) bulk magnet. Accordingly, as for the intermediate cases, it is suggested that Fe-intercalated FGT multilayers (Fen−1-[FGT]n, n > 2) can also be potential quasi-vdW magnets, forming a family of magnetic thin films that provide alternative building blocks for microminiaturized magnetic devices.
Neuronal synchronization in time-varying higher-order networks
Authors: Anwar Md Sayeed , Ghosh Dibakar
Published: July 2023

A potential issue of interest is figuring out how the combination of temporal and higher-order interactions influences the collective dynamics of the brain, specifically, neuronal synchronization. Motivated by this, here we consider an ensemble of neurons interacting with each other through gap junctions, modeled by temporal higher-order networks (simplicial complexes), and study the emergence of complete neuronal synchronization. We find that the critical synaptic strength for achieving neuronal synchronization with time-varying higher-order interaction is relatively lower than that with temporal pairwise interactions or static many-body interactions. Our study shows that neuronal synchronization can occur even in the sole presence of higher-order, time-varying interactions. We also find that the enhancement in neuronal synchronization in temporal higher-order structure is highly related to the density of group interactions among the neurons. Furthermore, to characterize the local stability of the synchronous solution, we use the master stability function approach, which shows that the numerical findings are in good agreement with the analytically derived conditions.
Phase field study on the flexoelectric response of dielectric–ferroelectric multilayers
Authors: Huang Xiang , Tao Junyu , Tang Zhenxun , Liu Linjie , Zhang Fan , Chen Weijin , Zheng Yue
Published: July 2023

We report a theoretical modeling of the flexoelectric response of dielectric–ferroelectric (DE–FE) multilayers based on phase field simulations in the framework of the Landau–Ginzburg–Devonshire (LGD) theory. The correlation between negative capacitance and flexoelectric response is revealed, and the single-domain and multi-domain models are compared. It shows that the dielectric layers drive the ferroelectric layer into a negative capacitance regime, and the flexoelectric response of the multilayer is maximal when the negative capacitance of the ferroelectric layer has a minimal absolute value. Moreover, the flexoelectric response peak will be shifted to a lower temperature by increasing the thickness of dielectric layer, indicating a possibility of achieving a stronger flexoelectric response at room temperature compared with that of pure ferroelectric. However, while the single-domain model shows that the flexoelectric response peak is simply shifted to a lower temperature with near constant peak value and width, the multi-domain model reveals a significant suppressing of the flexoelectric peak by the dielectric layer. This is attributed to the formation of the vortex domain state, which eases the depolarization effect and leads to large absolute value of negative capacitance of the ferroelectric layer. Our work provides new insights into flexoelectricity in ferroelectric heterostructures.
Second spectrum of 1/f noise due to mobility fluctuations: Simulations vs experiments in suspended graphene
Authors: Zeng Weijun , Tappura Kirsi , Kamada Masahiro , Laitinen Antti , Seppä Heikki , Hakonen Pertti
Published: July 2023

Mobility fluctuations have been observed to influence 1/f noise in mesoscopic two-dimensional conductors in recent experiments. If such mobility noise can be assigned to clustering/declustering of defects/impurities, the second spectrum should also display 1/f character. In this work, we investigate the second spectrum of noise due to mobile impurities on a two-dimensional lattice both using kinetic Monte Carlo simulations (periodic boundary conditions either in one or two directions) and experiments on suspended graphene in Corbino geometry. The simulations indicate 1/fδ behavior with δ≃0.8 ± 0.15 for the second spectrum of noise, while the experiments on suspended graphene yield an exponent δ≃0.7 ± 0.3, independent of the amount of adsorbed atoms.
Cooperation driven by alike interactions in presence of social viscosity
Authors: Majhi Soumen
Published: July 2023

Cooperation observed in nearly all living systems, ranging from human and animal societies down to the scale of bacteria populations, is an astounding process through which individuals act together for mutual benefits. Despite being omnipresent, the mechanism behind the emergence and existence of cooperation in populations of selfish individuals has been a puzzle and exceedingly crucial to investigate. A number of mechanisms have been put forward to explain the stability of cooperation in the last years. In this work, we explore the evolution of cooperation for alike (assortative) interactions in populations subject to social viscosity in terms of zealous individuals. We present a comprehensive study on how a finite fraction of these committed minorities present in both cooperators and defectors govern the evolutionary game dynamics where interactions among the individuals with same strategy are more probable than random interactions. We perform a detailed analysis concerning this synergy between alike interaction and the social viscosity in the opposing individuals. We scrutinize all three principal social dilemmas, namely, the prisoner’s dilemma, the stag-hunt, and the snowdrift game, under such evolutionary setting. We have been successful to delineate this evolutionary scenario theoretically based upon the generalized replicator dynamics in the well-mixed regime.