bluuebunny/crossref_metadata_2025 huggingface dataset:
English Teacher’s Responses to the Government’s Policy on Online Learning Activities During Covid-19 Pandemic: A Case Study at SMPN 2 Mataram
Authors: Ardiningsih Sri , Yusra Kamaludin , Muhaimi Lalu
Published: August 2023

This research aims to investigate English teachers’ responses to the government policy in online learning activities during Covid-19 pandemic at SMPN 2 Mataram. The study involved 4 English teachers and six students from 8 and 9 grades as participants of the study. This is a case study qualitative research. The data were collected by interviewing the teacher about their experience in implementing the policy to find out their response, obstacles, and how they overcame them. Documentation is conducted to see their preparation for teaching online. Then, audio and visual materials were necessary to see how they implemented it. The data were analyzed by using the following procedure: (a) identify teacher response to the online learning policy, (b) identify teacher’s obstacles during the implementation of the policy (c) identify the way teachers overcome the obstacles. The result of this study showed that English teachers’ responses to the government policy in online learning activities during Covid-19 pandemic at SMPN 2 Mataram were not too surprising because they have experience in using online media and were also supported by digital facilities at school. However, the teacher state that the process is not optimal when compared to offline learning. As a follow-up to improvement, it is necessary to evaluate and develop parents or stakeholders to be actively involved in assisting students.
Editorial
Authors: Hollmann Michael , Schifferdecker-Hoch Frank
Published: August 2023

Liebe Leserinnen und Leser,

In den letzten Monaten hat die Öffentlichkeit stark über die
Leistungsfähigkeit zukunftsweisender Systeme gestaunt und diskutiert.
Anwendungen wie Chat GPT und Dall-E, die künstliche Intelligenz in alle
Ebenen des gesellschaftlichen Lebens bringen, sind dabei nur die offensichtlichen
Glanzlichter. Auch im Gesundheitswesen hat man sich mittlerweile mit dem digitalen
Versorgungsgesetz und den nicht unlängst durch das
Bundesgesundheitsministerium angekündigten Aktivitäten zur ePA
(elektronische Patientenakte) oder sogar einer digitalen Form von Disease Management
Programmen zugunsten einer digitalen und innovativen Zukunft positioniert. Dieser
Schritt ist wichtig und, wenn man ihn im Vergleich zu anderen Ländern der
Welt sieht, höchst überfällig.
Empfehlungen zur Sonografieausbildung in der prähospitalen Notfallmedizin (pPOCUS): Konsensuspapier von DGINA, DGAI, BAND, BV-ÄLRD, DGU, DIVI und DGIIN
Authors: Michels Guido , Greim Clemens-Alexander , Krohn Alexander , Ott Matthias , Feuerstein Doreen , Möckel Martin , Fuchs Nikola , Friemert Benedikt , Wolfrum Sebastian , Kiefl Daniel , Bernhard Michael , Reifferscheid Florian , Bathe Janina , Walcher Felix , Dietrich Christoph F. , Lechleuthner Alexander , Busch Hans-Jörg , Sauer Dorothea
Published: August 2023

Die Point-of-Care-Sonografie ist in der Akut- und Notfallmedizin ein fester Bestandteil der Diagnostik und Therapieeinleitung von kritisch kranken und verletzten Patienten. Während die Notfallsonografie im Rahmen der Zusatzweiterbildung für klinische Akut- und Notfallmedizin vorausgesetzt wird, wird diese für die prähospitale Notfallmedizin lediglich im (Muster-)Kursbuch Allgemeine und spezielle Notfallbehandlung als Weiterbildungsinhalt definiert. Obwohl einige Fachgesellschaften in Deutschland bereits eigene Lernkonzepte für die Notfallsonografie etabliert haben, fehlt bis dato ein einheitliches nationales Ausbildungskonzept für den Einsatz der Notfallsonografie im prähospitalem Umfeld. Experten mehrerer Fachgesellschaften haben daher als Empfehlung für die notfallmedizinische Weiterbildung ein Kurskonzept für die spezielle Ausbildung in der prähospitalen Notfallsonografie erarbeitet, welche gleichermaßen zu deren Qualitätssicherung beitragen soll.
Was will die MFA?
Authors: Scheerbaum Petra , Scheerbaum Martin , Schöffski Oliver
Published: August 2023

Zielsetzung Obwohl in Deutschland jede sechste Berufsanfängerin
eines Ausbildungsberufes die Anstellung als Medizinische Fachangestellte (MFA)
verfolgt, existieren bislang keine hinreichenden Daten zu ihren
Wünschen. Dies möchten wir mit unserer Untersuchung
ändern.

Methodik Im Rahmen einer regionalen digitalen Umfrage wurden MFA in den
ambulanten Praxen in Mittelfranken und Oberfranken zu ihren Wünschen und
Präferenzen im Berufsalltag befragt.

Ergebnisse Insgesamt sind die MFA mit ihrem Arbeitsplatz und mit dem
Umgang mit Patienten sehr zufrieden. Eine geringere Zustimmung bekamen die
Bereiche Kommunikation im Team, das Führungsverhalten sowie die
Weiterbildungsmöglichkeiten.

Schlussfolgerung Die Praxisinhaber sollten mehr Kommunikation mit ihren
MFA betreiben. Dabei sollten Entscheidungen sowie
Entwicklungsmöglichkeiten transparent besprochen werden.
Divergent Synthesis and Biological Evaluation of 2,6-Disubstituted Tetrahydropyran-Containing Natural Products: Parvistone E, Goniothalesdiol A, 6-epi-Goniothalesdiol A, and 8-epi-9-Deoxygoniopypyrone
Authors: Xie Xinni , Liu Jun , Zhao Ziyang , Pan Ruiying , Lv Qingwei , Du Yuguo
Published: August 2023

The concise and efficient synthesis of (+)-goniothalesdiol A and (–)-parvistone E (leiocarpin A), as well as the first total syntheses of (–)-6-epi-goniothalesdiol A and (–)-8-epi-9-deoxygoniopypyrone acetate, have been achieved in four or five longest linear steps based on the chiron approach. The potential biological activities of four 2,6-disubstituted tetrahydropyran-containing natural products were explored based on a panel of human cancer cell lines, BV-2 microglia and 3T3-L1 preadipocytes. Our results indicate that these four natural products display significant adipogenic activity in 3T3-L1 preadipocytes, but do not have clear effects on cancer cell proliferation or LPS stimulated microglia activation.
C-5 Epimerisation of d-Mannopyranosyl Fluorides: The Influence of Anomeric Configuration on Radical Reactivity
Authors: Ferro Vito , See Nicholas W. , Pierens Gregory K. , Krenske Elizabeth H.
Published: August 2023

The fluorine-directing effect has so far been exploited to provide short and efficient synthetic routes to rare l-ido sugars. However, the importance of anomeric configuration to its success has remained experimentally unverified. We now report on the synthesis of α- and β-configured per-O-benzoylated mannopyranosyl fluorides and initially show that their reactivity towards photo-bromination is strongly dependent on the anomeric configuration. The stereochemical basis of the fluorine-directing effect is then validated by revealing the striking difference in stereoselectivity observed for the free-radical reductions of the isolated 5-C-bromo sugars. This work importantly provides a synthetic route to a donor-functionalised derivative of l-gulose and reveals new insights into the behaviour of glycosyl radicals.
Nationwide Analysis of the Outcomes and Mortality of Hospitalized Infants with Concomitant Diagnosis of COVID-19
Authors: Krishnan Parvathy , Malik Aaqib , Isath Ameesh , Bandyopadhyay Dhrubajyoti , Goel Akshay , Parton Lance , Chandrasekharan Praveen , Singh Meenakshi
Published: August 2023

Objective Coronavirus disease 2019 (COVID-19) generally causes milder illness in the pediatric population. However, infants represent a higher-risk population with evolving symptomatology and severity. There is a paucity of large population-based data on the impact of COVID-19 on hospitalized infants.

Study Design In this large cohort study, the National Inpatient Sample database was queried for all infant hospital admissions between January and December 2020 in the United States, with and without a diagnosis of COVID-19 based on ICD-10-CM U07. The mortality and morbidity of infants with and without COVID-19 were evaluated. Parent-reported race and outcomes were also analyzed.

Results A weighted total of 3,754,236 infants who were hospitalized were identified, of which 4,265 patients (0.11%) had a concomitant diagnosis of COVID-19. Infants with COVID-19 had similar mortality and extracorporeal membrane oxygenation utilization. Infants with concomitant COVID-19 had a higher rate of respiratory failure, congestive heart failure, acute kidney injury, and coagulopathy. Compared with Caucasian infants and Asian infants, Hispanic and African American infants were more likely to have COVID-19 hospital admissions than hospitalizations without COVID-19 diagnosis. Patients with lower median household income represented the majority of the COVID-19 hospitalization. The infants with COVID-19 were more likely to have Medicaid or Medicare insurance and less likely to have private insurance.

Conclusion In this large cohort of hospitalized infants with COVID-19, the infection was associated with complications, including respiratory failure and endotracheal intubations but not associated with a higher risk for mortality. Infants from racial minorities and lower socioeconomic strata carry the highest burden of COVID-19 infection.

Key Points
Using Bar Velocity to Assess Post-match Neuromuscular Fatigue in
Young Soccer Players
Authors: Barreira João , Gantois Petrus , Castro Jorge , Mesquita Xavier , Peixoto Rafael , Cid Miguel Ferreira , Loturco Irineu , Sousa Ana , Nakamura Fábio Yuzo
Published: August 2023

This study aimed to investigate the recovery of neuromuscular performance using
mechanical parameters collected during jump (vertical and horizontal) and
strength-power exercises in youth soccer players after official soccer matches.
Twenty-one outfield highly trained youth male soccer athletes (age: 18.23±0.73
years; weight: 72.12±6.99 kg; height: 1.78±0.08 m) from two teams competing in
the 1st division of U-19 Portuguese National Championship
participated in this study. Players completed a battery of physical tests at
−2 h, + 30 min, +24 h, and +48 h in relation to the match. Countermovement jump
height, horizontal jump distance, and bar velocity during the half squat, bench
press, and hip thrust exercises, at fixed loads, were recorded. Countermovement
jump was impaired until 24 h post-match (−1.7% from pre- to 24 h
post-match, p=0.050; ES=−0.82). Half-squat bar velocity was
reduced immediately following the match (−6.8% from pre-match,
p=0.004; ES=−0.64) but recovered at +24 h (+2.9%, p=1.00;
ES=0.02). Hip-thrust bar velocity was reduced for up to 48 h post-match
(−7.4% from pre- to 48 h post-match, p<0.001;
ES=−0.80). No impairments were found in the horizontal jump and bench
press at any moment. Our findings show prolonged decrements in strength of the
posterior chain following a soccer match, measured in the hip thrust exercise,
while the other exercises displayed faster recovery dynamics.
Endovascular Thrombectomy for Anterior Circulation Large Vessel Occlusion Stroke: An Evolution of Trials
Authors: Starikova Natalia , Räty Silja , Strbian Daniel , Kaiser Daniel P. O. , Gerber Johannes C. , Huo Xiaochuan , Qiu Zhongming , Chen Hui-Sheng , Kaesmacher Johannes , Pallesen Lars-Peder , Barlinn Kristian , Sun Dapeng , Abdalkader Mohamad , Nguyen Thanh N. , Nagel Simon , Miao Zhongrong , Puetz Volker
Published: August 2023

The last decade's progress in demonstrating the clinical benefit of endovascular thrombectomy (EVT) in patients with large vessel occlusion stroke has transformed the paradigm of care for these patients. This review presents the milestones in implementing EVT as standard of care, demonstrates the current state of evidence, provides guidance for identifying the candidate patient for EVT, and highlights unsolved and controversial issues. Ongoing trials investigate broadening of EVT indications for patients who present with large core infarction, adjunctive intra-arterial thrombolysis, medium vessel occlusion, low NIHSS, and tandem occlusion.
Cohomologies and deformations of O-operators on Lie triple systems
Authors: Chtioui Taoufik , Hajjaji Atef , Mabrouk Sami , Makhlouf Abdenacer
Published: August 2023

In this paper, first, we provide a graded Lie algebra whose Maurer–Cartan elements characterize Lie triple system structures. Then, we use it to study cohomology and deformations of O-operators on Lie triple systems by constructing a Lie 3-algebra whose Maurer–Cartan elements are O-operators. Furthermore, we define a cohomology of an O-operator T as the Lie–Yamaguti cohomology of a certain Lie triple system induced by T with coefficients in a suitable representation. Therefore, we consider infinitesimal and formal deformations of O-operators from a cohomological viewpoint. Moreover, we provide relationships between O-operators on Lie algebras and associated Lie triple systems.
Modelling the eye movements of dyslexic children during reading as a continuous time random walk
Authors: Iaconis F. R. , Meo M. , Del Punta J. A. , Gasaneo G.
Published: August 2023

The study of eye movements during reading is considered a valuable tool for understanding the underlying cognitive processes and for its ability to detect alterations that could be associated with neurocognitive deficiencies or visual conditions. During reading, the gaze moves from one position to the next on the text performing a saccade–fixation sequence. This dynamics resembles processes usually described as continuous time random walk, where the jumps are the saccadic movements and waiting times are the duration of fixations. The time between jumps (intersaccadic time) consists of stochastic waiting time and flight time, which is a function of the jump length (the amplitude of the saccade). This motivates the present proposal of a model of eye movements during reading in the framework of the intermittent random walk but considering the time between jumps as a combined stochastic-deterministic process. The parameters used in this model were obtained from records of eye movements of children with dyslexia and typically developed for children performing a reading task. The jump lengths arise from the characteristics of the selected text. The time required for the flights was obtained based on a previously proposed model. Synthetic signals were generated and compared with actual eye movement signals in a complexity-entropy plane.
Painlevé V and confluent Heun equations associated with a perturbed Gaussian unitary ensemble
Authors: Yu Jianduo , Chen Siqi , Li Chuanzhong , Zhu Mengkun , Chen Yang
Published: August 2023

We discuss the monic polynomials of degree n orthogonal with respect to the perturbed Gaussian weight w(z,t)=|z|α(z2+t)λe−z2,z∈R,t>0,α>−1,λ>0, which arises from a symmetrization of a semi-classical Laguerre weight wLag(z,t)=zγ(z+t)ρe−z,z∈R+,t>0,γ>−1,ρ>0. The weight wLag(z) has been widely investigated in multiple-input multi-output antenna wireless communication systems in information theory. Based on the ladder operator method, two auxiliary quantities, Rn(t) and rn(t), which are related to the three-term recurrence coefficients βn(t), are defined, and we show that they satisfy coupled Riccati equations. This turns to be a particular Painlevé V (PV, for short), i.e., PVλ22,−(1−(−1)nα)28,−2n+α+2λ+12,−12. We also consider the quantity σn(t)≔2tddtlnDn(t), which is allied to the logarithmic derivative of the Hankel determinant Dn(t). The difference and differential equations satisfied by σn(t), as well as an alternative integral representation of Dn(t), are obtained. The asymptotics of the Hankel determinant under a suitable double scaling, i.e., n → ∞ and t → 0 such that s ≔ 4nt is fixed, are established. Finally, by using the second order difference equation satisfied by the recurrence coefficients, we obtain the large n full asymptotic expansions of βn(t) with the aid of Dyson’s Coulomb fluid approach. By employing these results, the second differential equations satisfied by the orthogonal polynomials will be reduced to a confluent Heun equation.
Determination of the critical contact separation length for DC interruption in a vacuum subject to an external transverse magnetic field
Authors: Ma Hui , Liu Shaowei , Chen Jinlong , Yu Chen , Geng Yingsan , Liu Zhiyuan , Wang Jianhua
Published: August 2023

The objective of this work is to experimentally determine the critical contact separation length Lcritical for DC interruption in vacuum under an external transverse magnetic field (TMF), according the interruption behaviors and vacuum arc characteristics. L is defined as the separation length at the instant of TMF application. Lcritical is the critical and the minimal necessary separation length of the contacts for a successful DC interruption in vacuum. A pair of Helmholtz coils was used to generate the external TMF. A high-speed camera was used to record the vacuum arc appearance. The experimental results quantitatively determine Lcritical for DC vacuum interruption under a certain DC and the external TMF. When the DC ranged from 100 to 500 A under an external TMF of 30 mT, Lcritical ranged from 2.1 to 3.7 mm and did not show linear variation. Second, the extinguishing time of DC vacuum interruption te at various currents significantly increased in a similar pattern under decreasing L in the range of 0.3–1.6 ms. The decrease in L mainly increased the duration of the stable stage and had little apparent influence on the duration of the unstable stage of the DC vacuum arc. Third, the physical mechanism determining Lcritical in DC vacuum interruption under a TMF could be explained from two aspects: the expansion of the vacuum arc column and the diffusion of the metal plasma. In successful DC vacuum interruption, Lcritical should be large enough for the formation and expansion of the “C”-shaped arc column, and enough space should be available for the diffusion of the metal plasma.
Comprehensive review of power system oscillations in large-scale power electronic-based renewable energy power plants
Authors: Liu Ni , Wang Hong , Zhou Dangsheng , Shi Hexi , Chen Zhe
Published: August 2023

Recently, the large-scale integration of power electronic-based renewable energy power plants has changed the operation and response mechanism of the power system, resulting in several emerging oscillation issues that have seriously been threatening the system's stability. It helps us to recognize the similarities and differences among the triggering causes and formation mechanisms of oscillation scenarios. Following several typical oscillation events in the real world and the timescale decomposition method, this paper comprehensively reviews the wide-bandwidth oscillation study from the aspects of the analysis methods, possible cause, mechanism, and mitigation solution. The paper provides a perspective to classify the oscillations in the modern power systems on the basis of the oscillation frequency and the main oscillation module. This classification framework involves not only emerging oscillations in the power system with large-scale renewable energy sources integration but also includes typical oscillations in traditional power systems. It also systematically presents the relative relationship, development process, and inner influence between emerging oscillations and typical oscillations. Based on this review, the future research is suggested to focus on the relationship between different analytical methods or oscillation mechanisms, as well as the stability risk assessment of hybrid alternating current and direct current power systems.
Exactly solvable complex PT symmetry potential A[sech(λx) + i tanh(λx)]
Authors: Yang Wei
Published: August 2023

We obtained the exact solutions of the PT symmetric potential V(x) = A[sech(λx) + i tanh(λx)] and found that this system has no bound-state. The PT symmetric potential was first studied in this article, and the handedness effect is shown from reflection coefficients. As the asymptotically non-vanishing imaginary potential component, when the direction of the incident wave is opposite, the transmission coefficient will emerge a complex phase factor.
Study of backward Brillouin scattering in gas-filled anti-resonant fibers
Authors: Galal Malak , Zhang Li , Gao Shoufei , Wang Yingying , Thévenaz Luc
Published: August 2023

Brillouin scattering in gas shows unmatched gain properties in hollow-core optical fibers filled at high pressure. Here, the gain characteristics are studied for two common gases, namely, N2 and CO2, which show distinct features and are compared to expected responses deduced from conventional thermodynamic models for gases. This is realized—for the first time to our knowledge—in anti-resonant hollow-core optical fibers, demonstrating their full suitability for generating and exploiting Brillouin amplification in fluidic media. The potential of Brillouin scattering in gases is manifested in a distributed temperature sensor that is totally immune to strain and benefits from the absence of shear stress in the gaseous medium. The experimental results presented indicate that gases with smaller molecular masses show a higher temperature sensitivity than gases with larger masses. This inverse proportionality between the temperature sensitivity and the molecular mass of a gas shown in the experiment qualitatively agrees with the ideal gas model.
Analytical solutions and dynamic behaviors to synchronous oscillation of same bubbles at vertices of cuboid and rectangle
Authors: Qin Yupeng , Wang Zhen , Zou Li
Published: August 2023

The present work focuses on the nonlinear dynamics of the synchronous oscillating multiple bubbles in two typical spatial locations, namely, cuboid and rectangle arrangements. The governing equation for such synchronous oscillating multiple bubbles is derived from a modified Rayleigh–Plesset equation. Theoretical results including the collapse time and analytical solution (in three forms) for multiple vapor bubbles, as well as the maximum/minimum radii, oscillation period, and analytical solution in the form of Weierstrass elliptic function for multiple gas-filled ones, are provided. On the basis of these results, we not only study the dynamic characteristics of multi-bubbles straightforwardly but also carefully observe a series of evolution behaviors of bubbles when the number of bubbles decreases gradually on the order of 8→4→2→1. It should be pointed out that we also compare the multi-bubble behaviors between the general cuboid/rectangle arrangements and the corresponding cube/square arrangements under two reasonable restrictions, respectively. Furthermore, the limiting behaviors of the synchronous oscillating multiple gas-filled bubbles are discussed as the initial pressure of the gas in bubble approaches to zero.
Graphene and related materials for the Internet of Bio-Nano Things
Authors: Civas Meltem , Kuscu Murat , Cetinkaya Oktay , Ortlek Beyza E. , Akan Ozgur B.
Published: August 2023

The Internet of Bio-Nano Things (IoBNT) is a transformative communication framework characterized by heterogeneous networks comprising both biological entities and artificial micro/nano-scale devices, so-called Bio-Nano Things (BNTs), interfaced with conventional communication networks for enabling innovative biomedical and environmental applications. Realizing the potential of IoBNT requires the development of new and unconventional communication technologies, such as molecular communications, as well as the corresponding transceivers, bio-cyber interfacing technologies connecting the biochemical domain of IoBNT to the electromagnetic domain of conventional networks, and miniaturized energy harvesting and storage components for the continuous power supply to BNTs. Graphene and related materials (GRMs) exhibit exceptional electrical, optical, biochemical, and mechanical properties, rendering them ideal candidates for addressing the challenges posed by IoBNT. This perspective article highlights recent advancements in GRM-based device technologies that are promising for implementing the core components of IoBNT. By identifying the unique opportunities afforded by GRMs and aligning them with the practical challenges associated with IoBNT, particularly in the materials domain, our aim is to accelerate the transition of envisaged IoBNT applications from theoretical concepts to practical implementations while also uncovering new application areas for GRMs.
A novel fixed-time stability lemma and its application in the stability analysis of BAM neural networks
Authors: Chen Chuan , Li Lixiang , Mi Ling , Zhao Dawei , Qin Xiaoli
Published: August 2023

In this paper, we put forward an interesting fixed-time (FXT) stability lemma, which is based on a whole new judging condition, and the minimum upper bound for the stability start time is obtained. In the new FXT stability lemma, the mathematical relation between the upper bound of the stability start time and the system parameters is very simple, and the judgment condition only involves two system parameters. To indicate the usability of the new FXT stability lemma, we utilize it to study the FXT stability of a bidirectional associative memory neural network (BAMNN) with bounded perturbations via sliding mode control. To match the developed FXT stability lemma, novel sliding mode state variables and a two-layer sliding mode controller are designed. According to the developed FXT stability lemma, the perturbed BAMNN can achieve FXT stability under the devised sliding mode controller. The upper bound of the stability start time can be calculated easily by virtue of the control parameters, and the sufficient conditions guaranteeing that the perturbed BAMNN can achieve FXT stability have also been derived. Last, we provide some confirmatory simulations.
Angular magnetic field dependence of a doubly clamped magnetoelectric resonator
Authors: Mion Thomas , Lefler Benjamin M. , Staruch Margo , Bennett Steven , Gottron Norman , Lofland Samuel E. , Bussmann Konrad , Gangemi Nicholas , Baldwin Jeffrey , Finkel Peter
Published: August 2023

Angular dependence of magnetic field response of fully suspended resonant microelectromechanical double-clamped magnetoelectric beams was investigated as the basis for a vector magnetometer utilizing the magnetically induced change in fundamental resonance frequency. Strain-coupled magnetostrictive iron cobalt (FeCo) and piezoelectric aluminum nitride layers together constitute a magnetoelectric heterostructure with a high magnetic field sensitivity of 70 Hz/mT along the beam axis and a transfer function of 47 V/T at 10 Hz. The fundamental frequency shift to an external magnetic field is found to be strongly anisotropic with a relative variation of more than 3% between perpendicular and parallel field orientations with respect to the long axis of the beam at a field of 100 mT. This design can form the basis for an on-chip high sensitivity vector magnetometer operating with ultra-low power when multiplexed with two or more resonators.
Collective dynamics of nonlocally coupled Hindmarsh–Rose neurons modified by magnetic flux
Authors: Messee Goulefack L. , F. Ramos Marlon , Yamapi R. , Anteneodo C.
Published: August 2023

We investigate the dynamics of nonlocally coupled Hindmarsh–Rose neurons, modified by coupling the induced magnetic flux to the membrane potential with a quadratic memristor of strength k. The nonlocal coupling consists of the interaction of each neuron with its neighbors within a fixed radius, which influence the membrane potential of the neuron with coupling intensity σ. For such local dynamics and network of interactions, we investigate how variations of k and σ affect the collective dynamics. We find that when increasing k as well as when increasing σ, coherence typically increases, except for small ranges of these parameters where the opposite behavior can occur. Besides affecting coherence, varying k also affects the pattern of bursts and spikes, namely, for large enough k, burst frequency is augmented, the number and amplitude of the spikes are reduced, and quiescent periods become longer. Results are displayed for an intermediate range of interactions with radius 1/4 of the network size, but we also varied the range of interactions, ranging from first-neighbor to all-to-all couplings, observing in all cases a qualitatively similar impact of induction.
Non-Markovian effects of conformational fluctuations on the global diffusivity in Langevin equation with fluctuating diffusivity
Authors: Kimura Mutsumi , Akimoto Takuma
Published: August 2023

Local diffusivity of a protein depends crucially on the conformation, and the conformational fluctuations are often non-Markovian. Here, we investigate the Langevin equation with non-Markovian fluctuating diffusivity, where the fluctuating diffusivity is modeled by a generalized Langevin equation under a double-well potential. We find that non-Markovian fluctuating diffusivity affects the global diffusivity, i.e., the diffusion coefficient obtained by the long-time trajectories when the memory kernel in the generalized Langevin equation is a power-law form. On the other hand, the diffusion coefficient does not change when the memory kernel is exponential. More precisely, the global diffusivity obtained by a trajectory whose length is longer than the longest relaxation time in the memory kernel is not affected by the non-Markovian fluctuating diffusivity. We show that these non-Markovian effects are the consequences of an everlasting effect of the initial condition on the stationary distribution in the generalized Langevin equation under a double-well potential due to long-term memory.
Chaos, periodic structures, and multistability: Complex dynamical behaviors of an eco-epidemiological model in parameter planes
Authors: Garai Shilpa , Hossain Mainul , Karmakar Sarbari , Pal Nikhil
Published: August 2023

The environmental characteristics of a biological system are imbibed in some particular parameters of that system. Significant changes in any system parameter exert influence on the system dynamics as well as the persistence of interacting species. In this article, we explore the rich and tangled dynamics of an eco-epidemiological system by studying different parametric planes of the system. In the parameter planes, we find a variety of complex and subtle properties of the system, like the presence of a variety of intricate regular structures within irregular regimes, that cannot be found through a single parameter variation. Also, we find a new type of structure like an “eye” in a parametric plane. We notice the bistability between distinct pairs of attractors and also identify the coexistence of three periodic attractors. The most notable observation of this study is the coexistence of three periodic attractors and a chaotic attractor, which is a rare occurrence in biological systems. We also plot the basins for each set of coexisting attractors and see the existence of fractal basins in the system, which look like a “conch.” The appearance of fractal basins in a system causes enormous complications in predicting the system’s state in the long run. Variations in initial conditions and changes in parameters in parametric planes are key to managing the behavior of a system.
Synchronization stability and multi-timescale analysis of renewable-dominated power systems
Authors: Ma Rui , Zhang Yayao , Han Miao , Kurths Jürgen , Zhan Meng
Published: August 2023

Synchronization is one of the key issues in three-phase AC power systems. Its characteristics have been dramatically changed with the large-scale integration of power-electronic-based renewable energy, mainly including a permanent magnetic synchronous generator (PMSG) and a double-fed induction generator (DFIG) for wind energy and a photovoltaic (PV) generator for solar energy. In this paper, we review recent progresses on the synchronization stability and multi-timescale properties of the renewable-dominated power system (RDPS), from nodes and network perspectives. All PMSG, DFIG, and PV are studied. In the traditional synchronous generator (SG) dominated power system, its dynamics can be described by the differential–algebraic equations (DAEs), where the dynamic apparatuses are modeled by differential equations and the stationary networks are described by algebraic equations. Unlike the single electromechanical timescale and DAE description for the SG-dominated power system, the RDPS dynamics should be described by the multiscale dynamics of both nodes and networks. For three different timescales, including the AC current control, DC voltage control, and rotor electromechanical timescales, their corresponding models are well established. In addition, for the multiscale network dynamics, the dynamical network within the AC current control timescale, which should be described by differential equations, can also be simplified as algebraic equations. Thus, the RDPS dynamics can be put into a similar DAE diagram for each timescale to the traditional power system dynamics, with which most of power electrical engineers are familiar. It is also found that the phase-locked loop for synchronization plays a crucial role in the whole system dynamics. The differences in the synchronization and multiscale characteristics between the traditional power system and the RDPS are well uncovered and summarized. Therefore, the merit of this paper is to establish a basic physical picture for the stability mechanism in the RDPS, which still lacks systematic studies and is controversial in the field of electrical power engineering.
Semi-analytical modeling of sediment-laden open-channel flows with the effects of stratification, hindered settling, and eddy viscosities
Authors: Kumbhakar Manotosh , Tsai Christina W. , Absi Rafik
Published: August 2023

This study proposes semi-analytical models for simultaneous distribution of fluid velocity and suspended sediment concentration in an open-channel turbulent flow using three kinds of eddy viscosities. Apart from the classical parabolic eddy viscosity which is based on a log-law velocity profile, we consider two recently proposed eddy viscosities based on the concept of velocity and length scales. To deal with the flows with high sediment concentration, several turbulent features such as the hindered settling mechanism and the stratification effect are incorporated in the model. The governing system of highly nonlinear differential equations is solved using the homotopy analysis method (HAM), which produces solutions in the form of convergent series. Numerical and theoretical convergence analyses are provided for all three types of eddy viscosities. The effects of parameters on the derived models are discussed physically. Experimental data on both dilute and non-dilute flows are considered to verify the HAM-based solutions. The effects of the stratification correction factor (β) and the turbulent Schmidt number (α) reveal that they should be determined optimally for applicability of the proposed models in terms of accurate prediction with data. This optimal procedure required further investigation of these parameters, and, thus, an analysis of β and α is carried out, which linked them with the particle diameter through particle settling velocity, reference fluid velocity, and reference sediment concentration by proposing regression equations. Furthermore, using the optimal values of the parameters, the proposed models corresponding to the eddy viscosities based on the exponentially decreasing turbulent kinetic energy function and von Karman's similarity hypothesis are seen to be superior to the model corresponding to a parabolic eddy viscosity. Finally, a comment on the HAM is made where it is observed that the method can remove the numerical singularity of the governing equations at the water surface, which arises because of the consideration of vanishing eddy viscosity thereat.
Two-level systems in nucleated and non-nucleated epitaxial alpha-tantalum films
Authors: Alegria Loren D. , Tennant Daniel M. , Chaves Kevin R. , Lee Jonathan R. I. , O'Kelley Sean R. , Rosen Yaniv J. , DuBois Jonathan L.
Published: August 2023

Building usefully coherent superconducting quantum processors depends on reducing losses in their constituent materials [I. Siddiqi, Nat. Rev. Mater. 6, 875–891 (2021)]. Tantalum, like niobium, has proven utility as the primary superconducting layer within highly coherent qubits [Place et al., Nat. Commun. 12(1), 1–6 (2021) and Wang et al., npj Quantum Inf. 8(1), 1–6 (2022)]. However, unlike Nb, high temperatures are typically used to stabilize the desirable body-centered-cubic phase, α-Ta, during thin film deposition. It has long been known that a thin Nb layer permits the room-temperature nucleation of α-Ta [Westwood et al., Tantalum Thin Films (Academic Press, 1975); D. W. Face and D. E. Prober, J. Vac. Sci. Technol. A 5, 3408–3408 (1987); and Colin et al., Acta Mater. 126, 481–493 (2017)], but here we observe the epitaxial process and present few-photon microwave loss measurements in Nb-nucleated Ta films. We compare resonators patterned from Ta films grown at high temperature (500 °C) and films nucleated at room temperature, in order to understand the impact of the crystalline order on quantum coherence. In both cases, films grew with Al2O3 (001) ǁ Ta (110), indicating that the epitaxial orientation is independent of temperature and is preserved across the Nb/Ta interface. We use conventional low-power spectroscopy to measure two level system (TLS) loss as well as an electric-field bias technique to measure the effective dipole moments of TLS in the surfaces of resonators. In our measurements, Nb-nucleated Ta resonators had greater loss tangent (1.5 ± 0.1 × 10−5) than non-nucleated (5 ± 1 × 10−6) in approximate proportion to defect densities as characterized by x-ray diffraction (0.27° vs 0.18° [110] reflection width) and electron microscopy (30 vs 70 nm domain size). The dependence of the loss tangent on domain size indicates that the development of more ordered Ta films is likely to lead to improvements in qubit coherence times [I. Siddiqi, Nat. Rev. Mater. 6, 875–891 (2021) and Premkumar et al., Commun. Mater. 2(1), 1–9 (2021)]. Moreover, low-temperature α-Ta epitaxy may enable the growth of microstate-free heterostructures, which would not withstand high temperature processing [McSkimming et al., J. Vac. Sci. Technol. A 35, 021401 (2017)].
Magnetospheric Multiscale measurements of turbulent electric fields in earth's magnetosheath: How do plasma conditions influence the balance of terms in generalized Ohm's law?
Authors: Lewis Harry C. , Stawarz Julia E. , Franci Luca , Matteini Lorenzo , Klein Kristopher , Salem Chadi S. , Burch James L. , Ergun Robert E. , Giles Barbara L. , Russell Christopher T. , Lindqvist Per-Arne
Published: August 2023

Turbulence is ubiquitous within space plasmas, where it is associated with numerous nonlinear interactions. Magnetospheric Multiscale (MMS) provides the unique opportunity to decompose the electric field (E) dynamics into contributions from different linear and nonlinear processes via direct measurements of the terms in generalized Ohm's law. Using high-resolution multipoint measurements, we compute the magnetohydrodynamic (EMHD), Hall (EHall), electron pressure (EPe), and electron inertia (Einertia) terms for 60 turbulent magnetosheath intervals, to uncover the varying contributions to the dynamics as a function of scale for different plasma conditions. We identify key spectral characteristics of the Ohm's law terms: the Hall scale, kHall, where EHall becomes dominant over EMHD; the relative amplitude of EPe to EHall, which is constant in the sub-ion range; and the relative scaling of the nonlinear and linear components of EMHD and of EHall, which are independent of scale. We find expressions for the characteristics as a function of plasma conditions. The underlying relationship between turbulent fluctuation amplitudes and ambient plasma conditions is discussed. Depending on the interval, we observe that EMHD and EHall can be dominated by either nonlinear or linear dynamics. We find that EPe is dominated by its linear contributions, with a tendency for electron temperature fluctuations to dominate at small scales. The findings are not consistent with existing linear kinetic Alfvén wave theory for isothermal fluctuations. Our work shows how contributions to turbulent dynamics change in different plasma conditions, which may provide insight into other turbulent plasma environments.
Ultra-chaotic motion in the hexagonal Beltrami flow
Authors: Hu Tianli , Liao Shijun
Published: August 2023

In this paper, we investigate the influence of small disturbance on the statistical behaviors of fluid particles of the three-dimensional divergence-free hexagonal Beltrami flow from a Lagrangian point of view. Due to the butterfly-effect, numerical noise increases exponentially for chaotic dynamic systems. Thus, a powerful strategy, namely, the clean numerical simulation, is used to gain reliable/convergent trajectory in a long enough interval of time. It is found that the statistics of chaotic trajectory of fluid particles are stable in some cases, corresponding to the so-called “normal-chaos,” but unstable in some cases, i.e., rather sensitive to small disturbances, corresponding to the so-called “ultra-chaos,” which is a new concept proposed currently. Obviously, an ultra-chaotic trajectory of fluid particles is at a higher disorder than a normal chaotic trajectory. In theory, it is impossible to repeat any experimental/numerical results of an ultra-chaotic system even by means of statistics, but reproducibility is a corner-stone of our modern science paradigm. Hence, the wide existence or non-existence of ultra-chaos has a very important meaning. In this paper, we illustrate that the ultra-chaotic trajectories of fluid particles indeed widely exist in a hexagonal Beltrami flow field. This fact is important for deepening our understanding of chaotic dynamic systems and revealing the limitations of our paradigm of modern science.
Reconstruction of missing flow field from imperfect turbulent flows by machine learning
Authors: Luo Zhaohui , Wang Longyan , Xu Jian , Wang Zilu , Chen Meng , Yuan Jianping , Tan Andy C. C.
Published: August 2023

Obtaining reliable flow data is essential for the fluid mechanics analysis and control, and various measurement techniques have been proposed to achieve this goal. However, imperfect data can occur in experimental scenarios, particularly in the particle image velocimetry technique, resulting in insufficient flow data for accurate analysis. To address this issue, a novel machine learning-based multi-scale autoencoder (MS-AE) framework is proposed to reconstruct missing flow fields from imperfect turbulent flows. The framework includes two missing flow reconstruction strategies: complementary flow reconstruction and non-complementary flow reconstruction. The former requires two independent measurements of complementary paired flow fields, posing challenges for real-world implementation, whereas the latter requires only a single measurement, offering greater flexibility. A benchmark case study of channel flow with ordinary missing configuration is used to assess the performance of the MS-AE framework. The results demonstrate that the MS-AE framework outperforms the traditional fused proper orthogonal decomposition method in reconstructing missing turbulent flow, irrespective of the availability of complementary paired faulty flow fields. Furthermore, the robustness of the proposed MS-AE approach is assessed by exploring its sensitivity to various factors, such as latent size, overlap proportion, reconstruction efficiency, and suitability for multiscale turbulent flow structures. The new method has the potential to contribute to more effective flow control in the future, thanks to its characteristic that eliminates the requirement for complementary flow fields.
Local geometry of a weak normal shock wave interacting with turbulence
Authors: Kusuhata Amane , Tanaka Kento , Watanabe Tomoaki , Nagata Koji , Sasoh Akihiro
Published: August 2023

The shock surface geometry is investigated with direct numerical simulations of a weak normal shock wave propagating in turbulence. The geometry is quantified with the principal curvatures of the surface. A large part of the surface has an approximately flat saddle shape, while elliptic concave and convex shapes with a large curvature intermittently appear on the shock surface. The pressure–dilatation correlation in the governing equation of pressure is investigated at the shock wave with the decomposition into three terms associated with the velocity gradients in the two directions of the principal curvatures and the normal direction of the shock wave. Fluid expansion in the tangential direction occurs at the shock wave with a convex shape in the direction of the shock propagation, resulting in a smaller pressure jump across the shock wave. For a concave shape, compression in the tangential direction can amplify the pressure jump. Consistently, small and large shock Mach numbers are observed for convex and concave shapes, respectively. The geometric influences are the most significant for elliptic concave and convex shapes with approximately equal curvatures in the two principal directions because the compression or expansion occurs in all tangential directions. These relations between the shock surface geometry and shock Mach number observed in turbulence are consistent with the theory of deformed shock waves, suggesting that the three-dimensional geometrical features of the shock surface are important in the modulation of shock waves due to turbulence.
Parametric amplification induced giant nonreciprocal unconventional photon blockade in a single microring resonator
Authors: Liu Da-Wei , Huang Kai-Wei , Wu Ying , Si Liu-Gang
Published: August 2023

We theoretically propose an all-optical scheme to implement a giant nonreciprocal unconventional photon blockade (UPB) in a single photonic device. By considering the backscattering coupling between clockwise (CW) and counterclockwise (CCW) waves with the same frequency, we show that in the single microring χ2-nonlinear resonator, UPB happens when the resonator is pumped to induce a parametric amplification nonlinear process in one direction but not the other. This originates from the induced nonreciprocal transmission for the driving mode's resonance by the unidirectionally pumping, leading to different quantum interference effects between distinct driven-dissipative excitation paths for the CW and CCW modes. We analytically give the optimal conditions for achieving the nonreciprocal UPB. Our work provides a way to achieve single quantum nonreciprocal devices without moving parts, which greatly simplifies its experimental implementation.
Field-free spin–orbit torque-induced magnetization switching in a miscut-substrate driven slant-perpendicular magnetic anisotropy system
Authors: An Suhyeok , Kim Jin-A , Lee Soobeom , Lee Ki-Seung , You Chun-Yeol
Published: August 2023

In a perpendicular magnetic anisotropy (PMA) system, spin–orbit torque (SOT)-induced magnetization switching shows promise in terms of high speed and stability, but additional in-plane directional symmetry breaking is necessary to achieve deterministic switching. Here, we observed all-electric magnetization switching by SOT in a conventional heavy metal/ferromagnetic structure deposited on a 3.25° miscut sapphire substrate. To better understand the origin of field-free switching, we conducted azimuthal angle-dependent PMA analysis and found that the magnetic anisotropy is slightly tilted in the direction of the miscut step. Despite a few degrees of tilting angle (<3°), we also confirmed that a slant PMA is the origin of the field-free switching by micromagnetic simulations.