bluuebunny/crossref_metadata_2025 huggingface dataset:
Surgical and Interventional Radiology Management of Vascular and Biliary Complications in Liver Transplantation: Narrative Review
Authors: Barragan Camilo , Vera Alonso , Hoyos Sergio , Bejarano Diana , Lopez-Ruiz Ana Maria , Grippi Francisco , Mejia Alejandro , Bayona Molano María del Pilar
Published: September 2023

Liver transplant patients require a multidisciplinary and personalized approach to optimize outcomes. Posttransplant complications can be devastating for the patient and can jeopardize graft survival. Therefore, a careful evaluation and stepwise decision-making process is necessary to determine the best strategy, whether it is surgical, interventional, or a combination of both. While access to liver transplant interventions in Latin America can be more limited compared with other parts of the world, many countries in the region have made significant progress in developing their liver transplant programs and improving the management of posttransplant complications. For example, in Brazil, specialized transplant centers and multidisciplinary teams have been established to reduce morbidity and improve graft survival rates. The article also explores the latest advancements in interventional radiology techniques, such as angioplasty, stent placement, and embolization, and how they can be used to successfully treat these complications. Overall, this article highlights the importance of a comprehensive approach to managing complications in liver transplant patients and emphasizes how individualized treatment plans can lead to improved outcomes, even in settings with limited resources.
The Transition to Ophthalmology Residency: A National Survey of the Combined Ophthalmology PGY-1 Program
Authors: Azad Amee D. , Yuan Melissa , Weinert Marguerite , Rosenblatt Tatiana R. , Miller Joan W. , Lorch Alice
Published: September 2023

Background In 2017, the Accreditation Council for Graduate Medical Education announced all ophthalmology residency programs would provide a combined transitional or joint preliminary program for first postgraduate year (PGY-1) residents, with mandatory implementation by 2023.

Purpose This study aimed to survey ophthalmology residency program directors, postgraduate year 2 (PGY-2) ophthalmology residents who were a part of the first, official combined ophthalmology PGY-1 year, and postgraduate year 3 (PGY-3) residents who were a PGY-1 resident the year prior to integration to evaluate characteristics and perspectives on the combined ophthalmology PGY-1 year.

Methods A national, internet survey-based study approved by the Association of University Professors of Ophthalmology (AUPO) was disseminated to the AUPO listserv of program directors (PDs) and PGY-2 and PGY-3 ophthalmology residents from July to August 2022 and then again April to June 2023.

Results Twenty-six PDs completed the survey (response rate 20.3% out of 128 PDs). Forty-one PGY-2 ophthalmology residents who underwent the combined ophthalmology PGY-1 year and 33 PGY-3 ophthalmology residents also completed the survey. Most PGY-1 curricula focused on exposure to comprehensive ophthalmology and provided indirect ophthalmoscope, slit lamp, and refraction skills training to residents. Early exposure to fundamentals and clinical workflows were commonly cited benefits to the integration. When PDs were surveyed about how well-prepared PGY-1 residents who went through the combined year are for the PGY-2 relative to the prior year's class, 16 (61.5%) responded “better prepared.” PGY-2 residents also reported a relatively higher level of clinical preparedness and familiarity with ophthalmology co-residents than PGY-3 residents. Several areas of improvement cited by both PDs and residents were identified including a dedicated didactic curriculum and more time in ophthalmology during the PGY-1 year.

Conclusions We found an overall net benefit from the integration of the combined ophthalmology PGY-1 year. Benefits include early exposure to clinical skills and knowledge specific to ophthalmology, leading to increased confidence and preparedness for the rigorous transition to ophthalmology residency. We also identified many areas for improvement to optimize the PGY-1 year including a formal curriculum and additional time in ophthalmology. Programs should work closely with their residents, faculty, and non-ophthalmology PDs to refine the PGY-1 for the benefit of future ophthalmologists.
Improved Performance of ChatGPT-4 on the OKAP Examination: A Comparative Study with ChatGPT-3.5
Authors: Teebagy Sean , Colwell Lauren , Wood Emma , Yaghy Antonio , Faustina Misha
Published: September 2023

Introduction: This study aims to evaluate the performance of ChatGPT-4, an advanced artificial intelligence (AI) language model, on the Ophthalmology Knowledge Assessment Program (OKAP) examination compared to its predecessor, ChatGPT-3.5.

Methods: Both models were tested on 180 OKAP practice questions covering various ophthalmology subject categories.

Results: ChatGPT-4 significantly outperformed ChatGPT-3.5 (81% vs. 57%; p<0.001), indicating improvements in medical knowledge assessment.

Discussion: The superior performance of ChatGPT-4 suggests potential applicability in ophthalmologic education and clinical decision support systems. Future research should focus on refining AI models, ensuring a balanced representation of fundamental and specialized knowledge, and determining the optimal method of integrating AI into medical education and practice.
Trust across borders: a review of the research on interorganizational trust in international business
Authors: Zou Tengjian , Ertug Gokhan , Cuypers Ilya R. P. , Ferrin Donald L.
Published: September 2023

Trust between organizations has been recognized as crucial in international business (IB) and has attracted extensive research attention. Researchers have conceptualized and measured interorganizational trust in multiple ways, investigated numerous determinants and outcomes of interorganizational trust, and explored interorganizational trust in several types of international relationships across a range of country combinations using varied research methodologies. Our review aims to consolidate and advance this literature by focusing on (i) how interorganizational trust has been conceptualized in IB; (ii) how interorganizational trust has been operationalized in IB; (iii) what factors promote or hinder interorganizational trust in IB; (iv) what the outcomes are of interorganizational trust in IB; and (v) how interorganizational trust has been studied in IB. For each question, we analyze the literature and then provide recommendations and directions for future research. We aim to provide a solid grounding for future research that will keep this area theoretically sound, empirically robust, and phenomenologically relevant.
Existence theorems for a generalized Chern–Simons equation on finite graphs
Authors: Gao Jia , Hou Songbo
Published: September 2023

Consider G = (V, E) as a finite graph, where V and E correspond to the vertices and edges, respectively. We study a generalized Chern–Simons equation Δu=λeu(ebu−1)+4π∑j=1Nδpj on G, where λ and b are positive constants; N is a positive integer; p1, p2, …, pN are distinct vertices of V; and δpj is the Dirac delta mass at pj. We prove that there exists a critical value λc such that the equation has a solution if λ ≥ λc and the equation has no solution if λ < λc. We also prove that if λ > λc, the equation has at least two solutions that include a local minimizer for the corresponding functional and a mountain-pass type solution. Our results extend and complete those of Huang et al. [Commun. Math. Phys. 377(1), 613–621 (2020)] and Hou and Sun [Calculus Var. Partial Differ. Equations 61(4), 139 (2022)].
Surface electromyography using dry polymeric electrodes
Authors: Steenbergen Nicolas , Busha Ivan , Morgan Alexis , Mattathil Collin , Levy Pinto Arieh , Spyridakos Fotios , Sokolovskiy Ivan , Tahirbegi Bogachan , Chapman Christopher , Cuttaz Estelle , Litvinova Karina , Goding Josef , Green Rylie
Published: September 2023

Conventional wet Ag/AgCl electrodes are widely used in electrocardiography, electromyography (EMG), and electroencephalography (EEG) and are considered the gold standard for biopotential measurements. However, these electrodes require substantial skin preparation, are single use, and cannot be used for continuous monitoring (>24 h). For these reasons, dry electrodes are preferable during surface electromyography (sEMG) due to their convenience, durability, and longevity. Dry conductive elastomers (CEs) combine conductivity, flexibility, and stretchability. In this study, CEs combining poly(3,4-ehtylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) in polyurethane are explored as dry, skin contacting EMG electrodes. This study compares these CE electrodes to commercial wet Ag/AgCl electrodes in five subjects, classifying four movements: open hand, fist, wrist extension, and wrist flexion. Classification accuracy is tested using a backpropagation artificial neural network. The control Ag/AgCl electrodes have a 98.7% classification accuracy, while the dry conductive elastomer electrodes have a classification accuracy of 99.5%. As a conclusion, PEDOT based dry CEs were shown to successfully function as on-skin electrodes for EMG recording, matching the performance of Ag/AgCl electrodes, while addressing the need for minimal skin prep, no gel, and wearable technology.
Self-adapting infectious dynamics on random networks
Authors: Clauß Konstantin , Kuehn Christian
Published: September 2023

Self-adaptive dynamics occurs in many fields of research, such as socio-economics, neuroscience, or biophysics. We consider a self-adaptive modeling approach, where adaptation takes place within a set of strategies based on the history of the state of the system. This leads to piecewise deterministic Markovian dynamics coupled to a non-Markovian adaptive mechanism. We apply this framework to basic epidemic models (SIS, SIR) on random networks. We consider a co-evolutionary dynamical network where node-states change through the epidemics and network topology changes through the creation and deletion of edges. For a simple threshold base application of lockdown measures, we observe large regions in parameter space with oscillatory behavior, thereby exhibiting one of the most reduced mechanisms leading to oscillations. For the SIS epidemic model, we derive analytic expressions for the oscillation period from a pairwise closed model, which is validated with numerical simulations for random uniform networks. Furthermore, the basic reproduction number fluctuates around one indicating a connection to self-organized criticality.
Velocity-space sensitivity and inversions of synthetic ion cyclotron emission
Authors: Schmidt B. S. , Salewski M. , Reman B. C. G. , Dendy R. O. , Dong Y. , Järleblad H. , Moseev D. , Ochoukov R. , Rud M. , Valentini A.
Published: September 2023

This paper introduces a new model to find the velocity-space location of energetic ions generating ion cyclotron emission (ICE) in plasmas. ICE is thought to be generated due to inverted gradients in the v⊥ direction of the velocity distribution function or due to anisotropies, i.e., strong gradients in the pitch direction. Here, we invert synthetic ICE spectra generated from first principles PIC-hybrid computations to find the locations of these ICE-generating ions in velocity space in terms of a probability distribution function. To this end, we compute 2D ICE weight functions based on the magnetoacoustic cyclotron instability, which reveals the velocity-space sensitivity of ICE measurements. As an example, we analyze the velocity-space sensitivity of synthetic ICE measurements near the first 15 harmonics for plasma parameters typical for the Large Helical Device. Furthermore, we investigate the applicability of a least-square subset search, Tikhonov regularization, and Lasso regularization to obtain the locations in velocity space of the ions generating the ICE.
Chaotic finite difference operators
Authors: Murillo-Arcila Marina , Peris Alfred , Vargas Álvaro
Published: September 2023

In this article, we analyze the chaotic behavior of finite difference operators associated with certain differential equations. Our examples range from numerical schemes for a birth-and-death model with proliferation to a class of second-order partial differential equations that includes the hyperbolic heat transfer equation, the telegraph equation, and the wave equation. We provide sufficient conditions on the spatial and time steps of the scheme that guarantee chaos for the corresponding operators, and we compare them with the conditions needed to ensure chaotic analytical solutions.
Radiation tolerance and self-healing in triple halide perovskite solar cells
Authors: Afshari Hadi , Chacon Sergio A. , Sourabh Shashi , Byers Todd A. , Whiteside Vincent R. , Crawford Rose , Rout Bibhudutta , Eperon Giles E. , Sellers Ian R.
Published: September 2023

The high tolerance and stability of triple halide perovskite solar cells is demonstrated in practical space conditions at high irradiation levels. The solar cells were irradiated for a range of proton energies (75 keV, 300 keV, and 1 MeV) and fluences (up to 4 × 1014 p/cm2). The fluences of the energy proton irradiations were varied to induce the same amount of vacancies in the absorber layer due to non-ionizing nuclear energy loss (predominant at <300 keV) and electron ionization loss (predominant at >300 keV). While proton irradiation of the solar cells initially resulted in degradation of the photovoltaic parameters, self-healing was observed after two months where the performance of the devices was shown to return to their pristine operation levels. Their ability to recover upon radiation exposure supports the practical potential of perovskite solar cells for next-generation space missions.
Development and testing of secondary ion accelerator for ITER neutral particle diagnostic system
Authors: Afanasyev V. I. , Chernyshev F. V. , Kozlovsky S. S. , Melnik A. D. , Mironov M. I. , Mokeev A. N. , Navolotsky A. S. , Nesenevich V. G. , Petrov M. P. , Petrov S. Ya
Published: September 2023

This paper presents the results of the development and testing of a secondary ion accelerator for the diagnostic complex of neutral particle analyzers at ITER. The accelerator is part of an analyzer designed to measure fluxes of neutral deuterium and tritium particles escaping from reactor plasma in a total range of 10–200 keV. The aim of the accelerator is to improve the signal/background ratio of the analyzer. It is especially important for the region with a relatively low energy of 10–50 keV. The accelerator has the function of converting atoms into secondary ions and accelerating them in an electrostatic field with a voltage of up to +100 kV. The accelerator is based on two high-voltage accelerating tubes. A special unit is built into the central electrode of the accelerator, which provides the replacement of stripping foils used for the conversion of the flux of neutral particles into a flux of secondary ions. The high-voltage tube assembly is encompassed by a sealed steel housing, in which electrical insulation is provided by a gas gap (nitrogen at 6 bar). The results of tests of the accelerator under ITER relevant conditions, namely, under high-intensity gamma irradiation and seismic loads, have shown its high reliability for use in the diagnostic complex of the fusion reactor.
A high-bandwidth voltage amplifier for driving piezoelectric actuators in high-speed atomic force microscopy
Authors: Andany Santiago H. , Nievergelt Adrian P. , Kangül Mustafa , Ziegler Dominik , Fantner Georg E.
Published: September 2023

High-speed atomic force microscopy (HS-AFM) is a technique capable of revealing the dynamics of biomolecules and living organisms at the nanoscale with a remarkable temporal resolution. The phase delay in the feedback loop dictates the achievable speed of HS-AFM instruments that rely on fast nanopositioners operated predominantly in conjunction with piezoelectric actuators (PEAs). The high capacitance and high operating voltage of PEAs make them difficult to drive. The limited bandwidth of associated high-voltage piezo-amplifiers is one of the bottlenecks to higher scan speeds. In this study, we report a high-voltage, wideband voltage amplifier comprised of a separate amplification and novel voltage-follower power stage, requiring no global feedback. The reported amplifier can deliver a current over ±2 amps, offers a small-signal bandwidth of 1 MHz, and exhibits an exceptionally low phase lag, making it particularly well suited for the needs of next-generation HS-AFMs. We demonstrate its capabilities by reporting its achievable bandwidth under various PEA loads and showcasing its merit for HS-AFM by imaging tubulin protofilament dynamics at sub-second frame rates.
Effect of surface roughness on phase transition timing in megaampere pulsed-power–driven exploding conductors
Authors: Carrier Matthew J. , Farmer William A. , Klemmer Aidan W. , Kreher Seth E. , Bauer Bruno S. , Srinivasan Bhuvana
Published: September 2023

An understanding of material phase transitions in megaampere pulsed-power–driven exploding conductors is important for predicting the growth of hydrodynamic instabilities in magneto-inertial fusion concepts. This study analyzes phase transitions in electrical conductor explosions using 1D Lagrangian and 2D arbitrary Lagrangian–Eulerian resistive magnetohydrodynamic simulations to show that micrometer-scale surface roughness can lead to the electrothermal instability (ETI), a feedback effect that concentrates resistive heating and leads to early melting and ablation. Simulations of the Mykonos electrothermal instability II (METI-II) experiment show melting begins 19% sooner for machined rods with micrometer-scale surface roughness than for rods without these features. The surface magnetic field is 41 T around the initial region of melt, representing a lower magnitude than both the 86 T from 1D simulations and the 85 T threshold reported elsewhere. In 2D simulations with micrometer-scale surface roughness, temperature measurements indicate the critical point temperature of aluminum is reached 17% faster in comparison with 1D simulations. Values from 2D simulations with surface roughness align with predictions from ETI theory, and the observed temperature redistribution further supports the ETI as an underlying mechanism. Simulation results are validated against experimental photonic Doppler velocimetry data. This study shows 1D simulations are adequate to model conductors with sub-micrometer-scale surface roughness in this high-energy-density regime; however, 2D or 3D simulations are required to capture the full range of physics for accurately describing phase transitions in conductors with micrometer-scale or larger surface roughness.
A double-cycle echo state network topology for time series prediction
Authors: Fu Jun , Li Guangli , Tang Jianfeng , Xia Lei , Wang Lidan , Duan Shukai
Published: September 2023

Echo state network (ESN) has gained wide acceptance in the field of time series prediction, relying on sufficiently complex reservoir connections to remember the historical features of the data and using these features to obtain the outputs by a simple linear readout. However, the randomness of its input and reservoir connections pose negative impacts on the prediction performance and performance stability of the models, the complexity of reservoir connections brings high time consumption during network computing, and the presence of randomness and complexity makes the hardware implementation of the ESN difficult. In response, we propose a double-cycle ESN (DCESN) based on the Li-ESN model, which has fixed weights to improve prediction performance and performance stability and simpler reservoir connections compared to the classical ESN to reduce the time consumption. The existence of both greatly reduces the difficulty of hardware implementation of the ESN and provides many conveniences for the future application of the ESN. Experimental results on many widely used time series datasets show that the DCESN has comparable or even better prediction performance than the ESN and good robustness against noise and parameter fluctuations.
Spin dynamics and chirality induced spin selectivity
Authors: Hedegård Per
Published: September 2023

By now, it is well known that chiral molecules can affect the spin of electrons passing through. In addition, the magnetization of, e.g., nanomagnets covered by chiral molecules can be affected by the presence of molecules. We are studying the mechanisms that explain various observations involving combinations of magnets and chiral molecules. We find that there exists a molecule induced contribution to the magnetic anisotropy of the magnets. Out of equilibrium, when electrons are actually being transported through a nano-magnet covered with chiral molecules, a molecule induced torque acting on the magnetization is emerging. It is of the spin-transfer-torque kind, already discussed in other parts of spintronics. This current induced torque can help explain the observed breaking of the Onsager reciprocity principle in experiments involving magnets and chiral molecules.
Modeling the relationship between mechanical yield stress and material geometry using convolutional neural networks
Authors: Najafi Fahimeh , Sveinsson Henrik Andersen , Dreierstad Christer , Glad Hans Erlend Bakken , Malthe-Sørenssen Anders
Published: September 2023

Machine learning methods can be used to predict the properties of materials from their structure. This can be particularly useful in cases where other standard methods for finding material properties are time and resources consuming to use on large sample spaces. In this work, we study the strength of α-quartz crystals with a porous layer created by simplex noise as the shape of porosity. We train a neural network to predict the yield stress of these systems under both shear and tensile deformation. Molecular dynamics simulations are used for a randomly selected sample of possible structures in order to generate the ground truth to be used as the training data. We employ deep convolutional neural networks (CNNs) which are commonly used when dealing with image or image-like data since the input data for the problem in hand are a binary 2D structure of the porous layer of the systems. The trained CNN can predict the yield stress of a system based on the geometry of that given system, with much higher precision compared to a baseline polynomial regression method. Saliency maps created with the trained model show that the model predictions are most sensitive to altering structures near high-stress regions, indicating that the model makes predictions based on reasonable physics.
Study on bandgap characteristics and vibration attenuation mechanism of double-oscillator power-exponent prism phononic crystal plate
Authors: Zhang Zhan , Zhang Zhenhua , Jin Xing
Published: September 2023

This study introduces a local resonance mechanism to a periodic acoustic black hole (ABH) structure to achieve vibration control of plate structures and proposes a double-oscillator power-exponent prism phononic crystal. Results show that the periodic power-exponent prism can generate a high-frequency bandgap, the interior oscillator can generate a low-frequency bandgap, and the top oscillator can separate the frequency dispersion curve at around 700 Hz to form a bandgap with a width of 189 Hz. The double-oscillator power-exponent prism phononic crystal, composed of two types of oscillators and a power-exponent prism, can simultaneously have high-, middle-, and low-frequency bandgaps. Simulations and experiments show that it has a good attenuation effect on flexural vibration in the bandgap frequency band. The present results can provide a useful reference for bandgap design based on the combination of multiple mechanisms.
Laser-induced coherent longitudinal acoustics phonons in thin films observed by ultrafast optical reflectivity and ultrafast x-ray diffraction
Authors: Yu Junxiao , Zhang Haijuan , Lv Zefang , Chen Conglong , Li Runze , Zhai Xiaofang , Chen Jie , Rentzepis Peter M.
Published: September 2023

Femtosecond laser excitation of crystal materials can produce coherent longitudinal acoustic phonons (CLAPs), which possess the capability to interact with various quasiparticles and influence their dynamics. The manipulation of CLAPs' behavior is thus of significant interest for potential applications, particularly in achieving ultrafast modulations of material properties. In this study, we present our findings on the propagation of laser-induced CLAPs at thin-film interfaces and heterojunctions using ultrafast optical reflectivity and ultrafast x-ray diffraction measurements. We observe that CLAPs can efficiently propagate from a LaMnO3 thin-film to its SrTiO3 substrate due to the matching of their acoustic impedance, and the oscillation period increases from 54 to 105 GHz. In contrast, in ultrafast x-ray diffraction experiments, we discover that CLAPs are partially confined within an Au (111) thin film due to the mismatch of acoustic impedance with the substrates, leading to an oscillation period of 122 ps. However, interestingly, when examining La0.7Ca0.175Sr0.125MnO3/Ba0.5Sr0.5TiO3 bilayers, no oscillations are observed due to the favorable impedance matching between the layers. Our findings demonstrate that acoustic impedance can serve as an effective means to control coherent phonons in nanometer-thin films and may also play a crucial role in phonon engineering at interfaces or heterostructures.
Quantitative identification of daily mental fatigue levels based on multimodal parameters
Authors: Chen Ruijuan , Wang Rui , Fei Jieying , Huang Lengjie , Wang Jinhai
Published: September 2023

Fatigue has become an important health problem in modern life; excessive mental fatigue may induce various cardiovascular diseases. Most current mental fatigue recognition is based only on specific scenarios and tasks. To improve the accuracy of daily mental fatigue recognition, this paper proposes a multimodal fatigue grading method that combines three signals of electrocardiogram (ECG), photoplethysmography (PPG), and blood pressure (BP). We collected ECG, PPG, and BP from 22 subjects during three time periods: morning, afternoon, and evening. Based on these three signals, 56 characteristic parameters were extracted from multiple dimensions, which comprehensively covered the physiological information in different fatigue states. The extracted parameters were compared with the feature optimization ability of recursive feature elimination (RFE), maximal information coefficient, and joint mutual information, and the optimum feature matrix selected was input into random forest (RF) for a three-level classification. The results showed that the accuracy of classification of fatigue using only one physiological feature was 88.88%, 92.72% using a combination of two physiological features, and 94.87% using all three physiological features. This study indicates that the fusion of multiple physiological traits contains more comprehensive information and better identifies the level of mental fatigue, and the RFE-RF model performs best in fatigue identification. The BP variability index is useful for fatigue classification.
Polyzwitterion fast and slow mode behavior are coupled to phase separation as observed by dynamic laser light scattering
Authors: Pickett Phillip D. , Ma Yuanchi , Prabhu Vivek M.
Published: September 2023

A model zwitterionic polysulfobetaine, poly(3-(acrylamidopropyl-dimethyl-ammonium) propyl-1-sulfonate) (pAPAPS), phase separates upon cooling and exhibits an upper critical solution temperature (UCST) behavior with no added salt in deuterium oxide solutions. Dynamic light scattering measurements indicate the presence of distinct fast and slow diffusive modes, where the fast mode is interpreted as a collective diffusion coefficient and the slow mode is attributed to the diffusion of multi-chain dynamic clusters. The relative population of fast and slow modes varies systematically with temperature and concentration. A clustering temperature (T*) was assigned when the slow mode first appeared upon cooling. The slow mode then increases in relative scattering amplitude as the phase boundary is approached. The fast mode exhibits a concentration dependence above T* consistent with the virial expansion in the collective diffusion. The sign of the virial coefficient (kd) is negative, even in the good solvent region above the expected Flory temperature (Θ ≈ 39 °C), a behavior distinct from synthetic neutral polymers in organic solvents. The onset of multi-chain clustering at T < T* coincides with the poor solvent regime (T < Θ). Attractive dipolar interactions due to the zwitterionic sulfobetaine groups in pAPAPS are suggested as the origin of the multi-chain clusters with no salt. Upon the addition of 100 mM NaCl, the slow mode is suppressed, and the hydrodynamic radius is consistent with polyzwitterion chain dimensions in a dilute solution. We find that concentration dependent diffusion is highly linked to the theta temperature and the emergence of dynamic clusters as the polymer goes from good to poor solvent on approach to the UCST. The slow mode in the semidilute regime is reported along with preliminary small-angle neutron scattering data that show salt reduces clustering and leads to predominantly chain scattering.
Optical properties of ScN layers grown on Al2O3(0001) by plasma-assisted molecular beam epitaxy
Authors: Dinh Duc V. , Peiris Frank , Lähnemann Jonas , Brandt Oliver
Published: September 2023

Accurate knowledge of optical constants (refractive index n and extinction coefficient k) of ScN is crucial for understanding optical properties of this binary nitride semiconductor as well as for its use in optoelectronic applications. Using spectroscopic ellipsometry in a spectral range from far infrared to far ultraviolet (0.045–8.5 eV), we determine n and k of ScN layers grown on Al2O3(0001) substrates by plasma-assisted molecular beam epitaxy. Fits of ellipsometry data return the energies of four oscillators representing critical points in the band structure of ScN, namely, 2.03, 3.89, 5.33, and 6.95 eV. As the infrared range is dominated by free carriers, the vibrational properties of the layers are examined by Raman spectroscopy. Despite the rock salt structure of ScN, several first-order phonon modes are observed, suggesting a high density of point defects consistent with the high electron density deduced from Hall measurements. Finally, photoluminescence measurements reveal an emission band slightly above the lowest direct bandgap. We attribute the redshift of the peak emission energy from 2.3 to 2.2 eV with increasing layer thickness to a reduction in the O concentration in the layers.
Tunable IR perfect absorbers enabled by tungsten doped VO2 thin films
Authors: Larciprete Maria Cristina , Ceneda Daniele , Scirè Daniele , Mosca Mauro , Persano Adorno Dominique , Dereshgi Sina Abedini , Macaluso Roberto , Li Voti Roberto , Sibilia Concita , Cesca Tiziana , Mattei Giovanni , Aydin Koray , Centini Marco
Published: September 2023

The temperature tunability of complex dielectric constants of vanadium dioxide (VO2) makes it a promising phase-change material for use in active, dynamic, tunable photonics applications. Specifically, the semiconductor-to-metal phase transition in VO2 enables reversible, broadband, and large complex refractive index variation and paves the way for a plethora of applications. Although the critical temperature for phase-transition is 68 °C for VO2 films, its transition temperature can be reduced to room temperature by tungsten-doping of vanadium dioxide. Such a degree of freedom in controlling the critical temperature through tungsten doping provides further tunability of the thermochromic behavior. In this work, we investigate a variety of W-doped VO2 thin films deposited by laser ablation of targets with increasing W doping content and report detailed infrared characterization together with numerical simulations. Our experimental results indicate that the perfect absorption can be achieved at different temperatures, within the VO2 insulator-to-metal phase transition process, as a function of W doping content. Tunable subwavelength layers allow perfect absorption under different temperature conditions around λ = 12 µm. We show that a high dynamic range of reflectivity can be achieved when the temperature is increased above the phase transition temperature. Furthermore, we observe perfect absorption at 11.8 µm at room temperature for a W content of 0.75%. We believe that W-doped VO2 thin films with tunable and controllable perfect absorption will open the way for a class of promising thermo-optical devices including thermos-photovoltaics, infrared filters, radiative cooling devices, and thermal emitters.
An asymmetric probability density function
Authors: Chen W.
Published: September 2023

A probability density or distribution function of turbulence has been thought to be symmetric due to the symmetry of the partial differential equations from the first principles. However, the experimental data have been shown otherwise by a so-called Taylor correlation function, and this is an unresolved issue. A recent study shows that this probability density function can be asymmetric analytically by introducing negative eigenvalues. Here, in this work, we show the mathematical basis for this asymmetry, although the partial differential equations follow the symmetry of the Lie groups. We also demonstrate a complete solution of partial differential equations, including the exponential terms and negative eigenvalues, which plays a vital part in transient phenomena. Our analysis shows that the asymmetry is from the partition of velocities of the same or opposing direction, not from the negative eigenvalues. Fundamentally, the loss of rotational symmetry is caused by the exponential terms for the transient solution, which we demonstrate by the derivation of the complete solution. The new correlation produces excellent agreement with the experimental data. The universality and limitations of the correlation function are discussed, and through the parameter study, the variations and statistical nature of the probability function are clarified. The asymmetry probability function should have wider applicability than the symmetric Gaussian distribution, which is the special case of the asymmetry probability function.
Perspectives on superhydrophobic surface durability
Authors: Hoque Muhammad Jahidul , Ma Jingcheng , Rabbi Kazi Fazle , Yan Xiao , Singh Bakhshish Preet , Upot Nithin Vinod , Fu Wuchen , Kohler Johannes , Thukral Tarandeep Singh , Dewanjee Sujan , Miljkovic Nenad
Published: September 2023

Superhydrophobicity is a remarkable adaptation observed in various natural surfaces, which can potentially play a crucial role in the efficient functioning of numerous applications. The attainment of long-lasting or “durable” superhydrophobicity has significant implications for global energy production, water conservation, and the overall carbon footprint of industrialized and developing nations. Many applications requiring superhydrophobicity have been limited to laboratory scale experiments due to poor durability. In this article, we discuss important recent advancements and challenges to the development of durable superhydrophobic surfaces, including scalable fabrication, efficacy with low surface tension fluids, and the absence of standardized durability testing methods. To help address these challenges that hinder the implementation of superhydrophobicity, we conclude the article by providing a roadmap that outlines the crucial areas where the community should focus its research and development efforts, both from a fundamental and applied perspective.
Strongly correlated antiferromagnetic vanadates
Authors: Hu L. , Zhu X. B. , Sun Y. P.
Published: September 2023

Antiferromagnetic (AFM) materials have zero net magnetic moments due to the alignment of adjacent magnetic moments antiparallel to each other, which have drawn extensive interest in the field of next generation spintronics, thanks to the merits of negligible stray fields, fast spin dynamics, and robustness against magnetic disturbances. In the past decades, the strongly correlated vanadates of VO2, V2O3, and RVO3 have extensively been studied because of noteworthy metal–insulator transitions. Nevertheless, the magnetism (especially antiferromagnetism) in the vanadates has attracted less attention. This Perspective provides a brief overview of the strongly correlated AFM vanadates. First, an introduction to the basic concept of antiferromagnetism and vanadates is presented. Then, the antiferromagnetism in vanadates containing V4+ (VO2, NaV2O5, and Sr2VO4), V3+ (V2O3, RVO3, AV2O4, and VOCl), and V2+ (VO) with different spin moments is presented. Finally, a summary and outlook with respect to the antiferromagnetism in vanadates are included.
Identification of wave breaking from nearshore wave-by-wave records
Authors: Holand K. , Kalisch H. , Bjørnestad M. , Streßer M. , Buckley M. , Horstmann J. , Roeber V. , Carrasco-Alvarez R. , Cysewski M. , Frøysa H. G.
Published: September 2023

Using data from a recent field campaign, we evaluate several breaking criteria with the goal of assessing the accuracy of these criteria in wave breaking detection. Two new criteria are also evaluated. An integral parameter is defined in terms of temporal wave trough area, and a differential parameter is defined in terms of maximum steepness of the crest front period. The criteria tested here are based solely on sea surface elevation derived from standard pressure gauge records. They identify breaking and non-breaking waves with an accuracy between 84% and 89% based on the examined field data.
Thermodynamic calculations using reverse Monte Carlo: Simultaneously tuning multiple short-range order parameters for 2D lattice adsorption problem
Authors: Haque Suhail , Chatterjee Abhijit
Published: September 2023

Lattice simulations are an important class of problems in crystalline solids, surface science, alloys, adsorption, absorption, separation, catalysis, to name a few. We describe a fast computational method for performing lattice thermodynamic calculations that is based on the use of the reverse Monte Carlo (RMC) technique and multiple short-range order (SRO) parameters. The approach is comparable in accuracy to the Metropolis Monte Carlo (MC) method. The equilibrium configuration is determined in 5–10 Newton–Raphson iterations by solving a system of coupled nonlinear algebraic SRO growth rate equations. This makes the RMC-based method computationally more efficient than MC, given that MC typically requires sampling of millions of configurations. The technique is applied to the interacting 2D adsorption problem. Unlike grand canonical MC, RMC is found to be adept at tackling geometric frustration, as it is able to quickly and correctly provide the ordered c(2 × 2) adlayer configuration for Cl adsorbed on a Cu (100) surface.
Three-tone coherent microwave electromechanical measurement of a superfluid Helmholtz resonator
Authors: Spence S. , Varga E. , Potts C. A. , Davis J. P.
Published: September 2023

We demonstrate electromechanical coupling between a superfluid mechanical mode and a microwave mode formed by a patterned microfluidic chip and a 3D cavity. The electric field of the chip-cavity microwave resonator can be used to both drive and detect the motion of a pure superflow Helmholtz mode, which is dictated by geometric confinement. The coupling is characterized using a coherent measurement technique developed for measuring weak couplings deep in the sideband unresolved regime. The technique is based on two-probe optomechanically induced transparency/amplification using amplitude modulation. Instead of measuring two probe tones separately, they are interfered to retain only a signal coherent with the mechanical motion. With this method, we measure a vacuum electromechanical coupling strength of g0=2π×23.3 μ Hz, three orders of magnitude larger than previous superfluid electromechanical experiments.
Achiral dipoles on a ferromagnet can affect its magnetization direction
Authors: Alhyder Ragheed , Cappellaro Alberto , Lemeshko Mikhail , Volosniev Artem G.
Published: September 2023

We demonstrate the possibility of a coupling between the magnetization direction of a ferromagnet and the tilting angle of adsorbed achiral molecules. To illustrate the mechanism of the coupling, we analyze a minimal Stoner model that includes Rashba spin–orbit coupling due to the electric field on the surface of the ferromagnet. The proposed mechanism allows us to study magnetic anisotropy of the system with an extended Stoner–Wohlfarth model and argue that adsorbed achiral molecules can change magnetocrystalline anisotropy of the substrate. Our research aims to motivate further experimental studies of the current-free chirality induced spin selectivity effect involving both enantiomers.
Reducing the condensing flow effects on the steam turbine blades through modified design geometry
Authors: Hosseini Seyed Ali , Nakisa Mehdi , Lakzian Esmail
Published: September 2023

Nowadays, a large part of energy is provided by steam turbines; thus, increasing the efficiency and improving the steam turbines performance are of special importance. The presence of the liquid phase in the low-pressure stage of the steam turbine can cause energy loss, efficiency drop, and erosion/corrosion problems; therefore, one of the essential issues is to identify wet steam flow and try to reduce condensation loss. In order to decrease the liquid fraction, the drainage groove technique can be applied. The drainage groove sucks the water droplets from the turbine blade surface and drains them into the condenser. In this study, the effect of the drainage groove location on the surface of steam turbine blades has been investigated on the condensation, droplet radius, inlet mass flow, erosion rate, liquid drainage ratio, condensation losses, and total drainage ratio. For modeling the condensing flow, the Eulerian–Eulerian approach has been applied. The results show that the location of the drainage groove affects the groove performance and flow pattern in the turbine blade. In the selected drainage, the liquid drainage ratio, condensation losses, and erosion rate are reduced by 7.6%, 12%, and 88%, respectively, compared with the no-drainage groove case. Also, the total drainage ratio is 7.2% in the selected drainage. The outcomes of the present work have been a major step forward in the techniques having a great influence on the lifetime, repair and maintenance, and the output power of steam power generation facilities.
Extraction and characteristic analysis of the nonlinear acoustic impedance of circular orifices
Authors: Han Kangjian , Ji Zhenlin , Fan Yiliang
Published: September 2023

For investigating the nonlinear acoustic behavior of circular orifices under high amplitude sound excitation, an approach based on the three-dimensional time-domain computational fluid dynamics simulation is proposed to extract the nonlinear acoustic impedance of circular orifices. By solving laminar flow equations, the propagation of the acoustic signal in the vicinity of orifice is simulated, and the effect of the interaction among adjacent orifices is considered by using the lateral periodic boundary condition. The effects of diameter, thickness, and porosity on acoustic impedance under different amplitude sound excitations are studied. By using nonlinear regression analysis of the dimensionless parameters composed of particle velocity amplitude, frequency, and geometric parameters, fitting formulas of nonlinear acoustic impedance of circular orifices are presented. As an application of engineering computation, transmission loss of perforated silencers under low and high amplitude sound excitations is predicted by using the present acoustic impedance fitting formulas and via the finite element computation. By comparing the predicted and measured results, the accuracy and practicability of fitting formulas of nonlinear acoustic impedance of circular orifices are validated.
Bulk photovoltaic and photoconductivity effects in two-dimensional ferroelectric CuInP2S6 based heterojunctions
Authors: Qiu Dan , Hou Pengfei , Wang Jinbin , Ouyang Xiaoping
Published: September 2023

The construction of two-dimensional heterojunctions has significantly expanded the modulation degrees of freedom in two-dimensional materials, which has led to the emergence of numerous advanced microelectronics and optoelectronic devices. Extensive research has been conducted on the photovoltaic and photoconductivity effects to achieve higher photodetection performance in heterojunction-based devices. However, the bulk photovoltaic effect, which has excellent potential for applications in self-powered optoelectronics, microelectronics, and energy conversion devices, has not received enough attention. Herein, we construct a two-dimensional ferroelectric heterojunction using multi-layered CuInP2S6 (CIPS) and MoS2 nanoflakes and investigate its photoconductivity effect for photodetection. Furthermore, we observe and analyze the bulk photovoltaic effect in the heterojunction. The photoelectric effect in the MoS2 layer contributes to the photoconductivity effect of the heterojunction, while the room-temperature polar ordering in CIPS contributes to the bulk photovoltaic effect. The heterojunction exhibits high specific detectivity (D*) of 1.89 × 109 Jones, when the optical power intensity is 4.71 mW/cm2. Moreover, the short-circuit photocurrent density is high, reaching about 1.23 mA/cm2 when the optical power intensity is 0.35 W/cm2. This work highlights the potential application of two-dimensional ferroelectric materials in multifunction devices with self-powered detection and energy conversion capabilities.
Study of flow separation control by bleed slot and bleed holes in a transonic compressor cascade
Authors: Li Bai , Mu Guangyuang , Luo Lei , Du Wei , Zhou Xun
Published: September 2023

An extensive numerical investigation is carried out to study the effects of single-slot bleed and porous bleed on the flow separation control in a transonic compressor stator. Two single slots in different locations and three staggered rows of circular holes are placed on the suction surface. Five bleed pressure ratios are examined for each bleed scheme at the design inlet Mach number of 1.0. The numerical results show that the porous bleed performs similar to the downstream slot bleed in terms of pressure loss control when the bleed pressure ratio is below 1.0. The maximum relative reduction in total pressure loss is 73%. The stable working range of downstream slot bleed is between 0.75 and 1.0 bleed pressure ratio, which is narrower than the range of porous bleed. The bleeding acceleration and favorable pressure gradients on the suction surface are key reasons for keeping the boundary layer from separating. The position of the aft edge of the bleed configuration is a critical parameter. It determines the ultimate range of adverse pressure gradients that the blade surface boundary layer needs to withstand. The similar performance of porous bleed and slot bleed is caused by their identical aft edge position. The high shock losses caused by a single shock wave result in a narrow stable working range for single-slot bleed. Multiple shocks and side bleeding in porous bleed mitigate the influences of shock wave losses and extend its working range.