bluuebunny/crossref_metadata_2025 huggingface dataset:
Early Renin Recovery After Adrenalectomy in Aldosterone-Producing
Adenomas: A Prospective Study
Authors: Mermejo Livia M. , Elias Paula C.L. , Molina Carlos A.F. , Tucci Silvio , Muglia Valdair F. , Elias Jorge , Antonini Sonir R. , de Castro Margaret , Moreira Ayrton C.
Published: April 2022

The aim of the study was to clarify the relationship and the time of aldosterone
and renin recoveries at immediate and long-term follow-up in
aldosterone-producing adenoma (APA) patients who underwent adrenalectomy.
Prospective and longitudinal protocol in a cohort of APA patients was followed
in a single center. Among 43 patients with primary aldosteronism (PA), thirteen
APA patients were enrolled in this study. Blood was collected for aldosterone,
renin, potassium, creatinine, cortisol, and ACTH before and 1, 3, 5, 7, 15, 30,
60, 90, 120, 180, 270, 360 days after adrenalectomy. At diagnosis, most patients
(84%) had hypokalemia and high median aldosterone levels (54.8;
24.0–103 ng/dl) that decreased to undetectable
(<2.2) or very low (<3.0) levels between fifth to seventh days
after surgery; then, between 3–12 months, its levels gradually increased
to the lower normal range. The suppressed renin (2.3;
2.3–2.3 mU/l) became detectable between the fifteen and
thirty days after surgery, remaining normal throughout the study. The
aldosterone took longer than renin to recover (60 vs.15 days; p<0.002)
and patients with higher aldosterone had later recovery (p=0.03). The
cortisol/ACTH levels remained normal despite the presence of a
post-operative hypoaldosteronism. Blood pressure and antihypertensive
requirement decreased after adrenalectomy. In conclusion, our prospective study
shows the borderline persistent post-operative hypoaldosteronism in the presence
of early renin recovery indicating incapability of the zona glomerulosa of the
remaining adrenal gland to produce aldosterone. These findings contribute to the
comprehension of differences in renin and aldosterone regulation in APA
patients, although both are part of the same interconnected system.
External and Middle Ear Trauma Resulting From Ear Impressions
Authors: Wynne Michael K. , Kahn Jonathan M. , Abel Debra J. , Allen Rose L.
Published: April 2022

When taking an impression of the external ear canal and ear, the audiologist is engaged in an invasive procedure whereby a foreign body is first placed into the ear canal and then removed. There is always an element of risk for significant medical problems when a clinician is performing an invasive procedure. Although some minor patient discomfort and, at times, some slight trauma to the ear canal occur when taking ear impressions, the incidence of significant trauma to the external or middle ear appears to be low. The purpose of this report is to provide some illustrative cases of significant external and middle ear trauma as a result of taking impressions of the external ear. Audiologists are advised to develop and implement an appropriate risk management program for taking ear impressions to reduce the potential risks associated with this procedure to their patients and to their practices.

Abbreviations: CIC = completely in the canal, HPD = hearing protection device, OR = operating room, PROS = pressure relief oto-dam system
Value-creation in the health data domain: a typology of what health data help us do
Authors: Fiske Amelia , Degelsegger-Márquez Alexander , Marsteurer Brigitte , Prainsack Barbara
Published: April 2022

It has become a trope to speak of the increasing value of health data in our societies. Such rhetoric is highly performative: it creates expectations, channels and justifies investments in data technologies and infrastructures, and portrays deliberations on political and legal issues as obstacles to the flow of data. Yet, important epistemic and political questions remain unexamined, such as how the value of data is created, what data journeys are envisioned by policies and regulation, and for whom data types are (intended to be) valuable. Drawing on two empirical cases, (a) interviews with physicians on the topic of digital selfcare, and (b) expectations of stakeholders on the use of Real-World Data in clinical trials, as well as existing literature, we propose a typology of what health data help us to do. This typology is intended to foster reflection about the different roles and values that data use unfolds. We conclude by discussing how regulation can better accommodate practices of valuation in the health data domain, with a particular focus on identifying regulatory challenges and opportunities for EU-level policy makers, and how Covid-19 has shed light on new aspects of each case.
Measuring legislative stability: a new approach with data from Hungary
Authors: Sebők Miklós , Kubik Bálint György , Molnár Csaba , Járay István Péter , Székely Anna
Published: April 2022

While the stability of legislation is one of the fundamental issues in political theory, comparative and quantitative analyses on the subject are in short supply in the political science literature. In this article, we propose a novel measurement scheme for legislative stability, and we also introduce a Legislative Stability Index (LSI) developed to this end. In terms of empirical evidence, our index relies on the number of legislative amendments adopted within the span of an electoral cycle, as well as the breadth of issues the amendments touch on. It is based on the frequency with which laws are amended after their adoption. Our approach uses a new law-amendment edge-type network for a new Hungarian legislative database. Amendment-type connections are discovered by an automated dictionary-based text mining method. We tested the applicability of our index in various regression models. Results show that the legislative term, the length of the law and the way it was adopted were the most significant variables in explaining variation in the stability of legislation.
Counterion atmosphere around DNA double helix: trapping of counterions at the nanoscale
Authors: Perepelytsya Sergiy , Zdorevskyi Oleksii
Published: April 2022

DNA is a strong polyelectrolyte macromolecule making metal ions (counterions) condense to a cloud around the double helix. The counterions may be localized outside the macromolecule and inside the minor and major grooves of the double helix. In the present work, the distribution of condensed counterions between inner and outer regions of DNA has been studied using the approaches of counterion condensation theory. The results have shown that the number of counterions trapped inside the macromolecule should be greater than 0.16 per one phosphate group. The maximal number of counterions that may be localized inside the DNA double helix is limited to about 0.4 per one phosphate group and it is much lower than the total number of condensed counterions. To analyze the structure of counterion cloud the molecular dynamics simulations of B-DNA with K+ counterions have been performed. The obtained number of the counterions trapped inside the grooves of the double helix is about 0.22 ± 0.06 per one phosphate group that agree with the model estimations. The developed model describes general features of the structure of counterion cloud around DNA and is able to predict the number of counterions inside the grooves of the double helix.
Low-temperature ferromagnetic resonance in bare and SiO2 coated La0.775Sr0.225MnO3 nanoparticles
Authors: Sova K. Yu. , Vakula A. S. , Kalmykova T. V. , Tarapov S. I. , Petrushenko S. I. , Belous A. G. , Solopan S. O.
Published: April 2022

La0.775Sr0.225MnO3 nanoparticles were synthesized by sol-gel method with heat treatment at T = 1073 K and covered with silica shells of various thicknesses. Analysis of their experimental ferromagnetic resonance spectra was carried out in the temperature range of 77–290 K. The linewidth of absorption curves change in a nonlinear manner in coated samples in the temperature range of 230 K ≤ T ≤ 290 K. Such changes indicate the appearance of external stresses between nanoparticles due to the difference in the thermal expansion coefficients of the two materials.
Thermochemical synthesis of graphite-like carbon nitride and its application
Authors: Danilov M. O. , Dovbeshko G. I. , Rusetskiy I. A. , Afonina U. K. , Byckov V. N. , Gnatyuk O. P. , Fomanyuk S. S. , Kolbasov G. Ya.
Published: April 2022

A thermochemical method has been applied and a new routine has been developed for the synthesis of a layered material from graphite-like carbon nitride (g-C3N4) using urea and melamine compounds. The production of the graphite-like carbon nitride has been proven by TEM, electron diffraction, x-ray diffraction, Raman spectroscopy, and elemental analysis. The electrochemical studies have shown that the obtained material can be a promising candidate for metal-free catalysts of oxygen electrodes for fuel cells and a base for the development of novel functional composite materials.
Controllable structures on the surface of natural polymers made by proton beam writing and femtosecond laser treatment
Authors: Kalinkevich O. V. , Polozhii H. Ye. , Kolinko S. V. , Zinchenko Ye. I. , Karpenko A. Yu. , Baturin V. A. , Ponomarev A. G. , Kalinkevich A. N. , Danilchenko S. N. , Daskalova A. , Angelova L. , Buchvarov I.
Published: April 2022

Microstructures with a given topology were created on the surface of pure chitosan films and the same films with nanometer Ti- and Zn-containing layers deposited by magnetron sputtering. These structures were obtained using two methods: proton lithography and femtosecond laser processing. The quality of the structures (the sharpness of the walls and the thickness of the channel) is comparable to the quality of the structures obtained in the classical synthetic resist for proton lithography (polymethylmethacrylate, PMMA). A thin metal layer on the surface of the biopolymer matrix (resist) does not interfere with the formation of structures by the proton beam writing method. Laser treatment allows us to create repeating structures that control the biocompatibility of the treated surface.
Domains of the adsorbed benzene monolayer on graphene
Authors: Lykah V. A. , Syrkin E. S.
Published: April 2022

We consider the adsorbed benzene monolayer on graphene and show that the monolayer’s structure can be very complicated even for benzene, the simplest representative of the cyclic hydrocarbons. We base this on previous the first principal investigations, which found different energy states of the adsorbed benzene molecule. We find the existence of the six domains (star domains) for the stable molecular monolayer. The representatives of these domains (grains) at the graphene hexagonal layer are star vectors that describe transitions from symmetric high energy state into the stable low symmetric position. In the hexagon lattice of any benzene close pack domain, we introduce the primitive unit vectors, which are twice longer than the graphene primitive unit ones. The symmetry elements of the adsorbed benzene monolayer on graphene are found, left and right domains are introduced. Besides, half-translation of the benzene domains on the graphene primitive unit vectors leads to a further increase in the variety of the domain types. We introduce the selection procedure to decrease the number of the possible domains, find zero-block cells, and the complete number of the benzene domains — eight. We find all types of the structural domains and show their relation with the graphene unit cell construction.
Nondestructive characterization of aluminum grain size using a ring-shaped laser ultrasonic method
Authors: Xue Renjie , Xu Dong , Yang Quan , Wang Xiaochen , Sun Youzhao , Zhang Jiamin
Published: April 2022

In this study, a nondestructive ring-shaped laser ultrasonic method with a thermoelastic excitation regime was used to determine the grain size of metal materials. This method was proposed in order to evaluate the quality of metal in a fast online nondestructive manner. Normally, laser ultrasonic is used to detect grain size in the ablation excitation regime. The laser excites high energy longitudinal waves but causes damage to the surface of metal materials. To achieve strict online nondestructive testing, the thermoelastic regime was used in this work. The ring-shaped laser was converted from a circular collimated laser by an axicon and irradiated on the surface of the aluminum sample to induce ultrasonic waves and enhance the signal amplitude. The directivity pattern was analyzed to find a suitable detection parameter by the finite element method before performing laser ultrasound experiments. Quantitative analysis of the converging waves with different deviations from the center via laser ultrasound experiments demonstrated the enhancement effect of signal energy using a ring-shaped laser. The issues of low signal energy and the generation of a directivity pattern were solved by this ring-shaped laser ultrasonic method aimed at nondestructive grain size inspection. Aluminum samples with different mean grain sizes were detected by ring-shaped laser ultrasonic technology. A grain size characterization model was built with mean grain sizes and ultrasonic signals. Laser-generated ultrasound technology in the thermoelastic regime is a promising online detection method and can be used to detect material properties nondestructively with a ring-shaped laser.
Data driven discovery of a model equation for anode-glow oscillations in a low pressure plasma discharge
Authors: Thakur Bhumika , Sen Abhijit , Chaubey Neeraj
Published: April 2022

A plasma glow discharge tube, a versatile device widely employed in several scientific and industrial applications, is also a useful tool for many basic plasma studies in the laboratory. Anode glow oscillations are well-known phenomena in such devices that arise from an instability of the plasma glow around a small positively charged electrode. Depending upon the gas pressure, the applied DC voltage, and the distance between the electrodes, these oscillations can display a rich dynamical behavior. Over a certain parametric regime, these nonlinear oscillations exhibit a stable limit cycle behavior that has been modeled in the past by a Van der Pol like equation. While such a model equation provides a qualitative description of the observations, it lacks quantitative agreement and does not have any predictive capability. We employ the sparse identification of nonlinear dynamics (SINDy) method to obtain a model equation directly from a time series of the experimental data. Our model captures well the main features of the experimental data in a quantitative manner. It also shows a significant deviation from the Van der Pol model due to additional contributions that are akin to nonlinear damping in a Rayleigh oscillator. Such a hybrid Van der Pol–Rayleigh oscillator model could provide a useful paradigm for future explorations of the nonlinear dynamics of this system.
A novel method for photon unfolding spectroscopy of protein ions in the gas phase
Authors: Zhou Min , Jiao Luyang , Xu Shiyin , Xu Yicheng , Du Mengying , Zhang Xianyi , Kong Xianglei
Published: April 2022

In this study, a new experimental method for photon unfolding spectroscopy of protein ions based on a Fourier transform ion cyclotron resonance (FT ICR) mass spectrometer was developed. The method of short-time Fourier transform has been applied here to obtain decay curves of target ions trapped in the cell of the FT ICR mass spectrometer. Based on the decay constants, the collision cross sections (CCSs) of target ions were calculated using the energetic hard-sphere model. By combining a tunable laser to the FT ICR mass spectrometer, the changes of CCSs of the target ions were recorded as a function of the wavelengths; thus, the photon isomerization spectrum was obtained. As one example, the photon isomerization spectrum of [Cyt c + 13H]13+ was recorded as the decay constants relative to the applied wavelengths of the laser in the 410–480 nm range. The spectrum shows a maximum at 426 nm, where an unfolded structure induced by a 4 s irradiation can be deduced. The strong peak at 426 nm was also observed for another ion of [Cyt c + 15H]15+, although some difference at 410 nm between the two spectra was found at the same time. This novel method can be expanded to ultraviolet or infrared region, making the experimental study of wavelength-dependent photon-induced structural variation of a variety of organic or biological molecules possible.
Design of high-pressure iron Rayleigh–Taylor strength experiments for the National Ignition Facility
Authors: Righi Gaia , Lockard Thomas E. , Rudd Robert E. , Meyers Marc A. , Park Hye-Sook
Published: April 2022

Iron is an important metal, scientifically and technologically. It is a common metal on Earth, forming the main constituent of the planet's inner core, where it is believed to be in solid state at high pressure and high temperature. It is also the main component of many important structural materials used in quasistatic and dynamic conditions. Laser-driven Rayleigh–Taylor instability provides a means of probing material strength at high pressure and high temperature. The unavoidable phase transition in iron at relatively low pressure induces microstructural changes that ultimately affect its strength in this extreme regime. This inevitable progression can make it difficult to design experiments and understand their results. Here, we address this challenge with the introduction of a new approach: a direct-drive design for Rayleigh–Taylor strength experiments capable of reaching up to 400 GPa over a broad range of temperatures. We use 1D and 2D hydrodynamic simulations to optimize target components and laser pulse shape to induce the phase transition and compress the iron to high pressure and high temperature. At the simulated pressure–temperature state of 350 GPa and 4000 K, we predict a ripple growth factor of 3–10 depending on the strength with minimal sensitivity to the equation of state model used. The growth factor is the primary observable, and the measured value will be compared to simulations to enable the extraction of the strength under these conditions. These experiments conducted at high-energy laser facilities will provide a unique way to study an important metal.
A survey of pedestal magnetic fluctuations using gyrokinetics and a global reduced model for microtearing stability
Authors: Curie M. T. , Larakers J. L. , Hatch D. R. , Nelson A. O. , Diallo A. , Hassan E. , Guttenfelder W. , Halfmoon M. , Kotschenreuther M. , Hazeltine R. D. , Mahajan S. M. , Groebner R. J. , Chen J. ,   DIII-D Team, Perez von Thun C. , Frassinetti L. , Saarelma S. , Giroud C. ,   JET Contributors, Tennery M. M.
Published: April 2022

This article presents a global reduced model for slab-like microtearing modes (MTMs) in the H-mode pedestal, which reproduces distinctive features of experimentally observed magnetic fluctuations, such as chirping and discrete frequency bands at noncontiguous mode numbers. Our model, importantly, includes the global variation of the diamagnetic frequencies, which is necessary to reproduce the experimental observations. The key insight underlying this model is that MTM instability is enabled by the alignment of a rational surface with the peak in the profile of the diamagnetic frequency. Conversely, MTMs are strongly stabilized for toroidal mode numbers for which these quantities are misaligned. This property explains the discrete fluctuation bands in several DIII-D and JET discharges, which we survey using our reduced model in conjunction with global gyrokinetic simulations. A fast yet accurate reduced model for MTMs enables rapid interpretation of magnetic fluctuation data from a wide range of experimental conditions to help assess the role of MTM in the pedestal.
Experimental demonstration of exceptional points of degeneracy in linear time periodic systems and exceptional sensitivity
Authors: Kazemi Hamidreza , Nada Mohamed Y. , Nikzamir Alireza , Maddaleno Franco , Capolino Filippo
Published: April 2022

We present the experimental demonstration of the occurrence of exceptional points of degeneracy (EPDs) in a single resonator by introducing a linear time-periodic variation of one of its components. This is in contrast with the requirement of two coupled resonators with parity time-symmetric systems with precise values of gain and loss. In the proposed scheme, only the tuning of the modulation frequency is required, which is easily achieved in electronic systems. The EPD is a point in a system parameters’ space at which two or more eigenstates coalesce, and this leads to unique properties not occurring at other non-degenerate operating points. We show theoretically and experimentally the existence of a second-order EPD in a time-varying single resonator. Furthermore, we measure the sensitivity of the proposed system to a small structural perturbation and show that the two shifted system’s eigenfrequencies are well detected even for relative perturbations of 0.3%, with distinguished peaks well above the noise floor. We show that the regime of operation of the system at an EPD leads to a unique square-root-like sensitivity, which can devise new exceptionally sensitive sensors based on a single resonator by simply applying time modulation.
Axisymmetric Alfvén modes induced by energetic particles in tokamak plasmas
Authors: Zhou Deng , Yang Xiaoqing , Ming Yue , Gan Chenxiao
Published: April 2022

Axisymmetric Alfvén modes in the presence of energetic ions are studied using the MHD-kinetic hybrid model for tokamak plasmas. The general dispersion relation of continuous spectra is derived for the coupled m=0,±2 poloidal harmonics. The dispersion relation is analyzed for the single pitch angle slowing down distribution of well circulating energetic particles. In addition to the conventional axisymmetric Alfvén modes existing in the pure MHD description, axisymmetric Alfvén modes are also induced by the energetic ions if the pressure ratio between the energetic ions and the magnetic energy density is larger than a critical value, and the transit frequency of the energetic ions is in resonance with the emerging Alfvén modes. The existence of global Alfvén eigenmodes is also discussed.
Microscopic analysis of sound attenuation in low-temperature amorphous solids reveals quantitative importance of non-affine effects
Authors: Szamel Grzegorz , Flenner Elijah
Published: April 2022

Sound attenuation in low-temperature amorphous solids originates from their disordered structure. However, its detailed mechanism is still being debated. Here, we analyze sound attenuation starting directly from the microscopic equations of motion. We derive an exact expression for the zero-temperature sound damping coefficient. We verify that the sound damping coefficients calculated from our expression agree very well with results from independent simulations of sound attenuation. Small wavevector analysis of our expression shows that sound attenuation is primarily determined by the non-affine displacements’ contribution to the sound wave propagation coefficient coming from the frequency shell of the sound wave. Our expression involves only quantities that pertain to solids’ static configurations. It can be used to evaluate the low-temperature sound damping coefficients without directly simulating sound attenuation.
Alchemical geometry relaxation
Authors: Domenichini Giorgio , von Lilienfeld O. Anatole
Published: April 2022

We propose the relaxation of geometries throughout chemical compound space using alchemical perturbation density functional theory (APDFT). APDFT refers to perturbation theory involving changes in nuclear charges within approximate solutions to Schrödinger’s equation. We give an analytical formula to calculate the mixed second order energy derivatives with respect to both nuclear charges and nuclear positions (named “alchemical force”) within the restricted Hartree–Fock case. We have implemented and studied the formula for its use in geometry relaxation of various reference and target molecules. We have also analyzed the convergence of the alchemical force perturbation series as well as basis set effects. Interpolating alchemically predicted energies, forces, and Hessian to a Morse potential yields more accurate geometries and equilibrium energies than when performing a standard Newton–Raphson step. Our numerical predictions for small molecules including BF, CO, N2, CH4, NH3, H2O, and HF yield mean absolute errors of equilibrium energies and bond lengths smaller than 10 mHa and 0.01 bohr for fourth order APDFT predictions, respectively. Our alchemical geometry relaxation still preserves the combinatorial efficiency of APDFT: Based on a single coupled perturbed Hartree–Fock derivative for benzene, we provide numerical predictions of equilibrium energies and relaxed structures of all 17 iso-electronic charge-neutral BN-doped mutants with averaged absolute deviations of ∼27 mHa and ∼0.12 bohr, respectively.
Vibration reconstruction for a point-excited plate based on acoustic radiation modes and sound pressure measurement
Authors: Jiang Liying , Lin Fan , Liu Zubin
Published: April 2022

The inverse problem of sound radiation from a vibrating structure is one of the key problems in vibro-acoustics; however, sound source reconstruction with sound pressure measurement still has challenges from sound field assumptions and measurement noise. Due to orthogonality and unrestricted source, Acoustic Radiation Modes (ARMs) are seen as promising basis vectors to realize sound source reconstruction. Here, near-field ARMs obtained by the pressure-velocity method were proposed to construct a series of orthogonal basis vectors for the vibration velocity of a point-excited rectangular plate, and a new procedure of rearrangement and truncation of basis vectors is proposed to obtain the top-ranking vectors with their contribution. Finally, vibration reconstruction is realized with least finite vectors to reach a certain accuracy. Numerical simulations show that vibration reconstruction errors are below 10% with less than 20 orders of basis vectors at frequency range kL ≤ 2π and white noise SNR = 30 dB. The smaller distance of the measuring surface and lower frequency of sound lead to higher reconstruction accuracy and less necessary basis vectors. The factors affecting reconstruction accuracy were also studied by white noise level, amount of basis vectors, and number of measuring points.
Kinetic modeling of fractal aggregate mobility
Authors: Vijayan Akhil Marayikkottu , Levin Deborah A.
Published: April 2022

Although the mobility or transport parameters, such as lift drag and pitching moments for regular-shaped particulates, are widely studied, the mobility of irregular fractal-like aggregates generated by the aggregation of monomers is not well understood. These particulates which are ubiquitous in nature, and industries have very different transport mechanisms as compared to their spherical counterpart. A high-fidelity direct simulation Monte Carlo (DSMC) study of two fractal aggregates of different shapes or dimensions is undertaken in the slip and transitional gas regime to understand the underlying mechanism of gas-particle momentum transfer that manifests as the orientation-averaged mobility parameters of the particulates. The study specifically focuses on the viscous contribution of these parameters and develops a non-linear correlation for drag and lift parameters p and q obtained from DSMC by normalizing the axial and lateral forces. The drag parameter p predicted a monotonic increase in fractal particulate drag with respect to a spherical monomer while the lift parameter q shows an initial increasing trend but a decreasing tendency toward the high Mach number or high compressibility regime. The approximate model that captures the compressibility and rarefaction effects of the fractal mobility is used to study the evolution of these particulates in a canonical Rankine vortex to illustrate the wide disparity in the trajectories of the fractal aggregate vs a spherical geometry approximation generally found in the literature.
Turbulence in a compound channel with the combination of submerged and emergent vegetation
Authors: Barman Jyotirmoy , Kumar Bimlesh
Published: April 2022

Floodplain vegetation is heterogeneous with varying heights and spacing. Laboratory studies concerning compound channels with mixed submerged and emergent vegetation are scarce. This paper attempts to address the difference in flow behavior when it encounters single-layered submerged or emergent vegetation or a combination of both. Two different sets of uniform and non-uniform vegetation setups are considered. Vegetation cases with submerged, emergent, and mixed vegetation are considered for each set. The velocity in the floodplain region of fully emergent cases is higher than that in combined vegetation because of the less frontal area provided by the emergent vegetation. The Reynolds shear stress is also higher in the lower depth of the main channel in combined vegetation compared to uniform height vegetation, especially in the uniform vegetation setup. Turbulent anisotropy and octant analysis are studied in detail to get further insight into flow behavior in different vegetation setups. The anisotropic invariant map and invariant function F reveal that the main channel section of 67% emergent vegetation case has a greater tendency to approach two-dimensional turbulence than other non-uniform vegetation setups. Octant analysis study shows that internal sweep in the main channel is highest in 34% emergent uniform vegetation setup and lowest in 100% emergent non-uniform vegetation setup.
Unveiling the parasitic electron channel under the gate of enhancement-mode p-channel GaN field-effect transistors on the p-GaN/AlGaN/GaN platform
Authors: Zheng Zheyang , Chen Tao , Zhang Li , Song Wenjie , Chen Kevin J.
Published: April 2022

Enhancement-mode (E-mode) p-channel gallium nitride (GaN) field-effect transistors (p-FETs) are essential components for GaN-based complementary logic circuits. For the ease of integration with n-FETs, they could be fabricated on the commercial p-GaN gate high-electron-mobility-transistor (HEMT) platform, on which the two-dimensional electron gas at the AlGaN/GaN hetero-interface is completely depleted in as-grown epi-structures. However, under the gated region where p-GaN is recessed and depleted at thermal equilibrium, a parasitic electron channel (PEC) could appear at the AlGaN/GaN interface. This Letter reports experimental investigations on the PEC with specifically designed structures, confirming that the PEC does exist but imposes limited impacts on electrical characteristics of p-FETs. When connected with an external contact, the PEC could act as a back gate to modulate the overlaying p-channel. If isolated from external contacts, which is the case of p-FETs under normal operations, electrons in the PEC would redistribute under the active region of p-FETs in the horizontal direction (i.e., parallel to the surface) under different biases but are mostly confined near the AlGaN/GaN interface in the vertical direction (i.e., perpendicular to the surface).
Two inch diameter, highly conducting bulk
β
-Ga2O3 single crystals grown by the Czochralski method
Authors: Galazka Zbigniew , Ganschow Steffen , Seyidov Palvan , Irmscher Klaus , Pietsch Mike , Chou Ta-Shun , Bin Anooz Saud , Grueneberg Raimund , Popp Andreas , Dittmar Andrea , Kwasniewski Albert , Suendermann Manuela , Klimm Detlef , Straubinger Thomas , Schroeder Thomas , Bickermann Matthias
Published: April 2022

Two inch diameter, highly conducting (Si-doped) bulk β-Ga2O3 single crystals with the cylinder length up to one inch were grown by the Czochralski method. The obtained crystals revealed high structural quality characterized by narrow x-ray rocking curves (FWHM ≤ 25 arc sec) and high surface smoothness (RMS < 200 pm) of the epi-ready wafers. The free electron concentration and Hall mobility at room temperature were in the range of 1.6–9 × 1018 cm−3 and 118 – 52 cm2 V−1 s−1, respectively, which are not affected by a heat treatment at temperatures up to 1000 °C in an oxidizing atmosphere. Temperature-dependent electrical properties of the crystals revealed a degenerated semiconducting state. Both high structural quality and electrical properties make the crystals well suited as substrates for homoepitaxy and electronic device fabrication in the vertical configuration.
Investigation of unsteady cryogenic cavitating flow and induced noise around a three-dimensional hydrofoil
Authors: Wei Aibo , Wang Shunhao , Gao Xu , Qiu Limin , Yu Lianyan , Zhang Xiaobin
Published: April 2022

In this paper, the Large Eddy Simulation (LES) combined with the Schnerr–Sauer cavitation model and the permeable Ffowcs Williams–Hawkings (FW-Hpds) acoustic analogy approach are introduced to study the unsteady cavitation behaviors and the radiated noise characteristics of the transient liquid nitrogen (LN2) cavitating flow around a NACA66 (National Advisory Committee for Aeronautics) hydrofoil. Satisfactory agreement is obtained between the numerical predictions and experimental measurements. The cavitation noise is predicted based on the sound radiation theory for spherical bubbles and compared with the sound pressure levels of non-cavitating flow from the FW-Hpds equation. It is found that the cavity volume acceleration is directly responsible for driving the generation of cavitation noise, and the sound pressure caused by the development of LN2 cavitation is shown to vary with the periodic pulsing cavity volume evolution, indicating a strong link between cavity evolutions and radiated noises. The transient cavitation structures of the sheet and cloud cavitation are well captured, and the evolution features of the cavities and vortex structures are analyzed in detail. The collapse of the detached small cloud cavity downstream is the main mechanism for generating intense acoustic impulses for both sheet and cloud cavitation. While the strong interaction between the re-entrant jet and the main flow results in violent pressure fluctuations, and thus produces instantaneous extreme dipole noise, which accounts for another distinctive mechanism to induce intense acoustic impulses for cloud cavitation, the presented study provides a deep understanding of the nature of cavitation-dominated noise for cryogenic cavitating flow.
Particle–liquid transport in curved microchannels: Effect of particle volume fraction and size in Dean flow
Authors: Sivasankar Vishal Sankar , Wang Yanbin , Natu Rucha , Porter Daniel , Herbertson Luke , Craven Brent A. , Guha Suvajyoti , Das Siddhartha
Published: April 2022

Microfluidic transport in spiral channels is a promising flow-driven mechanism for applications such as cell sorting and particle focusing. Spiral channels have unique curvature-driven flow characteristics that trigger Dean flow, forcing the liquid to be displaced toward the outer wall of the microchannel due to centrifugal force. Despite the growing popularity of these applications, there is a lack of physical understanding of such particle–fluid two-phase transport in a spiral microchannel. To address this gap, in this paper we employ a coupled particle-transport-microfluidic-flow (two-phase) computational fluid dynamics model for probing such two-phase transport in a curved microchannel that gives rise to Dean flow. Our simulations reveal that the presence of the particles has two effects: (1) they reduce the Dean flow effect of skewing the flow field toward the outer wall, that is, the flow becomes more symmetric (or the velocity maximum moves toward the center of the channel) and (2) there is a significant alteration in the vortex patterns associated with the Dean flow. We quantify the drag and lift forces experienced by the particles and propose that the corresponding particle-imparted drag and the lift forces on the continuous phase counter the effect of the curvature-driven centrifugal force on the continuous phase, thereby altering the Dean flow characteristics. Furthermore, we anticipate that such precise quantification of the forces experienced by these particles, present in finitely large concentration in microfluidic Dean flow, will be critical in designing Dean flow effect driven size-based microfluidic particle separation.
Correlation of drag coefficient between rising bubbles in chain
Authors: Liu Ming , Wang Binbin , Tan Lei
Published: April 2022

Bubbles-in-chain is a two-phase fluid flow phenomenon in natural environments and engineering practices with unique bubble–bubble interactions. The interactions among bubbles lead to a periodically varying local drag coefficient, which has been rarely studied. Here, we report a numerical investigation of rising bubbles in a chain using large eddy simulation and coupled volume-of-fluid and level-set methods to examine the local drag coefficient and its predicting models. We first validated the bubble diameter and rise velocity with an experimental dataset. The local drag coefficient was then calculated and compared with the traditional Weber number based model. We propose a modified Weber number model with a trigonometric relation, defining the upper and lower limits of the drag coefficient as a result of bubble–bubble interactions. With the proposed model, the predicted drag coefficient shows an acceptable accuracy with errors less than 7%. The resolved flow field in the bubble wake confirms the correlation among the drag coefficient, wake velocity, and rising velocity. This mechanism provides a stable and periodical variation of the drag coefficient in the bubbles-in-chain system.
Resonance conditions, detection quality, and single-molecule sensitivity in fluorescence-encoded infrared vibrational spectroscopy
Authors: Whaley-Mayda Lukas , Guha Abhirup , Tokmakoff Andrei
Published: April 2022

Fluorescence-encoded infrared (FEIR) spectroscopy is a vibrational spectroscopy technique that has recently demonstrated the capability of single-molecule sensitivity in solution without near-field enhancement. This work explores the practical experimental factors that are required for successful FEIR measurements in both the single-molecule and bulk regimes. We investigate the role of resonance conditions by performing measurements on a series of coumarin fluorophores of varying electronic transition frequencies. To analyze variations in signal strength and signal to background between molecules, we introduce an FEIR brightness metric that normalizes out measurement-specific parameters. We find that the effect of the resonance condition on FEIR brightness can be reasonably well described by the electronic absorption spectrum. We discuss strategies for optimizing detection quality and sensitivity in bulk and single-molecule experiments.
Investigating the high field transport properties of Janus WSSe and MoSSe by DFT analysis and Monte Carlo simulations
Authors: Pai Hsiu-Chi , Wu Yuh-Renn
Published: April 2022

Janus transition metal dichalcogenides with out-of-plane structural asymmetry have attracted increasing attention due to their exceptional potential in electronic and optical applications. In this study, we systematically investigated the electron–phonon interactions and related transport properties in monolayer Janus MoSSe and WSSe using the density-functional formalism. The electron–phonon scattering rates were obtained using Fermi’s golden rule and extended to the extraction of the effective deformation potential constants for further Monte Carlo treatment. From the results of the Monte Carlo analysis, we found that WSSe provides better performance with higher low-field mobility, while MoSSe shows a higher peak velocity at higher fields. In our results, both MoSSe and WSSe seem to be competitive with other previously studied 2D materials. These predictions provide a systematic perspective on the potential of Janus WSSe and MoSSe for electronic applications.
Comparison between one- and two-way coupling approaches for estimating effective transport properties of suspended particles undergoing Brownian sieving hydrodynamic chromatography
Authors: Venditti Claudia , Cerbelli Stefano , Procopio Giuseppe , Adrover Alessandra
Published: April 2022

Simplified one-way coupling approaches are often used to model transport properties of diluted particle suspensions for predicting the performance of microcapillary hydrodynamic chromatography (MHDC). Recently, a one-way coupling approach was exploited to optimize the geometry and operating conditions of an unconventional double-channel geometry with a square cross section, where a Brownian sieving mechanism acting alongside the MHDC separation drive (BS-MHDC) is enforced to boost separation resolution. In this article, a cylindrical geometry enforcing the same BS-MHDC separation drive is thoroughly investigated by following a two-way coupling, fully three-dimensional approach, and results are compared with those obtained enforcing the one-way coupling analysis. Device geometry and operating conditions are optimized by maximizing the separation resolution. The effective velocity and dispersion coefficient of spherical, finite-sized particles of different diameters are computed, and two-phase effects are discussed in detail. Similar to the square channel device, the cylindrical double-channel geometry allows for a sizable reduction in the column length and in the analysis time (a factor above 12 for the length and a factor larger than 3 for the processing time) when compared to the standard MHDC configuration ensuring the same separation resolution. As expected, the one-way coupling approach overestimates the separation performance of both the BS-MHDC and the standard MHDC devices with respect to the two-way coupling analysis. But, surprisingly, the enhancement factor of the BS-MHDC over the standard MHDC is underestimated by the single-phase approximation as it doubles when wall/particle interactions are properly accounted for with a two-phase description.
Unraveling multi-state molecular dynamics in single-molecule FRET experiments. I. Theory of FRET-lines
Authors: Barth Anders , Opanasyuk Oleg , Peulen Thomas-Otavio , Felekyan Suren , Kalinin Stanislav , Sanabria Hugo , Seidel Claus A. M.
Published: April 2022

Conformational dynamics of biomolecules are of fundamental importance for their function. Single-molecule studies of Förster Resonance Energy Transfer (smFRET) between a tethered donor and acceptor dye pair are a powerful tool to investigate the structure and dynamics of labeled molecules. However, capturing and quantifying conformational dynamics in intensity-based smFRET experiments remains challenging when the dynamics occur on the sub-millisecond timescale. The method of multiparameter fluorescence detection addresses this challenge by simultaneously registering fluorescence intensities and lifetimes of the donor and acceptor. Together, two FRET observables, the donor fluorescence lifetime τD and the intensity-based FRET efficiency E, inform on the width of the FRET efficiency distribution as a characteristic fingerprint for conformational dynamics. We present a general framework for analyzing dynamics that relates average fluorescence lifetimes and intensities in two-dimensional burst frequency histograms. We present parametric relations of these observables for interpreting the location of FRET populations in E–τD diagrams, called FRET-lines. To facilitate the analysis of complex exchange equilibria, FRET-lines serve as reference curves for a graphical interpretation of experimental data to (i) identify conformational states, (ii) resolve their dynamic connectivity, (iii) compare different kinetic models, and (iv) infer polymer properties of unfolded or intrinsically disordered proteins. For a simplified graphical analysis of complex kinetic networks, we derive a moment-based representation of the experimental data that decouples the motion of the fluorescence labels from the conformational dynamics of the biomolecule. Importantly, FRET-lines facilitate exploring complex dynamic models via easily computed experimental observables. We provide extensive computational tools to facilitate applying FRET-lines.
Ultra-wide-temperature-range superelasticity and intrinsic two-way shape memory effect in Co–Ni–Ga microwires
Authors: Zhang Xiangyu , Chen Haiyang , Niu Yurong , Li Runguang , Yin Tao , Lang Runqiu , Song Chao , Meng Lingyun , Cong Daoyong , Li Shilei , Wang Yan-Dong
Published: April 2022

We demonstrate perfect superelasticity and inherent two-way shape memory effect in Co49Ni21Ga30 microwires fabricated by a Taylor–Ulitovsky method. With the formation of an almost complete [001]A-oriented single crystal along the axis of the wire, the as-drawn microwire displays great superelastic behaviors with a large reversible tensile strain of >8% over an ultra-wide temperature window of 550 K (223–773 K). Simultaneously, an excellent intrinsic two-way shape memory effect with a considerably large strain output (∼6.3%) was also obtained in this Co49Ni21Ga30 microwire. After mechanical training, the two-way shape memory strain can reach up to 6.8% at a low operating temperature. With the combination of above extraordinary functional properties and the low cost of fabrication, the Co49Ni21Ga30 microwire holds a significant potential for applications in miniature sensing and self-actuating devices in the future.
Instabilities of buoyancy-induced flow along vertical cylinder in thermally stratified medium
Authors: Xiao Yue , Zhang Bin , Zhao Moli , Wang Shaowei
Published: April 2022

In this paper, the instability of the buoyancy-driven boundary layer on a vertical cylinder is considered. We provide a mathematical description of a vertical cylinder immersed in a stably stratified fluid, and the analytical solutions of the basic flow are derived. Based on linear stability analysis, the effects of Prandtl number and transversal curvature have been investigated. It is found that the most unstable mode for Pr = 0.7 is three-dimensional for the cylindrical radii between 0.03 and 46, while the critical modes are axisymmetric for Pr = 7 and 100. All the results for different Pr are consistent with those of the vertical plate when the radius is large enough. Additionally, for absolute instability analysis, there exists absolute instability in the present model when the dimensionless radius is less than 0.31, which is quite different from the results obtained in the vertical plate. These encouraging results revealed in this paper should be helpful for understanding such a buoyancy-driven flow system.
On the maximal spreading of drops impacting onto a no-slip substrate
Authors: Wang Rui , Shi Yan-Zhao , Zhang Chun-Yu , Ding Hang
Published: April 2022

We numerically study the impact of a liquid drop onto no-slip rigid substrates with different wettabilities using a diffuse interface method, aiming to obtain a universal model for the maximal spreading of the impacting drop at moderate Weber numbers. We find that the wettability plays an important role in the maximal spreading and that the ratio of the surface energy to the initial kinetic energy of the drop at the maximal spreading, η, follows η∼We−1/2 at high fixed Reynolds numbers, where We is the Weber number. Taking account of the wettability effect, we obtain a scaling law at high Reynolds numbers from an analysis of energy transformation. This scaling law is compatible with the one derived from the momentum balance at the high impact velocity by Clanet et al. [“Maximal deformation of an impacting drop,” J. Fluid Mech. 517, 199–208 (2004)]. Moreover, we attribute it to the presence of a viscous–capillary regime, in which the viscous dissipation of the kinetic energy from the substrate is as significant as the kinetic energy transformed into the surface energy. Accordingly, we identify a new impact parameter, which makes all the numerical results of maximum drop deformation (from the viscous regime to the viscous–capillary regime with Reynolds number up to 104) collapse onto a single curve. Finally, we propose a universal model, the predictions of which are shown to agree well with numerical results for a wide range of Weber and Reynolds numbers.