bluuebunny/crossref_metadata_2025 huggingface dataset:
Emicizumab Dosing in Children and Adults with Hemophilia A: Simulating a User-Friendly and Cost-Efficient Regimen
Authors: Bukkems Laura H. , Fischer Kathelijn , Kremer-Hovinga Idske , Donners Anouk A. M. , Fijnvandraat Karin , Schutgens Roger E. G. , Cnossen Marjon H. , Mathôt Ron A. A.
Published: May 2021

Background When emicizumab is dosed according to label, clinicians are obligated to discard or overdose medication due to discrepancies between calculated dose and vial content. The aim of this study was to compose a cost-efficient emicizumab maintenance dosing regimen using Monte Carlo simulation based on vial size, patient-friendly intervals, and patient characteristics, while striving for similar plasma concentrations as observed in clinical trials.

Methods Monte Carlo simulations were used to investigate alternative dosing regimens in patients weighing 3 to 150 kg. Simulated regimens were targeted to achieve median emicizumab plasma concentrations at a steady state (C av,ss) of 40 to 60 (90% range: 25–95) µg/mL. The cost-efficiency of the alternative dosing regimen was calculated in mg and costs saved per patient per year.

Results The developed alternative dosing regimen achieved similar emicizumab C av,ss levels compared with the registered dosing regimen with a median deviation of less than 2 µg/mL in 78% of the body-weight categories. A dose of 60 mg every 3 weeks was advised for children weighing 12 to 16 kg, while adults weighing 76 to 85 kg can receive 120 mg emicizumab every week. Compared with the registered weekly dosing of 1.5 mg/kg, alternative dosing saved €35,434 per year in children weighing between 12 and 16 kg. For patients weighing 76 to 85 kg, the median saving was €29,529 (range: €0–€59,057).

Conclusion This alternative maintenance dosing scheme—applicable in patients with hemophilia A receiving emicizumab prophylaxis—reduces financial costs, avoids medication spillage, and is patient-friendly without loss of efficacy.
Direct Synthesis of N-Protected Serine- and Threonine-Derived Weinreb Amides via Diboronic Acid Anhydride-Catalyzed Dehydrative Amidation: Application to the Concise Synthesis of ­Garner’s Aldehyde
Authors: Shimada Naoyuki , Ohse Naoki , Takahashi Naoya , Urata Sari , Koshizuka Masayoshi , Makino Kazuishi
Published: May 2021

An efficient method for the direct synthesis of Weinreb amides derived from serine and threonine derivatives via diboronic acid anhydride-catalyzed hydroxy-directed amidation is described. This is the first successful example of the synthesis of serine- or threonine-derived Weinreb amides using catalytic dehydrative amidations. The methodology could be applied to the concise synthesis of Garner’s aldehyde.
Venous Thromboembolism Therapy with Apixaban in Daily Care Patients: Results from the Dresden NOAC Registry
Authors: Beyer-Westendorf Jan , Marten Sandra , Tittl Luise , Naue Christiane , Bornhäuser Martin
Published: May 2021

The effectiveness and safety of venous thromboembolism (VTE) treatment with apixaban, demonstrated in phase III trials, need to be confirmed in daily care.

Using data from the prospective, noninterventional cross-indication Dresden NOAC Registry we evaluated rates of VTE recurrence and bleeding complications during apixaban treatment of VTE patients. For this analysis, we only included patients with acute VTE who started apixaban within 14 days after diagnosis and who were enrolled within these 14 days. Patient characteristics, treatment persistence, and clinical outcomes were assessed.

Between August 1st, 2014 and October 31, 2018, 352 patients with apixaban treatment for acute VTE were enrolled. During treatment (median exposure 13.7 ± 9.8 months; median follow-up 21.7 ± 6.1 months) rates of recurrent VTE and International Society on Thrombosis and Haemostasis major bleeding were 1.3/100 pt.years (95% confidence interval or CI 0.4–3.0) and 1.5/100 pt.years (0.6–3.3), respectively. At 6 months. 68.6% of patients were still taking apixaban, 23.9% had a scheduled end of treatment, 6.3% were switched to other anticoagulants, and the remaining 2.3% had unplanned complete discontinuation of anticoagulation.

Of the 188 patients stopping apixaban, 12 (6.4%) experienced a recurrent VTE (six pulmonary embolisms ± deep vein thrombosis, six deep vein thrombosis; mean time between stopping anticoagulation and VTE recurrence 5.2 ± 4.1 months [range 14–417 days]).

Our findings suggest that, in daily care, apixaban demonstrated high effectiveness, safety, and persistence in the treatment of acute VTE with low rates of unplanned discontinuation.
Treatment of Periprosthetic Joint Infection in Total Knee Arthroplasty with a Temporary Intramedullary Nail: Is a Long or Short Nail Better?
Authors: Mohamed Nequesha S. , Castrodad Iciar M. Davila , Etcheson Jennifer I. , Kelemen Margaret N. , Plate F. Johannes , Conway Janet D. , Delanois Ronald E.
Published: May 2021

To our knowledge, no studies have compared postoperative outcomes between patients who received a temporary short or long intramedullary (IM) nail in the setting of infected total knee arthroplasty (TKA). Therefore, the aim of this study was to compare short-term outcomes for patients who underwent long or short IM nail insertion for treatment of periprosthetic knee infection. Specifically, we compared: (1) success rates; (2) patient reported/functional outcomes; and (3) complications between patients implanted with a short or a long IM nail following PJI of the knee. A retrospective chart review was performed for patients who underwent two-stage exchange arthroplasty with a temporary long or short IM nail between November 2010 and June 2018 at our institution (n = 67). Continuous and categorical variables were assessed using t-test/Mann–Whitney U test and chi-squared test, respectively. Logistic regression analyses were conducted to assess the effect of IM nail length on success rate while adjusting for age, sex, body mass index, and race. A total of 36 patients underwent temporary treatment with a long IM nail, while 31 patients received a short IM nail. There were no differences in success rate for reimplanted patients treated with long and short IM nails (odds ratio 0.992; p = 0.847). Fewer patients with a long IM nail went on to reimplantation (52.8 vs. 83.9%; p = 0.007). There was no difference in satisfaction (7.86 vs. 7.68; p = 0.515), pain scores (3.39 vs. 4.45 points; p = 0.126), or Knee Society score outcome scores (150.61 vs. 166.26 points; p = 0.117) between long or short IM nail patients. Following reimplantation, there was no difference in the number of patients who became reinfected (15.8 vs. 11.5%; p = 0.679) or went on to amputation (0 vs. 7.7%; p = 0.210). Periprosthetic joint infection (PJI) is a rare but serious postoperative complication following TKA. Our findings suggest that the use of long and short IM nails during two-stage exchange can have equal utility in PJI patients with severe bone defects.
Unlocking the materials to new electronic behavior
Authors: Lim Alane
Published: May 2021

The synthesis of a family of layered pnictides have garnered attention for their unique electronic properties.
Where nuclear quantum effects can provide physical insights
Authors: Bandari Anashe
Published: May 2021

Many atomistic simulations do not include nuclear quantum effects, but with improvements to computational techniques and power, there may be no reason to continue ignoring them.
Large deviations of the entropy production rate for a class of Gaussian processes
Authors: Budhiraja Amarjit , Chen Yong , Xu Lihu
Published: May 2021

We prove a large deviation principle (LDP) and a fluctuation theorem for the entropy production rate (EPR) of the following d dimensional stochastic differential equation dXt=AXtdt+QdBt, where A is a real normal stable matrix, Q is positive definite, and the matrices A and Q commute. The rate function for the EPR takes the following explicit form: I(x)=x1+ℓ0(x)−12+12∑k=1dαk2−βk2ℓ0(x)+αk for x ≥ 0 and I(x)=−x1+ℓ0(x)+12+12∑k=1dαk2−βk2ℓ0(x)+αk for x < 0, where αk ±iβk are the eigenvalues of A and ℓ0(x) is the unique solution of the equation x=1+ℓ×∑k=1dβk2αk2−ℓβk2,−1≤ℓ<mink=1,…,dαk2βk2. Simple closed form formulas for rate functions are rare, and our work identifies an important class of large deviation problems where such formulas are available. The logarithmic moment generating function (the fluctuation function) Λ associated with the LDP is given as Λ(λ)=−12∑k=1dαk2−4λ(1+λ)βk2+αk for λ∈D and Λ(λ) = ∞ for λ∉D, where D is the domain of Λ. The functions Λ(λ) and I(x) satisfy the Cohen–Gallavotti symmetry properties: Λ(x)=Λ(−(1+x)),I(x)=I(−x)−x, for all x∈R. In particular, the functions I and Λ do not depend on the diffusion matrix Q and are determined completely by the real and imaginary parts of the eigenvalues of A. Formally, the deterministic system with Q = 0 has zero EPR, and thus, the model exhibits a phase transition in that the EPR changes discontinuously at Q = 0.
All-optical laser-ultrasonic technology for width and depth gauging of rectangular surface-breaking defects
Authors: Chen Cheng , Ju Bing-Feng , Yang Xiaoyu , Wang Chuanyong , Sun Anyu , Gong Jinlu , Li Zhihong
Published: May 2021

In this paper, the width and depth of rectangular surface-breaking defects were successfully gauged using an all-optical laser-ultrasonic system. The finite element method was used to simulate propagating paths of defect-induced reflected and transmitted Rayleigh waves. It is observed that most Rayleigh waves with wavelengths less than the depth of the defect are reflected by the defect. A small part of the Rayleigh waves with wavelengths greater than the depth of the defect directly transmits through the bottom edge of the defect without acting on the left edge of the defect. Based on the simulation results, a three-step detection method of width and depth gauging of rectangular surface-breaking defects is proposed. In the first step, the pulsed laser and detection laser are irradiated on one side of the defect. In the second step, the sample is moved to a certain distance to ensure that both lasers reach the other side of the defect. In the third step, two lasers are irradiated on both sides of the defect. The width and depth of the defect are calculated according to the arrival time of the incident, reflected, and transmitted Rayleigh waves, as well as the movement distance of the sample. Experimental results are consistent with the reference-results measured by using a digital microscope. The proposed three-step detection method is proved to be feasible in simultaneous measurement of the width and depth of rectangular surface-breaking defects. Furthermore, it may be potentially useful for measuring other types of defect structures.
An exhaustive theoretical analysis of thermal effect inside bubbles for weakly nonlinear pressure waves in bubbly liquids
Authors: Kamei Takafumi , Kanagawa Tetsuya , Ayukai Takahiro
Published: May 2021

Weakly nonlinear propagation of pressure waves in initially quiescent compressible liquids uniformly containing many spherical microbubbles is theoretically studied based on the derivation of the Korteweg–de Vries–Burgers (KdVB) equation. In particular, the energy equation at the bubble–liquid interface [Prosperetti, J. Fluid Mech. 222, 587 (1991)] and the effective polytropic exponent are introduced into our model [Kanagawa et al., J. Fluid Sci. Technol. 6, 838 (2011)] to clarify the influence of thermal effect inside the bubbles on wave dissipation. Thermal conduction is investigated in detail using some temperature-gradient models. The main results are summarized as follows: (i) Two types of dissipation terms appeared; one was a well-known second-order derivative comprising the effect of viscosity and liquid compressibility (acoustic radiation) and the other was a newly discovered term without differentiation comprising the effect of thermal conduction. (ii) The coefficients of the KdVB equation depended more on the initial bubble radius rather than on the initial void fraction. (iii) The thermal effect contributed to not only the dissipation effect but also to the nonlinear effect, and nonlinearity increased compared with that observed by Kanagawa et al. (2011). (iv) There were no significant differences among the four temperature-gradient models for milliscale bubbles. However, thermal dissipation increased in the four models for microscale bubbles. (v) The thermal dissipation effect observed in this study was comparable with that in a KdVB equation derived by Prosperetti (1991), although the forms of dissipation terms describing the effect of thermal conduction differed. (vi) The thermal dissipation effect was significantly larger than the dissipation effect due to viscosity and compressibility.
Research on parametric modeling methods for vortex generators on flat plate
Authors: Zhao Zhenzhou , Chen Ming , Liu Huiwen , Wang Tongguang , Xu Bofeng
Published: May 2021

Vortex generators (VGs) are increasingly used on wind turbine blades to delay airflow separation. Small-size VGs substantially increase the numerical cost of simulations of large-size wind turbine blades with VGs. A parametric approach is typically used to replace physical VGs with an algorithm in computational fluid dynamics (CFD) research to address this problem. Nevertheless, the accuracy of the parametric approach is determined by the algorithm accuracy for calculating the maximum circulation of the VGs and the methods for modeling the trailing vortex profile. The main objective of this study is to propose a high-accuracy algorithm that describes the coupled responses of neighboring VGs using a series of modeling techniques. Since counter-rotating triangular VGs are typically used in the wind turbine industry, a pair of these devices mounted on a flat plate is investigated using a full-mesh model and a parametric model, considering different incoming velocities, VG incidence angles, and VG spacings. The research results show that the proposed algorithm for max circulation exhibits better agreement with the experimental data than existing algorithms that consider only one VG, and both model types show high consistency in all cases. The results indicate that the proposed parametric approach seems to be more suitable than the single VG algorithms for replacing physical VGs in CFD research of wind turbine blades equipped with VG arrays.
An automated multi-component gas adsorption system (MC GAS)
Authors: Shade Danny , Mounfield William P. , Huang Yi , Marszalek Bartosz , Walton Krista S.
Published: May 2021

The knowledge gap on adsorption of complex mixtures in the literature relative to single component data represents a persistent obstacle to developing accurate process models for adsorption separations. The collection of mixed gas adsorption data is an imminent need for improved understanding of the behavior of adsorbent systems in these diverse adsorption applications. Current approaches to understanding mixture adsorption using predictive theories based on pure component adsorption experiments often fail to capture the behavior of more complex, non-ideal systems. In this work, we present an automated volumetric instrument for the measurement of mixed gas adsorption isotherms. This instrument was validated by comparison to other in-house instruments and data available in the literature, and the binary adsorption measurements were found to be thermodynamically consistent. The automation of this instrument allows for rapid collection of high-quality mixture adsorption data.
Development of a filtered AXUV diode array for X-pinch soft x-ray spectra in the energy range of 1–10 keV
Authors: Ham Seunggi , Ryu Jonghyeon , Park Sungbin , Chung Kyoung-Jae , Ghim Y.-C. , Woo H. J. , Hwang Y. S.
Published: May 2021

We develop a filtered absolute extreme ultraviolet (AXUV) diode array to measure the time evolution of the soft x-ray spectrum in the energy range of 1–10 keV. AXUV–HS5, the detector, has a fast rise time of 0.7 ns, a wide energy detection range, and high accessibility. We use Geant4 simulations to design an appropriate filter set for flat-and-sharp virtual channels (VCs), where a filter with no spectral edge removes large tails of the response curves. A Levenberg–Marquardt (LM) method, sensitive to the expected spectral function, is improved to reliably generate a continuous radiation spectrum, by utilizing spectral information from the least-squares (LS) method that reconstructs a discrete spectrum with low spectral resolution directly from the VCs. We test the filtered AXUV diode array on an X-pinch device with a peak current of 140 kA at Seoul National University; the array with ten channels is installed in a vacuum chamber. For a two-wire 40 μm stainless steel X-pinch, x-ray power, radiation temperature, and the reconstructed x-ray spectrum are obtained from the filtered AXUV diode array by the combined LS–LM method.
Application of light scattering tomography for Si(111) samples
Authors: Szarvas T. , Pothorszky Sz. , Erdei D. , Molnár G. , Nádudvari Gy. , Almásy O. , Spindler Sz. , Kretschmer R. , Bauer S.
Published: May 2021

The detection of bulk micro-defects in Czochralski-grown silicon (Si) 〈100〉 wafers has significant importance in wafer quality control. Light Scattering Tomography (LST) is an industry standard technique for this purpose. This optical non-contact metrology requires destructive sample preparation: Samples have to be cleaved into half. One particular feature of the method is a dark field detection arrangement, which is achieved by separating the light detection part (microscope unit) from the illumination. Illumination is applied to the front surface of the sample, and the light scattered off of the defects is collected via the cleaved surface. The technique requires the perpendicularity of the cleaved surface to the front surface, which is fulfilled for Si(100) wafers. However, the nominally cleaved surface for Si(111) wafers is not perpendicular to the front surface but has an angle of 70.5°. This significant difference in cleavage results in the fact that Si(111) wafers cannot be measured by standard LST systems. Fortunately, the standard LST system can be modified by tilting the detection part under a proper angle allowing the measurements of Si(111) samples. In this article, we present this new technique in detail, showing the design and measurement capability of the new system. The measurement results are validated by a direct comparison to standard LST measurements on the same samples after proper sample preparation.
A co-axial electron gun to generate millimeter-wave RF using the two-stream instability
Authors: Neben D. , Bishofberger K. , Pavlenko V. , Yampolsky N.
Published: May 2021

A novel source for broadband millimeter-wave RF is being designed at Los Alamos National Laboratory utilizing the two-stream instability. This RF source offers the potential for consistent output power over a large bandwidth on a single device. The source is designed to use two co-axial electron beams coupled into solenoidal magnetic fields. This is accomplished using two cathodes independently modulated nested in each other. The electron beam energy from the innermost cathode will fall in the range between 15 and 20 keV with the beam energy from the outer cathode being 75%–95% of the inner beam energy. In order to efficiently match the beam from the outer cathode into the solenoidal magnetic field, shields are used around the cathodes to shape the electric field in the gun region to extend the electrostatic focal length of the beams for better coupling into the magnetic field. We present the design of electron guns and expected performance using Trak simulations.
Design and application of ion concentration polarization for preconcentrating charged analytes
Authors: Gholinejad Majid , Jabari Moghadam Ali , Phan Dinh-Tuan , Miri Amir K. , Mousavi Shaegh Seyed Ali
Published: May 2021

Micro/nanofluidic devices integrated with ion concentration polarization (ICP) phenomenon have been used to preconcentrate low-abundant molecules for separation and detection purposes. This work reviews ICP-based devices focused on electrokinetic fundamentals of ICP in microfluidics and related design factors. We discuss various designs of ICP devices and then provide insight on the role of design factors in ICP function. In addition, fabrication methods and relevant materials for making ICP devices and nanojunctions are explained. This work provides the most up-to-date applications of ICP with emphasis on active and passive methods in controlling and stabilizing streams of preconcentrated molecules to enhance the separation and detection efficiency in diagnostics, desalination, and electrodialysis.
Unidirectional invisibility of an acoustic multilayered medium with parity-time-symmetric impedance modulation
Authors: An Shuowei , Liu Tuo , Liang Shanjun , Gao He , Gu Zhongming , Zhu Jie
Published: May 2021

Non-Hermitian scattering systems respecting parity-time symmetry exhibit unidirectional invisibility or reflectionlessness at an exceptional point of the scattering matrix. In this study, we investigate the scattering properties of a one-dimensional acoustic parity-time-symmetric multilayered medium. Parity-time symmetry is defined by a spatial small-amplitude square-wave modulation of the medium parameters in the complex plane. Such a multilayered medium has been demonstrated to reach an exceptional point and support unidirectional invisibility for balanced real and imaginary part modulations of the refractive index. Through the analysis of interference within the medium, we show that the complex modulation of acoustic impedance instead of the refractive index governs the exceptional point of the scattering matrix and determines the occurrence of the unidirectional invisibility. This unidirectional invisibility is further investigated for more general cases of complex parameter distribution including unequal modulation amplitudes and rectangular wave modulation. Our study provides an intuitive physical picture of the occurrence of unidirectional invisibility induced by an exceptional point in acoustic wave systems. Moreover, this study could facilitate the design and practical realization of acoustic parity-time-symmetric structures.
Role of pre-existing dislocations on the shock compression and spall behavior in single-crystal copper at atomic scales
Authors: Ma Ke , Chen Jie , Dongare Avinash M.
Published: May 2021

Large-scale molecular dynamics simulations are carried out to investigate the role of pre-existing dislocation loops on the shock-induced deformation and spall behavior of single-crystal Cu microstructures. This study investigates the role of loading orientation and initial density of pre-existing dislocations on the decay behavior of the Hugoniot elastic limit (HEL) as well as the damage nucleation and growth behavior during spall failure of single-crystal Cu systems. The results suggest that the presence of pre-existing dislocation loops results in a decrease of the shock wave velocity and a substantial decay of the HEL values. The increased decay behavior is attributed to the decrease in the density of Shockley partials at the shock front as the shock wave travels through the metal as compared to defect-free initial single-crystal microstructures. Similarly, the presence of pre-existing dislocations is observed to result in increased values for the spall strength as compared to defect-free initial single-crystal microstructures wherein a higher density of dislocations results in the nucleation of a larger number of smaller voids. The decay behavior of the HEL values is observed to have a power–law dependence on the shock propagation distance with the initial dislocation density as a parameter. Similarly, a power–law dependence is also proposed for the number of voids nucleated at the spall plane with a dependence on the size of the voids as well as the initial density of dislocations. The evolution of microstructure (dislocation densities and voids) for the various loading orientations and initial densities of dislocations is discussed.
Effects of non-local competition on plankton–fish dynamics
Authors: Pal Mrinal Kanti , Poria Swarup
Published: May 2021

In ecology, the intra- and inter-specific competition between individuals of mobile species for shared resources is mostly non-local; i.e., competition at any spatial position will not only be dependent on population at that position, but also on population in neighboring regions. Therefore, models that assume competition to be restricted to the individuals at that position only are actually oversimplifying a crucial physical process. For the past three decades, researchers have established the necessity of considering spatial non-locality while modeling ecological systems. Despite this ecological importance, studies incorporating this non-local nature of resource competition in an aquatic ecosystem are surprisingly scarce. To this end, the celebrated Scheffer’s tri-trophic minimal model has been considered here as a base model due to its efficacy in describing the pelagic ecosystem with least complexity. It is modified into an integro-reaction–diffusion system to include the effect of non-local competition by introducing a weighted spatial average with a suitable influence function. A detailed analysis shows that the non-locality may have a destabilizing effect on underlying nutrient–plankton–fish dynamics. A local system in a stable equilibrium state can lose its stability through spatial Hopf and Turing bifurcations when strength of a non-local interaction is strong enough, which eventually generates a large range of spatial patterns. The relationship between a non-local interaction and fish predation has been established, which shows that fish predation contributes in damping of plankton oscillations. Overall, results obtained here manifest the significance of non-locality in aquatic ecosystems and its possible contribution to the phenomena of “spatial patchiness.”
Progress and challenges in ab initio simulations of quantum nuclei in weakly bonded systems
Authors: Rossi Mariana
Published: May 2021

Atomistic simulations based on the first-principles of quantum mechanics are reaching unprecedented length scales. This progress is due to the growth in computational power allied with the development of new methodologies that allow the treatment of electrons and nuclei as quantum particles. In the realm of materials science, where the quest for desirable emergent properties relies increasingly on soft weakly bonded materials, such methods have become indispensable. In this Perspective, an overview of simulation methods that are applicable for large system sizes and that can capture the quantum nature of electrons and nuclei in the adiabatic approximation is given. In addition, the remaining challenges are discussed, especially regarding the inclusion of nuclear quantum effects (NQEs) beyond a harmonic or perturbative treatment, the impact of NQEs on electronic properties of weakly bonded systems, and how different first-principles potential energy surfaces can change the impact of NQEs on the atomic structure and dynamics of weakly bonded systems.
Development and first operation of a cavity ring down spectroscopy diagnostic in the negative ion source SPIDER
Authors: Barbisan M. , Pasqualotto R. , Agnello R. , Pilieci M. , Serianni G. , Taliercio C. , Cervaro V. , Rossetto F. , Tiso A.
Published: May 2021

The neutral beam injectors of the ITER experiment will rely on negative ion sources to produce 16.7 MW beams of H/D particles accelerated at 1 MeV. The prototype of these sources was built and is currently operated in the SPIDER (Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma) experiment, part of the Neutral Beam Test Facility of Consorzio RFX, Padua. In the SPIDER, the H−/D− ion source is coupled to a three grid, 100 kV acceleration system. One of the main goals of the experimentation in SPIDER is to uniformly maximize the extracted current density; to achieve this, it is important to study the density of negative ions available in the proximity of the ion acceleration system. In SPIDER, line-integrated measurements of negative ion density are performed by a cavity ring down spectroscopy diagnostic. Its principle of operation is based on the absorption of the photons of a laser beam pulse by H−/D− photo-detachment; the absorption detection is enhanced by trapping the laser pulse in an optical cavity, containing the absorbing medium (i.e., negative ions). This paper presents and discusses the CRDS diagnostic setup in the SPIDER, including the first measurements of negative ion density, correlated with the main source parameters.
Measurement of axial phase difference of density fluctuations owing to spontaneously excited waves by using microwave reflectometer on GAMMA 10/PDX
Authors: Sekine R. , Hirata M. , Ikezoe R. , Jang S. , Kubota Y. , Kayano H. , Sugata K. , Aizawa T. , Noguchi D. , Kim D. , Sugimoto Y. , Matsuura R. , Yamazaki H. , Ichimura M. , Yoshikawa M. , Kohagura J. , Nakashima Y. , Ezumi N. , Sakamoto M.
Published: May 2021

In the GAMMA 10/PDX tandem mirror, plasma with strong ion-temperature anisotropy is produced by using the ion cyclotron range of frequency waves. This anisotropy of ion temperature causes several Alfvén-Ion-Cyclotron (AIC) waves to spontaneously excite in the frequency range just below the ion cyclotron frequency. In addition, difference-frequency (DF) waves are excited in the radial inner region of the plasma by wave–wave coupling among the AIC waves. The radial density profiles were measured at multi-axial positions using a frequency-modulation reflectometer with an axial array of microwave antennas, and an axial variation of the density was found to be significant. In addition, a relative phase difference of the DF wave between axially separated two points was first obtained by finely choosing the probing frequency of the reflectometers with a maximum coherence used as a measure, indicating that the DF wave is a propagating wave, while the pump AIC waves are standing waves in the axial region of measurement.
Global stability of noncritical traveling front solutions of Fisher-type equations with degenerate nonlinearity
Authors: Wang Yang , Cao Xinyue , Ma Zhaohai , Li Xiong
Published: May 2021

In this paper, for degenerate n-degree Fisher-type equations, we discuss the stability of their traveling front solutions with noncritical speeds. In fact, when the initial perturbations around these noncritical traveling front solutions are in some weighted Banach spaces, we have proved that these solutions are globally exponentially stable in the form of (1+t)13e−νt for ν ∈ (0, 1) via L1-energy estimates, L2-energy estimates, and the weighted energy method. Furthermore, by Fourier transform and the weighted energy method, we will prove that traveling front solutions with noncritical speeds are also globally exponentially stable in the form of t−12e−νt for some positive constant ν when the initial perturbations around these solutions are in some weighted Sobolev spaces. Our conclusions extend the local stability of noncritical traveling front solutions into the global case and also give some novel forms of exponential stability of these solutions.
Oxygen and vacancy defects in silicon. A quantum mechanical characterization through the IR and Raman spectra
Authors: Platonenko Alexander , Colasuonno Fabio , Gentile Francesco Silvio , Pascale Fabien , Dovesi Roberto
Published: May 2021

The Infrared (IR) and Raman spectra of various defects in silicon, containing both oxygen atoms (in the interstitial position, Oi) and a vacancy, are computed at the quantum mechanical level by using a periodic supercell approach based on a hybrid functional (B3LYP), an all-electron Gaussian-type basis set, and the Crystal code. The first of these defects is VO: the oxygen atom, twofold coordinated, saturates the unpaired electrons of two of the four carbon atoms on first neighbors of the vacancy. The two remaining unpaired electrons on the first neighbors of the vacancy can combine to give a triplet (Sz = 1) or a singlet (Sz = 0) state; both states are investigated for the neutral form of the defect, together with the doublet solution, the ground state of the negatively charged defect. Defects containing two, three, and four oxygen atoms, in conjunction with the vacancy V, are also investigated as reported in many experimental papers: VO2 and VOOi (two oxygen atoms inside the vacancy, or one in the vacancy and one in interstitial position between two Si atoms) and VO2Oi and VO22Oi (containing three and four oxygen atoms). This study integrates and complements a recent investigation referring to Oi defects [Gentile et al., J. Chem. Phys. 152, 054502 (2020)]. A general good agreement is observed between the simulated IR spectra and experimental observations referring to VOx (x = 1–4) defects.
Novel high voltage polymer insulators using computational and data-driven techniques
Authors: Kamal Deepak , Tran Huan , Kim Chiho , Wang Yifei , Chen Lihua , Cao Yang , Joseph V. Roshan , Ramprasad Rampi
Published: May 2021

One of the key bottlenecks in the development of high voltage electrical systems is the identification of suitable insulating materials capable of supporting high voltages. Under high voltage scenarios, conventional polymer based insulators, which are one of the popular choices of insulators, suffer from the drawback of space charge accumulation, which leads to degradation in desirable electronic properties and facilitates dielectric breakdown. In this work, we aid the development of novel polymers for high voltage insulation applications by enabling the rapid prediction of properties that are correlated with dielectric breakdown, i.e.,the bandgap (Egap) of the polymer and electron injection barrier (Φe) at the electrode–insulator interface. To accomplish this, density functional theory based methods are used to develop large, chemically diverse datasets of Φe and Egap. The deviation of the computed properties from experimental observations is addressed using a statistical technique called Bayesian calibration. Furthermore, to enable rapid estimation of these properties for a large set of polymers, machine learning models are developed using the created dataset. These models are further used to predict Egap and Φe for a set of 13k previously known polymers. Polymers with high values of these properties are selected as potential high voltage insulators and are recommended for synthesis. Finally, the models developed here are deployed at www.polymergenome.org to enable the community use.
Evolution of solid–liquid interface in bottom heated cavity for low Prandtl number using lattice Boltzmann method
Authors: Hasan Md Shahzad , Saha Sandip K.
Published: May 2021

The influence of natural convection cells on heat transfer and the evolution of melt interface is studied for low Prandtl number fluid (Pr = 0.025) in phase-change Rayleigh–Benard convection using the lattice Boltzmann method. The thermal lattice Boltzmann model is used to evaluate the effect of Rayleigh number (Ra = 6708, 11 708, and 21 708) and cavity aspect ratio (γ = 0.062 5, 0.125, 0.25, 0.5, and 1) on the onset of convection, number of convection cells, and Nusselt number in the classical Rayleigh–Benard convection. The modified equilibrium distribution function-based thermal lattice Boltzmann model is applied to evaluate the effect of Stefan number (Ste = 0.025, 0.05, and 0.1) in the phase change Rayleigh–Benard convection. Distinct flow configurations depend on the Rayleigh number, aspect ratio, and Stefan number. The number of convection cells follows an inverse relation with the aspect ratio. Nusselt number increases with decreasing cavity aspect ratio and increasing Rayleigh number in the classical Rayleigh–Benard convection. With the variation in the aspect ratio based on the melt layer height during melting of phase change material, the number of convection cells changes resulting in the change in the evolution of the melt interface and convective heat transfer. Melting in a cavity of aspect ratio less than 0.5, the evolution of melt interface remains symmetrical. For an aspect ratio greater than 0.5, the interface evolution becomes unsymmetrical depending on the transition to single convection cell-dominated heat transfer.
Electronic growth of Pd(111) nanostructures on MoS2
Authors: Kidd Timothy E. , Scott Skylar , Roberts Sophie , Carlile Ryan , Lukashev Pavel V. , Stollenwerk Andrew J.
Published: May 2021

Quantum confinement effects can induce the formation of discrete nanostructures with well-defined preferred heights in thin metallic films. In most systems, such electronic growth modes are weak and limited to cryogenic conditions. Recently, however, we have discovered that metals grown upon van der Waals surfaces can exhibit electronic growth at, or even above, room temperature to spontaneously form well-defined and highly stable nanostructures. Here, we explore the initial stages of room temperature deposition of Pd onto MoS2. We found that, even for minimal thicknesses, Pd spontaneously formed discrete islands with three atomic layers. The islands maintained this preferred height for nominal coverages below three atomic layers. At higher coverages, the preferred height switched abruptly to six atomic layers. Unlike previous studies using Au or Ag, the islands did not increase laterally with coverage but rather increased in number with lateral size remaining about the same. The preferred heights in Pd/MoS2 correlate to the Pd Fermi surface topography and are also consistent with thicknesses showing minima in the density of states at the Fermi level, which suggest that the electronic growth modes are the driving factors in these self-assembled Pd nanostructures. The Pd system shows a preference for island nucleation compared to Au and Ag which grow laterally with increasing coverage. This is likely related to differences in bonding at the interface as Pd is typically much more reactive than Ag or Au.
Theoretical and experimental analyses of a legged piezoelectric bending actuator with shoe soles made of polyimide composites
Authors: Zhu Pancheng , Peng Hanmin , Zhao Gai , Chen Ni
Published: May 2021

Friction materials form a critical component of piezoelectric actuators, and wear of the material affects output and service life of the actuator. This paper examines the influence of polyimide (PI) composites when used as a friction material on the performance of a legged piezoelectric bending actuator. We design and manufacture demountable shoe soles, made of a novel PI-based friction material, for an actuator. A Coulomb friction model is also established to determine the behavior resulting from contact-induced friction between the surface and the actuator. Reciprocating wear tests involving an insulation rubber pad against phosphor bronze and PI composites as friction materials yielded average friction coefficients of 0.21 and 0.28, respectively. We also found that PI composites have higher wear resistance than phosphor bronze, with a specific wear rate of 1.36 × 10−4 mm3/N m. The results of experiments and simulations indicate that the shoe soles made of PI composites reduced the actuator’s driving frequency and vibrational amplitude, but they did not affect the principle of locomotion of the actuator. Furthermore, the operational stability of the actuator improved by 46.8% by using the demountable shoe soles made of PI composites, albeit at the cost of its velocity and load capacity. This work has guiding significance for the design and selection of friction materials for piezoelectric actuators.
Solitary structure formation and self-guiding of electromagnetic beam in highly degenerate electron plasma
Authors: Berezhiani V. I. , Osmanov Z. N. , Mahajan S. M. , Mikeladze S. V.
Published: May 2021

In the present paper, we consider the nonlinear interaction of high frequency intense electromagnetic beam with degenerate electron plasmas. In a slowly varying envelop approximation, the beam dynamics is described by the couple of nonlinear equations for the vector and scalar potentials. Numerical simulations demonstrate that for an arbitrary level of degeneracy the plasma supports existence of axially symmetric 2D solitons which are stable against small perturbations. The solitons exist if the power trapped in the structures, being the growing function of soliton amplitude, is above a certain critical value but below the value determining by electron cavitation. The robustness of obtained soliton solutions was verified by simulating the dynamics of initial Gaussian beams with parameters close to the solitonic ones. After a few diffraction lengths, the beam attains the profile close to the profile of the ground state soliton and propagates for a long distance without detectable distortion. The simulations have been performed for the input Gaussian beams with parameters far from ground state solutions. It is shown that the beam parameters are oscillating near the parameters of the ground soliton solution and thus the formation of oscillating waveguide structures takes place.
High voltage microsecond pulse generators with highly effective energy recuperation in cases of sharp changes in load impedance
Authors: Korotkov S. V. , Aristov Y. V. , Korotkov D. A.
Published: May 2021

An experimental generator of microsecond pulses with an output current amplitude of ∼1 kA and an output voltage amplitude of ∼1 kV was developed. The generator is able to operate on a load whose electrical resistance changes significantly during operation. Under these conditions, the generator ensures high stability of output pulse energy and effectively uses energy that is reflected from the load. Using this generator, a high voltage generator with an output voltage pulse amplitude of ∼30 kV was developed. The high voltage generator is designed to be used in electric discharge technologies. The results of the experiments are given in which the high voltage generator produced discharges in water at a repetition rate of 500 Hz. The amplitude of the discharge current pulse was ∼600 A, and the pulse rise time was ∼150 ns.
Flow-induced vibration of a trapezoidal cylinder at low Reynolds numbers
Authors: Wang Shubiao , Cheng Wenming , Du Run , Wang Yupu , Chen Qingrong
Published: May 2021

This paper discusses the flow-induced vibration of a freely vibrating trapezoidal cylinder with a mass ratio of 10 at low Reynolds numbers (Re = 60–250). Over this range of the Reynolds number, we discuss the inflow and transverse amplitudes, frequency ratios, hydrodynamic forces, phase differences, and vortex modes. Comparing to square/circular cylinders with the same flow conditions, responses of the trapezoidal cylinder are much different. In both the vortex-induced vibration (VIV) and galloping regimes, double rise-up of the amplitudes and hydrodynamics forces is observed with respect to Re, as well as the two lock-ins for the frequency ratios. The phase differences and vortex modes in the wake are also found to be different from the square/circular cylinders. Thus, seven flow branches are identified, i.e., the initial branch, upper branch, lower branch, desynchronization region, initial galloping, upper galloping, and high galloping. Then, in order to interpret these branches, the evolutions of vortex formation and shedding in the wake are analyzed. It appears that the asymmetry of the trapezoidal cylinder to the inflow is the direct cause. In addition, a small degree of hysteresis is observed in the VIV regime and a larger degree is observed in the galloping regime.
Photoluminescence tuning of stacked submonolayer (SML) InAs nanostructures across the 2D to 3D transition
Authors: Roca R. C. , Kamiya I.
Published: May 2021

We report the precise and broadband tuning of the photoluminescence (PL) from a stacked submonolayer (SML) InAs nanostructure across the 2D to 3D transition. We have recently reported the growth of stacked SML InAs nanostructures by molecular beam epitaxy, which leads to the formation of two distinct types of SML nanostructures: 2D islands and 3D structures. In contrast to the well-investigated transition in Stranski–Krastanov (SK) growth of InAs nanostructures, the transition in SML growth is still largely unexplored. Here, the properties of three- and four-stack SML InAs nanostructures are investigated by PL measurements and are interpreted in the context of the transition. At the transition, a characteristic change in the PL is observed, while the controllability of the PL is maintained across the transition. Furthermore, control of the transition itself is possible by changing the SML stack configuration. A brief comparison with the SK transition is also discussed.
Interplay between magnetic moment and magnetocrystalline anisotropy in tetragonally distorted galfenol films
Authors: C. de Oliveira R. , Z. C. Paes V. , H. Mosca D. , Varalda J.
Published: May 2021

Magnetic properties of Fe100−xGax (x = 15 and 30) epitaxial thin films on GaAs(001) substrates were studied experimentally and theoretically. The samples grown by molecular beam epitaxy under certain conditions adopt body-centered structures with tetragonal distortion along the film normal with a c/a ratio varying from 1.014 to 1.036. The density functional theory (DFT) calculations were performed for different (c/a) ratio values and Ga contents. DFT results showed that Fe atoms placed at the first neighborhood of Ga positions present a much stronger distortion in the local exchange-correlation field than second neighbor Fe atoms. The formation of non-bonding Fe 3d states in the minority spin sub-band and the predominance of hybridization of Ga 4p states with Fe 4p states due to Ga content cause this magnetic behavior. The in-plane magnetic anisotropies are explained in terms of the exchange-correlation field isosurfaces. As a result of that, the global magnetic anisotropy can be described as cubic magnetocrystalline mixed with sixfold anisotropy.
Effect of out-of-plane strain on the phonon structures and anharmonicity of twisted multilayer graphene
Authors: Zeng Yu-Jia , Feng Ye-Xin , Tang Li-Ming , Chen Ke-Qiu
Published: May 2021

Twisted bilayer and multilayer two-dimensional materials linked by van der Waals interactions exhibit various unique physical properties. The phonon properties of such systems are of great importance, but have not been explored in detail. In this work, we use a hybrid neural-network potential to systematically investigate the evolution of the phonon structure of twisted multilayer graphene under out-of-plane strain. With increasing out-of-plane strain, the evolution of the phonon structure of the moiré superlattice exhibits different behavior from that of AA and AB stacked multilayer graphene. Meanwhile, with twisting of the interlayer, a higher Grüneisen parameter and a lower phonon group velocity can be obtained. A possible method is revealed by which phonon anharmonic scattering in stacked multilayer graphene could be enhanced by varying the twist angle in combination with out-of-plane strain. Our work shows that the application of out-of-plane strain can serve as an effective way to amplify the effect of twist angle on phonon structures of twisted multilayer two-dimensional systems, with potential application to thermoelectric and thermal logical devices.