bluuebunny/crossref_metadata_2025 huggingface dataset:
Large pneumatocele as a rare complication in SARS-CoV-2 infection of the lung
Authors: Gillissen Adrian , Zimmermann Thomas , Clasen Stephan
Published: May 2022

In this paper, we present a case of SARS-CoV2-Virus a non-vaccinated 54-year-old male admitted
with COVID-19 pneumonia and respiratory insufficiency requiring high-flow oxygen
supplementation. CT-scan of the lung revealed multifocal bilateral ground-glass opacities and
– as a rare complication – a large pneumatocele in the middle of the posterior part of the
left lower lobe. In order to treat the pneumatocele, a 10 F was placed into the cavity. The
resulting pneumothorax was successfully treated with a 20 F chest tube over a 9-day period.
The pneumatocele shrank only slightly. This case demonstrates a unique radiologic finding in
COVID-19, which is likely the result of severe inflammation secondary to SARS-CoV-2 including
an unfruitful attempt at depressurisation.
Syndesmosenverletzungen – Anatomie, Verletzungsmuster und Diagnostik
Authors: Walther Markus , Hörterer Hubert , Gottschalk Oliver
Published: May 2022

Viele Verletzungen der Außenbänder des Sprunggelenks heilen ohne langfristige Folgen. Ist aber die Syndesmose mit verletzt, drohen spätere Komplikationen. Eine gründliche Diagnose ist daher unabdingbar.
Belastung von Betroffenen mit MRKH-Syndrom: Effekt einer Intervention
zur Unterstützung bei Neovagina-Anlage
Authors: Schäffeler Norbert , Beckmann Julia , Schenk Bernadette , Schöller Dorit , Wallwiener Diethelm , Enck Paul , Teufel Martin , Zipfel Stephan , Rall Katharina , Brucker Sara
Published: May 2022

Die Diagnose des Mayer-Rokitansky-Küster-Hauser Syndroms (MRKHS), eine
seltene Variante der weiblichen Geschlechtsentwicklung, wird meist in der
Pubertät gestellt. Die Verunsicherung im Selbstbild, die
Unmöglichkeit schwanger zu werden führen häufig zu
deutlicher Belastung. Obwohl eine psychosomatische Begleitung in der Literatur
konsistent empfohlen wird gibt es bislang nur wenige Studien zu psychischen
Aspekten von MRKHS. Ziel dieser Studie ist es, die Lebensqualität und
Belastung von Frauen mit MRKHS bei der operativen Anlage einer Neovagina zu
untersuchen und andererseits Effekte einer Intervention zur Vorbereitung und
Unterstützung während der Behandlung zu evaluieren. Methoden An
einem überregionalen Zentrum zur Neovaginaanlage wurde im Rahmen einer
explorativen quasi-experimentellen Prä-Post-Untersuchung allen
Patientinnen eine psychosomatische Intervention angeboten (Interventionsgruppe
IG, n=23) und vor Operation (t0) sowie sechs Monate danach (t1) die
sexuelle Funktion (FSFI), psychische Belastung (PHQ-D) und gesundheitsbezogene
Lebensqualität (SF-12) erhoben. Diese wurden mit den Daten einer zuvor
sowie im Anschluss an den Interventionszeitraum erhobenen Stichprobe verglichen
(Vergleichsgruppe VG, n=30). Ergebnisse Während die
körperliche Lebensqualität (SF-12) beider Gruppen zu beiden
Zeitpunkten unauffällig war, zeigte sich eine signifikante
Beeinträchtigung in der psychischen Lebensqualität. Beide
Gruppen (IG, VG) verbesserten sich von t0 zu t1 in ihrer sexuellen Funktion
(FSFI) und zeigten niedrigere Depressionswerte (PHQ-D). Die im Rahmen dieser
Studie entwickelte Kurzintervention wurde von den Betroffenen gut akzeptiert und
als hilfreich bewertet. Diese subjektiv empfundene Wirksam-keit der Intervention
zeigte sich jedoch nicht durch eine Verbesserung auf der
Lebensqualitätsskala (SF-12) und Depressionsskala (PHQ-D).
Schlussfolgerung Die Betroffenen zeigen eine deutliche, klinisch relevante
Belastung (SF-12), die sich aber nicht in Form psychischer Komorbidität
(PHQ-D) abbildet. Diese scheinbare Diskrepanz weist auf psychisch stabile Frauen
mit akuter Belastung durch die Diagnose der Variante der Geschlechtsentwicklung
hin. Für sie scheint ein niederschwelliges Unterstützungsangebot
mit supportivem Charakter zur Begleitung während der operativen
Behandlung notwendig und hilfreich. Die rekonstruktive Therapie zur Anlage einer
Neovagina scheint die psychische Lebensqualität positiv zu beeinflussen.
Dass eine Schwangerschaft aufgrund des fehlenden Uterus weiterhin nicht
möglich ist könnte ein Grund für das Nicht-Erreichen der
Lebensqualität der Durchschnittsbevölkerung sein.
Consonant Enhancement Effects on Speech Recognition of Hearing-Impaired Children
Authors: Smith Lynn Z. , Levitt Harry
Published: May 2022

Differences in gain (enhancement, in dB) required to optimize the consonant/vowel intensity ratio in nonsense syllables were determined for stops and fricatives, both voiced and voiceless, in 12 children with congenital moderate to severe sensorineural hearing loss. The test stimuli were vowel/consonant nonsense syllables with various levels of enhancement ranging from 0 dB (for the unprocessed stimulus) to 24 dB of gain, in steps of 3 or 6 dB. Results showed that significant improvements in consonant recognition can be obtained with individualized adjustment of consonant amplitude for children as young as 5 years of age.

Abbreviations: CE = consonant enhacement, CVR = consonant/vowel intensity ratio, NST = Nonsense Syllable Test
Comparison of Air-Conduction and Bone-Conduction Hearing Thresholds for Pure Tones and Octave-Band Filtered Sound Effects
Authors: Abouchacra Kim S. , Letowski Tomasz
Published: May 2022

The purpose of this study was to measure air-conduction (AC) and bone-conduction (BC) hearing thresholds with pure-tone and filtered sound effect stimuli using standard audiometric equipment. A group of 20 young, normal-hearing listeners participated in the study. Pure-tone stimuli were 250, 500, 1000, 2000, and 4000 Hz. Sound effect stimuli were 12 natural sounds that were spectrally limited to an octave bandwidth centered at either 250, 500,1000, 2000, or 4000 Hz. The AC and BC detection thresholds were measured using a clinical audiometer (Madsen Orbiter 922) with a B-71 bone oscillator and TDH-50 earphones. Results indicated that detection thresholds for the pure-tone and corresponding octave-band sound effect stimuli were within 3 to 4 dB of each other for both AC and BC testing. The findings support the notion that octave-filtered sound effects are a viable alternative to pure-tone stimuli for use in audiology clinics.
Overcoming political risk in developing economies through non-local debt
Authors: Müllner Jakob , Dorobantu Sinziana
Published: May 2022

Infrastructure investments are essential in generating sustainable development but also involve extensive political risk and potentially unreliable local partners. We study how banks financing such investments use syndication with non-local partners to pool economic leverage from trade, investment, and FDI. Using 5928 of the world’s largest infrastructure and energy projects in 160 countries between 2000 and 2013, we show that banks pool economic leverage from banks with dominant economic ties to the host country and from supranational institutions. Our findings contribute three distinct elements to the nonmarket strategy literature. First, they highlight the strategic value of macro-economic dependencies in the management of political risk. Second, our study positions non-local alliances as an alternative to alliance partners in the host-country context. Third, our study is the first in IB to acknowledge the value of debt-side pooling of leverage. From a practical and policy point of view, our findings suggest that practitioners and policymakers should strive to improve the efficiency of debt syndication across borders as a means of mitigating political risk and encouraging infrastructure investment.
Excitation symmetry and origin of dark states in π-conjugated molecules
Authors: Xie Jun , Sheng Weidong
Published: May 2022

Utilizing the exact diagonalization method, the optical absorption spectra of two π-conjugated molecules, anthracene and pyrene, are calculated in various dielectric environments. In a confined quantum system with an anisotropic geometry, it is commonly believed that the first excited state is localized along the elongated direction. In the meantime, the dipole approximation says that the transitions to those states localized along the elongated direction shall generally have higher intensities. In this work we report that anthracene and pyrene would respectively fail these intuitive expectations. It is found that the first active transition in anthracene is always polarized along its short axis direction. For pyrene, it is revealed that the transition of the highest intensity is the one polarized along the short axis direction of the molecule. Furthermore, the first excited state in either anthracene or pyrene is often found to be optically inactive, which is successfully attributed to the short-range interactions by examining the energy spectra in varying interaction environments.
Theoretical study of hydrogen-bond interactions of CO2 in organic absorbent 1,3-diphenylguanidine
Authors: Wang Yiqiu , Gao Han , Li Yajing , Zhang Igor Ying , Xia Fei
Published: May 2022

Carbon capture and storage technology have been rapidly developed to reduce the carbon dioxide (CO2) emission into the environment. It has been found that the amine-based organic molecules could absorb CO2 efficiently and form the bicarbonate salts through hydrogen-bond (H-bond) interactions. Recently, the aqueous 1,3-diphenylguanidine (DPG) solution was developed to trap and convert CO2 to valuable chemicals under ambient conditions. However, how the DPG molecules interact with CO2 in an aqueous solution remains unclear. In this work, we perform molecular dynamics simulations to explore the atomistic details of CO2 in the aqueous DPG. The simulated results reveal that the protonated DPGH+ and the bicarbonate anions prefer to form complexes through different H-bond patterns. These double H-bonds are quite stable in thermodynamics, as indicated from the accurate density functional theory calculations. This study is helpful to understand the catalytic mechanism of CO2 conversion in the aqueous DPG.
Direct observation of singlet ππ∗ and nπ* equilibrium state in 2-amino-1,3,5-triazine solution
Authors: Li Xiuhua , Wang Xueli , Lv Meng , Zhou Zhongneng , Pan Haifeng , Chen Jinquan
Published: May 2022

1,3,5-Triazine molecules represent a class of molecules that may have been prebiotic information carriers in a primordial soup in early Earth and their excited state dynamics has received attention in recent years. In our previous study, one component with lifetime longer than 100 ps was discovered in 2-amino-1,3,5-trainzine (2-AT), but its nature has not been revealed. In this study, excited state dynamics of 2-AT is studied in different solvents by using femtosecond time-resolved transient absorption and fluorescence up-conversion spectroscopy. Interestingly, an equilibrium state consisting of the bright ππ∗ and dark nπ∗ states in 2-AT is directly observed in aqueous solution and its dynamics is solvent sensitive. The whole picture of the excited state deactivation mechanism of 2-AT is proposed based on our spectroscopy results.
A novel air microfluidics-enabled soft robotic sleeve: Toward realizing innovative lymphedema treatment
Authors: Gao Run Ze , Mai Vivian Ngoc Tram , Levinski Nicholas , Kormylo Jacqueline Mary , Murdock Robin Ward , Dickerson Clark R. , Ren Carolyn L.
Published: May 2022

A proof of concept of a novel air microfluidics-enabled soft robotic sleeve to enable lymphedema treatment is presented. Compression sleeves represent the current, suboptimal standard of care, and stationary pumps assist with lymph drainage; however, effective systems that are truly wearable while performing daily activities are very scarce. This problematic trade-off between performance and wearability requires a new solution, which is addressed by an innovative microfluidic device. Its novelty lies in the use of light, small, and inexpensive air microfluidic chips (35 × 20 × 5 mm3 in size) that bring three major advantages compared to their traditional counterparts. First, each chip is designed with 16 fluidic channels with a cross-sectional area varying from 0.04 to 1 mm2, providing sequential inflation and uniform deflation capability to eight air bladders, thereby producing intentional gradient compression to the arm to facilitate lymph fluid circulation. The design is derived from the fundamentals of microfluidics, in particular, hydraulic resistance and paths of least resistance. Second, the air microfluidic chip enables miniaturization of at least eight bulky energy-consuming valves to two miniature solenoid valves for control increasing wearability. Third, the air microfluidic chip has no moving parts, which reduces the noise and energy needed. The cost, simplicity, and scale-up potential of developing methods for making the system are also detailed. The sequential inflation, uniform deflation, and pressure gradient are demonstrated, and the resulted compression and internal air bladder pressure were evaluated. This air microfluidics-enabled sleeve presents tremendous potential toward future improvements in self-care lymphedema management.
Stochastic modeling of plasma fluctuations with bursts and correlated noise in TCABR
Authors: Zurita M. , Hernandez W. A. , Crepaldi C. , Pereira F. A. C. , Guimarães-Filho Z. O.
Published: May 2022

Blob-like filamentary structures are omnipresent in magnetized plasmas. Their transport deteriorates the particle confinement and may damage plasma-facing components of future fusion devices. In local measurements of density, these turbulent structures are seen as high-amplitude bursts, and, since the last decade, a stochastic pulse train model (SPTM) has been developed to describe these locally measured signals. The SPTM, which is also known as a filtered Poisson process, models plasma fluctuations as a superposition of pulses plus a background with Gaussian noise. In the present article, a fitting method for this model is introduced, considering a mixture of dynamical and observational noise. The proposed method exploits the fact the model parameters can be fitted in steps, using first the signal characteristic function, then the conditionally averaged burst, and finally the frequency spectrum. By employing this fit, we compare predictions of the model for ion saturation current measurements made with a Langmuir probe mounted in the outboard mid-plane region of the TCABR tokamak. The model is able to highlight a series of differences between the plasma edge and scrape-off layer. Furthermore, radial profiles of the SPTM parameters reveal a relation between the signal kurtosis, the intermittency of the pulses, and background parameters. Also, a linear increase in the pulse duration was found with the position. Finally, by using recurrence quantification analysis, we show evidence that the mixture of dynamical and measurement noise may be more accurate than just one of the two to describe the dynamic behavior of density fluctuations in TCABR.
Characterizing velocity–space signatures of electron energization in large-guide-field collisionless magnetic reconnection
Authors: McCubbin Andrew J. , Howes Gregory G. , TenBarge Jason M.
Published: May 2022

Magnetic reconnection plays an important role in the release of magnetic energy and consequent energization of particles in collisionless plasmas. Energy transfer in collisionless magnetic reconnection is inherently a two-step process: reversible, collisionless energization of particles by the electric field, followed by collisional thermalization of that energy, leading to irreversible plasma heating. Gyrokinetic numerical simulations are used to explore the first step of electron energization, and we generate the first examples of field–particle correlation signatures of electron energization in 2D strong-guide-field collisionless magnetic reconnection. We determine these velocity space signatures at the x-point and in the exhaust, the regions of the reconnection geometry in which the electron energization primarily occurs. Modeling of these velocity–space signatures shows that, in the strong-guide-field limit, the energization of electrons occurs through bulk acceleration of the out-of-plane electron flow by the parallel electric field that drives the reconnection, a non-resonant mechanism of energization. We explore the variation of these velocity–space signatures over the plasma beta range 0.01≤βi≤1. Our analysis goes beyond the fluid picture of the plasma dynamics and exploits the kinetic features of electron energization in the exhaust region to propose a single-point diagnostic, which can potentially identify a reconnection exhaust region using spacecraft observations.
Frequency-tunable Kerr-free three-wave mixing with a gradiometric SNAIL
Authors: Miano A. , Liu G. , Sivak V. V. , Frattini N. E. , Joshi V. R. , Dai W. , Frunzio L. , Devoret M. H.
Published: May 2022

Three-wave mixing is a key process in superconducting quantum information processing, being involved in quantum-limited amplification and parametric coupling between superconducting cavities. These operations can be implemented by superconducting nonlinear asymmetric inductive element (SNAIL)-based devices that present a Kerr-free flux-bias point where unwanted parasitic effects, such as Stark shift, are suppressed. However, with a single flux-bias parameter, these circuits can only host one Kerr-free point, limiting the range of their applications. In this Letter, we demonstrate how to overcome this constraint by introducing the gradiometric SNAIL, a doubly flux biased superconducting circuit in which both effective inductance and Kerr coefficient can be independently tuned. Experimental data show the capability of the gradiometric SNAIL to suppress the Kerr effect in a three-wave mixing parametric amplifier over a continuum of flux bias points corresponding to a 1.7 GHz range of operating frequencies.
Influences of gas pressure and applied voltage on electron beam generated by triggered pseudospark discharge
Authors: Shen Saikang , Yan Jiaqi , Sun Guoxiang , Ding Weidong
Published: May 2022

Used widely in microwave devices and material processing, triggered pseudospark discharge can generate an electron beam, the adjustability of which is affected greatly by the working gas pressure and the applied voltage of the pseudospark discharge. This paper reports the development of an electron-beam source based on a single-gap triggered pseudospark discharge device. Its working performance, as measured by the peak beam current, charge quantity, and pulse width, was studied experimentally, and the results showed that the peak beam current increased initially and then decreased with increasing gas pressure. This was because the beam current was limited by the low plasma density at low pressures, while the electron scattering and ion neutralization during drift decreased the beam current at high pressures. The pulse width of the beam current was consistent with that of the loop current and was determined by the damping coefficient of the discharge circuit. With increasing gas pressure, the pulse width decreased gradually. When the gas pressure was constant, the peak beam current increased significantly with increasing applied voltage because of the enhanced electron-emission current and weakened electron scattering. The charge quantity of the beam current also increased with increasing applied voltage, but the pulse width decreased slightly. Based on the above results, this paper also reports qualitative analysis of the change of the discharge process corresponding to the variation of the electron-beam parameters with gas pressure and applied voltage.
Filament dynamics in vertical confined chemical gardens
Authors: Rocha Luis A. M. , Cartwright Julyan H. E. , Cardoso Silvana S. S.
Published: May 2022

When confined to a Hele-Shaw cell, chemical gardens can grow as filaments, narrow structures with an erratic and tortuous trajectory. In this work, the methodology applied to studies with horizontal Hele-Shaw cells is adapted to a vertical configuration, thus introducing the effect of buoyancy into the system. The motion of a single filament tip is modeled by taking into account its internal pressure and the variation of the concentration of precipitate that constitutes the chemical garden membrane. While the model shows good agreement with the results, it also suggests that the concentration of the host solution of sodium silicate also plays a role in the growth of the structures despite being in stoichiometric excess.
A high throughput microfluidic system with large ranges of applied pressures for measuring the mechanical properties of single fixed cells and differentiated cells
Authors: Li Xiao , Jin Yiteng , Shi Jialin , Sun Xiaoqiang , Ouyang Qi , Luo Chunxiong
Published: May 2022

The mechanical properties of cells are of great significance to their normal physiological activities. The current methods used for the measurement of a cell’s mechanical properties have the problems of complicated operation, low throughput, and limited measuring range. Based on micropipette technology, we designed a double-layer micro-valve-controlled microfluidic chip with a series of micropipette arrays. The chip has adjustment pressure ranges of 0.03–1 and 0.3–10 kPa and has a pressure stabilization design, which can achieve a robust measurement of a single cell's mechanical properties under a wide pressure range and is simple to operate. Using this chip, we measured the mechanical properties of the cells treated with different concentrations of paraformaldehyde (PFA) and observed that the viscoelasticity of the cells gradually increased as the PFA concentration increased. Then, this method was also used to characterize the changes in the mechanical properties of the differentiation pathways of stem cells from the apical papilla to osteogenesis.
Perimeter leakage of face masks and its effect on the mask's efficacy
Authors: Solano Tomas , Ni Chuanxin , Mittal Rajat , Shoele Kourosh
Published: May 2022

Recent studies have shown that the effectiveness of the face masks depends not only on the mask material but also on their fit on faces. The mask porosity and fit dictate the amount of filtered flow and perimeter leakage. Lower porosity is usually associated with better filtration; however, lower porosity results in higher perimeter leakage. The resulting leakage jets generated from different types of faces and different mask porosities are of particular interest. Direct numerical simulations of the flow dynamics of respiratory events while wearing a face mask can be used to quantify the distribution of the perimeter leaks. Here, we present a novel model for porous membranes (i.e., masks) and use it to study the leakage pattern of a fabric face mask on a realistic face obtained from a population study. The reduction in perimeter leakage with higher porosities indicates that there would be an optimal porosity such that the total leakage and maximum leakage velocities are reduced. The current model can be used to inform the quantification of face mask effectiveness and guide future mask designs that reduce or redirect the leakage jets to limit the dispersion of respiratory aerosols.
Effect of free-stream turbulence properties on different transition routes for a zero-pressure gradient boundary layer
Authors: Dotto A. , Barsi D. , Lengani D. , Simoni D. , Satta F.
Published: May 2022

The natural and bypass routes to boundary-layer transition to turbulence are traditionally investigated independently in fluid mechanics applications. Nevertheless, in certain flow regimes both mechanisms could coexist and interact. In this work, large-eddy simulations (LES) were performed for a zero-pressure gradient boundary layer developing over a flat plate to investigate the transition mechanism for variable free-stream turbulent properties. Four different combinations of turbulence intensity and integral length scale were analyzed, and two main transition mechanisms were observed. High free-stream turbulence intensity instigates pure bypass transition through the amplification of a continuous Orr–Sommerfeld (O–S) mode that breaks down after secondary instability. Instead, at low free-stream turbulence intensity, discrete and continuous O–S modes interact and are both involved in the transition process. Visual inspection of the LES snapshots provides a detailed insight in Tollmien–Schlichting (TS) waves–streaks mutual interaction and clearly identifies two main mechanisms involved in turbulence breakdown. On one hand, TS waves trigger varicose instability of streaky structures. On the other hand, streaks cause secondary instability of TS waves with emerging Λ-structure formation. Then, dynamic mode decomposition (DMD) is applied to extract the main stability properties for both types of transition route and to highlight coherent structure dynamics, which is hardly observable in the literature. Specifically, for low-medium free-stream turbulence levels, DMD extracts unstable modes clearly related to streaks–TS waves interaction and leading to the formation of Λ structures. Therefore, the streaks–TS waves interaction is proved to be destabilizing and to trigger secondary instability leading to turbulence breakdown.
Fluid structure interaction of a subaqueous pendulum: Analyzing the effect of wake correction via large eddy simulations
Authors: Worf Dominik , Khosronejad Ali , Gold Thomas , Reiterer Kevin , Habersack Helmut , Sindelar Christine
Published: May 2022

The dynamic behavior of a subaqueous cylindrical pendulum and corresponding flow dynamics are investigated. The objectives were twofold: (i) to examine whether the two-dimensional model equations sufficiently capture the three-dimensional dynamics and (ii) to investigate the emerging three-dimensional vortical flow structures. Large eddy simulations with two-way coupling fluid structure interaction were carried out using the immersed boundary method to simulate the motion of the pendulum and its interactions with the initially stagnant water. The resulting pendulum motion is compared against measured data obtained in a series of experimental tests to validate the simulation results and the model equations with and without wake corrections. An analysis of the flow vorticity revealed the development of a vortex ring during the first swing and the formation of tip vortices. The evolution of the vortex rings emerging from the motion of the subaqueous cylindrical pendulum was visualized using Q-criteria showing a reasonable agreement with vortical structures observed in the experiment using particle imaging velocimetry. The hydrodynamic moments acting on the simulated pendulum and the moments calculated from the model equations are analyzed. Using the insights from these numerical simulations, a modification of the wake correction is proposed to enhance the accuracy of the rate of decay and period. The transient effect of coherent flow on pendulum dynamics, especially the added mass effect, is discussed.
Multi-fidelity modeling to predict the rheological properties of a suspension of fibers using neural networks and Gaussian processes
Authors: Boodaghidizaji Miad , Khan Monsurul , Ardekani Arezoo M.
Published: May 2022

Unveiling the rheological properties of fiber suspensions is of paramount interest to many industrial applications. There are multiple factors, such as fiber aspect ratio and volume fraction, that play a significant role in altering the rheological behavior of suspensions. Three-dimensional (3D) numerical simulations of coupled differential equations of the suspension of fibers are computationally expensive and time-consuming. Machine learning algorithms can be trained on the available data and make predictions for the cases where no numerical data are available. However, some widely used machine learning surrogates, such as neural networks, require a relatively large training dataset to produce accurate predictions. Multi-fidelity models, which combine high-fidelity data from numerical simulations and less expensive lower fidelity data from resources such as simplified constitutive equations, can pave the way for more accurate predictions. Here, we focus on neural networks and the Gaussian processes with two levels of fidelity, i.e., high and low fidelity networks, to predict the steady-state rheological properties, and compare them to the single-fidelity network. High-fidelity data are obtained from direct numerical simulations based on an immersed boundary method to couple the fluid and solid motion. The low-fidelity data are produced by using constitutive equations. Multiple neural networks and the Gaussian process structures are used for the hyperparameter tuning purpose. Results indicate that with the best choice of hyperparameters, both the multi-fidelity Gaussian processes and neural networks are capable of making predictions with a high level of accuracy with neural networks demonstrating marginally better performance.
Micro-damage evolution under intensive dynamic loading and its influence on constitutive and state equations for nanocrystalline NiTi alloy through molecular dynamics
Authors: Cui Yehui , Zeng Xiangguo , Xiao Junfeng , Wang Fang
Published: May 2022

In this study, to comprehensively reveal the damage mechanisms of NiTi alloys, molecular dynamics (MD) simulations were applied to examine the void evolution process under uniaxial and triaxial intensive dynamic loading. A single-crystal model was first used in the MD simulations. The calculation results revealed that the single-crystal NiTi model exhibited a similar damage response to brittle fracture. The corresponding damage mechanism was the rapid growth and coalescence of voids inside the material. Meanwhile, the defect influence was also examined for the single-crystal model, and the reduction effect of the ultimate stress value due to the stress concentration was analyzed quantitatively by the MD simulations. In addition, a polycrystalline model of NiTi was used in the MD simulations. Compared with the single-crystal model, the polycrystalline model showed an evident plastic stage under uniaxial loading due to dislocation slip. The MD simulation proved that the dislocations accumulated on the grain boundaries, which led to a stress concentration effect on the grain boundaries and sequentially resulted in void generation. However, the propagation and coalescence of voids were hindered by the grain interactions, which resulted in a ductile damage behavior inside the material. Based on this mechanism, the grain size influence was also studied in the MD simulations. It was discovered that the grain size effect in the damage stage resulted in a damage ductility enhancement with the decrease in the average grain size value. Finally, based on the relationships between the stress-strain curve, void fraction, and damage behavior, novel constitutive and state equations were proposed with damage terms to consider the void evolution process during the damage stage. The prediction results showed good agreement with the MD simulation data.
Droplet impact dynamics over a range of capillary numbers and surface wettability: Assessment of moving contact line models and energy budget analysis
Authors: Patil Nagesh D. , Shaikh Javed , Sharma Atul , Bhardwaj Rajneesh
Published: May 2022

Bouncing and non-bouncing impact dynamics of a droplet on a solid surface are studied experimentally and numerically. High-speed visualization and an in-house dual-grid level-set method based solver are employed. Two established contact angle models, namely, Kistler and Fukai models, are implemented in the solver. While the Kistler model employs a time-varying dynamic contact angle, the Fukai model accounts for a quasi-dynamic contact angle based on contact line velocity. Better agreement between the present numerical result and present as well as published experimental results of a dynamic contact angle is found for the Kistler model, specifically for more transient contact angle variations cases that correspond to the less viscous droplets on the hydrophilic surfaces (Ca = 0.005–0.037 and θeq = 22°–90°). This is because the Kistler model can replicate more dynamic variations of the contact angles during spreading and receding as compared to the Fukai model, while both the Fukai and Kistler models numerical results are found in good agreement with the measurements for less transient contact angle variations cases that correspond to the high viscous droplets on the hydrophilic/hydrophobic surfaces (Ca = 7.596 and θeq = 86°–125°). Finally, the coupled effects of liquid surface tension, liquid viscosity, substrate wettability, and impact velocity during droplet bouncing and non-bouncing are presented through an energy budget analysis. At a given impact velocity, for less-viscous and less-surface tension liquids, the viscous dissipation is substantial irrespective of the surface wettability, whereas for less-viscous and high-surface tension liquids, the viscous dissipation is smaller on hydrophobic surfaces as compared to that on hydrophilic surfaces.
Partial cation disorder in Li2MnO3 obtained by high-pressure synthesis
Authors: Abulikemu Aierxiding , Gao Shenghan , Matsunaga Toshiyuki , Takatsu Hiroshi , Tassel Cédric , Kageyama Hiroshi , Saito Takashi , Watanabe Toshiki , Uchiyama Tomoki , Yamamoto Kentaro , Uchimoto Yoshiharu , Takami Tsuyoshi
Published: May 2022

While atomic disorder has provided a paradigm shift in crystalline materials because of unusual atomic arrangements and functional response, “partial” disorder is scarcely reported until now. We discovered partial cation disorder in Li2MnO3 with fewer stacking faults, which was synthesized under high pressure. Mn and Li atoms in a Mn2/3Li1/3O2 layer disorder while Li atoms in a Li layer order. Magnetization and specific heat measurements indicate a long-range antiferromagnetic (AF) order below 35 K. The irreversibility observed in the magnetization data and the hump observed for the specific heat data suggest the coexistence of an AF order and a partial magnetic disorder. Neutron diffraction measurements reveal that the coexisted state is formed instead of the Néel AF state that has previously been reported for conventional Li2MnO3. These results indicate that high pressure makes a breakthrough to introduce partial disorder within crystals and designs not only a unique magnetic structure but also other physical properties.
Structured light illumination for pressure-sensitive paint measurement under ambient light
Authors: Matsuda Yu , Katayama Satoshi , Ikami Tsubasa , Egami Yasuhiro , Nagai Hiroki
Published: May 2022

We propose a pressure-sensitive paint (PSP) method under ambient light based on structured light illumination. In the PSP method, pressure is obtained by measuring the variation of the emission light intensity from a PSP coating when it is illuminated by a light source. Since the extraction of the emission light from ambient light is difficult in the conventional PSP method, the existence of ambient light induces a noticeable measurement error. While spatially uniform light is used as illumination light in the conventional PSP method, structured light, the spatial intensity of which is actively controlled, is used in the proposed method. By measuring the PSP emission by varying the spatial pattern of the structured light illumination, one can eliminate ambient light, which is not synchronized with the structured light and can measure pressure without the effect of ambient light. In this study, we demonstrate the pressure measurement under ambient light using structured light with a sinusoidal wave generated by a digital mirror device. The measured pressure agrees well with the pressure measured by a pressure transducer connected to a pressure tap. The proposed method is promising under ambient light conditions.
Magnetic skyrmion manipulation in CrTe2/WTe2 2D van der Waals heterostructure
Authors: Fragkos Sotirios , Pappas Panagiotis , Symeonidou Evgenia , Panayiotatos Yerassimos , Dimoulas Athanasios
Published: May 2022

Magnetic skyrmions in two-dimensional van der Waals materials provide an ideal platform to push skyrmion technology to the ultimate atomically thin limit. In this work, we theoretically demonstrate the Dzyaloshinskii–Moriya interaction and the formation of a Néel-type skyrmion lattice at the CrTe2/WTe2 bilayer van der Waals heterostructure. Our calculations suggest a field-controlled Néel-type skyrmion lattice—a ferromagnet transition cycle. In addition, a spin-torque induced by spin-polarized current injection was simulated in order to study the motion of a skyrmion on a racetrack, where an increase in the skyrmion Hall angle is observed at high temperatures. Consequently, this study suggests that generation and annihilation of skyrmions can be achieved with temperature or field control and also manipulate the velocity and the direction of the Néel-type skyrmions through ultra-low current densities and temperature, thus shedding light on the general picture of magnetic skyrmion control and design of two-dimensional van der Waals heterostructures.
Improved fifth-order weighted essentially non-oscillatory scheme with low dissipation and high resolution for compressible flows
Authors: Ning Jianguo , Su Xuan , Xu Xiangzhao
Published: May 2022

Compressible flows are numerically simulated using hyperbolic conservation laws. This study proposes a modified fifth-order weighted essentially non-oscillatory (WENO) scheme with a relatively low dissipation and high resolution for hyperbolic conservation laws. This scheme exhibits good performance when solving complex compressible flow fields containing strong discontinuities and smooth microstructures. A simple local smoothness indicator and an eighth-order global smoothness indicator are introduced to improve the accuracy. Furthermore, we construct a new optimal coefficient, which can be adaptively adjusted with different states of the flow field. It no longer depends on the grid spacing. This adaptive coefficient not only reduces dissipation while improving the resolution but also prevents negative dissipation and effectively suppresses spurious numerical oscillations. The proposed scheme attains a higher accuracy at high-order critical points than three classical WENO schemes. Moreover, analysis of the approximate dispersion relation indicates that the proposed scheme provides good dispersion and dissipation properties compared with other WENO schemes. Finally, several standard numerical experiments are performed to demonstrate the enhanced performance of the proposed scheme. The numerical results indicate that the present scheme has a low dissipation, high resolution, and good stability to capture both smooth and discontinuous structures.
Nondestructive inspection of metallic microstructure chips based on photoacoustic remote sensing microscopy
Authors: Chen Jijing , Li Shuai , Long Ying , Chen Xieyu , Liu Bowen , Hu Minglie , Li Jiao , Tian Zhen
Published: May 2022

Nondestructive testing of packaged chips is essential for ensuring product performance, yet existing methods have serious drawbacks. Here, we apply photoacoustic remote sensing microscopy using a high-frequency pulse laser with a pulse width of 1.2 ps and a wavelength of 1030 nm to inspect silicon-based semiconductor chips for internal defects. Joint optical-mechanical scanning allowed high-resolution imaging of a large field of view. The basis for photoacoustic imaging was explained using a solid-state physics model, which was confirmed experimentally by measuring photoacoustic amplitudes at different doping concentrations. Our method appears capable of rapidly imaging chips over a large field of view with depth-to-resolution ratios of around 200 without the need for a couplant, which could support nondestructive inspection in industrial applications.
3D printed ferroelectret with giant piezoelectric coefficient
Authors: Kumar Ajay , Saini Dalip , Mandal Dipankar
Published: May 2022

A ferroelectret cellular structure of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] is fabricated by a 3D printing technique that exhibits a giant piezoelectric coefficient of 1200 pC/N, which is 40 times higher than its commonly known film counterpart. It attributes that the bi-polar charge separation in cellular voids upon the corona discharge behaves as macroscopic dipoles. An increase in the surface potential and dielectric constant (from 10 to 20 at 1 kHz) also attributes to charged voids. Furthermore, the deviation of ferroelectric behavior, for instance, the continuous increasing trend in dielectric constant and remanent polarization as a function of temperature attributes to ferroelectret behavior of a 3D printed P(VDF-TrFE) specimen. The mechanical energy harvester (MEH) made with this ferroelectret structure shows prompt response with ∼4 W/m2 of the power density. Furthermore, the benefit of the giant piezoelectric coefficient of the MEH is used to demonstrate self-powered tactile mapping.
Optical second harmonic generation: role of symmetry and local resonances (review)
Authors: Baranova I.M. , Dolgova T.V. , Kolmychek I.A. , Maydykovskiy A.I. , Mishina E.D. , Murzina T.V. , Fedyanin A.A.
Published: May 2022

We report some results of studying optical second-harmonic generation (SHG) on surfaces and at interfaces of centrosymmetric media, in resonant nano- and microstructures, and in ferroelectric materials. The research was carried out at the Department of Quantum Electronics of the Lomonosov Moscow State University under the supervision of Professor O.A. Aktsipetrov, and subsequently developed by his disciples. As examples that clearly demonstrate the possibilities of the SHG method for examining nonstandard objects of nonlinear optics, we discuss the behaviour of the nonlinear optical response of single-crystal silicon and germanium surfaces and their interfaces with oxides, as well as nonlinear electroreflection. Optical interferometry and its possibilities are briefly described using the example of these systems. Unique sensitivity of SHG to the symmetry and resonance properties of nanostructures, including magnetic ones, is shown, which determines the efficiency of this method for investigating such systems. Finally, we demonstrate that the SHG effect is a unique remote and sensitive method for studying ferroelectric structures.
Amplification of laser radiation at the edge of the KrF (B–X) spectral line
Authors: Yampolskaya S.A. , Yastremskii A.G. , Panchenko Yu.N. , Puchikin A.V.
Published: May 2022

We report the results of experimental and numerical studies of the KrF electric discharge amplifier operating on a mixture of He – Kr – F2 gases. The possibility of expanding the short-wavelength spectral region of the induced radiation tuning at the B – X transition of the KrF molecule by removing the inverse population from the upper vibrational states of the electronic B level is shown. It is demonstrated that at the boundary of the active medium gain contour, the measured gain at a wavelength of 246.8 nm is 0.053 cm−1. Using the developed 1D model of the KrF electric discharge amplifier, it is shown that when the active medium is excited by a pump pulse with a specific peak power of ∼10 MW cm−3, the gain in this spectral region is due to a longer relaxation time of the population of excimer molecules from the upper vibrational levels compared with the characteristic time of their production.
Spectroscopic VUV diagnostics of high-temperature iron plasmas using the comparison method
Authors: Shevelko A.P.
Published: May 2022

We report the development of a new comparison method used to estimate the electron temperatureTeof heavy-element plasmas and high-temperature iron laser-produced plasmas. To this end, two laser-produced plasmas – magnesium plasmas and iron plasmas – were studied at identical laser radiation fluxes on the target. Plasma diagnostics was performed using X-ray spectra of H- and He-like Mg ions. VUV spectra of Fe ions were recorded in the wavelength range 15 – 150 Å As a result, the change in the structure of the VUV spectra of Fe ions as a function ofTein the range of 100 – 400 eV was studied. These data are necessary for diagnosing plasma sources containing the iron element.
Assessment of the thermal effect of femtosecond and millisecond laser pulses in microsurgery of mammalian embryos
Authors: Sitnikov D.S. , Ilina I.V. , Pronkin A.A.
Published: May 2022

We compare the thermal effect exerted by femtosecond and millisecond pulses during microsurgical procedures on embryos. The linear and nonlinear absorption of laser pulses in an aqueous medium, as well as heat transfer from the focusing region of the laser beam to adjacent regions, are considered.
Determining containment policy impacts on public sentiment during the pandemic using social media data
Authors: Sukhwal Prakash Chandra , Kankanhalli Atreyi
Published: May 2022

Significance

For effective pandemic response, policymakers need tools that can assess policy impacts in near real-time. This requires policymakers to monitor changes in public well-being due to policy interventions. Particularly, containment measures affect people’s mental well-being, yet changes in public emotions and sentiments are challenging to assess. Our work provides a solution by using social media posts to compute salient concerns and daily public sentiment values as a proxy of mental well-being. We demonstrate how public sentiment and concerns are impacted by various containment policy sub-types. This approach provides key benefits of using a data-driven approach to identify public concerns and provides near real-time assessment of policy impacts by computing daily public sentiment based on postings on social media.
Bringing and taking
Authors: Hellwig Birgit , Margetts Anna , Riesberg Sonja , Schippling Melanie
Published: May 2022

This chapter proposes a typology of expressions of directed caused accompanied motion (directed CAM): it introduces and defines this semantic domain, presents the corpus-based methodology used by the authors of this volume, and gives an overview of the results. It shows that directed CAM expressions tend to be morphosyntactically complex and it identifies four distinct patterns based on the lexical core of the expression: first, with a directed CAM verb; second, with an intransitive motion verb; third, with a transitive verb of accompaniment or of caused (accompanied) motion; or fourth, with a combination of the second and the third options. The chapter discusses each pattern and addresses issues of universality and variability in the domain of directed CAM.
The expression of directed caused accompanied motion events in Yurakaré
Authors: Gipper Sonja
Published: May 2022

This chapter gives an overview of the expression of directed caused accompanied motion events in Yurakaré (isolate, Bolivia) spoken discourse. Building on previous descriptive work by van Gijn (2005, 2006, 2011b), the chapter sets a focus on discourse frequencies of the relevant constructions, including a detailed analysis of the contributions of semantics and pragmatics to the expression of the four defining meaning components (directedness, causation, accompaniment, motion). In addition, I examine the variability in interactants’ choice of expression when describing the same event, emphasizing different aspects of the event with their choice. I argue that interactional strategies such as self‑ and cross-speaker repetition can explain part of the variability by influencing discourse frequencies.
Directed caused accompanied motion events in Saliba-Logea
Authors: Margetts Anna
Published: May 2022

This chapter describes the encoding of directed caused accompanied motion events (‘directed CAM’) in Saliba-Logea, an Oceanic language of Papua New Guinea. The description is based on analysing patterns in spoken language data. Saliba-Logea expressions of directed CAM are generally morphosyntactically complex and meaning components are frequently distributed across more than one verb. In such multi-verb constructions, one verb expresses caused motion, the other directionality. In Saliba-Logea the most common expressions of directed CAM events include information about the manner of caused motion in constructions with verbs like ‘carry’, ‘drag’ or ‘guide’.