bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolonged Second Stage of Labor and Anal Sphincter Injury in a Contemporary Cohort of Term Nulliparas
Authors: Naqvi Mariam , Jaffe Elana F. , Goldfarb Ilona T. , Bryant Allison S. , Wylie Blair J. , Kaimal Anjali J.
Published: October 2020

Objective This study aimed to assess whether a prolonged second stage of labor is an independent predictor of obstetric anal sphincter injury (OASI) in a contemporary cohort of nulliparous and term parturients, and to evaluate whether predelivery factors can accurately predict OASI.

Study Design This was a nested case-control study within a cohort of consecutive nulliparous term parturients with a singleton gestation who underwent a vaginal delivery at a single institution between January 2014 and January 2015. Cases were defined as women with a third- or fourth-degree laceration at the time of delivery, and controls were women without a third- or fourth-degree laceration. A prolonged second stage was defined as a second stage of ≥3 hours. Univariable and multivariable regression analyses were performed to examine the relationship between prolonged second stage of labor and third- or fourth-degree lacerations. Receiver operator curves were developed to assess the predictive capacity of predelivery information for third- and fourth-degree lacerations.

Results Of 1,197 births, 63 women had third- or fourth-degree lacerations (5.3%). With each additional hour of the second stage, the rate of OASI increased, with 2.9% of women with a second stage of <1 hour with OASI, 3.5% between 1 and 2 hours, 5.7% between 2 and 3 hours, 7.8% between 3 and 4 hours, 16.1% between 4 and 5 hours, and 28.6% among women with a second stage length >5 hours (p < 0.001). In multivariable regression analysis, operative vaginal delivery (adjusted odds ratio [aOR] = 5.92, 95% confidence interval [CI]: 3.17–11.07) and a prolonged second stage (aOR = 1.92, 95% CI: 1.06–3.51) were independent predictors of third- and fourth-degree lacerations. A predictive model was developed from these results (area under the curve [AUC] = 0.75, 95% CI: 0.68–0.81).

Conclusion Prolonged second stage of labor is a predictor of OASI, after adjustment for operative vaginal delivery. A model using predelivery risk factors has a reasonable prediction of OASI.

Key Points
Does Laparoscopy and Hysteroscopy Have a Place in the Diagnosis of Unexplained Infertility?
Authors: Kamath Mohan S. , Rikken Judith F.W. , Bosteels Jan
Published: October 2020

The standard fertility workup includes assessment of ovulation, semen analysis, and evaluation of tubal patency. If the fertility workup is found to be normal, a diagnosis of unexplained infertility is made. The role of laparoscopy in fertility workup has been a matter of debate. The current review presents the evidence for and against laparoscopy and hysteroscopy during fertility workup and subsequently prior to fertility treatment. After appraising the literature, we found the role of diagnostic laparoscopy in fertility workup is limited and is dependent on factors like prevalence of pelvic infection, setting, and availability of expertise. Moreover, whenever a laparoscopy is planned as a part of the fertility workup, the preparation should include ability to carry out simultaneous therapeutic intervention to maximize the benefit. Similarly, the routine use of hysteroscopy in women with unexplained infertility cannot be recommended. There is a need to investigate the impact of choice of tubal test on chances of spontaneous conception and treatment outcomes in women with unexplained infertility. Our future research agenda should also include high-quality multicenter randomized trials assessing the cost-effectiveness of screening and operative hysteroscopy prior to intrauterine insemination or in vitro fertilization.
Filtering noise in time and frequency domain for ultrafast pump–probe performed using low repetition rate lasers
Authors: Khatua Durga Prasad , Gurung Sabina , Singh Asha , Khan Salahuddin , Sharma Tarun Kumar , Jayabalan J.
Published: October 2020

Optical pump–probe spectroscopy is a powerful tool to directly probe the carrier dynamics in materials down to sub-femtosecond resolution. To perform such measurements, while keeping the pump induced perturbation to the sample as small as possible, it is essential to have a detection scheme with a high signal to noise ratio. Achieving such a high signal to noise ratio is easy with phase sensitive detection based on a lock-in-amplifier when a high repetition rate laser is used as the optical pulse source. However, such a lock-in-amplifier based method does not work well when a low repetition rate laser is used for the measurement. In this article, a sensitive detection scheme, which combines the advantages of a boxcar that rejects noise in time domain and a lock-in-amplifier that isolates the signal in the frequency domain for performing pump–probe measurements using a low-repetition rate laser system, is proposed and experimentally demonstrated. A theoretical model to explain the process of signal detection and a method to reduce the pulse to pulse energy fluctuation in probe pulses is presented. By performing pump–probe measurements at various detection conditions, the optimum condition required for obtaining the transient absorption signal with low noise is presented. The reported technique is not limited to pump–probe measurements and can be easily modified to suit for other sensitive measurements at low repetition rates.
Enabling Ga2O3’s neutron detection capability with boron doping and conversion layer
Authors: Blevins Jacob , Yang Ge
Published: October 2020

There is a growing necessity to develop revolutionary neutron detectors for nuclear energy, nuclear physics, medical physics, astrophysics, biological imaging, nonproliferation, and national security. The often-used Helium-3 (He-3) neutron detector is becoming increasingly difficult to obtain due to He-3 shortages. As an emerging oxide semiconductor material, Ga2O3 exhibits excellent physical properties. These physical merits enable Ga2O3’s potential as a high-performance semiconductor neutron detector for extreme condition applications. Here, two approaches are explored, i.e., applying an exterior conversion layer of boron-10 (B-10) on Ga2O3 and directly doping B-10 into Ga2O3 to demonstrate Ga2O3’s capability for neutron detection. Using Monte Carlo simulation, we show the distinct difference in neutron detection efficiency of Ga2O3 when applying direct doping of B-10 into Ga2O3 vs applying a uniform B-10 conversion layer on top of Ga2O3. Our results exhibit that the theoretically predicted maximum doping level of B-10 in Ga2O3 does not lead to the same detection efficiency as that of a simple B-10 conversion layer when detecting 480 keV gammas. Except for the most thermalized neutrons at 0.01 eV, direct doping simulations are not able to achieve comparable results to that of the conversion layer method.
Thermo-elastic properties of bcc Mn-rich high-entropy alloy
Authors: Huang Shuo , Dong Zhihua , Mu Wangzhong , Ström Valter , Chai Guocai , Vitos Levente
Published: October 2020

We report a chemically disordered solid solution, Al0.6Cr0.2MnFe0.5Co0.3Ni0.5, based on a body-centered cubic underlying lattice with the measured Curie temperature of ∼380 K. First-principles alloy theory is employed to investigate the temperature-dependent free energy, elastic constants, and coefficient of thermal expansion at the ferromagnetic and paramagnetic states. Theory and experiment are found to strengthen each other, and the results indicate that the magnetic state has a strong impact on the thermo-elastic properties of the considered alloy. The present advance in the thermo-magneto-elasticity enhances the understanding required for controlling the magnetic and mechanical response of multi-component systems.
Phenomenological dynamics of COVID-19 pandemic: Meta-analysis for adjustment parameters
Authors: Hojman Sergio A. , Asenjo Felipe A.
Published: October 2020

We present a phenomenological procedure of dealing with the COVID-19 (coronavirus disease 2019) data provided by government health agencies of 11 different countries. Usually, the exact or approximate solutions of susceptible–infected–recovered (or other) model(s) are obtained fitting the data by adjusting the time-independent parameters that are included in those models. Instead of that, in this work, we introduce dynamical parameters whose time-dependence may be phenomenologically obtained by adequately extrapolating a chosen subset of the daily provided data. This phenomenological approach works extremely well to properly adjust the number of infected (and removed) individuals in time for the countries we consider. Besides, it can handle the sub-epidemic events that some countries may experience. In this way, we obtain the evolution of the pandemic without using any a priori model based on differential equations.
Joint optimization of the number, type and layout of wind turbines for a new offshore wind farm
Authors: Zhang Jinhui , Jiang Yuewen
Published: October 2020

Prominent problems, including the high investment cost and limited generation revenue of offshore wind farms, are of concern. To tackle these problems, a bi-level model is proposed, whose upper level represents the offshore wind farm optimization for the target of maximizing the profit, and the lower level represents the day-ahead market clearing with the participation of an offshore wind farm. In the upper level, the number, type, and coordinates of wind turbines are simultaneously optimized on the premise of the determined sea area. The layout of an offshore wind farm in irregular sea areas can be obtained by constructing specific penalty functions. In the lower level, under different wind conditions and load, the day-ahead market with the goal of maximizing social welfare is cleared, and the cleared wind power and local marginal prices of an offshore wind farm are provided for the upper level model. Finally, the optimal number, type, and coordinates of wind turbines are obtained by solving the two-layer model. In a rectangular planned sea area, the bi-level optimization model is successfully applied. The test results show that when 27 wind turbines with a rated capacity of 6.45 MW are placed in the planned sea area, the annual investment profit reaches the maximum value of 22.6 × 106 euros. When the optimized layout of an offshore wind farm is used, the power deviation of 67% wind turbines caused by the wake effect can be controlled within 7%, which verifies that the optimized layout plays a role in reducing the wake effect.
Pair plasma instability in homogeneous magnetic guide fields
Authors: Pueschel M. J. , Sydora R. D. , Terry P. W. , Tyburska-Pueschel B. , Francisquez M. , Jenko F. , Zhu B.
Published: October 2020

Pair plasmas, collections of both matter and antimatter particles of equal mass, represent a paradigm for the study of basic plasma science, and many open questions exist regarding these unique systems. They are found in many astrophysical settings, such as gamma-ray bursts, and have recently also been produced in carefully designed laboratory experiments. A central research topic in plasma physics is instability; however, unlike their more common ion–electron siblings, pair plasmas are generally thought to be stable to cross field pressure gradients in homogeneous magnetic fields. It is shown here by means of kinetic full-f simulations that, when a pressure gradient is first established, the Gradient-driven Drift Coupling mode is destabilized and becomes turbulent. Force balance is eventually achieved by a combination of flattened pressure profiles due to turbulent transport and establishment of a magnetic field gradient, saturating the growth. During the unstable phase, key physics can be captured by a δf gyrokinetic description, where it is shown analytically and numerically that parallel particle motion results in a coupling of all electromagnetic field components. A fluid model derived therefrom accurately predicts linear eigenmodes and is used to resolve global profile effects. For laser-based electron–positron plasma experiments, prompt instability is predicted with growth times much shorter than plasma lifetimes. Similarly, growth rates are calculated for the planned APEX experiment as well as gamma-ray burst scenarios, suggesting that the instability may contribute to the early evolution of these systems.
Tailoring magnetic vortices of dipolar coupled nanoelements
Authors: Dantas J. T. S. , Silva Maria G. D. , Oliveira L. L. , Pedrosa S. S. , Rebouças G. O. G. , Dantas Ana L. , Carriço A. S.
Published: October 2020

We report a theoretical study of the magnetic profiles of vortex pairs of dipolar coupled Fe nanocylinders. We consider pairs of identical and coaxial 21 nm height Fe circular nanocylinders with the diameter values ranging from 81 nm to 129 nm. We show that, even though each isolated nanocylinder holds a vortex at remanence, the dipolar interaction may inhibit the formation of vortices for small values of the nanocylinders’ distance. For moderate values of the nanocylinders’ distance, the formation of opposite chirality vortex pairs is favored. We show that the vortex locations, the vortex pair magnetic pattern, and the dipolar field and local field profiles may be tailored using moderate external field values along preparation routes parallel and perpendicular to the Fe uniaxial anisotropy easy axis.
Molecular beam epitaxy growth and strain-induced bandgap of monolayer 1T′-WTe2 on SrTiO3(001)
Authors: Li Huifang , Chen Aixi , Wang Li , Ren Wei , Lu Shuai , Yang Bingjie , Jiang Ye-Ping , Li Fang-Sen
Published: October 2020

A monolayer 1T′-WTe2 film is grown on SrTiO3(001) with in-plane tensile strain. A height of ∼0.7 nm, obvious charge transfer, and incommensurate charge fluctuations in 1T′-WTe2 suggest strong coupling to the STO substrate. Scanning tunneling spectroscopy on the surface reveals that a large energy gap opens at the Fermi level with nearly zero conductance. The opened energy gap decreases with the increase in the WTe2 island size. The lack of the metallic edge state on monolayer 1T′-WTe2/SrTiO3(001) indicates the absence of the quantum spin Hall (QSH) state. Our study here demonstrates that the energy gap of monolayer 1T′-WTe2 can be tuned by lattice strain and illustrates the importance of interface coupling to realize the metallic edge state and QSH in monolayer 1T′-WTe2.
Epitaxial strain dependent electrocatalytic activity in CaRuO3 thin films
Authors: Lee Jegon , Jun So-Yeon , Choi Taekjib , Jung Donggeun , Bae Jong-Seong , Lee Sang A , Choi Woo Seok
Published: October 2020

The systematic tunability of electrocatalytic activity is indispensable not only for realizing highly efficient catalysts but also for understanding the underlying mechanism of chemical reactions at the surface. Epitaxial strain is a powerful tool for tailoring various physical and chemical properties of perovskite transition metal oxides, including electrocatalytic activity. We present single-crystalline CaRuO3 epitaxial thin films as a model system, in which the oxygen evolution reaction was systematically controlled by the epitaxial strain. With an increase in the degree of tensile strain, the interband transition energy and hybridization strength within the Ru–O bond decreased, which enhanced the oxygen evolution reaction. Our study facilitates the understanding of the correlation between the lattice/electronic structure and the electrocatalytic activity, which might be applied to other transition metal oxide catalysts.
Cubic silicon carbide/zinc oxide heterostructure fuel cells
Authors: Xing Yueming , Hu Enyi , Wang Faze , Muhammad Naveed , Wang Baoyuan , Wang Jun , Maryam Ammara , Rasheed Muhammad Naveed , Asghar Muhammad , Xia Chen , Yun Sining , Zhu Bin
Published: October 2020

Multifunctional semiconductor cubic silicon carbide (3C-SiC) is employed for fuel cell electrolyte, which has never been used before. n-type 3C-SiC can be individually employed as the electrolyte in fuel cells, but delivers insufficient open circuit voltage and minuscule current density due to its electronic dominant property. By introducing n-type ZnO to form an n–n 3C-SiC/ZnO heterostructure, significant enhancements in the ionic conductivity of 0.12 S/cm and fuel cell performance of 270 mW cm−2 are achieved at 550 °C. It is found that the energy band bending and build-in electric field of the heterostructure play the pivotal role in the ionic transport and suppressing the electronic conduction of 3C-SiC, leading to a markable material ionic property and fuel cell performance. These findings suggest that 3C-SiC can be tuned to ionic conducting electrolyte for fuel cell applications through the heterostructure approach and energy band alignment methodology.
A setup to measure the Seebeck coefficient and electrical conductivity of anisotropic thin-films on a single sample
Authors: Dörling Bernhard , Zapata-Arteaga Osnat , Campoy-Quiles Mariano
Published: October 2020

This work documents an all-in-one custom setup that allows us to measure the in-plane Seebeck coefficients and electrical conductivities of anisotropic thin film samples close to room temperature. Both pairs, S∥ and σ∥ and S⊥ and σ⊥, can be measured using four contacts on the same sample, reducing measurement time and minimizing potential sources of error due to aggregating data from several distinct samples. The setup allows us to measure the electrical conductivity of isotropic samples using the well-known van der Pauw method. For samples with in-plane anisotropy, the two components σ∥ and σ⊥ can be extracted from the same type of measurements by performing additional calculations. Using the same contacts, the Seebeck coefficient along one direction is measured using a differential steady-state method. After rotating the sample by 90°, the orthogonal Seebeck component can be measured. In order to show the generality of the method, we measure different types of samples, from metal references to oriented doped conjugated polymers.
Stopbands in fast ion-acoustic soliton propagation revisited
Authors: Verheest Frank , Hellberg Manfred A.
Published: October 2020

It was recently discovered that, in a multispecies plasma with two positive ion species (one cold and one warm adiabatic) and Boltzmann-distributed electrons, a “stopband” could occur, i.e., there was a range of velocities where no fast ion-acoustic solitons could propagate between two ranges where propagation was possible. Several extensions were subsequently investigated, including the effects of the cool ions having finite temperature and of nonthermal electron distributions. Efforts were made to estimate existence domains in plasma parameter space, often by ad hoc arguments, but the illustrations were invariably restricted to the same specific set of parameter values or their neighborhoods. In contrast, here, a systematic and structured study is given: physical arguments determine a range of compositional parameters so that a Sagdeev pseudopotential analysis establishes in a consistent way the various curves limiting the existence domains in parameter space. This is done for four models, namely, Boltzmann, nonthermal Cairns, superthermal kappa, and nonextensive Tsallis electron distributions, and for each, existence domains are plotted in the space of ion charge-to-mass ratio and inverse electron temperature, and detailed examples are presented. Contrary to reports in the literature, stopbands are shown to exist for large deviations from isothermality. However, their range in parameter space is shifted from that obtained for Boltzmann electrons. This establishes that the stopband phenomenon is robust and governed primarily by the cold and warm ion properties and the electron temperature, the form of the electron distribution having only a quantitative effect.
Electronic structure spectroscopy of organic semiconductors by energy resolved-electrochemical impedance spectroscopy (ER-EIS)
Authors: Schauer Franz
Published: October 2020

Organic electronic applications are envisioned to address broad markets, which includes flexible displays, electronic papers, sensors, disposable and wearable electronics, and medical and biophysical applications, leading to a tremendous amount of interest from both academia and industry in the study of devices. These fields of science and technology constitute interdisciplinary fields that cover physics, chemistry, biology, and materials science, leading, as a wanted output, to the elucidation of physical and chemical properties, as well as structures, fabrication, and performance evaluation of devices and the creation of new knowledge underlying the operation of organic devices using new synthesized organic materials—organic semiconductors. We testify the situation when the available organic electronic applications sometimes lack a theoretical background. The cause may be the complicated properties of disordered, weak bounded, molecular materials with properties different from their inorganic counterparts. One of the basic information-rich resources is the electronic structure of organic semiconductors, elucidated by the methods, hardly possible to be transferred from the branch of inorganic semiconductors. Electrochemical spectroscopic methods, in general, and electrochemical impedance spectroscopy, in particular, tend and seem to fill this gap. In this Perspective article, the energy resolved-electrochemical impedance spectroscopic method for electronic structure studies of surface and bulk of organic semiconductors is presented, and its theoretical and implementation background is highlighted. To show the method’s properties and strength, both as to the wide energy and excessive dynamic range, the basic measurements on polymeric materials and D–A blends are introduced, and to highlight its broad applicability, the results on polysilanes degradability, gap engineering of non-fullerene D–A blends, and electron structure spectroscopy of an inorganic nanocrystalline film are highlighted. In the outlook and perspective, the electrolyte/polymer interface will be studied in general and specifically devoted to the morphological, transport, and recombination properties of organic semiconductors and biophysical materials.
Effects of post-laser irradiation on the optical and structure properties of Al2O3 nanoparticles produced by laser ablation
Authors: ElFaham Mohamed M. , Okil M. , Mostafa Ayman M.
Published: October 2020

Alumina nanoparticles with different average particle sizes were synthesized by pulsed laser ablation of Al plates in ethanol, followed by laser irradiation at different times. Their optical and structural properties were investigated by different techniques. The experimental work showed that as the time of post-laser irradiation increased, the average particles’ size of alumina decreased. The decrease in the particle size is detected by using x-ray diffraction (XRD) technique and UV-visible absorption spectroscopy technique (UV–VIS) and characterized by laser-induced breakdown spectroscopy (LIBS). The LIBS technique was utilized as a diagnostic tool with XRD and UV–VIS for determining the nanoparticles’ size. Laser-induced plasma parameters such as electron density and electron temperature were determined. A relationship has been established between the electron temperature and the nanoparticles’ size. The results reflect the significance of correcting the spectral intensity of the emitted line for the effect of self-absorption in the LIBS experiment.
Control of relative electron densities and spacing of two laser induced plasmas by spatial light modulation of femtosecond laser
Authors: Ross M. P. , Pascoguin B. M. L. , Hening A. , Lynn B.
Published: October 2020

This study demonstrates a novel technique for independently controlling the relative electron densities and axial separation of two laser induced plasmas (LIPs) formed in air by an ultrashort pulse laser (USPL). A spatial light modulator (SLM) provides the means of control by altering the wavefront of a 35 fs, 1.6–2.5 mJ pulse from a Ti:Sapphire USPL with a 790 nm center wavelength. After modification by the SLM, a lens focuses the pulse, which increases its intensity and generates plasma by ionizing air. Holograms displayed on the SLM diffract a controlled amount of laser energy to a first-order focal spot some distance from the lens focus, and sufficient laser power generates two LIPs spaced from one another along the laser propagation direction. The hologram contrast dictates the relative intensity of the light arriving at each focus, and the spatial gradient of the phase shift applied by the hologram determines the distance between the two foci. Analytic solutions of linear light propagation and scalar diffraction theory computed with the convolution method are used to determine initial hologram designs meant to deliver various foci spacings and relative intensities. Ultrashort pulse lasers (USPLs) supply pulse powers sufficient to induce filamentation in air, a result of non-linear optical phenomena that extends the range of intense laser propagation and generates plasma. Comparing images of linear propagation at low laser powers with relative line-integrated electron density measurements taken during plasma formation indicate any extant non-linear processes do not prevent predictable control of plasma geometry for 0.3 m and 0.5 m focal lengths.
Stacking-configuration-enriched essential properties of bilayer graphenes and silicenes
Authors: Liu Hsin-yi , Lin Shih-Yang , Wu Jhao-ying
Published: October 2020

First-principles calculations show that the geometric and electronic properties of silicene-related systems have diversified phenomena. Critical factors of group-IV monoelements, like buckled/planar structures, stacking configurations, layer numbers, and van der Waals interactions of bilayer composites, are considered simultaneously. The theoretical framework developed provides a concise physical and chemical picture. Delicate evaluations and analyses have been made on the optimal lattices, energy bands, and orbital-projected van Hove singularities. They provide decisive mechanisms, such as buckled/planar honeycomb lattices, multi-/single-orbital hybridizations, and significant/negligible spin–orbital couplings. We investigate the stacking-configuration-induced dramatic transformations of essential properties by relative shift in bilayer graphenes and silicenes. The lattice constant, interlayer distance, buckling height, and total energy essentially depend on the magnitude and direction of the relative shift: AA → AB → AA′ → AA. Apparently, sliding bilayer systems are quite different between silicene and graphene in terms of geometric structures, electronic properties, orbital hybridizations, interlayer hopping integrals, and spin interactions.
Interaction of two cylindrical bubbles embedded in a corotating vortex pair
Authors: Liu Yunqiao , Wang Benlong , Sugiyama Kazuyasu
Published: October 2020

Cylindrical bubbles are frequently accompanied by vortical flows. However, there is a lack of knowledge concerning cylindrical bubble pairs, the simplest interaction unit, compared to the understanding of the interactions between two spherical bubbles or two single-phase vortices. Here, we propose a theoretical model to describe the interaction process of two cylindrical bubbles embedded in two corotating vortices. The dynamic equations of surface modes for two cylindrical bubbles are formulated based on a rotating frame of reference whose angular velocity is determined by the distributions of circulations. The Coriolis force is thereby added to the momentum equation and contributes to the displacements and deformations of the bubbles. Our model recovers the universally accepted unitary criterion for two single-phase vortices. A striking finding is that the merging of two cylindrical bubbles in vortical flows can display two kinds of criteria depending on the relative weights of the surface tension and vortex force.
Frontiers in atomistic simulations of high entropy alloys
Authors: Ferrari Alberto , Dutta Biswanath , Gubaev Konstantin , Ikeda Yuji , Srinivasan Prashanth , Grabowski Blazej , Körmann Fritz
Published: October 2020

The field of atomistic simulations of multicomponent materials and high entropy alloys is progressing rapidly, with challenging problems stimulating new creative solutions. In this Perspective, we present three topics that emerged very recently and that we anticipate will determine the future direction of research of high entropy alloys: the usage of machine-learning potentials for very accurate thermodynamics, the exploration of short-range order and its impact on macroscopic properties, and the more extensive exploitation of interstitial alloying and high entropy alloy surfaces for new technological applications. For each of these topics, we briefly summarize the key achievements, point out the aspects that still need to be addressed, and discuss possible future improvements and promising directions.
Multi-scale nonlinear singular limit for thermal non-equilibrium gas flow with multiple non-equilibrium modes for analytic data in multi-dimensions with physical boundaries
Authors: Luo Tao , Wang Yan-Lin
Published: October 2020

The multi-scale zero relaxation singular limit for gas dynamics in thermal non-equilibrium with multiple non-equilibrium modes in multi-dimensions with physical boundaries from non-equilibrium to thermal equilibrium of compressible Euler flow is proved in this paper for analytical data by establishing the uniform local-in-time estimates. A cancellation mechanism is utilized to deal with the nonlinear singular terms that cause the increase in both time and space derivatives in energy estimates. The rates of the relaxations corresponding to different non-equilibrium modes tending to zero discussed in this paper can be arbitrarily different.
A closer look into the distance dependence of vibrational energy transfer on surfaces using 2D IR spectroscopy
Authors: Fernández-Terán Ricardo , Hamm Peter
Published: October 2020

Vibrational energy transfer (VET) between two isotopologues of [Re(dcb)(CO)3Br] immobilized on a TiO2 surface is studied with the help of 2D IR spectroscopy in dependence of surface coverage. To dilute the molecules on the surface, and thereby control the intermolecular distances, two different diluents have been used: a third isotopologue of the same molecule and 4-cyanobenzoic acid. As expected, the VET rate decreases with dilution. For a quantitative investigation of the distance dependence of the VET rate, we analyze the data based on an excitonic model. This model reveals the typical 1/r6-distance dependence for a dimer of a donor and acceptor, similar to the nuclear Overhauser effect in NMR spectroscopy or Förster resonant energy transfer in electronic spectroscopy. However, VET becomes a collective phenomenon on the surface, with the existence of a network of coupled molecules and its disappearance below a percolation threshold, dominating the concentration dependence of the VET rate.
Enhanced intersystem crossing of boron dipyrromethene by TEMPO radical
Authors: Xu Zihao , Huang Yiming , Cao Yulei , Jin Tao , Miller Kristen A. , Kaledin Alexey L. , Musaev Djamaladdin G. , Lian Tianquan , Egap Eilaf
Published: October 2020

Radical enhanced intersystem crossing (EISC) of organic chromophores is an important approach to generate a long-lived triplet state for various electronic and optoelectronic applications. However, structural factors and design rules to promote EISC are not entirely clear. In this work, we report a series of boron dipyrromethene (BODIPY) derivatives covalently linked with a 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) radical with varying distances and topologies. We show that the incorporation of the TEMPO radical to BODIPY results in strong fluorescence quenching by up to 85% as a result of EISC and enhanced internal conversion. In BDP-2AR [2-(4-methyleneamino-TEMPO) BODIPY], a dyad with the shortest BODIPY–TEMPO through-bond distance, we observe the fastest EISC rate (τisc = 1.4 ns) and the longest triplet excited state lifetime (τT = 32 µs) compared to other distance and geometry variations. Contrary to previous reports and a general presumption, the BODIPY–TEMPO through-bond distance in this system does not play a significant role on the triplet formation rate and yield. Density functional theory suggests a folding of the TEMPO radical to form a sandwich-like structure with a BODIPY ring that leads to a decrease in the through-space distance, providing a new and an interesting insight for the radical enhanced intersystem.
Electronic structure basis of strength and toughness in fluoropolymers
Authors: Xu Justin , Hao Tengyuan , Hossain Zubaer M.
Published: October 2020

Using density functional theory calculations, we investigate and report the electronic structure basis of symmetry-breaking in atomic structures and variations in extreme mechanical properties of a number of widely used polymers, namely, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyethylene, and three structural variants of PVDF. All of these polymers consist of C–C bonds in the backbone and a combination of C–H and C–F bonds attached to the backbone. Our results show that the relative proportion and arrangement of the C–H and C–F bonds, hereafter called the chemical heterogeneity, lead to two distinct sets of structural symmetries and mechanical properties. The set with the lower chemical heterogeneity possesses higher structural symmetry and exhibits higher strength and toughness. Electronic population analysis shows that chemical heterogeneity breaks the structural symmetry and alters deformation induced “electron redistribution patterns” in the C–C backbone. Strong variations in electron redistribution serve as the basis for distinctive mechanical behavior among the polymers: the higher the structural variation and electron redistribution, the lower the bond rupture force and toughness of the polymer. The bond rupture process is initiated by a decrease in the electronic population in the backbone, while the electronic interactions at the C–H and C–F bonds dictate where, how, and which bonds rupture. Furthermore, in the linear regime of mechanical deformation, the force–strain behavior is insensitive to the chemical heterogeneity and controlled by the strong covalent interactions of the C–C bonds. In the nonlinear regime, the chemical heterogeneity dramatically reduces the strength and toughness of the polymer chain.
Nonlinear interactions in the hypersonic boundary layer on the permeable wall
Authors: Zhu Wenkai , Chen Xi , Zhu Yiding , Lee Cunbiao
Published: October 2020

Instability evolution and nonlinear interactions in a hypersonic boundary layer on the permeable wall are investigated over a flared cone. Permeable material is used here as an ultrasonically absorptive coating. Calculations are performed based on both Floquet theory and parabolized stability equations. Relative to the case of the smooth wall, the second mode grows faster in the linear stage and lasts over a longer distance along the flow direction on the permeable wall. Stability calculations based on the acoustic model show that the permeable wall partially promotes the second mode, which is in good agreement with the experimental measurements. For the smooth wall, the fundamental resonance is much stronger than the subharmonic and detuned resonance. The main part of the energy transfers is below the sonic line. However, the suppression of the near-wall disturbances by the permeable wall changes the spatial distribution of perturbations in the fundamental resonance, which disrupts the phase-locked relationship and prevents the growth of fundamental oblique waves.
Numerical investigation of aerosol transport in a classroom with relevance to COVID-19
Authors: Abuhegazy Mohamed , Talaat Khaled , Anderoglu Osman , Poroseva Svetlana V.
Published: October 2020

The present study investigates aerosol transport and surface deposition in a realistic classroom environment using computational fluid-particle dynamics simulations. Effects of particle size, aerosol source location, glass barriers, and windows are explored. While aerosol transport in air exhibits some stochasticity, it is found that a significant fraction (24%–50%) of particles smaller than 15 µm exit the system within 15 min through the air conditioning system. Particles larger than 20 µm almost entirely deposit on the ground, desks, and nearby surfaces in the room. Source location strongly influences the trajectory and deposition distribution of the exhaled aerosol particles and affects the effectiveness of mitigation measures such as glass barriers. Glass barriers are found to reduce the aerosol transmission of 1 µm particles from the source individual to others separated by at least 2.4 m by ∼92%. By opening windows, the particle exit fraction can be increased by ∼38% compared to the case with closed windows and reduces aerosol deposition on people in the room. On average, ∼69% of 1 µm particles exit the system when the windows are open.
Life cycle patterns of cognitive performance over the long run
Authors: Strittmatter Anthony , Sunde Uwe , Zegners Dainis
Published: October 2020

Significance

Despite evidence for an increasing importance of cognitively demanding tasks in the workplace, little is known about the life cycle performance in such tasks, particularly over the long run. We estimate the life cycle patterns of cognitive performance over the past 125 y using a methodology that is based on the comparison of individual move-by-move performance of professional chess players relative to the best move suggested by a chess engine in a given configuration. The findings document a hump-shaped profile of performance over the life cycle and an increase in individual performance, particularly at younger ages, that is associated with dynamics across birth cohorts rather than over time.
Conservative and liberal attitudes drive polarized neural responses to political content
Authors: Leong Yuan Chang , Chen Janice , Willer Robb , Zaki Jamil
Published: October 2020

Significance

Partisan biases in processing political information contribute to rising divisions in society. How do such biases arise in the brain? We measured the neural activity of participants watching videos related to immigration policy. Despite watching the same videos, conservative and liberal participants exhibited divergent neural responses. This “neural polarization” between groups occurred in a brain area associated with the interpretation of narrative content and intensified in response to language associated with risk, emotion, and morality. Furthermore, polarized neural responses predicted attitude change in response to the videos. These findings suggest that biased processing in the brain drives divergent interpretations of political information and subsequent attitude polarization.
Optical signatures of multifold fermions in the chiral topological semimetal CoSi
Authors: Xu Bing , Fang Zhenyao , Sánchez-Martínez Miguel-Ángel , Venderbos Jorn W. F. , Ni Zhuoliang , Qiu Tian , Manna Kaustuv , Wang Kefeng , Paglione Johnpierre , Bernhard Christian , Felser Claudia , Mele Eugene J. , Grushin Adolfo G. , Rappe Andrew M. , Wu Liang
Published: October 2020

Significance

We present a comprehensive combined experimental and theoretical study of optical conductivity in the chiral topological semimetal CoSi based on the development of high-quality crystals. We reveal the presence and the energy range of various exotic multifold quasiparticles in the optical responses and provide experimental evidence for the realization of fourfold spin-3/2 fermions, which were not directly observed previously. Our work is critical to interpreting future optical and transport responses of multifold fermion materials. We believe the methods used in this work will not only stimulate future research in this class of materials but will also provide a strategy for addressing optical signatures of chiral topological fermions in solids.
A 3D-printed molecular ferroelectric metamaterial
Authors: Hu Yong , Guo Zipeng , Ragonese Andrew , Zhu Taishan , Khuje Saurabh , Li Changning , Grossman Jeffrey C. , Zhou Chi , Nouh Mostafa , Ren Shenqiang
Published: October 2020

Significance

Molecular ferroelectrics, which show the ability to switch the electromechanical activity by an external electric field, establish the basis for mechanical metamaterial technologies. Despite their theoretical promise, such mechanical metamaterials remain hindered by the lack of adaptive stimuli-responsive materials which can be effectively tuned “on demand” across time and length scales. Here, we unravel a printable mechanical metamaterial of imidazolium perchlorate with superior electromechanical coupling and reprogrammable stiffness. We propose a continuous rapid three-dimensional (3D) printing technique which can reduce the manufacturing time of ferroelectrics from hours down to minutes. The printed molecular ferroelectric metamaterial structure is then shown to enable a tunable-frequency vibration-isolating architecture. This study paves the way for rationally designed 3D-printable molecular ferroelectric metamaterials.
Magnetized topological insulator multilayers
Authors: Lei Chao , Chen Shu , MacDonald Allan H.
Published: October 2020

Significance

Topological insulators have Dirac cone surface states protected by time-reversal symmetry (TRS). Weak magnetic order in topological insulator thin films can lead to the quantum anomalous Hall effect (QAHE), which was first realized by magnetic doping of topological insulators to establish a fragile ferromagnetic state. Recent work has established

MnBi

2

Te

4

as a structurally ordered magnetic topological insulator. We report on a theoretical study of superlattices formed from

M
n
B
i

2

T
e

4

and

Bi

2

Te

3

building blocks that employs a simplified model validated by ab initio density-functional theory. We use it to shed light on the dependence of the quantum anomalous Hall effect on film thickness, magnetic configuration, the stacking sequences of the van der Waals coupled building blocks, and bulk electronic structure.
Polymerase δ promotes chromosomal rearrangements and imprecise double-strand break repair
Authors: Layer Jacob V. , Debaize Lydie , Van Scoyk Alexandria , House Nealia C. , Brown Alexander J. , Liu Yunpeng , Stevenson Kristen E. , Hemann Michael , Roberts Steven A. , Price Brendan D. , Weinstock David M. , Day Tovah A.
Published: October 2020

Significance

We identify the replicative polymerase polymerase δ (Pol δ) as a promoter of aberrant DNA double-strand break end-joining events in human cells, including chromosomal translocations between targeted double-strand breaks. These studies identify a previously unknown role for Pol δ in human cells of multiple lineages and suggest a mechanism of Pol δ-dependent mutagenesis.
Transcriptional and proteomic insights into the host response in fatal COVID-19 cases
Authors: Wu Meng , Chen Yaobing , Xia Han , Wang Changli , Tan Chin Yee , Cai Xunhui , Liu Yufeng , Ji Fenghu , Xiong Peng , Liu Ran , Guan Yuanlin , Duan Yaqi , Kuang Dong , Xu Sanpeng , Cai Hanghang , Xia Qin , Yang Dehua , Wang Ming-Wei , Chiu Isaac M. , Cheng Chao , Ahern Philip P. , Liu Liang , Wang Guoping , Surana Neeraj K. , Xia Tian , Kasper Dennis L.
Published: October 2020

Significance

Although the overwhelming majority of COVID-19-related deaths are due to respiratory failure, little is known about the host response to SARS-CoV-2 in lung parenchyma. By profiling the lung and colon transcriptome and lung proteome of nine patients who died of COVID-19 during the first wave of the pandemic in Wuhan, China, we obtained molecular insights into the host response to severe SARS-CoV-2 infection. Interestingly, all samples had a low viral burden, a finding that suggests the patients’ deaths may be due to uncontrolled host inflammatory processes rather than an active viral infection. Taken together, our findings shed light on COVID-19 pathophysiology and offer potential therapeutic targets for severe COVID-19 disease.
A predictive model for electrostatic energy harvesters with impact-based frequency up-conversion
Authors: Li Jinglun , Tichy John , Borca-Tasciuc Diana-Andra
Published: October 2020

This paper reports a predictive model for vibration-to-electrical energy harvesters based on an in-plane, gap-closing variable capacitor with frequency up-conversion triggered by the impact between the electrodes. Since the output power is proportional to the output frequency, rectifying low-frequency ambient vibrations (1–50 Hz) to high-frequency electrical signals (200–600 Hz) increases the power output. While such a device has been previously reported experimentally, this is the first time a model able to predict the experimental data has been described. The model is based on lumped approximation. The central area supporting the mobile electrodes, or the shuttle mass, is represented by a point mass suspended by springs and has its own equation of motion. The motion of the electrodes attached to the shuttle is described by a set of two equations, each associated with a distinct dynamic mode. In these equations, the electrodes are represented by an equivalent mass and spring constant. The first equation describes the separate motion of mobile and fixed electrodes. In this mode, the electrodes experience damped free vibration due to the electrostatic and air damping between them. The second equation describes the combined motion when the two set of electrodes move together. In this mode the air damping forces between the collided electrodes is eliminated and the electrostatic force is kept constant. The motion equations are solved simultaneously with Kirchhoff’s law to compute the voltage drop across a resistor in series with the variable capacitor and a DC bias voltage source. Predictions are shown to be consistent with the experimental results, and frequency up-conversion effects are observed with exponentially decaying voltage amplitude as seen in experiments. A parametric study is also carried out to identify main parameters that affect the up-conversion, laying the foundation for future design optimization to maximize the power output.
Photoelectron spectra and angular distribution in sequential two-photon double ionization in the region of autoionizing resonances of ArII and KrII
Authors: Kiselev M D , Carpeggiani P A , Gryzlova E V , Burkov S M , Reduzzi M , Dubrouil A , Faccialá D , Negro M , Ueda K , Frassetto F , Stienkemeier F , Ovcharenko Y , Meyer M , Di Fraia M , Plekan O , Prince K C , Callegari C , Sansone G , Grum-Grzhimailo A N
Published: October 2020

Autoionizing hole states with electron configuration nsnp5
mp are studied in Ar+ and Kr+. Total and partial photoionization cross sections, photoelectron spectra and photoelectron angular distributions in the region of the resonances are obtained theoretically in extensive R-matrix calculations. The states of Ar+ are observed by means of excitation by a free-electron laser operating in the vacuum- and extreme-ultraviolet wavelength regime combined with angle-resolved photoelectron spectroscopy. Fine tuning of the photon energy allows scanning of the resonances and the observation of the shape of the partial cross section ratio, as well as the asymmetry parameter of the angular distribution of the photoelectrons. The calculations are in good agreement with the experimental data.