bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Effects of Various Androgens on Polycystic Ovary Syndrome
Authors: de Medeiros Sebastião Freitas , Barbosa Bruna Barcelo , de Medeiros Ana Karine Lin Winck Yamamoto , de Medeiros Matheus Antônio Souto , Yamamoto Márcia Marly Winck
Published: April 2021

The hyperandrogenism in polycystic ovary syndrome (PCOS) is associated with
the risk for the future development of the cardiovascular disease. The
objective of the study is to verify whether different androgens have the
same harmful effect. This cross-sectional study enrolled 823 women with
PCOS: 627 (76.2%) with biochemical hyperandrogenism and 196
(23.8%) with normal androgen levels. The role of individual androgen
was evaluated using univariate and multivariate logistic regression. In
normoandrogenemic PCOS (NA-PCOS), free androgen index (FAI) predicted
significant abnormality in visceral adipose index (VAI, OR=9.2,
p=0.002) and dehydroepiandrosterone (DHEA) predicted against
alteration in β-cell function (OR=0.5, p=0.007). In
hyperandrogenemic PCOS (HA-PCOS), FAI predicted derangements in waist
triglyceride index (WTI), VAI, and lipid accumulation product (LAP) (OR
ranging from 1.6 to 5.8, p<0.05). DHEA weakly predicted against VAI
(OR 0.7, p=0.018), dehydroepiandrosterone sulfate (DHEAS) tended to
predict against the conicity index (OR=0.7, p=0.037). After
multiple regression, FAI retained significant strength to predict various
anthropometric and metabolic abnormalities (OR ranging from 1.1 to 3.0,
p<0.01), DHEA was kept as a protector factor against WTI, LAP, and
VAI (OR ranging from 0.6 to 0.9; p<0.01) and DHEAS against the
conicity index (OR=0.5, p<0.001). In conclusion, the free
androgen index was the most powerful predictor of anthropometric and
metabolic abnormalities of polycystic ovary syndrome. Conversely, DHEA and
DHEAS demonstrated protective effects against disorders in some markers of
obesity and abnormal metabolism.
Improving Postpartum Attendance among Women with Gestational Diabetes Using the Medical Home Model of Care
Authors: Soffer Marti D. , Rekawek Patricia , Pan Stephanie , Overbey Jessica , Stone Joanne
Published: April 2021

Objective Poor attendance at the 6-week postpartum (PP) visit has been well reported. Attendance at this visit is crucial to identify women who have persistent diabetes mellitus (DM) following pregnancies affected by gestational DM (GDM). The medical home model has eliminated barriers to care in various other settings. This study sought to improve PP attendance among women with GDM by jointly scheduling PP visits and the 2-month well infant visits.

Study Design All patients with a diagnosis of GDM who received care at a New York City–based publicly insured hospital clinic and delivered between October 2017 and June 2019 were eligible. Data were obtained via chart review. The primary outcome was attendance at the PP visit compared with previously published historical controls. Secondary outcomes were rates of PP glucose screening and well infant attendance.

Results Of the 74 patients enrolled, 41.9% were Hispanic and 17.6% were Black, mean age was 31.6 years, and 58.1% delivered vaginally. Attendance at the 6-week PP visit was 68.9%, and attendance at the infant visit was 55.1%. PP glucose testing was ordered for 76.5% of attendees at the PP visit, and of those ordered, 43.6% of attendees completed testing. All patients had joint visits requested, though only 70.3% of visits were scheduled jointly. Among those who were jointly scheduled, 71.2% of women attended, 57.7% of infants attended, and 7.7% of pairs attended on the same day. The PP visit attendance rate was not significantly different than the prior attendance rate (p = 0.84).

Conclusion This study was unable to improve PP visit attendance among women with GDM by jointly scheduling the 6-week PP visit and the 2-month well-infant visit. Future research could be directed toward a shared space where both women and children can be seen to attempt to increase PP visit attendance and monitoring for women with GDM.

Key Points
Interpregnancy Body Mass Index Change and Offspring Mortality Risk following the Second Pregnancy
Authors: Dude Annie M. , Smid Marcela C. , Branch D. Ware , West Jennifer , Meeks Huong , Yu Zhe , Fraser Alison , Smith Ken , Reddy Deepika
Published: April 2021

Objective The aim of the study is to examine the impact of maternal interpregnancy body mass index (BMI) change on subsequent offspring mortality risk.

Study Design This is a retrospective cohort study of women who had two consecutive live singleton deliveries of at least 20 weeks' gestation from the Utah Population Database. Our exposure was defined as interpregnancy BMI change from the date of first delivery to the conception date of subsequent pregnancy. We categorized BMI change as: < − 1, −1 to 0, 0 to <1 (reference), 1 to 2, 2 to 4, ≥4 kg/m2. Our primary outcome was all-cause age-specific mortality during four time periods: neonatal (≤28 days), infant (29 days to <1 year old), childhood ((≥1 to <5 years old), and late childhood (5 to <18 years old). We also examined mortality specifically attributed to congenital anomalies. Analyses used Cox proportional hazard models stratified by full term (≥37 weeks) and preterm (<37 weeks) deliveries. All models were adjusted for relevant confounders.

Results Of 266,752 women, among full-term deliveries, women with a BMI increase of 4 kg/m2 or more had an increased risk of neonatal mortality in their subsequent pregnancy (hazard ratio or HR = 1.72, 95% confidence interval or CI: 1.23–2.41) Women who lost 1 kg/m2 or more between deliveries also had increased neonatal mortality (HR = 1.46, 95% CI: 1.04–2.05). There were no differences in infant, early, or late childhood mortality by interpregnancy BMI change. Maternal interpregnancy interval weight loss of 1 kg/m2 or more and weight gain of ≥4 kg/m2 also had increased risk of mortality associated with congenital anomalies or conditions arising during the neonatal period following their subsequent delivery.

Conclusion Women with significant interpregnancy weight gain and modest weight loss have a significant increased risk of neonatal mortality following their subsequent pregnancy.

Key Points
Dynamics of large boson systems with attractive interaction and a derivation of the cubic focusing NLS equation in R3
Authors: Chong Jacky
Published: April 2021

We consider a system of N bosons where the particles experience a short-range two-body interaction given by N−1vN(x) = N3β−1v(Nβx), where v∈Cc∞(R3), without a definite sign on v. We extend the results of Grillakis and Machedon [Commun. Math. Phys. 324(2), 601–636 (2013)] and Kuz [Differ. Integral Equations 30(7/8), 587–630 (2017)] regarding the second-order correction to the mean-field evolution of systems with repulsive interaction to systems with attractive interaction for 0<β<12. Our extension allows for a more general set of initial data, which includes coherent states. We also provide both a derivation of the focusing nonlinear Schrödinger equation in 3D from the many-body system and its rate of convergence toward mean-field for 0<β<13.
Sputtering of Mo and Ag with xenon ions from a radio-frequency ion thruster
Authors: Buntrock L. J. , Volkmar C. , Hannemann K.
Published: April 2021

The goal of this work is to set up an electric propulsion (EP) sputtering test section as a feasibility study for ground-based sputter testing of spacecraft materials with a radio-frequency ion thruster. Such experiments deliver valuable data, which are scarce but highly desired to model EP-based space missions, for example, with the Spacecraft Plasma Interaction System in order to predict the performance and lifetime of spacecraft components. This study assessed if sufficient testing conditions can be met to produce reliable experimental material data in the future. Therefore, the thruster was operated at ion energies of 1.5 and 1.8 keV, and a quartz crystal microbalance (QCM) was installed to detect sputter deposition rates. Molybdenum (Mo) and silver (Ag) were chosen as sputter targets. Wafer substrates served as a passive sampling method to characterize the composition of sputtered material by Rutherford backscattering spectrometry. Additionally, sputtering simulations matching the experimental conditions were performed with the software SDTrimSP. We obtained comparable experimental and computational data, as measured sputter deposition rates lie within the simulated order of magnitude and to some extent show the predicted angular dependence. Analysis of the deposited sputter material revealed the formation of metal oxides, which requires a future adaption of the material specific QCM settings. Furthermore, the cooling system of the QCM sensor head was not sufficient, limiting the comparability of results.
Almost exponential decay of the Boussinesq equations without surface tension on the upper free boundary
Authors: Xie Binqiang , Zeng Lan
Published: April 2021

In this paper, we prove the global existence and almost exponential decay of solutions for a Boussinesq approximation Bénard convection fluid. Compared with our previous paper [B. Guo, B. Xie, and L. Zeng, J. Differ. Equations 267, 2261–2283 (2019)], here the effect of the surface tension is neglected on the free surface. The analysis needs more higher regularity than the surface tension case.
Defect structures in (001) zincblende GaN/3C-SiC nucleation layers
Authors: Vacek Petr , Frentrup Martin , Lee Lok Yi , Massabuau Fabien C.-P. , Kappers Menno J. , Wallis David J. , Gröger Roman , Oliver Rachel A.
Published: April 2021

The defect structure of zincblende GaN nucleation layers grown by metalorganic vapor-phase epitaxy on 3C-SiC/Si (001) was investigated by high-resolution scanning transmission electron microscopy. Perfect dislocations, partial dislocations, and stacking faults are present in the layers. Perfect dislocations are identified as 60° mixed-type and act as misfit dislocations to relieve the compressive lattice mismatch strain in GaN. Stacking faults are mainly bounded by 30° Shockley partial dislocations and rarely by Lomer–Cottrell partial dislocations, both of which are able to relieve the compressive lattice mismatch strain in the layer. We propose that the stacking faults and their partial dislocations originate from the dissociation of perfect dislocations present in the zincblende GaN layer and by direct nucleation of partial dislocations loops from the surface. These are the two main mechanisms that lead to the final defect structure of the zincblende GaN nucleation layers.
Stochastic modeling of Lévy-like human eye movements
Authors: Błażejczyk Piotr , Magdziarz Marcin
Published: April 2021

The standard model of visual search dynamics is Brownian motion. However, recent research in cognitive science reveals that standard diffusion processes seem not to be the appropriate models of human looking behavior. In particular, experimental results confirm that the superdiffusive Lévy-type dynamics appears in this context. In this paper, we analyze the diffusive properties of human eye movement in a language comprehension task. We propose a model that is a combination of a Markov chain with a finite number of states and a Lévy walk. Our model fits well the experimental data and allows one to investigate the properties of the visual search dynamics using numerical simulations.
Perturbations of circuit evolution matrices with Jordan blocks
Authors: Figotin Alexander
Published: April 2021

In our prior studies, we synthesized special circuits with evolution matrices featuring degenerate eigenfrequencies and nontrivial Jordan blocks. The degeneracy of this type is sometimes referred to as exceptional point of degeneracy (EPD). Our focus here is on the simplest of our circuits featuring EPDs that are composed of only two LC-loops coupled by a gyrator. These circuits, when near an EPD state, can be used for enhanced sensitivity applications. With that in mind, we develop here a comprehensive perturbation theory for these simple circuits near an EPD. Using this theory, we propose an approach to sensing, allowing one to benefit from the proximity to an EPD on the one hand when providing for stable operation on the other hand. We also address a broader scope of problems related to perturbations of Jordan blocks and their numerical treatment that allow us to effectively detect proximity to Jordan blocks.
Dispersive readout of reconfigurable ambipolar quantum dots in a silicon-on-insulator nanowire
Authors: Duan Jingyu , Lehtinen Janne S. , Fogarty Michael A. , Schaal Simon , Lam Michelle M. L. , Ronzani Alberto , Shchepetov Andrey , Koppinen Panu , Prunnila Mika , Gonzalez-Zalba Fernando , Morton John J. L.
Published: April 2021

We report on ambipolar gate-defined quantum dots in silicon on insulator nanowires fabricated using a customized complementary metal–oxide–semiconductor process. The ambipolarity was achieved by extending a gate over an intrinsic silicon channel to both highly doped n-type and p-type terminals. We utilize the ability to supply ambipolar carrier reservoirs to the silicon channel to demonstrate an ability to reconfigurably define, with the same electrodes, double quantum dots with either holes or electrons. We use gate-based reflectometry to sense the inter-dot charge transition (IDT) of both electron and hole double quantum dots, achieving a minimum integration time of 160 (100) μs for electrons (holes). Our results present the opportunity to combine, in a single device, the long coherence times of electron spins with the electrically controllable hole spins in silicon.
Data analysis scheme for correcting general misalignments of an optics configuration for a voltage measurement system based on the Pockels electro-optic effect
Authors: Choi Seongmin , Lee Dong-Geun , Woo H. J. , Hong S. H. , Ham Seunggi , Ryu Jonghyeon , Chung Kyoung-Jae , Hwang Y. S. , Ghim Y.-c.
Published: April 2021

Having a sub-ns response time and not requiring physical contacts to the measurement points, a voltage measurement system based on the Pockels electro-optic effect, referred to as a PE (Pockels effect)-based voltmeter, is widely used for pulsed high voltage devices such as accelerators and X-pinch systems. To correct for the misalignment of a Pockels cell and the transmittance ratio of a beam splitter, a polar-coordinate-based data analysis scheme has been proposed. This scheme also overcomes a limitation on the measurable range of a PE-based voltmeter without ambiguity and can measure the half-wave voltage of a Pockels cell. We present an improved polar-coordinate-based data analysis scheme using an ellipse fitting method, which can correct for misalignments of all the optics components of a PE-based voltmeter while keeping the advantages of the previous scheme. We show the results of the improved data analysis scheme for measuring a slowly modulated voltage up to approximately 5 kV in about 30 s and a pulsed high voltage up to 7 kV with a rise time of less than 20 ns.
From nanotubes to nanoholes: Scaling of selectivity in uniformly charged nanopores through the Dukhin number for 1:1 electrolytes
Authors: Sarkadi Zsófia , Fertig Dávid , Ható Zoltán , Valiskó Mónika , Boda Dezső
Published: April 2021

Scaling of the behavior of a nanodevice means that the device function (selectivity) is a unique smooth and monotonic function of a scaling parameter that is an appropriate combination of the system’s parameters. For the uniformly charged cylindrical nanopore studied here, these parameters are the electrolyte concentration, c, voltage, U, the radius and the length of the nanopore, R and H, and the surface charge density on the nanopore’s surface, σ. Due to the non-linear dependence of selectivities on these parameters, scaling can only be applied in certain limits. We show that the Dukhin number, Du=|σ|/eRc∼|σ|λD2/eR (λD is the Debye length), is an appropriate scaling parameter in the nanotube limit (H → ∞). Decreasing the length of the nanopore, namely, approaching the nanohole limit (H → 0), an alternative scaling parameter has been obtained, which contains the pore length and is called the modified Dukhin number: mDu ∼ Du H/λD ∼ |σ|λDH/eR. We found that the reason for non-linearity is that the double layers accumulating at the pore wall in the radial dimension correlate with the double layers accumulating at the entrances of the pore near the membrane on the two sides. Our modeling study using the Local Equilibrium Monte Carlo method and the Poisson–Nernst–Planck theory provides concentration, flux, and selectivity profiles that show whether the surface or the volume conduction dominates in a given region of the nanopore for a given combination of the variables. We propose that the inflection point of the scaling curve may be used to characterize the transition point between the surface and volume conductions.
Measuring cellular contraction: Current progress and a future in
bioelectronics
Authors: Boys Alexander J. , Owens Róisín M.
Published: April 2021

Cellular contraction is a universal phenomenon that drives various processes in the body. As such, measurement of cell contractility is of great interest to the scientific community. However, contracting cells apply very small stresses, which can be difficult to monitor. Various techniques have been developed to overcome these issues, with resolutions extending to the single cell level. Despite significant progress in this field, many limitations remain, including the ability to measure contraction instantaneously and in vivo. Bioelectronics involve the application of electric fields or electrically responsive materials for measurement or stimulation in biology. Bioelectronic devices have the major potential to overcome some of the remaining challenges in monitoring cell contraction, given their ability to provide fast, non-invasive measurements. In this forward-looking perspective, we will discuss the development of contractile measurement technologies as well as new areas that require growth and the potential for application of bioelectronics in this field.
Optical and magnetic properties of Sm-doped BiFeO3 nanoparticles around the morphotropic phase boundary region
Authors: Gu Yanhong , Zhou Yan , Zhang Weiying , Guo Chaoyang , Zhang Xianghui , Zhao Jianguo , Zhang Yaju , Zheng Haiwu
Published: April 2021

The crystal structure, photocatalytic activity, and ferromagnetic properties of Sm-substituted (Bi1−xSmxFeO3, x = 0.05, 0.10, 0.15, 0.20) nanoparticles were systematically investigated within the entire Sm substitution region. The morphotropic phase boundary (MPB) consisting of a rhombohedral phase, orthorhombic interim phase (Pna21), and orthorhombic phase with 0.1 ≤ x ≤ 0.2 is constructed and confirmed by x-ray diffraction and Raman spectra with new vibration modes at ∼310 cm−1. The photocatalytic activity and ferromagnetism are improved around the MPB region (x = 0.10). Meanwhile, the wasp-waisted hysteresis loops are present around the MPB region. Wasp-waisted hysteresis loops have the features of low hysteresis loss in low magnetic fields and are helpful in designing some multiferroic devices.
Two-relaxation time lattice Boltzmann models for the ion transport equation in electrohydrodynamic flow: D2Q5 vs D2Q9 and D3Q7 vs D3Q27
Authors: Zhu Baojie , Guan Yifei , Wu Jian
Published: April 2021

Two commonly used discrete velocity models [the linear discrete velocity model (LDVM) and the full discrete velocity model (FDVM)] are investigated using the two-relaxation time lattice Boltzmann method coupled to a fast Poisson solver in an electroconvection system. We derived analytically the LDVM, i.e., D2Q5 and D3Q7 and FDVM, i.e., D2Q9 and D3Q27, for the ion transport equation (convection–diffusion–drift equation) in both two- and three-dimensional systems. The analytical results indicate that the error terms in LDVM are higher orders and can be neglected in practical simulations. The numerical results of LDVM and FDVM are quantitatively compared, showing the differences between the models' prediction in charge density, velocity, and stability hysteresis loops. The numerical results are consistent with the theoretical analysis. We perform all the simulations using graphics processing units, and the computational efficiency is measured via the wall clock time. We find that the LDVM can substitute FDVM in certain conditions with a substantial saving in computational costs and a small sacrifice in accuracy.
Space charge limited current with distributed velocity of initial electrons in planar diode
Authors: Wang Jianguo , Chen Jiannan , Cai Libing , Chen Zaigao , Ren Zeping
Published: April 2021

The research on the space-charge limited current is of great importance for developing insight into the high current diodes. The Child-Langmuir law presents one-dimensional (1D) space-charge limited current density by considering a full electrostatic solution. Jaffe investigated the 1D space-charge limited current density modified by the uniform initial velocity of electrons emitted from the cathode by using the equation of motion for the individual electron. Luginsland et al. presented the two-dimensional (2D) space-charge limited current density by using the particle-in-cell (PIC) codes neglecting initial velocity distribution of the emitted electrons. In this Letter, the effects of initial electrons with the uniform energy distribution and thermal equilibrium distribution on the space charge limited current density are studied by using the full electromagnetic PIC method; the 2D modification factors to the space charge limited current density for the two cases are presented and discussed.
Application of sparse grid combination techniques to low temperature plasmas particle-in-cell simulations. I. Capacitively coupled radio frequency discharges
Authors: Garrigues L. , Tezenas du Montcel B. , Fubiani G. , Bertomeu F. , Deluzet F. , Narski J.
Published: April 2021

The use of a particle-in-cell (PIC) algorithm with an explicit scheme to model low temperature plasmas is challenging due to computational time constrains related to resolving both the electron Debye length in space and the inverse of a fraction of the plasma frequency in time. One recent publication [Ricketson and Cerfon, Plasma Phys. Control. Fusion 59, 024002 (2017)] has demonstrated the interest of using a sparse grid combination technique to accelerate the explicit PIC model. Simplest plasma conditions were considered. This paper is the demonstration of the capability and the effectiveness of the sparse grid combination technique embedded in the PIC algorithm (hereafter called “sparse PIC”) to self-consistently model capacitively coupled radio frequency discharges. For two-dimensional calculations, the sparse PIC approach is shown to accurately reproduce the plasma profiles and the energy distribution functions compared to the standard PIC model. The plasma parameters obtained by these two numerical methods differ by less than 5%, while a speed up in the executable time between 2 and 5 is obtained depending on the setup.
Application of sparse grid combination techniques to low temperature plasmas Particle-In-Cell simulations. II. Electron drift instability in a Hall thruster
Authors: Garrigues L. , Tezenas du Montcel B. , Fubiani G. , Reman B. C. G.
Published: April 2021

Three-dimensional simulations of partially magnetized plasma are real challenges that actually limit the understanding of the discharge operations such as the role of kinetic instabilities using explicit Particle-In-Cell (PIC) schemes. The transition to high performance computing cannot overcome all the limits inherent to very high plasma densities and thin mesh sizes employed to avoid numerical heating. We have applied a recent method proposed in the literature [L. F. Ricketson and A. J. Cerfon, Plasma Phys. Controlled Fusion 59, 024002 (2017)] to model low temperature plasmas. This new approach, namely, the sparse grid combination technique, offers a gain in computational time by solving the problem on a reduced number of grid cells, hence allowing also the reduction of the total number of macroparticles in the system. We have modeled the example of the two-dimensional electron drift instability, which was extensively studied in the literature to explain the anomalous electron transport in a Hall thruster. Comparisons between standard and sparse grid PIC methods show an encouraging gain in the computational time with an acceptable level of error. This method offers a unique opportunity for future three-dimensional simulations of instabilities in partially magnetized low temperature plasmas.
Effect of mosaicity on energy storage performance of epitaxial BaZr0.35Ti0.65O3 films
Authors: Liang Zhongshuai , Ma Chunrui , Dai Yanzhu , Du Xianfeng , Liu Ming
Published: April 2021

It is well known that the macroscopic behaviors of ferroelectric materials were tightly related to their microstructure features. In this work, the mosaicity of epitaxial BaZr0.35Ti0.65O3 films was studied by analyzing the broadening effect of reciprocal lattice points. The smaller transverse block size (Dx) and relatively large tilt angle of crystal blocks (Δω) were suggested to promote the delay saturation of polarization. Meanwhile, the electric breakdown strength (EB) could be enhanced in the samples with smaller Dx, which can further improve the energy storage density efficiently. Ultimately, an ultrahigh recoverable energy density (Wrec) of 100.8 J/cm3 was achieved in the BaZr0.35Ti0.65O3 films prepared at 700 °C.
Blood backspatter interaction with propellant gases
Authors: Li Gen , Sliefert Nathaniel , Michael James B. , Yarin Alexander L.
Published: April 2021

The theoretical results of the present work reveal a significant interaction of the oncoming vortex ring of propellant muzzle gases with backward blood spatter. It is shown that there is even possibility that a blood droplet from the backspatter will fully turn around by a powerful vortex ring and land behind a victim. Such a predicted outcome is confirmed by experimental data of fully reversed drop trajectories observed in the experiments conducted in the second part of this work [N. Sliefert, G. Li, J. B. Michael, A. L. Yarin, “Experimental and numerical study of blood backspatter interaction with propellant gases,” Phys. Fluids 33, 043319 (2021)]. A parametric study is conducted here to investigate the totality of the outcomes of the vortex ring interaction with the backward blood spatter and the corresponding deflections and landing locations of blood drops. Furthermore, a secondary vortex ring is introduced here to reveal a continuous effect of the propellant gas.
Experimental and numerical study of blood backspatter interaction with firearm propellant gases
Authors: Sliefert Nathaniel , Li Gen , Michael James B. , Yarin Alexander L.
Published: April 2021

Experiments are used to quantify the influence of propellant gases on blood backspatter and the numerical model presented in the first part of this work (G. Li, N. Sliefert, J. B. Michael, A. L. Yarin, Phys. Fluids, 33, 043318 (2021)) is compared with the experimental results, which stem from muzzle gas expansion. Experimental results with blood backspatter show the reversal of backspatter blood drops and also indicate the presence of secondary atomization induced by the high relative velocity of the oncoming muzzle gases and the backward propagating bullet-induced blood spatter. To characterize the degree of influence, the muzzle gases for a range of modified and unmodified rifle and pistol configurations are considered. These muzzle gas expansions are used to infer the parameters of the numerical model presented in the first part. The significant effects of muzzle gases on blood backspatter have important implications for the use of forensic analysis of deposited bloodstain patterns, where flow reversal and breakup may significantly alter the forensic evidence.
Polarization singularities: Progress, fundamental physics, and prospects
Authors: Wang Qiang , Tu Cheng-Hou , Li Yong-Nan , Wang Hui-Tian
Published: April 2021

Polarization singularities, describing the points where the state of polarization is indeterminate, reveal the polarization topology in vectorial optical fields, which include two-/three-dimensional topologies such as C-points, V-points, L-lines, Möbius strips, links, and knots. Compared with the phase singularities, it has more parameters to manipulate, which bring forth a series of novel optical phenomena and potential applications. In this Perspective, the research progress and development of polarization singularities are reviewed from the mathematical description, generation, detection, propagation dynamics, and related applications. In particular, we focused on the three-dimensional spatial propagation and the topological characteristics of polarization singularities in detail and revealed some basic fundamental physical phenomena and the novel effects of polarization singularities. We aim to touch on the key research studies in this field and provide insight into the current status and the challenges to the research studies. Finally, we outline the exciting prospects for the future that are yet to be realized.
Biocompatible miniature temperature sensor based on whispering gallery modes of Sm3+ activated ZnO optical micro-resonators
Authors: Fabitha K. , Ramachandra Rao M. S.
Published: April 2021

Toward achieving an efficient micro-optical temperature sensor in a wide visible spectral range, Sm3+:ZnO micro-spheres are fabricated by the laser ablation technique. Visible range whispering gallery mode resonances are observed and are found to be lasing above low optical threshold with a quality factor of the order of 103. A temperature-induced change in whispering gallery modes is observed with a sensitivity of 0.04 nm/°C from the micro-sphere of diameter 10.5 μm. Using these results, cost-effective and bio-compatible miniature temperature sensors that operate in the visible spectral range could be devised.
Large spin to charge conversion in antiferromagnetic Weyl semimetal Mn3Sn
Authors: Yu Tian , Wu Hao , He Haoran , Guo Chenyang , Fang Chi , Zhang Peng , Wong Kin L. , Xu Shijie , Han Xiufeng , Wang Kang L.
Published: April 2021

The Weyl antiferromagnet Mn3Sn has recently attracted significant attention as it is not only a novel magnetic quantum material of fundamental interest, but it also opens opportunities to investigate a number of exotic spin-dependent transports for practical antiferromagnetic devices. Here, we report the large spin to charge conversion observed in YIG/Mn3Sn. Evidenced by both spin Seebeck and spin pumping measurements, the spin to charge conversion efficiency of Mn3Sn is found ∼2.5 times of that for the conventional heavy metal Ta. Our results suggest a promising potential for employing a topological non-trivial antiferromagnet to achieve more efficient spin to charge conversion than conventional metallic materials.
Effect of the supporting disks shape on nonlinear flow dynamics in a liquid bridge
Authors: Gaponenko Y. , Yasnou V. , Mialdun A. , Nepomnyashchy A. , Shevtsova V.
Published: April 2021

The stability of convective flows in a non-homogeneous temperature field is affected by the shape of the container hosting the fluid. We present a nonlinear two-phase computational study of convection in a liquid bridge that develops under the action of buoyancy and Marangoni forces. The hydrothermal instability is examined for three shapes of disks supporting liquid bridge: both disks flat, the upper (hot) disk tapered, and the lower (cold) disk tapered. Steady flow is also analyzed for the case that both disks are tapered. In all the cases of instability, the flow pattern comprises, but is not limited to, a hydrothermal wave with an azimuthal wavenumber m = 2. An intriguing flow pattern is observed in the case of flat disks when the nonlinear interaction between the modes m = 0 and m = 2 leads to quasiperiodic motion forming a torus in the phase space. The torus originates from two traveling waves (TW) with the same mode m = 2 but with distinct (close) frequencies. Note that this was not observed in the one-phase model. The case with a tapered cold disk reveals an oscillatory state with a single TW wave associated with m = 2 mode. In the case of a tapered hot disk, an axially symmetric TW with m = 0 is observed first and, at later times, is accompanied by a TW with m = 2.
Anisotropy in fifth-order exciton–exciton-interaction two-dimensional spectroscopy
Authors: Lüttig Julian , Brixner Tobias , Malý Pavel
Published: April 2021

Exciton–exciton-interaction two-dimensional (EEI2D) spectroscopy is a fifth-order variant of 2D electronic spectroscopy. It can be used to probe biexciton dynamics in molecular systems and to observe exciton diffusion in extended systems such as polymers or light-harvesting complexes. The exciton transport strongly depends on the geometrical and energetic landscape and its perturbations. These can be of both local character, such as molecular orientation and energetic disorder, and long-range character, such as polymer kinks and structural domains. In the present theoretical work, we investigate the anisotropy in EEI2D spectroscopy. We introduce a general approach for how to calculate the anisotropy by using the response-function formalism in an efficient way. In numerical simulations, using a Frenkel exciton model with Redfield-theory dynamics, we demonstrate how the measurement of anisotropy in EEI2D spectroscopy can be used to identify various geometrical effects on exciton transport in dimers and polymers. Investigating a molecular heterodimer as an example, we demonstrate the utility of anisotropy in EEI2D spectroscopy for disentangling dynamic localization and annihilation. We further calculate the annihilation in extended systems such as conjugated polymers. In a polymer, a change in the anisotropy provides a unique signature for exciton transport between differently oriented sections. We analyze three types of geometry variations in polymers: a kink, varying geometric and energetic disorder, and different geometric domains. Our findings underline that employing anisotropy in EEI2D spectroscopy provides a way to distinguish between different geometries and can be used to obtain a better understanding of long-range exciton transport.
Observation and characterization of impact ionization-induced OFF-state breakdown in Schottky-type p-GaN gate HEMTs
Authors: Cheng Yan , Wang Yuru , Feng Sirui , Zheng Zheyang , Chen Tao , Lyu Gang , Ng Yat Hon , Chen Kevin J.
Published: April 2021

In this work, the impact ionization-induced OFF-state breakdown is revealed and systematically investigated in 100 V Schottky-type p-GaN gate high-electron-mobility transistors. Impact ionization is found to occur in the peak electric-field region at the source-terminated field-plate edge and is initiated by electrons injected from the source-side two-dimensional electron gas channel through the buffer layer. Hot electrons generated from impact ionization, when being captured by surface traps, could lead to redistribution and peak value reduction of electric-field. Consequently, the sudden rise in the OFF-state leakage current by impact ionization could be self-clamped temporally to avoid catastrophic rupture of the device. The impact ionization is further verified by the increase in dynamic OFF-state leakage current and a negative shift in threshold voltage, both of which result from positively charged holes (generated from impact ionization) drifting toward the gated channel.
Numerical study of COVID-19 spatial–temporal spreading in London
Authors: Zheng Jie , Wu Xiaofei , Fang Fangxin , Li Jinxi , Wang Zifa , Xiao Hang , Zhu Jiang , Pain Christopher , Linden Paul , Xiang Boyu
Published: April 2021

A recent study reported that an aerosolized virus (COVID-19) can survive in the air for a few hours. It is highly possible that people get infected with the disease by breathing and contact with items contaminated by the aerosolized virus. However, the aerosolized virus transmission and trajectories in various meteorological environments remain unclear. This paper has investigated the movement of aerosolized viruses from a high concentration source across a dense urban area. The case study looks at the highly air polluted areas of London: University College Hospital (UCH) and King's Cross and St Pancras International Station (KCSPI). We explored the spread and decay of COVID-19 released from the hospital and railway stations with the prescribed meteorological conditions. The study has three key findings: the primary result is that the concentration of viruses decreases rapidly by a factor of 2–3 near the sources although the virus may travel from meters up to hundreds of meters from the source location for certain meteorological conditions. The secondary finding shows viruses released into the atmosphere from entry and exit points at KCSPI remain trapped within a small radial distance of < 50 m. This strengthens the case for the use of face coverings to reduce the infection rate. The final finding shows that there are different levels of risk at various door locations for UCH; depending on which door is used there can be a higher concentration of COVID-19. Although our results are based on London, since the fundamental knowledge processes are the same, our study can be further extended to other locations (especially the highly air polluted areas) in the world.
Propagation of one-dimensional planar and nonplanar shock waves in nonideal radiating gas
Authors: Singh Mayank , Arora Rajan
Published: April 2021

The present study seeks to investigate a quasilinear hyperbolic system of partial differential equations which describes the unsteady one-dimensional motion of a shock wave of arbitrary strength propagating through a nonideal radiating gas. We have derived an infinite hierarchy of the transport equation which is based on the kinematics of one-dimensional motion of shock front. By using the truncation approximation method, an infinite hierarchy of transport equations, which governs the shock strength and the induced discontinuities behind it, is derived to study the kinematics of the shock front. The first three transport equations (i.e., first, second, and third-orders) are used to study the growth and decay behavior of shocks in van der Waals radiating gas. The decay laws for weak shock waves in nonradiating gas are entirely recovered in the second-order truncation approximation. The results obtained by the first three approximations for shock waves of arbitrary strength are compared with the results predicted by the characteristic rule. Also, the effect of nonideal parameters and radiation on the evolutionary behavior of shock waves are discussed and depicted pictorially.
Optical coherence viscometry
Authors: Liu Hsiao-Chuan , Urban Matthew W.
Published: April 2021

We report a technique, named optical coherence viscometry (OCV), to measure the viscosity of Newtonian fluids in a noncontact manner. According to linear wave theory with small amplitudes, capillary waves are associated with fluid mechanical properties. To perform this measurement and avoid the overdamped effects of capillary waves in viscous fluids, transient acoustic radiation force was applied to generate capillary waves. Within a very limited field-of-view using optical coherence tomography, wave motion acquired in the time domain was analyzed using Fourier methods to study the wave velocity dispersion and attenuation relationships for capillary waves, which can reduce the fluid quantity drastically into tissue culture scale. We measure the viscosities of water, water–glycerol solutions with three concentrations, and biological plasma using the proposed OCV and compare the experimental results to theoretical calculations. OCV is sensitive to wave perturbations and can be a promising technique for measuring the viscosity of biological fluids and could be applied in future applications for measurements for lipid membranes in cell biology and tissue engineering investigation.
Angularly tunable perfect absorption in graphene-mushroom hybrid structure for all angles
Authors: Xue Zhen , Zhong Shuomin , Wang Xuchen , Ma Yungui
Published: April 2021

In this work, the authors propose a graphene-based tunable perfect metamaterial absorber at microwaves that can achieve perfect absorption at all angles. This is realized by stacking an unpatterned graphene sandwich structure and a dielectric layer on top of a mushroom-type high impedance surface whose resonant frequency is stable for all angles of incidence. A perfect-absorption-angle tunable absorber working at TM polarization is designed and realized, achieving perfect absorption covering a wide range of angles from normal to grazing incidence at the same frequency when the impedance of graphene is modulated by different bias voltages. The design concept of integrating different tunable materials and meta-structures opens up promising possibilities for wave manipulation with applications in smart and multifunctional electromagnetic devices.
Aerodynamics of two-dimensional bristled wings in low-Reynolds-number flow
Authors: Wu Yu Kai , Liu Yan Peng , Sun Mao
Published: April 2021

The smallest flying insects commonly possess bristled wings and use drag to provide flight forces. A bristled wing, with a wing area about 10% of that of a flat-plate wing, operating at the relevant Reynolds number of 5–15, produces a drag close to the plate wing. How this is done is not well understood. Here, detailed flows around each of the bristles are investigated numerically using simple model wings, and the following results are shown. (1) The drag production mechanism of the bristled wing is different from that of the plate wing: For the plate wing, the flow is blocked by the wing, giving a small positive pressure on the windward surface, and there exists a pair of weak vortices on the wing back, giving a small negative pressure on the leeward surface; the drag is due to the pressure forces (the frictional stress has almost no contribution). For the bristled wing, each bristle operates in a creeping flow and produces thick and strong shear layers. Strong viscous force generates a very large pressure difference between the windward and leeward surfaces of each bristle and very large frictional stress on the bristle surface, resulting in a large drag on each bristle, and the drag is equally contributed by the pressure and frictional forces. (2) Due to the flow-interference effect, when the bristle number reaches a certain value, a further increase in bristles has little effect on force production but has the disadvantage of increasing wing mass; this means that for a bristled wing of miniature insects, the distribution density of the bristles will not be too large, which agrees with observations.
Phase coalescence in a population of heterogeneous Kuramoto oscillators
Authors: Phogat Richa , Ray Arnob , Parmananda P. , Ghosh Dibakar
Published: April 2021

Phase coalescence (PC) is an emerging phenomenon in an ensemble of oscillators that manifests itself as a spontaneous rise in the order parameter. This increment in the order parameter is due to the overlaying of oscillator phases to a pre-existing system state. In the current work, we present a comprehensive analysis of the phenomenon of phase coalescence observed in a population of Kuramoto phase oscillators. The given population is divided into responsive and non-responsive oscillators depending on the position of the phases of the oscillators. The responsive set of oscillators is then reset by a pulse perturbation. This resetting leads to a temporary rise in a macroscopic observable, namely, order parameter. The provoked rise thus induced in the order parameter is followed by unprovoked increments separated by a constant time τPC. These unprovoked increments in the order parameter are caused due to a temporary gathering of the oscillator phases in a configuration similar to the initial system state, i.e., the state of the network immediately following the perturbation. A theoretical framework corroborating this phenomenon as well as the corresponding simulation results are presented. Dependence of τPC and the magnitude of spontaneous order parameter augmentation on various network parameters such as coupling strength, network size, degree of the network, and frequency distribution are then explored. The size of the phase resetting region would also affect the magnitude of the order parameter at τPC since it directly affects the number of oscillators reset by the perturbation. Therefore, the dependence of order parameter on the size of the phase resetting region is also analyzed.
Small noncoding RNA profiling across cellular and biofluid compartments and their implications for multiple sclerosis immunopathology
Authors: Zheleznyakova Galina Yurevna , Piket Eliane , Needhamsen Maria , Hagemann-Jensen Michael , Ekman Diana , Han Yanan , James Tojo , Khademi Mohsen , Al Nimer Faiez , Scicluna Patrick , Huang Jesse , Kockum Ingrid , Faridani Omid R. , Olsson Tomas , Piehl Fredrik , Jagodic Maja
Published: April 2021

Significance

Dysregulation of microRNAs (miRNAs), a type of small noncoding RNAs (sncRNAs), has frequently been associated with multiple sclerosis (MS). However, most studies have focused on peripheral blood, and few investigated other classes of sncRNAs. To address this, we analyzed all classes of sncRNAs in matching peripheral blood mononuclear cells, plasma, cerebrospinal fluid (CSF) cells, and cell-free CSF from MS patients and controls. We demonstrate widespread alterations of small nuclear (snRNA)–derived RNAs, small nucleolar-derived RNAs (sdRNAs), transfer RNA–derived fragments, and miRNAs, particularly in CSF cells. The striking contrast between the periphery and central nervous system and between relapse and remission phases of disease highlights the importance of sncRNA-mediated mechanisms in MS, in particular alternative splicing and mRNA translation.
Enhanced Ca2+signaling, mild primary aldosteronism, and hypertension in a familial hyperaldosteronism mouse model (Cacna1hM1560V/+)
Authors: Seidel Eric , Schewe Julia , Zhang Junhui , Dinh Hoang An , Forslund Sofia K. , Markó Lajos , Hellmig Nicole , Peters Jörg , Muller Dominik N. , Lifton Richard P. , Nottoli Timothy , Stölting Gabriel , Scholl Ute I.
Published: April 2021

Significance

Primary aldosteronism (increased production of the adrenal steroid hormone aldosterone) is the most common cause of secondary hypertension. We here generated a mouse model of familial hyperaldosteronism type IV with a heterozygous gain-of-function mutation in a calcium channel gene (Cacna1hM1560V/+).Cacna1hM1560V/+mice have about twofold elevated aldosterone:renin ratios (a screening parameter for primary aldosteronism) and elevated blood pressure, with an overall mild phenotype. Elevated adrenal aldosterone synthase expression inCacna1hM1560V/+mice is associated with increased intracellular calcium concentrations in glomerulosa cells. This model allows for the ex vivo analysis of calcium signaling in aldosterone-producing glomerulosa cells of the adrenal gland.Cacna1h−/−mice have normal aldosterone synthase expression, with implications for the evaluation of CACNA1H as a therapeutic target.
Local adaptation of
Mycobacterium tuberculosis
on the Tibetan Plateau
Authors: Liu Qingyun , Liu Haican , Shi Li , Gan Mingyu , Zhao Xiuqin , Lyu Liang-Dong , Takiff Howard E. , Wan Kanglin , Gao Qian
Published: April 2021

Significance

The global distribution of different
Mtb
lineages is very structured, with a few lineages that are globally widespread, whereas many others are restricted to particular geographic regions. Although local adaptation has been a favored model for explaining the sympatric relationship between the bacteria and host in these geographic regions, this has been difficult to study. Human migration has led to intermixing of ethnicities and has disturbed the bacterial population structure, thereby masking the putative genetic determinants that may have evolved from selection pressures in a given region. Here, by analyzing the genomes of hundreds of
Mtb
strains sampled from the relatively isolated population of Tibetan, we provide genetic evidence that
Mtb
can evolve to adapt to local populations and environments.