bluuebunny/crossref_metadata_2025 huggingface dataset:
S,N-Heteropentacenes – Syntheses of Electron-Rich Anellated Pentacycles
Authors: Berens Henning R. V. , Müller Thomas J. J.
Published: April 2021

This review summarizes syntheses of S,N-heteropentacenes, i.e. electron-rich sulfur and nitrogen-embedding pentacycles, and briefly highlights selected applications in molecular electronics. Depending on the anellation mode and the number of incorporated heteroatoms, electron density can be raised by increasing nitrogen incorporation and polarizability is manifested by the sulfur content. In comparison to triacene analogues, the conjugation pathways of S,N-heteropentacenes are increased and the favorable acene-typical crystallization behavior allows for diverse application in organic electronics. Furthermore, substitution patterns allow fine-tuning the electronic properties, extending the π-systems, and supplying structural elements for further application.

1 Introduction

2 Thiophene-Centered S,N-Heteropentacenes

2.1 Dipyrrolo-Fused Thiophenes

2.2 Diindolo-Fused Thiophenes

3 Pyrrole-Centered S,N-Heteropentacenes

3.1 Dithieno-Fused Pyrroles

3.2 Bis[1]benzothieno-Fused Pyrrole

4 Fused 1,4-Thiazines

4.1 Dinaphtho-Fused 1,4-Thiazines

4.2 Bis[1]benzothieno-Fused 1,4-Thiazines

5 Conclusions and Outlook
Dimeric Phenazinothiadiazole Acceptors in Bulk Heterojunction Solar Cells
Authors: Ahrens Lukas , Hofstetter Yvonne J. , Celik Baris , Butscher Julian F. , Rominger Frank , Freudenberg Jan , Vaynzof Yana , Bunz Uwe H. F.
Published: April 2021

Two covalently linked triisopropylsilyl-ethynylated phenazinothiadiazoles were prepared through condensation of a spirocyclic and a bicyclic tetraketone with a 5,6-diaminobenzothiadiazole. The spirobisindene- and the ethanoanthracene-based linkers render the electron acceptors amorphous in thin films. The optoelectronic properties of the non-conjugated dimers are indistinguishable from that of the crystalline monomer. Bulk heterojunction solar cells were prepared with power conversion efficiencies peaking at 1.6%. The choice of linker neither influenced optical and electrochemical properties nor device performance.
Boosting the Stability of Boron Peroxides through Subphthalocyanine Coordination
Authors: Labella Jorge , López-Serrano Elisa , Torres Tomás
Published: April 2021

The great potential of subphthalocyanines (SubPcs) to stabilize boron peroxides has been demonstrated. In particular, a subphthalocyanato boron (III) peroxide has been prepared in good yield via boron triflate. This derivative is remarkably stable under ambient conditions and can be fully characterized. The impact of the peroxide group on the structural and optoelectronic properties of SubPc was examined by NMR and UV/Vis spectroscopies, as well as single-crystal X-ray diffraction analysis. Moreover, density functional theory calculations were performed to explain the experimental results. The reactivity of this peculiar boron peroxide as an oxidant and a Lewis base was also studied.
Supramolecular Approaches for Taming the Chemo- and Regiochemistry of C60 Addition Reactions
Authors: Beil Sebastian B. , von Delius Max
Published: April 2021

The chemo- and regioselective functionalization of fullerenes is a long-standing problem of organic synthesis. Over the past five years, this fundamental challenge has gained technological relevance, because studies on single bis-adduct isomers in new-generation solar cells have demonstrated that the widespread use of isomer mixtures leads to suboptimal power conversion efficiencies. Herein, we review recent work on supramolecular approaches for achieving chemo- and regioselective syntheses of multiply functionalized derivatives of C60.
Simple, reversible gradient Seebeck coefficient measurement system for 300–600 K with COMSOL simulations
Authors: Biswas Soumya , Dutt Aditya S. , Sebastian Nirmal , Kamble Vinayak B.
Published: April 2021

Seebeck measurement is a crucial step for characterizing thermoelectric samples, as measuring the accurate value with a simpler system design is challenging. Here, we report a simple design of the Seebeck coefficient measurement system, which can measure the thermo-emf (Seebeck coefficient) of the sample, under a limited temperature range of 300–600 K. Unlike the majority of the reported instrumental designs, the system does not have a hot walled chamber. The sample is sandwiched between two brass block supported heaters, which are controlled separately. Thus, this type of system is suitable for a window of the temperature range near room temperature. In this paper, we report the system that can measure the Seebeck coefficient up to 600 K. The heaters touch the sample through 1 mm thick silver caps, which offer insignificant thermal resistance and a stable temperature, as seen through experiment as well as COMSOL simulations. A typical sample has, at maximum, a diameter of 10 mm and a thickness of 2–3 mm. A reversible temperature gradient is applied in quasi-static direct current mode. By virtue of its design, the sample holder ensures a minimum thermal and electrical contact resistance during a measurement cycle. The combination of metals used for measurement (Ag and Cu) shows negligible junction contribution. The variance up to ±2% and accuracy up to 8% at a high temperature have been obtained using calibration sample reference data of state-of-the-art commercial systems.
Environmental temperature effect on dimensional measurements of atomic force microscopy
Authors: Ma Chengfu , Chen Yuhang , Huang Wenhao
Published: April 2021

Atomic force microscopy (AFM) is increasingly being used as a fundamental tool for dimensional measurements at the nanoscale in the laboratory and in industry. Since the environmental temperature is not controlled in many measurements, or is even varied on purpose, quantification of its effects on AFM dimensional measurements is needed. In this paper, the influences of the temperature in the entire environment of the AFM (excluding only the controller and computer) and that in the local environment around the tip–sample are investigated. The results show that lateral dimensional measurements are affected mainly by the entire environmental temperature. However, vertical measurements are influenced by the temperature of both the entire environment and the local environment. The effects become significant for temperatures higher than some threshold, here between 35 and 40 °C.
The Cauchy problem for a generalized Riemann-type hydrodynamical equation
Authors: Wei Long , Wang Yang
Published: April 2021

In this work, we investigate the Cauchy problem for a generalized Riemann-type hydrodynamical equation. The local well-posedness of the equation in Besov spaces is derived by using Littlewood–Paley decomposition and transport equation theory. Then, we show that a finite maximal life span for a solution necessarily implies wave breaking for this solution and give a condition on the initial data to ensure wave breaking for this equation by making use of the method of characteristics; otherwise, the equation has a global smooth solution. In addition, we establish persistence results for solutions of the equation in weighted Lp spaces for a large class of moderate weights.
Application of response surface methodology to the temperature fluctuation suppression structure in the cryostats
Authors: Chen Hui , Liu Jieyu , Liu Yingwen
Published: April 2021

The cryocooler-based cryostat typically suffers from an intrinsic 200 mK temperature oscillation originating from the periodic variation of the cryocooler’s working fluid. In this paper, a numerical study is performed to investigate the impact of a thermal link (a temperature fluctuation suppression structure)’s geometric parameters on a cryostat’s performance. An optimization model is developed to minimize a cryostat flange’s temperature fluctuation and deviation. We considered three factors during the analysis: the number of the thermal link wires n, the length of the thermal link l, and the radius of the thermal link wires r. Two primary evaluation measures are the temperature fluctuation Tp–p and the temperature deviation of the flange Ri. The results are analyzed using Response Surface Methodology. The final predicted optimum combination of geometrical parameters for the thermal link is n = 8, l = 36 mm, and r = 0.8 mm. The optimization results are in good agreement with our model, and the deviations in predicted values are less than 1.6%. The model and results presented here to optimize the thermal link provide helpful guidance for cryostat optimization in experiments.
Dynamics in an attraction–repulsion Navier–Stokes system with signal-dependent motility and sensitivity
Authors: Zheng Pan , Willie Robert
Published: April 2021

This paper is concerned with an attraction–repulsion Navier–Stokes system with signal-dependent motility and sensitivity in a two-dimensional smooth bounded domain under zero Neumann boundary conditions for n, c, v and the homogeneous Dirichlet boundary condition for u. This system describes the evolution of cells that react on two different chemical signals in a liquid surrounding environment and models a density-suppressed motility in the process of stripe pattern formation through the self-trapping mechanism. The major difficulty in analysis comes from the possible degeneracy of diffusion as c and v tend to infinite. Based on a new weighted energy method, it is proved that under appropriate assumptions on parameter functions, this system possesses a unique global classical solution, which is uniformly-in-time bounded. Moreover, by means of energy functionals, it is shown that the global bounded solution of the system exponentially converges to the constant steady state.
Stochastic Schrödinger equation with Dirichlet noise boundary conditions
Authors: Juarez-Campos Beatriz
Published: April 2021

We consider the stochastic nonlinear Schrödinger equations on a half-line under Dirichlet brown-noise boundary conditions. We establish the global existence and uniqueness of solutions to the initial-boundary value problem with values in H1. We are also interested in the regularity behavior of solutions near the origin, where the boundary data are highly irregular.
Room-temperature plexcitonic strong coupling: Ultrafast dynamics for quantum applications
Authors: Xiong Xiao , Kongsuwan Nuttawut , Lai Yiming , Png Ching Eng , Wu Lin , Hess Ortwin
Published: April 2021

Strong light–matter interaction is at the heart of modern quantum technological applications and is the basis for a wide range of rich optical phenomena. Coupling a single quantum emitter strongly with electromagnetic fields provides an unprecedented control over its quantum states and enables high-fidelity quantum operations. However, single-emitter strong coupling is exceptionally fragile and has been realized mostly at cryogenic temperatures. Recent experiments have, however, demonstrated that single-emitter strong coupling can be realized at room temperature by using plasmonic nanocavities that confine optical fields via surface plasmons strongly on metal surfaces and facilitate sub-picosecond light–matter interaction. Here, we outline recent theoretical developments and experimental demonstrations of room-temperature strong coupling in the plasmonic platform, from emitter ensembles down to the single emitter limit, before placing a focus on selective studies that explore and provide insight into applications of plexcitonic strong coupling including sensing of single biological molecules, qubit entanglement generation, and reconfigurable single-photon sources and provide an outline of research directions in quantum sensing, quantum information processing, and ultrafast spectroscopy.
Monotonicity of solution to the dark monopole equations in non-Abelian gauge field theory
Authors: Zhang Xiangqin
Published: April 2021

In this paper, we combine a two-step iterative shooting argument and a fixed-point theorem approach to establish the existence of the solution of the dark monopole equations in a recently formulated non-Abelian gauge field theory by Deglmann and Kneipp and discuss its qualitative properties. In addition, the energy-minimizing solution of the dark monopole equations also satisfies the monotonicity, thus settling an unsettled but characteristic issue left out in an existence theorem regarding such a solution and confirming evidence from earlier numerical simulations.
Modeling and verification of life prediction of a V-shaped linear ultrasonic motor
Authors: Zhou Lifeng , Yao Zhiyuan , Dai Shichao , He Ying , Xu Hao
Published: April 2021

In this paper, a wear model is established for a V-shaped linear ultrasonic motor. The influence of the change in the dynamic friction coefficient and the roughness parameters of the contact surface of the stator/slider on the output performance of the motor is considered in this model. The wear mechanism of the motor and the variation rules of the morphology of the contact surface during the operation of the motor are studied, as well as the relation of the wear height of the driving tip with the preload force and the relation of the preload force with the resonance frequency of the stator. The accuracy of the model is verified by numerical simulation and experimental methods. A test platform for friction and wear experiments is constructed, and the wear characteristics and the output performance of the motor are tested. The obtained results indicated that the model can accurately predict the dynamic changes during the wear process and the service life and output performance of the motor.
Electron beam induced current microscopy of silicon p–n junctions in a scanning transmission electron microscope
Authors: Conlan Aidan P. , Moldovan Grigore , Bruas Lucas , Monroy Eva , Cooper David
Published: April 2021

A silicon p-n junction has been mapped using electron beam induced current in both a scanning transmission electron microscope (STEM) and a conventional scanning electron microscope (SEM). In STEM, the transmission of a higher energy electron beam through the thin specimen leads to better spatial resolution and a more uniform interaction volume than can be achieved in SEM. Better spatial resolution is also achieved in the thin TEM specimens as the diffusion lengths of the minority carriers are much lower than measured in bulk material due to the proximity of specimen surfaces. We further demonstrate that a positive fixed surface charge favors surface recombination of electrons in n-type silicon and induces a surface depletion region in p-type silicon. These results have been compared to off-axis electron holography measurements of the electrostatic potentials and simulations of the internal fields.
Development of the gas puffing imaging diagnostic on J-TEXT tokamak
Authors: Li F. , Yang Z. J. , Gao L. , Fu C. P.
Published: April 2021

Edge turbulence is important for plasma confinement, so the gas puffing imaging (GPI) diagnostic was proposed on the J-TEXT tokamak for the two-dimensional measurement of turbulence in the edge region. GPI is a diagnostic of plasma turbulence that uses a puff of neutral gas at the plasma edge to increase the local visible light emission for improved space–time resolution of plasma fluctuations. Considering the conditions of J-TEXT, the observation area is 21° away from the position of the optical system in the toroidal direction, and the observation area is 10 cm × 10 cm inside and outside the last closed flux surface. To have a lower divergence of the gas flow, the gas puff nozzle is specially designed. An interface has been developed for operation. To photograph the line radiation generated by the neutral gas cloud along the magnetic field lines, the optical system is designed. It is composed of a quartz glass, mirrors, commercial lenses, filters, and high-speed cameras. The high-speed camera can capture the line radiation with a speed up to 180 000 frames/s with 256 pixels × 256 pixels and an exposure time of 5 µs. In a recent experiment, the new GPI diagnostic has obtained some preliminary pictures.
Coherence measures induced by norm functions
Authors: Jing Yangping , Li Chi-Kwong , Poon Edward , Zhang Chengyang
Published: April 2021

Which matrix norms induce proper measures for quantifying quantum coherence? We study this problem for two important classes of norms and show that (i) coherence measures cannot be induced by any unitary similarity invariant norm and (ii) the ℓq,p-norm induces a coherence measure if and only if q = 1 and 1 ≤ p ≤ 2, thus giving a new class of coherence measures with simple closed forms that are easy to compute. These results extend and unify previously known facts about norm-induced coherence measures and lead to a broader framework for understanding what functionals can be coherence measures.
Sensing mechanism and optical properties of H2O on the surface of Pt/VO2: First-principles study
Authors: Huang Jingtao , Zhou Yi , Liu Yong , Lai Zhonghong , Zhou Fei , Zhu Jingchuan
Published: April 2021

Based on the density functional theory with generalized gradient approximation, the adsorption behavior and optical properties of H2O molecules on the surface of VO2 and Pt loaded on the VO2 surface were calculated. The calculation results show that the adsorption energy of H2O molecules on the surface of VO2 is −0.39 eV, the bond length and bond angle of H2O molecules have not changed significantly, and the adsorption of H2O molecules on VO2 is physisorption. Further research shows that the adsorption energy of H2O molecules on the surface of Pt/VO2 is −1.76 eV, and the bond angle of H2O molecules on the surface of Pt/VO2 has changed significantly, increasing by 4°. The results show that H2O molecules adsorption on the surface of Pt/VO2 is chemisorption. Subsequently, we calculated the optical properties of the entire system and found that its light absorption capacity in the visible light region is ranked as follows: VO2+Pt+H2O>VO2+Pt>VO2+H2O>VO2. Our results demonstrate that Pt loaded on the VO2 surface not only affects the adsorption behavior of VO2, but also significantly modifies the electronic structure by generating impurity-derived states. Our results provide a reference for further study of the optical properties of VO2 and the dissociation reaction of H2O molecules.
Modeling of contactless bubble–bubble interactions in microchannels with integrated inertial pumps
Authors: Hayes B. , Whiting G. L. , MacCurdy R.
Published: April 2021

In this study, the nonlinear effect of contactless bubble–bubble interactions in inertial micropumps is characterized via reduced parameter one-dimensional and three-dimensional computational fluid dynamics (3D CFD) modeling. A one-dimensional pump model is developed to account for contactless bubble-bubble interactions, and the accuracy of the developed one-dimensional model is assessed via the commercial volume of fluid CFD software, FLOW-3D. The FLOW-3D CFD model is validated against experimental bubble dynamics images as well as experimental pump data. Precollapse and postcollapse bubble and flow dynamics for two resistors in a channel have been successfully explained by the modified one-dimensional model. The net pumping effect design space is characterized as a function of resistor placement and firing time delay. The one-dimensional model accurately predicts cumulative flow for simultaneous resistor firing with inner-channel resistor placements (0.2L < x < 0.8L where L is the channel length) as well as delayed resistor firing with inner-channel resistor placements when the time delay is greater than the time required for the vapor bubble to fill the channel cross section. In general, one-dimensional model accuracy suffers at near-reservoir resistor placements and short time delays which we propose is a result of 3D bubble-reservoir interactions and transverse bubble growth interactions, respectively, that are not captured by the one-dimensional model. We find that the one-dimensional model accuracy improves for smaller channel heights. We envision the developed one-dimensional model as a first-order rapid design tool for inertial pump-based microfluidic systems operating in the contactless bubble–bubble interaction nonlinear regime.
Active flow control of the dynamic wake behind a square cylinder using combined jets at the front and rear stagnation points
Authors: Gao Donglai , Meng Hao , Huang Yewei , Chen Guanbin , Chen Wen-Li
Published: April 2021

This study experimentally investigated an active flow control method with combined jets at the front and the rear stagnation points of a square cylinder to suppress the unsteady wake flow. The Reynolds number (Re) was 1.67×104, based on the incoming speed of airflow and the diameter of test model. The square cylinder model was manufactured with two narrow slots symmetrically positioned at the centerline of the front and rear surfaces. The strength of the jets is characterized with a dimensionless momentum coefficient Cμ. We obtained the dynamic wake flow regimes by employing the particle image velocimetry technique. Then, with the method of proper orthogonal decomposition and linear stability analysis, the time-averaged flow characteristics, e.g., turbulence kinetic energy (TKE) and the Reynolds shear stress (RSS) distributions, and the dynamic wake flow behind the square cylinder were analyzed in detail. Results of flow visualization suggested that at low momentum coefficient Cμ the wake flow regime showed no notable modifications to the wake. As Cμ increased to 0.0948, the periodic shear layers from the square cylinder were found to be pushed to the farther wake. Meanwhile, the time-averaged wake flow region was found to be greatly modified in the streamwise direction with a notable decrease in TKE and RSS distributions. The experimental results indicated that unsteadiness of vortex shedding in the wake flow experienced notable suppression. For higher Cμ up to 0.2133 and 0.3793, unsteady vortex shedding from the square cylinder and the dynamic wake flow were further suppressed in the near wake. A linear stability analysis was also employed to reveal the underlying nature of wake modification by the combined jets.
Neutron radiation hardness of aluminum gallium nitride UV LEDs at various wavelengths
Authors: Sun K.-X. , Valencia H. , Soriano L. , Nelson R. O.
Published: April 2021

Radiation hard diagnostics are critical to the success of nuclear fusion at National Ignition Facility, Z, ITER, and prolonged space explorations. We have first demonstrated the exceptional proton radiation hardness of initial GaN devices and qualified their space flight and deployment for missions such as the Laser Interferometer Space Antenna and International Space Station. We have further conducted neutron radiation hardness experiments at Los Alamos Neutron Science Center by opening a new high fluence beam station. During 2014–2016, we irradiated multiple Aluminum Gallium Nitride (AlGaN) LEDs with a maximum fluence of 2.4 × 1013 neutrons/cm2 in 3 years and generated 54 161 current–voltage (I–V) scan traces. Our data processing program analyzes each and all I–V traces. In addition, we retrieved local temperature records to analyze and remove temperature effects in the outdoor environment. The I–V curve families of AlGaN UV LEDs with emitting wavelengths of 265, 275, and 310 nm were compared. The I–V curves of 265 nm AlGaN UV LEDs have the smallest deviations from the average value, while the I–V curves for 310 nm AlGaN LEDs showed the largest deviations from the average value. We have reached another important recommendation for the optimal use of multiple AlGaN optoelectronic devices or imaging arrays for inertially confined fusion diagnostics: Shorter wavelength devices at 265 nm exhibit more consistent radiation hardness performance than the 310 nm devices. Higher aluminum content LEDs or AlxGa1–xN devices with higher mole fraction x for generating shorter wavelengths have better radiation hardness for fusion diagnostics.
Non-contact and direct electrocaloric effect measurement for high-throughput material screening
Authors: Baba Masaaki , Kuwahara Ryoya , Ishibashi Naoya , Fukuda Shota , Takeda Masatoshi
Published: April 2021

A non-contact and direct electrocaloric effect (ECE) measurement system was developed for rapid ECE measurement. The ECE of ferroelectric materials was measured directly using two measurement methods, namely, the constant heating rate method (CH method) and one-dimensional temperature gradient method (1D method), with the measurement system. The CH method continuously measures the ECE while gently heating the sample, and it can evaluate the performance of the sample more quickly than conventional methods that measure the ECE at steady state. The 1D method directly measures the ECE using a 1D temperature distribution applied to the sample. This method can measure the temperature dependence of the ECE faster than the CH method. The measurement system achieved a high signal-to-noise ratio, and the temperature dependence of the ECE measured by the two methods was consistent. The proposed measurement system and methods enable promising candidate materials for electrocaloric cooling systems to be screened more rapidly than when using conventional approaches.
Regulating droplet impact on a solid hydrophobic surface through alternating current electrowetting-on-dielectric
Authors: Tan Jie , Wang Hongchen , Sun Mingyang , Tian Penghao , Wang Yutao , Wang Kun , Jiang Dongyue
Published: April 2021

The phenomenon of droplet impact is commonly found in industrial and agricultural processes. The basic characteristics and theories of a droplet impacting solid walls have been extensively studied, but the regulation of the droplet impact phenomenon has not been adequately examined. This study investigates the regulation of droplet impact on a hydrophobic surface based on alternating current electrowetting-on-dielectric (AC EWOD). When a water droplet impacts a virgin Teflon surface at 1.06 m/s, the phenomenon of partial rebound occurs. When an AC voltage is applied to an electrode pair underneath the Teflon layer, the droplet is stabilized on the hydrophobic surface after impact. To investigate the mechanism of influence of the AC signal on the regulation of droplet impact, the variation in the spread diameter and height of the droplet were characterized at different frequencies and amplitudes of the AC signal. An oscillation in the diameter of the droplet was observed in the retraction stage with the application of AC EWOD, which was the dominant effect in neutralizing the retraction kinetic energy and yielded the rebound inhibition effect. A transition diagram between partial droplet rebound and rebound inhibition was plotted in terms of voltage, frequency, and the Weber number, and theoretical analysis was carried out to determine the retraction kinetic energy dissipated by the viscous force when the AC EWOD signal was applied.
Symmetries, constants of the motion, and reduction of mechanical systems with external forces
Authors: de León Manuel , Lainz Manuel , López-Gordón Asier
Published: April 2021

This paper is devoted to the study of mechanical systems subjected to external forces in the framework of symplectic geometry. We obtain Noether’s theorem for Lagrangian systems with external forces, among other results regarding symmetries and conserved quantities. We particularize our results for the so-called Rayleigh dissipation, i.e., external forces that are derived from a dissipation function, and illustrate them with some examples. Moreover, we present a theory for the reduction in Lagrangian systems subjected to external forces, which are invariant under the action of a Lie group.
Influence of initial phase on subharmonic resonance in an incompressible boundary layer
Authors: Park Donghun , Park Jaeyoung , Kim Minwoo , Lim Jiseop , Kim Seungtae , Jee Solkeun
Published: April 2021

The influence of the initial phase of fundamental and subharmonic waves on subharmonic resonance is investigated for an incompressible boundary layer with zero and adverse pressure gradients. Parabolized stability equation analyses are carried out for various combinations of the initial phases of fundamental and subharmonic waves. The amplification of subharmonic and higher modes is found to depend strongly on the initial phases, and this dependence is consistent with observations from previous experimental studies. There exists a certain combination of initial phases that leads to resonance or anti-resonance condition (i.e., maximum or minimum growth, respectively). For all combinations of the initial phases, the phase dependence appears to be a function of a single parameter that represents the initial phase difference between the fundamental and subharmonic waves. The amplification in the subharmonic resonant interaction depends on the initial phase difference rather than the individual initial phase of the fundamental or subharmonic wave. In the downstream direction, the phase difference changes from the initial value and eventually converges to a specific value approximately ranging from 80° to 90°, regardless of the initial phase difference. This transient behavior does not start until the subharmonic wave enters the parametric resonant stage, which yields double-exponential growth. The qualitative characteristic of the phase dependence remains unchanged for the fundamental frequencies and spanwise wavenumbers as well as for the pressure gradients studied. The method of analysis and results contribute to the physical foundations of controlling boundary-layer transition dominated by the subharmonic resonance.
Stability on large non-constant steady states of semiconductor equations
Authors: Wu Yunshun , Wang Yong
Published: April 2021

Around the large non-constant steady state, we show the existence and uniqueness of the global solution of the three-dimensional Cauchy problem of the semiconductor equations without or with the magnetic field effect. Without the magnetic field effect, we prove that the solution converges to the non-constant steady state exponentially fast as time goes to infinity. With the magnetic field effect, the optimal algebraic time-decay rates of the lower-order derivatives of the solution are obtained. Our results manifest that the degenerate dissipation of the magnetic field slows down the decay rates of the whole solution.
Statistical properties of wave kinematics in long-crested irregular waves propagating over non-uniform bathymetry
Authors: Lawrence C. , Trulsen K. , Gramstad O.
Published: April 2021

Experimental and numerical evidence have shown that nonuniform bathymetry may alter significantly the statistical properties of surface elevation in irregular wave fields. The probability of “rogue” waves is increased near the edge of the upslope as long-crested irregular waves propagate into shallower water. The present paper studies the statistics of wave kinematics in long-crested irregular waves propagating over a shoal with a Monte Carlo approach. High order spectral method is employed as wave propagation model, and variational Boussinesq model is employed to calculate wave kinematics. The statistics of horizontal fluid velocity can be different from statistics in surface elevation as the waves propagate over uneven bathymetry. We notice strongly non-Gaussian statistics when the depth changes abruptly in sufficiently shallow water. We find an increase in kurtosis in the horizontal velocity around the downslope area. Furthermore, the effects of the bottom slope with different incoming waves are discussed in terms of kurtosis and skewness. Finally, we investigate the evolution of kurtosis and skewness of the horizontal velocity over a sloping bottom in a deeper regime. The vertical variation of these statistical quantities is also presented.
Pauli crystals make their experimental debut
Authors: Wilson R. Mark
Published: April 2021

When a few ultracold atoms are repeatedly trapped and imaged tens of thousands of times, self-organized patterns emerge out of the quantum blue.
A tabletop waveguide delivers coherent x rays
Authors: Berkowitz Rachel
Published: April 2021

The layered anode emits bright, directed beams without the need for mirrors or large-scale accelerators.
Nanoanalytical analysis of bisphosphonate-driven alterations of microcalcifications using a 3D hydrogel system and in vivo mouse model
Authors: Ruiz Jessica L. , Hutcheson Joshua D. , Cardoso Luis , Bakhshian Nik Amirala , Condado de Abreu Alexandra , Pham Tan , Buffolo Fabrizio , Busatto Sara , Federici Stefania , Ridolfi Andrea , Aikawa Masanori , Bertazzo Sergio , Bergese Paolo , Weinbaum Sheldon , Aikawa Elena
Published: April 2021

Significance

The most common cause of heart attacks or strokes is the rupture of thin fibrous caps that cover vulnerable plaques within blood vessels. Small mineral deposits, called microcalcifications, increase local tissue stress and thereby increase the risk of cap rupture. We report here the use of a three-dimensional collagen hydrogel model of fibrous cap calcification and a complementary mouse model of plaque formation to determine whether bisphosphonate (BiP) therapy, commonly used to treat bone loss, alters microcalcification formation. The results showed that BiP treatment resulted in time-dependent changes in microcalcification size and mineral morphology, dependent on whether BiP treatment was initiated before or after the expected onset of microcalcification formation.
Network dynamics of hypothalamic feeding neurons
Authors: Sweeney Patrick , Chen Can , Rajapakse Indika , Cone Roger D.
Published: April 2021

Significance

Paraventricular nucleus (PVN) neurons expressing the melanocortin 4 receptor (MC4R) integrate hormonal and neuronal information concerning energy availability and engage neural circuitry controlling feeding, metabolism, and neuroendocrine function in response to changes in body weight and stored energy. Thereby, the dynamic activity of PVN MC4R neurons may serve as a neural representation of body weight “set point.” Here, we demonstrate that PVN MC4R neuronal activity is bidirectionally regulated by changes in energy state, as neuronal activity is gradually suppressed during fasting and increased in response to refeeding. Together, these findings provide a framework for understanding how hunger and satiety are controlled within critical neurons involved in energy homeostasis.
A Raf-like kinase is required for smoke-induced seed dormancy in
Arabidopsis thaliana
Authors: Lee Inhye , Kim Eunsun , Choi Soobin , Kim Dayoung , Hong Wangyu , Choi Jungki , Choi Hyunmo , Kim Jimin , Sable Ganesh A. , Markkandan Kesavan , Lim Dongyeol , Park Soon Ki , Kim Soo Young , Lee Sumin , Soh Moon-Soo
Published: April 2021

Significance

Seed dormancy is an important developmental trait for plants, which ensures seed germination under more favorable spatiotemporal environments. A smoke compound, 3,4,5-trimethylfuran-2(
5H
)-one, which is called TMB for short, has been identified to inhibit seed germination in a still elusive way. Here, we presented several lines of evidence that TMB inhibits seed germination through the induction of physiological dormancy. Furthermore, by isolating TMB-resistant
Arabidopsis
mutants, we demonstrated that
TMB RESISTANT1
, encoding a Raf-like kinase, is critically required for the TMB-induced seed dormancy. These results suggest the presence of a smoke sensory pathway that takes part in the multiple layers of the dormancy regulatory network in higher plants.
Deep generative selection models of T and B cell receptor repertoires with soNNia
Authors: Isacchini Giulio , Walczak Aleksandra M. , Mora Thierry , Nourmohammad Armita
Published: April 2021

Significance

The adaptive immune system relies on many types of B and T cells, whose functions are reflected in the distinct molecular features of their receptor sequences. Here, we introduce an inference framework, soNNia, which integrates interpretable knowledge-based models of immune receptor generation with flexible and powerful deep learning approaches to characterize sequence determinants of receptor function. Using soNNia, we characterize sequence-specific selection associated with receptors harvested from different cell types and tissues. We quantify synergetic interactions between the molecular features of the paired chains making up the receptor. Lastly, we develop a selection-based classifier to identify T cells specific to distinct pathogenic epitopes. Our approach provides a molecular understanding for how sequence determines the specific functionality of immune receptors.
Fast inactivation of Nav1.3 channels by FGF14 proteins: An unconventional way to regulate the slow firing of adrenal chromaffin cells
Authors: Carbone Emilio
Published: April 2021

Using Nav1.3 and FGF14 KO mice, Martinez-Espinosa et al. provide new findings on how intracellular FGF14 proteins interfere with the endogenous fast inactivation gating and regulate the “long-term inactivation” of Nav1.3 channels that sets Nav channel availability and spike adaptation during sustained stimulation in adrenal chromaffin cells.
Charge trap spectroscopy in polymer dielectrics: a critical review
Authors: Teyssedre Gilbert , Zheng Feihu , Boudou Laurent , Laurent Christian
Published: April 2021

Trapping phenomena are essential features controlling the transport properties of insulating materials. Depending on the energy depth, traps can either assist transport or lead to long-lasting storage of charges. The consequences of charge trapping are non-linear phenomena and electric field distribution distortion in the dielectric bulk. The important characteristics about traps are the nature of the levels, their depth in energy, and their density. In this review, we discuss the different techniques available to probe the energetics of traps, particularly in insulating polymers. The methods implemented for approaching the characteristics of traps range from atomistic simulation based on known physical/chemical defects, identification by spectroscopic techniques, and coupled optical-electrical or thermal-electrical techniques. The review is focused on methods involving thermal or optical excitation coupled to detection using electrical or luminescence response with questioning about the physical hypotheses behind the analysis and the difference in response obtained through the various approaches. The technical implementation of these methods is described, along with examples of application. The differences in trap depth estimation from optical and thermal methods is discussed as well as the impact of having distributed trap depths. The input of luminescence techniques, which provide a fingerprint of chemical groups involved in charge recombination, is put forward.
Investigation of transient mass transport induced deformation of PEGDA hydrogel in photocurable solution
Authors: Liu Wangyu , Zhou Feng , Sun Dong , Luo Yuanqiang , Tang Aimin
Published: April 2021

Hydrogels have attractive characteristics such as notable biocompatibility, outstanding hydrophilia and efficient mass transport (MT), which makes hydrogel suitable for tissue engineering scaffold materials. Stereolithography is a prevalent method to prepare hydrogel scaffold with complex structure. However, it is difficult to ensure dimension accuracy in printing complex hydrogel scaffold since solvents can migrate in gel and render MT behavior, which consequently induce deformation and dimensional inaccuracy of printed hydrogel. Little investigation of MT of gel in mixture like solution is conducted. Aiming to depict multiple solvents MT in gel, a model is established by mainly modifying the representation of free energy of mixing to the multi-component one. This model is feasible to describe concurrent multiple solvents migration and mechanical deformation for hydrogel in liquid mixtures, which fulfills understanding of multi-component MT. In this work, the transient MT behaviors of poly(ethylene glycol) diacrylate gel in its photocurable solution are investigated by the model. The numerical model is validated by experimental results and then applied to simulate free and confined MT process of the system. It is found that the deformation trend is not monotonous and total gel deformation can be regulated by adjusting printing time. The correspondence between numerical and experimental results proved that this model can promisingly illustrate multi-component MT induced deformation and provide instructions on improving dimensional accuracy for printing hydrogels.
Antimony doped SnO2 nanowire@C core–shell structure as a high-performance anode material for lithium-ion battery
Authors: Mousavi MirRazi , Abolhassani Reza , Hosseini Mohammad , Akbarnejad Elaheh , Mojallal Mohammad Hossein , Ghasemi Shahnaz , Mohajerzadeh Shams , Sanaee Zeinab
Published: April 2021

SnO2 is considered as one of the high specific capacity anode materials for Lithium-ion batteries. However, the low electrical conductivity of SnO2 limits its applications. This manuscript reports a simple and efficient approach for the synthesis of Sb-doped SnO2 nanowires (NWs) core and carbon shell structure which effectively enhances the electrical conductivity and electrochemical performance of SnO2 nanostructures. Sb doping was performed during the vapor-liquid-solid synthesis of SnO2 NWs in a horizontal furnace. Subsequently, carbon nanolayer was coated on the NWs using the DC Plasma Enhanced Chemical Vapor Deposition approach. The carbon-coated shell improves the Solid-Electrolyte Interphase stability and alleviates the volume expansion of the anode electrode during charging and discharging. The Sb-doped SnO2 core carbon shell anode showed the superior specific capacity of 585 mAhg−1 after 100 cycles at the current density of 100 mA g−1, compared to the pure SnO2 NWs electrode. The cycle stability evaluation revealed that the discharge capacity of pure SnO2 NWs and Sb doped SnO2 NWs electrodes were dropped to 52 and 152 mAh g−1 after100th cycles. The process of Sb doping and carbon nano shielding of SnO2 nanostructures is proposed for noticeable improvement of the anode performance for SnO2 based materials.
Facile multifunctional-mode of fabricated biocompatible human serum albumin/reduced graphene oxide/Cladophora glomerata nanoparticles for bacteriostatic phototherapy, bacterial tracking and antioxidant potential
Authors: Amina Musarat , Al Musayeib Nawal M , Alarfaj Nawal A , El-Tohamy Maha F , Al-Hamoud Gadah A
Published: April 2021

To overcome multi-drug resistance in microbes, highly efficient antimicrobial substances are required that have a controllable antibacterial effect and are biocompatible. In the present study, an efficient phototherapeutic antibacterial agent, human serum albumin (HSA)/reduced graphene oxide (rGO)/Cladophora glomerata bionanocomposite was synthesized by the incorporation of rGO nanoparticles with HSA, forming protein-rGO, and decorated with a natural freshwater seaweed Cladophora glomerata. The prepared HSA/rGO/Cladophora glomerata bionanocomposite was characterized by spectroscopic (UV-vis, FTIR, XRD and Raman) and microscopic (TEM and SEM) techniques. The as-synthesized bionanocomposite showed that sunlight/NIR irradiation stimulated ROS-generating dual-phototherapic effects against antibiotic-resistant bacteria. The bionanocomposite exerted strong antibacterial effects (above 96 %) against amoxicillin-resistant P. aeruginosa and S. aureus, in contrast to single-model-phototherapy. The bionanocomposite not only generated abundant ROS for killing bacteria, but also expressed a fluorescence image for bacterial tracking under sunlight/NIR irradiation. Additionally, the bionanocomposite displayed pronounced antioxidant activity.
VizGrain: a new computational tool for particle simulations of reactive plasma discharges and rarefied flow physics
Authors: Levko Dmitry , Upadhyay Rochan R , Karpatne Anand , Breden Douglas , Suzuki Kenta , Topalian Victor , Shukla Chandrasekhar , Raja Laxminarayan L
Published: April 2021

This paper presents recent progress on the development of the new multi-purpose particle modeling and simulation tool VizGrain. A unique aspect of VizGrain is that it allows computational modeling of particle dynamics in a variety of systems, including rarefied gas dynamics, macroscopic particle dynamics (e.g., dust particles, droplets, etc), particle-in-cell modeling, and hybrid continuum-particle modeling within a single integrated framework. VizGrain allows working with atomic sized particles and particles with finite macroscopic sizes. The former approach is used to model rarefied gas dynamics and conventional non-equilibrium plasmas, while the finite sized macro-particles are considered for the modeling of dusty plasmas, aerosols, droplets etc. In this latter case, the electrical charge up of particles in a plasma environment is considered. The model features a comprehensive variety of drag forces that can act on both atomic and macro-particles. A detailed description of the physical models implemented within VizGrain is presented, to provide insights into the approach that can be taken in other particle-based codes in the community. These models are scrupulously validated against the benchmark problems proposed in the research literature for a variety of applications from the plasma reactors used in semiconductor industry to high-speed rarefied gas dynamics problems.
Community lockdowns in social networks hardly mitigate epidemic spreading
Authors: Gosak Marko , Duh Maja , Markovič Rene , Perc MatjaŽ
Published: April 2021

Community lockdowns and travel restrictions are commonly employed to decelerate epidemic spreading. We here use a stochastic susceptible-infectious-recovered model on different social networks to determine when and to what degree such lockdowns are likely to be effective. Our research shows that community lockdowns are effective only if the links outside of the communities are virtually completely sealed off. The benefits of targeting specifically these links, as opposed to links uniformly at random across the whole network, are inferable only beyond 90% lockdown effectiveness. And even then the peak of the infected curve decreases by only 20% and its onset is delayed by a factor of 1.5. This holds for static and temporal social networks, regardless of their size and structural particularities. Networks derived from cell phone location data and online location-based social platforms yield the same results as a large family of hyperbolic geometric network models where characteristic path lengths, clustering, and community structure can be arbitrarily adjusted. The complex connectedness of modern human societies, which enables the ease of global communication and the lightning speeds at which news and information spread, thus makes it very difficult to halt epidemic spreading with top-down measures. We therefore emphasize the outstanding importance of endogenous self-isolation and social distancing for successfully arresting epidemic spreading.