bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemistry education research and practice in diverse online learning environments: resilience, complexity and opportunity!
Authors: Lawrie Gwendolyn
Published: January 2021

It would be difficult to step into 2021 without acknowledging the shifting sands, and sometimes sinkholes, that we have experienced as chemistry educators during 2020. COVID-19 could be construed to have been a perfect storm in chemistry education research and practice. Or perhaps it represents a threshold that has been crossed involving the creation of teaching dissonance.
The nickel-sirohydrochlorin formation mechanism of the ancestral class II chelatase CfbA in coenzyme F430 biosynthesis
Authors: Fujishiro Takashi , Ogawa Shoko
Published: January 2021

The substrate-assisted nickel chelatase mechanism of CfbA in coenzyme F430 biosynthesis was unveiled by X-ray crystal structure analysis.
Rh(i)- and Rh(ii)-catalyzed C–H alkylation of benzylamines with alkenes and its application in flow chemistry
Authors: Das Amrita , Chatani Naoto
Published: January 2021

Rh(i)- and Rh(ii)-catalyzed C–H alkylation of benzylamines with alkenes using a picolinamide derivative as a directing group is reported under both batch and flow.
Snapshotting the transient conformations and tracing the multiple pathways of single peptide folding using a solid-state nanopore
Authors: Liu Shao-Chuang , Ying Yi-Lun , Li Wei-Hua , Wan Yong-Jing , Long Yi-Tao
Published: January 2021

A solid-state nanopore based method is described for resolving protein-folding-related problems via snapshotting the folding intermediates and characterizing the kinetics of a single peptide.
Investigating states of gas in water encapsulated between graphene layers
Authors: Hsu Wei-Hao , Hwang Ing-Shouh
Published: January 2021

Transmission electron microscopy of gas-supersaturated water in graphene liquid cells shows two microscopic structures: polycrystalline nano-particles and a clathrate structure. The observations challenge conventional view of gas in water.
Modulation of the superficial electronic structure via metal–support interaction for H2 evolution over Pd catalysts
Authors: Wang Jin , Cheng Dan , Gao Mengmeng , Li Qian , Xin Ying , Zhang Nana , Zhang Zhaoliang , Yu Xuehua , Zhao Zhen , Zhou Kebin
Published: January 2021

A new type of electronic effect, polarized metal-support interaction (pEMSI), in oxide-supported Pd nanoparticles describing the enhanced accumulation of electrons at the superficial surface is responsible for improved catalytic H2 evolution.
Supercritical water co-liquefaction of LLDPE and PP into oil: properties and synergy
Authors: Zhao Peitao , Yuan Zhilong , Zhang Jing , Song Xueping , Wang Cuiping , Guo Qingjie , Ragauskas Arthur J.
Published: January 2021

The supercritical water liquefaction of PE/PP mixtures yields around 86.84–90.70% oil without catalyst or H2.
Isolating metallophthalocyanine sites into graphene-supported microporous polyaniline enables highly efficient sensing of ammonia
Authors: Lu Xiaodong , Chen Zhimin , Wu Hao , Cao Erping , Wang Ying , Du Shichao , Wu Yiqun , Ren Zhiyu
Published: January 2021

The successful isolation of metal phthalocyanines into graphene-supported microporous polyanilines results in rich exposure to active sites, rapid electron transfer and efficient gas transport channels, which synergically enhance NH3 sensing.
Hydronium ion diffusion in model proton exchange membranes at low hydration: insights from ab initio molecular dynamics
Authors: Zelovich Tamar , Winey Karen I. , Tuckerman Mark E.
Published: January 2021

Sequence of steps in the reaction of hydronium (H3O+) with sulfonate (SO3−) contributing to the proton structural diffusion mechanism in a low-hydration environment of a proton-exchange-membrane (PEM) mimic.
Dynamics of delivering aptamer targeted nano-drugs into cells
Authors: Liu Yulin , Yang Yu , Zhang Qingrong , Lu Denghua , Li Siying , Li Junfeng , Yang Guocheng , Shan Yuping
Published: January 2021

Gaining precise dynamics over the cellular entry of targeted nano-drug may be the most pertinent question in achieving high efficiency nano-drug. Based on force tracing technique, the dynamics of delivering targeted nano-drug into cell was explored.
Cell-free scaffolds functionalized with bionic cartilage acellular matrix microspheres to enhance the microfracture treatment of articular cartilage defects
Authors: Liu Jun , Lu Yan , Xing Fei , Liang Jie , Wang Qiguang , Fan Yujiang , Zhang Xingdong
Published: January 2021

The cell-free scaffold functionalized with bionic cartilage acellular matrix microspheres (BCAMMs) improves the outcome of microfracture treatment to articular cartilage defects in a rabbit model.
Multiscale simulation of extreme ultraviolet nanolithography: impact of acid–base reaction on pattern roughness
Authors: Lee Hyungwoo , Park Sungwoo , Kim Muyoung , Moon Junghwan , Lee Byunghoon , Cho Maenghyo
Published: January 2021

Impact of acid–base neutralization in EUV lithography was investigated using our newly developed multi-scale framework (DFT-MD-FDM).
Enantiomeric perovskite with a dual phase transition at high temperature
Authors: Peng Hang , Cheng Hao , Liu Yu-Hua , Yang Meng-Juan , Liao Wei-Qiang , Ai Yong
Published: January 2021

Chiral organic–inorganic perovskites show a dual-phase-transition with Tc as high as 367 K and 460 K and robust dielectric switching properties.
Complexin-2 redistributes to the membrane of muscle cells in response to insulin and contributes to GLUT4 translocation
Authors: Pavarotti Martin Alejandro , Tokarz Victoria , Frendo-Cumbo Scott , Bilan Philip J. , Liu Zhi , Zanni-Ruiz Emilia , Mayorga Luis Segundo , Klip Amira
Published: January 2021

Insulin stimulates glucose uptake in muscle cells by rapidly redistributing vesicles containing GLUT4 glucose transporters from intracellular compartments to the plasma membrane (PM). GLUT4 vesicle fusion requires the formation of SNARE complexes between vesicular VAMP and PM syntaxin4 and SNAP23. SNARE accessory proteins usually regulate vesicle fusion processes. Complexins aide in neuro-secretory vesicle-membrane fusion by stabilizing trans-SNARE complexes but their participation in GLUT4 vesicle fusion is unknown. We report that complexin-2 is expressed and homogeneously distributed in L6 rat skeletal muscle cells. Upon insulin stimulation, a cohort of complexin-2 redistributes to the PM. Complexin-2 knockdown markedly inhibited GLUT4 translocation without affecting proximal insulin signalling of Akt/PKB phosphorylation and actin fiber remodelling. Similarly, complexin-2 overexpression decreased maximal GLUT4 translocation suggesting that the concentration of complexin-2 is finely tuned to vesicle fusion. These findings reveal an insulin-dependent regulation of GLUT4 insertion into the PM involving complexin-2.
A non‐singular fast terminal sliding mode control scheme for residual current compensation inverters in compensated distribution networks to mitigate powerline bushfires
Authors: Roy Tushar Kanti , Mahmud Md Apel , Nasiruzzaman A. B. M. , Barik Md Abdul , Oo Amanullah Maung Than
Published: January 2021

This paper presents an approach to design a non‐singular fast terminal sliding model controller for residual current compensation inverters in compensated distribution networks to compensate the fault current due to most commonly occurred single line‐to‐ground faults. The main control objective is to completely eliminate the fault current in order to mitigate the impacts of powerline bushfires. A non‐singular fast terminal sliding surface is used to design the controller so that the residual current compensation inverter can quickly ensure the desired control performance without experiencing singularity problems. In this scheme, the chattering effects are minimised by replacing the discontinuous function appearing in the control law with a continuous function and the Lyapunov stability theory is utilised to demonstrate the theoretical stability of the control law. This paper also includes an overview of the non‐singular terminal sliding model controller as the performance of the non‐singular fast terminal sliding model controller is compared with this controller through rigorous simulation results over a range of fault currents. Simulation results clearly demonstrate the faster convergence speed of the non‐singular fast terminal sliding model controller over the non‐singular terminal sliding model controller for compensating the fault current and hence, mitigating powerline bushfires.
Upping the internal quantum efficiency of green light‐emitting diodes by employing a graded AlGaN barrier and an electron blocking layer
Authors: Usman Muhammad , Anwar Abdur‐Rehman , Munsif Munaza , Ullah Ihsan
Published: January 2021

Two different device structures are numerically studied, and their optoelectronic characteristics with standard structure are compared. The authors minimized the uneven carrier distribution across the active region. By replacing the first quantum barrier with graded AlGaN and using a graded AlGaN electron blocking layer, in the structure proposed by the authors, the injection of holes into the active region is improved. By using the graded AlGaN barrier, the concentration of injected electrons is also controlled because of the additional barrier height. As a result, the contribution of radiative recombination is boosted. The droop ratio of the proposed structure is reduced to ∼34% at 100 A cm−2 in comparison to other devices.
Parker Solar Probe observations of He/H abundance variations in SEP events inside 0.5 au
Authors: Cohen C. M. S. , Christian E. R. , Cummings A. C. , Davis A. J. , Desai M. I. , de Nolfo G. A. , Giacalone J. , Hill M. E. , Joyce C. J. , Labrador A. W. , Leske R. A. , Matthaeus W. H. , McComas D. J. , McNutt R. L. , Mewaldt R. A. , Mitchell D. G. , Mitchell J. G. , Rankin J. S. , Roelof E. C. , Schwadron N. A. , Stone E. C. , Szalay J. R. , Wiedenbeck M. E. , Vourlidas A. , Bale S. D. , Pulupa M. , MacDowall R. J.
Published: January 2021

Aims. The Parker Solar Probe (PSP) orbit provides an opportunity to study the inner heliosphere at distances closer to the Sun than previously possible. Due to the solar minimum conditions, the initial orbits of PSP yielded only a few solar energetic particle (SEP) events for study. Recently during the fifth orbit, at distances from 0.45 to 0.3 au, the energetic particle suite on PSP, Integrated Science Investigation of the Sun (IS⊙IS), observed a series of six SEP events, adding to the limited number of SEP events studied inside of 0.5 au. Variations in the H and He spectra and the He/H abundance ratio are examined and discussed in relation to the identified solar source regions and activity.

Methods. IS⊙IS measures the energetic particle environment from ~20 keV to >100 MeV/nuc. Six events were selected using the ~1 MeV proton intensities, and while small, they were sufficient to calculate proton and helium spectra from ~1 to ~10 MeV/nuc. For the three larger events, the He/H ratio as a function of energy was determined. Using the timing of the associated radio bursts, solar sources were identified for each event and the eruptions were examined in extreme ultraviolet emission.

Results. The largest of the selected events has peak ~1 MeV proton intensities of 3.75 (cm2 sr s MeV)−1. Within uncertainties, the He and H spectra have similar power law forms with indices ranging from −2.3 to −3.3. For the three largest events, the He/H ratios are found to be relatively energy independent; however, the ratios differ substantially with values of 0.0033 ± 0.0013, 0.177 ± 0.047, and 0.016 ± 0.009. An additional compositional variation is evident in both the 3He and electron signatures. These variations are particularly interesting as the three larger events are likely a result of similar eruptions from the same active region.
Planck constraints on the tensor-to-scalar ratio
Authors: Tristram M. , Banday A. J. , Górski K. M. , Keskitalo R. , Lawrence C. R. , Andersen K. J. , Barreiro R. B. , Borrill J. , Eriksen H. K. , Fernandez-Cobos R. , Kisner T. S. , Martínez-González E. , Partridge B. , Scott D. , Svalheim T. L. , Thommesen H. , Wehus I. K.
Published: January 2021

We present constraints on the tensor-to-scalar ratio r using Planck data. We use the latest release of Planck maps, processed with the NPIPE code, which produces calibrated frequency maps in temperature and polarisation for all Planck channels from 30 GHz to 857 GHz using the same pipeline. We computed constraints on r using the BB angular power spectrum, and we also discuss constraints coming from the TT spectrum. Given Planck’s noise level, the TT spectrum gives constraints on r that are cosmic-variance limited (with σr = 0.093), but we show that the marginalised posterior peaks towards negative values of r at about the 1.2σ level. We derived Planck constraints using the BB power spectrum at both large angular scales (the ‘reionisation bump’) and intermediate angular scales (the ‘recombination bump’) from ℓ = 2 to 150 and find a stronger constraint than that from TT, with σr = 0.069. The Planck BB spectrum shows no systematic bias and is compatible with zero, given both the statistical noise and the systematic uncertainties. The likelihood analysis using B modes yields the constraint r < 0.158 at 95% confidence using more than 50% of the sky. This upper limit tightens to r < 0.069 when Planck EE, BB, and EB power spectra are combined consistently, and it tightens further to r < 0.056 when the Planck TT power spectrum is included in the combination. Finally, combining Planck with BICEP2/Keck 2015 data yields an upper limit of r < 0.044.
Giant planet migration during the disc dispersal phase
Authors: Monsch Kristina , Picogna Giovanni , Ercolano Barbara , Kley Wilhelm
Published: January 2021

Context. Transition discs are expected to be a natural outcome of the interplay between photoevaporation and giant planet formation. Massive planets reduce the inflow of material from the outer to the inner disc, therefore triggering an earlier onset of disc dispersal due to photoevaporation through a process known as Planet-Induced PhotoEvaporation. In this case, a cavity is formed as material inside the planetary orbit is removed by photoevaporation, leaving only the outer disc to drive the migration of the giant planet.

Aims. We investigate the impact of photoevaporation on giant planet migration and focus specifically on the case of transition discs with an evacuated cavity inside the planet location. This is important for determining under what circumstances photoevaporation is efficient at halting the migration of giant planets, thus affecting the final orbital distribution of a population of planets.

Methods. For this purpose, we use 2D FARGO simulations to model the migration of giant planets in a range of primordial and transition discs subject to photoevaporation. The results are then compared to the standard prescriptions used to calculate the migration tracks of planets in 1D planet population synthesis models.

Results. The FARGO simulations show that once the disc inside the planet location is depleted of gas, planet migration ceases. This contradicts the results obtained by the impulse approximation, which predicts the accelerated inward migration of planets in discs that have been cleared inside the planetary orbit.

Conclusions. These results suggest that the impulse approximation may not be suitable for planets embedded in transition discs. A better approximation that could be used in 1D models would involve halting planet migration once the material inside the planetary orbit is depleted of gas and the surface density at the 3:2 mean motion resonance location in the outer disc reaches a threshold value of 0.01 g cm‒2.
Ballot position effects in open-list PR systems: the moderating impact of postal voting
Authors: Jankowski Michael , Frank Torren
Published: January 2021

Various studies demonstrate that candidates at the top of the party list have a strong advantage in preferential voting systems, particularly under open-list PR. Such ballot position effects can be explained by voters’ tendency to rely on easily available information shortcuts when selecting a candidate. In this paper, we argue that the strength of ballot position effects depends on the context of how voters cast their vote. Specifically, we argue that postal voters are less likely to rely on the ballot position cue compared to voters who vote on election day for two reasons. First, postal voters might be more politically interested. Second, postal voters have more time to assess additional information about the candidates. The hypothesis is tested by analyzing newly collected data from two open-list PR elections in the German federal state of Hamburg. The results confirm the theoretical expectations: Ballot position effects are substantively weaker among postal voters. Additional analyses suggest that differences in the political interest between postal voters and election day voters are unlikely to fully explain these results. These findings advance our understanding of ballot position effects and voters’ use of information shortcuts more generally.
Generic zero-Hausdorff and one-packing spectral measures
Authors: Carvalho Silas L. , de Oliveira César R.
Published: January 2021

For some metric spaces of self-adjoint operators, it is shown that the set of operators whose spectral measures have simultaneous zero upper-Hausdorff and one lower-packing dimension contains a dense Gδ subset. Applications include sets of limit-periodic operators.
Using solenoid as multipurpose tool for measuring beam parameters
Authors: Pinayev Igor , Jing Yichao , Kayran Dmitry , Litvinenko Vladimir N. , Ma Jun , Mihara Kentaro , Petrushina Irina , Shih Kai , Wang Gang , Wu Yuan Hui
Published: January 2021

Solenoids are frequently used for focusing low-energy beams. In this paper, we show how they can serve as multipurpose diagnostics tools to measure various beam parameters, including energy, emittance, the second moments of the transverse distribution, and the beam position and angle with respect to the solenoid’s axis. The energy measurement is based on rotation of the plane of the transverse motion, as opposed to generating dispersion with a dipole. Measurement of the beam trajectory with respect to the solenoid axis is done by analyzing the beam orbit downstream of the solenoid while varying its current. The second moments are calculated by analyzing the beam image on a profile monitor while accounting for the beam rotation caused by the solenoid. We describe in detail the corresponding procedures and the experimental results of these measurements.
Dynamics of the price–volume information flow based on surrogate time series
Authors: Nie Chun-Xiao
Published: January 2021

This paper uses transfer entropy and surrogates to analyze the information flow between price and transaction volume. We use random surrogates to construct local random permutation (LRP) surrogates that can analyze the local information flow in detail. The analysis based on the toy models verifies the effectiveness of the LRP method. We further apply it to analyze three financial datasets, including two index datasets and one stock dataset. Empirical analysis shows that both the S&P500 index data and SSEC index data include rich information flow dynamics. There was a stronger information flow during the stock bubble burst or the financial crisis. In addition, tests based on stock data suggest that market crises may lead to changes in the relationship between prices and trading volume. This paper provides a new way to analyze the price–volume relationship, which can effectively detect the drastic changes in the local information flow, thereby providing a method for studying the impact of events.
Line-defect orientation- and length-dependent strength and toughness in hBN
Authors: Hao Tengyuan , Zhang Zhaocheng , Ahmed Tousif , Xu Justin , Brown Shane , Hossain Zubaer M.
Published: January 2021

Applying classical molecular dynamics simulations, we report the effects of length (λ) and orientation (θ) of a line-defect on strength and toughness in defective 2D hexagonal boron nitride. Results reveal the existence of a “transition angle,” θt=2.47°, at which both toughness and strength are insensitive to the finite length of the defect in an infinite domain. For θ<θt, both toughness and strength increase with an increase in defect-length; whereas, for θ>θt, they show the opposite behavior. Examination of the stress-fields shows that θ-dependent variation in stress-localization at the edges of the line-defect and symmetry-breaking of the stress-fields with respect to the defect-axis govern the disparate θ-dependent behavior. For θ<θt, the intensity of elastic fields at the edges of the line-defect is substantially weakened by the elastic interactions originating from the atoms on the sides of the line-defect. For θ>θt, the stress-intensity at the edges is strongly localized at the opposite sides of the line-defect. The stress-intensity increases asymptotically with the increasing defect-length and reduces the strength and toughness of the defective lattice. The stress-localization, however, saturates at a “saturation angle” of around 60° for strength and 30° for toughness. Additionally, there exists a critical defect-length λc=60 Å, below which there is a strong θ-dependent variation in elastic interactions between the edges, affecting strength and toughness substantially. For λ>λc, the elastic interactions saturate and make both strength and toughness insensitive to the change in the length of the defect.
Dye-sensitized H2 evolution from water facilitated by photoinduced electron transfer between molecules on the inside and the outside of a carbon nanotube
Authors: Tajima Tomoyuki , Yamagami Masahiro , Sagawa Ryohei , Miyake Hideaki , Takaguchi Yutaka
Published: January 2021

Dye-encapsulated single-walled carbon nanotubes (dye@SWCNTs) were physically modified to fabricate a water-dispersible dye@SWCNT/dendrimer hybrid. A photocatalytic H2 evolution reaction that uses this dye@SWCNT hybrid as a particulate photocatalyst was conducted in the presence of an electron-relay molecule [methyl viologen (MV2+)], a co-catalyst [PVP–Pt; poly(vinylpyrrolidone)], and a sacrificial donor [1-benzyl-1,4-dihydronicotinamide]. Photoinduced electron transfer occurs between the encapsulated dye molecule inside the SWCNT and the MV2+ ion outside the SWCNT. This is followed by the relay of the electron to the co-catalyst, which reduces H+ to generate H2. The external quantum yield of the H2 evolution reached a maximum of 8.5% under irradiation with light at 510 nm. Notably, the photoinduced electron transfer between the molecules on the inside and the outside of the SWCNT proceeded smoothly despite the possibility of energy migration from the encapsulated dye to the SWCNT or the possibility of charge recombination.
Consistent coupling algorithms for coupled core-edge simulations of plasma turbulence
Authors: Ricketson L. , Hakim A. , Hittinger J.
Published: January 2021

Two schemes for coupling gyrokinetic simulations of microturbulence in tokamaks are proposed. The first scheme is based on an additive Schwarz domain decomposition. We show that, because the goal of turbulence is long-time averages of the dynamics rather than temporal accuracy, the iteration to self-consistency across domains, which is typically required by Schwarz schemes, can be avoided, thereby accelerating the computation. Second, we propose a coupling scheme that relies entirely on the addition of source terms, leaving the boundary conditions arbitrary. The practical motivations for such a scheme are discussed, and forms of the source terms that ensure consistency and stability are derived. The schemes are tested on a nonlinear, one-dimensional model problem, and the first scheme is further tested on the Hasegawa–Wakatani model.
A perpendicular field electromagnet with a 250 mm access bore
Authors: Petrović A. P. , Smit B. H. M. , Fong K. L. , Satywali B. , Tee X. Y. , Panagopoulos C.
Published: January 2021

We present a laboratory electromagnet capable of generating magnetic fields up to ±0.48 T, specifically designed as a perpendicular flux source for thin film samples in an ambient environment. The magnet features a 250 mm diameter clear access bore above the sample plane, thus offering compatibility with a wide variety of experimental apparatus. Despite its generous size, the magnet thermally dissipates less than 1 kW at maximum field. A shaped ferromagnetic core is used to amplify and homogenize the field B, leading to an estimated uniformity of ±1.5 mT (≲0.3%) in B within a 28 mm2 zone at maximum field. The sample stage is thermally regulated and isolated from the magnet, enabling temperature control with ±5 mK precision even at elevated magnetic fields.
Spectral inclusion and pollution for a class of dissipative perturbations
Authors: Stepanenko Alexei
Published: January 2021

Spectral inclusion and spectral pollution results are proved for sequences of linear operators of the form T0 + iγsn on a Hilbert space, where sn is strongly convergent to the identity operator and γ > 0. We work in both an abstract setting and a more concrete Sturm–Liouville framework. The results provide rigorous justification for a method of computing eigenvalues in spectral gaps.
Photophysics behind luminescence phenomenon in conducting conjugate polymer blends for application as an emissive layer in PLEDs
Authors: Banerjee Dhritiman , Kar Asit Kumar
Published: January 2021

Luminescence quenching by polarons is an important loss mechanism in polymer light-emitting diodes (PLEDs). Steady-state and time-resolved photoluminescence spectroscopy of polyaniline (PAni) thin films with varying polaron doping has helped us to realize polaron density-dependent photoluminescence quenching mechanisms inside the thin films. A sharp reduction in photoluminescence emission spectra has been observed at doping densities between 1017 and 1019 cm−3. This doping concentration-dependent photoluminescence phenomenon in PAni is modeled quantitatively using quenching of excitons by polarons through long-range Förster resonance energy transfer (FRET) and short-range charge transfer (CT) mechanisms. The results match well with the experimental findings that demonstrate that both models need to be considered to explain the mechanisms of luminescence quenching. FRET and CT phenomena inside an emissive layer of PLEDs have been demonstrated to play a pivotal role in the quantum efficiency roll-off phenomenon at high current density using experimentally obtained and theoretically calculated kinetic quenching parameters. To get rid of low luminescence in PAni, it has been blended with poly(methyl) methacrylate (PMMA) that enhances its luminescence manifold. The blending of PMMA leads to the introduction of a new photophysical phenomenon—donor PMMA concentration-dependent FRET contrary to original FRET theory proposed by Förster. Concentration-dependent FRET leads to a sharp drop in luminescence from the polymer blend after reaching a critical concentration of PMMA. Therefore, the present study explores the reason behind low luminescence in conducting polymers and demonstrates ways to mitigate it along with providing an account of the photo-physics of the conducting polymer as an emissive layer in PLEDs.
Toward improved models of human cancer
Authors: Welm Bryan E. , Vaklavas Christos , Welm Alana L.
Published: January 2021

Human cancer is a complex and heterogeneous collection of diseases that kills more than 18 million people every year worldwide. Despite advances in detection, diagnosis, and treatments for cancers, new strategies are needed to combat deadly cancers. Models of human cancer continue to evolve for preclinical research and have culminated in patient-derived systems that better represent the diversity and complexity of cancer. Still, no model is perfect. This Perspective attempts to address ways that we can improve the clinical translatability of models used for cancer research, from the point of view of researchers who mainly conduct cancer studies in vivo.
Controlled exciton–plasmon coupling in a mixture of ultrathin periodically aligned single-wall carbon nanotube arrays
Authors: Adhikari C. M. , Bondarev I. V.
Published: January 2021

We study theoretically the in-plane electromagnetic response and the exciton–plasmon interactions for an experimentally feasible carbon nanotube (CN) film system composed of parallel aligned periodic semiconducting CN arrays embedded in an ultrathin finite-thickness dielectric. For homogeneous single-CN films, the intertube coupling and thermal broadening bring the exciton and interband plasmon resonances closer together. They can even overlap due to the inhomogeneous broadening for films composed of array mixtures with a slight CN diameter distribution. In such systems, the real part of the response function is negative for a broad range of energies (negative refraction band), and the CN film behaves as a hyperbolic metamaterial. We also show that for a properly fabricated two-component CN film, by varying the relative weights of the two constituent CN array components, one can tune the optical absorption profile to make the film transmit or absorb light in the neighborhood of an exciton absorption resonance on-demand.
Resolving dynamics of inertial migration in straight and curved microchannels by direct cross-sectional imaging
Authors: Zhou Jian , Papautsky Ian
Published: January 2021

The explosive development of inertial microfluidic systems for label-free sorting and isolation of cells demands improved understanding of the underlying physics that dictate the intriguing phenomenon of size-dependent migration in microchannels. Despite recent advances in the physics underlying inertial migration, migration dynamics in 3D is not fully understood. These investigations are hampered by the lack of easy access to the channel cross section. In this work, we report on a simple method of direct imaging of the channel cross section that is orthogonal to the flow direction using a common inverted microscope, providing vital information on the 3D cross-sectional migration dynamics. We use this approach to revisit particle migration in both straight and curved microchannels. In the rectangular channel, the high-resolution cross-sectional images unambiguously confirm the two-stage migration model proposed earlier. In the curved channel, we found two vertical equilibrium positions and elucidate the size-dependent vertical and horizontal migration dynamics. Based on these results, we propose a critical ratio of blockage ratio (β) to Dean number (De) where no net lateral migration occurs (β/De ∼ 0.01). This dimensionless number (β/De) predicts the direction of lateral migration (inward or outward) in curved and spiral channels, and thus serves as a guideline in design of such channels for particle and cell separation applications. Ultimately, the new approach to direct imaging of the channel cross section enables a wealth of previously unavailable information on the dynamics of inertial migration, which serves to improve our understanding of the underlying physics.
Marangoni patterns on a rhombic lattice in a thin film heated from below
Authors: Samoilova Anna E. , Nepomnyashchy Alexander
Published: January 2021

Pattern formation due to oscillatory Marangoni instability in a thin film heated from below is studied. We focus on the stability of patterns that are produced by nonlinear interaction of two standing waves propagating at the angle ϕ between the wave vectors. We provide weakly nonlinear analysis within the amplitude equations, which govern the evolution of the layer thickness and the characteristic temperature. This leads to a set of four complex Landau equations that govern the evolution of wave amplitudes. The coefficients of Landau equations, which define pattern formation, have been calculated in a wide range of governing parameters. Stable traveling rectangles and alternating rolls on a rhombic lattice are detected.
On-chip optical non-reciprocity through a synthetic Hall effect for photons
Authors: Kim Soonwook , Sohn Donggyu B. , Peterson Christopher W. , Bahl Gaurav
Published: January 2021

We demonstrate a synthetic Hall effect for light, using an acousto-optically modulated nanophotonic resonator chain. To produce this effect, we simultaneously generate the required synthetic electric field using temporal modulation and the required synthetic magnetic field using spatial modulation of the resonator chain. We show how the combination of these synthetic fields transverse to the direction of light propagation can be used to produce non-reciprocal optical transmission, as a basis for new photonic and topological devices.
Cavity-enhanced light–matter interaction in Vogel-spiral devices as a platform for quantum photonics
Authors: Trojak Oliver J. , Gorsky Sean , Murray Connor , Sgrignuoli Fabrizio , Pinheiro Felipe A. , Dal Negro Luca , Sapienza Luca
Published: January 2021

Enhancing light–matter interactions on a chip is of paramount importance for classical and quantum photonics, sensing, and energy harvesting applications. Several photonic geometries have been developed, allowing high extraction efficiencies, enhanced light–matter interactions, and control over the spontaneous emission dynamics of solid-state quantum light sources. To this end, a device geometry resilient to nanofabrication imperfections, providing high-quality light confinement and control over the emitted light properties, would be desirable. We demonstrate that aperiodic arrangements, whose geometry is inspired by natural systems where scattering elements are arranged following Fibonacci series, represent a platform for enhancing the light–matter interaction in on-chip nanophotonic devices, allowing us to achieve efficient visible light confinement. We use optically active defect centers in silicon nitride as internal light sources to image and characterize, by means of microphotoluminescence spectroscopy, the individual optical modes confined by photonic membranes with Vogel-spiral geometry. By studying the statistics of the measured optical resonances, in combination with rigorous multiple scattering theory, we observe lognormal distributions and report quality factors with values as high as 2201 ± 443. Our findings improve the understanding of the fundamental physical properties of light-emitting Vogel-spiral systems and show their application to active nanophotonic devices. These results set the basis for further development of quantum devices that leverage the unique properties of aperiodic Vogel spiral order on a chip, including angular momentum states, thus producing mode structures for information processing and communications.
Turbulent thermal convection driven by free-surface evaporation in cuboidal domains of different aspect ratios
Authors: Hay William A. , Martin Jimmy , Migot Benoît , Papalexandris Miltiadis V.
Published: January 2021

In this paper, we present simulations of turbulent thermal convection driven by free-surface evaporation above and by a heated wall below. A novel algorithm is proposed for predicting evaporation rates at a free surface, which we then validate against experimental data. At the top of a cuboidal domain, a shear-free boundary condition acts as an approximation of the free surface. We first focus on a domain of aspect ratio Γ = 1, where a fully resolved direct numerical simulation is carried out at a moderate Rayleigh number, Ra = 1.2 × 107, and we compare flow statistics with a Large-Eddy Simulation (LES) on a coarse grid. Both the fully resolved simulation and the LES predict well the time- and area-averaged evaporation rate and free surface temperature when compared with the experimental data. Next, we carry out a series of LES with an increasing lower wall temperature and, consequently, Ra. We then validate the evaporation model by comparing LES predictions of the time- and area-averaged mass flux and temperature at the upper boundary against the experimental measurements. The aspect ratio of the domain is then reduced, and we show, for the first time, the transition to a dual-roll state of the large-scale circulation (LSC) at the aspect ratio of Γ = 1/4 in a cuboidal domain. The temperature and velocity distributions at the free surface are impacted by the state of the LSC. However, we find that the water-side turbulence and aspect ratio play a negligible role on the evaporation rate above, in accordance with experimental observations.
Long-term thermal stability, β relaxation, and mechanical behavior of a LaCe-based bulk metallic glass
Authors: Bian Bingchuan , Cui Xiao , Li Jinjing
Published: January 2021

In this work, the long-term thermal stability, dynamic relaxation behavior, and mechanical performance of (La60Ce40)60Al15Co25 bulk metallic glass (BMG) were studied using differential scanning calorimetry, internal friction measurement, and compression testing, respectively. The long-term stability of the LaCe-based BMG was realized by constructing a continuous heating transformation diagram on the basis of the kinetic characteristics of the crystallization behavior. The internal friction analysis of the LaCe-based BMG showed the emergence of prominent slow β relaxation before the glass transition temperature. The β relaxation had a close relationship with the heterogeneous distribution and the good mobility of the constituting elements. The compression testing results in different temperature ranges near and far from the activation temperature of the β relaxation showed that the plastic deformation could proceed continuously as the deformation temperature reached the activation temperature of the β relaxation.
Acousto-optical analogue of a Fabry – Perot resonator
Authors: Pustovoit V.I.
Published: January 2021

A new method is proposed to increase the spectral resolving power of collinear acousto-optical filters by using optical feedback when the light leaving the region of its interaction with a periodic structure formed in the crystal by an acoustic wave returns to the input of the crystal, in which the diffraction process repeats itself many times. The light beam returned to the interaction region changes the boundary conditions of the parametric diffraction problem, because of which the amplitudes of the diffracted and passed light beams turn out to be strongly dependent on the feedback properties (similar to the processes occurring in a Fabry – Perot optical resonator). It is shown that such a combined acousto-optical Fabry – Perot filter with feedback is able to electronically tune the optical transmission wavelength and simultaneously has a higher spectral resolution than a conventional acousto-optical filter without feedback. It is also shown that the multiple radiation diffraction due to the feedback increases the diffraction efficiency with a comparatively small spatial change in the refractive index of the medium. Explicit analytical expressions for the instrumental functions of a combined acousto-optical Fabry – Perot filter are found and their properties are analysed. It is noted that a change in the feedback by any mechanism, i.e., by changing the returned wave phase or amplitude, leads to modulation of the measured signal, which makes it possible to create more precise methods of spectral measurements.
Analysis of the pulse waveform in arterial vessels using the spectrum of the autodyne signal of a laser interferometer
Authors: Skripal An.V. , Dobdin S.Yu. , Dzhafarov A.V. , Chernetsova I.A.
Published: January 2021

The results of measuring the derivative of the pulse wave using a laser autodyne based on the Fourier analysis of the low-frequency spectrum of the interference signal are presented. The features of using the windowed Fourier transform for window types and window widths are discussed. The correlation coefficient between the derivative obtained by direct differentiation of the sphygmographic signal and the frequency dependence of the windowed Fourier transform obtained from the analysis of the interference signal is calculated. It is shown that the amplitude of biovibration of the skin surface has the greatest influence on the correlation of the frequencies of the window spectrum of the autodyne signal with direct measurements of the pulse wave parameters by the sphygmographic method. Using a hardware-software system, we measured the sphygmogram of the pulse wave in the radial artery in a 19-year-old man who did not suffer from cardiovascular diseases. The derivative of the pulse wave obtained from the sphygmogram was compared with the dependence of the frequencies of the window spectrum of the autodyne signal. A comparative analysis of the dependences of the frequencies of the spectral harmonics of the window method with the derivative of the sphygmographic pulse showed a good correlation at the amplitudes of biovibration of the skin surface exceeding 10 μm.
Fast method for computer simulation of luminescence characteristics of multilayer biological tissues with embedded luminescent nanoparticles
Authors: Yakovlev D.D. , Sagaidachnaya E.A. , Yakovlev D.A. , Kochubey V.I.
Published: January 2021

We report a fast and computationally stable method for computer simulation of optical properties of layered scattering systems containing luminescent layers. The method is based on the solution of one-dimensional scalar radiative transfer equations and makes it possible to calculate spectral and angular characteristics of luminescent radiation emerging from the system under various conditions of luminescence excitation. The method is used to estimate the parameters necessary for determining temperature in subcutaneous layers from luminescence spectra of up-conversion nanoparticles embedded in these layers during transcutaneous optical probing.
Mammal species occupy different climates following the expansion of human impacts
Authors: Pineda-Munoz Silvia , Wang Yue , Lyons S. Kathleen , Tóth Anikó B. , McGuire Jenny L.
Published: January 2021

Significance

Mammals on landscapes within North America are now living in different climates than they did prior to major human expansions. Many smaller animals have expanded into climates now dominated by agricultural and urban regions; whereas large-bodied mammals were forced out of these climates and were relegated to colder, dryer regions. As a result, the distributions of modern mammals do not accurately reflect the range of climatological conditions where species can live. Rather, they reflect the marginalization or facilitation that those species have undergone following the expansion of major human activities. Failing to mitigate the ecological changes that mammals are experiencing can have unprecedented impacts on the future survival of the remaining large-bodied species in North America.
Kallikrein directly interacts with and activates Factor IX, resulting in thrombin generation and fibrin formation independent of Factor XI
Authors: Kearney Katherine J. , Butler Juliet , Posada Olga M. , Wilson Clare , Heal Samantha , Ali Majid , Hardy Lewis , Ahnström Josefin , Gailani David , Foster Richard , Hethershaw Emma , Longstaff Colin , Philippou Helen
Published: January 2021

Significance

Prekallikrein (PK) is a zymogen that is converted to kallikrein (PKa) by factor (F)XIIa. PK and FXII reciprocally activate each other; the resulting FXIIa initiates activation of the coagulation system via the cleavage of FXI to FXIa, which then activates FIX. This manuscript describes a novel high-affinity binding interaction between FIX(a) and PK(a) and reports that PKa can dose- and time-dependently activate FIX to generate FIXa, resulting in thrombin generation and clot formation independent of FXIa. Characterization of the kinetics of FIX activation reveal that PKa is a more significant activator of FIX than previously considered. This work highlights a new amendment to the coagulation cascade where PKa can directly activate FIX.
Cellular autofluorescence is magnetic field sensitive
Authors: Ikeya Noboru , Woodward Jonathan R.
Published: January 2021

Significance

The radical pair mechanism is the favored hypothesis for explaining biological effects of weak magnetic fields, such as animal magnetoreception and possible adverse health effects. To date, however, there is no direct experimental evidence for magnetic effects on radical pair reactions in cells, the fundamental building blocks of living systems. In this paper, using a custom-built microscope, we demonstrate that flavin-based autofluorescence in native, untreated HeLa cells is magnetic field sensitive, due to the formation and electron spin–selective recombination of spin-correlated radical pairs. This work thus provides a direct link between magnetic field effects on chemical reactions measured in solution and chemical reactions taking place in living cells.
Diversification of mammalian deltaviruses by host shifting
Authors: Bergner Laura M. , Orton Richard J. , Broos Alice , Tello Carlos , Becker Daniel J. , Carrera Jorge E. , Patel Arvind H. , Biek Roman , Streicker Daniel G.
Published: January 2021

Significance

Satellites are virus-like agents which require both a host and a virus to complete their life cycle. The only human-infecting satellite is hepatitis delta virus (HDV), which exacerbates liver disease in patients co-infected with hepatitis B virus (HBV). How HDV originated is a long-standing evolutionary puzzle. Using terabase-scale data mining, coevolutionary analyses, and field studies in bats, we show that deltaviruses can jump between highly divergent host species. Our results further suggest that the contemporary association between HDV and HBV likely arose following zoonotic transmission from a yet-undiscovered animal reservoir in the Americas. Plastic host and virus associations open prospects that deltaviruses might alter the virulence of multiple viruses in multiple host species.
The 2018 reawakening and eruption dynamics of Steamboat Geyser, the world’s tallest active geyser
Authors: Reed Mara H. , Munoz-Saez Carolina , Hajimirza Sahand , Wu Sin-Mei , Barth Anna , Girona Társilo , Rasht-Behesht Majid , White Erin B. , Karplus Marianne S. , Hurwitz Shaul , Manga Michael
Published: January 2021

Significance

Natural geysers episodically erupt liquid water and steam and, thus, provide a window into multiphase hydrothermal systems. The size of and interval between eruptions can shift over time due to changes in the hydrothermal system and due to deeper magmatic processes. An improved understanding of geyser dynamics can provide insights into other multiphase episodic processes on Earth and other planets that result from localized input of energy and mass (e.g., volcanism).
Spillover outcomes of job insecurity: differences among men and women (Consecuencias indirectas de la inseguridad laboral: diferencias entre hombres y mujeres)
Authors: Sora Beatriz , Caballer Amparo , Peiró José M.
Published: January 2021

A vast literature on job insecurity can be found. However, there are still several significant research gaps. Little attention has been paid to the spillover effect of job insecurity on employees’ family, and the role of gender in relation to job insecurity is unclear. Hence, the purpose of this study was twofold: first, to analyse the potentially detrimental effects of job insecurity on employees’ families (e.g., family satisfaction, family cohesion and family flexibility); and second, to determine whether there are differences between men and women in job insecurity perception and its association with the spillover outcomes in family domain. In fact, this study tested competing theoretical predictions surrounding the role of gender related to job insecurity. Using hierarchical multiple regression analyses, the following hypotheses were confirmed: (1) job insecurity was related to lower levels of family satisfaction, family cohesion and family flexibility; (2) gender moderated the relationship between job insecurity and family outcomes, but curiously this moderation results were in an unexpected direction. Women increased their family cohesion and family flexibility when they experienced job insecurity. However, non-differences in job insecurity perception between men and women were found.