bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental evidence for super-Alfvénic acceleration of the field-reversed configuration due to a magnetic pressure gradient
Authors: Kobayashi Daichi , Asai Tomohiko
Published: February 2021

The super-Alfvénic acceleration of an extremely high beta plasmoid due to a magnetic pressure gradient is evidenced in translation experiments involving the field-reversed configuration (FRC) in the FRC amplification via the translation-collisional merging (FAT-CM) device. Inside the FRC, there is a population of unmagnetized particles that forms a volume with extremely high beta. Formed using the field-reversed theta pinch method, the FRC is accelerated and injected into a quasi-static confinement magnetic field that is weaker than the formation and acceleration fields. Because the FRC is injected with nonzero axial translation speed and cannot slow down, its speed exceeds the Alfvénic and sonic speed upon entering the confinement field. This phenomenon is predicted from two-dimensional resistive magnetohydrodynamic simulations, and experimental results that are consistent with the magnetohydrodynamic approximation show that the FRC acceleration process is due mainly to magnetic pressure on the thin magnetized layer.
Performance and uniformity of a kilo-pixel array of Ti/Au transition-edge sensor microcalorimeters
Authors: Taralli E. , D’Andrea M. , Gottardi L. , Nagayoshi K. , Ridder M. L. , de Wit M. , Vaccaro D. , Akamatsu H. , Bruijn M. P. , Gao J. R.
Published: February 2021

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3 eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 μm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1 cm) is less than 1.5 mK. We found a large region of detector’s bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3 eV. In particular, results show a summed x-ray spectral resolution ΔEFWHM = 2.50 ± 0.04 eV at a photon energy of 5.9 keV, measured in a single-pixel mode using a frequency domain multiplexing readout system developed at SRON/VTT at bias frequencies ranging from 1 MHz to 5 MHz. Moreover, we compare the logarithmic resistance sensitivity with respect to temperature and current (α and β, respectively) and their correlation with the detector’s noise parameter M, showing a homogeneous behavior for all the measured pixels in the array.
Slow photoionization via higher excited states of N,N-dimethylaniline in ethanol solution probed by femtosecond transient absorption spectroscopy under two-pulse two-photon excitation
Authors: Koga Masafumi , Miyake Yuto , Hayasaka Mizuki , Sotome Hikaru , Miyasaka Hiroshi
Published: February 2021

Photoionization dynamics of N,N-dimethylaniline (DMA) from highly electronically excited states in ethanol solution was investigated by means of femtosecond two-pulse two-photon excitation transient absorption (2PE-TA) spectroscopy. The first pump pulse prepares the lowest singlet excited state (S1 state) of DMA, and the second one excites the S1 state into higher excited states. In the case with the second pulse at 500 nm, the ionization took place via a rapid channel (<100 fs) and a slow one with the time constant of ∼10 ps. The excitation wavelength effect of the second pulse indicated that a specific electronic state produced directly from higher excited states was responsible for the slow ionization. By integrating these results with the time evolution of the transient absorption spectra of the solvated electron in neat ethanol detected by the simultaneous two-photon excitation, it was revealed that the slow ionization of DMA in ethanol was regulated by the formation of the anionic species just before the completion of the solvation of the electron, leading to the solvated electron in the relaxed state. From these results, it was strongly suggested that the capture of the electron of the Rydberg-like state by the solvent or solvent cluster regulates the appearance of the cation radical.
Stress distribution at the AlN/SiC heterointerface probed by Raman spectroscopy
Authors: Breev I. D. , Likhachev K. V. , Yakovleva V. V. , Hübner R. , Astakhov G. V. , Baranov P. G. , Mokhov E. N. , Anisimov A. N.
Published: February 2021

We grow AlN/4H-SiC and AlN/6H-SiC heterostructures by physical vapor deposition and characterize the heterointerface with micro-scale resolution. We investigate the spatial stress and strain distribution in these heterostructures using confocal Raman spectroscopy. We measure the spectral shifts of various vibrational Raman modes across the heterointerface and along the entire depth of the 4H- and 6H-SiC layers. Using the earlier experimental prediction for the phonon-deformation potential constants, we determine the stress tensor components in SiC as a function of the distance from the AlN/SiC heterointerface. Despite the fact that the lattice parameter of SiC is smaller than that of AlN, the SiC layers are compressively strained at the heterointerface. This counterintuitive behavior is explained by different coefficients of thermal expansion of SiC and AlN when the heterostructures are cooled from growth to room temperature. The compressive stress values are maximum at the heterointerface, approaching 1 GPa, and relax to the equilibrium value on the scale of several tens of micrometers from the heterointerface.
Reduced-order modeling of plasma ionization due to multifluid, collisional-radiative effects
Authors: Abrantes Richard J. E. , Martin Robert S.
Published: February 2021

Collisional rate calculations which account for relative multifluid streaming were implemented in a collisional-radiative model that is applicable for a generalized set of atomic elements. The rate modifications for multifluid streaming were derived in two recent studies for electron-impact excitation, de-excitation, ionization, and recombination [H. P. Le and J.-L. Cambier, Phys. Plasmas 22, 093512 (2015); 23, 063505 (2016)]. This study follows from the previous studies by extending the derivations to radiative recombination. However, the memory intensive aspect of expanding the collisional rate tabulations to temperature and multifluid effects can become a numerical obstacle for large-scale plasma simulations. The main objective of this study is to explore reduced-order modeling approaches for collisional-radiative systems that may adopt collisional rate accounting for multifluid streaming. The ionization test case simulated in this work uses the quasi-steady-state solution and two Boltzmann grouping approaches, one of which is the ionic excitation concept and the other being a relatively finer selection of Boltzmann groups. The reduced-order models captured the general trend of the detailed model, providing a foundation from which to improve or perform coupled plasma simulations in the future.
Three-dimensional patterned distribution of thermal conductivity in the volume for effective thermal concentration
Authors: Qin Fahao , Wang Lanlan , Jiang Weitao , Zhang Yajun , Liu Hongzhong
Published: February 2021

For thermal devices and electronic systems, heat flow manipulation is critical to meet various needs. In this article, based on transformation thermodynamics, three-dimensional (3D) structures in the volume for patterned thermal conductivity were designed and fabricated. The 3D structures in the volume acting as heat flow routes can be achieved as pre-designed, providing a promising method to manipulate heat flow applied to the localized thermal concentration, thermal cloaking, etc. Simulation and experiments show that, by the 3D structures for thermal concentration, the heat flow could be concentrated to the pre-designed region, 7.0 K higher compared to the isotropic sample without any internal structures, and with a temperature gradient of over 1.3 K mm−1 to the surroundings (the heat source is 361 K), indicating an effective heat concentration. It also reveals that the heat flow could be accurately manipulated by carefully designing the geometric and material parameters of the internal structures, providing an alternative method to construct a 3D matrix for heat flow manipulation in the volume.
Expansion opacity in laboratory conditions
Authors: Glazyrin S. I. , Blinnikov S. I. , Roudskoy I. V. , Golubev A. A. , Rosmej O. N. , Pikuz S. A.
Published: February 2021

Radiation–matter interaction depends mainly on the state of matter (its density, temperature, etc.), and also on the radiation spectrum. The opacity of thick plasma also depends on plasma velocity—the Doppler effect shifts atomic lines. For the cases when there are many bound–bound transitions, i.e., the plenty of lines contribute to the opacity, the latter is enhanced when the plasma expands with a nonuniform velocity field. It is known as “expansion opacity” in the literature. Existing models are discrepant and predict diverse results in some cases. Here, we present a rigorous derivation of the effect and show that the effect is available for experimental study at modern laser facilities. The plasma created by a Cu target irradiated with an ∼100 J nanosecond laser pulse is rich in lines and has enough expansion velocity so that its opacity is increased in the spectral range ∼102−103 eV by the order of magnitude. The possible experimental measurement of the effect is briefly discussed.
A second order yield-temperature relation for accurate inference of burn-averaged quantities in multi-species plasmas
Authors: Kabadi N. V. , Adrian P. J. , Bose A. , Casey D. T. , Frenje J. A. , Gatu Johnson M. , Lahmann B. , Mannion O. M. , Petrasso R. D. , Rinderknecht H. G. , Séguin F. H. , Sio H. W. , Sutcliffe G. D. , Zylstra A. B.
Published: February 2021

Measured yields and ion temperatures inferred from the fusion product energy spectra can be used as metrics for the performance of an ICF implosion. This can be used to infer species separation, thermal decoupling, flows, or other effects that can cause the inferred ion temperatures to deviate from the true underlying thermal temperature and the yield ratio to deviate from the expected value. Direct inference of the impact of these effects on observed temperatures and yields can be difficult to uncover due to the underlying dependence on the shape and time evolution of the temperature and density profiles of the fusing plasma. Due to differences in the temperature dependence of the reactivities, different fusion products are emitted from different regions and times within the implosion. In order to properly account for this, a second-order analytical expression relating the apparent temperatures and yield ratios is developed. This expression can be coupled to models of yield and/or temperature altering effects to infer their burn-averaged impact on an implosion. The second-order expression shows significant improvement over lower-order expressions in synthetic data studies. Demonstrations of its applications to synthetic data coupled with models of ion thermal decoupling and radial flows are presented. In the case of thermal decoupling, both first and second-order expressions show reasonable levels of accuracy. To consistently infer the amplitude of radial flow with a <10% error, the second-order equation is required.
Random-matrix theory for the Lindblad master equation
Authors: Lange Stefan , Timm Carsten
Published: February 2021

Open quantum systems with Markovian dynamics can be described by the Lindblad equation. The quantity governing the dynamics is the Lindblad superoperator. We apply random-matrix theory to this superoperator to elucidate its spectral properties. The distribution of eigenvalues and the correlations of neighboring eigenvalues are obtained for the cases of purely unitary dynamics, pure dissipation, and the physically realistic combination of unitary and dissipative dynamics.
Reflecting metagrating-enhanced thin-film organic light emitting devices
Authors: Xu Xin , Kwon Hoyeong , Finch Stanley , Lee Jae Young , Nordin Leland , Wasserman Daniel , Alù Andrea , Dodabalapur Ananth
Published: February 2021

Organic light emitting diodes can achieve close to unitary internal quantum efficiency; however, their external quantum efficiency is much lower due to losses within the device. Gradient metasurfaces and metagratings can be utilized to achieve substantial electromagnetic field manipulation and enhancement of the local density of photonic states, thereby improving the external quantum efficiency of organic light emitting devices. In this work, we show how suitably designed reflecting plasmonic metagratings can be potentially incorporated into a top-emitting organic light emitting device, resulting in large enhancement of light emissivity by effectively coupling out the light trapped in the waveguide modes. We describe how both periodic and quasiperiodic metagratings can be used to improve device performance. Electromagnetic simulations and measurements show that our metagratings greatly enhance the electromagnetic field intensity in the light emission layer, leading to increased emission normal to the plane of the layers (by up to a factor of 4.8) and suppression of light trapping typically lost into waveguide modes.
Ensemble-level energy transfer measurements can reveal the spatial distribution of defect sites in semiconductor nanocrystals
Authors: Nilsson Zach N. , Beck Lacey M. , Sambur Justin B.
Published: February 2021

Energy transfer measurements are widely used to measure the distance between donors and acceptors in heterogeneous environments. In nanocrystal (NC)-molecule donor–acceptor systems, NC defects can participate in electronic energy transfer (EnT) in a defect-mediated EnT process. Here, we explore whether ensemble-level spectroscopy measurements can quantify the distance between the donor defect sites in the NC and acceptor molecules. We studied defect-mediated EnT between ZnO NCs and Alexa Fluor 555 (A555) because EnT occurs via emissive NC defect sites, such as oxygen vacancies. We synthesized a size series of ZnO NCs and characterized their radii, concentration, photoluminescence (PL) lifetime, and defect PL quantum yield using a combination of transmission electron microscopy, elemental analysis, and time-resolved PL spectroscopy. The ZnO defect PL decay kinetics were analyzed using the stochastic binding (SB) and restricted geometry (RG) models. Both models assume the Förster point dipole approximation, but the RG model considers the geometry of the NC donor in the presence of multiple acceptors. The RG model revealed that the emissive defect sites are separated, on average, 0.5 nm from the A555 acceptor molecules. That is, the emissive defect sites are predominantly located at or near the surface of large NCs. The SB model revealed the average number of A555 molecules per NC and the equilibrium binding constant but did not provide meaningful information regarding the defect–acceptor distance. We conclude that ensemble-level EnT measurements can reveal the spatial distribution of defect sites in NCs without the need for interrogating the sample with a microscope.
Role of magnetic ordering in the phase coexistence at the structural instability of the multiferroic BiFeO3–PbTiO3
Authors: Fernández-Posada Carmen M. , Castro Alicia , del Real Rafael P. , Algueró Miguel , Amorín Harvey
Published: February 2021

A promising approach for obtaining a large magnetoelectric response at room temperature in single-phase materials is to make use of phase-change phenomena at structural instabilities of a multiferroic state. This is the case of perovskites showing the morphotropic phase boundary (MPB) between ferroelectric polymorphs with differentiated magnetic orderings, like in BiFeO3–PbTiO3. Indeed, distinctive magnetoelectric effects were recently shown in Mn-modified BiFeO3–PbTiO3, associated with the electric field-induced phase transition between the coexisting MPB phases. We report here analogous effects under the magnetic field in 0.7BiFeO3–0.3PbTiO3, which shed light on the reversibility of the phase-change phenomena and the role of the magnetic ordering in the phase coexistence at the structural instability characteristic of the MPB. Results demonstrate magnetic field-driven phase-change phenomena.
Power and area efficient stochastic artificial neural networks using spin–orbit torque-based true random number generator
Authors: Song Min , Duan Wei , Zhang Shuai , Chen Zhenjiang , You Long
Published: February 2021

Hardware implementations of Artificial Neural Networks (ANNs) using conventional binary arithmetic units are computationally expensive and energy-intensive together with large area footprints. Stochastic computing (SC) is an unconventional computing paradigm that operates on stochastic bit streams. It can offer low-power and area-efficient hardware implementations and has shown promising results when applied to ANN hardware circuits. SC relies on stochastic number generators (SNGs) to map input binary numbers to stochastic bit streams. The SNGs are conventionally implemented using random number generators (RNGs) and comparators. Linear feedback shifted registers (LFSRs) are typically used as the RNGs, which need far more area and power than the SC core, counteracting the latter's main advantages. To mitigate this problem, in this Letter, RNGs employing Spin–Orbit Torque (SOT)-induced stochastic switching of perpendicularly magnetized Ta/CoFeB/MgO nanodevices have been proposed. Furthermore, the SOT true random number generator (TRNG) is integrated with the simple CMOS stochastic computing circuits to perform a stochastic artificial neural network. To further optimize power and area efficiency, a fully parallel architecture and TRNG-sharing scheme are presented. The proposed stochastic ANN using the SOT-based TRNG obtains a negligible inference accuracy loss, compared with the binary version, and achieves 9× and 25× improvement in terms of area and power, respectively, compared with the ANN using LFSRs.
Dielectric and electro-mechanic nonlinearities in perovskite oxide ferroelectrics, relaxors, and relaxor ferroelectrics
Authors: Riemer Lukas M. , Jin Li , Uršič Hana , Otonicar Mojca , Rojac Tadej , Damjanovic Dragan
Published: February 2021

The polarization and strain response of ferroelectric materials at electric fields below the macroscopic coercive field is of paramount importance for the operation of many electronic devices. The response of real ferroelectric and related materials is, in general, complex and difficult to interpret. The reason for this is that many processes in a ferroelectric material contribute to its properties, often concurrently. Examples include the motion of ferroelectric and ferroelastic domains, the presence of domains within domains, the dynamics of different types of polar nano-entities, the interaction of polar nano-entities (e.g., polar nanoregions in relaxors) with the strain and polarization within domains, motion of defects, and rearrangement of defect clusters and their interaction with polarization and strain. One signature of these processes is nonlinearity of the strain and polarization. Most ferroelectrics exhibit nonlinear response at all practical field levels, meaning that the apparent material coefficients depend on the amplitude of the driving excitation. In this paper, we show that an investigation of nonlinear behavior is a sensitive way to study various mechanisms operating in dielectric and piezoelectric materials. We review the basic formalism of the nonlinear description of polarization and strain, give a physical interpretation of different terms, and illustrate this approach on numerous examples of relaxors, relaxor ferroelectrics, hard and soft ferroelectrics, and morphotropic phase boundary compositions. An experimental approach based on a lock-in technique that is well suited for such studies is also discussed.
AlGaN/GaN MISHEMTs with epitaxially grown GdScO3 as high-
κ
dielectric
Authors: Seidel Sarah , Schmid Alexander , Miersch Christian , Schubert Jürgen , Heitmann Johannes
Published: February 2021

Epitaxially grown GdScO3 was integrated in a GaN-based metal-insulator-semiconductor high electron mobility transistor as a high-κ gate passivation layer. Microstructural investigations using transmission electron microscopy and x-ray diffraction confirm the epitaxial growth of GdScO3 on GaN deposited by pulsed laser deposition on the AlGaN-GaN heterostructure. The metal-insulator-semiconductor high electron mobility transistor was compared to unpassivated and to Al2O3 passivated high electron mobility transistors. A layer of 20 nm GdScO3 reduces the gate leakage current below the level of the Al2O3 passivated transistors and below the off-current of the high electron mobility transistor without any gate dielectric. Time-dependent measurements show a strong dependence of the drain leakage current in the off-state on light illumination, which indicates slow trapping effects in GdScO3 or at the GdScO3–GaN interface.
Ordinal patterns in the Duffing oscillator: Analyzing powers of characterization
Authors: Gunther Ivan , Pattanayak Arjendu K. , Aragoneses Andrés
Published: February 2021

Ordinal patterns are a time-series data analysis tool used as a preliminary step to construct the permutation entropy, which itself allows the same characterization of dynamics as chaotic or regular as more theoretical constructs such as the Lyapunov exponent. However, ordinal patterns store strictly more information than permutation entropy or Lyapunov exponents. We present results working with the Duffing oscillator showing that ordinal patterns reflect changes in dynamical symmetry that is invisible to other measures, even permutation entropy. We find that these changes in symmetry at given parameter values are correlated with a change in stability at neighboring parameters, which suggests a novel predictive capability for this analysis technique.
Hybrid improper ferroelectricity in A-site cation ordered Li2La2Ti3O10 ceramic with triple-layer Ruddlesden–Popper structure
Authors: Zhang Bi Hui , Xu Diming , Chen Bu Hang , Liu Xiao Qiang , Hester James R. , Chen Xiang Ming
Published: February 2021

Hybrid improper ferroelectricity has been extensively studied in double-layer Ruddlesden–Popper oxides in recent years. Although the hybrid improper ferroelectricity could be created among triple-layer Ruddlesden–Popper oxides with an ordered A-site cation predicted by the first-principles calculations, no experimental result has been reported yet. In the present work, the room-temperature ferroelectricity has been observed in Li2La2Ti3O10 ceramics with an A-site cation ordered triple-layer Ruddlesden–Popper structure. The polar phase P21ab has been determined by combining the first-principles calculation and the powder diffraction analysis at room temperature. The hybrid improper ferroelectricity was induced by the triple-coupled irreps including the A-site cation ordering. The variable temperature differential scanning calorimetry measurements and dielectric responses indicate no evidence of phase transition over the temperature range of 200–1080 K. The present work sheds light on designing the hybrid improper ferroelectrics in A-site ordered triple-layer Ruddlesden–Popper compounds.
Micromagnetic understanding of switching and self-oscillations in ferrimagnetic materials
Authors: Cutugno Francesco , Sanchez-Tejerina Luis , Tomasello Riccardo , Carpentieri Mario , Finocchio Giovanni
Published: February 2021

Ferrimagnetic materials (FiMs) represent a promising direction for the realization of spin-based devices since they can combine the ultrafast dynamics typical of antiferromagnets in an easier way to control the magnetic state typical of ferromagnets. In this work, we micromagnetically analyze the magnetization dynamics of a current-driving transition metal/rare earth ferrimagnet in a spin Hall geometry as a function of the uncompensation parameter of the angular moments of the two sublattices. We show that, for a uniaxial FiM, a self-oscillation is the only possible dynamical state at the angular momentum compensation point. We also find a finite discontinuity near the magnetization compensation point originated from the demagnetizing field, which controls the type of dynamics behind the switching. We finally show the effect of the interfacial Dzyaloshinskii–Moriya interaction on both the switching time and the self-oscillation frequency and amplitude.
Electronic dispersions of a stable twisted bilayer phosphorene in 2O-tαP phase
Authors: Pan Douxing
Published: February 2021

It is reported for the electronic properties of an in-plane twisted bilayer phosphorene, known as the 2O-tαP phase, and the only dynamically stable phase beyond the AB stacking. This was achieved using first-principles calculations, a generalized empirical tight-binding model inclusive of electric field effects, and a two-parameter low energy effective model, the latter two providing an efficient scheme for nanoelectronics related applications. The tight-binding model reproduces a global fit to the first-principles dispersion, and the low energy model provides more accurate near-gap bands. Both are orders-of-magnitude faster and less memory-intensive than performing first-principles calculations. The twisted 2O-tαP structure possesses a direct bandgap of 1.27 eV, larger than that of the shifted AB structure (1.03 eV). The hole and electron polar effective mass anisotropy ratios are 27.34 and 1.95, respectively. An important observation is that the layer twisting results in the removal of Dirac cones as a reflection of a different band topology compared to the AB one, while the twofold degeneracy at the Brillouin zone boundary and the symmetry of the energy surface are both broken by an external vertical electric field. With an increasing electric field strength, a decreasing bandgap and an increasing energy difference between the valence band maximum and the twisted band point are both predicted by the tight-binding model and the low energy model.
Ultraviolet-light-triggered isomerization of Rydberg-excited propanal: Real-time capture of ultrafast structural evolution and dynamics investigation
Authors: Wang Yanmei , Gu Zhenfei , Deng Xulan , Zhang Bing
Published: February 2021

Structure rearrangement processes, such as isomerization, are attracting extensive interest as a potential carrier in molecular scale electronics design. UV-light-triggered isomerization of Rydberg-excited propanal with two UV photons has been investigated with time-resolved photoelectron spectroscopy. By following the photoionization from 3s Rydberg states in the time domain, the ultrafast structural evolution and the corresponding photoisomerization dynamics are observed and tracked in real-time. The conversion barrier for isomerization from cis-propanal to gauche isomer is estimated to be about 1500 ± 100 cm−1 experimentally. Both the photoisomerization yield and the conversion rate have shown strong dependence on the excitation energy. It is observed that whether vibration modes are selectively excited or not, cis-to-gauche photoisomerization of propanal in 3s Rydberg state occurs once the excitation energy is higher than the conversion barrier without any vibrational excitation specificity. This yields a powerful approach to studying structural evolution dynamics in large molecules, which may have applications in molecular devices.
Borexino experiment detects neutrinos from the Sun’s carbon-nitrogen-oxygen cycle
Authors: Wilson R. Mark
Published: February 2021

The cycle’s catalytic reactions account for just 1% of the Sun’s energy, but they are the dominant energy producers in heavier stars.
Photoelectrons shine a light on dark excitons
Authors: Middleton Christine
Published: February 2021

The population of the elusive quasiparticles is nearly twice that of their bright counterparts in a two-dimensional semiconductor.
Magnetic fields for modulating the nervous system
Authors: Christiansen Michael G. , Anikeeva Polina
Published: February 2021

Although targeted actuation of neurons via magnetic fields may benefit neuroscience research and medicine, some approaches have sparked controversy.
A Novel Synthesis of 2-Arylbenzimidazole and 2-Arylbenzothiazole Derivatives by MnO
Authors: Amouhadi Elham , Fazaeli Razieh , Aliyan Hamid
Published: February 2021

The main objective of this research is to develop efficient and environmentally benign heterogeneous catalysts for synthesis of 2-arylbenzimidazole and 2-arylbenzothiazoles derivatives by MnO2/MOF-199. For this purpose, a heterogeneous MnO2/MOF-199 catalyst was prepared by the solvothermal method, and the prepared catalyst was characterised by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET, IR, thermogravimetric–differential thermogravimetric (TG-DTG), and temperature-programmed desorption with ammonia (NH3-TPD) analysis. The solid catalyst, with a MnO2/MOF-199 loading of 9 %, demonstrated a high catalytic activity in the synthesis of 1,2-arylbenzimidazole and 1,2-arylbenzothiazole derivatives and the catalyst could be reused for at least 5 cycles under mild conditions.
Developmental synaptic regulator, TWEAK/Fn14 signaling, is a determinant of synaptic function in models of stroke and neurodegeneration
Authors: Nagy Dávid , Ennis Katelin A. , Wei Ru , Su Susan C. , Hinckley Christopher A. , Gu Rong-Fang , Gao Benbo , Massol Ramiro H. , Ehrenfels Chris , Jandreski Luke , Thomas Ankur M. , Nelson Ashley , Gyoneva Stefka , Hajós Mihály , Burkly Linda C.
Published: February 2021

Significance

It is of great importance to elucidate mechanisms underlying the loss or dysfunction of synapses in neurological diseases. The concept that reduced functional synapses in disease reflect aberrant reactivation of pathways mediating synapse elimination in development has yielded candidate mechanisms. Here, we elucidate a role of the cytokine TWEAK and its receptor Fn14, previously shown to be critical in visual development, in synaptic function in the adult brain. We show that limiting this signaling pathway augments synaptic function in models of Alzheimer’s disease and ischemic stroke. Our results support a general role of TWEAK/Fn14 signaling as a regulator of synaptic function across different ages and brain regions, highlighting it as a therapeutic target in diseases featuring synaptic dysfunction.
The
Arabidopsis
GRAS-type SCL28 transcription factor controls the mitotic cell cycle and division plane orientation
Authors: Goldy Camila , Pedroza-Garcia José-Antonio , Breakfield Natalie , Cools Toon , Vena Rodrigo , Benfey Philip N. , De Veylder Lieven , Palatnik Javier , Rodriguez Ramiro E.
Published: February 2021

Significance

The mitotic cell cycle (MCC) sustains plant organ growth by producing new cells in the meristems. Multiple mechanisms of gene expression regulation determine the dynamics of gene expression across the successive phases of the cell cycle. At the transcriptional level, only E2F and MYB3R transcription factors (TFs) have been identified as controlling gene expression dynamics in the MCC. In this work, we analyze the transcriptome of cells in the G2/M phases of the cell cycle and identify SCL28, a previously uncharacterized GRAS TF, as a regulator of the MCC in plants.
Cell dispersal by localized degradation of a chemoattractant
Authors: Karmakar Richa , Tyree Timothy , Gomer Richard H. , Rappel Wouter-Jan
Published: February 2021

Significance

Many studies have investigated how cells can move toward the source of a chemoattractant, but relatively little is known about mechanisms that can cause cells to move away from a location. Here, we show that small aggregates of the social amoebaDictyostelium discoideumcan show dispersal behavior during which cells are moving away from the aggregate. Using a combination of experiments and modeling, we show that this dispersal can arise due to a competition between the diffusible chemoattractant and the enzyme that degrades it, and that the localized degradation of the chemoattractant may be a mechanism for morphogenesis.
Intercellular communication induces glycolytic synchronization waves between individually oscillating cells
Authors: Mojica-Benavides Martin , van Niekerk David D. , Mijalkov Mite , Snoep Jacky L. , Mehlig Bernhard , Volpe Giovanni , Goksör Mattias , Adiels Caroline B.
Published: February 2021

Significance

Many organs have densely packed cells divided in subpopulations that display coherent and spatially differentiated behavior. Using yeast cells packed in a microfluidic device, constructed to mimic an organ structure with peripheral blood flow, we show that cells coupled via diffusion of metabolites can lead to spatially differentiated subpopulations with temporally synchronized behavior. A detailed mathematical model for each yeast cell simulated in its precise architectural location within the microfluidic system correctly predicts the cells’ behavior as a function of an external stress solution. Our results provide us with a mechanistic understanding of this system and indicate how a relatively simple mechanism can underlie a yet poorly understood cellular differentiation process.
GABA from vasopressin neurons regulates the time at which suprachiasmatic nucleus molecular clocks enable circadian behavior
Authors: Maejima Takashi , Tsuno Yusuke , Miyazaki Shota , Tsuneoka Yousuke , Hasegawa Emi , Islam Md Tarikul , Enoki Ryosuke , Nakamura Takahiro J. , Mieda Michihiro
Published: February 2021

Significance

In mammals, the suprachiasmatic nucleus (SCN) functions as the master circadian clock to orchestrate multiple circadian biological rhythms in the body. Although almost all SCN neurons contain γ-aminobutyric acid (GABA) as a neurotransmitter, the physiological roles of GABA in the SCN network are poorly understood. We show that mice lacking GABA release specifically from arginine vasopressin (AVP)-producing neurons, one of the major neuron types in the SCN, retain an SCN that progresses normally at the clock gene level but fires aberrantly with bimodal rhythm. Accordingly, the mice demonstrate locomotor activity at inappropriate times with respect to the clock gene-based SCN clock. GABAergic transmission from AVP neurons may regulate SCN firing rhythm to modulate when SCN molecular clocks enable daily behavior.
Chromatophores efficiently promote light-driven ATP synthesis and DNA transcription inside hybrid multicompartment artificial cells
Authors: Altamura Emiliano , Albanese Paola , Marotta Roberto , Milano Francesco , Fiore Michele , Trotta Massimo , Stano Pasquale , Mavelli Fabio
Published: February 2021

Significance

Chromatophores are closed vesicles extracted from photosynthetic bacteria that efficiently perform the photophosphorylation reaction (ADP + Pi → ATP) under illumination. Here we show that, when entrapped inside giant lipid vesicles, they behave as nano-biophotosynthetic organellae, allowing the construction of energetically autonomous artificial protocells. As proof of concept, DNA has been transcribed within an artificial protocell, thanks to the continuous ATP photo-production from chromatophores. Such a hybrid multicompartment approach will speed up the current efforts of constructing cell-like systems of increasing complexity, allowing the implementation of several ATP-dependent processes. Developed at the interface between synthetic biology and systems chemistry, the science of artificial protocells promises unprecedented biotechnological applications, as well as unveiling still unsolved origins-of-life questions.
Herbivory and warming interact in opposing patterns of covariation between arctic shrub species at large and local scales
Authors: Post Eric , Cahoon Sean M. P. , Kerby Jeffrey T. , Pedersen Christian , Sullivan Patrick F.
Published: February 2021

Significance

Whether climatic conditions or biotic interactions determine species abundances and distributions has been a persistent question in ecology. Furthermore, its answer has long been considered scale-dependent, with climate presumably constraining abundance and distributions at large scales and species interactions determining them at local scales. We conducted a 15-y field experiment to test more recent theory that predicts abiotic conditions and biotic interactions can shape patterns of species covariation at both large and local scales. Our results affirm this prediction, offering insights that will help improve predictions of species’ distributional responses to climate change.
Kin selection explains the evolution of cooperation in the gut microbiota
Authors: Simonet Camille , McNally Luke
Published: February 2021

Significance

This is a comparative study attempting to explain the pattern of cooperation across a number of microbial species. Hamilton’s inclusive-fitness theory makes the very general prediction that increased genetic relatedness should drive the evolution of cooperation. Various arguments have dismissed the validity of this prediction in microbes, but without ever testing the broad taxonomic support for those arguments. Here, we rehabilitate the central role of relatedness by showing that its power to predict cooperative gene content holds across the full diversity of the human gut microbiota. Explaining broad-scale patterns is critical to a unifying variable for predictive science and broad applications. The manipulation of relatedness may offer an opportunity to engineering microbial communities, such as the gut microbiota.
Language left behind on social media exposes the emotional and cognitive costs of a romantic breakup
Authors: Seraj Sarah , Blackburn Kate G. , Pennebaker James W.
Published: February 2021

Significance

By analyzing language on the social media platform Reddit, we tracked people’s social, cognitive, and emotional lives as they dealt with the breakup of a close intimate relationship. Language markers can detect impending relationship breakups up to 3 mo before they occur, with continued psychological aftereffects lasting 6 mo after the breakup. Because the language shifts are also apparent in subreddits (forums) unrelated to relationships, the research points to the pervasive impact personal upheavals have across people’s social worlds. Comparable cognitive and social effects are apparent among people undergoing divorce or dealing with major life secrets. The analysis of subtle shifts in pronouns, articles, and other almost-invisible words can reveal the psychological effects of life experiences.
Data integration enables global biodiversity synthesis
Authors: Heberling J. Mason , Miller Joseph T. , Noesgaard Daniel , Weingart Scott B. , Schigel Dmitry
Published: February 2021

Significance

As anthropogenic impacts to Earth systems accelerate, biodiversity knowledge integration is urgently required to support responses to underpin a sustainable future. Consolidating information from disparate sources (e.g., community science programs, museums) and data types (e.g., environmental, biological) can connect the biological sciences across taxonomic, disciplinary, geographical, and socioeconomic boundaries. In an analysis of the research uses of the world’s largest cross-taxon biodiversity data network, we report the emerging roles of open-access data aggregation in the development of increasingly diverse, global research. These results indicate a new biodiversity science landscape centered on big data integration, informing ongoing initiatives and the strategic prioritization of biodiversity data aggregation across diverse knowledge domains, including environmental sciences and policy, evolutionary biology, conservation, and human health.
Identifying hydrophobic protein patches to inform protein interaction interfaces
Authors: Rego Nicholas B. , Xi Erte , Patel Amish J.
Published: February 2021

Significance

Hydrophobicity drives diverse aqueous assemblies, including the interactions between proteins. Conventional wisdom stipulates that the hydrophobicity of a surface must be inversely related to its polarity. By using specialized molecular simulations to characterize protein hydrophobicity, here, we challenge this notion and demonstrate that polar/charged atoms comprise a substantial fraction of hydrophobic protein patches. Moreover, hydrophobic and hydrophilic protein patches have surprisingly similar chemical compositions. We further find that the most hydrophobic protein patches also tend to mediate protein interactions. Our work thus establishes a computational framework for characterizing the hydrophobicity of complex solutes, such as proteins, and for uncovering their interaction interfaces.
Transverse spin dynamics in structured electromagnetic guided waves
Authors: Shi Peng , Du Luping , Li Congcong , Zayats Anatoly V. , Yuan Xiaocong
Published: February 2021

Significance

We formulate and experimentally validate a set of spin–momentum equations which are analogous to the Maxwell’s equations and govern spin–orbit coupling in electromagnetic guided waves. The Maxwell-like spin–momentum equations reveal the spin–momentum locking, the chiral spin texture of the field, Berry phase, and the spin–orbit interaction in the optical near field. The observed spin–momentum behavior can be extended to other classical waves, such as acoustic, fluid, gas, and gravitational waves.
Teacher language awareness and scaffolded interaction in CLIL science classrooms
Authors: Xu Daozhi , Harfitt Gary James
Published: February 2021

Teacher language awareness (TLA) constitutes the teacher’s self-reflective knowledge about the operation of
language systems in pedagogical practices. This study focuses on teachers’ understanding of learning of language and learning
through language in Content and Language Integrated Learning (CLIL) contexts, exploring how teachers proceduralise their knowledge
of language to facilitate science learning in Hong Kong. By analysing the reflective relationship between TLA and scaffolding
strategies of two teachers (students n = 31; 32) during a set of lessons in a secondary school, this paper
suggests that it is critical to re-orient the TLA focus from teachers to the act of learning and learners’ needs. This expanded
conceptual framework of TLA sheds light on how to transform teachers’ implicit knowledge of language into explicit awareness of
scaffolding in class. The TLA-filtered, scaffolded interactions can therefore promote the use of language not merely for
pedagogical purposes but also as a cognitive learning tool.
The value of introspective measures in aptitude-treatment interaction research
Authors: Sachs Rebecca , Akiyama Yuka , Nakatsukasa Kimi
Published: February 2021

To explore the value of introspective measures in aptitude-treatment interaction (ATI) research, this study
analyzed the cognitive profiles and concurrent think-alouds of six university learners of Japanese who were highly successful,
moderately successful, or unsuccessful under two computer-mediated feedback conditions in a larger (N = 80)
quantitative ATI investigation (Sachs, 2011). That study had made indirect inferences
regarding relationships among individual differences (IDs), cognitive processes, and learning on the basis of correlational
results. Using Leow’s (2015) depth-of-processing (DoP) framework as a lens, what we
found in the qualitative verbalization data highlighted that learners in the same condition with similar strengths in the IDs that
are statistically associated with performance at the group level may nonetheless engage in different cognitive processes and
achieve different learning outcomes, and vice versa. The findings also pointed toward more complex ID-DoP and ID-ID interactions
that future research could explore, such as the possibility that a weakness in memory might limit the benefits of metalinguistic
knowledge and analytic processing in a condition where group-level correlations suggest analysis is relevant to success, or that
analytic processing might enhance the value of memory in a condition where memory is relevant to success. In our conclusions, we
argue for the value of mixed-methods research in this area.
A changing landscape of voseo in
Medellín?
Authors: Restrepo-Ramos Falcon D.
Published: February 2021

This study examines the use of second-person
singular forms of address (2PS) in the linguistic landscape of Valle
de Aburrá, Colombia. Along with 58 surveys from
Paisas, over 300 photographs of public signage
with content in 2PS were taken within urban centers. Results show
that voseo has its allocated niche with a vocative
function in signs authored by the current local government of
Medellín and selected businesses. While ustedeo is
placed in regulatory signage, pronominal tú forms
are preferred for informative and commercial purposes in private and
official domains in neighboring municipalities. Public perception is
in favor of content with voseo, but governmental
ascription seems dependent upon the administration in office rather
than a steady change for all public purposes.
The Escondido swap meet
Authors: Ramos Pellicia Michelle F.
Published: February 2021

The Spanish-speaking community in North County
San Diego, a community comprised mostly of Mexicans, Mexican
Americans, and Chicanxs, but also of Guatemalans, Salvadorians, and
Nicaraguans, are using language as a tool for resistance in the
linguistic landscape of the Escondido swap meet. In this work, I
consider how linguistic practices in the landscape are strategically
used and how they compare to what it entails to be a speaker of a
language that is considered undesired and has been racialized, but
it is at the same time an asset to the local Spanish-speaking
community, as it is used to maintain their linguistic roots, and
resist linguistic oppression.
Linguistic Landscape in Otavalo
Authors: Puma Ninacuri Cristian , Narváez Daniela
Published: February 2021

This article examines the Linguistic Landscape
of Otavalo (Ecuador) where besides Spanish, Kichwa and English are
present. This city is known for its cultural diversity and its
handmade crafts market which offers a setting for the investigation
of issues related with the sociolinguistics of globalization (Blommaert, 2010; Coupland & Coupland,
2014) and processes of language commodification (Heller, Jaworski, & Thurlow,
2014). Through quantitative and qualitative data our
results show that Kichwa is seen as an identity and cultural marker
as well as a commodity, while English is indexed to modernity and
international orientation. Therefore, it is shown that social
meanings attributed to languages are dynamic indexes which can be
mobilized according to the social actors.
The act of naming in the Hispanic linguistic landscape of
Milan
Authors: Calvi Maria Vittoria
Published: February 2021

The Hispanic linguistic landscape of Milan,
which reflects the consistent presence of a Latin American
community, has been studied from the viewpoint of an emerging
multilingualism, linked to the negotiation of space, language and
identities in different multi-ethnic neighborhood. This study
explores, in particular, the act of naming, i.e. the choice of a
name for restaurants and other commercial enterprises, in which
social memories and lived experiences are involved. Different
linguistic and semiotic aspects will be considered in order to trace
the boundaries of what we might call the “Peruvian namescape”. A
qualitative-ethnographic perspective will be adopted, connecting the
analysis of some contextualized LL units, corresponding to 22
Peruvian restaurants, to what emerges from interviews with
shop-owners.