bluuebunny/crossref_metadata_2025 huggingface dataset:
Superheating and melting mechanisms of YBa2Cu3O7−x surfaces
Authors: Huang Simin , Chen Yuanyuan , Yao Xin , Jin Zhaohui
Published: March 2021

Recently, REBa2Cu3O7−x films were observed to possess excellent superheating performances, among which YBa2Cu3O7−x films deposited on LaAlO3 substrates could be superheated beyond the equilibrium melting point by 100 K. Although previous investigations have shown that the low surface energy of this multilayered structure is responsible for the superheating nature, micro-mechanism remains unclear. Here, based on molecular dynamics simulations, the superheating origin of YBa2Cu3O7−x was studied at the atomic scale. We found that the (001) free surface possesses strong superheating capability and exhibits a layer-by-layer melting mode with a flat melting front. Remarkably, the superheating phenomenon is attributed to the high stability of Ba–O layers, which serve as obstacles in suppressing the melting propagation. In contrast, with an absence of such significant barriers, the (100) surface displays a wavy melting front and a continuous melting process. Particularly, in that case, the highly mobile oxygen atoms facilitate the penetration of the melting liquid phase into the bulk, which further deteriorate the film thermal stability. Moreover, we proposed a modified thermodynamic model to describe the concrete melting process. The atomic simulations provide detailed evidence for understanding the microscopic origin of the melting of YBa2Cu3O7−x films and hint the way to enhance the thermal stability of functional oxides with multilayer structures.
Quantitative measure of memory loss in complex spatiotemporal systems
Authors: Kramár Miroslav , Kovalcinova Lenka , Mischaikow Konstantin , Kondic Lou
Published: March 2021

History dependence of the evolution of complex systems plays an important role in forecasting. The precision of the predictions declines as the memory of the systems is lost. We propose a simple method for assessing the rate of memory loss that can be applied to experimental data observed in any metric space X. This rate indicates how fast the future states become independent of the initial condition. Under certain regularity conditions on the invariant measure of the dynamical system, we prove that our method provides an upper bound on the mixing rate of the system. This rate can be used to infer the longest time scale on which the predictions are still meaningful. We employ our method to analyze the memory loss of a slowly sheared granular system with a small inertial number I. We show that, even if I is kept fixed, the rate of memory loss depends erratically on the shear rate. Our study suggests the presence of bifurcations at which the rate of memory loss increases with the shear rate, while it decreases away from these points. We also find that the rate of memory loss is closely related to the frequency of the sudden transitions of the force network. Moreover, the rate of memory loss is also well correlated with the loss of correlation of shear stress measured at the system scale. Thus, we have established a direct link between the evolution of force networks and the macroscopic properties of the considered system.
Photoluminescence excitation spectroscopy for structural and electronic characterization of resonant tunneling diodes for THz applications
Authors: Cito M. , Kojima O. , Stevens B. J. , Mukai T. , Hogg R. A.
Published: March 2021

Photoluminescence excitation spectroscopy (PLE) and high-resolution x-ray diffraction (HR-XRD) are used to characterize the structural and electronic properties of high current density InGaAs/AlAs/InP resonant tunneling diode wafer structures. The non-destructive assessment of these structures is challenging, with several unknowns: well and barrier thickness, the well indium molar fraction, and band-offsets, which are a function of strain, material, growth sequence, etc. The low temperature PL spectra are deconvoluted through simulation and are shown to include contributions from type I (e1–hh1) and type II (conduction band–hh1) transitions that are broadened due to interface fluctuations on a range of length scales. PLE data are obtained by a careful choice of the detection wavelength, allowing the identification of the e2hh2 transition that is critical in determining the band-offsets. An agreement between the HR-XRD data, the PL, and the PLE data is only obtained for a given conduction band offset of 58.8%. This scheme, combining HR-XRD, PL, and PLE, consequently provides crucial electronic and structural information non-destructively.
Nitrogen-induced ultralow power switching in flexible ZnO-based memristor for artificial synaptic learning
Authors: Lin Ya , Liu Jilin , Shi Jiajuan , Zeng Tao , Shan Xuanyu , Wang Zhongqiang , Zhao Xiaoning , Xu Haiyang , Liu Yichun
Published: March 2021

An energy-efficient memristive synapse is highly desired for the development of brain-like neurosynaptic chips. In this work, a ZnO-based memristive synapse with ultralow-power consumption was achieved by simple N-doping. The introduction of N atoms, as the acceptor, reduces the carrier concentration and greatly increases the resistance of the ZnO film. The low energy consumption, which is as low as 60 fJ per synaptic event, can be achieved in our device. Essential synaptic learning functions have been demonstrated, including excitatory postsynaptic current, paired-pulse facilitation, and experience-dependent learning behaviors. Furthermore, the device can still exhibit the synaptic performance in the bent state or even after 100 bending cycles. Our memristive synapse is not only promising for energy-efficient neuromorphic computing systems but also suitable for the development of wearable neuromorphic electronics.
The onset of instabilities and finite amplitude waves in a model of aluminum reduction cells with nonuniform cathode current
Authors: Molokov S. , Pedcenko A. , Chahine R. , Chailly N.
Published: March 2021

In aluminum reduction cells, the electric current density at the cathode is seldom uniform. This may be due to a variety of reasons. One of the reasons is that a mass of undissolved alumina may get enrobed by the cryolitic bath, and this mix freezes due to the decrease in temperature below the liquidus point. Thus, an electrically resistive solid layer (“mud”) is formed at a part of the cathode. This leads to horizontal electric currents in the liquid aluminum layer, and their magnetohydrodynamic (MHD) interaction with the vertical magnetic field induces a rotating flow of aluminum. This may cause undesirable MHD instabilities. A quasi-two-dimensional model for the laboratory facility has been presented. The results show that the dominating feature of the flow is a depression of the free surface of the liquid metal above the mud spot. This is due to strong rotation of the liquid metal around the mud spot, which causes the centrifugal force. Other effects may include superimposed conventional MHD instability, which manifests itself in a rotating interface, modulated waves, reflection of the waves from the corners of the domain, sloshing, etc. It has been shown that small mud spots do not affect the cell stability, while the large ones may cause such deep depressions that the centrifugal force completely removes the liquid metal above the spot.
Filling a hole by capillary flow of liquid metal–equilibria and instabilities
Authors: Yu Cheng-Nien , Lazaridis Konstantinos , Wu Yangyang , Voroshilov Evgeniy , Krivilyov Mikhail D. , Mesarovic Sinisa Dj. , Sekulic Dusan P.
Published: March 2021

The importance of the problem of hole-filling by a molten metal lies in the application of brazing for repairs in space, under microgravity conditions. The negligible effects of gravity and dominance of capillary forces can be approximated under terrestrial conditions, provided that the hole and the quantity of liquid are small, as quantified by the Bond number. In this paper, we report experimental results, modeling, and analysis of the hole-filling problem using the liquid aluminum brazing alloy on aluminum substrate. Depending on the hole size, the capillary driven flow may result in the hole being either filled or not filled. The equilibrium problem (energy minimization) has multiple solutions in some regions of the parameter space. Therefore, the experimental outcomes may depend on the availability of sufficiently strong perturbation, required to dislodge the system from a metastable equilibrium. We report good agreement between experimental results and theoretical/computational predictions. In general, a deeper and narrower hole favors the filled outcome.
Reservoir computing with swarms
Authors: Lymburn Thomas , Algar Shannon D. , Small Michael , Jüngling Thomas
Published: March 2021

We study swarms as dynamical systems for reservoir computing (RC). By example of a modified Reynolds boids model, the specific symmetries and dynamical properties of a swarm are explored with respect to a nonlinear time-series prediction task. Specifically, we seek to extract meaningful information about a predator-like driving signal from the swarm’s response to that signal. We find that the naïve implementation of a swarm for computation is very inefficient, as permutation symmetry of the individual agents reduces the computational capacity. To circumvent this, we distinguish between the computational substrate of the swarm and a separate observation layer, in which the swarm’s response is measured for use in the task. We demonstrate the implementation of a radial basis-localized observation layer for this task. The behavior of the swarm is characterized by order parameters and measures of consistency and related to the performance of the swarm as a reservoir. The relationship between RC performance and swarm behavior demonstrates that optimal computational properties are obtained near a phase transition regime.
High-fidelity ghost diffraction and transmission in free space through scattering media
Authors: Xiao Yin , Zhou Lina , Chen Wen
Published: March 2021

We report a different class of ghosts, called ghost diffraction and transmission with compressed spectrum coefficients, for ghost (e.g., analog-signal) transmission in free space through scattering media using a single-pixel detector. The ghost, e.g., analog signal, is first transformed to its spectral domain, such as Hadamard domain. The generated Hadamard spectrum coefficients can be flexibly compressed in order to reduce the number of random patterns to be illuminated and transmitted in free space, and the selected Hadamard spectrum coefficients are sequentially encoded into random amplitude-only patterns as information carriers. In the experiments, high-quality Hadamard spectrum transmission using a coherent light source is realized in different scattering environments, and, subsequently, high-fidelity ghosts are further retrieved from the received Hadamard spectrum coefficients. Experimental results demonstrate that the proposed method possesses high robustness against wave diffraction, multi-layer scattering, and noise. This class of ghosts provides a different insight about quantum and classical optics for analog-signal transmission in free space, and an avenue toward many applications, e.g., quantum ghost transmission and communication, could be opened up.
Cluster formation and non-metal-to-metal transition in a diamond-shaped graphene-like lattice
Authors: Bittencourt Rafael A. , da Silva Costa G. , da Cunha Lima A. T. , da Cunha Lima I. C.
Published: March 2021

This work is a numerical simulation of the bond percolation in an array of junctions and bifurcations mimicking a section of a graphene slab. We calculate the size distribution of graphene clusters as a filler of a polymer aiming to obtain the percolation threshold. We obtained the sigmoidal distribution of graphene clusters as a function of concentration of persistent conducting bonds creating these clusters. The probability density of this distribution shows a universal complementary Fermi–Dirac behavior as a signature of a topological response. Using a tight-binding model for the transmission from the source to the drain, we obtain a smooth transition from an insulator to a conductor through a dirty metal as the concentration of conductive bonds increases for small arrays. As the array size increases, the simulation shows a sharp non-metal-to-metal transition from a pure polymer into a pristine suspended graphene layer.
Two-photon absorption line shapes in the transit-time limit
Authors: Lehmann Kevin K.
Published: March 2021

A weak excitation transit-time resolution limited analytic line shape is derived for a Doppler broadening-free degenerate two-photon transition from a standing wave with a TEM00 transverse profile. This approximation is appropriate when the collisional mean free path is much larger than the transverse width of the TEM00 beam. It is considerably simpler than the two-photon absorption line shape previously published, Bordé, C. R. Hebd. Seances Acad. Sci., Ser. B 282, 341–344 (1976), which was derived for more general experimental conditions. The case of a saturating field, with an intensity-dependent shift of the resonance frequency, is treated and expressed in reduced units. Numerical calculations are presented for the line shape for a range of the reduced intensity and light intensity shifts values.
An imaging refractometer for density fluctuation measurements in high energy density plasmas
Authors: Hare J. D. , Burdiak G. C. , Merlini S. , Chittenden J. P. , Clayson T. , Crilly A. J. , Halliday J. W. D. , Russell D. R. , Smith R. A. , Stuart N. , Suttle L. G. , Lebedev S. V.
Published: March 2021

We report on a recently developed laser-probing diagnostic, which allows direct measurements of ray-deflection angles in one axis while retaining imaging capabilities in the other axis. This allows us to measure the spectrum of angular deflections from a laser beam, which passes through a turbulent high-energy-density plasma. This spectrum contains information about the density fluctuations within the plasma, which deflect the probing laser over a range of angles. We create synthetic diagnostics using ray-tracing to compare this new diagnostic with standard shadowgraphy and schlieren imaging approaches, which demonstrates the enhanced sensitivity of this new diagnostic over standard techniques. We present experimental data from turbulence behind a reverse shock in a plasma and demonstrate that this technique can measure angular deflections between 0.06 and 34 mrad, corresponding to a dynamic range of over 500.
Modeling oil–water separation with controlled wetting properties
Authors: Gavazzoni Cristina , Silvestrini Marion , Brito Carolina
Published: March 2021

Several oil–water separation techniques have been proposed to improve the capacity of cleaning water. With the technological possibility of producing materials with antagonist wetting behavior, for example, a substrate that repels water and absorbs oil, the understanding of the properties that control this selective capacity has increased with the goal of being used as the mechanism to separate mixed liquids. Besides the experimental advance in this field, less is known from the theoretical side. In this work, we propose a theoretical model to predict the wetting properties of a given substrate and introduce simulations with a four-spin cellular Potts model to study its efficiency in separating water from oil. Our results show that the efficiency of the substrates depends both on the interaction between the liquids and on the wetting behavior of the substrates itself. The water behavior of the droplet composed of both liquids is roughly controlled by the hydrophobicity of the substrate. Predicting the oil behavior, however, is more complex because the substrate being oleophilic does not guarantee that the total amount of oil present on the droplet will be absorbed by the substrate. For both types of substrates considered in this work, pillared and porous with a reservoir, there is always an amount of reminiscent oil on the droplet, which is not absorbed by the substrate due to the interaction with the water and the gas. Both theoretical and numerical models can be easily modified to analyze other types of substrates and liquids.
Research on photosensitive gate ferroelectric integrated GaN HEMT photodetector
Authors: Zhu Yanxu , Li Qixuan , Yang Zhuang , Wang Cai , Wei Zhao
Published: March 2021

In this paper, we take advantage of the high sensitivity of two-dimensional electron gas concentration in the heterojunction channel of a GaN high electron mobility transistor (HEMT) to device surface states and gate voltages. By integrating a HEMT with ferroelectric materials with photovoltaic effects, a photo-sensitive gate HEMT photodetector based on ferroelectric integration is obtained. By exploring the ferroelectric and composite film sputtering growth epitaxial atmosphere, a high-performance PZT/ZnO composite ferroelectric film grown in an oxygen-containing atmosphere is obtained. Comparing the PZT and LiNbO3 (LN) ferroelectric thin films prepared with or without the buffer layer, the following conclusions are obtained. The quantum efficiency of the PZT/ZnO film increases by 240% and 596% at the peak of 300–400 nm, reaching 14.55%; the residual polarization of the PZT film obtained in an oxygen-containing atmosphere reaches 52.31 μC/cm2; the PZT/ZnO composite film has better fatigue characteristics. The GaN HEMT detector prepared by using magnetron sputtered PZT/ZnO as the sensing gate under the oxygen atmosphere has a photocurrent increment of 11.51 mA under ultraviolet light and a responsivity of 111A/W at 365 nm. At the same time, the device has τr = 0.12 s and τf = 8.3 s transient response. The research in this paper shows that a new structure photodetector based on a GaN HEMT has excellent ultraviolet light response, which provides a new research direction for the light detection mechanism.
Persistence of hydrodynamic envelope solitons: Detection and rogue wave occurrence
Authors: Slunyaev Alexey
Published: March 2021

The observation of a wave group persisting for more than 200 periods in the direct numerical simulation of nonlinear unidirectional irregular water waves in deep water is discussed. The simulation conditions are characterized by parameters realistic for broad-banded waves in the sea. Through solution of the associated scattering problem for the nonlinear Schrödinger equation, the group is identified as the intense envelope soliton with remarkably stable parameters. Most of the extreme waves occur on top of this group, resulting in higher and longer rogue wave events.
An experimental study of two identical air bubbles rising side-by-side in water
Authors: Agrawal Meenu , Gaurav Ashish , Karri Badarinath , Sahu Kirti Chandra
Published: March 2021

We experimentally study the dynamics of two identical air bubbles rising side-by-side in water by varying two parameters, namely, the radius of the bubble and center to center distance between them. The bubbles follow a three-dimensional spiraling motion, and their path and shape oscillations are observed in both the front and top views by using a high speed camera with a back-lit illumination and a mirror arrangement. Bubbles of different sizes are created by using a dumping cup mechanism, and the center to center distance between the two bubbles is varied by using telescopic joints. The dynamics of the two side-by-side bubbles is compared and contrasted with that of a single rising bubble. We found that the bubbles act independent of each other, like a single bubble, when the center to center distance is greater than seven times the radius of the bubbles. For similar separation distances, increasing the size of the bubbles results in a smaller terminal velocity and also lesser deviation from a spiral path due to high inertia.
A novel dataset to identify the endemic herpetofauna of the New Caledonia biodiversity hotspot with DNA barcodes
Authors: Bernstein Justin M. , Jackman Todd R. , Sadlier Ross A. , Wang Yun-yu , Bauer Aaron M.
Published: March 2021

New Caledonia is the smallest global biodiversity hotspot, yet has one of the highest levels of endemism for an insular region of its size. Lizards are the dominant vertebrate fauna, and, while ecologically important, can be difficult to identify and many are in decline due to anthropogenic threats. As an aid to facilitate identification, we generated a near-complete DNA barcode dataset for New Caledonian lizards, consisting of 601 mitochondrial CO1 sequences of 100 of the 107 described lizards, and a number of yet undescribed species. We use this dataset to assess the performance of CO1 in delimiting species recognised by other, more extensive data and in recovering phylogenetic signal. Most species had intraspecific genetic distances ≤3.7%. Most comparisons between described species were at least ~5% divergent, with the exception of three pairwise species comparisons showing interspecific distances > 2.5%. Maximum likelihood CO1 trees of the six most speciose genera recovered each as monophyletic and, although discordant with previously published ND2 trees using quantitative topology tests, showed similar patterns of intraspecific and interspecific divergence, supporting the utility of CO1 in taxonomic identification and species delimitation. Some species showed overlap between intra- and interspecific pairwise distances, suggesting cryptic taxa, a finding also supported by species delimitation analyses using GMYC and mPTP. This dataset not only provides the basis for economical and reliable identification of New Caledonian lizards encountered during biodiversity assessments, but also provides a potential tool for investigating the identity of native lizards and their ecosystem interactions, even from partial remains.
Cytokine receptor clustering in sensory neurons with an engineered cytokine fusion protein triggers unique pain resolution pathways
Authors: Prado Judith , Westerink Remco H. S. , Popov-Celeketic Jelena , Steen-Louws Cristine , Pandit Aridaman , Versteeg Sabine , van de Worp Wouter , Kanters Deon H. A. J. , Reedquist Kris A. , Koenderman Leo , Hack C. Erik , Eijkelkamp Niels
Published: March 2021

Significance

Interactions between the immune system and nervous system regulate chronic pain. Cytokines are well-known immune-regulatory molecules that have activities beyond regulation of the immune system, including regulation of pain pathways. We identified that fusion of regulatory cytokines interleukin (IL)-4 and IL-10 into the fusion protein IL4–10 FP provides unexpected properties to inhibit pain by clustering the respective receptor chains of both cytokines in sensory neurons. IL4–10 FP promotes unique signaling pathways and gene-expression profiles that resolve chronic inflammatory pain. Thus IL4–10 FP is an immune biologic that effectively inhibits pain by activating pain-resolution pathways in sensory neurons through clustering of cytokine receptors. This unique effect discriminates IL4–10 FP from a combination therapy with individual regulatory cytokines.
A bird-like genome from a frog: Mechanisms of genome size reduction in the ornate burrowing frog,
Platyplectrum ornatum
Authors: Lamichhaney Sangeet , Catullo Renee , Keogh J. Scott , Clulow Simon , Edwards Scott V. , Ezaz Tariq
Published: March 2021

Significance

The mechanisms by which genomes become smaller in lineages with large genomes, such as many frogs, are poorly understood. Here, we present the sequence of a very small genome from a frog—that of the ornate burrowing frog,
Platyplectrum ornatum
, whose genome is smaller than that of many birds, a group well known for small genomes. Our data show that this frog evolved molecular mechanisms to keep in check a major process characterizing large genomes: namely, proliferation of transposable elements. We also present basic data on gene expression and sex determination in this emerging model for genome miniaturization.
Primary differentiated respiratory epithelial cells respond to apical measles virus infection by shedding multinucleated giant cells
Authors: Lin Wen-Hsuan W. , Tsay Annie J. , Lalime Erin N. , Pekosz Andrew , Griffin Diane E.
Published: March 2021

Significance

Measles virus (MeV) is highly infectious by the respiratory route, but respiratory epithelial cells are thought to be resistant to infection through the exposed apical surface and to require infection through the basolateral surface. We show that differentiated respiratory epithelial cells are actually highly susceptible to apical infection and that infection leads to formation of multinucleated giant cells that are shed from the epithelial sheet into the lumen leaving the epithelium intact and devoid of infected cells. These results are consistent with the hypothesis that MeV infection is initiated in respiratory epithelial cells with subsequent infection of lymphoid tissue and systemic spread.
Ancient noeggerathialean reveals the seed plant sister group diversified alongside the primary seed plant radiation
Authors: Wang Jun , Hilton Jason , Pfefferkorn Hermann W. , Wang Shijun , Zhang Yi , Bek Jiri , Pšenička Josef , Seyfullah Leyla J. , Dilcher David
Published: March 2021

Significance

There were two heterosporous lignophyte lineages of which only one, the seed plants, survived the Permian–Triassic mass extinction. Based on exceptionally complete fossil trees from a 300-My-old volcanic ash, the enigmatic Noeggerathiales are now recognized as belonging to the other lineage. They diversified alongside the primary seed plant radiation and constitute seed plants’ closest relatives. Noeggerathiales are reconstructed as members of a plexus of free-sporing woody plants called progymnosperms, extending their age range by 60 My. Following the origin of seed plants, progymnosperms were previously thought to have become gradually less abundant before dying out in Carboniferous. We show they diversified and evolved complex morphologies including cone-like structures from modified leaves before going extinct at the Permian–Triassic extinction.
The intracellular environment affects protein–protein interactions
Authors: Speer Shannon L. , Zheng Wenwen , Jiang Xin , Chu I-Te , Guseman Alex J. , Liu Maili , Pielak Gary J. , Li Conggang
Published: March 2021

Significance

Protein–protein interactions are essential for proper cellular function. Macromolecular crowding can influence these interactions via two phenomena: hard-core repulsions and soft (chemical) interactions. Simple theory predicts that hard-core repulsions are stabilizing, and stabilization increases with increased crowding, while chemical interactions can be stabilizing or destabilizing. We investigated the effect of the cellular environment on a model protein–protein interaction in a prokaryote (
Escherichia coli
) and a eukaryote (
Xenopus laevis
oocytes). The observation that the complex is more stable in the eukaryote, even though it is less crowded, highlights the key role played by chemical interactions under physiologically relevant conditions.
Involvement of cytotoxic Eomes-expressing CD4
+
T cells in secondary progressive multiple sclerosis
Authors: Raveney Ben J. E. , Sato Wakiro , Takewaki Daiki , Zhang Chenyang , Kanazawa Tomomi , Lin Youwei , Okamoto Tomoko , Araki Manabu , Kimura Yukio , Sato Noriko , Sano Terunori , Saito Yuko , Oki Shinji , Yamamura Takashi
Published: March 2021

Significance

Multiple sclerosis (MS) can transition from a relapsing-remitting form (RRMS) into a chronic progressive form (secondary progressive MS, SPMS). SPMS pathogenesis remains poorly understood with diagnosis based entirely on retrospective clinical monitoring. We show that T helper cells expressing the transcription factor Eomes (Eomes
+
Th cells) were significantly increased in peripheral blood from SPMS patients versus healthy subjects or RRMS and other progressive MS patients. Moreover, Eomes
+
Th cells expressing granzyme B were found infiltrating brain tissues in SPMS autopsy samples, providing support for a pathogenic role. Analysis of clinical status on follow-up indicated the value of measuring Eomes
+
Th cells for SPMS diagnosis and prognostic monitoring. This study may contribute to future development of biomarker-assisted “precision medicine” for MS.
Kinetic analysis reveals that independent nucleation events determine the progression of polyglutamine aggregation in
C. elegans
Authors: Sinnige Tessa , Meisl Georg , Michaels Thomas C. T. , Vendruscolo Michele , Knowles Tuomas P. J. , Morimoto Richard I.
Published: March 2021

Significance

Diseases associated with amyloid formation affect millions of people worldwide. Great progress has been made to understand the process of amyloid formation in test tube reactions, but it has so far remained unclear if the same biophysical principles also dominate in living cells and organisms. Here, we use the nematode
C. elegans
to demonstrate that we can apply kinetic modeling approaches to quantitatively analyze the process of protein aggregation in a living animal. The mathematical models that we develop are not restricted to this system and are applicable to other disease-associated proteins and animal models. The ability to quantitatively understand aggregation mechanisms in living organisms will be critical to advance our understanding of human disease and to design therapeutic strategies.
Historic Yangtze flooding of 2020 tied to extreme Indian Ocean conditions
Authors: Zhou Zhen-Qiang , Xie Shang-Ping , Zhang Renhe
Published: March 2021

Significance

Summer rainfall along the Yangtze River in 2020 was the heaviest since 1961, with devastating socioeconomic impacts. While official forecasts based on tropical Pacific state failed, we show that dynamic models, when initialized with ocean observations globally, succeed in predicting the extreme rainfall. Slowly propagating oceanic Rossby waves in the South Indian Ocean are the source of predictability, which are in turn tied to the record-breaking Indian Ocean Dipole in late 2019. The identification of antecedent subsurface conditions of the Indian Ocean as a key predictor represents an important conceptual advance in Asian summer monsoon dynamics, helping improve disaster preparation that saves lives and properties.
Photoinduced hole hopping through tryptophans in proteins
Authors: Záliš Stanislav , Heyda Jan , Šebesta Filip , Winkler Jay R. , Gray Harry B. , Vlček Antonín
Published: March 2021

Significance

Electron (hole) hopping through tryptophan residues activates protein cofactors, participates in cellular photosignaling, and protects enzymes from oxidative degradation. The energetics of excited chromophores, together with their positions relative to proximal indoles, are evolution-optimized in natural photolyases and cryptochromes. Our theoretical analysis of photoinduced hole hopping through tryptophans in rhenium-modified blue copper proteins has shed light on the roles of electronic coupling and adiabaticity, as well as electrostatic-field fluctuations and solvation dynamics in driving charge transport rapidly over long distances. The take-home message is that attention should be paid to solvation of redox-active molecules in hopping chains in the design of bioinspired light-harvesting systems and functional photocatalysts.
Closed-orbit theory for the photodetachment rate in a static magnetic field transversely superimposed to an oscillatory electric field
Authors: Chen X J , Titimbo K , Du M L
Published: March 2021

The closed-orbit theory is used for the study of the photodetachment rate of electrons from single-charged anions in presence of a homogeneous magnetic field that is perpendicular to a time-dependent electric field. The photodetachment process in the near-threshold region is achieved by a weak laser field. We describe in detail the semiclassical method to derive the general formula for the instant photodetachment rate in time-dependent systems. We find that the photodetachment rate is affected by the presence of the static magnetic field since, within the semiclassical picture, it contributes to fold back the electron trajectories back to their emission position: generating closed orbits. For weak magnetic fields, however, the number of closed orbits does not change, then the modulation of the photodetachment rate is virtually unaffected when it is compared to the case with no magnetic field. On the contrary, the modulation is clearly distinctive and complicated for strong magnetic field intensities due to the contribution of a larger number of closed orbits. Despite we provide general formulas, numerical experiments and discussions are focused on the emission of electrons as s-waves and p

z
-waves.
Physical and chemical properties of a magnetic-assisted DC superimposed nanosecond-pulsed streamer discharge plasma
Authors: Jiang Nan , Lu Xiaoling , Peng Bangfa , Li Jie , Shang Kefeng , Lu Na , Wu Yan
Published: March 2021

In the present work, a magnetic-assisted DC superimposed nanosecond-pulsed streamer discharge (DC-NPSD) with a 0.4 T parallel magnetic field is developed that achieves good performance for ozone production and toluene degradation. The influence of the assisted parallel magnetic field on the electrical characteristics, streamer propagation behavior, reactive species generation and plasma chemical properties of the DC-NPSD are systematically investigated. The experimental results indicate that better impedance matching of a nanosecond pulsed power supply and a discharge reactor can be realized by superimposing DC voltage (U
DC), which facilitates reactive species production and toluene degradation. The discharge current, input energy and reactive species production can be further enhanced by the application of a parallel magnetic field under different pulse and DC voltage conditions. There are two distinct streamer phases in the DC-NPSD: a primary streamer (PS) with longer propagation distance and higher propagation velocity and a secondary streamer (SS) with shorter propagation distance and lower propagation velocity. The propagation velocities of both the PS and the SS increase with increasing U
DC. Only PS propagation velocity is accelerated by a parallel magnetic field; however, that of the SS remains almost constant with or without a magnetic field. Both ozone generation and toluene degradation performance are improved by a magnetic field, which is attributed to the lengthened electron motion path under the action of Lorentz force and the constraint effect on energetic electrons in the presence of a parallel magnetic field.
Direct excitation of the magnetisation in photon-magnon hybrid systems with an infrared laser pulse
Authors: Braggio Caterina , Carugno Giovanni , Crescini Nicolò , Di Vora Raffaele , Ortolan Antonello , Ruoso Giuseppe
Published: March 2021

We present experimental results concerning the direct excitation of the magnetisation in a photon-magnon hybrid system composed of a microwave cavity and an embedded yttrium iron garnet (YIG) sphere. An 11 ps ultrafast pulsed laser, with wavelength of 1064 nm outside the YIG transparence window, directly excite the magnon modes. We measure the energy deposited in the Kittel mode of magnetisation by exploiting its coupling to the TE102 mode of the rectangular microwave cavity in the strong coupling regime. Energy collection is performed by a standard rf detection chain reading an antenna matched to the cavity resonance. This technique can prove to be essential in the study of the dynamics of cavity magnon-polaritons, finding application in dark matter axion searches and future magnon based quantum information studies.
Defect-engineered three-dimensional vanadium diselenide microflowers/nanosheets on carbon cloth by chemical vapor deposition for high-performance hydrogen evolution reaction
Authors: Miao Chengcheng , Zhang Ting , Li Fulin , Zhang Lei , Sun Jiamin , Liu Dong , Wu Liqian , Wang Hang , Chen Fenghua , He Longbing , Han Ning , Ma Yandong , Dai Ying , Yang Zai-xing
Published: March 2021

In the past decades, defect engineering has become an effective strategy to significantly improve the hydrogen evolution reaction (HER) efficiency of electrocatalysts. In this work, a facile chemical vapor deposition (CVD) method is firstly adopted to demonstrate defect engineering in high-efficiency HER electrocatalysts of vanadium diselenide nanostructures. For practical applications, the conductive substrate of carbon cloth (CC) is selected as the growth substrate. By using a four-time CVD method, uniform three-dimensional microflowers with defect-rich small nanosheets on the surface are prepared directly on the CC substrate, displaying a stable HER performance with a low Tafel slope value of 125 mV dec−1 and low overpotential voltage of 295 mV at a current density of 10 mA cm−2 in alkaline electrolyte. Based on the results of x-ray photoelectron spectra and density functional theory calculations, the impressive HER performance originates from the Se vacancy-related active sites of small nanosheets, while the microflower/nanosheet homoepitaxy structure facilitates the carrier flow between the active sites and conductive substrate. All the results present a new route to achieve defect engineering using the facile CVD technique, and pave a novel way to prepare high-activity layered electrocatalysts directly on a conductive substrate.
Novel single-step synthesis and shape transformation of Au/CuO micro/nanocomposites using plasma-liquid interaction
Authors: Boruah Palash Jyoti , Khanikar Rakesh Ruchel , Bailung H
Published: March 2021

We report a novel single-step synthesis method of metal/metal oxide composites and transformation of the shape of the oxide material by Plasma-Liquid Interaction. Considering the potential applications of noble metal nanoparticle decorated copper oxide composites, we synthesize Au/CuO micro/nanocomposites by generating plasma between two copper electrodes inside a gold precursor (HAuCl4) solution. Simultaneous synthesis of CuO and Au nanoparticles from the electrode material and from the precursor solution respectively is possible due to the interaction of energetic electrons and other active species formed in the plasma zone. Moreover, the process does not require any external stabilizing and reducing chemical agents. The method provides a remarkable tunability of the materials’ physical and chemical properties by only controlling the precursor solution concentration. By controlling process parameters, the shape of CuO particles can be transformed from spindles to sheet-like and the size of Au nanoparticles can also be varied. It influences the particles’ specific surface area and total pore volume. Plasmonic property of Au nanoparticles is also observed i.e. optical tunability can be achieved. The process is found to be effective for synthesis of desired nanomaterials having various energy storage and solar light-driven photocatalytic applications.
NaYF4:Yb/Tm@SiO2-Dox/Cur-CS/OSA nanoparticles with pH and photon responses
Authors: Qi Xiaoling , Han Yingdong , Liu Shujing , Hu Haofeng , Cheng Zhenzhou , Liu Tiegen
Published: March 2021

Stimulus-triggered drug delivery systems (DDSs) based on lanthanide-doped upconversion nanoparticles (UCNPs) have attracted significant attention for treating cancers due to their merits of high drug availability, precisely controlled drug release, and low side-effects. However, such DDSs usually exhibit a single stimulus-response, which may limit the efficiency of cancer treatment. To extend response types in a single DDS, we construct NaYF4:Yb/Tm@SiO2-doxorubicin (Dox)/curcumin (Cur)-chitosan (CS)/2-Octen-1-ylsuccinic anhydride (OSA) nanoparticles with core-shell structures. Our method is based on the exploration of the synergistic effect of UCNPs and multiple drugs. In particular, the NaYF4:Yb/Tm is used to convert near-infrared light to visible light, activating Cur photosensitizers to produce singlet oxygen for photodynamic therapy, while CS/OSA responds to a low pH environment to release cancer drugs, including Dox and Cur for chemotherapy through breaking a free carboxyl group. The results show that the UCNPs with a 40 nm diameter, 23 nm thick mesoporous SiO2, and 19/1 mol% Yb3+/Tm3+concentrations could continuously release Dox and Cur at a pH value of 6.5 within 6 h after the excitation of a 980 nm-wavelength CW laser. Our study provides a promising approach for developing efficient DDSs for cancer treatment.
Normally-off AlGaN/GaN high electron mobility transistors on Si substrate with selective barrier regrowth in ohmic regions
Authors: Jiang Weihong , Tang Haipeng , Bardwell Jennifer A
Published: March 2021

In this paper, we report the fabrication of a normally-off AlGaN/GaN high electron mobility transistor (HEMT) using an ultra-thin AlGaN barrier layer structure on Si (111) substrate. Additional AlGaN layers were selectively regrown only on the ohmic contact areas. The fabricated device exhibits a positive threshold voltage of 0.3 V, a maximum drain output current of 753 mA mm−1 at gate voltage of +4 V, and low gate leakage of 1.2 × 10−7 A mm−1. The selective area growth method shows a promising way to achieve normally-off GaN based HEMTs with very good performance.
Minimal length, Berry phase and spin-orbit interactions
Authors: Aghababaei S , Moradpour H , Rezaei G , Khorshidian S
Published: March 2021

Bearing the perturbation method in mind, and by focusing on the first order of approximation, the effect of Generalized Uncertainty Principle (GUP) on the Berry phase is investigated. Thereinafter, we apply the obtained formulation to quantum ring including two sorts of spin-orbit interactions, namely Rashba and Dresselhaus interactions, which are accessible for electrons. Finally, a comparison between the results and the accuracy of Berry phase detectors helps us in finding out β
0 < 1046 and β
0 < 1051 as the upper bounds on the GUP parameter inflicted by the Rashba and Dresselhaus interactions, respectively.
Tight focusing of the centrosymmetric shape of hybrid polarized beams by adjustable multi-vortex phases
Authors: Ji Kailai , Qin Yali , Liu Xiaoxu , Zheng Huan , Ren Hongliang , Hu Yingtian
Published: March 2021

We propose an approach for achieving various centrosymmetric shapes by employing hybrid polarized Bessel–Gaussian (HPBG) beams with multi-vortex phases, which are obtained by embedding a few first-order off-axis topological charges into vortices separated by equal arc lengths of a circle. According to the Debye–Wolf electromagnetic diffraction formula (which is routinely used to describe focusing by high numerical aperture optical systems), we investigate the evolution of tightly focused intensity profiles of the HPBG beams with multi-vortex phases (which are the vectorial electric field of radial and azimuthal polarization), by tuning the positional vectors of the embedded vortex phases, the number of vortex phases and the ratio of radial to azimuthal polarization of the hybrid polarization. The simulation results show that the number of vortex phases is equal to the number of vertices of hollow polygons, increasing the magnitude of polar vector leads to deformation of the hollow polygons, and that the ratio of the radial and azimuthal polarization magnitudes affects the edge sharpness of the hollow polygon in the focal plane, respectively. We can produce triangles, squares, pentagons, hexagons, and inner crosses in the central hollow region, and outer crosses, embedded stars and snowflakes by manipulating the numbers and sites of multi-vortex phase singularities. The focusing structures are robust to noise and maintain a limited thickness along the optical axis. These specific intensity profiles are significant for potential applications including the trapping of multiple micro-sized particles, nonlinear optics, optical beam shaping, and optical telecommunication applications.
Rescattering mechanism of weak decays of double-charm baryons *
Authors: Han Jia-Jie , Jiang Hua-Yu , Liu Wei , Xiao Zhen-Jun , Yu Fu-Sheng
Published: March 2021

The doubly charmed baryon

was recently observed by LHCb via the decay processes of

and

. These discovery channels were successfully predicted in a framework in which the short-distance contributions are calculated under the factorization hypothesis and the long-distance contributions are estimated using the rescattering mechanism for the final-state-interaction effects. In this paper, we illustrate the above framework in detail by systematic studies on the two-body baryonic decays

involving the doubly charmed baryons

, the singly charmed baryons

and the light pseudoscalar mesons

.
Towards semantic fMRI neurofeedback: navigating among mental states using real-time representational similarity analysis
Authors: Russo Andrea G , Lührs Michael , Di Salle Francesco , Esposito Fabrizio , Goebel Rainer
Published: March 2021

Objective. Real-time functional magnetic resonance imaging neurofeedback (rt-fMRI-NF) is a non-invasive MRI procedure allowing examined participants to learn to self-regulate brain activity by performing mental tasks. A novel two-step rt-fMRI-NF procedure is proposed whereby the feedback display is updated in real-time based on high-level representations of experimental stimuli (e.g. objects to imagine) via real-time representational similarity analysis of multi-voxel patterns of brain activity. Approach. In a localizer session, the stimuli become associated with anchored points on a two-dimensional representational space where distances approximate between-pattern (dis)similarities. In the NF session, participants modulate their brain response, displayed as a movable point, to engage in a specific neural representation. The developed method pipeline is verified in a proof-of-concept rt-fMRI-NF study at 7 T involving a single healthy participant imagining concrete objects. Based on this data and artificial data sets with similar (simulated) spatio-temporal structure and variable (injected) signal and noise, the dependence on noise is systematically assessed. Main results. The participant in the proof-of-concept study exhibited robust activation patterns in the localizer session and managed to control the neural representation of a stimulus towards the selected target in the NF session. The offline analyses validated the rt-fMRI-NF results, showing that the rapid convergence to the target representation is noise-dependent. Significance. Our proof-of-concept study introduces a new NF method allowing the participant to navigate among different mental states. Compared to traditional NF designs (e.g. using a thermometer display to set the level of the neural signal), the proposed approach provides content-specific feedback to the participant and extra degrees of freedom to the experimenter enabling real-time control of the neural activity towards a target brain state without suggesting a specific mental strategy to the subject.
Thermal behavior of small magnets
Authors: Herron Lukas , Dixit Purushottam
Published: March 2021

While the canonical ensemble has been tremendously successful in capturing statistical properties of large systems, deviations from canonical behavior exhibited by small systems are not well understood. Here, using a two-dimensional small Ising magnet embedded inside a larger heat bath, we characterize the failures of the canonical ensemble when describing small systems. We find significant deviations from the canonical behavior for small systems near and below the critical point. Notably, the agreement with the canonical ensemble is driven not by the system size but by the decoupling between the system and its surrounding. A superstatistical framework wherein we allow the temperature of the small magnet to vary is able to capture the statistics of the small magnet with significantly higher accuracy than the Gibbs–Boltzmann distribution. We discuss implications for experiments and future directions.