bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spicules and downflows in the solar chromosphere
Authors: Bose Souvik , Joshi Jayant , Henriques Vasco M. J. , van der Voort Luc Rouppe 
Published: January 2021

Context. High-speed downflows have been observed in the solar transition region (TR) and lower corona for many decades. Despite their abundance, it has been hard to find signatures of such downflows in the solar chromosphere.
Aims. In this work, we target an enhanced network region which shows ample occurrences of rapid spicular downflows in the Hα spectral line, which could potentially be linked to high-speed TR downflowing counterparts.
Methods. We used the k-means algorithm to classify the spectral profiles of on-disk spicules in Hα and Ca II K data observed from the Swedish 1 m Solar Telescope and employed an automated detection method based on advanced morphological image processing operations to detect such downflowing features, in conjunction with rapid blue-shifted and red-shifted excursions (RBEs and RREs).
Results. We report the existence of a new category of RREs (termed as downflowing RRE) for the first time that, contrary to earlier interpretation, are associated with chromospheric field aligned downflows moving toward the strong magnetic field regions. Statistical analysis performed on nearly 20 000 RBEs and 15 000 RREs (including the downflowing counterparts), which were detected in our 97 min long dataset, shows that the downflowing RREs are very similar to RBEs and RREs except for their oppositely directed plane-of-sky motion. Furthermore, we also find that RBEs, RREs, and downflowing RREs can be represented by a wide range of spectral profiles with varying Doppler offsets, and Hα line core widths, both along and perpendicular to the spicule axis, that causes them to be associated with multiple substructures which evolve together.
Conclusions. We speculate that these rapid plasma downflows could well be the chromospheric counterparts of the commonly observed TR downflows.
Development of in situ optical spectroscopy with high temporal resolution in an aberration-corrected transmission electron microscope
Authors: Liu Chang , Ma Chaojie , Xu Jinjing , Qiao Ruixi , Sun Huacong , Li Xiaomin , Xu Zhi , Gao Peng , Wang Enge , Liu Kaihui , Bai Xuedong 
Published: January 2021

Exploring the corresponding relation between structural and physical properties of materials at the atomic scale remains the fundamental problem in science. With the development of the aberration-corrected transmission electron microscopy (AC-TEM) and the ultrafast optical spectroscopy technique, sub-angstrom-scale spatial resolution and femtosecond-scale temporal resolution can be achieved, respectively. However, the attempt to combine both their advantages is still a great challenge. Here, we develop in situ optical spectroscopy with high temporal resolution in AC-TEM by utilizing a self-designed and manufactured TEM specimen holder, which has the capacity of sub-angstrom-scale spatial resolution and femtosecond-scale temporal resolution. The key and unique design of our apparatus is the use of the fiber bundle, which enables the delivery of focused pulse beams into TEM and collection of optical response simultaneously. The generated focused spot has a size less than 2 µm and can be scanned in plane with an area larger than 75 × 75 µm2. Most importantly, the positive group-velocity dispersion caused by glass fiber is compensated by a pair of diffraction gratings, thus resulting in the generation of pulse beams with a pulse width of about 300 fs (@ 3 mW) in TEM. The in situ experiment, observing the atomic structure of CdSe/ZnS quantum dots in AC-TEM and obtaining the photoluminescence lifetime (∼4.3 ns) in the meantime, has been realized. Further ultrafast optical spectroscopy with femtosecond-scale temporal resolution could be performed in TEM by utilizing this apparatus.
Effect of liquid depth on dynamics and collapse of large cavities generated by standing waves
Authors: Raja D. Krishna , Das S. P. 
Published: January 2021

The effect of fluid depth on the collapse of large cavities generated by over-driven axisymmetric gravity waves in a 10 cm diameter cylindrical container has been studied. At a large fluid depth in a viscous glycerine–water solution, the collapse of the cavities is inertia dominant at the initial phase with the time-dependent cavity radius (rm) obeying rm ∝ τ1/2; τ = t − t0 being the time remaining for collapse, with t0 being the time at collapse. However, enhanced damping at a low liquid depth turns the late stage of the transition into the viscous regime (rm ∝ τ) at some critical depth beyond which a singular collapse (transition from non-pinch-off and pinch-off collapse) is impossible. At a shallow depth, the change in cavity radius follows a flip of the power law, i.e., rm ∝ τ at the initial stage of collapse followed by a transition to rm ∝ τ1/2, suggesting a viscous–inertial transition. For fluids with relatively lower viscosity but similar surface tension, here water, a smoother cavity with damped parasitic waves at a small liquid depth collapses at a smaller radius. The surface jet velocity due to the collapse of the cavity monotonically decreases with the decrease in the depth, whereas in the case of water, it increases with the depth reaching a maximum at a critical depth followed by a decrease again. The self-similarity, exhibited by the cavity up to the critical depth, is lost due to the axial movement restriction by the bottom wall.
Deep-learning potential method to simulate shear viscosity of liquid aluminum at high temperature and high pressure by molecular dynamics
Authors: Cheng Yuqing , Wang Han , Wang Shuaichuang , Gao Xingyu , Li Qiong , Fang Jun , Song Hongzhou , Chu Weidong , Zhang Gongmu , Song Haifeng , Liu Haifeng 
Published: January 2021

The shear viscosity of matter and efficient simulating methods in a wide range of temperatures and densities are desirable. In this study, we present the deep-learning many-body potential (the deep potential) method to reduce the computational cost of simulations for the viscosity of liquid aluminum at high temperature and high pressure with accurate results. Viscosities for densities of 2.35 g/cm3, 2.7 g/cm3, 3.5 g/cm3, and 4.27 g/cm3 and temperatures from melting points to about 50 000 K are calculated. The results agree well with the experiment data at a pressure near 1 bar and are consistent with the simulation of first-principles at high pressure and high temperature. We reveal the behavior of the shear viscosity of liquid Al at a range where the current experimental results do not exist. Based on the available experimental data and newly generated simulation data, we propose a modified Enskog–Dymond theory, which can analytically calculate the viscosity of Al at this range. This research is helpful for numerous potential applications.
Speed breeding: a space inspired technology
Authors: Vijaya Amalraj Mohanlal , Rajendran Raj Nirmal , Ramalingasamy Ralshiya , Jayakumar Jayanthi Sneka 
Published: January 2021

Abstract
Speed breeding technology reduces the breeding cycle and fastens crop research by producing many generations within a short period of time. In this technology, plants are exposed to an extended light and reduced night time for rapid generation advancement. For instance, wheat crop can be cultivated for 2–3 generations per year under normal glass house conditions but employing speed breeding, it can be cultivated up to 6 generations per year. Speed breeding approach is inspired by NASA experiments conducted on a space mission where wheat crops were grown inside small chambers exposed to a continuous source of light. The basic principal underlying this technique is optimization of photosynthetic activity to promote rapid growth of crops, whereas the extended photoperiod with a short dark period supports functional expression of circadian clock genes. The circadian clock coordinates the biological processes with changing external environment and acts as an internal timekeeper. Under controlled environment of growth chambers, speed breeding can accelerate plant development phase which will be useful for variety development and crop research purposes including phenotyping, mutant studies and transformation. In the process of variety development, conventional breeding approaches take 7–10 years for crossing and inbreeding to develop genetically stable lines, while speed breeding takes only 2 years for crossing and inbreeding. Moreover, this technology can speed up genomic selection and can be integrated with other advanced techniques like genome editing and high throughput genotyping.
Resonance ionisation spectrometry measurement of atomic calcium Rydberg isotope shifts
Authors: Wells Stephen R , Miyabe Masabumi , Iwata Yoshihiro , Hasegawa Shuichi 
Published: January 2021

Abstract
Rydberg levels in atomic calcium are of interest due to their use in highly isotope selective multiple-step resonance ionisation spectrometry, and also for nuclear physics investigations, but gaps remain in the data for higher lying levels in calcium isotopes other than

Ca

40

. We report novel isotope shift data on four isotopes of calcium (

Ca

42

,

Ca

43

,

Ca

44

,

Ca

48

), relative to the majority abundance isotope

Ca

40

, in six Rydberg transitions for each P (n = 25–30) and F (n = 23–28) angular momentum quantum number designated series.
Dual-wavelength multilevel diffractive lenses for near-infrared imaging
Authors: Yang Gensen , Zhang Fei , Pu Mingbo , Li Xiong , Ma Xiaoliang , Guo Yinghui , Luo Xiangang 
Published: January 2021

Abstract
Optical imaging systems play an extremely important role for humans in exploring the world, but the existence of chromatic aberration greatly reduces the imaging ability. Conventional optical systems require the combination of multiple lenses to reduce chromatic aberration, but such a solution is not conducive to the miniaturization and weight reduction of the optical system. In this paper, we design dual-wavelength multilevel diffractive lenses that focus pairs of wavelengths on the same focal plane, using a modified direct-binary-search algorithm to maximize the focusing efficiency. The simulated focusing efficiencies are 72% (92%) and 79% (92%) at the wavelength of 1.064 μm and 1.55 μm, respectively, for the two-dimensional (one-dimensional) ones. Through this approach, the results presented here suggest good focusing performance at two wavelengths, providing a new opportunity for various applications in dual-wavelength imaging systems and lightweight collimators.
Transition-metal adatoms on 2D-GaAs: a route to chiral magnetic 2D materials by design
Authors: González-García A , López-Pérez W , González-Hernández R , Bacaksiz C , Šabani D , Milošević M V , Peeters F M 
Published: January 2021

Abstract
Using relativistic density-functional calculations, we examine the magneto-crystalline anisotropy and exchange properties of transition-metal atoms adsorbed on 2D-GaAs. We show that single Mn and Mo atom (Co and Os) strongly bind on 2D-GaAs, and induce local out-of-plane (in-plane) magnetic anisotropy. When a pair of TM atoms is adsorbed on 2D-GaAs in a close range from each other, magnetisation properties change (become tunable) with respect to concentrations and ordering of the adatoms. In all cases, we reveal presence of strong Dzyaloshinskii–Moriya interaction. These results indicate novel pathways towards two-dimensional chiral magnetic materials by design, tailored for desired applications in magneto-electronics.
Stress effect on segregation and ordering in Pt–Ag nanoalloys
Authors: Front Alexis , Mottet Christine 
Published: January 2021

Abstract
We performed a theoretical study of the chemical ordering and surface segregation of Pt–Ag nanoalloys in the range of size from 976 to 9879 atoms (3.12 to 6.76 nm). We used an original many-body potential able to stabilize the L11 ordered phase at equiconcentration leading to a strong silver surface segregation. Based on a recent experimental study where nanoparticles up to 2.5 nm have been characterized by high transmission electron microscopy with the L11 ordered phase in the core and a silver surface shell, we predict in our model via Monte Carlo simulations that the lower energy configuration is more complicated with a three-shell alternance of Ag/Pt/Ag from the surface surrounding the L11 ordered phase in the core. The stress analysis demonstrates that this structure softens the local stress distribution inside the nanoparticle which contributes to reduce the internal energy.
A novel solder joint diagnosis algorithm using differential geometry approach in high-density flexible integrated circuit substrates
Authors: Zeng Yong , Hu Yueming , Huang Dan 
Published: January 2021

Abstract
To provide a system with high-density solder joint 3D information acquisition and improve the comprehensive performance of automatic optical inspection systems, a novel diagnosis system for solder joints of high-density flexible integrated circuit substrates is proposed in this paper. The differential geometry principle is introduced to analyze the appearance identity of solder joints, and the diagnosis is handled as a pattern-recognition problem with the Frenet frame-matching approach. First, a high-precision 3D information-acquisition system constituted of two CCD digital cameras, each with a microscope and a three-color LED illumination, is developed. Second, a discrete estimation scheme based on the differential geometry theory is proposed to achieve curvature measurement, and then the shape of the solder joints is characterized by the crest line representation method. Finally, the classification strategy is to establish different models of solder joint types and make a decision based on a set of the predefined diagnosis rules. By inspecting various types of solder joints and comparing with other typical algorithms, the performance of the proposed system is evaluated. The experiment results indicate that the proposed algorithm has advantages of fast inspection speed, low misjudgment rate, which is reduced to 2.2%, and detailed classification.
A level set approach to simulate grain growth with an evolving population of second phase particles
Authors: Alvarado Karen , Florez Sebastian , Flipon Baptiste , Bozzolo Nathalie , Bernacki Marc 
Published: January 2021

Abstract
In numerous polycrystalline materials, grain size is controlled by second phase particles (SPPs) that hinder the grain boundaries (GBs) by pinning mechanisms. The Smith–Zener pinning (SZP) model describes the physical interaction between SPPs and GBs. Both of them can evolve when applying a heat treatment to the material. As industrial forging processes involve hot deformation steps near the solvus temperature, it is thus of prime importance to characterize the evolution of the SPPs due to their impact on the final microstructure, notably on the grain size. The level set (LS) method is classically used to describe the influence of SPPs on grain growth (GG) by considering the simulated particles as inert and represented by static holes in the used finite element (FE) mesh. A new formalism to model GG mechanism under the influence of the SZP phenomenon, able to take into account evolving particles is proposed. It involves the representation of SPPs by a LS function and a particular numerical treatment around the grain interfaces encountering SPP, making possible the modelling of SPPs evolution without altering the undergoing pinning pressure. Validation and comparison of the new method regarding previous FE-LS formulation in 2D and 3D simulations and an application on GG under the influence of dissolving particles are described.
Interfacial dislocation network in precipitation strengthened alloys during creep: a discrete dislocation dynamics (DDD) study in three dimensions
Authors: Jogi Tushar , Bhattacharya Saswata 
Published: January 2021

Abstract
Ni-base superalloys show an intricate network of dislocations around γ′ precipitates during high-temperature low-to-intermediate stress creep. With an aim to understand the formation of this interfacial dislocation network on the surfaces of unsheared, cuboidal γ′ precipitates, we perform three-dimensional discrete dislocation dynamics simulations at constant stress in a model system containing superellipsoidal inclusions. The exponents of the superellipsoid are adjusted to fit the cuboidal shape of γ′. We use a fault-energy-based back-force model to describe interactions between dislocations and structurally inhomogeneous inclusions. The model incorporates climb of edge dislocation segments on non-glissile planes through a modified dislocation mobility law for face-centred cubic crystals. Athermal repulsive intersection cross-slip is considered for the screw segments. We systematically show the evolution of dislocation network as a function of applied stress, inter-particle spacing, and ratio of glide-to-climb mobility. We scale the simulation box and the inclusions by the same factor in order to keep the volume fraction of inclusions constant in all cases. Although the dislocation density increases with the increase in applied stress as well as inter-particle spacing, the onset of steady-state in all cases is marked by a constant mobile-to-immobile dislocation density (ρ
m/ρ
im) ratio. For the range of stresses and inter-particle spacings considered in this study, the steady-state ρ
m/ρ
im remains nearly the same. Our simulations indicate a power-law behaviour where the stress exponent n ≈ 4 suggests dislocation climb to be the rate-controlling mechanism. The simulated morphological features of the dislocation network formed on the surfaces of the inclusions at steady-state (e.g., hexagonal nets due to dislocation reactions) are similar to those observed experimentally in single-crystalline superalloys crept at high temperatures and low stresses. Moreover, we obtain a relationship between length scale associated with dislocation density and applied stress.
Enforcing local equilibrium of point defects near sinks in object kinetic Monte Carlo simulations
Authors: Jourdan T 
Published: January 2021

Abstract
A model for the emission of point defects by point defect sinks is proposed for object kinetic Monte Carlo simulations. Local equilibrium of point defects in the vicinity of sinks is ensured by construction, even if elastic interactions are taken into account for the diffusion of point defects. The emission of vacancies by dislocation segments is treated in detail and validated numerically. The model is then used to simulate the annealing of a vacancy Frank loop in a system containing surfaces. Results are in overall good agreement with analytical formulas, which are based on the approximation of instantaneous equilibration of the vacancy field during the loop evolution process. For small loops the shrinkage is so rapid that this quasi-static approximation is no more valid.
Metal–insulator transition in single crystalline ZnO nanowires
Authors: Milano G , D’Ortenzi L , Bejtka K , Ciubini B , Porro S , Boarino L , Ricciardi C 
Published: January 2021

Abstract
In this work, we report on the metal–insulator transition and electronic transport properties of single crystalline ZnO nanowires synthetized by means of Chemical Vapor Deposition. After evaluating the effect of adsorbed species on transport properties, the thermally activated conduction mechanism was investigated by temperature-dependent measurements in the range 81.7–250 K revealing that the electronic transport mechanism in these nanostructures is in good agreement with the presence of two thermally activated conduction channels. More importantly, it was observed that the electrical properties of ZnO NWs can be tuned from semiconducting to metallic-like as a function of temperature with a metal-to-insulator transition (MIT) observed at a critical temperature above room temperature (T
c ∼ 365 K). Charge density and mobility were investigated by means of field effect measurements in NW field-effect transistor configuration. Results evidenced that the peculiar electronic transport properties of ZnO NWs are related to the high intrinsic n-type doping of these nanostructures that is responsible, at room temperature, of a charge carrier density that lays just below the critical concentration for the MIT. This work shows that native defects, Coulomb interactions and surface states influenced by adsorbed species can significantly influence charge transport in NWs.
Core–shell structured monodisperse carbon-rich SiO1.31C1.46H0.81 ceramic spheres as anodes for high-capacity lithium-ion batteries
Authors: Zeng Ying , He Zhiyan , Li Mingqi 
Published: January 2021

Abstract
SiOC ceramic material is a promising anode material for lithium-ion batteries. However, due to its intrinsically low electronic conductivity, it often suffers from a much lower specific capacity than the theoretical value, poor rate capability and serious potential hysteresis. In this paper, we report a core–shell structured monodisperse carbon-rich SiO1.31C1.46H0.81 submicron ceramic sphere with a free carbon content of 13.7 wt%, which is synthesized by directly annealing polysiloxane spheres derived from vinyltrimethoxysilane without adding external carbon resources. The SiO1.31C1.46H0.81 sphere has a unique microstructure, the core of which is organically assembled by large amounts of SiO1.31C1.46H0.81 primary particles of less than 20 nm and coated by a shell of 20–50 nm. As anodes for lithium-ion batteries, it presents much higher reversible capacity, initial Coulomb efficiency (ICE) and rate performance than the SiOC-based ceramic materials reported in the literature to date. At 100 mA g−1, its first reversible capacity and ICE reach ∼1107 mAh g−1 and 78.2%, respectively. At 1600 mA g−1, its stable discharge capacity is still as high as 610 mAh g−1. The excellent electrochemical performance is attributed to the moderate composition, spherical morphology and unique microstructure of the synthesized material.
Glycyrrhetinic acid remodels the tumor microenvironment and synergizes with doxorubicin for breast cancer treatment in a murine model
Authors: Tang Mingxiu , Yang Mengjia , He Kaiyong , Li Ran , Chen Xiaojie , Wang Yaowen , Zhang Xueqiong , Qiu Tong 
Published: January 2021

Abstract
We aimed to combine glycyrrhetinic acid with doxorubicin to prepare, characterize and evaluate a drug delivery nano-system with REDOX sensitivity for the treatment of breast cancer. M-DOX-GA NPs prepared by nano sedimentation were spherical, with a particle size of 181 nm. And the maximum encapsulation efficiency and drug loading in M-DOX-GA NPs were 89.28% and 18.22%, respectively. Cytotoxicity and cellular uptake experiments of nanoparticles to KC cells, Cal-27 cells and 4T1 cells were studied by the CCK-8 method. The result indicated that M-DOX-GA NPs could accurately release the drug into the tumor cells, thus achieving the targeted release of the drug. Comparing the survival rate of the above three cells, it was found that M-DOX-GA NPs had a good tumor selectivity and had a more significant therapeutic effect on breast cancer. A 4T1-bearing mouse model was established, and the tumor inhibition rate was 77.37% after injection of nanoparticle solution for 14 d. Normal tissue H&E stained sections and TUNEL assay were verified M-DOX-GA NPs have excellent tumor suppressive effect, and can efficiently reduce the toxic side effects on normal organisms, and effectively avoided 4T1 cells metastasis. Immunofluorescence detection and Western-blot analysis figured a decline in both CUGBP1 and α-SMA, which verifying the TME remodeling induced by glycyrrhetinic acid. Collectively, the combination of doxorubicin and glycyrrhetinic acid is an effective and safe strategy for remodeling fibrotic TME by improving the therapeutic outcome for breast cancer.