bluuebunny/crossref_metadata_2025 huggingface dataset:
Persistence properties of a Camassa–Holm type equation with (
n + 1)-order non-linearities
Authors: Freire Igor Leite
Published: January 2022

Lower order conservation laws and symmetries of a family of hyperbolic equations having the Camassa–Holm equation as a particular member are obtained. We show that the equation has two conservation laws with zeroth order characteristics and that its symmetries are generated by translations in the independent variables and a certain scaling, as well as some invariant solutions are studied. Next, we consider persistence and asymptotic properties for the solutions of the equation considered. In particular, we analyze the behavior of the solutions of the equation for large values of the spatial variable. We show that if the initial data has a certain asymptotic exponential decaying, then such a property persists for any time as long as the solution exists. Moreover, depending on the behavior of the initial data for large values of the spatial variable and if for some further time the solution shares the same behavior, then it necessarily vanishes identically. Finally, we prove unique continuation results for the solutions of the equation.
Atomically dispersed cobalt anchored on N-doped graphene aerogels for efficient electromagnetic wave absorption with an ultralow filler ratio
Authors: Xu Jia , Liu Minjie , Zhang Xinci , Li Bei , Zhang Xiao , Zhang Xiaoli , Zhu Chunling , Chen Yujin
Published: January 2022

The widespread application of high-frequency electronic and communication devices has caused increasingly severe electromagnetic pollution. It is highly desirable but challenging to develop ultralight electromagnetic wave (EMW) absorbers with strong absorption performance to eliminate the negative effects of electromagnetic pollution. Herein, a secondary ion adsorption and defect-anchoring strategy was proposed to construct ultralight N-doped graphene aerogels containing isolated single cobalt atoms (Co-SAs/GAs) with a tunable content of Co-SAs from 1.13 to 2.58 wt. %. The optimal Co-SAs/GAs with a matching thickness of 1.5 mm and an ultralow filler ratio of 5 wt. % attenuated about 99.999% electromagnetic energy and exhibited specific EMW absorption performance (SMAP) of 37 220 dB cm2 g−1, which was 15 000 dB cm2 g−1 higher than that of the best reported absorber in literature. Permittivity and electrical conductivity measurements indicated that the introduction of Co-SAs significantly increased the conduction and polarization losses of the GAs, which was confirmed by simulation results based on the Havriliak–Negami equation. Theoretical calculations demonstrated that the Co–N4 moiety exhibited obvious polarization behavior, which could be further tuned by defective sites in its vicinity. This comprehensive investigation of the relationships between single-atom structure and electromagnetic wave absorption property provides an efficient route toward the rational design of ultralight absorbers with metal single-atoms.
Influences of serrated trailing edge on the aerodynamic and aeroacoustic performance of a flapping wing during hovering flight
Authors: Ji Xueyu , Wang Li , Ravi Sridhar , Tian Fang-Bao , Young John , Lai Joseph C. S.
Published: January 2022

The influences of serrated trailing edge on the aerodynamic and aeroacoustic performance of a flapping wing during hovering flight are investigated using a hybrid framework of an immersed boundary Navier–Stokes solver for the flow field and the Ffowcs Williams–Hawkings (FW–H) analogy for the sound field. A rigid rectangular wing with an aspect ratio of 2 undergoes pitching and stroke motions at a Reynolds number (Re) of 310 and a Mach number (M) of 0.012. Simulations are conducted by varying the dimensionless wavenumber k* from 2π to 10π and wave amplitude 2h* from 0.25 to 1.0. We find that at k*=8π and 2h*=1.5 (D4), the average sound power level is reduced by up to 6.8 dB within the Strouhal number (St) between 2.0 and 4.0 compared to that of a plain trailing edge while the lift coefficient is maintained. The directivity at St = 0.2, St = 0.4, St = 2.2, and St = 2.4 is discussed. It is found that the serrations of D4 do not affect the directivity for the first two frequencies and significantly reduce the magnitude of the directivity for the last two frequencies. The serrations of D4 considerably alter the flow field near the wing surface and reduced the surface pressure fluctuations near the wing tip, leading to the noise reduction. The lift coefficient of D4 is not significantly changed, because the reduction in the pressure-contributed lift is compensated by an increase in the shear stress-contributed lift. The serrations with higher 2h* and k* have larger shear stress-contributed lift.
Two surface multipactor discharge with two-frequency rf fields and space-charge effects
Authors: Iqbal Asif , Verboncoeur John , Zhang Peng
Published: January 2022

This paper presents two-surface multipactor discharge with two-frequency rf fields using Monte Carlo simulations and Computer Simulation Technology (CST) Particle Studio. The effects of the relative strength and phase of the second carrier mode on multipactor susceptibility and time dependent physics are studied. Compared to single-frequency rf operation, shrinkage of multipactor susceptibility regions is observed for different configurations of two-frequency rf operation. The presence of a second carrier mode in the rf field results in mixed multipactor modes in which electrons take a fixed time period to complete a round trip between the two surfaces, while the time for electrons to traverse the gap in each direction is found to be different. CST simulation reveals that the space-charge effect reduces the electron growth rate and causes shrinkage of multipactor susceptibility bands.
Cancellation method to improve signal to noise ratio of an electrodeless microwave-biased ZnO single crystal x-ray detector
Authors: Zhao Xiaolong , Ye Ming , Cao Zhi , Huang Danyang , Fan Tingting , He Yongning
Published: January 2022

Semiconductor x-ray detectors are usually fabricated with proper ohmic or Schottky contact electrodes, which make the fabrication process complex and even unable to realize, especially for new materials. In this paper, we demonstrated an electrodeless ZnO single crystal x-ray detector using microwave (MW) bias with a high signal-to-noise ratio obtained by a cancellation method. The MW-biased x-ray detector is fabricated using the split-ring-resonator with the ZnO crystal mounted on the split-ring gap. The analytical response model was built for the detector. The MW cancellation process was realized by a phase and amplitude matching network. By using the cancellation method, the signal-to-noise ratio of the detector is about 59.4 dB, which is 58 dB higher than that of the DC-biased ZnO photodetector. The sensitivity of the detector is 139 µC Gy−1 cm−2 for the x-ray dose rate of 3.54 Gy/s, which is 86 times higher than that of the DC-biased ZnO photodetector. The high sensitivity of the detector is due to the high equivalent stimulated voltage caused by the split-ring resonator. The MW-biased detector can be used for x-ray dose monitoring.
Electronic structure of epitaxially grown and regrown GaN pn junctions characterized by scanning Kelvin probe and capacitance microscopy
Authors: Kim Tae-Hyeon , Fu Kai , Yang Chen , Zhao Yuji , Yu Edward T.
Published: January 2022

Epitaxial regrowth of GaN pn junctions is a key technology for realization of a variety of high-performance GaN power electronic devices. However, the regrowth process can introduce impurities and defects that degrade a device’s performance. Here, we show that scanning Kelvin probe force microscopy and scanning capacitance microscopy can be used in a cross-sectional geometry to probe dopant distributions and an electronic structure in epitaxially grown GaN pn junctions. These measurements enable profiling of potential and dopant distributions across GaN pn junctions produced by uninterrupted epitaxial growth and by regrowth on an etched surface. Clear differences are observed in comparisons to the electronic structure of these two types of junctions that can be correlated with results of complementary characterization of dopant distributions reported for similarly grown structures. These measurements also suggest the presence of defects in etch-and-regrow pn junction structures that extend nearly 1 μm below the regrown interface.
Viscous shaping of the compliant cell nucleus
Authors: Dickinson Richard B. , Katiyar Aditya , Dubell Christina R. , Lele Tanmay P.
Published: January 2022

The cell nucleus is commonly considered to be a stiff organelle that mechanically resists changes in shape, and this resistance is thought to limit the ability of cells to migrate through pores or spread on surfaces. Generation of stresses on the cell nucleus during migration and nuclear response to these stresses is fundamental to cell migration and mechano-transduction. In this Perspective, we discuss our previous experimental and computational evidence that supports a dynamic model, in which the soft nucleus is irreversibly shaped by viscous stresses generated by the motion of cell boundaries and transmitted through the intervening cytoskeletal network. While the nucleus is commonly modeled as a stiff elastic body, we review how nuclear shape changes on the timescale of migration can be explained by simple geometric constraints of constant nuclear volume and constant surface area of the nuclear lamina. Because the lamina surface area is in excess of that of a sphere of the same volume, these constraints permit dynamic transitions between a wide range of shapes during spreading and migration. The excess surface area allows the nuclear shape changes to mirror those of the cell with little mechanical resistance. Thus, the nucleus can be easily shaped by the moving cell boundaries over a wide range of shape changes and only becomes stiff to more extreme deformations that would require the lamina to stretch or the volume to compress. This model explains how nuclei can easily flatten on surfaces during cell spreading or elongate as cells move through pores until the lamina smooths out and becomes tense.
Ga-ion beam surface modification of glass using a custom-built liquid metal ion beam
Authors: Cha Byeong Jun , Byeon Woo Jun , Choi Chang Min , Min Boo Ki , Cho Jinwan , Baek Ji Young , Kim Young Dok , Choi Myoung Choul
Published: January 2022

The application of a Ga-liquid metal ion beam (Ga-LMIB) for surface modification is reported. Ga-LMIB treatment on the glass surface resulted in the implantation of Ga ions and the formation of sub-micrometer mounds. The glass surface hydrophobicity was also found to be enhanced as a result of the Ga-LMIB treatment; additionally, a photocatalytic activity that promoted organic dye decomposition was observed. Ga-LMIB application can be considered to be a new surface modification strategy for the construction of locally hydrophobic and photocatalytic surfaces.
Influence of substrate stress on in-plane and out-of-plane ferroelectric properties of PZT films
Authors: Aruchamy Naveen , Schenk Tony , Girod Stephanie , Glinsek Sebastjan , Defay Emmanuel , Granzow Torsten
Published: January 2022

Solution-deposited ferroelectric films often are under mechanical stress due to the difference in thermal expansion coefficients between films and substrate materials. Knowledge of how stress changes the ferroelectric response under different actuation conditions is essential when selecting a substrate for film deposition. Here, a comparative study of the ferroelectric properties of lead zirconate titanate thin films on transparent fused silica glass and sapphire substrates is presented. Sapphire exerts a compressive in-plane stress on the film, favoring an out-of-plane domain orientation, while fused silica causes tensile in-plane stress and a predominantly in-plane domain configuration. As expected, the out-of-plane polarization is high under in-plane compressive stress but reduced by a factor of nearly 4 by in-plane tensile stress. In contrast, the in-plane polarization shows an unexpectedly weak stress dependence. It is larger by only about 10% under tensile stress compared to compressive stress. Permittivity increases when the major domain orientation does not coincide with the electric field. The observations are explained based on a model taking into account the crystallographic structure of the film.
Multi-dimensional control of femtosecond laser filaments by inserting a wedge plate in the forced focusing region
Authors: Wang Jianji , Guo Yajun , Song Xiaowei , Guo Kaimin , Lin Jingquan
Published: January 2022

Modulating the length and position of plasma filament is desired for many filament-based applications. We proposed a novel method to manipulate the properties of filament along the propagation direction by introducing asymmetric focusing with a wedge plate in the forced focusing region. By simply varying the inclination degree of a wedge and the distance between the wedge and lens, a plasma filament can break into two sub-filaments along the propagation direction, and the separation between sub-filaments can be controlled. The experiment results are in agreement with the results of simulation by the ray-tracing method. Furthermore, the effect of the wedge angle and rotation angle on the control of the filament is studied. It is found that the separation of the sub-filaments and the azimuth angle of the filament around the original optical axis can be controlled by the wedge angle and rotation angle of the wedge, respectively. When combined with a phase plate, the control method also shows the ability to modulate the multi-filament array with wavefront modification. Our research provides a simple and flexible method for 3-D control of femtosecond laser filaments for practical applications.
Size-dependent enhancement of passive microwave rectification in magnetic tunnel junctions with perpendicular magnetic anisotropy
Authors: Sidi El Valli A. , Iurchuk V. , Lezier G. , Bendjeddou I. , Lebrun R. , Lamard N. , Litvinenko A. , Langer J. , Wrona J. , Vila L. , Sousa R. , Prejbeanu I. L. , Dieny B. , Ebels U.
Published: January 2022

Spintronic rf detectors are efficient nanoscale counterparts to conventional semiconductor-based components for energy harvesting and wireless communication at low input power. Here, we report on the optimization of the rectified output dc voltage using magnetic tunnel junctions (MTJs) with strong perpendicular anisotropy of both the polarizing and free layers. The magnetization of the polarizing layer is fixed out-of-plane, while the free layer thickness is adjusted so that its magnetization orientation changes from in-plane to out-of-plane. Rectification dc output voltages in the mV range are obtained for moderate rf source powers with a signal-to-noise ratio of 26–39 dB for Prf = −25 dBm and a sensitivity ε of 300 mV/mW. The rectified signal shows a strong dependence on MTJ dimensions: it increases by a factor of 5–6 when reducing the diameter from 180 to 50 nm. Furthermore, this enhancement can be doubled when reducing the free layer thickness from 1.8 to 1.6 nm. This size-related enhancement is attributed to several jointly acting effects: the amplitude of the spin transfer torque that depends inversely on the diameter, the effective anisotropy that depends on the thickness of the excited layer, and the tunneling magneto-resistance ratio that for the devices studied here depends on diameter. The obtained results indicate that the geometry of the MTJ can be used to design spintronic based rf detectors with optimized sensitivity.
Parametric excitation of a gravity–capillary wave by radiation pressure of ultrasound
Authors: Krutyansky L. , Preobrazhensky V. , Brysev A. , Pernod P. , Klopotov R.
Published: January 2022

Parametric instability of a standing gravity–capillary wave is observed in conditions of irradiation of a surface of a liquid by a plane ultrasound beam modulated by amplitude. A threshold value of ultrasound intensity for excitation of the parametric oscillations of the surface is determined, and the frequency response of the process is measured. A mechanism of instability based on sound radiation pressure applied to a liquid surface curved with menisci is suggested.
Ferromagnetic resonance and magnetization switching characteristics of perpendicular magnetic tunnel junctions with synthetic antiferromagnetic free layers
Authors: Lyu Deyuan , Zhang Delin , Gopman Daniel B. , Lv Yang , Benally Onri J. , Wang Jian-Ping
Published: January 2022

Perpendicular magnetic tunnel junctions (pMTJs) with synthetic antiferromagnetic (SAF) free layers have attracted much interest for applications on spintronic memory devices with ultrafast speed and ultralow energy. In this work, SAF free layer pMTJs (SAF-pMTJs) were designed and fabricated, in which a Ru/Ta bilayer spacer is used to form the SAF structure. We first characterized the magnetization dynamics of the SAF free layer by using ferromagnetic resonance and found that the Gilbert damping constant of the SAF free layer is around 0.019. Then, in device level studies that span from 900 nm down to 200 nm lateral size, we observed a transition of the SAF free layer from a preferred antiparallel to parallel magnetic configuration at small device sizes, which can be explained by the increased dipole interaction. The impact of the operating current was also investigated. We report an extraordinarily strong dependence, up to 144.1 kOe per A/μm2, of the offset field on the applied current, suggesting an electric-field modulation on the interlayer exchange coupling of the SAF free layer. These results will be instructive to improve the understanding of material properties and device performance of SAF-pMTJs for ultrafast, ultralow-power consumption spintronic devices.
Contactless electrostatic shaping of a capillary jet for drop-on-demand purposes
Authors: Lalloz Samy , Davoust Laurent
Published: January 2022

The contactless electrostatic shaping of a capillary jet can be adjusted so as to generate a monodisperse spray in the jetting regime. To demonstrate this, an actuator based on stacked electrodes is developed to generate a spatially modulated electric stress. The latter promotes the parametric excitation of a wavelength along a deformed capillary jet. The objective is to better control the breakup length of the capillary jet and to phase lock drop ejection. Experiments are carried out based on light absorption and fast imaging. The breakup length and the drop size distribution are measured. The comparison with a stability model allows us to identify resonant frequencies which monitor the size or the number density of drops. The concept of synchronization frequencies is introduced here with possible use in future developments of electrodynamic actuators.
Analytical solutions of hydroelastic interactions between waves and submerged open-net fish cage modeled as a porous cylindrical thin shell
Authors: Ma Mingyuan , Zhang Hong , Jeng Dong-Sheng , Wang Chien Ming
Published: January 2022

In this paper, a new semi-analytical solution is proposed to describe the interactions between ocean waves and a flexible cylindrical net cage that is submerged at different depths below the mean water level. The flexible net is treated as a thin perforated shell, and its deformation is governed by the membrane vibration equation of cylindrical shells. The small-amplitude wave theory is adopted to simulate the wavefield, while the flow passing through the cage is described by the porous medium theory. The numerical results exhibit significant wave responses of the net cage, including the distribution properties of wave surfaces, dynamic pressure drops on the net interface, and net structure displacements. Furthermore, the influences of several important design parameters on the hydrodynamic action imposed on the net cage are revealed by parametric studies. The present studies conclude that the significant wave impact is mainly concentrated on the free water surface, and increasing the porosity and flexibility of the net can alleviate wave scattering and the hydrodynamic actions. In addition, at specific wave frequencies, the horizontal wave force acting on the cage will vanish. These findings should be useful to engineers who are designing offshore fish cage systems.
Miniaturization of dielectric ceramic-based metamaterial perfect absorber
Authors: Luo Weijia , Wang Xubin , Wang Shun , Wang Xueqian , Liu Zetan , Li Lingxia , Hu Fan , Wen Yongzheng , Zhou Ji
Published: January 2022

Currently, due to the low resonance absorption of each dielectric ceramic block with a finite dielectric constant, the period of dielectric ceramic-based metamaterials for microwave or terahertz perfect absorbers is always large, which cannot meet the miniaturization requirements. Here, we introduce another absorption loss dimension, conductivity loss, by nano-carbon powders through the carburizing process to ameliorate these metamaterial absorbers; the mechanism based on electromagnetic simulation is also sufficiently demonstrated. Then, we establish a carburizing channel in the Ba4Sm9.33Ti18O54 ceramics with an appropriate dielectric constant (<80) for verification, and the microwave absorbance can be double improved. Correspondingly, the period is only 1/2 that of the pure ceramic-based one. Furthermore, this approach is considered to be extended into various metamaterials using dielectric resonance, proposing an effective strategy for device miniaturization, and the restrictive relationship between device size and dielectric constant is expected to be broken.
Observations of rotating ferrofluid drop in a time-varying magnetic field
Authors: Shih Jyun-Chen , Chu Hong-Yu
Published: January 2022

We report the stretch–shrink–rotation motion of a ferrofluid drop in a time-varying magnetic field along the x direction. The drop performs stretch and shrink motion at low magnetic field due to the balance of magnetic force and surface tension as observed in previous investigations, but it exhibits rotating motion at high magnetic field. The growth rate of rotating angle for the drop stretched to the maximum length is characterized. We find that the size of elongated drop shows transitions at Rayleigh frequency of drop and at the frequency with maximum growth rate. The phase diagram of growth rate to the frequency and the strength of applied magnetic field reveals the threshold for drop to rotate. It is suspected that the induced transverse magnetization for the magnetic torque is associated with the phase lag between the time-varying magnetic field and the deformation of drop which leads to the rotation of drop. Drop rotating along the y and z axis shows the evidence of transverse magnetization induced by the magnetic field in the x axis.
Portable, handheld, and affordable blood perfusion imager for screening of subsurface cancer in resource-limited settings
Authors: Bhowmik Arka , Ghosh Biswajoy , Pal Mousumi , Paul Ranjan Rashmi , Chatterjee Jyotirmoy , Chakraborty Suman
Published: January 2022

Significance

Existing procedures of screening subsurface cancers are either prohibitively resource-intensive and expensive or are unable to provide direct quantitative estimates of the relevant physiological parameters for accurate classification accommodating interpatient variabilities and overlapping clinical manifestations. Here, we introduce a handheld and inexpensive blood perfusion imager that provides a noninvasive in situ screening approach for distinguishing precancer, cancer, and normal scenarios by precise quantitative estimation of the localized blood circulation in the tissue over an unrestricted region of interest without any unwarranted noise in the data, augmented by machine learning–based classification. Clinical trials in minimally resourced settings have established the efficacy of the method in differentiating cancerous and precancerous stages of suspected oral abnormalities, as verified by gold-standard biopsy reports.
The effectiveness of nudging: A meta-analysis of choice architecture interventions across behavioral domains
Authors: Mertens Stephanie , Herberz Mario , Hahnel Ulf J. J. , Brosch Tobias
Published: January 2022

Significance

Changing individuals’ behavior is key to tackling some of today’s most pressing societal challenges such as the COVID-19 pandemic or climate change. Choice architecture interventions aim to nudge people toward personally and socially desirable behavior through the design of choice environments. Although increasingly popular, little is known about the overall effectiveness of choice architecture interventions and the conditions under which they facilitate behavior change. Here we quantitatively review over a decade of research, showing that choice architecture interventions successfully promote behavior change across key behavioral domains, populations, and locations. Our findings offer insights into the effects of choice architecture and provide guidelines for behaviorally informed policy making.
Physical mechanisms of ESCRT-III–driven cell division
Authors: Harker-Kirschneck Lena , Hafner Anne E. , Yao Tina , Vanhille-Campos Christian , Jiang Xiuyun , Pulschen Andre , Hurtig Fredrik , Hryniuk Dawid , Culley Siân , Henriques Ricardo , Baum Buzz , Šarić Anđela
Published: January 2022

Significance

Cell division is an essential requirement for life. Division requires mechanical forces, often exerted by protein assemblies from the cell interior, that split a single cell into two. Using coarse-grained computer simulations and live cell imaging we define a distinct cell division mechanism—based on the forces generated by the supercoiling of an elastic filament as it disassembles. Our analysis suggests that such a mechanism could explain ESCRT-III–dependent division in
Sulfolobus
cells, based on the similarity of the dynamics of division obtained in simulations to those observed using live cell imaging. In this way our study furthers our understanding of the physical mechanisms used to reshape cells across evolution and identifies additional design principles for a minimal division machinery.
Association of improved air quality with lower dementia risk in older women
Authors: Wang Xinhui , Younan Diana , Millstein Joshua , Petkus Andrew J. , Garcia Erika , Beavers Daniel P. , Espeland Mark A. , Chui Helena C. , Resnick Susan M. , Gatz Margaret , Kaufman Joel D. , Wellenius Gregory A. , Whitsel Eric A. , Manson JoAnn E. , Rapp Stephen R. , Chen Jiu-Chiuan
Published: January 2022

Significance

Epidemiological studies have demonstrated that improved air quality may improve respiratory health and reduce mortality. Increasing data support late-life exposure to air pollution as a modifiable risk factor for dementia, but whether improved ambient air quality translates to lower dementia risk is unclear. In this study on a geographically diverse cohort of US community-dwelling older women, we found that long-term improvement in ambient air quality in late life was associated with reduced dementia risk. The associations did not significantly differ by age, education, geographic region, Apolipoprotein E e4 genotypes, or cardiovascular risk factors. These findings strengthen the causal association between late-life exposure to air pollution and dementia risk.
Slow expanders invade by forming dented fronts in microbial colonies
Authors: Lee Hyunseok , Gore Jeff , Korolev Kirill S.
Published: January 2022

Significance

Living organisms never cease to evolve, so there is a significant interest in predicting and controlling evolution in all branches of life sciences. The most basic question is whether a trait should increase or decrease in a given environment. The answer seems to be trivial for traits such as the growth rate in a bioreactor or the expansion rate of a tumor. Yet, it has been suggested that such traits can decrease, rather than increase, during evolution. Here, we report a mutant that outcompeted the ancestor despite having a slower expansion velocity when in isolation. To explain this observation, we developed and validated a theory that describes spatial competition between organisms with different expansion rates and arbitrary competitive interactions.
BRD9 regulates interferon-stimulated genes during macrophage activation via cooperation with BET protein BRD4
Authors: Ahmed Nasiha S. , Gatchalian Jovylyn , Ho Josephine , Burns Mannix J. , Hah Nasun , Wei Zong , Downes Michael , Evans Ronald M. , Hargreaves Diana C.
Published: January 2022

Significance

Macrophages regulate many aspects of the innate immune response and the activation of adaptive immunity following exposure to microbial ligands. However, macrophages can also contribute to inflammation underlying diseases such as atherosclerosis and obesity. Epigenetic regulators control inflammatory gene regulation and, as such, are potential targets for modulation of the inflammatory response. Here, we show that inhibitors and degraders of the bromodomain protein BRD9, a subunit of the noncanonical BAF complex, limit inflammation by specifically blocking the induction of interferon-stimulated genes. This effect overlaps with the transcriptional responses with the BET inhibitor JQ1 but affects fewer genes and is more specific in scope. Our results suggest that BRD9 inhibitors/degraders may be therapeutically relevant agents to limit interferon-associated inflammation.
Trophic interactions with heterotrophic bacteria limit the range of
Prochlorococcus
Authors: Follett Christopher L. , Dutkiewicz Stephanie , Ribalet François , Zakem Emily , Caron David , Armbrust E. Virginia , Follows Michael J.
Published: January 2022

Significance

Prochlorococcus
is the smallest and most abundant photosynthetic organism on Earth and is thought to be confined to low-latitude regions by its requirement for warm waters. Latitudinal transects in the North Pacific, however, demonstrate that the poleward decrease of this species occurs across a wide range of temperatures. An additional mechanism is likely required. We use theory, computational models, and additional observational data to suggest that the poleward decrease is caused by an ecological interaction: a shared predator which consumes both
Prochlorococcus
and similar-sized heterotrophic bacteria. Understanding the fate of this organism requires a knowledge of the interconnected ecosystem of other organisms, where both direct and indirect interactions control community structure.
Inverting the structure–property map of truss metamaterials by deep learning
Authors: Bastek Jan-Hendrik , Kumar Siddhant , Telgen Bastian , Glaesener Raphaël N. , Kochmann Dennis M.
Published: January 2022

Significance

More than a decade of research has been devoted to leveraging the rich mechanical playground of periodically assembled truss metamaterials. The enormous design space of manufacturable unit cells, however, has made the inverse design a challenge: How does one efficiently identify a complex truss that has given target properties? We answer this question by a data-driven method, which instantly (once trained, within milliseconds) generates not one but a variety of truss unit cells, whose effective response closely matches a given (fully anisotropic) stiffness tensor. Moreover, our framework to smoothly transition between different unit cells enables the design of lightweight structures with spatially varying, locally optimized properties, for applications from wave guiding to artificial bone.
Enhanced spin accumulation in nano-pillar-based lateral spin valve using spin reservoir effect
Authors: Cui Xiaomin , Hu Shaojie , Kimura Takashi
Published: January 2022

Lateral spin valves are ideal nanostructures for investigating spin-transport physics phenomena and promoting the development of future spintronic devices owing to dissipation-less pure spin current. The magnitude of the spin accumulation signal is well understood as a barometer for characterizing spin current devices. Here, we develop a novel fabrication method for lateral spin valves based on ferromagnetic nanopillar structures using a multi-angle deposition technique. We demonstrate that the spin-accumulation signal is effectively enhanced by reducing the lateral dimension of the nonmagnetic spin channel. The obtained results can be quantitatively explained by the confinement of the spin reservoir by considering spin diffusion into the leads. The temperature dependence of the spin accumulation signal and the influence of the thermal spin injection under a high bias current are also discussed.
Study on bandgap and directional wave propagation of a two-dimensional lattice with a nested core
Authors: Hou Jiahong , Zhang Zhijun , Li Dong
Published: January 2022

This paper proposes a two-dimensional lattice structure with a nested core. The bandgap distribution and the anisotropy of the phase velocity and group velocity were studied based on Bloch’s theorem and the finite element method. The effects of the eccentric ratio (e) and the rotation angle (

θ

) of the dual-phase structure on the bandgap distribution were investigated, and the anisotropy was studied via phase velocity and group velocity. The structure of e = 0.3 displayed the maximum total bandgap width. As

θ

increased, the total bandgap widths of structures of different e all obviously increased and the low-frequency bandgap properties were improved. The phase velocity and group velocity of e = 0 displayed strong anisotropy, and the anisotropy was adjusted by tuning

θ

. Furthermore, the group velocity of the eighth mode displayed high-directional wave propagation. For practical applications, a single-phase structure was proposed and analyzed. Through additive manufacturing technology, the single-phase structure was prepared and tested by a low amplitude test setup. The experimental results displayed good agreement with the numerical results, which demonstrated high directional propagation. This finding may pave the way for practical applications of the proposed lattice metamaterial in terms of wave filtering.
Epitaxial growth and room-temperature ferromagnetism of quasi-2D layered Cr4Te5 thin film
Authors: Wang Jing , Wang Weiyuan , Fan Jiyu , Zheng Huan , Liu Hao , Ma Chunlan , Zhang Lei , Tong Wei , Ling Langsheng , Zhu Yan , Yang Hao
Published: January 2022

Large-scale growth of two-dimensional (2D) ferromagnetic thin films will provide an ideal platform for studying 2D magnetism and active spintronic devices. However, controllable growth of 2D ferromagnets over large areas faces tremendous challenges. Herein, we report a large-area growth of 2D ferromagnetic single-crystal thin films Cr4Te5 on Al2O3 (0001) substrates using pulsed laser deposition. X-ray diffraction patterns and atomic force microscopy detection confirm that all thin films have high quality epitaxy together with being atom-level smooth. Magnetic measurements show the persistence of ferromagnetic ordering state to above room temperature, with a Curie temperature ∼320 K, atomic magnetic moment ∼0.307

μ

B

/Cr, and the easy-magnetization axis in the film plane. Comparing with bulk Cr4Te5 single-crystal, the critical exponent β = 0.491 indicates that the magnetic interactions of the thin film obey the mean-field model rather than the 3D Heisenberg model. This work will open an avenue for growing large-scale 2D ferromagnets and developing room temperature 2D magnet-based nanodevices.
On chain models for contact electrification
Authors: Hasbun Javier E , Lew Yan Voon Lok C , Willatzen Morten
Published: January 2022

An exact analytical model of charge dynamics for a chain of atoms with asymmetric hopping terms is presented. Analytic and numeric results are shown to give rise to similar dynamics in both the absence and presence of electron interactions. The chain model is further extended to the case of two atoms per cell (a perfect alloy system). This extension is further applied to contact electrification between two different atomic chains and the effect of increasing the magnitude of the contact transfer matrix element is studied.
Astigmatism correction of convex aspheres using the subaperture stitching hindle test
Authors: Kim Goeun , Song In-Ung , Kihm Hagyong , Yang Ho-Soon
Published: January 2022

We propose an astigmatism correction method for the subaperture stitching Hindle test to measure hyperbolic convex aspheres. Astigmatic wavefront errors arise from misaligned Hindle setups, mechanical runout errors of the rotational motion for stitching, and the surface error of the target itself. Because these errors are combined, they cannot be separated in the conventional subaperture stitching Hindle tests. We exploited the rotational periodicity of each error to distinguish the surface figure error from other astigmatic error sources and rectified the Hindle test results with a third-order astigmatism. Using the subaperture stitching Hindle test, we averaged two sets of measurement data with a 180° rotational phase difference between them to calculate the astigmatic surface error. The proposed method was verified experimentally by comparing it with the results from a commercial stitching interferometer from QED Technologies; only subnanometer differences in the root-mean-square values were obtained. Therefore, the proposed method calibrated the system errors from the test surface wedge and the rotational decenter easily, thereby reducing the mechanical costs and alignment efforts and making it more accessible than a sophisticated mechanism.
Fabrication of 3D hierarchical Fe2O3/SnO2 photoanode for enhanced photoelectrochemical performance
Authors: Zhang Xing , Chen Hao , Zhang Wei , Zhang Lina , Liu Xinyu , Ma Jinwen , Xu Shichong , Li Haibo
Published: January 2022

Exploring and fabricating a suitable photoanode with high catalytic activity is critical for enhancing photoelectrochemical (PEC) performance. Herein, a novel 3D hierarchical Fe2O3/SnO2 photoanode was fabricated by a hydrothermal route, combining with an annealing process. The morphology, crystal structure were studied by scanning electron microscopy, transmission electron microscopy, x-ray photon spectroscopy, and x-ray diffraction, respectively. The results reveal the successful preparation of Fe2O3 nanothorns on the surface of SnO2 nanosheets. The as-fabricated 3D Fe2O3/SnO2 photoanode yields obviously promoted PEC performance with a photocurrent density of approximate 5.85 mA cm−2, measured in a mixture of Na2S (0.25 M) and Na2SO3 (0.35 M) aqueous solution at 1.23 V (versus reversible hydrogen electrode, RHE). This value of photocurrent is about 53 times higher than that of the bare SnO2 photoanode. The obvious improved PEC properties can be attributed to the 3D Fe2O3/SnO2 heterostructures that offer outstanding light harvesting ability as well as improved charge transport and separation. These results suggest that exploring a suitable 3D hierarchical photoanode is an effective approach to boost PEC performance.
Low-resistivity Pd nanopatterns created by a direct electron beam irradiation process free of post-treatment steps
Authors: Salvador-Porroche Alba , Herrer Lucía , Sangiao Soraya , de Teresa José María , Cea Pilar
Published: January 2022

The ability to create metallic patterned nanostructures with excellent control of size, shape and spatial orientation is of utmost importance in the construction of next-generation electronic and optical devices as well as in other applications such as (bio)sensors, reactive surfaces for catalysis, etc. Moreover, development of simple, rapid and low-cost fabrication processes of metallic patterned nanostructures is a challenging issue for the incorporation of such devices in real market applications. In this contribution, a direct-write method that results in highly conducting palladium-based nanopatterned structures without the need of applying subsequent curing processes is presented. Spin-coated films of palladium acetate were irradiated with an electron beam to produce palladium nanodeposits (PdNDs) with controlled size, shape and height. The use of different electron doses was investigated and its influence on the PdNDs features determined, namely: (1) thickness of the deposits, (2) atomic percentage of palladium content, (3) oxidation state of palladium in the deposit, (4) morphology of the sample and grain size of the Pd nanocrystals and (5) resistivity. It has been probed that the use of high electron doses, 30000 μC cm−2 results in the lowest resistivity reported to date for PdNDs, namely 145 μΩ cm, which is only one order of magnitude higher than bulk palladium. This result paves the way for development of simplified lithography processes of nanostructured deposits avoiding subsequent post-treatment steps.
Controllable assembly of continuous hollow graphene fibers with robust mechanical performance and multifunctionalities
Authors: Shi Lei , Dai Hongbo , Ni Qinqqing , Qi Xiaoming , Liu Wei , He Rui , Chi Zhangyi , Fu Yaqin
Published: January 2022

Macroscopic conformation of individual graphene sheets serves as the backbone of translating their intrinsic merits towards multifunctional practical applications. However, controllable and continuous assemblies of graphene-based nanomaterials to create stable macroscopic structural components are always in face of great challenge. We have developed a scalable converging-flow assisted wet-spinning methodology for continuously fabricating hollow graphene fibers (HGFs, the newest variation of solid graphene fibers) with high quality. The degradable silk thread is selectively utilized as the continuous hollow structure former that holds the coaxially stacked graphene sheets aligned through the converging-flow modulating process. For the first time, we have created the longest freestanding HGF in length of 2.1 m. The continuous HGFs are in an average diameter of 180 μm and with 4–8 μm adjustable wall thicknesses. The optimal HGF demonstrates an average tensile strength of 300 MPa and modulus of 2.49 GPa (comparable to typical solid graphene fibers, but the highest among the reported HGFs in literature) and an exceptional failure elongation of 10.8%. Additionally, our continuous HGFs exhibit spontaneous resistive response to thermal and strain stimuli (in form of large deformations and human motions), offering great potential for developing multifunctional sensors. We envision that this work demonstrates an effective and well-controlled macroscopic assembly methodology for the scaled-up mass production of HGFs.
MOF composites derived BiFeO3@Bi5O7I n–n heterojunction for enhanced photocatalytic performance
Authors: Zhu Yu , Li Chuwen , Hou Dongmei , Gao Guicheng , Luo Weiqi , Duan Zhengzhou , Zhang Tang , Xv Qinyun , Wang Yujia , Tang Jijun
Published: January 2022

BiFeO3 is a photocatalyst with excellent performance. However, its applications are limited due to its wide bandgap. In this paper, MIL-101(Fe)@BiOI composite material is synthesized by hydrothermal method and then calcined at high temperature to obtain BiFeO3@Bi5O7I composite material with high degradation capacity. Among them, an n–n heterojunction is formed, which improves the efficiency of charge transfer, and the recombination of light-generated electrons and holes promotes improved photocatalytic efficiency and stability. The result of photocatalytic degradation of tetracycline under visible light irradiation showed, BiFeO3@Bi5O7I (1:2) has the best photodegradation effect, with a degradation rate of 86.4%, which proves its potential as a photocatalyst.
High-sensitivity hybrid PbSe/ITZO thin film-based phototransistor detecting from 2100 to 2500 nm near-infrared illumination
Authors: Shikoh Ali Sehpar , Choi Gi Sang , Hong Sungmin , Jeong Kwang Seob , Kim Jaekyun
Published: January 2022

We report that high absorption PbSe colloidal quantum dots (QDs) having a peak absorbance beyond 2100 nm were synthesized and incorporated into InSnZnO (ITZO) channel layer-based thin film transistors (TFTs). It was intended that PbSe QDs with proportionally less photocurrent modulation can be remedied by semiconducting and low off-current ITZO-based TFT configuration. Multiple deposition scheme of PbSe QDs on ITZO metal oxide thin film gave rise to nearly linear increase of film thickness with acceptably uniform and smooth surface (less than 10 nm). Hybrid PbSe/ITZO thin film-based phototransistor exhibited the best performance of near infrared (NIR) detection in terms of response time, sensitivity and detectivity as high as 0.38 s, 3.91 and 4.55 × 107 Jones at room temperature, respectively. This is indebted mainly from the effective diffusion of photogenerated carrier from the PbSe surface to ITZO channel layer as well as from the conduction band alignment between them. Therefore, we believe that our hybrid PbSe/ITZO material platform can be widely used to be in favour of incorporation of solution-processed colloidal light absorbing material into the high-performance metal oxide thin film transistor configuration.
Molecular dynamics simulations of radiation damage in YBa2Cu3O7
Authors: Gray R L , Rushton M J D , Murphy S T
Published: January 2022

The advent of high-temperature superconductors (HTS) with high field strengths offers the possibility of building smaller, cheaper magnetically confined fusion reactors. However, bombardment by high energy neutrons ejected from the fusion reaction may damage the HTS tapes and impair their operation. Recreating the conditions present in an operational fusion reactor is experimentally challenging, therefore, this work uses molecular dynamics simulations to understand how radiation modifies the underlying crystal structure of YBa2Cu3O7. To facilitate the simulations a new potential was developed that allowed exchange of Cu ions between the two symmetrically distinct sites without modifying the structure. Radiation damage cascades predict the formation of amorphous regions surrounded by regions decorated with Cu and O defects found in the CuO-chains. The simulations suggest that the level of recombination that occurs is relatively low, resulting in a large number of remnant defects and that there is a no substantial temperature effect.
Physical realization of complex dynamical pattern formation in magnetic active feedback rings
Authors: Anderson Justin Q , Janantha P A Praveen , Alcala Diego A , Wu Mingzhong , Carr Lincoln D
Published: January 2022

We report the clean experimental realization of cubic–quintic complex Ginzburg–Landau (CQCGL) physics in a single driven, damped system. Four numerically predicted categories of complex dynamical behavior and pattern formation are identified for bright and dark solitary waves propagating around an active magnetic thin film-based feedback ring: (1) periodic breathing; (2) complex recurrence; (3) spontaneous spatial shifting; and (4) intermittency. These nontransient, long lifetime behaviors are observed in self-generated spin wave envelopes circulating within a dispersive, nonlinear yttrium iron garnet waveguide. The waveguide is operated in a ring geometry in which the net losses are directly compensated for via linear amplification on each round trip (of the order of 100 ns). These behaviors exhibit periods ranging from tens to thousands of round trip times (of the order of μs) and are stable for 1000s of periods (of the order of ms). We present ten observations of these dynamical behaviors which span the experimentally accessible ranges of attractive cubic nonlinearity, dispersion, and external field strength that support the self-generation of backward volume spin waves in a four-wave-mixing dominant regime. Three-wave splitting is not explicitly forbidden and is treated as an additional source of nonlinear losses. All observed behaviors are robust over wide parameter regimes, making them promising for technological applications. We present ten experimental observations which span all categories of dynamical behavior previously theoretically predicted to be observable. This represents a complete experimental verification of the CQCGL equation as a model for the study of fundamental, complex nonlinear dynamics for driven, damped waves evolving in nonlinear, dispersive systems. The reported dynamical pattern formation of self-generated dark solitary waves in attractive nonlinearity without external sources or potentials, however, is entirely novel and is presented for both the periodic breather and complex recurrence behaviors.