bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and testing of drift free force probe experiments with absolute distance control
Authors: Schwenzfeier Kai A. , Valtiner Markus
Published: July 2022

After almost 35 years of truly successful and transformative advancements, Atomic Force Microscopy (AFM) and, in general, scanning probe microscopy still have a fundamental limitation. This is constant drift and uncontrolled motion of probe and tested surface structures with respect to each other. This is inherently linked to the currently accepted design principle—only forces are measured, and distances are inferred from force measurements and piezo motions. Here, we demonstrate and test a new setup, which combines advantages of AFM and the surface forces apparatus, where absolute distances are measured by Multiple Beam White Light Interferometry (MBI). The novel and unique aspect of this apparatus consists of a synergistic combination of white light interferometric measurement of the absolute distance by direct reflection from an AFM cantilever and a fast distance clamping and drift correction using an IR-laser Fabry–Pérot interferometry-based approach (FPI). We demonstrate the capabilities of the system by force/distance measurements, benchmarking of distance control by direct comparison of MBI and FPI, and discuss potential applications of the system. This novel setup has the potential to form, monitor, and stress a single molecule or ligand/receptor bond on the molecular hook with sub-nanometer control of molecular distances over in principle infinite times.
Transition of the generation mechanism of high-order harmonics in an extended neon system
Authors: Gao Jingli , Ye Difa , Liu Jie , Kang Wei
Published: July 2022

Using a time-dependent density functional theory method, we perform a systematic numerical study of the transition of high-order harmonic generation in neon (Ne) systems from an isolated Ne atom to an extended Ne system of solid density. We show that ionized electrons wander in such extended systems until they meet a nearby ion and collide with it. The maximum energy edge for the main feature of the high-order harmonic spectrum in this “wandering electron” picture is determined as Eedge = Ip + 8Up, where Ip is the ionization energy of Ne and Up is the ponderomotive energy delivered by the driving laser. The factor of 8 comes from the maximum kinetic energy of an ionized electron in the driving laser field. Beyond the atomic limit of high-order harmonic spectra, a multiplatform feature is observed, corresponding to re-collisions of ionized electrons with their nearby ions. It is also shown that a Ne simple cubic lattice of appropriate size provides a selection condition for the direction of polarization of high-order harmonics beyond the atomic limit, which may be further used to manipulate the emitted radiation.
Rijke tube: A nonlinear oscillator
Authors: Manoj Krishna , Pawar Samadhan A. , Kurths Jürgen , Sujith R. I.
Published: July 2022

Dynamical systems theory has emerged as an interdisciplinary area of research to characterize the complex dynamical transitions in real-world systems. Various nonlinear dynamical phenomena and bifurcations have been discovered over the decades using different reduced-order models of oscillators. Different measures and methodologies have been developed theoretically to detect, control, or suppress the nonlinear oscillations. However, obtaining such phenomena experimentally is often challenging, time-consuming, and risky mainly due to the limited control of certain parameters during experiments. With this review, we aim to introduce a paradigmatic and easily configurable Rijke tube oscillator to the dynamical systems community. The Rijke tube is commonly used by the combustion community as a prototype to investigate the detrimental phenomena of thermoacoustic instability. Recent investigations in such Rijke tubes have utilized various methodologies from dynamical systems theory to better understand the occurrence of thermoacoustic oscillations and their prediction and mitigation, both experimentally and theoretically. The existence of various dynamical behaviors has been reported in single and coupled Rijke tube oscillators. These behaviors include bifurcations, routes to chaos, noise-induced transitions, synchronization, and suppression of oscillations. Various early warning measures have been established to predict thermoacoustic instabilities. Therefore, this review article consolidates the usefulness of a Rijke tube oscillator in terms of experimentally discovering and modeling different nonlinear phenomena observed in physics, thus transcending the boundaries between the physics and the engineering communities.
Precise wavefront characterization of x-ray optical elements using a laboratory source
Authors: Dresselhaus J. Lukas , Fleckenstein Holger , Domaracký Martin , Prasciolu Mauro , Ivanov Nikolay , Carnis Jerome , Murray Kevin T. , Morgan Andrew J. , Chapman Henry N. , Bajt Saša
Published: July 2022

Improvements in x-ray optics critically depend on the measurement of their optical performance. The knowledge of wavefront aberrations, for example, can be used to improve the fabrication of optical elements or to design phase correctors to compensate for these errors. At present, the characterization of such optics is made using intense x-ray sources, such as synchrotrons. However, the limited access to these facilities can substantially slow down the development process. Improvements in the brightness of lab-based x-ray micro-sources in combination with the development of new metrology methods, particularly ptychographic x-ray speckle tracking, enable characterization of x-ray optics in the lab with a precision and sensitivity not possible before. Here, we present a laboratory setup that utilizes a commercially available x-ray source and can be used to characterize different types of x-ray optics. The setup is used in our laboratory on a routine basis to characterize multilayer Laue lenses of high numerical aperture and other optical elements. This typically includes measurements of the wavefront distortions, optimum operating photon energy, and focal length of the lens. To check the sensitivity and accuracy of this laboratory setup, we compared the results to those obtained at the synchrotron and saw no significant difference. To illustrate the feedback of measurements on performance, we demonstrated the correction of the phase errors of a particular multilayer Laue lens using a 3D printed compound refractive phase plate.
Programmable morphing, electroactive porous shape memory polymer composites with battery-voltage Joule heating stimulated recovery
Authors: Lai-Iskandar S. , Li W. H. , Tsang S. H. , Lee Y. H. , Teo E. H. T.
Published: July 2022

Direct fabrication of electroactive shape memory polymer composites (eSMPCs) into complex non-planar geometries is highly desirable to enable remotely deployable, form-functional structures. However, traditional processes such as injection molding, casting, and extrusion limit the producible geometries to planar ribbons, wires, or tubes and the design of deployment modes to flattening-out/self-folding motions. To achieve low-voltage eSMPCs with a complex geometry, we report a direct fabrication strategy of bespoked-geometry eSMPCs via a two-stage sequential cure-and-foam technique for a new type of porous eSMPC, functionalized with 3D graphene nanofoam monolith (3DC). In our method, we resolved the difficulty in shaping fragile 3DC, and thus, various complex shape transforms (curved, helical, and wavy) can be intuitively designed via direct sculpting. Our method can be compatible with kirigami techniques for the design of hierarchical and combinatorial shape-change structures. 3DC not only serves as an intrinsic heater but, during synthesis, its cell walls also act as a confinement framework for architecting porosity within 3DC-eSMPCs, which can be actuated with low-voltage (7.5 V, <2 W). The herein reported 3DC-eSMPC and its synthesis strategy represent a new method and material to fabricate low-voltage deployables of bespoked shapes, capable of low-voltage actuation.
Ab initio composite strategies and multireference approaches for lanthanide sulfides and selenides
Authors: S. Almeida Nuno M. , Melin Timothé R. L. , North Sasha C. , Welch Bradley K. , Wilson Angela K.
Published: July 2022

The f-block ab initio correlation consistent composite approach was used to predict the dissociation energies of lanthanide sulfides and selenides. Geometry optimizations were carried out using density functional theory and coupled cluster singles, doubles, and perturbative triples with one- and two-component Hamiltonians. For the two-component calculations, relativistic effects were accounted for by utilizing a third-order Douglas–Kroll–Hess Hamiltonian. Spin–orbit coupling was addressed with the Breit–Pauli Hamiltonian within a multireference configuration interaction approach. The state averaged complete active space self-consistent field wavefunctions obtained for the spin–orbit coupling energies were used to assign the ground states of diatomics, and several diagnostics were used to ascertain the multireference character of the molecules.
A new endstation for extreme-ultraviolet spectroscopy of free clusters and nanodroplets
Authors: Bastian Björn , Asmussen Jakob D. , Ben Ltaief Ltaief , Czasch Achim , Jones Nykola C. , Hoffmann Søren V. , Pedersen Henrik B. , Mudrich Marcel
Published: July 2022

In this work, we present a new endstation for the AMOLine of the ASTRID2 synchrotron at Aarhus University, which combines a cluster and nanodroplet beam source with a velocity map imaging and time-of-flight spectrometer for coincidence imaging spectroscopy. Extreme-ultraviolet spectroscopy of free nanoparticles is a powerful tool for studying the photophysics and photochemistry of resonantly excited or ionized nanometer-sized condensed-phase systems. Here, we demonstrate this capability by performing photoelectron–photoion coincidence experiments with pure and doped superfluid helium nanodroplets. Different doping options and beam sources provide a versatile platform to generate various van der Waals clusters as well as He nanodroplets. We present a detailed characterization of the new setup and show examples of its use for measuring high-resolution yield spectra of charged particles, time-of-flight ion mass spectra, anion–cation coincidence spectra, multi-coincidence electron spectra, and angular distributions. A particular focus of the research with this new endstation is on intermolecular charge and energy-transfer processes in heterogeneous nanosystems induced by valence-shell excitation and ionization.
Refractory metal-based ohmic contacts on
β
-Ga2O3 using TiW
Authors: Tetzner Kornelius , Schewski Robert , Popp Andreas , Anooz Saud Bin , Chou Ta-Shun , Ostermay Ina , Kirmse Holm , Würfl Joachim
Published: July 2022

The present work investigates the use of the refractory metal alloy TiW as a possible candidate for the realization of ohmic contacts to the ultrawide bandgap semiconductor β-Ga2O3. Ohmic contact properties were analyzed by transfer length measurements of TiW contacts annealed at temperatures between 400 and 900 °C. Optimum contact properties with a contact resistance down to 1.5 × 10−5 Ω cm2 were achieved after annealing at 700 °C in nitrogen on highly doped β-Ga2O3. However, a significant contact resistance increase was observed at annealing temperatures above 700 °C. Cross-sectional analyses of the contacts using scanning transmission electron microscopy revealed the formation of a TiOx interfacial layer of 3–5 nm between TiW and β-Ga2O3. This interlayer features an amorphous structure and most probably possesses a high amount of vacancies and/or Ga impurities supporting charge carrier injection. Upon annealing at temperatures of 900 °C, the interlayer increases in thickness up to 15 nm, featuring crystalline-like properties, suggesting the formation of rutile TiO2. Although severe morphological changes at higher annealing temperatures were also verified by atomic force microscopy, the root cause for the contact resistance increase is attributed to the structural changes in thickness and crystallinity of the interfacial layer.
Spatiotemporal patterns of firearm acquisition in the United States in different presidential terms
Authors: Wang Xu , Sipahi Rifat , Porfiri Maurizio
Published: July 2022

This study develops mathematical tools and approaches to investigate spatiotemporal patterns of firearm acquisition in the U.S. complemented by hypothesis testing and statistical analysis. First, state-level and nation-level instant background check (BC) data are employed as proxy of firearm acquisition corresponding to 1999–2021. The relative-phase time-series of BC in each U.S. state is recovered and utilized to calculate the time-series of the U.S. states’ synchronization degree. We reveal that U.S. states present a high-level degree of synchronization except in 2010–2011 and after 2018. Comparing these results with respect to a sitting U.S. president provides additional information: specifically, any two presidential terms are characterized by statistically different synchronization degrees except G. W. Bush’s first term and B. H. Obama’s second term. Next, to detail variations of BC, short-time Fourier transform, dimensionality reduction techniques, and diffusion maps are implemented within a time-frequency representation. Firearm acquisition in the high frequency band is described by a low-dimensional embedding, in the form of a plane with two embedding coordinates. Data points on the embedding plane identify separate clusters that signify state transitions in the original BC data with respect to different time windows. Through this analysis, we reveal that the frequency content of the BC data has a time-dependent characteristic. By comparing the diffusion map at hand with respect to a presidential term, we find that at least one of the embedding coordinates presents statistically significant variations between any two presidential terms except B. H. Obama’s first term and D. J. Trump’s pre-COVID term. The results point at a possible interplay between firearm acquisition in the U.S. and a presidential term.
Fluid viscoelasticity suppresses chaotic convection and mixing due to electrokinetic instability
Authors: Sasmal C.
Published: July 2022

When two fluids of different electrical conductivities are transported side by side in a microfluidic device under the influence of an electric field, an electrokinetic instability (EKI) is often generated after some critical values of the applied electric field strength and conductivity ratio. Many prior experimental and numerical studies show that this phenomenon results in a chaotic flow field inside a microdevice, thereby facilitating the mixing of two fluids if they are Newtonian in behavior. However, the present numerical study shows that this chaotic convection arising due to the electrokinetic instability can be suppressed if the fluids are viscoelastic instead of Newtonian ones. In particular, we observe that as the Weissenberg number (ratio of the elastic to that of the viscous forces) gradually increases and the polymer viscosity ratio (ratio of the solvent viscosity to that of the zero-shear rate viscosity of the polymeric solution) gradually decreases, the chaotic fluctuation inside a T microfluidic junction decreases within the present range of conditions encompassed in this study. We demonstrate that this suppression of the chaotic motion occurs due to the formation of a strand of high elastic stresses at the interface of the two fluids. We further show that this suppression of the chaotic fluctuation (particularly, the span-wise one) inhibits the mixing of two viscoelastic fluids. Therefore, one needs to be cautious when the EKI phenomenon is planned to use for mixing such viscoelastic fluids. Our observations are in line with that seen in limited experimental studies conducted for these kinds of viscoelastic fluids.
Dynamics of NEMS resonators across dissipation limits
Authors: Ti C. , McDaniel J. G. , Liem A. , Gress H. , Ma M. , Kyoung S. , Svitelskiy O. , Yanik C. , Kaya I. I. , Hanay M. S. , González M. , Ekinci K. L.
Published: July 2022

The oscillatory dynamics of nanoelectromechanical systems (NEMS) is at the heart of many emerging applications in nanotechnology. For common NEMS, such as beams and strings, the oscillatory dynamics is formulated using a dissipationless wave equation derived from elasticity. Under a harmonic ansatz, the wave equation gives an undamped free vibration equation; solving this equation with the proper boundary conditions provides the undamped eigenfunctions with the familiar standing wave patterns. Any harmonically driven solution is expressible in terms of these undamped eigenfunctions. Here, we show that this formalism becomes inconvenient as dissipation increases. To this end, we experimentally map out the position- and frequency-dependent oscillatory motion of a NEMS string resonator driven linearly by a non-symmetric force at one end at different dissipation limits. At low dissipation (high Q factor), we observe sharp resonances with standing wave patterns that closely match the eigenfunctions of an undamped string. With a slight increase in dissipation, the standing wave patterns become lost, and waves begin to propagate along the nanostructure. At large dissipation (low Q factor), these propagating waves become strongly attenuated and display little, if any, resemblance to the undamped string eigenfunctions. A more efficient and intuitive description of the oscillatory dynamics of a NEMS resonator can be obtained by superposition of waves propagating along the nanostructure.
Synergistic effects of rice straw and its biochar on availability of phosphorus fertiliser in acidic soils
Authors: Baquy M. Abdulaha-Al , Pan Xiao-ying , Li Jiu-yu , Hong Zhi-neng , Kamran Muhammad Aqeel , Xu Ren-kou
Published: July 2022

Contexts Increasing the availability of phosphorus fertiliser is needed for better crop production in acidic soils. Aims To observe how rice straw and its biochar affect phosphorus fertiliser recovery in an Ultisol and an Oxisol as a measure for the availability of phosphorus in acidic soils. Methods A 60-day incubation study was conducted using treatments comprising of straw (1.5%, w/w) and biochar produced at 400°C (1.5%, w/w), a mixture of each at the same rate, and a control with two phosphorus rates of 0 and 100 mg kg−1. Key results The application of both the straw and the biochar alone and in combination raised the soil pH by 0.12, 0.20, 0.32, 0.17, 0.31 and 0.38 units, and cation exchange capacity by 2.06, 3.02, 2.72, 2.56, 6.28, and 8.40% compared to control for both the Ultisol and the Oxisol, respectively. Similarly, dissolved organic matter also increased by 74.19, 55.28, 84.63, 24.39 and 136.44%, respectively compared to control for the corresponding treatments and soils except the straw amended Ultisol. With an increase in the soil pH, the rate of phosphorus recovery increased by 11.73, 12.99, 23.89, 2.72, 5.23 and 6.28% compared to control for the corresponding treatments and soils, respectively. Phosphate adsorption by the soils became hindered by increased cation exchange capacity and dissolved organic matter but decreased exchangeable trivalent aluminium cations, which led to a greater phosphorus recovery in both the amended soils. Conclusions The combined application of rice straw and biochar would be the appropriate choice for increasing the applied phosphorus fertiliser availability in acid soils.
Germination behaviour of
Authors: Ali Mohammad , Suthar Premal C. , Williams Alwyn , Widderick Michael , Adkins Steve W.
Published: July 2022

Context Avena sterilis subsp. ludoviciana (wild oats) is one of the major winter weeds of the Northern Grains Region of Australia. The abundance of this weed increased dramatically after the adoption of no-tillage conservation agriculture (NTCA). However, information is lacking on the germination characteristics of the two types of seed (i.e. primary and secondary) that it produces. Aims We aimed to determine the light and temperature requirements for germination and the time to germination of primary and secondary seeds of A. ludoviciana, in order to find ways to manage this weed effectively under NTCA systems. Methods Primary and secondary seeds and caryopses from two southern and two northern biotypes were exposed to a range of temperature and light regimes in the glasshouse, and germination was assessed. Key results All biotypes had ∼25% higher germination from primary than secondary seeds. Removing the hull increased caryopsis germination by ∼70%. The use of a light/dark photoperiod stimulated germination of both types of seed and caryopses compared with continuous darkness. Based on data for caryopses, 7°C and 9°C were found to be optimal germination temperatures for southern and northern biotypes, respectively. At optimum germination temperature, primary caryopses germinated 7–20 days earlier than secondary caryopses. In addition, a light/dark environment resulted in germination 2–6 days earlier than continuous darkness. Conclusions In the Northern Grains Region, seeds retained on or close to the soil surface (i.e. in NTCA systems) can undergo maximum germination during May–June (late autumn–winter), when long-term average temperatures match optimum germination temperatures. This coincides with winter crop plantings. Implications The seasonal timing of germination and the difference in germination timing between primary and secondary seeds, which help to stagger emergence of this weed, are major issues that need to be addressed in NTCA systems.
Allosteric role of a structural NADP
+
molecule in glucose-6-phosphate dehydrogenase activity
Authors: Wei Xuepeng , Kixmoeller Kathryn , Baltrusaitis Elana , Yang Xiaolu , Marmorstein Ronen
Published: July 2022

Human glucose-6-phosphate dehydrogenase (G6PD) is the main cellular source of NADPH, and thus plays a key role in maintaining reduced glutathione to protect cells from oxidative stress disorders such as hemolytic anemia. G6PD is a multimeric enzyme that uses the cofactors β-D-glucose 6-phosphate (G6P) and “catalytic” NADP
+
(NADP
+
c), as well as a “structural” NADP
+
(NADP
+
s) located ∼25 Å from the active site, to generate NADPH. While X-ray crystallographic and biochemical studies have revealed a role for NADP
+
s in maintaining the catalytic activity by stabilizing the multimeric G6PD conformation, other potential roles for NADP
+
s have not been evaluated. Here, we determined the high resolution cryo-electron microscopy structures of human wild-type G6PD in the absence of bound ligands and a catalytic G6PD-D200N mutant bound to NADP
+
c and NADP
+
s in the absence or presence of G6P. A comparison of these structures, together with previously reported structures, reveals that the unliganded human G6PD forms a mixture of dimers and tetramers with similar overall folds, and binding of NADP
+
s induces a structural ordering of a C-terminal extension region and allosterically regulates G6P binding and catalysis. These studies have implications for understanding G6PD deficiencies and for therapy of G6PD-mediated disorders.
Why are people antiscience, and what can we do about it?
Authors: Philipp-Muller Aviva , Lee Spike W. S. , Petty Richard E.
Published: July 2022

From vaccination refusal to climate change denial, antiscience views are threatening humanity. When different individuals are provided with the same piece of scientific evidence, why do some accept whereas others dismiss it? Building on various emerging data and models that have explored the psychology of being antiscience, we specify four core bases of key principles driving antiscience attitudes. These principles are grounded in decades of research on attitudes, persuasion, social influence, social identity, and information processing. They apply across diverse domains of antiscience phenomena. Specifically, antiscience attitudes are more likely to emerge when a scientific message comes from sources perceived as lacking credibility; when the recipients embrace the social membership or identity of groups with antiscience attitudes; when the scientific message itself contradicts what recipients consider true, favorable, valuable, or moral; or when there is a mismatch between the delivery of the scientific message and the epistemic style of the recipient. Politics triggers or amplifies many principles across all four bases, making it a particularly potent force in antiscience attitudes. Guided by the key principles, we describe evidence-based counteractive strategies for increasing public acceptance of science.
The Hippo pathway regulates axis formation and morphogenesis in
Hydra
Authors: Brooun Maria , Salvenmoser Willi , Dana Catherine , Sudol Marius , Steele Robert , Hobmayer Bert , McNeill Helen
Published: July 2022

How did cells of early metazoan organisms first organize themselves to form a body axis? The canonical Wnt pathway has been shown to be sufficient for induction of axis in Cnidaria, a sister group to Bilateria, and is important in bilaterian axis formation. Here, we provide experimental evidence that in cnidarian
Hydra
the Hippo pathway regulates the formation of a new axis during budding upstream of the Wnt pathway. The transcriptional target of the Hippo pathway, the transcriptional coactivator YAP, inhibits the initiation of budding in
Hydra
and is regulated by
Hydra
LATS. In addition, we show functions of the Hippo pathway in regulation of actin organization and cell proliferation in
Hydra
. We hypothesize that the Hippo pathway served as a link between continuous cell division, cell density, and axis formation early in metazoan evolution.
Propagation of societal gender inequality by internet search algorithms
Authors: Vlasceanu Madalina , Amodio David M.
Published: July 2022

Humans increasingly rely on artificial intelligence (AI) for efficient and objective decision-making, yet there is increasing concern that algorithms used by modern AI systems produce discriminatory outputs, presumably because they are trained on data in which societal biases are embedded. As a consequence, their use by human decision makers may result in the propagation, rather than reduction, of existing disparities. To assess this hypothesis empirically, we tested the relation between societal gender inequality and algorithmic search output and then examined the effect of this output on human decision-making. First, in two multinational samples (
n
= 37, 52 countries), we found that greater nation-level gender inequality was associated with more male-dominated Google image search results for the gender-neutral keyword “person” (in a nation’s dominant language), revealing a link between societal-level disparities and algorithmic output. Next, in a series of experiments with human participants (
n
= 395), we demonstrated that the gender disparity associated with high- vs. low-inequality algorithmic outputs guided the formation of gender-biased prototypes and influenced hiring decisions in novel scenarios. These findings support the hypothesis that societal-level gender inequality is recapitulated in internet search algorithms, which in turn can influence human decision makers to act in ways that reinforce these disparities.
Nontrivial phase matching in helielectric polarization helices: Universal phase matching theory, validation, and electric switching
Authors: Zhao Xiuhu , Long Huaqian , Xu Hao , Kougo Junichi , Xia Runli , Li Jinxing , Huang Mingjun , Aya Satoshi
Published: July 2022

Second-order optical nonlinearity is the essential concept for realizing modern technologies of optical wavelength conversion. The emerging helical polarization fluid, dubbed helielectric nematic, now makes it possible to design and easily fabricate various polarization structures and control their optical responses. The matter family is demonstrated as an ideal liquid platform for nonlinear optical conversion and amplification with electric-reconfigurable tunability. We here develop a universal phase matching theory and reveal a nonclassic chirality-sensitive phase-matching condition in the polarization helices through both the numerical calculation and the experimental validations. The nonlinear optical amplification can be dramatically modulated with a contrast ratio of >100:1 by an in-plane electric field. Furthermore, we employ the director relaxation under electric fields coupled with nonlinear optical simulation to clarify the topology–light interactions.
Gravitational waves in gauge theory gravity with a negative cosmological constant
Authors: Xu Jianfei
Published: July 2022

In this paper, we discuss the gravitational waves in the context of gauge theory gravity with a negative cosmological constant. The gauge theory gravity is a gravity theory under gauge formulation in the language of geometric algebra. In contrast to general relativity, the background spacetime in gauge theory gravity is flat, the gauge freedom comes from the fact that equations in terms of physical quantities should be kept in a covariant form under spacetime displacement and rotation. Similar to the electromagnetism, the gauge formulation enables us to interpret the gravitational force as a gauge force on the background flat spacetime. The dynamical fields that describe the gravitational interactions are those position and rotation gauge fields introduced as the requirement of the gauge covariance. The gravitational field equations can be derived from the least action principle with the action as a gauge invariant quantity built from the covariant field strength. We discuss the gravitational wave solutions of the field equations with a negative cosmological constant, and show that these solutions are of Petrov type-N. We also discuss the velocity memory effect by calculating the velocity change of an initially free falling massive particle due to the presence of the gravitational waves.
Silicene: an excellent material for flexible electronics
Authors: Sahoo Swastik , Sinha Abhinaba , Koshi Namitha Anna , Lee Seung-Cheol , Bhattacharjee Satadeep , Muralidharan Bhaskaran
Published: July 2022

The outstanding properties of graphene have laid the foundation for exploring graphene-like 2D systems, commonly referred to as 2D-Xenes. Among them, silicene is a front-runner due to its compatibility with current silicon fabrication technologies. Recent works on silicene have unveiled its useful electronic and mechanical properties. The rapid miniaturization of silicon devices and the useful electro-mechanical properties of silicene necessitate the exploration of potential applications of silicene flexible electronics in nano electro-mechanical systems. Using a theoretical model derived from the integration of ab initio density-functional theory and quantum transport theory, we investigate the piezoresistance effect of silicene in the nanoscale regime. As with graphene, we obtain a small value of the piezoresistance gauge factor (GF) of silicene, which is sinusoidally dependent on the transport angle. The small GF of silicene is attributed to its robust Dirac cone and strain-independent valley degeneracy. Based on the obtained results, we propose to use silicene as an interconnect in flexible electronic devices and as a reference piezoresistor in strain sensors. This work will hence pave the way for exploring flexible electronics applications in other 2D-Xene materials.
First-principles predictions of tunable half metallicity in zigzag GaN nanoribbons with possible applications in CO detection and spintronics
Authors: Yogi Rachana , Jha Kamal K , Shukla Alok , Jaiswal Neeraj K
Published: July 2022

Based on systematic first-principles density-functional theory simulations, we predict that the zigzag GaN nanoribbons (ZGaNNRs) can be used both as highly efficient CO detectors as well as spin filters. Our calculations, performed both on infinitely long nanoribbons, and also on finite strands, suggest that: (a) CO binds strongly at the edges of ZGaNNRs, and (b) that several of the resultant configurations exhibit half-metallic behavior. We considered various edge-passivation sites and found that all the resultant structures are thermodynamically stable. The metallic, half-metallic, and semiconducting configurations are observed as a function of CO passivation coverage. We also compute the current–voltage (I–V) characteristics of various structures using the Landauer formalism, and find that the devices made up of half-metallic configurations act as highly-efficient spin filters. The effect of CO concentration is also investigated which suggests a viable way to not just tune the electronic band gap of ZGaNNRs, but also their half metallicity. Our simulations thus suggest a new direction of research for possible device applications of III–V heterostructures.
Polarization-independent resonant lattice Kerker effect in phase-change metasurface
Authors: Xiong Lei , Luo Xiaoqing , Ding Hongwei , Lu Yuanfu , Li Guangyuan
Published: July 2022

Resonant lattice Kerker effect in periodic resonators is one of the most interesting generalizations of the Kerker effect that relates to various fascinating functionalities such as scattering management and Huygens metasurfaces. However, so far this effect has been shown to be sensitive to the incident polarization, restricting its applications. Here, we report, for the first time, polarization-independent resonant lattice Kerker effect in metasurfaces composed of periodic Ge2Se2Te5 (GST) disks. For such a metasurface of square lattice, the spectrally overlap of the electric dipole and magnetic dipole surface lattice resonances can be realized by choosing an appropriate GST crystalline fraction regardless of the incident polarization. The operation wavelength and the required GST crystalline fraction can be conveniently tuned over large ranges since these parameters scale linearly with the disk size and the lattice period, greatly facilitating the design. Making use of the obtained resonant lattice Kerker effect, we realize a reconfigurable and polarization-independent lattice Huygens’ metasurface with a dynamic phase modulation of close to 2π and high transmittance. This work will advance the engineering of the resonant lattice Kerker effect and promote its applications in phase modulation and wavefront control.
Solidification of ternary melts with a two-phase layer
Authors: Toropova L V , Ivanov A A , Osipov S I , Yang Y , Makoveeva E V , Alexandrov D V
Published: July 2022

This review is concerned with the nonstationary solidification of three-component systems in the presence of two moving phase transition regions—the main (primary) and cotectic layers. A non-linear moving boundary problem has been developed and its analytical solutions have been defined. Namely, the temperature and impurity concentration distributions were determined, the solid phase fractions in the phase transition regions and the laws of motion of their boundaries were found. It was shown that variations in the initial impurity concentration affect significantly the ratio between the lengths of the two-phase layers. A non-linear liquidus surface equation is theoretically taken into account as well.
Sepiolite and ZIF-67 co-modified PAN/PVdF-HFP nanofiber separators for advanced Li-ion batteries
Authors: Jiang Wenwu , Han Yi , Ding Yanhuai
Published: July 2022

Electrospun PAN/PVdF-HFP membranes have the potential to be used as separators for Li-ion batteries owing to their good mechanical properties and high chemical stability. However, the application of PAN/PVdF-HFP separators has been hampered by their poor electrochemical performances. In this study, semi-aligned PAN/PVdF-HFP nanofiber separators have been fabricated by an electrospinning technology. Sepiolite and ZIF-67 co-modification was employed to enhance the physical properties of the PAN/PVdF-HFP separators. The test cells with the as-prepared composite separator showed better electrochemical performance than the commercial and raw PAN/PVdF-HFP separators.
Electrostatic focusing of cold and heavy molecules for the ACME electron EDM search
Authors: Wu X , Hu P , Han Z , Ang D G , Meisenhelder C , Gabrielse G , Doyle J M , DeMille D
Published: July 2022

The current best upper limit for electron electric dipole moment (EDM), |d
e| < 1.1 × 10−29 e cm (90% confidence), was set by the ACME Collaboration in 2018. The ACME experiment uses a spin-precession measurement in a cold beam of thorium monoxide (ThO) molecules to detect d
e. An improvement in statistical uncertainty would be possible with more efficient use of molecules from the cryogenic buffer gas beam source. Here, we demonstrate electrostatic focusing of the ThO beam with a hexapole lens. This results in a factor of 16 enhancement in the molecular flux detectable downstream, in a beamline similar to that built for the next generation of ACME. We also demonstrate an upgraded rotational cooling scheme that increases the ground state population by 3.5 times compared to no cooling, consistent with expectations and a factor of 1.4 larger than previously in ACME. When combined with other demonstrated improvements, we project over an order of magnitude improvement in statistical sensitivity for the next generation ACME electron EDM search.
Data-driven predictive modeling of Hubble parameter
Authors: Salti Mehmet , Ciger Emel , Kangal Evrim Ersin , Zengin Bilgin
Published: July 2022

We redesign the generalized pressure dark energy (GPDE) model, which is covering three common types of pressure parameterizations, with the help of a caloric framework to construct a theoretical ground for the machine learning (ML) analysis of cosmic Hubble parameter. The theoretical setup was optimized to find out appropriate values of its arbitrary parameters with the help of genetic neural network (GNN) algorithm and the most recent observational measurements of Hubble parameter. Since there is a shortcoming that the GNN process does not provide a direct method to calculate errors on the optimized values of free model parameters, we therefore take the Fisher Information Matrix (FIM) algorithm into account to deal with this issue. We see that the best-fitting value of Hubble constant and dimensionless dark energy density are in very good agreement with the most recent observations. Also, we discussed the optimized model from a cosmological perspective by making use of the evolutionary behavior of some cosmological parameters to present additional cosmological aspects of our theoretical proposal. It is concluded that our model implies physically meaningful results. In summary, the constructed model can explain the current accelerated expansion phase of the cosmos via Hubble parameter successfully.
Prospects for H-mode inhibition in negative triangularity tokamak reactor plasmas
Authors: Nelson A.O. , Paz-Soldan C. , Saarelma S.
Published: July 2022

Instability to high toroidal mode number (n) ballooning modes has been proposed as the primary gradient-limiting mechanism for tokamak equilibria with negative triangularity (NT) (δ) shaping, preventing access to strong H-mode regimes when δ is sufficiently negative. To understand how this mechanism extrapolates to reactor conditions, we model the infinite-n ballooning stability as a function of internal profiles and equilibrium shape using a combination of the CHEASE and BALOO codes. While the critical δ required for avoiding 2nd stability to high-n modes is observed to depend in a complicated way on various shaping parameters, including the equilibrium inverse aspect ratio, elongation and squareness, equilibria with NT are robustly prohibited from accessing the 2nd stability region, offering the prediction that NT reactors should maintain L-mode-like operation. In order to access high-n 2nd stability, the local shear over the entire bad curvature region must be sufficiently negative to overcome curvature destabilization on the low field side. Scalings of the ballooning-limited pedestal height are provided as a function of plasma parameters to aid future scenario design.
Multiangle scanning for measuring radiation beam profiles with a typical size of 10 millimetres — Proof-of-principle experiments
Authors: Bulavskaya A.A. , Cherepennikov Yu.M. , Grigorieva A.A. , Miloichikova I.A. , Stuchebrov S.G.
Published: July 2022

In this research, a method for acquiring radiation beam
profiles was developed. Multiple linear beam scanning using a
detection strip was performed in a beam cross section at different
angles. The obtained data were then mathematically processed and
transformed into the radiation beam profile. The profiles of X-ray
and electron beams were obtained experimentally using the proposed
method, and are reported herein.
Spring snow cover duration and tundra greenness in the Lena Delta, Siberia: two decades of MODIS satellite time series (2001–2021)
Authors: Heim Birgit , Lisovski Simeon , Wieczorek Mareike , Morgenstern Anne , Juhls Bennet , Shevtsova Iuliia , Kruse Stefan , Boike Julia , Fedorova Irina , Herzschuh Ulrike
Published: July 2022

The Lena Delta in Siberia is the largest delta in the Arctic and as a snow-dominated ecosystem particularly vulnerable to climate change. Using the two decades of MODerate resolution Imaging Spectroradiometer satellite acquisitions, this study investigates interannual and spatial variability of snow-cover duration and summer vegetation vitality in the Lena Delta. We approximated snow by the application of the normalized difference snow index and vegetation greenness by the normalized difference vegetation index (NDVI). We consolidated the analyses by integrating reanalysis products on air temperature from 2001 to 2021, and air temperature, ground temperature, and the date of snow-melt from time-lapse camera (TLC) observations from the Samoylov observatory located in the central delta. We extracted spring snow-cover duration determined by a latitudinal gradient. The ‘regular year’ snow-melt is transgressing from mid-May to late May within a time window of 10 days across the delta. We calculated yearly deviations per grid cell for two defined regions, one for the delta, and one focusing on the central delta. We identified an ensemble of early snow-melt years from 2012 to 2014, with snow-melt already starting in early May, and two late snow-melt years in 2004 and 2017, with snow-melt starting in June. In the times of TLC recording, the years of early and late snow-melt were confirmed. In the three summers after early snow-melt, summer vegetation greenness showed neither positive nor negative deviations. Whereas, vegetation greenness was reduced in 2004 after late snow-melt together with the lowest June monthly air temperature of the time series record. Since 2005, vegetation greenness is rising, with maxima in 2018 and 2021. The NDVI rise since 2018 is preceded by up to 4 °C warmer than average June air temperature. The ongoing operation of satellite missions allows to monitor a wide range of land surface properties and processes that will provide urgently needed data in times when logistical challenges lead to data gaps in land-based observations in the rapidly changing Arctic.
A national estimate of U.S. underground natural gas storage incident emissions
Authors: Li Hugh Z , Saint-Vincent Patricia M B , Mundia-Howe Mumbi , Pekney Natalie J
Published: July 2022

The 2015 Aliso Canyon storage well blowout was widely reported as the worst natural gas leak in the history of the United States (U.S.) and released ∼0.1 million metric tons of methane (CH4), a potent greenhouse gas. Although storage well fugitive emissions are estimated in the U.S. Environmental Protection Agency’s annual Greenhouse Gas Inventory, the inventory does not include historical estimates of anomalous large emission events other than Aliso Canyon or smaller incident related CH4 releases. A total of 129 underground natural gas storage (UGS) incident-related events between 1940 and 2016 were compiled from various federal/state agencies and literature reviews. Incident emissions were estimated based on best available information, such as direct operator reports, the monetary cost of gas lost, or modeling of the escaping gas at sonic speeds. There are 387 active UGS fields in three types of reservoirs: salt caverns, aquifers, and depleted oil and gas (O&G) fields. 65% of events were in the depleted O&G fields, which account for 79% of storage fields. Texas recorded the highest number of incidents (20), 14 of which were in salt dome reservoirs. The incident emissions showed a heavy-tailed emission pattern with CH4 releases up to 29 billion cubic feet (8.2 × 108m3). The top seven events contributed 98% of the total estimated/measured CH4 emissions.
Motor vehicles’ problems with keeping the straight driving direction; analysis of selected case
Authors: Pusty T , Lewiński R , Kowieski H K
Published: July 2022

The article presents issues related to the testing and verification of the keeping of straight driving direction by motor vehicles. The subjective feelings of drivers were assigned specific values of physical quantities describing the rectilinear path of motion, i.e. the steering wheel angle and the force vector applied to the steering wheel of the vehicle under test while driven along a straight path. This made it possible to determine the limit values enabling the assessment whether the object under test has a tendency to move straight ahead without any unusual steering corrections. The cases analysed relate to the situations where measurements of wheel geometry settings do not show significant deviations from the standard but, in spite of that, the vehicle requires unusual steering corrections by the driver to maintain a straight path.
Effects of motorbike front suspension component operation on torsional vibration frequencies
Authors: Dębowski A
Published: July 2022

Riding a motorbike requires much more experience than other types of vehicles. However, not only insufficient skills may contribute to dangerous driving situations, but also vibrations generated in the steering system of a motorbike. This paper presents a method of vibration analysis on the example of a motorbike steering system using a transmittance model and shows how to extract the relevant frequencies for analysis. The effects of selected stiffness and damping parameters are analysed and an assessment is made of how the frequencies for wobble vibration will change over the life of the steering components. The results were presented using Bode diagrams.
Modelling of dynamics of the suspension of tandem axles of a multi-axle vehicle provided with a novel load-equalising system
Authors: Piłatowicz R , Luty W
Published: July 2022

The paper presents the problem of using multi-axle suspension systems in vehicles, concerning unbalanced distribution of axle loads while moving in off-road conditions. An innovative load balancing system for tandem axles, which limits the occurring overloads, is presented. A mathematical model is proposed to represent the suspension of a front “quarter” of a four-axle vehicle provided with a novel system to equalise the loads on two closely spaced (tandem) axles. The “quarter” of the vehicle is described as a set of rigid bodies linked with each other by spring and damping elements. The model has three degrees of freedom and defines vehicle’s responses to excitations (inputs) generated by road irregularities. The mathematical models known from the literature describe typical suspension systems and specific types of load balancing systems for two- and three-axle vehicles. This makes it impossible to apply them directly to simulation test of a vehicle with two front axles. A new model dedicated to the proposed load equalizing system, which allows simulation tests for the design and verification of the new system’s operation, has been prepared.