bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of entropy-swallowing point of blunt hypersonic cone
Authors: Han Yufeng , Zhou Jingtian , Cao Wei
Published: February 2022

Entropy swallowing is the phenomenon where the entropy layer is swallowed by the boundary layer developing downstream. In this work, the entropy-swallowing point over a 5° blunt hypersonic cone is investigated theoretically and numerically. An equation for obtaining the location of the entropy-swallowing point is derived herein that requires only the free-stream parameters. This equation also reveals the relationship between the entropy-swallowing point and the nose radius under the constant free-stream Mach number. The analytical results are entirely consistent with direct numerical simulation results. Furthermore, the influence of the Mach number and Reynolds number on the entropy-swallowing point is investigated. The location of the entropy-swallowing point depends more strongly on the Reynolds number than on the Mach number, with the entropy-swallowing point shifting further downstream as the Reynolds number increases. However, as the Mach number increases, its impact on the entropy-swallowing point decreases. Furthermore, the influence of the boundary-layer displacement also decreases with an increase of the Mach number.
Confinement effects on glass-forming mixtures: Insights from a combined experimental approach to aqueous ethylene glycol solutions in silica pores
Authors: Reuhl Melanie , Monnard Philipp , Vogel Michael
Published: February 2022

We perform nuclear magnetic resonance, broadband dielectric spectroscopy, and differential scanning calorimetry studies to ascertain the dynamical behaviors of aqueous ethylene glycol (EG) solutions in silica pores over broad temperature ranges. Both translational and rotational motions are analyzed, and the pore diameter (2.4–9.2 nm) and the EG concentration (12–57 mol. %) are varied, leading to fully liquid or partially crystalline systems. It is found that the translational diffusion coefficient strongly decreases when the diameter is reduced, resulting in a slowdown of nearly three orders of magnitude in the narrowest pores, while the confinement effects on the rotational correlation times are moderate. For the fully liquid solutions, we attribute bulk-like and slowed down reorientation processes to the central and interfacial pore regions, respectively. This coexistence is found in all the studied pores, and, hence, the range of the wall effects on the solution dynamics does not exceed ∼1 nm. Compared to the situation in the bulk, the concentration dependence is reduced in confinements, implying that the specific interactions of the molecular species with the silica walls lead to preferential adsorption. On the other hand, bulk-like structural relaxation is not observed in the partially frozen samples, where the liquid is sandwiched between the silica walls and the ice crystallites. Under such circumstances, there is another relaxation process with a weaker temperature dependence, which is observed in various kinds of partially frozen aqueous systems and denoted as the x process.
The parental active model: A unifying stochastic description of self-propulsion
Authors: Caprini Lorenzo , Sprenger Alexander R. , Löwen Hartmut , Wittmann René
Published: February 2022

We propose a new overarching model for self-propelled particles that flexibly generates a full family of “descendants.” The general dynamics introduced in this paper, which we denote as the “parental” active model (PAM), unifies two special cases commonly used to describe active matter, namely, active Brownian particles (ABPs) and active Ornstein–Uhlenbeck particles (AOUPs). We thereby document the existence of a deep and close stochastic relationship between them, resulting in the subtle balance between fluctuations in the magnitude and direction of the self-propulsion velocity. Besides illustrating the relation between these two common models, the PAM can generate additional offsprings, interpolating between ABP and AOUP dynamics, that could provide more suitable models for a large class of living and inanimate active matter systems, possessing characteristic distributions of their self-propulsion velocity. Our general model is evaluated in the presence of a harmonic external confinement. For this reference example, we present a two-state phase diagram that sheds light on the transition in the shape of the positional density distribution from a unimodal Gaussian for AOUPs to a Mexican-hat-like profile for ABPs.
Hierarchical timescales in the neocortex: Mathematical mechanism and biological insights
Authors: Li Songting , Wang Xiao-Jing
Published: February 2022

Significance

In the neocortex, while early sensory areas encode and process external inputs rapidly, higher-association areas are endowed with slow dynamics suitable for accumulating information over time. Such a hierarchy of temporal response windows along the cortical hierarchy naturally emerges in a model of multiareal primate cortex. This finding raises the question of why diverse temporal modes are not mixed in roughly the same way across the whole cortex, despite high connection density and an abundance of feedback loops. We investigate this question by mathematically analyzing the anatomically based network model of macaque cortex and theoretically show that three sufficient conditions of synaptic excitation and inhibition give rise to timescale segregation in a hierarchy, a functionally important characteristic of the cortex.
Mice expressing fluorescent PAR
2
reveal that endocytosis mediates colonic inflammation and pain
Authors: Latorre Rocco , Hegron Alan , Peach Chloe J. , Teng Shavonne , Tonello Raquel , Retamal Jeffri S. , Klein-Cloud Rafael , Bok Diana , Jensen Dane D. , Gottesman-Katz Lena , Rientjes Jeanette , Veldhuis Nicholas A. , Poole Daniel P. , Thomsen Alex R. B. , Schmidt Brian L. , Pothoulakis Charalabos H. , Rankin Carl , Xie Ying , Koon Hon Wai , Bunnett Nigel W.
Published: February 2022

G protein–coupled receptors (GPCRs) regulate many pathophysiological processes and are major therapeutic targets. The impact of disease on the subcellular distribution and function of GPCRs is poorly understood. We investigated trafficking and signaling of protease-activated receptor 2 (PAR
2
) in colitis. To localize PAR
2
and assess redistribution during disease, we generated knockin mice expressing PAR
2
fused to monomeric ultrastable green fluorescent protein (muGFP). PAR
2
-muGFP signaled and trafficked normally. PAR
2
messenger RNA was detected at similar levels in

Par
2
-mugfp

and wild-type mice. Immunostaining with a GFP antibody and RNAScope in situ hybridization using
F2rl1
(PAR
2
) and
Gfp
probes revealed that PAR
2
-muGFP was expressed in epithelial cells of the small and large intestine and in subsets of enteric and dorsal root ganglia neurons. In healthy mice, PAR
2
-muGFP was prominently localized to the basolateral membrane of colonocytes. In mice with colitis, PAR
2
-muGFP was depleted from the plasma membrane of colonocytes and redistributed to early endosomes, consistent with generation of proinflammatory proteases that activate PAR
2
. PAR
2
agonists stimulated endocytosis of PAR
2
and recruitment of Gα
q
, Gα
i
, and β-arrestin to early endosomes of T84 colon carcinoma cells. PAR
2
agonists increased paracellular permeability of colonic epithelial cells, induced colonic inflammation and hyperalgesia in mice, and stimulated proinflammatory cytokine release from segments of human colon. Knockdown of dynamin-2 (
Dnm2
), the major colonocyte isoform, and Dnm inhibition attenuated PAR
2
endocytosis, signaling complex assembly and colonic inflammation and hyperalgesia. Thus, PAR
2
endocytosis sustains protease-evoked inflammation and nociception and PAR
2
in endosomes is a potential therapeutic target for colitis.
Loss of glucose 6-phosphate dehydrogenase function increases oxidative stress and glutaminolysis in metastasizing melanoma cells
Authors: Aurora Arin B. , Khivansara Vishal , Leach Ashley , Gill Jennifer G. , Martin-Sandoval Misty , Yang Chendong , Kasitinon Stacy Y. , Bezwada Divya , Tasdogan Alpaslan , Gu Wen , Mathews Thomas P. , Zhao Zhiyu , DeBerardinis Ralph J. , Morrison Sean J.
Published: February 2022

Significance

Melanoma metastasis is limited by oxidative stress. Cells that enter the blood experience high levels of reactive oxygen species and usually die of ferroptosis. We found that melanoma cells become more dependent upon the oxidative pentose phosphate pathway to manage oxidative stress during metastasis. When pentose phosphate pathway function was impaired by reduced glucose 6-phosphate dehydrogenase (
G6PD
) function, melanoma cells increased malic enzyme activity and glutamine consumption. Melanoma cells thus have redundant and layered protection against oxidative stress.
Variation of TNF modulates cellular immunity of gregarious and solitary locusts against fungal pathogen
Metarhizium anisopliae
Authors: Wang Yundan , Tong Xiwen , Yuan Shenglei , Yang Pengcheng , Li Ling , Zhao Yong , Kang Le
Published: February 2022

Significance

Ecological immunology addresses the interactions between host immunity and the environment. Locusts display density-dependent phase transitions between solitary and gregarious locusts. In control practices and laboratory bioassays, gregarious locusts always exhibit stronger resistance to fungal pathogens than solitary locusts. However, few studies have investigated the mechanism of altered immune switch in locusts. Here, we combined mathematical simulation and experimental studies to show that gregarious locusts inhibit tumor necrosis factor (TNF) to alter immune defense by enhancing humoral defense and reducing cellular defense, and high levels of TNF reduce the survival of solitary locusts. Our study provides an important cue for understanding cellular immunity variations in response to different population densities and for improving the control efficacy of locust plagues.
Place-making: From a Residents’ Initiative to a Participatory Effect: The Case Study of BOMBAST
Authors: Schulte Monique , de Heus Nicoline
Published: February 2022

This case study illustrates an organic bottom-up place-making process, which started with the initiative of a couple of residents who created an invented folktale as a gift to their community. Through the development of a fictional character, these residents intuitively tried to embody the place’s norms and values or, in other words, the DNA of the community. The challenge, however, was how to transform this single initiative into shared meaning-making, borne by the wider local community. Two trends, noted in place-making literature, are of significance for the case. First, the case shows that, in making the place more attractive to live, the focus should be on the intangible attributes— the cultural soul of the place. Secondly, the case illustrates, through the use of the Imagineering Design Methodology, how the wider community has been enabled to become co-producers and co-consumers in the place-making process. Moreover, by actively including disruptive voices, such as those locals who were critical in the enabling interventions, the place-making process evolved. The case, therefore, shows how these interventions led to a participatory effect.

VIU logo

WLCE logo

Information

Vancouver Island University World Leisure Centre of Excellence Main image: Stichting BOMBAST, 2020. Drawing by Clema van Bekhoven

© Monique Schulte – van Alphen and Nicoline de Heus2022
Energy–momentum tensor and duality symmetry of linearized gravity in the Fierz formalism
Authors: Tóth Gábor Zsolt
Published: February 2022

A formulation of linearized gravity in flat background, based on the Fierz tensor as a counterpart of the electromagnetic field strength, is discussed in detail and used to study fundamental properties of the linearized gravitational field. In particular, the linearized Einstein equations are written as first order partial differential equations in terms of the Fierz tensor, in analogy with the first order Maxwell equations. An energy–momentum tensor

(

T

lg

a
b

)

with favourable properties and exhibiting remarkable similarity to the standard energy–momentum tensor of the electromagnetic field is found for the linearized gravitational field.

T

lg

a
b

is quadratic in the Fierz tensor (which is constructed from the first derivatives of the linearized metric), traceless, and satisfies the dominant energy condition in a gauge that contains the transverse traceless (TT) gauge. It is further shown that in suitable gauges, including the TT gauge, linearized gravity in the absence of matter has a duality symmetry that maps the Fierz tensor, which is antisymmetric in its first two indices, into its dual. Conserved currents associated with the gauge and duality symmetries of linearized gravity are also determined. These currents show good analogy with the corresponding currents in electrodynamics.
Slab dielectric waveguide with randomly fluctuating refractive indices
Authors: Reyes-Romero Arturo , Cruz Anabel
Published: February 2022

The three-layer slab dielectric waveguide is perhaps the most basic structure for designing optical and electronic devices. Deterministic results, assuming constant refractive indices, on the propagation of an electromagnetic wave within this structure are well known and they are reported in papers and textbooks, however to the best of the authors knowledge, there are no works reported in the literature on the stochastic propagation. In order to describe the stochastic propagation, we propose a model in which the refractive indices are variables fluctuating randomly. Our main objective is to show the student the significant difference between the deterministic and stochastic response of the system, when constant or random refractive indices are considered. In particular the dispersion curves, the distribution of the fields and the energy flow are presented and discussed. Our results show that the asymmetry factor associated with the dispersion curves can be easily modified by means of the magnitude of the induced fluctuation. Another interesting property shows that both TE0 and TM0 fundamental modes propagate only for small fluctuations. In the core of the guide, the amplitude of the electric and magnetic fields exhibits damped oscillations due to the randomness of the system. The energy flow is high in the substrate region, but it is vanishing in the cladding region. We conclude that those deterministic results are a particular case of our stochastic results.
A bi-stable mechanism actuated by patterned permanent magnet and Cu-Ni integrated micro-coil
Authors: Wang Yue , Xie Jin , Zhang Fengtian , Tao Fenggang , Xiong Zhuang , Zhi Chao
Published: February 2022

This paper presents a bi-stable mechanism, which mainly consists of a suspended mass, a spacer and a bottom plate. Electromagnetic actuation is used for switching between two states (i.e. ‘On/Off’ state). The actuation is achieved via permanent magnet (PM) on the suspended mass and micro-coils embedded in the bottom plate. Different from spiral coil and central core in conventional design, micro-coils in this paper integrate Cu and Ni together as a whole, acting as both coil and ferromagnetic core. This integration simplifies the fabrication into one-mask process. Furthermore, chessboard patterned PM is utilized with Cu-Ni integrated micro-coils to generate enhanced force density. The bi-stable mechanism is designed, fabricated and experimentally characterized. Total size of this mechanism is 16 × 14 × 2 mm3. No power is needed for holding either of the state. Switching processes (both ‘On’ to ‘Off’ and ‘Off’ to ‘On’) can be realized with external acceleration of 24 G (gravity) and 37 G, respectively. Furthermore, resetting (i.e. ‘On’ to ‘Off’) can also be accomplished with 1.5 A current input.
Development of microfluidic flow cytometry capable of characterization of single-cell intrinsic structural and electrical parameters
Authors: Liang Hongyan , Zhang Yi , Chen Deyong , Li Yueying , Wang Yixiang , Wang Junbo , Chen Jian
Published: February 2022

Although single-cell intrinsic structural and electrical parameters (e.g. D
c of cell diameter, D
n of nuclear diameter, σ
cy of cytoplasmic conductivity and C
sm of specific membrane capacitance) are promising for cell-type classification, they cannot be obtained simultaneously due to structural limitations of previously reported flow cytometry. This paper presented a microfluidic flow cytometry made of a double T-type constriction channel plus a predefined fluorescence detection domain, capable of high-throughput characterizing single-cell D
c, D
n, σ
cy and C
sm leveraging a home-developed impedance-fluorescence model. As a demonstration, the microfluidic platform quantified D
c, D
n, σ
cy and C
sm from ∼10 000 individual cells of three well-established tumor cell lines of A549, SW620 and HeLa where successful rates of cell-type classification were estimated as 54.5 ± 1.3% (D
c), 68.9 ± 6.8% (D
c + D
n) and 84.8 ± 4.4% (D
c, D
n, σ
cy + C
sm) based on neural pattern recognition. Then D
c, D
n, σ
cy and C
sm derived from ∼10 000 single cells of K562 vs Jurkat of leukemia and SACC-LM vs CAL 27 of oral tumor were quantified and compared, where successful rates of cell-type classification were estimated as 87.3% (K562 vs Jurkat) and 79.5% (SACC-LM vs CAL 27), respectively. In summary, the microfluidic platform reported in this study could quantify single-cell intrinsic structural and electrical parameters simultaneously, leading to significant increases in successful rates of cell-type classification.
Asymmetric optical transmission of a metallic grating-incorporated Fabry–Pérot cavity
Authors: Abudula Aibibula , Sun Zhijun
Published: February 2022

In this report, we show a structure of metallic grating-incorporated Fabry–Pérot (F–P) cavity demonstrating asymmetric optical transmission (AOT) for all transmission modes. The asymmetric transmission basically arises from asymmetric coupling and decoupling of resonant surface plasmons (SPs) on both sides of the metallic grating with asymmetric media of different indices. Coupling of the SP mode with anti-resonance mode of the F–P cavity in orthogonal directions further optimizes transmission characteristics of the structure for asymmetric transmission. Particularly, a high contrast AOT is achieved by locating the SP resonance position at center of the anti-resonance band of the F–P cavity. Meanwhile, SP resonance modes induced at different interfaces/regions of the cavity structure influence the transmission properties. The AOT structure has no nanoapertures and critical requirements on profile of the grating surfaces for fabrication, and can be adapted to various optical systems.
Unbalanced distribution of electric current in underwater electrical wire array explosion
Authors: Liu Zhigang , Qian Dun , Xu Cong , Li Liuxia , Zou Xiaobing , Wang Xinxin
Published: February 2022

The uniformity of electric current distribution in a wire array and its unstable behavior during the process of underwater electrical explosion have been investigated. Two exploding wires in parallel were used in the experiments and the current waveforms flowing through each wire were obtained using two self-integrating coils. Significant differences in the current waveforms of the two wires were observed near the melting point, which was attributed to the non-simultaneity of heating and phase transition. Unbalanced current distribution caused by the deviations of wire dimensions was analyzed based on a magneto-hydrodynamic model, and the simulation results show that thermodynamic state difference between two wires is present throughout the entire electrical explosion process. It is also found that the initial stored energy of pulse generator will affect the thermodynamic state evolution of exploding wires, resulting in different behaviors of current distribution after the explosion time. The slightly different heating rate caused by unbalanced current distribution in a wire array can break the symmetry of converging shock waves and lower the pressure peak in the vicinity of implosion axis, which was discussed based on the two-dimensional hydrodynamic simulations.
Stray field and combined effects on device miniaturization of the magnetic tunnel junctions
Authors: Cheng Chih-Wei , Chen Kuan-Ming , Wei Jeng-Hua , Hsin Yu-Chen , Sheu Shyh-Shyuan , Wu Chih-I , Tseng Yuan-Chieh
Published: February 2022

Magneto-static stray field (H
stray) interactions become an important issue when perpendicular CoFeB/MgO magnetic tunnel junctions (MTJs) are miniaturized. This raises the issue of which of the two mainstream etching processes, the pillar structure and the step structure, is better able to retain MTJ performance at extremely small scales. In the current study, we first simulated H
stray effects as a function of Ruderman–Kittel–Kasuya–Yosida strength within a synthetic antiferromagnetic structure for the two structures. Our results revealed that H
stray interactions were less influential (in terms of offset field) in step MTJs than in pillar MTJs during MTJ miniaturization. This is in good agreement with experimental results. This finding is further supported by adding Dzyaloshinskii–Moriya interactions into the free-layer of the two structures. We further simulated thermal stability with the inclusion of H
stray for 30 nm MTJs. We found that adding etching damage effects (i.e. assuming both anisotropy constant and saturation magnetization of the free layer had some degree of loss) into the model of the pillar MTJ was necessary to obtain a trend that is close to the experimental results of thermal stability. This information can provide some guidance on the technical choices for the MTJ miniaturization.
Invalidation of the acquisition of internal quantum efficiency using temperature-dependent photoluminescence in InGaN quantum wells with high threading dislocation density
Authors: Yu Jiadong , Wang Lai , Wang Jian , Hao Zhibiao , Luo Yi , Sun Changzheng , Han Yanjun , Xiong Bing , Li Hongtao
Published: February 2022

Temperature-dependent photoluminescence (TDPL) is mostly employed to evaluate the internal quantum efficiency (IQE) of light-emitting semiconductors. The key assumption of this method is that the IQE is 100% under low temperature (LT) (e.g. 10 K), which is often considered to be reasonable without any verification. This may lead to an obvious contradiction between a considerable IQE value and poor emission intensity, especially when there exists a high threading dislocation density. In this paper, the power-dependent photoluminescence (PDPL), TDPL, and time-resolved photoluminescence are carried out on three InGaN single-quantum-well samples with diverse threading dislocation densities to obtain the IQE and the recombination coefficients. It is found that the IQE at LT must be confirmed by PDPL and used to calibrate the TDPL values. Then, the IQEs obtained from different measurements are in good agreement under the same excitation conditions. A phenomenological model is proposed to explain the evolution of IQE and recombination coefficients with threading dislocation density. This work indicates that the commonly used TDPL is not reliable, as the hypothesis of negligible nonradiative recombination at LT is proven to not be valid for InGaN quantum well samples, especially those with high threading dislocation density (>1010 cm−2).
Fine structure of thermoluminescence assisted by molecular vibrations in disordered organic semiconductors
Authors: Sugakov V I
Published: February 2022

The article deals with the issue of the influence of a separate mode of molecular vibrations on the formation of the thermoluminescence from disordered systems with quasi-continuous spectra of localized carriers. The contribution of vibrations is noticeable if the energy of their quanta is close to the depth of some localized carriers and the transition of the carrier into the conductive region occurs via absorption of these quanta. At some value of a carrier–vibration interaction, the effect manifests itself in the appearance of a fine discrete structure on the generally smooth thermoluminescence curve. The thermoluminescence of polymers is calculated using the model of non-adiabatic transitions, in which the carrier–vibrational interaction is determined by the displacements of nuclei in the presence of the carrier. The dependence of the arising discrete structure of the thermoluminescence curve on a number of parameters of the system like the magnitude of the carrier–vibration interaction, the width of vibrational levels, the parameters of the conductive region is investigated. The processes with participation of multiple quanta of vibrations are investigated and the formation of repetitive structures on the thermoluminescence curve has been shown owing to the absorption of several vibrational quanta. Analysis of a number of experiments is presented using the suggested theory.
Tuning the semimetallic charge transport in the Weyl semimetal candidate Eu2Ir2O7 (111) epitaxial thin film with an all-in-all-out spin structure
Authors: Ghosh Mithun , Bhat Shwetha G , Pal Anand , Kumar P S Anil
Published: February 2022

We report the stoichiometric epitaxial growth of the Eu2Ir2O7 (111) thin film on YSZ substrate by a two-step solid phase epitaxy (SPE) method. An optimized post-annealing environment of the SPE was superior over the conventional air annealing procedure to get rid of the typical impurity phase, Eu2O3. The thickness-dependent structural study on Eu2Ir2O7 (111) thin films suggests a systematic control of Ir/Eu stoichiometry in our films, which is otherwise difficult to achieve. In addition, the low-temperature electrical resistivity studies strongly support the claim. The power-law dependence analysis of the resistivity data exhibits a power exponent of 0.52 in 50 nm sample suggesting possible disorder-driven semimetallic charge transport in the 3D Weyl semimetallic (WSM) candidate Eu2Ir2O7. In addition, the all-in-all-out/all-out-all-in antiferromagnetic domains of Ir4+ sublattice is verified using the field cooled magnetoresistance measurements at 2 K. Hall resistivity analysis indicate semimetallic hole carrier type dominance near the Fermi level up to the measured temperature range of 2–120 K. Altogether, our study reveals the ground state of stoichiometric Eu2Ir2O7 (111) thin film, with an indirect tuning of the off-stoichiometry using thickness of the samples, which is of interest in the search of the predicted 3D WSM phase.
Interface effects of Schottky devices built from MoS2 and high work function metals
Authors: Li Y D , Zhen W L , Weng S R , Hu H J , Niu R , Yue Z L , Xu F , Zhu W K , Zhang C J
Published: February 2022

Schottky junctions, formed by high work function metals and semiconductors, are important devices in electronics and optoelectronics. The metal deposition in traditional Schottky interfaces usually damages the semiconductor surface and causes defect states, which reduces the Schottky barrier height and device performance. This can be avoided in the atomically smooth interface formed by two-dimensional (2D) metals and semiconductors. For better interface tailoring engineering, it is particularly important to understand various interface effects in such 2D Schottky devices under critical or boundary conditions. Here we report the fabrication and testing of three types of MoS2 devices, i.e., using PtTe2, Cr and Au as contact materials. While the Cr/MoS2 contact is an ohmic contact, the other two are Schottky contacts. The van-der-Waals interface of PtTe2–MoS2 results in a well-defined OFF state and a significant rectification ratio of 104. This parameter, together with an ideality factor 2.1, outperforms the device based on evaporated Au. Moreover, a device in the intermediate condition is also presented. An abrupt increase in the reverse current is observed and understood based on the enhanced tunneling current. Our work manifests the essential role of doping concentration and provides another example for 2D Schottky interface design.
Anderson localization and multifractal spectrum at the transition point in a two-dimensional non-Hermitian AII† system
Authors: Yan Kun , Wang Yixian , Zhan Yuwei , Zhang Zhiyong , Wu Xinglong
Published: February 2022

The Anderson localization transition in a two-dimensional AII† system is studied by eigenvalue statistics and then confirmed by the multifractal analysis of the wave functions at the transition point. The system is modeled by a two-dimensional lattice structure with real-quaternion off-diagonal elements and complex on-site energies, whose real and imaginary parts are two independent random variables. Via finite-size scaling analysis of eigenvalue spacing ratios, we find the non-Hermiticity reduces the critical disorder and give an estimate of the critical exponent ν = 1.89, showing the system belongs to a new universal class other than the AII class and probably shares the same exponent with two-dimensional Hermitian DIII systems although they have different symmetries. The Anderson localization transition is further confirmed by checking the linearity in the parametric representation of the singularity strength and by checking the universality of the forms of the singularity spectra of different system sizes. The generalized dimensions are obtained as

D

1

=
1.80

and

D

2

=
1.62

.
Magnetic structures and electronic properties of cubic-pyrochlore ruthenates from first principles
Authors: Huebsch M-T , Nomura Y , Sakai S , Arita R
Published: February 2022

The magnetic ground states of R
2Ru2O7 and A
2Ru2O7 with R = Pr, Gd, Ho, and Er, as well as A = Ca, Cd are predicted devising a combination of the cluster-multipole (CMP) theory and spin-density-functional theory (SDFT). The strong electronic correlation effects are estimated by the constrained-random-phase approximation (cRPA) and taken into account within the dynamical-mean-field theory (DMFT). The target compounds feature d-orbital magnetism on Ru4+ and Ru5+ ions for R and A, respectively, as well as f-orbital magnetism on the R site, which leads to an intriguing interplay of magnetic interactions in a strongly correlated system. We find CMP + SDFT is capable of describing the magnetic ground states in these compounds. The cRPA captures a difference in the screening strength between R
2Ru2O7 and A
2Ru2O7 compounds, which leads to a qualitative and quantitative understanding of the electronic properties within DMFT.
A reinforcement transfer learning method based on a policy gradient for rolling bearing fault diagnosis
Authors: Wang Ruixin , Jiang Hongkai , Wu Zhenghong , Xu Jun , Zhang Jianjun
Published: February 2022

Accurate rolling bearing fault diagnosis is a basic guarantee of the safe operation of rotating machinery. Therefore, it is critical to select an appropriate fault diagnosis model. Selecting the optimal structure for intelligent fault diagnosis model has gradually become a research hot spot. At the same time, in practical engineering, sufficient data cannot always be guaranteed, which also increases the difficulty of accurate fault diagnosis. This paper proposes a reinforcement transfer learning method based on a policy gradient to identify the optimal structure of an intelligent fault diagnosis model when the number of training samples is insufficient. First, a policy gradient method is used to select the optimal child model in the source domain. Second, a transfer learning method is adopted to transfer the hyperparameters of the optimal child model from the source domain to the target domain. Finally, a small number of labeled training samples are used to fine-tune this model in the target domain. An adequate number of experiments proved the viability of proposed method, confirming the importance of the autonomous selection of a diagnostic model structure.
High-precision vapor pressure measurement apparatus with facile and inexpensive construction
Authors: Bhagwat Rohit , Sanadhya Sidharth , Gulotty Eva , Tucker Zachary , Ashfeld Brandon , Moghaddam Saeed
Published: February 2022

This study describes an apparatus for high-precision variable temperature measurement of liquid vapor pressure. The apparatus can be used to measure the vapor pressure using only 0.5 ml of the liquid sample. To evaluate the accuracy of the device measurement, water and 2-propanol are utilized as standard liquids, and their vapor pressure is measured with a maximum uncertainty of ∼1%. This apparatus can be replicated using inexpensive and commonly used laboratory fittings and fixtures, making it an indispensable tool for synthetic chemists and chemical engineers involved in the iterative synthesis of compounds, targeting different vapor–liquid equilibrium regimes.
Enhancement of the magnetic anisotropy in single semiconductor nanowires via surface doping and adatom deposition
Authors: Aras Mehmet , Güler-Kılıç Sümeyra , Kılıç Çetin
Published: February 2022

The magnetic anisotropy of single semiconductor (ZnO and GaN) nanowires incorporating both a transition metal (Co and Mn, respectively) as a substitutional surface dopant and a heavy metal (Au, Bi, or Pt) adatom is studied by performing density-functional supercell calculations with the Hubbard U correction. It is found that a substantial enhancement in the magnetic anisotropy energy is obtained through the deposition of Bi; the deposition of Au and Pt leads to significant variation in other magnetic properties, but not in the magnetic anisotropy energy. An analysis within a band description shows that the coexistence of Bi adatom and a surface dopant with large spin moment activates a mechanism involving reorientation and readjustment of the spin moments of electrons in occupied bands in response to the change of magnetization direction, which promotes giant magnetic anisotropy. Our results for adsorption energetics indicate that the accommodation of Bi in the neighborhood of the surface dopant is more likely in GaN nanowires, because the Bi adatom does (not) tend to be closer to the Mn (Co) dopant on the surface of GaN (ZnO) nanowire. The stability of GaN nanowire with giant magnetic anisotropy owing to the incorporation of both Mn and Bi is demonstrated by performing ab initio molecular dynamics simulations at temperatures considerably higher than room temperature. These results suggest that adatom deposition and surface doping can be used complementarily to develop single nanowire-based spintronic devices.
Versatile, rapid and robust nano-positioning of single-photon emitters by AFM-nanoxerography
Authors: Humbert M , Hallez Y , Larrey V , Fournel F , Palleau E , Paillard V , Cuche A , Ressier L
Published: February 2022

Atomic force microscopy (AFM) nanoxerography was successfully used to direct the assembly of colloidal nanodiamonds (NDs) containing nitrogen-vacancy (NV) centres on electrostatically patterned surfaces. This study reveals that the number of deposited NDs can be controlled by tuning the surface potentials of positively charged dots on a negatively charged background written by AFM in a thin PMMA electret film, yielding assemblies down to a unique single-photon emitter with very good selectivity. The mechanisms of the ND directed assembly are attested by numerical simulations. This robust deterministic nano-positioning of quantum emitters thus offers great opportunities for ultimate applications in nanophotonics for quantum technologies.
Impact of solid–liquid interfacial thermodynamics on phase-change memory RESET scaling
Authors: Lewis Matthew , Brush Lucien N
Published: February 2022

A model of the RESET melting process in conventional phase-change memory (PCM) devices is constructed in which the Gibbs–Thomson (GT) effect, representing local equilibrium at the solid–liquid interface, is included as an interfacial condition for the electro-thermal model of the PCM device. A comparison is made between the GT model and a commonly used model in which the interfacial temperature is fixed at the bulk melting temperature of the PCM material. The model is applied to conventional PCM designs in which a dome-shaped liquid/amorphous region is formed. Two families of solutions are computed representing steady state liquid regions, distinguished by their thermodynamic aspects. There is a family of solutions representing a hypothetical liquid nucleation process, and a family of larger steady-state liquid solutions representing the limit of the melting process. These ‘melting limits’ enable calculation of minima in voltage and corresponding current required for the RESET process. In this PCM configuration, the GT effect constrains the equilibrium solid–liquid interface temperature to remain above the bulk melting temperature during melting. The magnitude of this temperature difference increases with decreasing device size scale, thus requiring an increase in the required voltage and current needed for RESET compared to the case in which the interface temperature is approximated by the bulk melting temperature. This increase becomes substantial for active device dimensions in the <20 nm range. The impact of this phenomena on PCM device design is discussed.
Magneto-stimulation limits in medical imaging applications with rapid field dynamics
Authors: Grau-Ruiz Daniel , Rigla Juan P , Pallás Eduardo , Algarín José M , Borreguero José , Bosch Rubén , López-Comazzi Guillermo , Galve Fernando , Díaz-Caballero Elena , Gramage Carlos , González José M , Pellicer Rubén , Ríos Alfonso , Benlloch José M , Alonso Joseba
Published: February 2022

Objective. The goal of this work is to extend previous peripheral nerve stimulation (PNS) studies to scenarios relevant to magnetic particle imaging (MPI) and low-field magnetic resonance imaging (MRI), where field dynamics can evolve at kilo-hertz frequencies. Approach. We have constructed an apparatus for PNS threshold determination on a subject’s limb, capable of narrow and broad-band magnetic stimulation with pulse characteristic times down to 40 μs. Main result. From a first set of measurements on 51 volunteers, we conclude that the PNS dependence on pulse frequency/rise-time is compatible with traditional stimulation models where nervous responses are characterized by a rheobase and a chronaxie. Additionally, we have extended pulse length studies to these fast timescales and confirm thresholds increase significantly as trains transition from tens to a few pulses. We also look at the influence of field spatial distribution on PNS effects, and find that thresholds are higher in an approximately linearly inhomogeneous field (relevant to MRI) than in a rather homogeneous distribution (as in MPI). Significance. PNS constrains the clinical performance of MRI and MPI systems. Extensive magneto-stimulation studies have been carried out recently in the field of MPI, where typical operation frequencies range from single to tens of kilo-hertz. However, PNS literature is scarce for MRI in this fast regime, relevant to small (low inductance) dedicated MRI setups, and where the resonant character of MPI coils prevents studies of broad-band stimulation pulses. This work advances in this direction.
Impact of the electrode proximity on the streamer breakdown and development of pulsed dielectric barrier discharges
Authors: Wubs J R , Höft H , Kettlitz M , Becker M M , Weltmann K-D
Published: February 2022

The impact of the electrode proximity on the streamer breakdown and development of pulsed-driven dielectric barrier discharges (DBDs) in a single-filament arrangement has been investigated in a gas mixture of 0.1 vol% O2 in N2 at 0.6 bar and 1.0 bar. The gap distance was varied from 0.5 mm to 1.5 mm, and the applied voltage was adapted correspondingly to create comparable breakdown conditions in the gap. The development of the DBDs was recorded by an iCCD and a streak camera system, while fast electrical measurements provided insight into discharge characteristics such as the transferred charge and consumed energy. The results demonstrate that breakdown in a smaller gap is characterised by a slower streamer propagation but a significantly higher acceleration. It can therefore be concluded that the proximity of the cathode has a strong impact on the characteristics of the streamer breakdown. However, after the streamer has crossed the gap, the discharge structure in front of the anode was found to be the same independent of the actual gap distance.
High-dimensional data analytics in structural health monitoring and non-destructive evaluation: a review paper
Authors: Momeni Hamed , Ebrahimkhanlou Arvin
Published: February 2022

This paper aims to review high-dimensional data analytic (HDDA) methods for structural health monitoring (SHM) and non-destructive evaluation (NDE) applications. High-dimensional data is a type of data in which the number of features for each observation is much larger than the number of all observations. High-dimensional data may violate assumptions of the classic methods for statistical modeling and data analysis. Then, classic statistical modeling will no longer be applicable. HDDA methods were developed to overcome this challenge and analyze these types of data. In the field of SHM/NDE, there are several sources of high-dimensionality. Examples include a large number of data points in continuous waves/signals or high-resolution images/videos. HDDA methods are used as a dimension-reduction tool to preprocess data for further analysis, or they are directly implemented for damage detection and localization. This paper reviews six HDDA methods as well as existing and potential applications in SHM/NDE. Particularly, this paper discusses the vast range of implemented SHM/NDE applications from crack detection to missing data imputation. Furthermore, experimental and simulated datasets have been used to show the application of HDDA methods as hands-on examples. It is shown that the potential of HDDA for SHM/NDE studies is significantly more than the existing studies in the literature, and these methods can be used as a powerful tool that provides vast opportunities in SHM/NDE.
The T-A formulation: an efficient approach to model the macroscopic electromagnetic behaviour of HTS coated conductor applications
Authors: Huber Felix , Song Wenjuan , Zhang Min , Grilli Francesco
Published: February 2022

In recent years, the
T-A
formulation has emerged as an efficient approach for modelling the electromagnetic behaviour of high-temperature superconductor (HTS) tapes in the form of coated conductors (CCs). HTS CCs are characterized by an extremely large width-to-thickness ratio of the superconducting layer, normally up to 1000 ∼ 6000, which in general leads to a very large number of degrees of freedom. The
T-A
formulation considers the superconducting layer to be infinitely thin. The magnetic vector potential
A
is used to calculate the magnetic field distribution in all simulated domains. The current vector potential
T
is used to calculate the current density in the superconducting layer, which is a material simulated with a highly nonlinear power-law resistivity. This article presents a review of the
T-A
formulation. First, the governing equations are described in detail for different cases (2D and 3D, cartesian and cylindrical coordinates). Then, the literature on the implementation of
T-A
formulation for simulating applications ranging from simple tape assemblies to high field magnets is reviewed. Advantages and disadvantages of this approach are also discussed.
Protection of edge transport in quantum spin Hall samples: spin-symmetry based general approach and examples
Authors: Yevtushenko Oleg M , Yudson Vladimir I
Published: February 2022

Understanding possible mechanisms, which can lead to suppression of helical edge transport in quantum spin Hall (QSH) systems, attracted huge attention right after the first experiments revealing the fragility of the ballistic conductance. Despite the very intensive research and the abundance of theoretical models, the fully consistent explanation of the experimental results is still lacking. We systematize various theories of helical transport with the help of the spin conservation analysis which allows one to single out setups with the ballistic conductance being robustly protected regardless of the electron backscattering. First, we briefly review different theories of edge transport in the QSH samples with and without the spin axial symmetry of the electrons including those theoretical predictions which are not consistent with the spin conservation analysis and, thus, call for a deeper study. Next, we illustrate the general approach by a detailed study of representative examples. One of them addresses the helical edge coupled to an array of Heisenberg-interacting magnetic impurities (MIs) and demonstrates that the conductance remains ballistic even if the time-reversal symmetry on the edge is (locally) broken but the total spin is conserved. Another example focuses on the effects of the space-fluctuating spin–orbit interaction on the QSH edge. It reveals weakness of the protection in several cases, including, e.g. the presence of either the U(1)-symmetric, though not fully isotropic, MIs or generic electron–electron interactions.
Modeling of second-order nonlinear metasurfaces
Authors: Achouri Karim , Kiselev Andrei , Martin Olivier J F
Published: February 2022

We present a frequency-domain modeling technique for second-order nonlinear metasurfaces. The technique is derived from the generalized sheet transition conditions (GSTCs), which have been so far mostly used for modeling linear metasurfaces. In this work, we extend the GSTCs to include effective nonlinear polarizations. This allows retrieving the effective nonlinear susceptibilities of a given metasurface and predict its nonlinear scattering responses under arbitrary illumination conditions. We apply this modeling technique to the case of metasurfaces made of a periodic arrangement of T-shaped gold nanoparticles. For verification, several metasurfaces are fabricated and a fair agreement is found when comparing simulated data and experimental results. The proposed model may thus serve as a design platform to implement complex nonlinear metasurface based applications.
Weyl–Wigner description of massless Dirac plasmas: ab initio quantum plasmonics for monolayer graphene
Authors: Figueiredo José L , Bizarro João P S , Terças Hugo
Published: February 2022

We derive, from first principles and using the Weyl–Wigner formalism, a fully quantum kinetic model describing the dynamics in phase space of Dirac electrons in single-layer graphene. In the limit ℏ → 0, we recover the well-known semiclassical Boltzmann equation, widely used in graphene plasmonics. The polarizability function is calculated and, as a benchmark, we retrieve the result based on the random-phase approximation. By keeping all orders in ℏ, we use the newly derived kinetic equation to construct a fluid model for macroscopic variables written in the pseudospin space. As we show, the novel ℏ-dependent terms can be written as corrections to the average current and pressure tensor. Upon linearization of the fluid equations, we obtain a quantum correction to the plasmon dispersion relation, of order ℏ
2, akin to the Bohm term of quantum plasmas. In addition, the average variables provide a way to examine the value of the effective hydrodynamic mass of the carriers. For the latter, we find a relation in which Drude’s mass is multiplied by the square of a velocity-dependent, Lorentz-like factor, with the speed of light replaced by the Fermi velocity, a feature stemming from the quasi-relativistic nature of the Dirac fermions.
Reversible control of the metal-insulator transition in V2O3 thin films through plasma hydrogenation
Authors: Sultan M T , Arnalds U B
Published: February 2022

We investigate the effect of hydrogen plasma treatment on the metal-insulator transition (MIT) of epitaxial V2O3 films grown on c-Al2O3. The films were exposed to plasma at constant power for varying intervals. With increasing hydrogenation the films display a suppression of the MIT magnitude and temperature due to neutralization of structural defects and passivation of unpaired bonds by incorporation of atomic hydrogen as supported by relaxation in strain by XRD and Raman spectroscopy analysis, while stabilizing the metallic phase due to reduction in Peierls dimerization of V-V bonds. Heating to 350-400 °C the electrical characteristics of the film in the as-grown state are regained showing the possibility of reversibly controlling the MIT characteristics.