Junction Model Research Articles

Timing and Nd-Hf isotopic mapping of early Mesozoic granitoids in the Qinling Orogen, central China: Implication for architecture, nature and processes of the orogen

The Qinling orogen, one of the most important orogens in Asia, belongs to the northeastern part of the Tethyan orogen. The architecture and processes of the Qinling orogen remain controversial. In this study, we present 15 new zircon U–Pb ages, 20 whole-rock geochemical and 46 Sm-Nd isotopic analyses, and 30 zircon Lu–Hf isotopic data for early Mesozoic granitoids in this orogen, combining with data from literature, to delineate the crustal architecture and processes of the orogen. A total of 181 zircon U–Pb ages show three phase (252–230, 230–198, and 190–185 Ma) of granitoids. The first-phase granitoids occur mainly in the westernmost segment of the orogen and formed in a subduction setting during the closure of the Mianlue Ocean (a northern branch of the Paleo-Tethyan Ocean). The second- and third-phase granitoids, distributed in the middle to eastern parts of the Qinling orogen, were generated in late syn-collisional and post-collisional tectonic settings, respectively. Whole-rock Nd and zircon Hf isotopic mapping of these granitoids yield six and seven isotopic provinces, respectively. These provinces display that the southern margin of the North China Block and the northern margin of the South China Block are dominated by ancient deep crust, that is, early Paleoproterozoic (2.3–1.8 Ga) and late Paleoproterozoic (∼1.7 Ga) components, respectively. By way of camparison, the North Qinling contains younger Mesoproterozoic [eNd(t) = −10.7 to −0.2; TDM = 1.4–1.0 Ga] basement, evidencing that it is an independent terrane different from the North China Block. The isotopic mapping also reveals a deep-seated NNE–SSW-trending zoned architecture that is approximately perpendicular to the WNW–ENE-trending of the orogen. This provides new evidence for the “Spaghetti Junction model” for the Qinling orogen. The old Nd (2.2–1.0 Ga, mostly 2.0–1.2 Ga) and Hf (2.3–0.8 Ga, mostly 2.0–1.2 Ga) model ages indicate that the continental growth in this orogen occurred mainly during the Paleoproterozoic and Mesoproterozoic, with only minor amounts of juvenile [eNd(t) = ∼0, TDM = ∼0.1 Ga] continental growth along the Shangdan and Mianlue sutures. These characteristics suggest that the Qinling orogen is dominantly formed by the collision of ancient continental blocks, distinct from some typical accretionary orogens, such as the Central Asian Orogenic Belt with voluminous juvenile crust.

Simplification of deep reinforcement learning in traffic control using the Bonsai Platform

The paper deals with the problem of traffic light control of road intersection. The authors use a model of a real road junction created in the AnyLogic modelling tool. For two scenarios, there are three simulation experiments performed ? fixed time control, fixed time control after AnyLogic-based optimizations, and dynamic control obtained through the cooperation of the AnyLogic tool and the Bonsai platform, utilizing benefits of deep reinforcement learning. At present, there are trends to simplify machine learning processes as much as possible to make them accessible to practitioners with no artificial intelligence background and without the need to become data scientists. Project Bonsai represents an easy-to-use connector, that allows to use AnyLogic models connected to the Bonsai platform - a novel approach to machine learning without the need to set any hyper-parameters. Due to unavailability of real operational data, the model uses simulation data only, with presence and movement of vehicles only (no pedestrians). The optimization problem consists in minimizing the average time that agents (vehicles) must spend in the model, passing the modelled intersection. Another observed parameter is the maximum time of individual vehicles spent in the model. The authors share their practical, mainly methodological, experiences with the simulation process and indicate economic cost needed for training as well.

JUNÇÃO E TRADIÇÃO DISCURSIVA NA ESCRITA INFANTIL

Neste artigo, propõe-se uma abordagem descritivo-comparativa do funcionamento dos mecanismos de junção nas tradições discursivas (TDs) relato de experiência e carta de opinião, no modo escrito de enunciação. Com o objetivo de alcançar indícios que apontem a relação sintomática entre mecanismos de junção e TDs, o estudo fundamenta-se no modelo funcionalista de junção (RAIBLE, 2001), conjugado a uma base teórica que entende a escrita como constitutivamente heterogênea (CORRÊA, 2004) e a uma concepção de texto que considera as TDs que o constituem (KABATEK, 2006). Nesse quadro teórico-metodológico, a descrição da escrita infantil é pautada na consideração de aspectos linguísticos e discursivos, que permitem o reconhecimento, por meio do funcionamento dos MJs, de rastros do movimento do sujeito pelo que (re)conhece como fixo e lacunar do texto. Os resultados mostram que a textualização ocorre por meio dessa circulação do sujeito, em intrínseca associação àquilo que imagina ser a (sua) escrita, no processo de atualização da tradição. As especificidades da movimentação indiciada por esses rastros apontam, ao mesmo tempo, para o geral e o particular, a partir do que é fixo e lacunar nas tradições em que se inserem e lançam luz sobre a relação sintaxe-texto-discurso.

Light Cross-Linkable Marine Collagen for Coaxial Printing of a 3D Model of Neuromuscular Junction Formation.

Collagen is a major component of the extracellular matrix (ECM) that modulates cell adhesion, growth, and migration, and has been utilised in tissue engineering applications. However, the common terrestrial sources of collagen carry the risk of zoonotic disease transmission and there are religious barriers to the use of bovine and porcine products in many cultures. Marine based collagens offer an attractive alternative and have so far been under-utilized for use as biomaterials for tissue engineering. Marine collagen can be extracted from fish waste products, therefore industry by-products offer an economical and environmentally sustainable source of collagen. In a handful of studies, marine collagen has successfully been methacrylated to form collagen methacrylate (ColMA). Our work included the extraction, characterization and methacrylation of Red Snapper collagen, optimisation of conditions for neural cell seeding and encapsulation using the unmodified collagen, thermally cross-linked, and the methacrylated collagen with UV-induced cross-linking. Finally, the 3D co-axial printing of neural and skeletal muscle cell cultures as a model for neuromuscular junction (NMJ) formation was investigated. Overall, the results of this study show great potential for a novel NMJ in vitro 3D bioprinted model that, with further development, could provide a low-cost, customizable, scalable and quick-to-print platform for drug screening and to study neuromuscular junction physiology and pathogenesis.

Optimal conditions for observing fractional Josephson effect in topological Josephson junctions

Topological Josephson junctions (JJs), which contain Majorana bound states, are expected to exhibit 4$\pi$-periodic current-phase relation, thereby resulting in doubled Shapiro steps under microwave irradiation. We performed numerical calculations of dynamical properties of topological JJs using a modified resistively and capacitively shunted junction model and extensively investigated the progressive evolution of Shapiro steps as a function of the junction parameters and microwave power and frequency. Our calculation results indicate that the suppression of odd-integer Shapiro steps, i.e., evidence of the fractional ac Josephson effect, is enhanced significantly by the increase in the junction capacitance and IcRn product as well as the decrease in the microwave frequency even for the same portion of the 4$\pi$-periodic supercurrent. Our study provides the optimal conditions for observing the fractional ac Josephson effect; furthermore, our new model can be used to precisely quantify the topological supercurrent from the experimental data of topological JJs.

Cryo-electron tomography structure of Arp2/3 complex in cells reveals new insights into the branch junction

The actin-related protein (Arp)2/3 complex nucleates branched actin filament networks pivotal for cell migration, endocytosis and pathogen infection. Its activation is tightly regulated and involves complex structural rearrangements and actin filament binding, which are yet to be understood. Here, we report a 9.0 Å resolution structure of the actin filament Arp2/3 complex branch junction in cells using cryo-electron tomography and subtomogram averaging. This allows us to generate an accurate model of the active Arp2/3 complex in the branch junction and its interaction with actin filaments. Notably, our model reveals a previously undescribed set of interactions of the Arp2/3 complex with the mother filament, significantly different to the previous branch junction model. Our structure also indicates a central role for the ArpC3 subunit in stabilizing the active conformation.

Numerical and experimental study of the 3D flow in a graft-artery junction model

Vascular graft occlusion after implantation is one of the most urgent problems of vascular surgery. This paper presents results of numerical simulation and ultrasound/strain gauge measurements of the 3D pulsating flow of blood-mimicking fluid in a model of the junction of the graft with superficial femoral artery. The calculations have pointed, in particular, at occurrence of an extensive stagnant zone with low wall shear stresses near the graft-artery junction, which can accelerate the graft occlusion. Both the simulation and the ultrasound measurements have shown that a four-vortex flow structure forms just after the graft-artery junction zone, which transforms into a two-vortex flow structure further downstream. Numerical and experimental data on the pressure drop at the graft-artery junction model were in a good accordance.

Transport and Noise Properties of sub-100-nm Planar Nb Josephson Junctions with Metallic Hf - Ti Barriers for nano-SQUID Applications

We analyze electric transport and noise properties at 4.2 K of self-shunted superconductor-normal metal-superconductor (SNS) sandwich-type Josephson junctions, comprising $\mathrm{Nb}$ as the superconductor and $\mathrm{Hf}$-$\mathrm{Ti}$ as the normal conducting material, with lateral dimensions down to approximately $80$ nm. The junctions are fabricated with an optimized multilayer $\mathrm{Nb}$ technology based on nanopatterning by electron-beam lithography and chemical-mechanical polishing. The dependence of transport properties on the junction geometry (lateral size and barrier thickness ${d}_{\mathrm{Hf}\mathrm{\ensuremath{-}}\mathrm{Ti}}$) is studied, yielding a characteristic voltage ${V}_{c}$ up to approximately $100\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{V}$ for the smallest ${d}_{\mathrm{Hf}\mathrm{\ensuremath{-}}\mathrm{Ti}}=17$ nm. The observed small hysteresis in the current-voltage curves of devices with high ${V}_{c}$ and large size can be attributed to self-heating of the junctions and fitted with an extended version of the resistively shunted junction model. Measurements of voltage noise of single junctions are consistent with the model including self-heating effects. The potential of our technology for further miniaturization of nanoscale superconducting quantum interference devices and for the improvement of their performance is discussed.

A Naghdi Type Nonlinear Model for Shells with Little Regularity

In this paper a new nonlinear two-dimensional shell model of Naghdi’s type is formulated for shells which middle surface is parameterized by a $W^{1, \infty}$ function. Therefore the model inherently contains undeformed geometries with corners, so the model also includes models of junctions of nonlinear shells. Deformation of the shell is described by a pair $(\boldsymbol{\psi}, {\mathbf{R}})$ of independent unknowns, where $\boldsymbol{\psi}$ is the deformation of the middle surface and ${\mathbf{R}}$ is a function with value in rotations that describes rotation of the shell cross-section. The model is formulated as the minimization problem for the total energy functional that includes flexural, membrane, shear and drill energies differently scaled with respect to the thickness of the shell. We relate the new model for smooth enough undeformed geometry to the known shell models in two ways. First we restrict the proposed model on two particular subsets of admissible functions and obtain exactly the flexural shell model and a perturbation of the Koiter shell model. More important, we consider asymptotics, using $\Gamma$ –convergence, of the proposed model with respect to the thickness as a small parameter in the membrane and flexural regime and obtain exactly the nonlinear membrane and flexural shell model obtained as $\Gamma$ –limits starting from nonlinear three–dimensional elasticity. In that way we link rigorously the proposed model with the nonlinear three–dimensional elasticity.

Proximitized Josephson junctions in highly-doped InAs nanowires robust to optical illumination

We have studied the effects of optical-frequency light on proximitized InAs/Al Josephson junctions based on highly n-doped InAs nanowires at varying incident photon flux and at three different photon wavelengths. The experimentally obtained IV curves were modeled using a resistively shunted junction model which takes scattering at the contact interfaces into account. Despite the fact that the InAs weak link is photosensitive, the Josephson junctions were found to be surprisingly robust, interacting with the incident radiation only through heating, whereas above the critical current our devices showed non-thermal effects resulting from photon exposure. Our work indicates that Josephson junctions based on highly-doped InAs nanowires can be integrated in close proximity to photonic circuits. The results also suggest that such junctions can be used for optical-frequency photon detection through thermal processes by measuring a shift in critical current.

Microwave Photon Detection Using a Topological Josephson Junction

Single photon detection (SPD) has found increasingly important applications in many forefront areas of fundamental science and advanced engineering applications, ranging from studying the galaxy formation though cosmic infrared background to entanglement of superconducting qubits, single molecular spectroscopy, and remote sensing. In recent years, the rapid developments in superconducting quantum computation, high fidelity quantum measurement, quantum key distribution, and quantum network call for SPD in the microwave frequency range.In this talk, I will first present our recent experimental work on topological Josephson junctions in Dirac semimetal Cd3As2. In high quality aluminum-Cd3As2-aluminum Josephson junctions, we observe both π and 4π periodic supercurrents. The π period is manifested by both the magnetic-field dependence of the critical supercurrent and the appearance of half-integer Shapiro steps in the ac Josephson effect. Our simulation by a resistively shunted junction model suggests that the π period arises from interference between the induced bulk superconductivity and the induced Fermi-arc surface superconductivity. In the second part of the talk, I will discuss microwave photon detection using these topological Josephson junctions. The temperature dependence and microwave power dependence of the junction resistance are studied. It is observed the effective temperature of the junction device under microwave radiation increases with microwave power, suggesting a promising potential for photon number-resolving capability.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under Contract No. DE-NA-0003525.

Research on wind barrier of canyon bridge-tunnel junction based on wind characteristics

Due to the acceleration effect of the wind by the special geographical location of the canyon bridge-tunnel junction, the traffic safety and stability of this section are difficult to be guaranteed, resulting in frequent traffic accidents. In order to ensure the safety and comfort of vehicles driving on this section, the numerical simulation method based on CFD is adopted to establish the numerical model of the canyon bridge-tunnel junction. The acceleration of the incoming wind speed in the bridge-tunnel junction with a guardrail that is 0.8 m high is analyzed from different canyon spacings, wind directions and heights from the bridge deck. Based on the characteristics of wind field above the bridge deck, two kinds of gradient wind barriers—trapezoidal and stepped—are proposed, and their wind reduction effects and turbulence intensity changes are analyzed. Then the aerodynamic performances of running vehicle are compared. The results show that the stepped wind barrier with 50% porosity and rectangular section railings has the best wind reduction effects, and can noticeably improve the comfort of driving. The aerodynamic coefficients of vehicle are lower with stepped wind barrier.

Use of carrier injection engineering to increase the light intensity of a polycrystalline silicon avalanche mode light-emitting device

This paper demonstrates a polycrystalline silicon avalanche mode light-emitting device. The unique N+PN+PN+ cascade structure is designed to enhance light intensity via carrier injection engineering, in which the minority carriers are injected from the forward-biased junction to the light emission junction. Visible light can be observed at the reverse-biased PN junctions when the device operating voltage exceeds 20 V. In particular, the phonon-assisted indirect interband recombination of carriers with excess energy may be the main mechanism of photon emission. A specific junction model is proposed to explain that the light intensity peaks are generated primarily via carrier injection. Comparing the spectral measurements of a single polysilicon N+P junction device and the proposed cascade device shows that the strategy of improving the luminous intensity via carrier injection engineering is feasible and effective.

A density-functional theory study of the Al/AlOx/Al tunnel junction

The aluminum oxide tunnel junction is a key component of the majority of superconducting quantum devices. For high-quality, reproducible, and scalably manufacturable qubits, the ability to fabricate Josephson junctions (JJs) with a targeted critical current and high uniformity is essential. We use first-principles modeling to assess fundamental aspects of the atomic structure of both amorphous and crystalline aluminum oxide tunnel junctions and relate the structure to predicted performance metrics. We use modified ab initio molecular dynamics to develop realistic models of the tunnel junction, from which interface roughness and local thickness fluctuations are analyzed in an unbiased manner by training a neural network to identify the boundary between metal and oxide. We show that the effective thickness of the insulating part of the junction can be different from the apparent physical thickness. We calculate the rate of Cooper pair tunneling for the atomically resolved electrostatic potential using direct numerical solution in 3D, which shows a channeling effect that impacts the junction critical current. The predicted critical current is a useful JJ design parameter that can be accessed from the ab initio calculations without fitting parameters. To assess the limits of uniformity and fabrication choices (e.g., oxidation vs epitaxy), we compare the amorphous junctions to crystalline models, which show order of magnitude more efficient tunneling compared to the amorphous case, underlining the connection between atomistic structure and Cooper pair tunneling efficiency. Further, this work provides a foundation for ab initio materials design and evaluation to help accelerate future development of improved tunnel junctions.

Development of an in vitro model of the dentogingival junction using 3D organotypic constructs.

The overall aim was to propose a plausible model of the dentogingival junction (DGJ) to deepen our understanding of the extrinsic influences responsible for the development of the junctional epithelial phenotype. The specific objective was to test the hypothesis that epithelial migration and proliferation would be inhibited by periodontal ligament (PDL) fibroblasts in an in vitro model of the DGJ consisting of 3D organotypic cultures. Previously, we showed that 3D organotypic cultures containing human gingival fibroblasts (HGF) supported the development of a multi-layered epithelium, while constructs containing human periodontal ligament fibroblasts (HPDLF) resulted in epithelial atrophy (Lu EMC, Hobbs C, Dyer CJ, Ghuman M, Hughes FJ. J Perio Res., 2020). However, changes in epithelial phenotype have not been studied within an in vitro model of the DGJ. The in vitro model of the DGJ comprised of a donor HGF construct (H400 epithelium overlying HGF-collagen matrix) supported by a dimensionally larger recipient collagen bed enriched with HPDLF. Samples were harvested, fixed and processed for immunohistochemistry. The changes in epithelial migration and proliferation following contact with HPDLF were assessed by measuring the horizontal extension of the epithelial outgrowth on the recipient collagen matrix. Within our in vitro model of the DGJ, epithelial migration and proliferation were inhibited following contact with the recipient HPDLF. By contrast, the control set-up showed a relative increase in epithelial growth, where the epithelium came into contact with the recipient HGF. Overall, there were limited changes in the molecular expression of keratin markers. This study has proposed a plausible in vitro model of the DGJ to illustrate the role of different fibroblasts in the regulation of dentogingival epithelia. Furthermore, it suggests that the anatomical positional stability of the JE and its apparent resistance to apical migration could be associated with its interaction with the PDL.

Estimation of rock load for junctions based on roof failure cases for safe mining operation

Coal mine roadway junctions in bord and pillar mining, in particular, are more vulnerable to roof fall due to the excavation induced stresses as well as general stress loading pattern inherent to the typical cross section achieved in practice. Roof fall incidences are generally more in junctions of development galleries and a cause of concern as they provide access to faces in different directions (dip/rise). The CMRI-ISM rock mass classification system, popularly known as Rock Mass Rating (RMR), is being used for the design of support system in underground coal mines for the last 30 years in India. In spite of the well-defined guidelines, it has been observed that roof failures are still a major concern in many underground coal mines. In this research, an attempt has been made to develop a new rock load prediction model for junctions of bord and pillar workings based on the geoengineering investigations carried out in 63 coal mines. After analysis of failure and stable cases, a best suited rock load predictor equation was developed. Analysis indicated that the maximum roof failure cases occurred for RMR values in between 30 and 45, and this zone is considered as highly unstable zone. Assessment of stable and unstable class is also done with respect to rock load for varied RMR. A general support design has also been suggested as per the RMR and severity of the roof fall. The suggested approach can help designing a rational support system for underestimated and overestimated zones thus minimising the roof fall cases leading to improved safety and productivity in underground coal mines.

Compact Model of Magnetic Tunnel Junctions for SPICE Simulation Based on Switching Probability

Compact Model of Magnetic Tunnel Junctions for SPICE Simulation Based on Switching Probability

Lighting up the NMJ: developing an LED-based model of the neuromuscular junction for the undergraduate classroom.

Many complex physiological processes can be introduced and explored using the framework of the neuromuscular junction (NMJ), including neurotransmitter release, membrane depolarization, and ion channel activity. While traditionally used instructional tools such as static complex drawings are useful, these images can be incomplete physiological representations due to the lack of physically moving parts. As a result, they often misrepresent the complexity of physiological phenomena to students. We describe an effort to create a more accurate, dynamic representation of the NMJ to enhance instruction in an undergraduate anatomy and physiology course. We sought to create a unique and memorable moving diagram that combines elements of static images with moving parts. To evaluate the impact of the dynamic model, students were asked about their understanding of the NMJ before and after exposure to the model. In addition, students were asked for attitudinal responses to the model and their preferred method of instruction. Analysis of student responses indicated that students enjoyed the model, although they also had concerns about the speed of the simulated ion movement being too fast. The model has also served as an informal science education art installation in presentations for prospective students, stakeholders in the broader community, including local and statewide politicians, the University president and board of trustees, donors, and other regional economic and educational leaders.

Self-equilibration theorem in quantum-point contacts of interacting electrons: Time-dependent quantum fluctuations of tunnel transport beyond the Levitov–Lesovik scattering approach

Equilibration to the steady state for a wide class of Luttinger liquid ballistic weakly linked tunnel contacts is extensively studied. Quantum fluctuations of tunnel current are considered in all orders in tunnel coupling and out of the equilibrium in the time domain. Especially, two important mathematical statements: Self-equilibration (SE-)theorem and Self-equilibration (SE-)lemma on the exact re-exponentiation of thermal average from the Keldysh-contour-ordered evolution operator for arbitrary weakly linked Luttinger liquid tunnel contact are proven. Demonstrated proof of SE-theorem and SE-lemma represents first evidence of a novel emergent phenomenon of ”self-equilibration” in the dynamics of quantum fluctuations of electron transport through ballistic tunnel junctions. This phenomenon and all related real-time full counting statistics are shown to be much more general as compared to the usual Levitov–Lesovik scattering approach for the non-interacting electrons, though SE-theorem also contains known results obtained within the Levitov–Lesovik scattering approach as corresponding limiting case for lowest order cumulants at g=1. As the result, corresponding differential equation of ”self-equilibration” for time-dependent Keldysh partition function of tunnel contact is derived and explained. It is shown that proven SE-theorem can be considered also as the dynamical version of well-known Jarzynski equality for the tunnel electron transport out of the equilibrium. As the result, for arbitrary weakly linked tunnel junction model of interest the exact time-dependent cumulant generating functional is derived being valid at arbitrary electron–electron repulsion in the Luttinger liquid leads of the junction, arbitrary temperature and arbitrary bias voltage. Respective general formula in its long-time asymptote turns into a non-perturbative Luttinger liquid generalization of the Levitov–Lesovik type of detailed balance formula for cumulant generating function. As the consequence of obtained results, a universal character of self-equilibration of tunnel current in one-dimensional weakly linked tunnel junctions is revealed and studied on the level of non-equilibrium Fano factor. As well, a new measure of disequilibrium in such systems – the ”steady flow” rate – is also introduced and discussed.

Fractional Shapiro steps in resistively shunted Josephson junctions as a fingerprint of a skewed current-phase relationship

We study numerically the fractional Shapiro step response in low-frequency driven Josephson junctions which have a nonsinusoidal current-phase relation. We perform this study within the resistively shunted Josephson junction model. We demonstrate that fractional steps, as a fingerprint of a skewed current phase relation, will manifest themselves only for higher values of the reduced frequency. We compare the theoretical observations with experimental measurements in an anisotropic Josephson junction array containing over 500 superconductor-normal-superconductor junctions having a skewed current phase relation. We demonstrate that changing the critical current by applying a magnetic field is a robust method to modify the reduced frequency over a broad range of values. The presence of fractional Shapiro steps at high values of the reduced frequency directly confirm the theoretical results.