bluuebunny/crossref_metadata_2025 huggingface dataset:
Brain Growth Evaluation Assessed with Transfontanellar (B-GREAT) Ultrasound. Old and New Bedside Markers to Estimate Cerebral Growth in Preterm Infants: a Pilot Study
Authors: Arena Roberta , Gallini Francesca , De Rose Domenico Umberto , Conte Francesca , Giraldi Luca , Pianini Teresa , Perri Alessandro , Catenazzi Piero , Orfeo Luigi , Vento Giovanni , Govaert Paul
Published: November 2021

Objective We aimed to investigate the feasibility of evaluating overall preterm brain growth using a gathered set of measurements of brain structures in standard cranial ultrasound planes. We called this method of assessment Brain Growth Evaluation Assessed with Transfontanellar ultrasound (B-GREAT).

Study design In this prospective observational cohort study, cranial ultrasound was regularly performed (on day 1, 2, 3, and 7 of life, and then weekly until discharge, and at term) in preterm infants born with gestational age (GA) less than 32 weeks. We evaluated corpus callosum length, corpus callosum–fastigium length, anterior horn width, frontal white matter height, total brain surface, deep grey matter height, hemisphere height, transverse cerebellar diameter in the axial view, and transverse cerebellar diameter coronal view. Measurements obtained were used to develop growth charts for B-GREAT markers as a function of postmenstrual age. Reproducibility of B-GREAT markers was studied.

Results A total of 528 cranial ultrasounds were performed in 80 neonates (median birth GA: 28+5 weeks and interquartile range: 27+3–30+5). The intraclass correlation coefficients for intra-observer and inter-observer analyses showed substantial agreement for all B-GREAT markers. Growth curves for B-GREAT markers were developed.

Conclusion B-GREAT is a feasible and reproducible method for bedside monitoring of the growth of the main brain structures in preterm neonates.

Key Points
Maternal COVID-19 Infection and Possible Associated Adverse Neurological Fetal Outcomes, Two Case Reports
Authors: Archuleta Charlotte , Wade Christine , Micetic Becky , Tian Ashley , Mody Kartik
Published: November 2021

Introduction The long-term effects of prenatal coronavirus disease 2019 (COVID-19) infection on the fetal brain are mostly unknown at this time; however, there is increasing evidence being published.

Case Report Two cases of severe ventriculomegaly, neurological dysfunction, and seizures were found in neonates with prenatal exposure to COVID-19 infection during the first and third trimesters of pregnancy.

Conclusion Inflammation during the prenatal and neonatal periods may be associated with neurological disorders or injury. Despite the presumed lack of vertical transmission, post-COVID-19 syndrome and its associated inflammation may have an impact on the unborn fetus. Hyper-vigilance and dissemination of adverse findings are of significant importance as we navigate through this evolving pandemic and its effects.

Key Points
Sport Supplements and the Athlete’s Gut: A Review
Authors: Wilson Patrick
Published: November 2021

Vigorous or prolonged exercise poses a challenge to gastrointestinal system functioning and is associated with digestive symptoms. This narrative review addresses 1) the potential of dietary supplements to enhance gut function and reduce exercise-associated gastrointestinal symptoms and 2) strategies for reducing gastrointestinal-related side effects resulting from popular sports supplements. Several supplements, including probiotics, glutamine, and bovine colostrum, have been shown to reduce markers of gastrointestinal damage and permeability with exercise. Yet the clinical ramifications of these findings are uncertain, as improvements in symptoms have not been consistently observed. Among these supplements, probiotics modestly reduced exercise-associated gastrointestinal symptoms in a few studies, suggesting they are the most evidenced-based choice for athletes looking to manage such symptoms through supplementation. Carbohydrate, caffeine, and sodium bicarbonate are evidence-based supplements that can trigger gastrointestinal symptoms. Using glucose-fructose mixtures is beneficial when carbohydrate ingestion is high (>50 g/h) during exercise, and undertaking multiple gut training sessions prior to competition may also be helpful. Approaches for preventing caffeine-induced gastrointestinal disturbances include using low-to-moderate doses (<500 mg) and avoiding/minimizing exacerbating factors (stress, anxiety, other stimulants, fasting). Adverse gastrointestinal effects of sodium bicarbonate can be avoided by using enteric-coated formulations, low doses (0.2 g/kg), or multi-day loading protocols.
Understanding mechanisms of thermal expansion in complex oxide thin-films from first principles: Role of high-order phonon-strain anharmonicity
Authors: Ritz Ethan T. , Benedek Nicole A.
Published: November 2021

The thermal properties of materials are critically important to various technologies and are increasingly the target of materials design efforts. However, it is only relatively recent advances in first-principles computational techniques that have enabled researchers to explore the microscopic mechanisms of thermal properties, such as thermal expansion. We use the Grüneisen theory of thermal expansion in combination with density functional calculations and the quasiharmonic approximation to uncover mechanisms of thermal expansion in ferroelectric PbTiO3 thin-films. We show that although there are large changes in the elastic constants and Grüneisen parameters with both misfit strain and temperature, surprisingly the temperature evolution of the structural parameters can be modeled using a simple model of linear elasticity; the only inputs required are the misfit strain and bulk PbTiO3 elastic constants. We show that a near-cancellation between different types of anharmonicity gives rise to this behavior. Our results illustrate how different sources of anharmonicity can affect materials’ properties in different ways, even for the same material. The framework used in our study is general and illustrates how different types of anharmonicity can be systematically identified and explored.
Percolation theory based model of conduction mechanism and characteristic contradiction in ZnO RRAM
Authors: Qi Haiqing , Hu Cong , Wang Yanyong , Ali Salamat , Hu Junjie , Bai Na , Wang Qi , Qi Jing , He Deyan
Published: November 2021

Resistive random access memory (RRAM) has been intensively investigated for nearly two decades. However, RRAM has not been applied widely in the market because of the poor characteristics, such as reliability and uniformity, which could be improved by the accurate comprehension of the mechanism. In this paper, a model based on percolation theory is proposed to simulate the I-V characteristics of ZnO resistive switching memory. It demonstrates that three different conductions of space charge limited current, Poole–Frenkel effect, and thermionic emission are determined by the relationship between the oxygen vacancy concentration and the bias. Furthermore, this model well explains the effect of conductive filaments' diameter and compliance current on the I-V characteristics of ZnO resistive switching memory, which demonstrates the rationality of the percolation model.
Potential of the acoustic micromanipulation technologies for biomedical research
Authors: Akkoyun Fatih , Gucluer Sinan , Ozcelik Adem
Published: November 2021

Acoustic micromanipulation technologies are a set of versatile tools enabling unparalleled micromanipulation capabilities. Several characteristics put the acoustic micromanipulation technologies ahead of most of the other tweezing methods. For example, acoustic tweezers can be adapted as non-invasive platforms to handle single cells gently or as probes to stimulate or damage tissues. Besides, the nature of the interactions of acoustic waves with solids and liquids eliminates labeling requirements. Considering the importance of highly functional tools in biomedical research for empowering important discoveries, acoustic micromanipulation can be valuable for researchers in biology and medicine. Herein, we discuss the potential of acoustic micromanipulation technologies from technical and application points of view in biomedical research.
Magnon junction effect in Y3Fe5O12/CoO/Y3Fe5O12 insulating heterostructures
Authors: He Wenqing , Wu Hao , Guo Chenyang , Wan Caihua , Zhao Mingkun , Xing Yaowen , Tang Ping , Yan Zhengren , Xia Jihao , Yu Tian , Han Xiufeng
Published: November 2021

Magnonics as an emerging frontier of spintronics aims using magnons to deliver information free from electron scattering and as-induced Joule heating. In general, magnon currents can be excited both thermally and electrically in magnetic insulators by applying a current in an adjacent heavy-metal layer. Here, we report another kind of magnon junctions (MJs) composed of Y3Fe5O12/CoO/Y3Fe5O12 heterostructures, in which Y3Fe5O12 and CoO are, respectively, ferrimagnetic and antiferromagnetic insulators. A temperature gradient can drive a high (low) magnon current via the spin Seebeck effect when the Y3Fe5O12 layers in an MJ are configured at the parallel (antiparallel) state, showing a spin valve-like behavior. Electrically injected magnon current could also be controlled by the MJs, contributing to a magnon-mediate nonlocal spin Hall magnetoresistance (SMR). Furthermore, compared with its NiO counterpart, both the magnon junction and magnon-mediate SMR effects can be clearly observed at room temperature for the CoO-based magnon junctions, which can possibly be applied as a building block for room-temperature magnon-based memory or logic devices.
A potential model for assessing and adapting island biodiversity to the risks of climate change
Authors: Ball Derek , Gilbert-Ball Hannah
Published: November 2021

Context Island landscapes and component biodiversity provide invaluable services. However, these are threatened by climate change. There is currently no framework for assessing and mitigating such threats on islands. Aims Based on an existing adaptation standard, we aimed to propose a systematic approach for planning the adaptation of islands based on a risk management process. Methods For each risk, we investigated a range of adaptation approaches that can be considered and selected by conservation practitioners in designing conservation interventions. Key results For each risk identified, a range of adaptation measures can be selected: do nothing; maintain and enhance habitat, intensive species management, and preserve populations (including through ex situ conservation); or exploit the natural characteristics of islands to conserve biodiversity. Conclusions This approach provides a decision-making matrix of risks/drivers vs adaptation measures to assist in the design of conservation interventions, which can be applied to Australian islands on a priority basis. Implications There will inevitably remain gaps in knowledge and understanding that will hamper conservation efforts. There will also remain circumstances where adaptation is not possible and loss of services and biodiversity will follow as a result of climate change. However, the proposed model for assessing and adapting to climate change risks is a step forward from the current situation, where relatively little consideration is being given to climate change when developing island conservation interventions.
G protein signaling–biased mu opioid receptor agonists that produce sustained G protein activation are noncompetitive agonists
Authors: Stahl Edward L. , Schmid Cullen L. , Acevedo-Canabal Agnes , Read Cai , Grim Travis W. , Kennedy Nicole M. , Bannister Thomas D. , Bohn Laura M.
Published: November 2021

Significance

Analgesic tolerance can result upon chronic use of opioid drugs necessitating dose escalation to treat pain. The biased mu opioid receptor agonist SR-17018 maintains antinociceptive efficacy without evidence of tolerance when given chronically to mice. Here, we show that SR-17018 and related compounds are noncompetitive agonists that stabilize the receptor in an active state that can still be blocked by orthosteric antagonists. We propose that this mode of activation may contribute to the biased agonists’ apparent ability to preferentially induce G protein signaling in cellular assays and may underlie the enduring efficacy observed for SR-17018 in vivo.
Temporal order of signal propagation within and across intrinsic brain networks
Authors: Veit Mike J. , Kucyi Aaron , Hu Wenhan , Zhang Chao , Zhao Baotian , Guo Zhihao , Yang Bowen , Sava-Segal Clara , Perry Claire , Zhang Jianguo , Zhang Kai , Parvizi Josef
Published: November 2021

Significance

Direct electrical stimulation and intracranial recordings from the human brain during cognitive experiments revealed unique information about the temporal order of signal processing within and across intrinsic resting-state networks. Pairs of regions located within the same intrinsic networks communicate faster and coactivate closer in time than those located across different intrinsic networks.
Linguistic territoriality under stress
Authors: Burckhardt Till , Coakley John , Marácz László
Published: November 2021

This article revisits a well-known dichotomy (the ‘territorial’ and ‘personal’ principles) and develops a four-element classification of state approaches (from the most generous to the most menacing, from the perspective of speakers of minority languages). The article examines the implications for language policy of geographically dispersed or spatially concentrated patterns of distribution of speakers of particular languages. We begin by exploring the general literature on language policy, focusing in particular on the territorial and personal principles, the use of ‘threshold rules’ at municipal and other subnational levels, and the hybrid language regimes that are often a consequence of sociolinguistic complexity. We consider the extent to which responses to linguistic diversity across Europe may be understood by reference to these principles and categories. We explain why we have selected particular case studies (the Baltic republics, Transylvania, Switzerland, Belgium and Ireland) for further exploration. We conclude that, notwithstanding the value of the typologies we consider, real-life cases are almost invariably more complex, with states implementing policies that defy categorisation, that may change over time, and that may treat different language minorities by reference to different principles.
Personality and territoriality in theory and in Belgium
Authors: Schutter Helder De
Published: November 2021

Language policy debates regularly refer to the principles of personality and territoriality. Yet the precise meaning of these principles remains unclear. In this contribution, I conceptualize these principles as poles of a continuum between official bilingualism (instantiating the personality principle) and official unilingualism (exemplifying the territoriality principle), with a mixed regime in between (which grants a certain territorial primacy to a language, but allows exceptions based on linguistic affiliation). The question of the determination of particular points on the continuum cannot be separated from the metaterritorial question of the boundaries of the units within which those principles apply. Application of this ‘continuum model’ to Belgium draws attention to three language-political regimes. The first invokes a strict personality principle (Brussels). The second follows the strict territoriality principle (almost all municipalities in Flanders and Wallonia). The third is a mixed regime (a total of 27 ‘municipalities with facilities’ where one language enjoys primacy but speakers of another language enjoy certain linguistic ‘facilities’). The article also analyses the manner in which these regimes were historically established in Belgium in combination with a delineation of the language border and the division of the country into four language areas.
Geographical retreat and symbolic advance?
Authors: Coakley John
Published: November 2021

Language policy in the Republic of Ireland has an unusual starting point: the geographical base of the Irish language is very weak and territorially dispersed, yet the constitutional status of the language is extremely strong. The article explores this paradox. It sets Irish language policy in two contexts: that of successful nationalist movements mainly in Central and Eastern Europe in the early twentieth century, and that of the struggling Celtic languages of Western Europe. It explores the evolution of the language and its weakening demographic status since the nineteenth century, noting that while its demographic weakness mirrors that of the other Celtic languages, its constitutional entrenchment resembles that of the national languages of Central and East European states. It attempts to explain this by suggesting that the language has played a marginal role in nationalist mobilisation; the language served as a symbol of a specific cultural heritage rather than as the vital lingua franca of the community. The central role of the language in nationalist ideology, however, failed to address the reality of continuing decline in the Irish-speaking districts, notwithstanding the emergence of a sizeable population of ‘new speakers’ of the language outside these districts.
Quantitative correlative microscopy reveals the ultrastructural distribution of endogenous endosomal proteins
Authors: van der Beek Jan , de Heus Cecilia , Liv Nalan , Klumperman Judith
Published: November 2021

The key endosomal regulators Rab5, EEA1, and APPL1 are frequently applied in fluorescence microscopy to mark early endosomes, whereas Rab7 is used as a marker for late endosomes and lysosomes. However, endogenous levels of these proteins localize poorly in immuno-EM, and systematic studies on their native ultrastructural distributions are lacking. To address this gap, we here present a quantitative, on-section correlative light and electron microscopy (CLEM) approach. Using the sensitivity of fluorescence microscopy, we label hundreds of organelles that are subsequently visualized by EM and classified by ultrastructure. We show that Rab5 predominantly marks small, endocytic vesicles and early endosomes. EEA1 colocalizes with Rab5 on early endosomes, but unexpectedly also labels Rab5-negative late endosomes, which are positive for PI(3)P but lack Rab7. APPL1 is restricted to small Rab5-positive, tubulo-vesicular profiles. Rab7 primarily labels late endosomes and lysosomes. These data increase our understanding of the structural–functional organization of the endosomal system and introduce quantitative CLEM as a sensitive alternative for immuno-EM.
Blood stem cell PU.1 upregulation is a consequence of differentiation without fast autoregulation
Authors: Ahmed Nouraiz , Etzrodt Martin , Dettinger Philip , Kull Tobias , Loeffler Dirk , Hoppe Philipp S. , Chavez James S. , Zhang Yang , Camargo Ortega Germán , Hilsenbeck Oliver , Nakajima Hideaki , Pietras Eric M. , Schroeder Timm
Published: November 2021

Transcription factors (TFs) regulate cell fates, and their expression must be tightly regulated. Autoregulation is assumed to regulate many TFs’ own expression to control cell fates. Here, we manipulate and quantify the (auto)regulation of PU.1, a TF controlling hematopoietic stem and progenitor cells (HSPCs), and correlate it to their future fates. We generate transgenic mice allowing both inducible activation of PU.1 and noninvasive quantification of endogenous PU.1 protein expression. The quantified HSPC PU.1 dynamics show that PU.1 up-regulation occurs as a consequence of hematopoietic differentiation independently of direct fast autoregulation. In contrast, inflammatory signaling induces fast PU.1 up-regulation, which does not require PU.1 expression or its binding to its own autoregulatory enhancer. However, the increased PU.1 levels induced by inflammatory signaling cannot be sustained via autoregulation after removal of the signaling stimulus. We conclude that PU.1 overexpression induces HSC differentiation before PU.1 up-regulation, only later generating cell types with intrinsically higher PU.1.
High-sensitivity electrical properties measurement of graphene-based composites using interferometric near-field microwave technique
Authors: Bakli Hind , Moualhi Mohamed , Makhlouf Mourad
Published: November 2021

High-sensitivity electrical properties measurement of composite materials using an interferometric near-field microwave technique is proposed in this paper. A one-port calibration model is developed to relate the measured transmission coefficient to the local properties of the material. To represent the probe–composite sample interaction, an electrical model based on lumped elements is developed. As a demonstration, the complex permittivity and conductivity of composite materials prepared with polyvinyl chloride and different concentrations of graphene are experimentally determined at 2.45 GHz. The obtained results show that the proposed technique is sensitive for the detection of small contrasts of permittivity and conductivity in the composite material. When the graphene concentration increases from 1% to 30%, the conductivity increases from 0.0061 s m−1 to 0.056 s m−1.
Photonic implementation of spike timing dependent plasticity with weight-dependent learning window based on VCSOA
Authors: Tian Tao , Wu Zhengmao , Lin Xiaodong , Tang Xi , Gao Ziye , Ni Min , Xia Guangqiong , Chen Haitao , Deng Tao
Published: November 2021

Based on the well-known Fabry–Pérot approach, after taking into account the variation of bias current of the vertical-cavity semiconductor optical amplifier (VCSOA) according to the present synapse weight, we implement the optical spike timing dependent plasticity (STDP) with weight-dependent learning window in a VCSOA with double optical spike injections, and numerically investigate the corresponding weight-dependent STDP characteristics. The simulation results show that, the bias current of VCSOA has significant effect on the optical STDP curve. After introducing an adaptive variation of the bias current according to the present synapse weight, the optical weight-dependent STDP based on VCSOA can be realized. Moreover, the weight training based on the optical weight-dependent STDP can be effectively controlled by adjusting some typical external or intrinsic parameters and the excessive adjusting of synaptic weight is avoided, which can be used to balance the stability and competition among synapses and pave a way for the future large-scale energy efficient optical spiking neural networks based on the weight-dependent STDP learning mechanism.
Palladium nanoparticles/wool keratin-assisted carbon composite-modified flexible and disposable electrochemical solid-state pH sensor
Authors: Zhang Wenli , Liu Xiaotian , Lin Youhui , Ma Liyun , Kong Linqing , Min Guangzong , Wu Ronghui , Mengane Sharwari K. , Yang Likun , Patil Aniruddha B. , Liu Xiang Yang
Published: November 2021

Several pH-dependent processes and reactions take place in the human body; hence, the pH of body fluids is the best indicator of disturbed health conditions. However, accurate and real-time diagnosis of the pH of body fluids is complicated because of limited commercially available pH sensors. Hence, we aimed to prepare a flexible, transparent, disposable, user-friendly, and economic strip-based solid-state pH sensor using palladium nanoparticles (PdNPs)/N-doped carbon (NC) composite material. The PdNPs/NC composite material was synthesized using wool keratin (WK) as a precursor. The in-situ prepared PdNPs played a key role in the controlled switching of protein structure to the N-doped carbon skeleton with π–π arrangement at the mesoscale level, which mimics the A–B type polymeric structure, and hence, is highly susceptible to H+ ions. The optimized carbonization condition in the presence of PdNPs showed that the material obtained using a modified Ag/AgCl reference electrode had the highest pH sensitivity with excellent stability and durability. The optimized pH sensor showed high specificity and selectivity with a sensitivity of 55 mV/pH unit and a relative standard deviation of 0.79%. This study is the first to synthesize PdNPs using WK as a stabilizing and reducing agent. The applicability of the sensor was investigated for biological samples, namely, saliva and gastric juices. The proposed protocol and material have implications in solid-state chemistry, where biological material will be the best choice for the synthesis of materials with anticipated performance.
Molecular dynamics simulations of A-DNA in bivalent metal ions salt solution
Authors: Xue Jingjing , Li Xinpeng , Tan Rongri , Zong Wenjun
Published: November 2021

A-form DNA is one of the biologically active double helical structure. The study of A-DNA structure has an extensive application for developing the field of DNA packaging in biotechnology. In aqueous solution, the A-DNA structure will have a free transformation, the A-DNA structure will be translated into B-form structure with the evolution of time, and eventually stabilized in the B-DNA structure. To explore the stability function of the bivalent metal ions on the A-DNA structure, a series of molecular dynamics simulations have been performed on the A-DNA of sequence (CCCGGCCGGG). The results show that bivalent metal ions (Mg2+, Zn2+, Ca2+) generate a great effect on the structural stability of A-DNA in the environment of high concentration. As the interaction between metal ions and electronegative DNA chains, the stability of A-DNA in solution is gradually improved with the increasing solution concentration of ions. In metal salt solution with high concentration, metal ions can be easily distributed in the solvation shells around the phosphate groups and further lead to the formation of shorter and more compact DNA structure. Also, under the condition of the same concentration and valency of the metal ions, the stability of A-DNA structure is different. The calculations indicate that the structure of A-DNA in CaCl2 solution is less stable than in MgCl2 and ZnCl2 solution.
Molecular dynamics simulations of mechanical properties of epoxy-amine: Cross-linker type and degree of conversion effects
Authors: Zhang Yongqin , Yang Hua , Sun Yaguang , Zheng Xiangrui , Guo Yafang
Published: November 2021

Molecular dynamics (MD) simulations are conducted to study the thermo-mechanical properties of a family of thermosetting epoxy-amines. The crosslinked epoxy resin EPON862 with a series of cross-linkers is built and simulated under the polymer consistent force field (PCFF). Three types of curing agents (rigidity1,3-phenylenediamine (1,3-P), 4,4-diaminodiphenylmethane (DDM), and phenol-formaldehyde-ethylenediamine (PFE)) with different numbers of active sites are selected in the simulations. We focus on the effects of the cross-linkers on thermo-mechanical properties such as density, glass transition temperature (T
g), elastic constants, and strength. Our simulations show a significant increase in the T
g, Young’s modulus and yield stress with the increase in the degree of conversion. The simulation results reveal that the mechanical properties of thermosetting polymers are strongly dependent on the molecular structures of the cross-linker and network topological properties, such as end-to-end distance, crosslinking density and degree of conversion.
Simulation of the physical process of neural electromagnetic signal generation based on a simple but functional bionic Na+ channel
Authors: Wang Fan , Xu Jingjing , Ge Yanbin , Xu Shengyong , Fu Yanjun , Shi Caiyu , Xue Jianming
Published: November 2021

The physical processes occurring at open Na+ channels in neural fibers are essential for the understanding of the nature of neural signals and the mechanism by which the signals are generated and transmitted along nerves. However, there is a less generally accepted description of these physical processes. We studied changes in the transmembrane ionic flux and the resulting two types of electromagnetic signals by simulating the Na+ transport across a bionic nanochannel model simplified from voltage-gated Na+ channels. The results show that the Na+ flux can reach a steady state in approximately 10 ns due to the dynamic equilibrium of the Na+ ion concentration difference between both sides of the membrane. After characterizing the spectrum and transmission of these two electromagnetic signals, the low-frequency transmembrane electric field is regarded as the physical quantity transmitting in the waveguide-like lipid dielectric layer and triggering the neighboring voltage-gated channels. Factors influencing the Na+ flux transport are also studied. The impact of the Na+ concentration gradient is found to be higher than that of the initial transmembrane potential on the Na+ transport rate, and introducing the surface-negative charge in the upper third channel could increase the transmembrane Na+ current. This work can be further studied by improving the simulation model; however, the current work helps to better understand the electrical functions of voltage-gated ion channels in neural systems.
Temperature-responded tunable metalenses based on phase transition materials
Authors: Wu Jing-Jun , Tang Feng , Ma Jun , Han Bing , Wei Cong , Li Qing-Zhi , Chen Jun , Zhang Ning , Ye Xin , Zheng Wan-Guo , Zhu Ri-Hong
Published: November 2021

Once the metalenses are fabricated, the functions of most metalenses are invariable. The tunability and reconfigurability are useful and cost-saving for metalenses in realistic applications. We demonstrate this tunability here via a novel hybrid metalens with the strategic placement of an ultra-thin VO2 layer. The hybrid metalens is capable of dynamically modulating the focusing intensity of transmitted light at a wavelength of 1550 nm, and demonstrate a 42.28% focusing efficiency of the incident light and 70.01% modulation efficiency. The hybrid metalens’ optothermal simulations show an optothermal conversion process of dynamic focusing, and a maximum laser density of 1.76×103 W/cm2 can be handled at an ambient temperature lower than 330 K. The hybrid metalens proposed in this work, a light-dose sensitive tunable smart metalens that can protect other instruments/systems or materials from being damaged, has its specific applications such as in anti-satellite blinding, bio-imaging, etc.
Bias-induced reconstruction of hybrid interface states in magnetic molecular junctions
Authors: Zhang Ling-Mei , Miao Yuan-Yuan , Cao Zhi-Peng , Qiu Shuai , Zhang Guang-Ping , Ren Jun-Feng , Wang Chuan-Kui , Hu Gui-Chao
Published: November 2021

Based on first-principles calculations, the bias-induced evolutions of hybrid interface states in π-conjugated tricene and in insulating octane magnetic molecular junctions are investigated. Obvious bias-induced splitting and energy shift of the spin-resolved hybrid interface states are observed in the two junctions. The recombination of the shifted hybrid interface states from different interfaces makes the spin polarization around the Fermi energy strongly bias-dependent. The transport calculations demonstrate that in the π-conjugated tricene junction, the bias-dependent hybrid interface states work efficiently for large current, current spin polarization, and distinct tunneling magnetoresistance. But in the insulating octane junction, the spin-dependent transport via the hybrid interface states is inhibited, which is only slightly disturbed by the bias. This work reveals the phenomenon of bias-induced reconstruction of hybrid interface states in molecular spinterface devices, and the underlying role of conjugated molecular orbitals in the transport ability of hybrid interface states.
Dynamic vortex Mott transition in triangular superconducting arrays
Authors: Pei Zi-Xi , Guo Wei-Gui , Qiu Xiang-Gang
Published: November 2021

The proximity-coupled superconducting island arrays on a metallic film provide an ideal platform to study the phase transition of vortex states under mutual interactions between the vortex and potential landscape. We have developed a top-down microfabrication process for Nb island arrays on Au film by employing an Al hard mask. A current-induced dynamic vortex Mott transition has been observed under the perpendicular magnetic fields of f magnetic flux quantum per unit cell, which is characterized by a dip-to-peak reversal in differential resistance d V/d I vs. f curve with the increasing current. The d V/d I vs. I characteristics show a scaling behavior near the magnetic fields of f = 1/2 and f = 1, with the critical exponents ε of 0.45 and 0.3, respectively, suggesting different universality classes at these two fields.
Higher-order tensor decomposition based scalp-to-intracranial EEG projection for detection of interictal epileptiform discharges
Authors: Abdi-Sargezeh Bahman , Valentin Antonio , Alarcon Gonzalo , Martin-Lopez David , Sanei Saeid
Published: November 2021

Objective. Interictal epileptiform discharges (IEDs) occur between two seizures onsets. IEDs are mainly captured by intracranial recordings and are often invisible over the scalp. This study proposes a model based on tensor factorization to map the time-frequency (TF) features of scalp EEG (sEEG) to the TF features of intracranial EEG (iEEG) in order to detect IEDs from over the scalp with high sensitivity. Approach. Continuous wavelet transform is employed to extract the TF features. Time, frequency, and channel modes of IED segments from iEEG recordings are concatenated into a four-way tensor. Tucker and CANDECOMP/PARAFAC decomposition techniques are employed to decompose the tensor into temporal, spectral, spatial, and segmental factors. Finally, TF features of both IED and non-IED segments from scalp recordings are projected onto the temporal components for classification. Main results. The model performance is obtained in two different approaches: within- and between-subject classification approaches. Our proposed method is compared with four other methods, namely a tensor-based spatial component analysis method, TF-based method, linear regression mapping model, and asymmetric–symmetric autoencoder mapping model followed by convolutional neural networks. Our proposed method outperforms all these methods in both within- and between-subject classification approaches by respectively achieving 84.2% and 72.6% accuracy values. Significance. The findings show that mapping sEEG to iEEG improves the performance of the scalp-based IED detection model. Furthermore, the tensor-based mapping model outperforms the autoencoder- and regression-based mapping models.
Swirling to improve heat transfer in the MHD flow of liquid metal in a duct
Authors: Yu Chernysh D , Krasnov D , Kolesnikov Yu B , Belyaev I A
Published: November 2021

The subject of this study is the effect of the initial “swirling” of the flow by installing cylindrical elements in the initial flow region affected by strong magnetic field. In particular, various designs (longitudinal, transverse, and inclined arrangement with respect to the magnetic field) and the dimensions of the cylinders are considered. To create liquid metal systems that are more predictable and possibly more efficient from the point of view of thermal hydraulics, we experimentally studied the flow in a rectangular channel with dimensions of 56×16 mm. For the first time, it was found that the presence of an initial flow disturbance leads to significant changes in the flow at a significant length (700 mm).
Numerical analysis of heat transfer and fluid flow around circular and non-circular tubes
Authors: Deeb R , Sidenkov D V
Published: November 2021

A two-dimensional study of turbulent flow and heat transfer in a channel with circular and non-circular tubes has been carried out using the CFD Fluent software package. Four non-circular tubes were investigated: flat, ellipse, cam, and drop-shaped. Reynolds number varied in the range of 7300 ≤ Re ≤ 14600. All tubes were investigated under similar operating conditions. Local heat transfer, pressure, and friction coefficients over a surface of the tubes were presented. The thermal-hydraulic performance was used to estimate the efficiency of the non-circular tubes. The results indicated that the drop-shaped tube has the best thermal-hydraulic performance, which was about 5.6, 2.6, 1.7, 1.3 times higher than that of the circular, flat, ellipse, cam tube, respectively.
Numerical study on heat transfer characteristics of swirling flow on dimpled surfaces with effusion holes at turbine blade leading edge
Authors: Kong Dehai , Liu Cunliang , Isaev S A
Published: November 2021

In this paper, we conducted a numerical study to investigate the effect of the offset of the jet holes on heat transfer of swirling flow in a concave target chamber with various dimple structures and effusion holes at the turbine blade leading edge. The distance of the jet holes off the centerline e/d varies from 0 to 2.0. Four types of dimple structure, including spherical dimples (SDs) and oval-trench dimples (OTDs) in the inline and staggered arrangement, are considered. The heat transfer performance of the different leading-edge, impingement-effusion cooling structures is evaluated and compared at a Reynolds number of 30,000 based on the jet hole diameter. Results show that the offset of the jet holes provides 15% higher overall heat transfer performance and more uniform heat transfer of the target surface within the e/d range of 0-2.0. The introduction of the dimple structures on the target surface slightly decreases the overall averaged Nusselt number but enhance the heat transfer quantity due to the clear increase of heat transfer areas. Under the same e/d, the OTD structure, especially with the staggered arrangement, is superior to SD structure.
Flow analysis in seamless hot-extruded pipes with helical inner ribbing surface
Authors: Kosmatskiy Ya Ig , Yu Egorov M , Lychakov V D
Published: November 2021

The article is devoted to numerical simulation of heat transfer processes occurring during the flow of a coolant in seamless hot-extrusion pipes with a spiral inner fin surface (TMK-IRS). A description of the numerical modeling technique is given along with the interface of the program used to create different types of internal fins. Thermohydraulic analysis of finned pipes for transient, turbulent and laminar flow regimes has been carried out. An estimate of the critical Reynolds number characterizing the transition to a turbulent regime, the nature of the transient flow regime in comparison with other classical cases is given.
Analysis of vortex structures formed in the winter in the atmosphere of Krasnoyarsk city
Authors: Filimonov S A , Meshkova V D , Dekterev A A , Gavrilov A A , Yu Litvintsev K , Shebelev A V
Published: November 2021

The article considers the influence of the relief, river, and urban development on the formation of vortex structures in the atmosphere and the spread of pollutants in the city of Krasnoyarsk in winter. The weak influence of urban development on the appearance of large vortex structures over the river is shown. However, in the ground layer, it significantly changes the flow pattern and determines the character of the distribution of pollutants.
Development of a simplified methodology for furnace aerodynamics with vortex combustion of organic fuel modeling
Authors: Prokhorov V B , Fomenko N E , Fomenko M V
Published: November 2021

This paper describes the process of developing a simplified methodology for furnace aerodynamics during the development or modernization of combustion schemes with direct-flow burners. This technique is based on the use of numerical modeling of air movement and turbulence phenomena in the furnace volume and allows for a relatively short period of time to analyze a large number of options for the burners and nozzles location. This is its advantage in comparison with the use of experimental modeling or numerical simulation with combustion when analyzing a variety of schemes. The model was developed on the basis of validated results of combustion processes numerical simulation in the K-50 boiler furnace. The paper presents the results of calculations performed for several variants of the simplified methodology. For further use, the option that best corresponds to full-scale studies taking into account the fuel combustion process has been selected. The main states of the methodology are formulated.
Experimental and computational study of a low-pressure natural circulation loop
Authors: Kabankov O N , Yagov V V , Zubov N O
Published: November 2021

The experimental and analytical study of single-phase flow and heat transfer in natural circulation loop has been carried out. Experiments were performed on water and ethanol that are the liquids with significantly different thermophysical properties. Experimental apparatus was a rectangular shaped loop with vertical flow up leg. The flow up and flow down legs of the loop are joined to the separator-condenser at the top of the loop. The upper limit of heat flux densities in the experiments was set with the consideration for flow regime to remain in single phase state along the whole heated length. Wall temperature time records being registered at different distances from the inlet to the heated zone indicate the occurrence of temperature fluctuations near the exit from heated zone even at relatively low heat flux densities. This fact displaces a complex changing of velocity profiles along the tube with vortex formation and occurrence of flow instability. Experimental data on longitudinal wall temperature distributions of heated section have been used to test a modified method of hydraulic calculation of the loop. It was pointed out that in spite of long year (since early 1950s) experimental, analytical and numerical investigations of natural circulation loops no suitable predicting recommendations for heat transfer and friction have been proposed till today for engineering hydraulic calculations of single-phase natural circulation loops.
Thermal detonation wave in liquid lead – water mixture
Authors: Kapustin A V , Melikhov V I , Melikhov O I , Saleh B , Finoshkina D V
Published: November 2021

It was developed the model of thermal detonation in a mixture of continuous liquid lead and dispersed steam/water particles. Stationary equations of mass, impulse and energy conservations laws for multiphase continuum are applied to describe internal structure of thermal detonation wave. They are supplemented by closing relations describing interfacial friction, heat transfer, and fragmentation. Conditions at leading shock wave and at Chapman-Jouguet plane are used as boundary conditions.
Influence of a non-condensable gas on mixing of a melt with water in a stratified configuration
Authors: Melikhov V I , Melikhov O I , Yakush S E , Saleh B , Borzdyi N A
Published: November 2021

The influence of bubbles of hot non-condensable gas formed at the interface between the melt and water on the formation of a mixture of melt with water capable of producing steam explosions is considered. The dynamics of such a bubble in subcooled water is analyzed numerically in a one-dimensional spherically symmetric approximation. It is shown that with significant initial superheat of the bubble relative to the water, a rapid drop in pressure in the bubble occurs due to strong heat removal into the water. This leads to the collapse of the bubble and the appearance of an accompanying flow of water. The results obtained made it possible to approximately describe the stage of collapse of the bubble as the polytropic process and to determine its index. The axisymmetric problem of the impact of the water jet on the surface of a melt during collapse of a gas bubble near the interface between the melt and water is numerically investigated. In this case, the obtained polytropic process equation is used to determine the pressure in the bubble. It is found that the resulting impact on the melt is capable of knocking out melt droplets into the water to a height of several centimeters, which leads to the formation of a layer of water mixed with the melt droplets, which is capable of producing strong steam explosions.
Heat flux during boiling of superfluid helium inside a porous body based on a two-fluid model
Authors: Puzina Yu Yu , Kryukov A P
Published: November 2021

The calculation of the recovery heat flux density is considered for superfluid helium boiling on the cylindrical heater inside porous structure. System of equations is based on the methods of continuum mechanics and molecular kinetic theory. The new type of boundary condition on the vapor-liquid interface based on the two-fluid model is formulated. Heat transfer in a free liquid is described by the Gorter-Mellink semi-empirical theory. Inside the porous structure the processes is discussed by the two-fluid model and filtration equation. Experimental data on the boiling of superfluid helium inside the porous structure are interpreted based on the formulated mathematical model. The qualitative and in some cases quantitative agreement between the calculated and experimental values of the recovery heat flux were obtained in the considered range of parameters
Numerical study of the vortex breakdown and vortex reconnection in the flow path of high-pressure water turbine
Authors: Sentyabov A V , Platonov D V , Minakov A V , Lobasov A S
Published: November 2021

The paper presents a study of the instability of the precessing vortex core in the model of the draft tube of a hydraulic turbine. The study was carried out using numerical modeling using various approaches: URANS, RSM, LES. The best agreement with the experimental data was shown by the RSM and LES methods with the modelling of the runner rotation by the sliding mesh method. In the regime under consideration, the precessing vortex rope is subject to instability, which leads to reconnection of its turns and the formation of an isolated vortex ring. Reconnection of the vortex core leads to aperiodic and intense pressure fluctuations recorded on the diffuser wall.
Heat transfer in laser passive and deformable mirrors
Authors: Leonov E , Chernykh A , Shanin Yu
Published: November 2021

In work, the possibilities of using uncooled and cooled optical elements (including laser passive and deformable mirrors) with an increase in the power of laser facilities are analyzed. To increase the permissible light loads acting on the optical elements, the use of highly efficient cooling systems with minichannels (coplanar and multi-tiered), providing a high compactness of the heat exchange surface and the intensification of heat transfer, is considered. The advantages and efficiency of the proposed cooling systems for reducing the displacement of the optical surface of the mirror due to bending are estimated.
The role of boundary conditions on the free surface of a liquid metal in an electrovortex flow
Authors: Teplyakov I O , Kiselyova S V , Malyshev K Yu , Mikhaylov E A
Published: November 2021

An electro-vortex flow between two hemispherical electrodes is considered. The influence of the type of boundary condition on the surface of a conducting liquid medium on the velocity field in the volume is studied numerically. The dependences of the velocity on the axis of the vessel on the radius of the small electrode and the parameter of the electric vortex flow are obtained for various types of boundary conditions on the surface.
The Phenomenon of Hysteresis in a Swirling Stream
Authors: Sergeev M N , Veretennikov S V , Pudeev A I
Published: November 2021

The article considers a swirling current with a sudden expansion. As a result of an experimental study, it was found that two flow modes can exist under these conditions. In the first case, there is an intense twist at the outlet of the vortex device, a zone of return currents and precessional oscillations. In the second case, there is no zone of return currents and precession. At the same time, the gas flow through the device increases abruptly
Influence of pulsed modes of a magnetic field on an electric vortex flow
Authors: Vinogradov D A , Teplyakov I O , Ivochkin Yu P , Shihov K A , Zhidkov A V
Published: November 2021

Using a fiber-optic velocity transducer, the effect of external pulsed magnetic fields on the structure of electrovortex flows is experimentally investigated. It is shown that an external pulsed magnetic field can lead to the appearance of oscillations of significant amplitude in a liquid metal.