bluuebunny/crossref_metadata_2025 huggingface dataset:
High power continuous wave laser heating of graphite in a high temperature range up to 3800 K
Authors: Gallais L. , Vidal T. , Lescoute E. , Pontillon Y. , Rullier J. L.
Published: January 2021

As graphite is an important material for several applications, the evaluation of its properties at very high temperatures is of major importance. Conducting studies at temperatures >2800 K is, however, very challenging, and the amount of available data in the literature is, therefore, very limited. This paper presents a methodology that compares experimental data with simulation results following a progressive increase of the temperature range investigated. The study was conducted on a commercial polycrystalline graphite produced by sintering (EDM-3 from POCO) under high power continuous laser heating (kW ytterbium at a wavelength of 1080 nm). Experiments were done inside a vacuum chamber equipped with pyrometers and cameras allowing fine monitoring of the temperature of the samples. A 3D numerical model has been developed based on the finite element method to analyze the experimental results. The evolution of the thermal and optical properties of EDM-3 with temperature is required for correctly modeling laser/material interactions. By running a sequential comparison of calculation with a dedicated experiment, we achieve better knowledge of such properties. From this study, we obtain estimations of the evolution of thermal conductivity, emissivity, and evaporation rate up to 3800 K of amorphous graphite.
Photon-assisted Landau–Zener transitions in a periodically driven Rabi dimer coupled to a dissipative mode
Authors: Zheng Fulu , Shen Yuejun , Sun Kewei , Zhao Yang
Published: January 2021

We investigate multiple photon-assisted Landau–Zener (LZ) transitions in a hybrid circuit quantum electrodynamics device in which each of two interacting transmission-line resonators is coupled to a qubit, and the qubits are driven by periodic driving fields and also coupled to a common phonon mode. The quantum state of the entire composite system is modeled using the multi-D2 Ansatz in combination with the time-dependent Dirac–Frenkel variational principle. Applying a sinusoidal driving field to one of the qubits, this device is an ideal platform to study the photon-assisted LZ transitions by comparing the dynamics of the two qubits. A series of interfering photon-assisted LZ transitions takes place if the photon frequency is much smaller than the driving amplitude. Once the two energy scales are comparable, independent LZ transitions arise and a transition pathway is revealed using an energy diagram. It is found that both adiabatic and nonadiabatic transitions are involved in the dynamics. Used to model environmental effects on the LZ transitions, the common phonon mode coupled to the qubits allows for more available states to facilitate the LZ transitions. An analytical formula is obtained to estimate the short time phonon population and produces results in reasonable agreement with numerical calculations. Equipped with the knowledge of the photon-assisted LZ transitions in the system, we can precisely manipulate the qubit state and successfully generate the qubit dynamics with a square-wave pattern by applying driving fields to both qubits, opening up new venues to manipulate the states of qubits and photons in quantum information devices and quantum computers.
The role of a dielectric barrier in single-filament discharge over a water surface
Authors: Höft H. , Kettlitz M. , Brandenburg R.
Published: January 2021

A dielectric barrier discharge over distilled water was investigated by means of synchronized, fast electrical and optical diagnostics. For this purpose, a single, alumina-covered electrode was placed above a water surface and a grounded tungsten electrode underwater, while the gas gap was constantly flushed with synthetic air at atmospheric pressure. Discharge events occur at rising and falling slopes or at the plateaus of the applied high-voltage pulse. Due to the synchronized diagnostics, a direct comparison of electrical characteristics and optical features of individual discharge events was performed. In most cases, a single discharge channel develops between the tips of the dielectric and the Taylor cone. Surface discharge channels can also occur in the upper part of the electrodes, which can be explained by a water layer being formed on the dielectric and acting as a virtual electrode. The discharge morphology and dynamics were found to be independent of the voltage polarity, which contradicts to known experiments with bare metal pin electrodes instead of dielectric-covered ones.
Gradual magnetization switching via domain nucleation driven by spin–orbit torque
Authors: Wan C. H. , Stebliy M. E. , Wang X. , Yu G. Q. , Han X. F. , Kolesnikov A. G. , Bazrov M. A. , Letushev M. E. , Ognev A. V. , Samardak A. S.
Published: January 2021

Gradual magnetization switching driven by spin–orbit torque (SOT) is preferred for neuromorphic computing in a spintronic manner. Here we have applied focused ion beam to selectively illuminate patterned regions in a Pt/Co/MgO strip with perpendicular magnetic anisotropy, soften the illuminated areas, and realize the gradual switching by a SOT-driven nucleation process. It is found that a large in-plane field is helpful to reduce the nucleation barrier, increase the number of nucleated domains and intermediate states during the switching progress, and finally flatten the switching curve. We proposed a phenomenological model for descripting the current dependence of magnetization and the dependence of the number of nucleation domains on the applied current and magnetic field. This study may promote the birth of SOT devices applicable in neuromorphic computing applications.
Tunable spin-valley polarized transport channel in silicene-based superconducting hybrid structures
Authors: Wei Ya-Jun , Tao Y. C.
Published: January 2021

We investigate the influence of spin-valley polarized transport channel (SVPTC) mismatch modulated by the perpendicular electric field and the exchange field in a silicene-based ferromagnet/ferromagnet/superconductor junction and the barrier strength in a ferromagnet/insulator/ferromagnet/superconductor junction. In the former junction, due to the mismatch of SVPTC caused by the different electric fields applied in the two ferromagnet (F) layers, the zero-bias Andreev reflection and zero-bias conductance peak (ZBCP) are suppressed. Moreover, by shifting the band, the exchange field can lead to the different mismatch of SVPTC between the two F layers with opposite magnetization orientations, and thus, the conversion from ZBCP to a zero-bias conductance valley can be observed. For the latter junction, due to the electrically tunable SVPTC, the phase shift of conductance oscillation with barrier strength is created by changing the electric field but not by altering the exchange field. Particularly, for the variation from the parallel to the antiparallel magnetic configuration, there is a phase shift π/2 of conductance vs the barrier strength.
Multiplicity of solution for natural convective heat transfer and entropy generation in a semi-elliptical enclosure
Authors: Sarkar U. K. , Biswas Nirmalendu , Öztop Hakan F.
Published: January 2021

The problem of steady natural convection in a bottom-heated semi-elliptical enclosure has been investigated numerically for a wide range of geometric and flow configurations using the finite volume method. The results are presented for varying Rayleigh numbers, Ra, in the range 1 × 102 ≤ Ra ≤ 5 × 104 and different values of aspect ratio, A = 1, 0.75, 0.5, and 0.25, where the aspect ratio, A, is defined as the ratio of lengths of the semi-minor axis to the semi-major axis of the semi-elliptical enclosure. It has been found that the steady-state solution appears in the form of single or multiple pairs of counter-rotating convection cells depending on the values of physical parameters. For A = 1, 0.75, and 0.5, as the value of Rayleigh number exceeds a critical value, natural convective flow inside the semi-elliptical enclosure exhibits multiple steady solutions with varying pairs of counter-rotating convection cells; however, such multiplicity of steady solutions could not be found for the cases of A = 0.25. The parametric variations of heat transfer and entropy generation rates are studied in detail. It is observed that the average Nusselt number associated with the natural convection in the semi-elliptical cavity is governed by several parameters: aspect ratio, Rayleigh number, number of convection cells, and intensity of convective motion inside the convection cells. The entropy generation due to viscous dissipation is found to be negligible as compared to the entropy generation due to conduction.
Semi-analytical analysis of high-brightness microbunched beam dynamics with collective and intrabeam scattering effects
Authors: Tsai Cheng-Ying , Qin Weilun
Published: January 2021

The studies of incoherent single-particle and collective multi-particle effects are, in general, separated in accelerator beam dynamics in that the two dynamical phenomena involve quite different time scales. Recent experimental measurements indicate that in some parameter regime, the small-angle, multiple scattering effects within a high-brightness electron beam can have a strong influence on microbunched beam dynamics. In this paper, we apply our recently developed semi-analytical kinetic analysis to investigate the collective phase space microbunched dynamics in the presence of incoherent single-particle effects. Particular emphasis will be placed on evaluation of the intrinsic or slice energy spread. An example of two linear beam transport lines, followed by two identical, interleaving bunch compressor chicanes, is then presented. The semi-analytical calculations are consistent with particle tracking simulations. Moreover, the threshold condition is derived, indicating the relation among relevant physical quantities. At threshold, the incoherent effect can be beneficial for effective suppression of the collective microbunching instability. We expect that this work could shed light on high-brightness electron transport beamline design to improve short-wavelength free-electron laser performance.
The golden age of social science
Authors: Buyalskaya Anastasia , Gallo Marcos , Camerer Colin F.
Published: January 2021

Social science is entering a golden age, marked by the confluence of explosive growth in new data and analytic methods, interdisciplinary approaches, and a recognition that these ingredients are necessary to solve the more challenging problems facing our world. We discuss how developing a “lingua franca” can encourage more interdisciplinary research, providing two case studies (social networks and behavioral economics) to illustrate this theme. Several exemplar studies from the past 12 y are also provided. We conclude by addressing the challenges that accompany these positive trends, such as career incentives and the search for unifying frameworks, and associated best practices that can be employed in response.
Large remodeling of the Myc-induced cell surface proteome in B cells and prostate cells creates new opportunities for immunotherapy
Authors: Chen Wentao , Mou Kurt Yun , Solomon Paige , Aggarwal Rahul , Leung Kevin K. , Wells James A.
Published: January 2021

Significance

MYC is a powerful transcription factor and when overexpressed can drive cancers. We broadly characterized the MYC-driven surfaceome in B cells and prostate cells using proteomics. MYC overexpression induces large bidirectional changes in the surfaceome through broad up-regulation of >80 metabolite transporters important for cell proliferation and paradoxical up-regulation of two receptors involved in cell turnover such as a TNF receptor family member and a natural killer cell activating ligand. We targeted these two receptors using recombinant bispecific T cell engagers (BiTEs) to kill MYC overexpressing cells. These cells are also more sensitive to toxic nucleosides to two up-regulated nucleoside transporters. Our studies identify surface targets or combinations thereof as possible candidates for immunotherapy or cytotoxic metabolites.
Kěài ‘cute’ in Mandarin
Authors: Chen Yu-Chieh , Li Jen-i
Published: January 2021

The word kěài in Mandarin is semantically rich. However, little research has been devoted to examining
its meanings and uses, let alone possible innovative usage following the popularity of social media platforms. Hence, this study aims to
examine in detail (a) the descriptive range, meanings and functions of kěài, and (b) possible changes of its usage in
Internet communication. To achieve these goals, a total of 800 tokens of kěài were collected and analyzed–400 from the
Sinica Corpus and 400 from two widely used social media platforms, representing the data before and after social media platforms became
popular. Our major findings are: First, although human beings and non-human objects are what kěài mostly
describes, its descriptive range is shifting to more abstract entities for much higher percentages of Abstract Entity and Event are found on
the social media platforms. Second, the influence of age and gender factors has weakened. Third, although most of the non-human cases are
described as kěài due to their external features, most of the human cases in the Sinica Corpus are called
kěài for their external features while on the social media platforms, for their non-external features. Fourth,
kěài conveys positive meanings most of the time, and the three most frequently found meanings of kěài in
the Sinica Corpus are different from those on the social media platforms. Fifth, kěài is found to serve as hedges in both
sets of data, but it is also used to show surprise on the social media platforms.
A corpus-based investigation of semantic and syntactic differences between the two major future tense constructions
Authors: Yeh Tzu-Fen
Published: January 2021

English has two major future tense constructions,willandbe going to. Additionally, English can also use the present tense with a future-marking adverbial to express futurity. However, the distributions of these future markers are not free but limited. Instead of discriminating the differences among these distributions through direct comparison to etymological meanings or intuitive examples, this study offers an account for the semantic and syntactic differences between the two major English future tense constructions by analyzing data retrieved from the British National Corpus (BNC). The focus of attention is chiefly on the semantic and syntactic differences that lead to the choices British English native speakers make when expressing futurity. Based on the empirical analysis of data from the BNC, this study demonstrates that distribution of the future tense constructions seems sensitive to the following factors: (1) event-time orientation (temporal posteriority) or present-time orientation (prospective aspect), (2) the levels of verbal dynamicity in the whole sentence, (3) contexts of subordination, and (4) different text categories. The analysis suggests that the futurity constructions are not in the same distribution but are semantically and syntactically different. Utilizing its findings, this study aims to enhance second language learners’ expression of futurity by providing pedagogical suggestions.
Unitarity and the information problem in an explicit model of black hole evaporation
Authors: Schindler Joseph , Frangipane Evan , Aguirre Anthony
Published: January 2021

We consider the black hole information problem in an explicitly defined spacetime modeling black hole evaporation. Using this context we review basic aspects of the problem, with a particular effort to be unambiguous about subtle topics, for instance precisely what is meant by entropy in various circumstances. We then focus on questions of unitarity, and argue that commonly invoked semiclassical statements of long term, evaporation time, and Page time ‘unitarity’ may all be violated even if physics is fundamentally unitary. This suggests that there is no horizon firewall. We discuss how the picture is modified for regular (nonsingular) evaporation models. We also compare our conclusions to recent holographic studies, and argue that they are mutually compatible.
Geometric mean of bimetric spacetimes
Authors: Kocic Mikica
Published: January 2021

We use the geometric mean to parametrize metrics in the Hassan–Rosen ghost-free bimetric theory and pose the initial-value problem. The geometric mean of two positive definite symmetric matrices is a well-established mathematical notion which can be under certain conditions extended to quadratic forms having the Lorentzian signature, say metrics g and f. In such a case, the null cone of the geometric mean metric h is in the middle of the null cones of g and f appearing as a geometric average of a bimetric spacetime. The parametrization based on h ensures the reality of the square root in the ghost-free bimetric interaction potential. Subsequently, we derive the standard n + 1 decomposition in a frame adapted to the geometric mean and state the initial-value problem, that is, the evolution equations, the constraints, and the preservation of the constraints equation.
Symmetry restriction and its application to gravity
Authors: Kamiński Wojciech , Liegener Klaus
Published: January 2021

In the Hamiltonian formulation, it is not a priori clear whether a symmetric configuration will keep its symmetry during evolution. In this paper, we give precise requirements of when this is the case and propose a symmetry restriction to the phase space of the symmetric variables. This can often ease computation, especially when transcending from the infinite dimensional phase space of a field theory to a possibly finite dimensional subspace. We will demonstrate this in the case of gravity. A prominent example is the restriction of full general relativity in its Hamiltonian formulation to the cosmological configurations of Robertson–Walker type. We will demonstrate our procedure in this setting and extend it to examples that appear useful in certain approaches to quantum gravity.
Infinite degeneracy of Landau levels from the Euclidean symmetry with central extension revisited
Authors: Murgan Rajan
Published: January 2021

The planar Landau system which describes the quantum mechanical motion of a charged particle in a plane with a uniform magnetic field perpendicular to the plane, is explored within pedagogical settings aimed at the beginning graduate level. The system is known to possess the Euclidean symmetry in two dimensions with central extension

E

̄

(

2

)

. In this paper, we revisit the well-known energy eigenvalues of the system, known as the Landau levels, by exploiting the related

e

̄

(

2

)

symmetry algebra. Specifically, we utilize the Casimir operator and the commutation relations of the generators of the

E

̄

(

2

)

group. More importantly, an algebraic formalism on this topic based on Schwinger’s oscillator model of angular momentum is also presented. The dimensions of irreducible representations of the

E

̄

(

2

)

group and their implications on the degeneracy of Landau levels is discussed.
BAlN for III-nitride UV light-emitting diodes: undoped electron blocking layer
Authors: Gu Wen , Lu Yi , Lin Rongyu , Guo Wenzhe , Zhang Zihui , Ryou Jae-Hyun , Yan Jianchang , Wang Junxi , Li Jinmin , Li Xiaohang
Published: January 2021

The undoped BAlN electron-blocking layer (EBL) is investigated to replace the conventional AlGaN EBL in light-emitting diodes (LEDs). Numerical studies of the impact of variously doped EBLs on the output characteristics of LEDs demonstrate that the LED performance shows heavy dependence on the p-doping level in the case of the AlGaN EBL, while it shows less dependence on the p-doping level for the BAlN EBL. As a result, we propose an undoped BAlN EBL for LEDs to avoid the p-doping issues, which a major technical challenge in the AlGaN EBL. Without doping, the proposed BAlN EBL structure still possesses a superior capacity in blocking electrons and improving hole injection compared with the AlGaN EBL having high doping. Compared with the Al0.3Ga0.7N EBL with a doping concentration of 1 × 1020 cm−3, the undoped BAlN EBL LED still shows lower droop (only 5%), compatible internal quantum efficiency (2% enhancement), and optical output power (6% enhancement). This study provides a feasible route to addressing electron leakage and insufficient hole injection issues when designing ultraviolet LED structures.
Diffusion charging of nanometer-sized liquid aerosol particles
Authors: Yang Yong , Zhang Haoqin , Li Chuan , Li Chi , Yu Ziheng , Yu Kexun
Published: January 2021

Aerosol particles play an important role in atmospheric physical or chemical reactions. Charging of aerosol particles is also widely used in various engineering applications, such as electrical low-pressure impactors and differential mobility analyzers. In this paper, the charging process of nanometer-sized liquid aerosol particles in an atmospheric environment is studied theoretically and experimentally. The traditional charging equation is modified taking the variation of carried charges and the number density of liquid aerosol particles into consideration, due to the coalescence of liquid aerosol particles that brings 100% charge conversion efficiency. By fitting the experimental data under a low discharge voltage, an appropriate combination (r, η) is selected, where r is a specific droplet radius and η is the corresponding equivalent conversion factor of charges. The results from the fitting combination (r, η) are in good agreement with the experimental data and it further demonstrates that the charging evolution of droplets with various radiuses under various voltages can be derived from the existing experimental data under a low voltage. In addition, the concept of a charging time constant τ
0.1 is introduced to describe the charging rate. This paper may provide a reference to reveal and optimize the charging process of liquid aerosol particles and broaden the engineering applications for the charging of aerosol particles.
Comparison of high-k Y2O3/TiO2 bilayer and Y-doped TiO2 thin films on Ge substrate
Authors: Kim Dong Gun , Kim Hae-Ryoung , Kwon Dae Seon , Lim Junil , Seo Haengha , Kim Tae Kyun , Paik Heewon , Lee Woongkyu , Hwang Cheol Seong
Published: January 2021

Y2O3/TiO2 bilayer thin films and Y-doped TiO2 (YTO) thin films were deposited on a Ge substrate by atomic layer deposition at a substrate temperature of 250 °C. They were used as gate insulators to examine the electrical properties of Pt/TiN/TiO2/Y2O3/p-Ge and Pt/TiN/YTO/p-Ge metal–oxide–semiconductor capacitors. A 7 nm thick bilayer thin film showed a lower leakage current density by more than one order of magnitude compared to a YTO thin film with the same thickness due to the high conduction band offset between the Y2O3 layer and Ge substrate. However, the bilayer thin film showed a large hysteresis of 950 mV. On the other hand, the YTO thin film showed significantly reduced hysteresis of 120 mV due to the smaller slow trap density. The voltage acceleration factors of the bilayer thin film and YTO thin film were 1.12 and 1.25, respectively, higher in the YTO thin film. The interfacial trap density of the 7 nm thick bilayer and YTO thin films were 3.5 × 1011 cm−2 eV−1 and 2.7 × 1011cm−2 eV−1, respectively. The equivalent oxide thickness of the YTO film could be scaled down to 0.9 nm, and a leakage current density of 1.4 × 10−4A cm−2 at flat band voltage −1 V was achieved. This study confirmed that the YTO film can be used as a promising ternary high-k oxide for a Ge-based field-effect-transistor.
Perpendicular magnetic anisotropy induced by La2/3Sr1/3MnO3–YBaCo2O5+δ
interlayer coupling
Authors: Han Furong , Chen Xiaobing , Wang Jianlin , Huang Xudan , Zhang Jine , Song Jinghua , Liu Banggui , Chen Yuansha , Bai Xuedong , Hu Fengxia , Shen Baogen , Sun Jirong
Published: January 2021

Heterostructure with a symmetry-mismatched interface provides a promising playground for the exploration of emergent phenomena. Herein, we report a systematic investigation on La2/3Sr1/3MnO3/YBaCo2O5+δ
(LSMO/YBCO) grown on SrTiO3, a heterostructure formed by perovskite oxides of different symmetry. A high-resolution lattice image shows the formation of high-quality perovskite LSMO and A-site cation-ordered oxygen-deficient double perovskite YBCO, without any signatures of atomic reconfiguration at the interface. Surprisingly, the YBCO-buffered LSMO exhibits perpendicular magnetic anisotropy (PMA), though bare LSMO film is in-plane anisotropic. The PMA is robust, appearing even when the thickness of YBCO is only one unit cell. The typical anisotropy constant is ∼4 × 106 erg cm−3. X-ray absorption spectroscopy analysis reveals a preferential occupation of the

d

3

z
2

−

r
2

orbital compared with

d

x
2

−

y
2

, which is confirmed by density functional theory calculations. This orbital reconstruction accounts for the PMA. The formation of a covalent bond between Mn and Co caged by different oxygen polyhedrons, an octahedron and a square pyramid, respectively, stabilizes the orbital reconstruction, resulting in anomalous spin orientation.
Study of the 33Cl spectroscopic factors via the 32S(3He, d)33Cl one-proton transfer reaction
Authors: Lombardo I , Dell'Aquila D , Cinausero M , Gasques L R , Vigilante M , Zagatto V A B , Barlini S , Bolzonella R , Bruno M , Buccola A , Camaiani A , Carturan S M , Casini G , Ciampi C , Cicerchia M , D'Andrea M , Degerlier M , Fabris D , Frosin C , Gramegna F , Lepine-Szily A , Maggioni G , Mantovani G , Marchi T , Ordine A , Ottanelli P , Pasquali G , Piantelli S , Rigato V , Russo M , Scomparin L , Valdrè S , Verde G
Published: January 2021

In this paper we discuss new experimental data on the one-proton transfer reaction 32S(3He, d)33Cl* at 9.68 MeV bombarding energy. An enriched 32S target and a high-granularity hodoscope were used to obtain data for proton transfer reactions to bound and unbound states in 33Cl. Angular distributions were interpreted by means of finite-range DWBA and coupled-channel calculations. The obtained spectroscopic factors have been compared with previous results reported in the literature and with shell model calculations.
Stabilities and catapults of truncated carbon nanocones
Authors: Dong Shuhong , Liu Jun , Zhang Zi-Yue , Li Yongheng , Huang Ruiyu , Zhao Junhua
Published: January 2021

Truncated carbon nanocones (CNCs) can be taken as energy suppliers because of their special structures. In this paper, we demonstrate the stability of truncated CNCs under compression and the escape behavior of a fullerene catapulted from a compressed CNC by molecular dynamics simulations and theoretical models. The strain energy of a CNC and cohesive energy between a fullerene and the CNC (due to their van der Waals interactions) dominate the stability and catapulting capability of the cone, which strongly depend on geometrical parameters (apex angle, top radius and height) of each CNC and axial distances between them. In particular, the additional transverse vibration of buckled CNCs after released plays a significant role in their catapulting abilities and efficiencies. Finally, finite element method and experiments are further performed to validate the escape mechanism. This study should be of great importance to providing a theoretical support for designing novel nanodevices in mico/nanoelectromechanical systems.
Introducing ferromagnetism and anisotropic magnetoresistance in monolayer CVD graphene by nitrogen doping
Authors: Singla Robin , Shukla Ambika Shankar , Kottantharayil Anil
Published: January 2021

We demonstrate a method to dope monolayer chemical vapor deposited (CVD) graphene with nitrogen and make it ferromagnetic. CVD graphene was first functionalized with hydroxyl groups by treating with H2O2 in the presence of UV light and then annealed in ammonia gas to dope it with nitrogen. Magnetization measurements showed a ferromagnetic hysteresis loop at low temperatures with a coercivity of 222 Oe at 2 K. We also investigated the effect of a change in the angle of the applied magnetic field on the anisotropic magnetoresistance effect (AMR) in the doped CVD graphene devices. Graphene shows positive AMR for temperatures from 2 K to 50 K, negative AMR at 100 K and 150 K, and no AMR for temperatures higher than 150 K. A maximum AMR of 0.92% was observed at 2 K for an in-plane magnetic field of 30 kOe. Magnetic force microscopy also confirms the introduction of magnetism in CVD graphene after doping, and electron spin resonance spectroscopy shows resonance when scanned in a magnetic field, which confirms the presence of unpaired electrons in doped graphene. The process introduced in this paper for nitrogen doping of graphene with attendant magnetism could pave the way for the applications of graphene in spintronics and other devices.
Composites of ion-in-conjugation polysquaraine and SWCNTs for the detection of H2S and NH3 at ppb concentrations
Authors: Zhou Jin , Järvinen Topias , Pitkänen Olli , Kónya Zoltán , Kukovecz Akos , Kordas Krisztian
Published: January 2021

Several different methods are established for the analysis of gases, including optical spectroscopy, photoacoustic spectroscopy as well as colorimetric and resistive sensing, the measurements systems are either too complex or have limited sensitivity. In particular, when the goal is to apply a large number of sensors in networks, it is highly desirable to have devices that are simple, have low cost and energy consumption, yet sensitive and selective to monitor analytes even in traces. Herein, we propose a new type of resistive sensor device based on a composite of single-wall carbon nanotubes and an ion-in-conjugation polymer, poly(1,5-diaminonaphthalene-squaraine), capable of detecting H2S and NH3 in air even at room temperature with a theoretical concentration limit of ∼1 ppb and ∼7 ppb, respectively. Density functional theory calculations revealed that H atoms of the analytes and O atoms of the polymer chain interact and form hydrogen bonds, and the electron withdrawal from the gas molecules by the polymer chain results in the change of its electrical conductivity. To demonstrate the feasibility of the new nanocomposites in sensing, we show the devices for monitoring food safety with good sensor stability of operation for at least 3 months of period of time.
Imaging the response to deep brain stimulation in rodent using functional ultrasound
Authors: Nayak Rohit , Lee Jeyeon , Chantigian Siobhan , Fatemi Mostafa , Chang Su-Youne , Alizad Azra
Published: January 2021

In this study, we explored the feasibility of using functional ultrasound (fUS) imaging to visualize cerebral activation associated with thalamic deep brain stimulation (DBS), in rodents. The ventrolateral (VL) thalamus was stimulated using electrical pulses of low and high frequencies of 10 and 100 Hz, respectively, and multiple voltages (1–7 V) and pulse widths (50–1500 μs). The fUS imaging demonstrated DBS-evoked activation of cerebral cortex based on changes of cerebral blood volume, specifically at the primary motor cortex (PMC). Low frequency stimulation (LFS) demonstrated significantly higher PMC activation compared to higher frequency stimulation (HFS), at intensities (5–7 V). Whereas, at lower intensities (1–3 V), only HFS demonstrated visible PMC activation. Further, LFS-evoked cerebral activation was was primarily located at the PMC. Our data presents the functionality and feasibility of fUS imaging as an investigational tool to identify brain areas associated with DBS. This preliminary study is an important stepping stone towards conducting real-time functional ultrasound imaging of DBS in awake and behaving animal models, which is of significant interest to the community for studying motor-related disorders.
A 4D flow cardiovascular magnetic resonance study of flow asymmetry and haemodynamic quantity correlations in the pulmonary artery
Authors: Gbinigie Henrike , Coats Louise , Parikh Jehill D , Hollingsworth Kieren G , Gan Lian
Published: January 2021

Objective. In this paper we elucidate the asymmetric flow pattern and the haemodynamic quantity distributions and correlations in the pulmonary artery (PA) vasculature in healthy adults having structurally normal hearts, to provide reference on the flow characteristics in the PA and the right ventricle.Approach. Velocity data are acquired non-invasively from 18 healthy volunteers by 4D flow magnetic resonance imaging, resolved to 20 phases with spatial resolution 3 × 3 × 3 mm3. Interpolation is applied to improve the accuracy in quantifying haemodynamic quantities including kinetic energy, rotational energy, helicity and energy dissipation rate. These quantities are volumetrically normalised to remove size dependency, representing densities or local intensity.Main results. Flow asymmetry in the PA is quantified in terms of all the flow dynamic quantities and their correlations. The right PA has larger diameter and higher peak stroke velocity than the left PA. It also has the highest rotational energy intensity. Counter-rotating helical streams in the main PA appear to be associated with the unidirectional helical flow noticed in the left and the right PA near the peak systole.Significance. This study provides a fundamental basis of normal flow in the PA. It implies the validity to use these flow pattern-related quantitative measures to aid with the identification of abnormal PA flow non-invasively, specifically for detecting abnormalities in the pulmonary circulation and response to therapy, where haemodynamic flow is commonly characterised by increased vortical and helical formations.
Capacitively-coupled ECG and respiration for the unobtrusive detection of sleep apnea
Authors: Deviaene Margot , Castro Ivan D , Borzée Pascal , Patel Aakash , Torfs Tom , Buyse Bertien , Testelmans Dries , Van Huffel Sabine , Varon Carolina
Published: January 2021

Objective. The performance of a novel unobtrusive system based on capacitively-coupled electrocardiography (ccECG) combined with different respiratory measurements is evaluated for the detection of sleep apnea. Approach. A sleep apnea detection algorithm is proposed, which can be applied to electrocardiography (ECG) and ccECG, combined with different unobtrusive respiratory measurements, including ECG derived respiration (EDR), respiratory effort measured using the thoracic belt (TB) and capacitively-coupled bioimpedance (ccBioz). Several ECG, respiratory and cardiorespiratory features were defined, of which the most relevant ones were identified using a random forest based backwards wrapper. Using this relevant feature set, a least-squares support vector machine classifier was trained to decide if a one minute segment is apneic or not, based on the annotated polysomnography (PSG) data of 218 patients suspected of having sleep apnea. The obtained classifier was then tested on the PSG and capacitively-coupled data of 28 different patients. Main results. On the PSG data, an AUC of 76.3% was obtained when the ECG was combined with the EDR. Replacing the EDR with the TB led to an AUC of 80.0%. Using the ccECG and ccBioz or the ccECG and TB resulted in similar performances as on the PSG data, while using the ccECG and ccECG-based EDR resulted in a drop in AUC to 67.4%. Significance. This is the first study which tests an apnea detection algorithm on capacitively-coupled ECG and bioimpedance signals and shows promising results on the capacitively-coupled data set. However, it was shown that the EDR could not be accurately estimated from the ccECG signals. Further research into the effect that respiration has on the ccECG is needed to propose alternative EDR estimates.
Experimental demonstration of plasma mass separation in a configuration with a potential well and crossed electric and magnetic fields
Authors: Liziakin G , Antonov N , Usmanov R , Melnikov A , Timirkhanov R , Vorona N , Smirnov V S , Oiler A , Kislenko S , Gavrikov A , Smirnov V P
Published: January 2021

One of the alternative ‘dry’ methods for spent nuclear fuel (SNF) reprocessing is the plasma mass separation technique. This letter describes the first experiments that demonstrate the fundamental feasibility of a plasma mass separation approach in crossed electric and magnetic fields in collisionless mode. The Ag + Pb mixture was used to simulate the heavy (>235 u) and light (<150 u) components of the SNF. The Ag + Pb mixture was transformed into a plasma jet and ejected along the magnetic field. The action of the electric field caused the deposition of mixture components on the substrate in the form of localized spots. The estimated separation factor was of 35.
Eigenvalue solution for the ion-collisional effects on the fast and slow ion acoustic waves in multi-ion species plasmas
Authors: Zhang S T , Zhou Y Z , Yang T , Xie R , Jiang Y , Ban S S , Feng Q S , Wang Y X , Qiao B , Liu Z J , Cao L H , Zheng C Y
Published: January 2021

The fast and slow waves in multi-ion species collisionless plasmas have been widely studied, but the collision effect on ion acoustic waves is a difficult problem. In this paper, plasmas with azimuthal symmetry velocity distribution in different collisional regimes are studied by eigenvalue solution of the linearized Fokker–Planck equation. The frequency, damping rate and distribution function from the solutions are consistent with the analytical result in collisionless limit. For the fast wave, the damping rate agrees well with the prediction of both fluid theory in collision limit and kinetic theory in collisionless limit. But for the slow wave, the frequency and damping rate predicted by fluid theory are not accurate. In two-ion species plasmas, the light and heavy ion density perturbation phases of two-ion species are the same for the fast wave, but opposite for the slow wave. Polytropic index of C5H12 plasmas is also calculated, which is simply affected by mean-free paths of ions for the fast wave, but affected by multiple factors, such as mean-free paths, heat transfer and the opposite phases for the slow wave.
The evolution of properties and microstructure of Bi-2212 wires after gamma-ray irradiation
Authors: Zhang Zhen-Chuang , Zhou Hai-Shan , Qin Jing-Gang , Yang Dong-Sheng , Luo Guang-Nan
Published: January 2021

Among various high-temperature superconducting materials, Bi2Sr2CaCu2O8+x
(Bi-2212) is considered as one of the most promising candidates to fabricate superconductors for magnetic confinement fusion reactors. Considering that the superconductors will be subject to irradiation in nuclear reactors, the effects of gamma-ray irradiation on the superconducting properties of Bi-2212 wires is studied in the present work. Critical current (I
c) tests have been done for Bi-2212 wires with different gamma-ray irradiation doses and the variation of I
c is correlated to the change of microstructures. During the 12 T I
c tests, the normalized I
c first rises to 1.15 then decreases to 0.89 with the increase of irradiation time. Results from x-ray diffraction, Raman spectroscopy and x-ray photoelectron spectroscopy indicate that defects are produced within the gamma-ray irradiated samples. From the images of high resolution transmission electron microscopy, amorphous structure in the gamma-ray irradiated sample is discovered as well.
Manipulation of vortex arrays with thermal gradients by applying dynamic heat sources
Authors: Chen Zhidong , Yong Huadong , Zhou Youhe
Published: January 2021

In this paper, we investigate the manipulation of vortex arrays of magnetic flux by using dynamic heat sources in the superconducting strip. The time-dependent Ginzburg–Landau (TDGL) equations and the heat diffusion equation are numerically solved to study the effect of the dynamic heat sources and the vortex dynamics of the sample. Three distinct velocity ranges were shown to occur, depending on the vortex motion and the corresponding characteristics of the induced voltage. Due to the relationship among the driving force, viscous force, and vortex–vortex interaction, the vortex motion changes from direct motion to a roughly harmonic motion with the velocity of the heat source. Meanwhile, the electromagnetic performance of the sample is also related to the heat source parameters, the applied magnetic fields and the pinning centers. In addition, the thermal effect leads to a more complex non-linear relationship between the induced voltage and the heat source velocity.
Resistivity, Hall effect, and anisotropic superconducting coherence lengths of HgBa2CaCu2O6 thin films with different morphology
Authors: Richter H , Lang W , Peruzzi M , Hattmansdorfer H , Durrell J H , Pedarnig J D
Published: January 2021

Thin films of the high-temperature superconductor HgBa2CaCu2O6 have been prepared on SrTiO3 substrates by pulsed-laser deposition of precursor films and subsequent annealing in mercury-vapor atmosphere. The microstructural properties of such films can vary considerably and have been analyzed by x-ray analysis and atomic force microscopy. Whereas the resistivity is significantly enhanced in samples with coarse-grained structure, the Hall effect shows little variation. This disparity is discussed based on models for transport properties in granular materials. We find that, despite of the morphological variation, all samples have similar superconducting properties. The critical temperatures T

c
∼ 121.2 K …122.0 K, resistivity, and Hall data indicate that the samples are optimally doped. The analyses of superconducting order parameter fluctuations in zero and finite magnetic fields yield the in-plane ξ

ab
(0) ∼ 2.3 nm …2.8 nm and out-of-plane ξ

c
(0) ∼ 0.17 nm …0.24 nm Ginzburg–Landau coherence lengths at zero temperature. Hall measurements provide estimates of carrier scattering defects in the normal state and vortex pinning properties in the superconducting state inside the grains.
Nanometric skyrmion lattice from anisotropic exchange interactions in a centrosymmetric host
Authors: Hirschberger Max , Hayami Satoru , Tokura Yoshinori
Published: January 2021

Skyrmion formation in centrosymmetric magnets without Dzyaloshinskii–Moriya interactions was originally predicted from unbiased numerical techniques. However, no attempt has yet been made, by comparison to a real material, to determine the salient interaction terms and model parameters driving spin-vortex formation. We identify a Hamiltonian with anisotropic exchange couplings, local ion anisotropy, and four-spin interactions, which is generally applicable to this class of compounds. In the representative system Gd3Ru4Al12, anisotropic exchange drives a fragile balance between helical, skyrmion lattice (SkL), and transverse conical (cycloidal) orders. The model is severely constrained by the experimentally observed collapse of the SkL with a small in-plane magnetic field. For the zero-field helical state, we further anticipate that spins can be easily rotated out of the spiral plane by a tilted magnetic field or applied current.
Bilinear Bäcklund transformation, soliton and breather solutions for a (3+1)-dimensional generalized Kadomtsev-Petviashvili equation in fluid dynamics and plasma physics
Authors: Shen Yuan , Tian Bo , Liu Shao-Hua , Yang Dan-Yu
Published: January 2021

A (3+1)-dimensional generalized Kadomtsev-Petviashvili equation in fluid dynam-ics and plasma physics is hereby investigated. Via the Hirota method, bilinear Bäcklund transformation are obtained, along with two types of the analytic solutions. Kink-shaped soliton solutions are derived via the Hirota method. Breather solutions are derived via the extended homoclinic test approach and lump solutions are obtained from the breather solutions under a limiting procedure. We find that the shape and amplitude of the one-kink soliton keep unchanged during the propagation and the velocity of the one-kink soliton depends on all the coefficients in the equation. We graphically demonstrate that the interaction between the two-kink solitons is elastic, and analyse the solitons with the influence of the coefficients. We observe that the amplitudes and shapes of the breather and lump remain unchanged during the propagation, and graphically present the breathers and lumps with the influence of the coefficients in the equation.
Vulnerability assessment of power system based on Theil entropy of branch potential energy
Authors: He Xiaofeng , Fan Wenli
Published: January 2021

To achieve the safe operation of power system and prevent cascading failures, a vulnerability assessment method of power system is proposed based on the state correlation of branch fault. Firstly, a weighted correlation network based on the branch potential energy is established by using the state transition relationship of the two-level cascading failures. Secondly, the vulnerability assessment model of power system is constructed by applying the Theil entropy theory into the weighted correlation network. Finally, the simulation results on IEEE_39 bus system and an actual power system show that the model can not only evaluate the vulnerability of power system effectively but also find the vulnerable branches in power network more accurately.
Bubble dynamics in a strong first-order quark-hadron transition *
Authors: Zhou Shuying , Shu Song , Mao Hong
Published: January 2021

We investigate the dynamics of a strong first-order quark-hadron transition driven by cubic interactions via homogeneous bubble nucleation in the Friedberg-Lee model. The one-loop effective thermodynamic potential of the model and the critical bubble profiles have been calculated at different temperatures and chemical potentials. By taking the temperature and the chemical potential as variables, the evolutions of the surface tension, the typical radius of the critical bubble, and the shift in the coarse-grained free energy in the presence of a nucleation bubble are obtained, and the limit on the reliability of the thin-wall approximation is also addressed accordingly. Our results are compared to those obtained for a weak first-order quark-hadron phase transition; in particular, the spinodal decomposition is relevant.
Fine structure of α decay in 222Pa *
Authors: Hua Wei , Zhang Zhiyuan , Ma Long , Gan Zaiguo , Yang Huabin , Yuan Cenxi , Huang Minghui , Yang Chunli , Zhang Mingming , Tian Yulin , Zhou Xiaohong
Published: January 2021

With the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system, the fine structure of the

decay for

Pa was studied. The nuclides were produced through the 1p3n evaporation channel via the heavy-ion induced fusion evaporation reaction

Ar +

W. Based on the ER-

-

-

and

-

correlation measurement, three new

decays were observed in addition to the three branches known previously. The one with the largest

decay energy was regarded as the ground state to ground state transition. The newly measured

decay properties of

Pa were examined in a framework of reduced width.