bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atomic force microscopy characterization of polyethylene terephthalate grafting with poly(styrene sulfonate)
Authors: Nguyen Tuan Ngoc , Humblot Vincent , Migonney Véronique , Lévy Raphaël 
Published: February 2022

Abstract
Polyethylene terephthalate (PET) is widely used to elaborate biomaterials and medical devices in particular for long-term implant applications but tuning their surface properties remains challenging. We investigate surface functionalization by grafting poly(sodium 4-styrene sulfonate, PNaSS) with the aim of enhancing protein adhesion and cellular activity. Elucidating the topography and molecular level organization of the modified surfaces is important for understanding and predicting biological activity. In this work, we explore several grafting methods including thermal grafting, thermal grafting in the presence of Mohr’s salt, and UV activation. We characterize the different surfaces obtained using atomic force microscopy (AFM), contact angle (CA), and x-ray photoelectron spectroscopy (XPS). We observe an increase in the percentage of sulfur atoms (XPS) that correlates with changes in (CA), and we identify by AFM characteristic features, which we interpret as patches of polymers on the PET surfaces. This work demonstrates tuning of biomaterials surface by functionalization and illustrates the capability of AFM to provide insights into the spatial organization of the grafted polymer.
Valleytronics in two-dimensional materials with line defect
Authors: Tian Hongyu , Ren Chongdan , Wang Sake 
Published: February 2022

Abstract
The concept of valley originates from two degenerate but nonequivalent energy bands at the local minimum in the conduction band or local maximum in the valence band. Manipulating the valley states for information storage and processing develops a brand-new electronics—valleytronics. Broken inversion symmetry is a necessary condition to produce pure valley currents. The polycrystalline two-dimensional materials (graphene, silicene, monolayer group-VI transition metal dichalcogenides, etc) with pristine grains stitched together by disordered grain boundaries (GBs) are the natural inversion-symmetry-broken systems and the candidates in the field of valleytronics. Different from their pristine forms, the Dirac valleys on both sides of GBs are mismatched in the momentum space and induce peculiar valley transport properties across the GBs. In this review, we systematically demonstrate the fundamental properties of valley degree of freedom across mostly studied and experimentally feasible polycrystalline structure—the line defect, and the manipulation strategies with electrical, magnetic and mechanical methods to realize the valley polarization. We also introduce an effective numerical method, the non-equilibrium Green’s function technique, to tackle the valley transport issues in the line defect systems. The present challenges and the perspective on the further investigations of the line defect in valleytronics are also summarized.
Origin of proton induced fluorescence quenching of colloidal carbon dots: reshaping of Schrödinger wavefunctions and huge red shift of transition energy
Authors: Zhang Chengyu , Dai Dejian , Zhao Guo , Lu Wei , Fan Jiyang 
Published: February 2022

Abstract
The fluorescence quenching by protons is a universal phenomenon but the mechanism remains unclear. Here, we take the fluorescent amide-terminated carbon dots as a prototype to study the proton fluorescence quenching mechanism by using both experiments and time-dependent density functional theory calculations. The study reveals that when an approached proton is captured by the weakly negatively charged fluorophore group of the colloidal carbon dot, it will substantially change the electron wavefunctions owing to the strong proton–electron interaction, and this leads to highly diminished energy gap and resultant fluorescence quenching in the visible spectral region. The protons generated by hydrolysis of various types of metal ions also exhibit fruitful fluorescence quenching and the quenching efficiency is roughly proportional to the hydrolysis constant of the metal ion. This fluorescence quenching mechanism is quite distinct from the conventional ones involving electron or energy transfer.
Mg-doped InSnO nanofiber field-effect transistor for methanol gas detection at room temperature
Authors: Li Linkang , Li Jun , Fu Wenhui , Jiang Dongliang , Song Yanjie , Yang Qiuhong , Zhu Wenqing , Zhang Jianhua 
Published: February 2022

Abstract
Research on high-performance gas sensors for detecting toxic and harmful methanol gas is still a very important issue. For gas sensors, it is very important to be able to achieve low concentration detection at room temperature. In this work, we used the electrospinning method to prepare Mg-doped InSnO nanofiber field-effect transistors (FETs) methanol gas sensor. When the Mg element doping concentration is 2.3 mol.%, InSnO nanofiber FET exhibits excellent electrical properties, including higher mobility of 3.17 cm2 V−1 s−1, threshold voltage of 1.51 V, subthreshold swing of 0.42 V/decade, the excellent on/off current ratio is about 108 and the positive bias stress stability of the InSnO nanofiber FET through Mg doping has been greatly improved. In addition, the InSnMgO nanofiber FET gas sensor exhibits acceptable gas selectivity and sensitivity to methanol gas at room temperature. In the methanol gas sensor test at room temperature, when the methanol gas concentration is 60 ppm at room temperature, the response value of the InSnMgO nanofiber FET gas sensor is 81.92; and when the methanol concentration is 5 ppm, the response value is still 1.21. This work provides an effective and novel way to build a gas sensor at room temperature and use it to detect methanol gas at room temperature.
A physics-based machine learning approach for modeling the complex reflection coefficients of metal nanowires
Authors: Wu Xiaoqin , Wang Yipei 
Published: February 2022

Abstract
Metal nanowires are attractive building blocks for next-generation plasmonic devices with high performance and compact footprint. The complex reflection coefficients of the plasmonic waveguides are crucial for estimation of the resonating, lasing, or sensing performance. By incorporating physics-guided objective functions and constraints, we propose a simple approach to convert the specific reflection problem of nanowires to a universal regression problem. Our approach is able to efficiently and reliably determine both the reflectivity and reflection phase of the metal nanowires with arbitrary geometry parameters, working environments, and terminal shapes, merging the merits of the physics-based modeling and the data-driven modeling. The results may provide valuable reference for building comprehensive datasets of plasmonic architectures, facilitating theoretical investigations and large-scale designs of nanophotonic components and devices.
COREDIV modelling of nitrogen and krypton seeding at the ASDEX Upgrade tokamak
Authors: Ivanova-Stanik I , Zagórski R , Chomiczewska A , Bernert M , Glöggler S , Kallenbach A 
Published: February 2022

Abstract
Self-consistent core-scrape-off layer numerical simulations of an ASDEX-Upgrade discharge where the nitrogen (N) seeding is gradually replaced with the krypton (Kr) seeding during the plasma current flat-top phase are presented. These simulations are performed with the COREDIV code focusing on the prediction of the impurity evolution (W, Kr, N) with matched global plasma parameters: total and core radiation, temperature at the target plate and W concentration. The numerical results are compared with experimental measurements for shot #30503 at three different time points: 2.5 s (only N seeding), 4.2 s (N + Kr seeding) and 5.2 s (only Kr seeding). The calculated electron temperature at the divertor plate can be reduced to 3 eV with the highest Kr seeding. A good agreement between modelling results and experimental observations is reported.
Conventional and non-conventional diagnostics of a stable atmospheric pressure DC normal glow microplasma discharge intended for in situ TEM studies
Authors: Hansen Luka , Kohlmann Niklas , Schürmann Ulrich , Kienle Lorenz , Kersten Holger 
Published: February 2022

Abstract
A simple setup utilizing parallel flat electrodes with a 50–150 μm interelectrode distance divided by a Kapton spacer with a 1 mm diameter whole as discharge region intended for in situ transmission electron microscope studies is presented. The rather small setup operated in Ar or He results in an atmospheric pressure DC normal glow discharge and is investigated using various diagnostics. I–V characteristics show a glow-like behavior of the microplasma. Significant differences due to the working gas, electrode material and electrode distance have been observed. Currents in the range of 0.5–3 mA resulted in electrode potentials of 140–190 V for most experimental conditions. Optical emission spectroscopy and imaging revealed stable plasma operation and enabled the determination of current densities (approx. 16 mA mm−2 for He, or 28 mA mm−2 for Ar) independent of the input current as the discharge channel grows in diameter. Sheath thicknesses in the range of a few μm have been calculated by the collision-dominated Child–Langmuir law and trends are confirmed by the optical imaging. Energy flux measurements revealed a pronounced effect of ions on the measurement process and resulted in high energy fluxes locally up to 275 W cm−2. Effective secondary electron emission coefficients ranging from 1 to 1.6 depending on the discharge conditions have been determined based on the energy balance at the cathode.
Determining causality in Hall effect thrusters using extended convergent cross mapping: II*
Authors: Huerta C E , Martin R S , Eckhardt D Q , Koo J W 
Published: February 2022

Abstract
Extended convergent cross mapping was previously shown to be a powerful tool for analyzing the dynamics of Hall-effect thrusters and has applications in many diverse fields. Due to its limitations, data splitting and self-reconstruction are introduced for robustness, and the results are judiciously used to eliminate inconclusive and false links (sample scenarios are discussed). The analysis is then applied to Hall-effect thruster data, and the results are used to construct causality network graphs that map the flow of information inside the thruster. Two operating modes are studied: quiescent and oscillatory. For both cases, the causality links qualitatively agree with calculated plumes and demonstrate that charged particles carry information about the currents throughout the experiment, as expected. Causal links carried by neutral particles or propagating through waves are possible, but outside the scope of this work. Additionally, the extended convergent cross mapping results can be used to estimate the first two harmonic frequencies in the oscillatory mode to great precision
High performance 4H-SiC MOSFET with deep source trench
Authors: Na Jaeyeop , Cheon Jinhee , Kim Kwangsoo 
Published: February 2022

Abstract
In this study, we investigated a 4H-SiC deep source trench metal-oxide semiconductor field-effect transistor (DST-MOSFET) using technology computer-aided design numerical simulations. The proposed DST-MOSFET comprises a P-pillar formed along with the DST and a side P+ shielding region (SPR), which replaces the gate trench bottom SPR. Owing to the superjunction generated by the P-pillar and N-drift region, the static characteristics of the DST-MOSFET were superior to those of the trench gate MOSFET (UMOSFET) and double-trench MOSFET (DT-MOSFET). The specific on-resistance and Baliga’s figure of merit of DST-MOSFET improved by 9% and 104%, respectively, in comparison with those of UMOSFET; and by 37% and 64%, respectively, compared to those of DT-MOSFET. Additionally, the SPR reduced the gate-to-drain capacitance of the DST-MOSFET and improved the switching characteristics. Consequently, the total switching energy loss of the proposed DST-MOSFET reduced by 63% and 47% in comparison with those of the UMOSFET and DT-MOSFET, respectively.
Harvesting electrical energy from water drops falling on a vibrating cantilever
Authors: Helseth L E 
Published: February 2022

Abstract
In this work a novel thin-film device combining piezoelectric and contact electrification energy harvesting is created with the aim of investigating how it responds to water droplet impact during vibrations. The two energy harvesting principles utilize the same ground electrode, but the electrical signal outputs are independent and show entirely different electrical signal characteristics in presence of external forcing. While piezoelectricity gives rise to a nearly quadratic increase in harvested energy as a function of vibration velocity, the energy due to contact electrification reaches saturation for larger water drop velocities. On the other hand, when the water stream transitions from discrete droplets to a continuous stream the energy gathered from the piezoelectric mechanism exhibits saturation, whereas the energy due to contact electrification decreases. The proposed device may have applications as a self-powered environmental sensor that allow one to distinguish between forced oscillations and water droplet impacts.
Coda wave interferometry-based very early stage bolt looseness monitoring using a single piezoceramic transducer
Authors: Chen Dongdong , Shen Zhouhui , Fu Ruili , Yuan Bo , Huo Linsheng 
Published: February 2022

Abstract
The traditional monitoring methods can only give warnings for the bolts with severe looseness. However, it is essential for the safety of bolted joints to detect the looseness of bolts at the very early stage. To this end, in this paper, coda wave interferometry (CWI)-based high-resolution bolt preload monitoring using a single piezoceramic transducer is proposed. According to the CWI and acoustoelastic theories, a theoretical model is established and the linear relationship between the time shifts of coda waves and the preload variations of the bolt is derived. An experiment, in which a piezoceramic transducer simultaneously functions as the actuator and sensor, was carried out to verify the effectiveness of the proposed method. Three lead zirconium titanate transducers at different locations of a bolted specimen are tested. The experimental results show that the time shifts of coda waves increase linearly with the decrease of bolt preload and the detectable resolution of bolt preload (DRBP) is up to 0.326%. The DRBP value proves that the proposed technique can successfully monitor bolt looseness at the very early stage. In addition, a comparison study is carried out between the CWI-based method and the energy-based wavelet packet decomposition (WPD) method, and the result shows that the preload sensitivity of the CWI-based method is about six times higher than that of the WPD approach. Therefore, the CWI-based method is an effective way for the in situ monitoring of bolt looseness, especially in the embryonic stage.
Improving the connectivity of MgB2 bulk superconductors by a novel liquid phase sintering process
Authors: Matthews G A B , Mousavi T , Santra S , Grovenor C R M , Grant P S , Speller S 
Published: February 2022

Abstract
This work investigates a new processing method developed to improve the connectivity of ex-situ MgB2 bulks at low sintering temperatures. Mg additions (1–10 wt.%) were mixed to pre-synthesised MgB2 to make composite powders that were sintered at 900 ∘C by the field assisted sintering technique. Addition of 10 wt.% Mg resulted in a substantial increase in density from 68% to 79% and a dramatic reduction in MgB4 from 11 to ∼0 wt.%. Pressure and dilatometry data recorded in-situ during the sintering process revealed that Mg additions led to different sintering mechanisms depending on the Mg fraction. For large Mg fractions (6 and 10 wt.%) a Mg liquid phase was formed and led to significant density improvements, and all pre-existing MgB4 was transformed into MgB2. A small amount of residual Mg remained in the bulks after the sintering process. Connectivity was improved with Mg additions, increasing four fold in the 10 wt.% Mg-MgB2 sample compared to unmodified MgB2. J

c
values at low field were also significantly improved by Mg additions, in particular the 6 and 10 wt.% Mg-MgB2 specimens showed J

c
(20 K, 0 T) values 4–5 times higher than for unmodified MgB2.
Prospects for assembling ultracold radioactive molecules from laser-cooled atoms
Authors: Kłos Jacek , Li Hui , Tiesinga Eite , Kotochigova Svetlana 
Published: February 2022

Abstract
Molecules with unstable isotopes often contain heavy and deformed nuclei and thus possess a high sensitivity to parity-violating effects, such as the Schiff moments. Currently the best limits on Schiff moments are set with diamagnetic atoms. Polar molecules with quantum-enhanced sensing capabilities, however, can offer better sensitivity. In this work, we consider the prototypical 223Fr107Ag molecule, as the octupole deformation of the unstable 223Fr francium nucleus amplifies the nuclear Schiff moment of the molecule by two orders of magnitude relative to that of spherical nuclei and as the silver atom has a large electron affinity. To develop a competitive experimental platform based on molecular quantum systems, 223Fr atoms and 107Ag atoms have to be brought together at ultracold temperatures. That is, we explore the prospects of forming 223Fr107Ag from laser-cooled Fr and Ag atoms. We have performed fully relativistic electronic-structure calculations of ground and excited states of FrAg that account for the strong spin-dependent relativistic effects of Fr and the strong ionic bond to Ag. In addition, we predict the nearest-neighbor densities of magnetic-field Feshbach resonances in ultracold 223Fr + 107Ag collisions with coupled-channel calculations. These resonances can be used for magneto-association into ultracold, weakly-bound FrAg. We also determine the conditions for creating 223Fr107Ag molecules in their absolute ground state from these weakly-bound dimers via stimulated Raman adiabatic passage using our calculations of the relativistic transition electric dipole moments.
Efficient rotational cooling of a cold beam of barium monofluoride
Authors: Courageux T , Cournol A , Comparat D , Viaris de Lesegno B , Lignier H 
Published: February 2022

Abstract
The ability to cool and trap a large number of molecules is currently a crucial challenge for the implementation of various applications in fundamental physics and cold chemistry. We here present an optical cooling of the internal degrees of freedom which maximizes the number of molecules in a minimum number of rotational states. Our demonstration is achieved on a supersonic beam of barium monofluoride seeded in argon, a process that leads to a rotational temperature T
rot ≈ 12 K. The rotation is then cooled by our optical pumping to approximately T
rot ≈ 0.8 K which, compared to the initial rotational distribution, corresponds to an increase of the number of molecules in the lowest rotational state by one order of magnitude. Our method employs two light sources coming from tapered amplifiers. The first source, dedicated to the rotational cooling of molecules occupying the fundamental vibrational level, is optimized thanks to a spectral shaping whose resolution is comparable to the separation of the relevant rotational levels. The second source is used to pump the molecules back to the fundamental vibrational level when they escape from it. This work focuses on the relevant features of these two types of optical pumping.
Al0.30Ga0.70N /GaN MODFET with triple-teeth metal for RF and high-power applications
Authors: Dubey Shashank Kumar , Islam Aminul 
Published: February 2022

Abstract
A modulation-doped field-effect transistor (MODFET) has been investigated in this paper. It is also called HEMT (high electron mobility transistor). The proposed MODFET is made up of Al0.30Ga0.70N as supply layer and GaN as channel or buffer layer, in which floating metal is embedded. Its T-gate is recessed to obtain higher gm, which results in improved RF characteristics. T-gate is used to minimize the gate resistance which reduces the power consumption of the proposed HEMT. A floating metal having triple teeth (TT), which resembles a comb is developed in GaN channel/buffer layer between the gate and drain electrodes to improve the device performance without increasing the dimensions of the device. The transition or cutoff frequency (f
T) of 125 GHz and unity power gain (also called) maximum oscillation) frequency (f
MAX) of 530 GHz at V
DS = 10 V with V
GS = 0.4 V have been reported in this paper. Analysis of power consumption of the proposed FET such as power gain (A
P), output power (P
OUT), and power-added efficiency (PAE) have been analyzed at 10 GHz in continuous wave mode and V
DS = 35 V have been analyzed. The value obtained for P
OUT, A
P, and PAE is 67.5 dBmW, 11.6 dB, and 24.6%, respectively. All the obtained results from the Silvaco TCAD software have been verified with the mathematical model.
Reflection and refraction of photons
Authors: Bersons Imants , Veilande Rita , Balcers Ojars 
Published: February 2022

Abstract
Three linear equations are proposed as quantum-mechanical equations for the free propagating photons. The solution of these equations is the vector potential of the electromagnetic field and it is a product of the Gaussian functions for the transverse coordinates and the eigenfunction of the harmonic oscillator for the longitudinal coordinate. This solutions is used to describe the reflection and refraction of photons on the boundary between two dielectrics. The amplitude of the reflected field coincides with the Fresnel formulae for the plane waves, but the amplitude of the refracted field is different. These amplitudes are the probability’s amplitudes of reflection and refraction of photons—like in the quantum mechanics. The photons propagated from the first into the second medium increase (decrease) their transverse size in the plane of incidence, if the refraction index of the second medium is greater (smaller) than in the first medium. The increasing or decreasing grow when increasing the angle of incidence. The difference between the quantum mechanics of the particles with a mass and the photons, as well as the interpretation of the wave function of photons, is discussed.
Constraints for electric charge from Maxwell’s equations and boundary conditions
Authors: Cameron Robert P 
Published: February 2022

Abstract
Certain boundary conditions constrain the forms that the electromagnetic field can take in a theory, in particular the boundary conditions inherent to closed spaces. According to Maxwell’s equations, this can give rise to constraints for the electric charge in the theory. We identify three such ‘boundary constraints’ for electric charge and highlight some of their myriad implications, touching upon a wealth of topics including the self-consistency of practical calculations, the nature of dark matter, the origin of electric-charge quantisation and the shape of the Universe. Furthermore, we explain that magnetic analogues of our boundary constraints offer new insights into the possible existence of magnetic monopoles and dyons.