bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study on physical modeling of flow mechanism in volumetric fracturing of tight oil reservoir
Authors: Zhao Xinli , Liu Xuewei , Yang Zhengming , Wang Fang , Zhang Yapu , Liu Guozhong , Lin Wei
Published: October 2021

This paper investigates the characteristics of oil–water two-phase flow after volumetric fracturing of horizontal wells in tight reservoirs. Based on a large-scale high-pressure, high-temperature experimental system for modeling horizontal well injection and production, the characteristics of the pressure distribution, cumulative liquid production, recovery factor, and liquid production rate of a matrix model and fractured model during the waterflooding process are compared and analyzed. The results show that, for both types of reservoirs, the fluid forms a high-pressure zone and a low-pressure zone during water injection. As the development progresses, the high-pressure zone continuously moves forward. There is a pressure step between the high-pressure zone and the low-pressure zone, which gradually decreases in magnitude as the pressure wave reaches the well. By this time, the main resistance before water breakthrough is the pressure step at the waterflooding front. The ultimate recovery is found to be 26.71% for the matrix model and 28.48% for the fractured model. Without an effective displacement system, the resistance of the horizontal well during waterflooding mainly acts on the oil–water interface. After the establishment of an effective displacement scheme, the resistance gradually expands to both sides of the water-swept zone. At this point, the formation of a dominant channel greatly weakens the displacement performance. Thus, it is necessary to rely on imbibition or surfactants in the later stages to improve the recovery factor.
Partially coherent perfect vortex beam generated by an axicon phase
Authors: Li Xiaofei , Wei Huazhe , Visser Taco D. , Cai Yangjian , Liu Xianlong
Published: October 2021

Vortex beams are structured light fields with a helical phase of the form exp (ilϕ) that carries an optical angular momentum (OAM) of lℏ per photon. Such beams typically have a ring-shaped intensity with a radius that varies with l. Perfect vortex (PV) beams are designed to have a radius that is approximately uniform over a certain OAM range. Here, we report how spatial coherence can be used to maintain a fixed ring shape over a larger propagation distance and for a greater OAM range than is possible for fully coherent vortex beams. Our work is relevant for the application of PV beams in areas such as trapping, tweezing, and optical communications.
Iron-deficiency response and differential expression of iron homeostasis related genes in spring wheat (
Authors: Kenzhebayeva Saule S. , Atabayeva Saule D. , Sarsu Fatma
Published: October 2021

Iron (Fe) is essential for plant growth and human health. Fe deficiency reduces yield and quality traits of wheat (Triticum aestivum L.). Grains of modern bread wheat varieties contain low levels of Fe, and Fe uptake and translocation in wheat grown in Fe conditions have not been studied in detail. This study investigates Fe homeostasis and biofortification in genetically stable spring wheat Almaken and Zhenis M5 mutant lines, developed with 200 Gy for higher grain Fe content. Mutant lines and parents were analysed for the expression of genes involved in Fe homeostasis under normal and deficient Fe. Wheat homologues of genes that participated in phytosiderophore (PS) synthesis and transport were significantly upregulated in the Fe-limited roots of Almaken M/1 and both Zhenis M/2 mutant lines, emphasising the role of deoxymugineic acid (DMA) in iron acquisition. The combined overexpression of SAMS, NAS1, TaNAAT, DMAS and TOM was also revealed in the roots of Almaken M/1 and both Zhenis M5 mutant lines, suggesting their involvement in PS synthesis, Fe chelation and transport. Under Fe deficiency, levels of TaYS1A encoding the wheat homologues of the metal-NA transporter YSL, also showed 2.6-, 5.1- and 5.9-fold increases in the roots of Almaken M/1 and both Zhenis M5 mutant lines, respectively. Vacuolar iron transporters (VIT2), natural resistance associated-macrophage protein (NRAMP) genes and the transcription factor basic-loop-helix (bHLH) were significantly upregulated under Fe starvation in shoots. Fe-deficiency-related genotype-dependent and tissue-specific gene expression differences provide new insights into genes involved in iron homeostasis and biofortification genes in wheat.
Effect of microstructure on the high cycle fatigue behaviour of DP 600 and SPFH 590 steels with and without a hole
Authors: Chatterjee Sudin , Chinara M. , Prasad A. D. , Jayabalan B. , Mahashabde V. , Mukherjee S.
Published: October 2021

The performance of ferrite-martensite (DP 600) and ferrite-pearlite (SPFH 590) steels with a similar tensile strength of ∼650 MPa under cyclic loading was investigated. This work presents the high cycle fatigue properties of DP 600 and SPFH 590 steel in the presence and absence of a hole. In presence of the hole, the fatigue strength for both the steels drops significantly, with drop being more for SPFH 590 steel. While the fatigue strength in absence of a hole is a strong function of yield strength of material, the behaviour in presence of the hole depends on the steel microstructure. The presence of martensite in case of DP 600 steel delayed the crack propagation by branching and crack tip blunting. Additionally, martensite  also increases the local strain, low angle grain boundary and dislocation density ahead of the crack tip, resulting in an increased  amount of plastic deformation and blunting of the crack tip.
Bidirectional regulation of calcium release–activated calcium (CRAC) channel by SARAF
Authors: Zomot Elia , Achildiev Cohen Hadas , Dagan Inbal , Militsin Ruslana , Palty Raz
Published: October 2021

Store-operated calcium entry (SOCE) through the Ca2+ release–activated Ca2+ (CRAC) channel is a central mechanism by which cells generate Ca2+ signals and mediate Ca2+-dependent gene expression. The molecular basis for CRAC channel regulation by the SOCE-associated regulatory factor (SARAF) remained insufficiently understood. Here we found that following ER Ca2+ depletion, SARAF facilitates a conformational change in the ER Ca2+ sensor STIM1 that relieves an activation constraint enforced by the STIM1 inactivation domain (ID; aa 475–483) and promotes initial activation of STIM1, its translocation to ER–plasma membrane junctions, and coupling to Orai1 channels. Following intracellular Ca2+ rise, cooperation between SARAF and the STIM1 ID controls CRAC channel slow Ca2+-dependent inactivation. We further show that in T lymphocytes, SARAF is required for proper T cell receptor evoked transcription. Taking all these data together, we uncover a dual regulatory role for SARAF during both activation and inactivation of CRAC channels and show that SARAF fine-tunes intracellular Ca2+ responses and downstream gene expression in cells.
Bone marrow runs the (bone) show
Authors: Karsenty Gerard
Published: October 2021

In this issue of JEM, a paper by Kim et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20211872), asking a simple question through a remarkable alliance of human and mouse genetics, demonstrates that a prevalent hematological condition can lead to osteoporosis. This work is important by virtue of the quality of its results and its implication for the relationship between bone and its marrow.
Gravitational quantum states as finite representations of the Lorentz group
Authors: Cianfrani Francesco
Published: October 2021

A manifestly Lorentz-covariant formulation of loop quantum gravity (LQG) is given in terms of finite-dimensional representations of the Lorentz group. The formulation accounts for discrete symmetries, such as parity and time-reversal, and it establishes a link with Wigner classification of particles. The resulting quantum model can be seen as LQG-like with the internal SU(2) ⊗ SU(2) group and it is free of the Immirzi parameter, while the scalar constraint is just the Euclidean part.
Analytical and numerical study of T-shaped plasmonic demultiplexer based on Fano and induced transparency resonances
Authors: Amrani M , Khattou S , Rezzouk Y , Mouadili A , Noual A , El Boudouti E H , Djafari-Rouhani B
Published: October 2021

We study analytically and numerically the design of plasmonic demultiplexers based on Fano and plasmonic induced transparency (PIT) resonances. The demultiplexers consist of T-shaped structures with an input waveguide and two output waveguides. Each output contains two waveguide stubs grafted either at the same position or at two different positions far from the input waveguide. We derive closed form analytical expressions of the geometrical parameters allowing a selective transfer of a single mode in one waveguide without affecting the other one. This is performed by implementing the Fano and PIT resonances which are characterized by a resonance placed near an antiresonance or placed between two antiresonances respectively. In particular, we show the possibility of trapped modes, also called bound in continuum (BIC) modes. These modes appear as resonances with zero width in the transmission spectra for appropriate lengths of the stubs. Then, by detuning slightly the stubs, BICs transform to PIT or Fano resonances. The existence of a full transmission besides a transmission zero, enables to filter a given wavelength on one output waveguide, by vanishing both the transmission on the second waveguide as well as the reflection in the input waveguide. The demultiplexer is capable to separate two fundamental optical windows (i.e. 1310 and 1550 nm). The performance of the demultiplexer platform is measured using the crosstalk of the two outputs and quality factor. The lowest value of the crosstalk −96.8 dB with an average of −84.7 dB is achieved and a maximum quality factor 45 is obtained. The maximum transmission reaches a high value of 85% despite the large metallic losses. These values are suitable for integrated photonic circuits in the optical communication. The analytical results are obtained by means of the Green’s function method which enables us to deduce the transmission and reflection coefficients, as well as the delay times and density of states. These results are confirmed by numerical simulations using a 2D finite element method. The analytical analysis developed in this work represent a predictive method to understand deeply different physical phenomena in more complex plasmonic devices.
Mimicking synaptic plasticity with a wedged Pt/Co/Pt spin–orbit torque device
Authors: Chen Shiwei , Mishra Rahul , Chen Huanjian , Yang Hyunsoo , Qiu Xuepeng
Published: October 2021

We fabricated a wedge-shaped Pt/Co/Pt device with perpendicular magnetic anisotropy and manifested that the Co magnetization can be solely switched by spin–orbit torque without any magnetic field. Similar to the synaptic weight, we observed that the state of Co magnetization (presented by the anomalous Hall resistance R
H) of the wedged Pt/Co/Pt device can be tuned continuously with a large number of nonvolatile levels by applied pulse currents. Furthermore, we studied the synaptic plasticity of the wedged Pt/Co/Pt device, including the excitatory postsynaptic potentials or inhibitory postsynaptic potentials and spiking-time-dependent plasticity. The work elucidates the promise of the wedged Pt/Co/Pt device as a candidate for a new type of artificial synaptic device that is induced by a spin current and paves a substantial pathway toward the combination of spintronics and synaptic devices.
Striations in moderate pressure dc driven nitrogen glow discharge
Authors: Tahiyat Malik M , Stephens Jacob C , Kolobov Vladimir I , Farouk Tanvir I
Published: October 2021

Plasma stratification has been studied for more than a century. Despite the many experimental studies reported on this topic, theoretical analyses and numerical modeling of this phenomenon have been mostly limited to rare gases. In this work, a one-dimensional fluid model with detailed kinetics of electrons and vibrationally excited molecules is employed to simulate moderate-pressure (i.e. a few Torrs) dc discharge in nitrogen in a 15.5 cm long tube of radius 0.55 cm. The model also considers ambipolar diffusion to account for the radial loss of ions and electrons to the wall. The proposed model predicts self-excited standing striations in nitrogen for a range of discharge currents. The impact of electron transport parameters and reaction rates obtained from a solution of local two-term and a multi-term Boltzmann equation on the predictions are assessed. In-depth kinetic analysis indicates that the striations result from the undulations in electron temperature caused due to the interaction between ionization and vibrational reactions. Furthermore, the vibrationally excited molecules associated with the lower energy levels are found to influence nitrogen plasma stratification and the striation pattern strongly. A balance between ionization processes and electron energy transport allows the formation of the observed standing striations. Simulations were conducted for a range of discharge current densities from ∼0.018 to 0.080 mA cm−2, for an operating pressure of 0.7 Torr. Parametric studies show that the striation length decreases with increasing discharge current. The predictions from the model are compared against experimental measurements and are found to agree favorably.
Field-induced deformation of ferromagnetic soft nanocomposites
Authors: Birster K , Schweitzer R , Schopphoven C , Tschöpe A
Published: October 2021

Uniaxial ferromagnetic Ni nanorods were prepared by the anodic aluminum oxide (AAO) template method. Reversible magnetization changes, measured perpendicular to the texture axis, were analyzed in terms of the Stoner–Wohlfarth model (SW). Using empirical model parameters, a quantitative and consistent description of the orientation- and field-dependent magnetic torque per particle was achieved. The model was extended (eSW) to take into account the local rotation of the magnetic nanorods in a soft-elastic matrix. The nanorods were characterized regarding their size, using transmission electron microscopy (TEM), their magnetic moment and colloidal volume fraction, determined from static field-dependent optical transmission (SFOT) measurements, and their rotational shape factor, obtained from oscillating field-dependent optical transmission (OFOT). The eSW-model was used in the simulation of simple bending and torsion of thin composite filaments. These simulations were compared with experimental results with the focus on the effect of finite magnetic anisotropy and local elastic rotation on the field-induced deformation of soft nanocomposites. The high sensitivity of thin filaments enabled the investigation of torque-induced deformation at nanorod volume density as low as 10−4 at which particle-particle interactions were negligible. In addition, reprogramming of the magnetic texture by magnetization reversal and the resulting modification in the deformation pattern was investigated.
Multi-phase equation of state of ultrapure hafnium to 120 GPa
Authors: Huston L Q , Velisavljevic N , Smith J S , Gray G T , Sturtevant B T
Published: October 2021

Hafnium (Hf) is an industrially important material due to its large neutron absorption cross-section and its high corrosion resistance. When subjected to high pressure, Hf phase transforms from its hexagonal close packed α-Hf phase to the hexagonal ω-Hf phase. Upon further compression, ω-Hf phase transforms to the body centered cubic β-Hf phase. In this study, the high pressure phase transformations of Hf are studied by compressing and decompressing a well-characterized Hf sample in diamond anvil cells up to 120 GPa while collecting x-ray diffraction data. The phase transformations of Hf were compared in both a He pressure transmitting medium (PTM) and no PTM over several experiments. It was found that the α-Hf to ω-Hf phase transition occurs at a higher pressure during compression and lower pressure during decompression with a helium (He) PTM compared to using no PTM. There was little difference in the ω-Hf to β-Hf phase transition pressure between the He PTM and no PTM. The equation of state was fit for all three phases of Hf and under both PTM and no-PTM.
Temperature tunable flexible photo absorbers based on near-infrared 1D photonic crystal hybridized W-doped VO2 nanostructures
Authors: Singh Dipti Umed , Narayanan Remya
Published: October 2021

Vanadium dioxide is a potential candidate for energy efficient smart windows and have crystalline phase transition temperature (T
c) at 68 °C. So far, literatures mainly emphasis on different synthetic strategies of tungsten doped VO2 which is a most effective dopant to reduce T
c of VO2 to near room temperatures. Until now, there is no report shows the incorporation of flexible 1D photonic crystals as spectrally selective, temperature tunable device to control the changes in optical transmission modulations of W-VO2 nanostrtcures, especially in the near IR region for smart window application. W-doped VO2 with various tungsten contents were synthesized with a facile hydrothermal route. We found that, with 1.1 at% of tungsten doping in intrinsic VO2, the metal to insulator transition temperature is brought down to 37 °C from 68 °C. IR transmission of VO2 thin film can be reduced from 70% to 40% around room temperature, after doping. Significant absorption enhancement has been observed for both VO2 and W-doped VO2 films, deposited over tunable SiO2/Ta2O5 based distributed Bragg reflector (DBR) fabricated over flexible PET (poly-ethylene terephthalate) substrates. On depositing VO2 over ∼70% reflecting DBR, optical transmission is reduced to ∼15% from 35% while the temperature varies to 380 K from 300 K in IR regime. Number of stacks plays a crucial role for effective IR extinctions. A high quality DBR is fabricated by increasing no. of stacks from 4 to 7, with optical transmission of DBR reduced to nearly 5% in stop band. However, with 1.1 at% of W-VO2 over such 95% reflecting flexible DBR, optical transmission vanishes nearly, around room temperature itself in the stop bands of that DBR, which clearly indicates the significant absorption enhancement. W-VO2/DBR hybrid can substantially modulate the solar heat flux and also imbuing DBR over flexible PET substrates offers retrofitting of the existing windows for energy economy. Thus these structures have promising potential applications for optical devices and practical design for smart windows.
Geant4-DNA modeling of nanodosimetric quantities in the Jet Counter for alpha particles
Authors: Pietrzak Marcin , Mietelska Monika , Bancer Aleksandr , Rucinski Antoni , Brzozowska Beata
Published: October 2021

The purpose of this work was to validate the calculation accuracy of nanodosimetric quantities in Geant4-DNA track structure simulation code. We implemented the Jet Counter (JC) nanodosimeter geometry in the simulation platform and quantified the impact of the Geant4-DNA physics models and JC detector performance on the ionization cluster size distributions (ICSD). ICSD parameters characterize the quality of radiation field and are supposed to be correlated to the complexity of the initial DNA damage in nanoscale and eventually the response of biological systems to radiation. We compared Monte Carlo simulations of ICSD in JC geometry performed using Geant4-DNA and PTra codes with experimental data collected for alpha particles at 3.8 MeV. We investigated the impact of simulation and experimental settings, i.e., three Geant4-DNA physics models, three sizes of a nanometer sensitive volume, gas to water density scaling procedure, JC ion extraction efficiency and the presence of passive components of the detector on the ICSD and their parameters. We found that ICSD in JC geometry obtained from Geant4-DNA simulations in water correspond well to ICSD measurements in nitrogen gas for all investigated settings, while the best agreement is for Geant4-DNA physics option 4. This work also discusses the accuracy and robustness of ICSD parameters in the context of the application of track structure simulation methods for treatment planning in particle therapy.
Effects of frequency on bubble-cloud behavior and ablation efficiency in intrinsic threshold histotripsy
Authors: Edsall Connor , Ham Emerson , Holmes Hal , Hall Timothy L , Vlaisavljevich Eli
Published: October 2021

Objective. Histotripsy is a non-thermal focused ultrasound ablation method that destroys tissue through the generation of a cavitation bubble cloud. Previous work studying intrinsic threshold histotripsy has shown that dense bubble clouds can be formed by a single-cycle pulse when the negative pressure exceeds an intrinsic threshold of ∼25–30 MPa, with the ablation efficiency dependent upon the size and density of bubbles within the cloud. This work investigates the effects of frequency on bubble-cloud behavior and ablation efficiency in intrinsic threshold histotripsy. Approach. A modular transducer was used to expose agarose tissue phantoms to 500 kHz, 1 MHz, or 3 MHz, histotripsy pulses. Optical imaging was used to measure the bubble-cloud dimensions, bubble density, and bubble size. The effects of frequency on ablation efficiency were also investigated by applying histotripsy to red blood cell (RBC) phantoms. Main results. Results revealed that the bubble-cloud size closely matched theoretical predictions for all frequencies. The bubble density, which is a measure of the number of bubbles per unit area, was shown to increase with increasing frequency while the size of individual bubbles within the cloud decreased at higher frequencies. Finally, RBC phantom experiments showed decreasing ablation efficiency with increasing frequency. Significance. Overall, results demonstrate the effects of frequency on histotripsy bubble-cloud behavior and show that lower frequency generates more efficient tissue ablation, primarily due to enhanced bubble expansion.
Axial momentum gains of ions and electrons in magnetic nozzle acceleration
Authors: Emoto Kazuma , Takahashi Kazunori , Takao Yoshinori
Published: October 2021

Fully kinetic simulations of magnetic nozzle acceleration were conducted to investigate the axial momentum gains of ions and electrons with electrostatic and Lorentz forces. The axial momentum gains per ion and electron are directly calculated from the kinetics of charged particles, indicating that electrons in the magnetic nozzle obtain the net axial momentum by the Lorentz force, even though they are decelerated by the electrostatic force. Whereas ions are also accelerated by the electrostatic force, the axial momentum gain of electrons increases significantly with increasing magnetic field strength and becomes dominant in the magnetic nozzle. In addition, it is clearly shown that the axial momentum gain of electrons is due to the electron momentum conversion from the radial to the axial direction, resulting in a significant increase in the thrust and exhaust velocity.
Fast state detection in F1-ATPase rotation enhanced by theory of mixed states and external torque
Authors: Le Luan Q , Volkán-Kacsó Sándor
Published: October 2021

During brief 120° transitions between long catalytic dwells, single F1-ATPase molecules exhibit angular jumps that vary with rotation angles. Using the angular jump profile enables the detection of fast states in the mechano-chemical scheme of the enzyme, states that are difficult to capture from single-molecule trajectories due to the fluctuations of the imaging nanoprobe. In a previous work, a short-lived, three occupancy state was postulated from a multi-state, probabilistic theory to explain the mean angular jump profile. An assumption in the theory was that the ‘mixing’ of chemical states is negligible during jumps. In a mixing event, two subsequent angular positions recorded by the imaging apparatus belong to two different chemical states of the motor enzyme due to fast reactions within a recording frame. In this paper, we provide an enhanced method for the detection of fast states. On one hand, we show using Langevin simulations that state mixing leads to faster mean angular jump, shifting up the profile. Consequently, the improved method provides a correction to the angular position and lifetime of the postulated three-occupancy metastable state. On the other hand, we show that when F1-ATPase is subject to torques opposing rotation in hydrolysis direction, the torques shift down the dwell angles without affecting the angle-dependent reaction rates. The torques improve detection capability for the fast state by increasing dwell times which is made evident by the flattening of the mean angular jump profile within 40°–60° from the catalytic dwell. In the three-occupancy state release of ADP occurs in concert with the binding of ATP to a different site in the F1-ATPase. Similarly, in the full ATP synthase when torques are created by the proton gradient in the FO region, the release of the product ATP is presumably accelerated by the binding of ADP to a different site in the F1 domain.
Effect of initial phase on the Rayleigh–Taylor instability of a finite-thickness fluid shell
Authors: Guo Hong-Yu , Cheng Tao , Li Jing , Li Ying-Jun
Published: October 2021

Rayleigh–Taylor instability (RTI) of finite-thickness shell plays an important role in deep understanding the characteristics of shell deformation and material mixing. The RTI of a finite-thickness fluid layer is studied analytically considering an arbitrary perturbation phase difference on the two interfaces of the shell. The third-order weakly nonlinear (WN) solutions for RTI are derived. It is found the main feature (bubble-spike structure) of the interface is not affected by phase difference. However, the positions of bubble and spike are sensitive to the initial phase difference, especially for a thin shell (kd < 1), which will be detrimental to the integrity of the shell. Furthermore, the larger phase difference results in much more serious RTI growth, significant shell deformation can be obtained in the WN stage for perturbations with large phase difference. Therefore, it should be considered in applications where the interface coupling and perturbation phase effects are important, such as inertial confinement fusion.
Exact solutions of the Schrödinger equation for a class of hyperbolic potential well
Authors: Wang Xiao-Hua , Chen Chang-Yuan , You Yuan , Lu Fa-Lin , Sun Dong-Sheng , Dong Shi-Hai
Published: October 2021

We propose a new scheme to study the exact solutions of a class of hyperbolic potential well. We first apply different forms of function transformation and variable substitution to transform the Schrödinger equation into a confluent Heun differential equation and then construct a Wronskian determinant by finding two linearly dependent solutions for the same eigenstate. And then in terms of the energy spectrum equation which is obtained from the Wronskian determinant, we are able to graphically decide the quantum number with respect to each eigenstate and the total number of bound states for a given potential well. Such a procedure allows us to calculate the eigenvalues for different quantum states via Maple and then substitute them into the wave function to obtain the expected analytical eigenfunction expressed by the confluent Heun function. The linearly dependent relation between two eigenfunctions is also studied.
Wavelength and sensitivity tunable long period gratings fabricated in fluid-cladding microfibers
Authors: Jin Wa , Zhang Linke , Zhang Xiang , Xu Ming , Bi Weihong , Qi Yuefeng
Published: October 2021

We report the fabrication of long period gratings in fluid-cladding microfibers by directly focusing a femtosecond laser beam on the microfibers surface to induce periodical modification a long one side of the microfibers. A long period grating is fabricated in a water-cladding microfiber with a diameter of ~ 5 μm, which demonstrates a resonant attenuation of 28.53 dB at wavelength of 1588.1 nm with 10 pitches. When water cladding is changed to be refractive index oil of n= 1.33 and alcohol solution with concentration of 5%, the resonance wavelength shifts to 1575.1 nm with resonant attenuation of 24.91 dB and 1594.1 nm with resonant attenuation of 35.9 dB, respectively. The long period grating demonstrates different temperature sensitivities of–0.524 nm/°C,–0.767 nm/°C and–1.316 nm/°C for water, alcohol solution and refractive index oil cladding microfibers, respectively, which means the alterable liquid cladding allows the availability of tunable wavelength and sensitivity. The fluid-cladding protects the microfibers from external disturbance and contamination and allows more flexibility in controlling the transmission property and sensing characteristics of long period gratings, which can be used as fiber devices and sensors for chemical, biological, and environmental applications.
Morphological and structural damage investigation of nanostructured molybdenum fuzzy surface after pulsed plasma bombardment
Authors: Luo Yu-Chuan , Yan Rong , Pu Guo , Wang Hong-Bin , Wang Zhi-Jun , Yang Chi , Yang Li , Guo Heng-Xin , Zhou Zhi-Bing , Chen Bo , Chen Jian-Jun , Gou Fu-Jun , Ye Zong-Biao , Zhang Kun
Published: October 2021

Steady high-flux helium (He) plasma with energy ranging from 50 eV to 90 eV is used to fabricate a fiber-form nanostructure called fuzz on a polycrystalline molybdenum (Mo) surface. Enhanced hydrogen (H) pulsed plasma in a wide power density range of 12 MW/m2–35 MW/m2 is subsequently used to bombard the fuzzy Mo, thereby simulating the damage of edge localized mode (ELM) to fuzz. The comparisons of surface morphologies, crystalline structures, and optical reflectivity between the original Mo and the Mo treated with various He+ energy and transient power densities are performed. With the increase of He ion energy, the Mo nano-fuzz evolved density is enlarged due to the decrease of filament diameter and optical reflectivity. The fuzz-enhanced He release should be the consequence of crystalline growth and the lattice shrinkage inside the Mo-irradiated layers (∼ 200 nm). The fuzz induced by lower energy experiences more severe melting damage and dust release under the condition of the identical transient H plasma-bombardment. The H and He are less likely to be trapped due to aggravated melting evidenced by the enhanced crystalline size and distinct lattice shrinkage. As the transient power density rises, the thermal effect is enhanced, thereby causing the fuzz melting loss to aggravate and finally to completely disappear when the power density exceeds 21 MW/m2. Irreversible grain expansion results in huge tensile stress, leading to the observable brittle cracking. The effects of transient thermal load and He ion energy play a crucial role in etching Mo fuzz during ELM transient events.
Two-body exceptional points in open dissipative systems
Authors: Ding Peize , Yi Wei
Published: October 2021

We study two-body non-Hermitian physics in the context of an open dissipative system depicted by the Lindblad master equation. Adopting a minimal lattice model of a handful of interacting fermions with single-particle dissipation, we show that the non-Hermitian effective Hamiltonian of the master equation gives rise to two-body scattering states with state- and interaction-dependent parity–time transition. The resulting two-body exceptional points can be extracted from the trace-preserving density-matrix dynamics of the same dissipative system with three atoms. Our results not only demonstrate the interplay of parity-time symmetry and interaction on the exact few-body level, but also serve as a minimal illustration on how key features of non-Hermitian few-body physics can be probed in an open dissipative many-body system.
Effect of the magnetization parameter on electron acceleration during relativistic magnetic reconnection in ultra-intense laser-produced plasma
Authors: Zhang Qian , Ping Yongli , An Weiming , Sun Wei , Zhong Jiayong
Published: October 2021

Relativistic magnetic reconnection (MR) driven by two ultra-intense lasers with different spot separation distances is simulated by a three-dimensional (3D) kinetic relativistic particle-in-cell (PIC) code. We find that changing the separation distance between two laser spots can lead to different magnetization parameters of the laser plasma environment. As the separation distance becomes larger, the magnetization parameter σ becomes smaller. The electrons are accelerated in these MR processes and their energy spectra can be fitted with double power-law spectra whose index will increase with increasing separation distance. Moreover, the collisionless shocks’ contribution to energetic electrons is close to the magnetic reconnection contribution with σ decreasing, which results in a steeper electron energy spectrum. Basing on the 3D outflow momentum configuration, the energetic electron spectra are recounted and their spectrum index is close to 1 in these three cases because the magnetization parameter σ is very high in the 3D outflow area.
Enhancement of magnetic and dielectric properties of low temperature sintered NiCuZn ferrite by Bi2O3–CuO additives
Authors: Li Jie , Lu Bing , Zhang Ying , Wu Jian , Yang Yan , Han Xue-Ning , Wen Dan-Dan , Liang Zheng , Zhang Huai-Wu
Published: October 2021

With a series of 1.0 wt%Bi2O3–x wt% CuO (x = 0.0, 0.2, 0.4, 0.6, and 0.8) serving as sintering additives, Ni0.23Cu0.32Zn0.45Fe2O4 ferrites are successfully synthesized at a low temperature (900 °C) by using the solid state reaction method. The effects of the additives on the phase formation, magnetic and dielectric properties as well as the structural and gyromagnetic properties are investigated. The x-ray diffraction (XRD) results indicate that the added Bi2O3–CuO can lower the synthesis temperature significantly without the appearing of the second phase. The scanning electron microscope (SEM) images confirm that Bi2O3 is an important factor that determines the sintering behaviors, while CuO affects the grain size and densification. With CuO content x = 0.4 or 0.6, the sample shows high saturation magnetization, low coercivity, high real part of magnetic permeability, dielectric permittivity, and small ferromagnetic resonance linewidth (ΔH). The NiCuZn ferrites are a promising new generation of high-performance microwave devices, such as phase shifters and isolators.
In situ measurement on nonuniform velocity distribution in external detonation exhaust flow by analysis of spectrum features using TDLAS
Authors: Huang Xiao-Long , Li Ning , Weng Chun-Sheng , Kang Yang
Published: October 2021

Instantaneous and precise velocity sensing is a critical part of research on detonation mechanism and flow evolution. This paper presents a novel multi-projection tunable diode laser absorption spectroscopy solution, to provide a real-time and reliable measurement of velocity distribution in detonation exhaust flow with obvious nonuniformity. Relations are established between overlapped spectrums along probing beams and Gauss velocity distribution phantom according to the frequency shifts and tiny variations in components of light-of-sight absorbance profiles at low frequencies analyzed by the fast Fourier transform. With simulated optical measurement using H2O feature at 7185.6 cm−1 carried out on a phantom generated using a simulation of two-phase detonation by a two-fluid model, this method demonstrates a satisfying performance on recovery of velocity distribution profiles in supersonic flow even with a noise equivalent absorbance up to 2 × 10−3. This method is applied to the analysis of rapidly decreasing velocity during a complete working cycle in the external flow field of an air-gasoline detonation tube operating at 25 Hz, and results show the velocity in the core flow field would be much larger than the arithmetic average from traditional tunable diode laser doppler velocimetry. This proposed velocity distribution sensor would reconstruct nonuniform velocity distribution of high-speed flow in low cost and simple operations, which broadens the possibility for applications in research on the formation and propagation of external flow filed of detonation tube.
Estimation of co-channel interference between cities caused by ducting and turbulence
Authors: Yang Kai , Wu Zhensen , Guo Xing , Wu Jiaji , Cao Yunhua , Qu Tan , Xue Jiyu
Published: October 2021

With the rapid development of the fifth-generation (5G) mobile communication technology, the application of each frequency band has reached the extreme, causing mutual interference between different modules. Hence, there is a requirement for detecting filtering and preventing interference. In the troposphere, over-the-horizon propagation occurs in atmospheric ducts and turbulent media. The effects of both ducting and turbulence can increase the probability of occurrence of long-distance co-channel interference (CCI), in turn, severely affecting the key performance indicators such as system access, handover and drop. In the 5G era, to ensure communication channels and information security, CCI must be reduced. This paper introduces a scattering parabolic equation algorithm for calculating signal propagation in atmospheric ducts on irregular terrain boundaries. It combines Hitney’s radio physical optical model and Wagner’s nonuniform turbulent scattering model for calculating the tropospheric scattering in an evaporation duct or a surface-based duct. The new model proposes a tropospheric scattering parabolic equation algorithm for various tropospheric duct environments. Finally, as a specific case, the topographical boundaries between several cities in the East China Plain were considered, and the over-the-horizon propagation loss was simulated for various ducting and turbulent environments. The simulation results were used to evaluate whether CCI would occur between cities in a specific environment.
Decoding of cortex-wide brain activity from local recordings of neural potentials
Authors: Liu Xin , Ren Chi , Huang Zhisheng , Wilson Madison , Kim Jeong-Hoon , Lu Yichen , Ramezani Mehrdad , Komiyama Takaki , Kuzum Duygu
Published: October 2021

Objective. Electrical recordings of neural activity from brain surface have been widely employed in basic neuroscience research and clinical practice for investigations of neural circuit functions, brain–computer interfaces, and treatments for neurological disorders. Traditionally, these surface potentials have been believed to mainly reflect local neural activity. It is not known how informative the locally recorded surface potentials are for the neural activities across multiple cortical regions. Approach. To investigate that, we perform simultaneous local electrical recording and wide-field calcium imaging in awake head-fixed mice. Using a recurrent neural network model, we try to decode the calcium fluorescence activity of multiple cortical regions from local electrical recordings. Main results. The mean activity of different cortical regions could be decoded from locally recorded surface potentials. Also, each frequency band of surface potentials differentially encodes activities from multiple cortical regions so that including all the frequency bands in the decoding model gives the highest decoding performance. Despite the close spacing between recording channels, surface potentials from different channels provide complementary information about the large-scale cortical activity and the decoding performance continues to improve as more channels are included. Finally, we demonstrate the successful decoding of whole dorsal cortex activity at pixel-level using locally recorded surface potentials. Significance. These results show that the locally recorded surface potentials indeed contain rich information of the large-scale neural activities, which could be further demixed to recover the neural activity across individual cortical regions. In the future, our cross-modality inference approach could be adapted to virtually reconstruct cortex-wide brain activity, greatly expanding the spatial reach of surface electrical recordings without increasing invasiveness. Furthermore, it could be used to facilitate imaging neural activity across the whole cortex in freely moving animals, without requirement of head-fixed microscopy configurations.
Directed stimulation with interfascicular interfaces for peripheral nerve stimulation
Authors: Koppaka Smruta , Hess-Dunning Allison , Tyler Dustin J
Published: October 2021

Objective. Computational models have shown that directional electrical contacts placed within the epineurium, between the fascicles, and not penetrating the perineurium, can achieve selectivity levels similar to point source contacts placed within the fascicle. The objective of this study is to test, in a murine model, the hypothesis that directed interfascicular contacts are selective. Approach. Multiple interfascicular electrodes with directional contacts, exposed on a single face, were implanted in the sciatic nerves of 32 rabbits. Fine-wire intramuscular wire electrodes were implanted to measure electromyographic (EMG) activity from medial and lateral gastrocnemius, soleus, and tibialis anterior muscles. Main results. The recruitment data demonstrated that directed interfascicular interfaces, which do not penetrate the perineurium, selectively activate different axon populations. Significance. Interfascicular interfaces that are inside the nerve, but do not penetrate the perineurium are an alternative to intrafascicular interfaces and may offer additional selectivity compared to extraneural approaches.
The role of tungsten chemical state and boron on ammonia formation using N2–H2 radiofrequency discharges
Authors: Antunes R. , Marot L. , Romero-Muñiz C. , Steiner R. , Meyer E.
Published: October 2021

This work aims at investigating the role of tungsten and boron surfaces on ammonia production with N2–H2 radiofrequency plasmas at 3 Pa. The experiments combine the analysis of the reaction products and surface chemical environment using mass spectrometry and x-ray photoelectron spectroscopy (XPS). We show that NH3 is formed upon discharges of N2 or H2 after having exposed a tungsten (W) foil to H2 or N2, respectively. A higher amount of ammonia is formed for the N2-then-H2 case, which we explain by the larger number of Eley–Rideal reaction channels for the formation of NH
x
(s) and the lower surface diffusion barrier for adsorbed hydrogen, calculated using the density functional theory (DFT). As a result, H(s) combines with N(s) or NH
x
(s) through Langmuir–Hinshelwood at a faster rate than N(s) combines with another N(s). The amount of NH3 formed with N2–H2 discharges after conditioning the tungsten foil with H2, N2 or O2 was also investigated. We observed that this pre-conditioning plays no major role on the amount of NH3 detected with the residual gas analyser, albeit a small decrease was observed after H2 contamination. With DFT, the adsorption energies of H on WO3 and W are found to be similar, while the adsorption of N on WO3 is significantly weaker. The similar NH3 concentrations obtained with a clean and oxidized tungsten surface thus suggest that the adsorption of N does not limit the formation rate of ammonia. The production of NH3 on boron was evaluated as well. The boron surface reduced the amount of detected ammonia almost by half. On the one side, a significant amount of H2 was removed from the surface during the Ar cleaning that followed, which suggests a strong retention of hydrogen. On the other side, the XPS data reveals that nitrogen forms strong bonds with boron and impurities on the surface, regardless on whether hydrogen is previously present on the surface or in the plasma volume. The presence of hydrogen in the plasma volume, simultaneously with nitrogen or after nitrogen exposure, is nevertheless necessary for the formation of NH(s) and NH2(s). No NH3(s) was however detected with XPS. The increased retention of both hydrogen and nitrogen on the boron surface may thus hinder the formation of NH3.
Evaluation of tribological, oxidation and corrosion behavior of HVOF sprayed sustainable temperature-dependent carbon coating
Authors: Tyagi Ankit , Chourasia Shubhangi , Murtaza Qasim , Walia R S
Published: October 2021

To abate frictional loss, advanced coatings are vital for piston rings, thick low friction environment-friendly carbon coatings have been deposited using HVOF spray (High Velocity Oxy-fuel) technique. The COF (Coefficient of Friction) was found in the range of 0.3 to 0.45 whereas the wearing range was about 45–150 μm during the tested conditions. After wear test at high temperature, the developed coating shows that micro-hardness was increased about 11.5%, 90% reduction in residual stress, COF decreases to about 50%, and wear decreases to about 70% under test conditions. The experimental result of the conducted corrosion test illustrates that the overall measured mass loss per unit area of the as deposited sample was decreased to be about 85.7% at an exposure time of 1 h, 63.6%, at an exposure time of 3 h, and 55% at an exposure time of 5 h.
Plasma activated water prepared by different plasma sources: physicochemical properties and decontamination effect on lentils sprouts
Authors: MEDVECKÁ Veronika , OMASTA Samuel , KLAS Matej , MOŠOVSKÁ Silvia , KYZEK Stanislav , ZAHORANOVÁ Anna
Published: October 2021

The pulsed corona discharge (CD) generated in contact with water and directly in water, and high-power air plasma jet (APJ) were studied for production of plasma activated water (PAW). The changes of physical (pH, redox potential, conductivity, temperature) and chemical (peroxides, nitrites, nitrates concentrations) properties of treated water were investigated. The comparison of CD generated in gas/water interface and underwater configuration in the same system showed that the interaction of reactive oxygen and nitrogen species formed in ambient air in gas/water system induces different chemical processes, leading to lower pH, higher oxidation-reduction potential (ORP) and higher conductivity of PAW than in underwater discharge. High yield of peroxide was observed in both configurations. The PAW prepared by APJ exhibits high concentration of nitrites and nitrates according to supplied energy, and related significant decrease of pH and increase of ORP and conductivity after treatment. The antimicrobial effect of PAW prepared by CD and plasma jet on lentils sprouts was studied in different treatment and washing times. The APJ appears to have great efficacy on water activation resulted in strong decontamination effect. The PAW treated by APJ for 10 min led to bacterial reduction from initial 8.3 to 5.9 and 4.0 log10 CFU g−1 after 10 and 30 min of washing, respectively.
Convergence acceleration of ensemble Kalman inversion in nonlinear settings
Authors: Chada Neil , Tong Xin
Published: October 2021

Many data-science problems can be formulated as an inverse problem, where the parameters are estimated by minimizing a proper loss function. When complicated black-box models are involved, derivative-free optimization tools are often needed. The ensemble Kalman filter (EnKF) is a particle-based derivative-free Bayesian algorithm originally designed for data assimilation. Recently, it has been applied to inverse problems for computational efficiency. The resulting algorithm, known as ensemble Kalman inversion (EKI), involves running an ensemble of particles with EnKF update rules so they can converge to a minimizer. In this article, we investigate EKI convergence in general nonlinear settings. To improve convergence speed and stability, we consider applying EKI with non-constant step-sizes and covariance inflation. We prove that EKI can hit critical points with finite steps in non-convex settings. We further prove that EKI converges to the global minimizer polynomially fast if the loss function is strongly convex. We verify the analysis presented with numerical experiments on two inverse problems.
Maximal operators and Fourier restriction on the moment curve
Authors: Jesurum Michael
Published: October 2021

We bound certain

r
r

-maximal restriction operators on the moment curve.