bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatially and temporally resolved evaluation of local thermodynamic equilibrium for laser-induced plasma in a high vacuum
Authors: Liu Zelin , Zhao Guomin , Guo Chuan , Chen Lei , Chen Minsun , Liu Hao , Han Kai
Published: September 2021

This figure evaluates the spatial and temporal dependence of LTE deviation. (v = 1, satisfies LTE; v > 1, departure from LTE.)
Planar hydrodynamic traps and buried channels for bead and cell trapping and releasing
Authors: Lipp Clémentine , Uning Kevin , Cottet Jonathan , Migliozzi Daniel , Bertsch Arnaud , Renaud Philippe
Published: September 2021

A new process for the fabrication of two superposed layers of microfluidic channels connected by vias is used to trap and release particles in a transparent chip. Parallel manipulation of beads is studied and the rules for cell trapping are defined.
Synthesis, structural characterization and cytotoxicity of a new proton transfer compound based on 2,4-diamino-1,3,5-triazine: an experimental and computational study
Authors: Gholivand Khodayar , Babaee Leila Sarmadi , Fallah Nasrin , Faraghi Mohammad , Dusek Michal , Eigner Vaclav
Published: September 2021

A water-soluble proton transfer compound was synthesized and characterized. Non-covalent interactions were studied by X-ray crystallography and DFT calculations. Anticancer activities were investigated and supported by a molecular docking study.
Quantum binding energy features of the drug olmesartan bound to angiotensin type-1 receptors in the therapeutics of stroke
Authors: Esmaile Stephany Campanelli , Bezerra Katyanna Sales , de Oliveira Campos Daniel Melo , da Silva Maria Karolaynne , Neto José Xavier Lima , Manzoni Vinicius , Fulco Umberto Laino , Oliveira Jonas Ivan Nobre
Published: September 2021

We investigated the binding energies of 105 residues within a 10 Å pocket radius, predicted the energetic relevance of olmesartan regions, and the influence of individual protein segments on OLM -AT1 binding.
Correction: Reduced graphene oxide in perovskite solar cells: the influence on film formation, photophysics, performance, and stability
Authors: Marchezi Paulo Ernesto , de Araújo Francineide Lopes , Szostak Rodrigo , Germino José Carlos , Therézio Eralci M. , Marletta Alexandre , Nogueira Ana Flavia
Published: September 2021

Correction for ‘Reduced graphene oxide in perovskite solar cells: the influence on film formation, photophysics, performance, and stability’ by Paulo Ernesto Marchezi et al., J. Mater. Chem. C, 2021, DOI: 10.1039/D1TC01360B.
Current tuned slotted Y‐branch laser for wafer thickness measurements with THz radiation
Authors: Surkamp N. , Gerling A. , O'Gorman J. , Honsberg M. , Schmidtmann S. , Nandi U. , Preu S. , Sacher J. , Brenner C. , Hofmann M. R.
Published: September 2021

A slotted Y‐branch laser diode that emits two spectral modes at a difference frequency of about 1 THz is investigated in the context of photonic based cw‐THz measurements. The beating frequency of the emitted laser light can be tuned by ±10.5 GHz around 1 THz by changing the applied laser current, which allows for potentially fast measurements. A second spectral window of ±6.5 GHz was found at 850 GHz. Pointwise scanning of the difference frequency is demonstrated with thickness determination of HRFZ‐Si wafer samples as a possible application scenario.
Power quality investigation of CHB nine‐level converter based large‐scale solar PV system with different modulation schemes
Authors: Kulkarni Jyoti , Yadav Shivam Kumar , Singh Bhim , Kumar Narendra
Published: September 2021

Multilevel converters (MLCs) are extensively used in solar photovoltaic (SPV) applications owing to their advantages such as low total harmonic distortion (THD) in the converter voltage, reduction in device stress, and switching losses. A suitable modulation technique is important for the efficient closed‐loop control of megawatt (MW)‐scale solar photovoltaic plants. This work utilises different modulation techniques, such as phase‐shifted (PS) multicarrier pulse width modulation (PWM), selected harmonic elimination (SHE), and nearest level modulation (NLM), for switching of cascaded H‐bridge (CHB) converter‐based large‐scale SPV systems. The investigation on improving power quality is presented with a suitable fast Fourier transform (FFT) analysis and comparative graphs. The presented control and modulation enhance the power quality of the output current being fed to the grid in the dynamic solar profile. Moreover, the low switching frequency employed in this photovoltaic converter at a high power rating increases the system efficiency. Graphical illustrations of losses with fundamental and PWM switching were analysed for the MW‐rated system. The obtained results show that SHE‐PWM provides the best performance for large‐scale solar power plants. Furthermore, the IEEE‐519 standard was met for both grid voltages and currents. The system was modelled and simulated in MATLAB/Simulink and validated in a real‐time environment.
A two‐stage model predictive control with zero‐sequence voltage injection for a three‐level T‐type inverter
Authors: Xin Yechun , Wang Yanxu , Wu Gang , Jiang Shouqi , Wang Weiru , Wang Chaobin , Wang Wei
Published: September 2021

Three‐level inverter systems based on the conventional Finite Control Set‐Model Predictive Control (FCS‐MPC) principle are characterized by large current ripples, difficult‐to‐design weighting factors and variable switching frequencies. In order to solve these problems, in this study a two‐stage model predictive control is proposed that consists of two objective functions: the current prediction and neutral point potential prediction objective functions. The first objective function was based on the mathematical model of a three‐level T‐type, and the second was based on the zero‐sequence injection principle and intended to modify the modulated signals. Then, a multi‐carrier modulation method was adopted to attain the switching signal for the inverter system. In addition, this paper analyses the sensitivity of the inductance and load resistance parameters for the predictive model. Finally, the performance of the proposed strategy is evaluated based on the time‐domain simulation and experiment study.
Followed The Regularized Leader (FTRL) prediction model based photovoltaic array reconfiguration for mitigation of mismatch losses in partial shading condition
Authors: Gao Xin , Deng Fang , Zheng Hao , Ding Ning , Ye Ziman , Cai Yeyun , Wang Xiangyang
Published: September 2021

Non‐uniform irradiance, for example, partial shading, would affect the performance of the whole Photovoltaic (PV) array and reduce the output power. Since the layout of PV array is also an important factor influencing the performance of PV array, reconfiguration scheme has been researched popularly. Since plenty of array reconfiguration techniques are not realistic to be implemented in reality, in this paper considering the simplicity, robustness and economical aspects, a Followed The Regularized Leader algorithm (FTRL) regression prediction model based switches controlled PV array reconfiguration method is proposed to enhance the power output from solar PV array and alleviate the effects of partial shadings. The proposed scheme has no additional labor and wire requirement, since the proposed connection architecture of PV array involves no complex switch matrix design. Subsequently, to testify the performance of the proposed scheme, simulations with various shades in different PV arrays are made and evaluation parameters, for example, Fill Factor (FF) and mismatch loss are calculated. Furthermore, outdoor experiments are conducted to validate the simulation and the analyses. Besides, extensive analyses of cost analysis and energy savings are given. At last, a comprehensive evaluation is performed to check the quality of the proposed scheme by comparing with various techniques in literature.
Comprehensive aging assessment of pitch systems combining SCADA and failure data
Authors: Wei Lu , Qian Zheng , Zareipour Hamidreza , Zhang Fanghong
Published: September 2021

Due to the recent rapid development of the wind energy industry, many wind turbines that have been operational over long periods will face degradation caused by aging effects; hence, an appropriate aging assessment method for wind turbines and their components is essential for optimizing the asset management and maintenance strategy of a wind farm. An aging assessment method is proposed for wind‐turbine electric‐pitch systems by introducing four individual aging indicators based on the examination of supervisory control and data acquisition (SCADA) and failure data, i.e. function, energy‐consumption, temperature, and reliability indicators. To obtain a reliable comprehensive assessment, an information‐fusion method has been developed based on a given reference value; the weighting factors in the information fusion were calculated based on the reference value, while reliability and robustness were verified using the SCADA and failure data from a wind farm over three years.
Analysis of the Caribbean wave climate for wave energy harvesting
Authors: Lemessy Kevin G. , Manohar Krishpersad , Adeyanju Anthony
Published: September 2021

In this study, the design requirements for a regional wave energy converter are identified from the analysis of 10 years of spectral data provided by nine buoys located across the Caribbean. It indicated that the average significant wave height and wave period in the Caribbean is 1.62 m and 5.91 s, respectively, while the average total theoretical power capable of being absorbed from a wave energy converter is 7.4 kilowatts per meter of surface waves. Devices should be designed to withstand a significant wave height of 19.0 ± 2.8 meters (95% confidence) for a 1 in 100 year return wave. This was determined by performing various extreme wave analyses. Additionally, a design life of 30 years for a device would have a probability of exceedance regarding this return wave as 26%. Using two‐dimensional wave spectra analysis for the resource study, the overall spectral width, directionality coefficient and direction of the maximum directionally resolved wave power for the region are determined to be 0.172, 0.74 and 42°, respectively. It is expected that the combination of these information would improve the viability of a wave energy industry in the Caribbean and advance technological development.
Hint of a truncated primordial spectrum from the CMB large-scale anomalies
Authors: Melia Fulvio , Ma Qingbo , Wei Jun-Jie , Yu Bo
Published: September 2021

Context. Several satellite missions have uncovered a series of potential anomalies in the fluctuation spectrum of the cosmic microwave background temperature, including: (1) an unexpectedly low level of correlation at large angles, manifested via the angular correlation function, C(θ); and (2) missing power in the low multipole moments of the angular power spectrum, Cℓ.

Aims. Their origin is still debated, however, due to a persistent lack of clarity concerning the seeding of quantum fluctuations in the early Universe. A likely explanation for the first of these appears to be a cutoff, kmin = (3.14 ± 0.36)×10−4 Mpc−1, in the primordial power spectrum, 𝒫(k). Our goal in this paper is twofold: (1) we examine whether the same kmin can also self-consistently explain the missing power at large angles, and (2) we confirm that the introduction of this cutoff in 𝒫(k) does not adversely affect the remarkable consistency between the prediction of Planck-ΛCDM and the Planck measurements at ℓ > 30.

Methods. We have used the publicly available code CAMB to calculate the angular power spectrum, based on a line-of-sight approach. The code was modified slightly to include the additional parameter (i.e., kmin) characterizing the primordial power spectrum. In addition to this cutoff, the code optimized all of the usual standard-model parameters.

Results. In fitting the angular power spectrum, we found an optimized cutoff, kmin = (2.04−0.79+1.4) × 10−4 Mpc−1, when using the whole range of ℓ’s, and kmin = (3.3−1.3+1.7) × 10−4 Mpc−1, when fitting only the range ℓ ≤ 30, where the Sachs-Wolfe effect is dominant.

Conclusions. These are fully consistent with the value inferred from C(θ), suggesting that both of these large-angle anomalies may be due to the same truncation in 𝒫(k).
The dust–star interplay in late-type galaxies at z < 0.5: Forecasts for the JWST
Authors: Pappalardo Ciro , Bendo George J. , Boquien Mederic , Baes Maarten , Viaene Sebastien , Bianchi Simone , Fritz Jacopo
Published: September 2021

Context. In recent years, significant growth in the amount of data available to astronomers has opened up the possibility for extensive multi-wavelength approaches. In the field of galaxy evolution, such approaches have uncovered fundamental correlations, linking the dust component of a galaxy to its star formation rate (SFR). Despite these achievements, the relation between the SFR and the dust is still challenging, with uncertainties related to the physical mechanisms linking the two.

Aims. In this paper, we re-examine these correlations, paying specific attention to the intrinsic properties of the dust. Our goal is to investigate the origin of the observed scatter in low-redshift galaxies, and the ability of the James Webb Space Telescope (JWST) to explore such relations in the early Universe.

Methods. We defined a sample of about 800 normal star-forming galaxies with photometries in the range of 0.15 < λ < 500 μm and analysed them with different spectral energy distribution (SED) fitting methods. With the SEDs extracted, we investigated the detection rate at different redshifts with the MId-Infrared instruments (MIRI) on board the JWST.

Results. Dust luminosity (Ld) and SFR show a strong correlation, but for SFR < 2 M⊙ yr−1, the correlation scatter increases dramatically. We show that selection based on the fraction of ultraviolet (UV) emission absorbed by dust, that is, the UV extinction, greatly reduces the data dispersion. Dust masses (Md) and SFR show a weaker correlation, with a larger scatter due to the interstellar radiation field produced by stars during late evolutionary stages, which shifts the positions of the galaxies in the dust mass–SFR plane. At z = 2, more than 60% of the galaxies in the sample are detected with F770, F1000, F1280, F1500, and F1800. At higher redshifts, the detection decreases, and only 45% of z = 8 galaxies are detected with two filters. Reproducing the expected sensitivity of the Cosmic Evolution Early Release Science Survey and classifying galaxies according to their SFR and stellar mass (M*), we investigated the MIRI detection rate as a function of the physical properties of the galaxies. Fifty percent of the objects with SFR ∼ 1 M⊙ yr−1 at z = 6 are detected with F770, which decreases to 20% at z = 8. For such galaxies, only 5% of the subsample will be detected at 5σ with F770 and F1000 at z = 8, and only 10% with F770, F1000, and F1280 at z = 6. For galaxies with higher SFR, detection with these three filters will be possible up to z = 6 in ∼60% of the subsample.

Conclusions. The link between dust and star formation is complex, and many aspects remain to be fully understood. The scatter between SFR and dust mass, and SFR and luminosity, decreases significantly when the analysis includes dust properties. In this context, the JWST will revolutionise the field, allowing investigation of the dust–star interplay well within the epoch of reionisation.
Medicinal Plants: Guests and Hosts in the Heterologous Expression of High-Value Products
Authors: Vasilev Nikolay
Published: September 2021

Medicinal plants play an important dual role in the context of the heterologous expression of high-value pharmaceutical products. On the one hand, the classical biochemical and modern omics approaches allowed for the discovery of various genes encoding biosynthetic pathways in medicinal plants. Recombinant DNA technology enabled introducing these genes and regulatory elements into host organisms and enhancing the heterologous production of the corresponding secondary metabolites. On the other hand, the transient expression of foreign DNA in plants facilitated the production of numerous proteins of pharmaceutical importance. This review summarizes several success stories of the engineering of plant metabolic pathways in heterologous hosts. Likewise, a few examples of recombinant protein expression in plants for therapeutic purposes are also highlighted. Therefore, the importance of medicinal plants has grown immensely as sources for valuable products of low and high
molecular weight. The next step ahead for bioengineering is to achieve more success stories of industrial-scale production of secondary plant metabolites in microbial systems and to fully exploit plant cell factoriesʼ commercial potential for recombinant proteins.
Effect of Gut Microbiota on the Metabolism of Chemical Constituents of Berberis kansuensis Extract Based on UHPLC-Orbitrap-MS Technique
Authors: Du Huan , Xu Tong , Yi Huan , Xu Xinmei , Zhao Chengcheng , Ge Yiman , Zhang Chuantao , Fan Gang
Published: September 2021

The dried stem bark of Berberis kansuensis is a commonly used Tibetan herbal medicine for the treatment of diabetes. Its main chemical components are alkaloids, such as berberine, magnoflorine and jatrorrhizine. However, the role of gut microbiota in the in vivo metabolism of these chemical components has not been fully elucidated. In this study, an ultra-high performance liquid chromatography method coupled with Orbitrap mass spectrometry (UHPLC-Orbitrap-MS) technology was applied to detect and identify prototype components and metabolites in rat intestinal contents and serum samples after oral administration of a B. kansuensis extract. A total of 16 prototype components and 40 metabolites were identified. The primary metabolic pathways of the chemical components from B. kansuensis extract were demethylation, desaturation, deglycosylation, reduction, hydroxylation, and other conjugation reactions including sulfation, glucuronidation,
glycosidation, and methylation. By comparing the differences of metabolites between diabetic and pseudo-germ-free diabetic rats, we found that the metabolic transformation of some chemical components in B. kansuensis extract such as bufotenin, ferulic acid 4-O-β-D-glucopyranoside, magnoflorine, and 8-oxyberberine, was affected by the gut microbiota. The results revealed that the gut microbiota can affect the metabolic transformation of chemical constituents in B. kansuensis extract. These findings can enhance our understanding of the active ingredients of B. kansuensis extract and the key role of the gut microbiota on them.
Thoracic Paravertebral Block Ameliorates Postoperative Delirium in Geriatric Patients
Authors: Heng Lei , Wang Mingyu , Wang Mingquan , Li Li , Zhu Shanshan
Published: September 2021

Objectives Thoracic surgery often causes postoperative delirium (POD) in geriatric patients. This study aimed to explore the effect of ultrasound-guided continuous thoracic paravertebral block (UG-TPVB) on POD in geriatric patients undergoing pulmonary resection.

Methods Total 128 patients who underwent pulmonary resection were randomly allocated to either the conventional patient-controlled analgesia (PCA) group or the UG-TPVB group (n = 64 per group). The consumption of opioid agents (propofol and remifentanil), postoperative hospital stay, postoperative pulmonary atelectasis, postoperative nausea/vomiting, and postoperative itchiness were recorded. The diagnosis of delirium was dependent on the Nursing Delirium Screening Scale. The postoperative pain was assessed by visual analogue scale (VAS) score. The serum levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α were used to evaluate the postoperative neuroinflammation.

Results The consumption of propofol and remifentanil, postoperative hospital stay, postoperative pulmonary atelectasis, postoperative nausea/vomiting, and postoperative itchiness in the UG-TPVB group were lower than that in the PCA group. Compared with the PCA group, the prevalence of POD was decreased in the UG-TPVB group. In addition, use of UG-TPVB not only reduced postoperative pain (VAS score) but also decreased postoperative neuroinflammation compared with PCA in geriatric patients undergoing pulmonary resection.

Conclusions This study determined the benefits of UG-TPVB over PCA, providing an effectiveness approach to alleviate POD in geriatric patients undergoing pulmonary resection.
Generalized Null Lagrangians for Equations with Special Function Solutions
Authors: Dange Atharva A. , Vestal Lesley C. , Musielak Zdzislaw E.
Published: September 2021

A method to derive general standard and null Lagrangians for second-order differential equations whose solutions are special function of mathematical physics is presented. The general null Lagrangians are used to find the corresponding general gauge functions. All derived Lagrangians are new and in special cases they reduce to those published in the literature. The obtained results are applied to the Bessel, Hermite and Legendre equations, which have many applications in physics, applied mathematics and engineering.
Installation of a Cosmic-Ray Trigger System to Commission the Belle II Experiment VerteX Detector with Cosmic Rays
Authors: Halawani Ahmed , Ayad Rachid , Albalawi Mohammed , Alatawi Mansour , Alatawi Abdulaziz , Moser Hans-Günter
Published: September 2021

In this paper, we describe the design, construction, testing, and installation of the cosmic ray trigger system used to commission the VerteX Detector (VXD) of the Belle II experiment at the High-Energy Accelerator Research Organization (KEK) in Japan. The system consists of two rows of scintillators; with six scintillators being on top of the VXD, and six at the bottom of it. The scintillators were characterized (plateaus, threshold values, coincidences rate), and when compared with the simulation values a concordant match was found for all cosmic coincidence measurements. In Phase 3 of SuperKEKB accelerator, the VXD was the last sub-detector to be integrated into the heart of Belle II detector, after it was absent from being integrated within Belle II in Phase 1 and Phase 2 of SuperKEKB machine studies. A system consisting of VXD prototype parts had been installed, into Belle II detectors, at the VXD location during Phase 2 to study background and it was found that the VXD can cope with the level of measured background: allowing the VXD to be present during Phase 3 Belle II data taking. The VXD was tested with cosmic rays outside of Belle II before it was integrated within Belle II just before Phase 3 data taking, which commenced in March 2019.
Nitrogen Beams with a National Electrostatics Corporation Alphatross Source and a 5SDH Accelerator
Authors: Harlow B. , DeYoung P. A. , Bunnell V. A.
Published: September 2021

Over the past 15 years, Hope College has been producing hydrogen and helium ion beams with an Alphatross® ion source and 5SDH Pelletron® tandem Van de Graaff accelerator. The manufacturer stated the possibility of creating nitrogen ions from this source, but Hope College has not, up until now, attempted to do so. By mixing approximately 1% nitrogen into hydrogen source gas, imidogen (NH-) and amidogen (NH2-) ions are created and accelerated through the tandem accelerator. Oxygen and hydroxide beams are also present due to residual water vapor in the source after maintenance. Post acceleration, these ion beams were directed into a scattering chamber by a dipole bending magnet for identification. Alternate beams such as these open up new possibilities for future experiments such as nitrogen implantation.
Normal modes with boundary dynamics in geophysical fluids
Authors: Yassin Houssam
Published: September 2021

Three-dimensional geophysical fluids support both internal and boundary-trapped waves. To obtain the normal modes in such fluids, we must solve a differential eigenvalue problem for the vertical structure (for simplicity, we only consider horizontally periodic domains). If the boundaries are dynamically inert (e.g., rigid boundaries in the Boussinesq internal wave problem and flat boundaries in the quasigeostrophic Rossby wave problem), the resulting eigenvalue problem typically has a Sturm–Liouville form and the properties of such problems are well-known. However, when restoring forces are also present at the boundaries, then the equations of motion contain a time-derivative in the boundary conditions, and this leads to an eigenvalue problem where the eigenvalue correspondingly appears in the boundary conditions. In certain cases, the eigenvalue problem can be formulated as an eigenvalue problem in the Hilbert space L2⊕C and this theory is well-developed. Less explored is the case when the eigenvalue problem takes place in a Pontryagin space, as in the Rossby wave problem over sloping topography. This article develops the theory of such problems and explores the properties of wave problems with dynamically active boundaries. The theory allows us to solve the initial value problem for quasigeostrophic Rossby waves in a region with sloping bottom (we also apply the theory to two Boussinesq problems with a free-surface). For a step-function perturbation at a dynamically active boundary, we find that the resulting time-evolution consists of waves present in proportion to their projection onto the dynamically active boundary.
Fractional blood flow in rotating nanofluid with different shapes nanoparticles in the influence of activation energy and thermal radiation
Authors: Ndjawa Yomi P. A. , Bansi Kamdem C. D. , Nkoa Nkomom T. , Tabi C. B. , Mohamadou A. , Kofane T. C.
Published: September 2021

A fractional blood flow model, in the presence of magnetic nanoparticles, is considered in this work. The effects of activation energy and thermal radiation on the blood flowing in the oscillating elastic tube are studied. The nanofluid inside the tube is activated by the rotating effect of the charged particles, a constant external magnetic field, and the activation energy. The blood is assumed to be at a temperature and a concentration that vary with the speed of the particles. The study takes advantage of a model, which includes a fractional-order derivative of Caputo’s type. The shape of nanoparticles and the speed of blood and the distributions of temperature and concentration are assimilated to Brownian motion and thermophoresis. They are calculated numerically using the L1-algorithm method. The results show that the applied magnetic field and the effects of the fractional-order parameter reduce the velocity of the nanofluid and nanoparticles, which considerably affects the temperature and concentration of the fluid. It is also found that the particle shape and fractional derivative parameters significantly influence velocities and heat transfer.
Field-aligned potential drops in nonthermal plasmas: Application to plasma sheet boundary layer
Authors: Shamir M. , Murtaza G.
Published: September 2021

Kinetic Alfvén waves are observed in the plasma sheet boundary layer (PSBL) as indicated by the Polar satellite. Moreover, the THEMIS and the Polar spacecraft also detected parallel electric fields associated with double layers (DLs) in the PSBL region. Apart from this, the Magnetospheric Multiscale Mission recently reported counterstreaming ion beams in the aforesaid region of the Earth's magnetosphere. Being motivated by these observations, we have investigated kinetic Alfvénic DLs (KADLs) in a two-component low-β Cairns distributed plasma in the plasma sheet boundary layer at altitude 4−6RE. In order to explore KADL structures, the Sagdeev potential technique is employed to construct a nonlinear extended Korteweg–de Vries equation. It is found that our investigation admits only rarefactive KADL structures. Furthermore, the effects of nonthermality and Alfvénic Mach number on KADLs and their corresponding parallel electric field are explored in detail. It is noted that the propagation characteristics of KADL and the electric field profiles are significantly affected by nonthermality. Moreover, the implications of our results to PSBL related to charged particle acceleration are briefly mentioned. The present theoretical results are consistent with the Polar spacecraft observations.
Autoresonance phenomenon in a long mirror
Authors: Andreev V. V. , Novitsky A. A. , Umnov A. M.
Published: September 2021

The paper describes an implementation of a long mirror-based variant of cyclotron autoresonance which permits a local temporary change in the mirror`s induction and provides a mode for filling the trap with primary plasma, and for the generation of plasma bunches with an energetic electron component and their accumulation within a single cavity. The approach does not require injection of external particles into the acceleration zone as particles can be generated directly within the mirror using specialized conditions of electron cyclotron resonance (ECR) as part of the operational mode. A detailed study of the spectral-angular distribution of Bremsstrahlung in various operational modes has been undertaken. The results of this study permit the optimal value of the time sequence between the leading edge of the pulsed magnetic field and the microwave pulse to be determined, which ensures the optimal mode of electron trapping in the cyclotron autoresonance mode. Bremsstrahlung radiation recorded in the transverse direction has a significantly higher intensity of photons and energy compared to the longitudinal direction during the acceleration and subsequent confinement mode of plasma bunches. The observed changes in the intensity and spectral distribution of the Bremsstrahlung, which depend on the values of the operating parameters for acceleration, afford the possibility to define the dependence of the number of initial plasma particles trapped by cyclotron autoresonance for the different operating modes. The results will improve our understanding of the processes taking place at various stages of the operational modes. In general, such studies are important for gaining an improved understanding of the mechanisms of generation and confinement of hot electron plasma bunches with an energetic electron component for autoresonant interaction in a long mirror.
Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma
Authors: von der Linden J. , Fiksel G. , Peebles J. , Edwards M. R. , Willingale L. , Link A. , Mastrosimone D. , Chen Hui
Published: September 2021

Creating a magnetized relativistic pair plasma in the laboratory would enable the exploration of unique plasma physics relevant to some of the most energetic events in the universe. As a step toward a laboratory pair plasma, we have demonstrated an effective confinement of multi-MeV electrons inside a pulsed-power-driven 13 T magnetic mirror field with a mirror ratio of 2.6. The confinement is diagnosed by measuring the axial and radial losses with magnetic spectrometers. The loss spectra are consistent with ≤2.5 MeV electrons confined in the mirror for ∼1 ns. With a source of 1012 electron-positron pairs at comparable energies, this magnetic mirror would confine a relativistic pair plasma with Lorentz factor γ∼6 and magnetization σ∼40.
Time simulation of the nonlinear wave–particle interaction in meters-long traveling-wave tubes
Authors: Minenna Damien F. G. , Aliane Khalil , Elskens Yves , Poyé Alexandre , André Frédéric , Puech Jérôme , Doveil Fabrice
Published: September 2021

We propose a multi-particle self-consistent Hamiltonian (derived from an N-body description) that is applicable for periodic structures, such as traveling-wave tubes (TWTs), gyrotrons, free-electron lasers, or particle accelerators. We build a one-dimension symplectic multi-particle algorithm to simulate the nonlinear wave–particle interaction in the time domain occurring in an experimental 3-m-long helix TWT. Our algorithm is efficient thanks to a drastic reduction model. A 3D helix version of our reduction model is provided. Finally, we establish an explicit expression of the electromagnetic power in the time domain and in non-monochromatic (non-“continuous waveform”) regime.
Microscopic diffusion coefficients of dumbbell- and spherocylinder-shaped colloids and their application in simulations of crowded monolayers
Authors: Lüders Anton , Zander Ellen , Nielaba Peter
Published: September 2021

We explore the diffusion properties of colloidal particles with dumbbell and spherocylinder shapes using a hydrodynamic bead-shell approach and additional Brownian dynamics (BD) simulations. By applying the bead-shell method, we determine empirical formulas for the microscopic diffusion coefficients. A comparison of these formulas and established experimental and theoretical results shows remarkable agreement. For example, the maximum relative discrepancy found for dumbbells is less than 5%. As an application example of the empirical formulas, we perform two-dimensional (2D) BD simulations based on a single dumbbell or spherocylinder in a suspension of spheres and calculate the resulting effective long-time diffusion coefficients. The performed BD simulations can be compared to quasi-2D systems such as colloids confined at the interface of two fluids. We find that the effective diffusion coefficient of translation mostly depends on the sphere area fraction ϕ, while the effective diffusion coefficient of rotation is influenced by the aspect ratio and ϕ. Furthermore, the effective rotational diffusion constant seems to depend on the particle shape with the corresponding implementation of the interactions. In the resolution limit of our methods, the shape-dependent differences of the microscopic diffusion coefficients and the long-time diffusion constant of translation are negligible in the first approximation. The determined empirical formulas for the microscopic diffusion coefficients add to the knowledge of the diffusion of anisotropic particles, and they can be used in countless future studies.
The Kuramoto model on a sphere: Explaining its low-dimensional dynamics with group theory and hyperbolic geometry
Authors: Lipton Max , Mirollo Renato , Strogatz Steven H.
Published: September 2021

We study a system of N identical interacting particles moving on the unit sphere in d-dimensional space. The particles are self-propelled and coupled all to all, and their motion is heavily overdamped. For d=2, the system reduces to the classic Kuramoto model of coupled oscillators; for d=3, it has been proposed to describe the orientation dynamics of swarms of drones or other entities moving about in three-dimensional space. Here, we use group theory to explain the recent discovery that the model shows low-dimensional dynamics for all N≥3 and to clarify why it admits the analog of the Ott–Antonsen ansatz in the continuum limit N→∞. The underlying reason is that the system is intimately connected to the natural hyperbolic geometry on the unit ball Bd. In this geometry, the isometries form a Lie group consisting of higher-dimensional generalizations of the Möbius transformations used in complex analysis. Once these connections are realized, the reduced dynamics and the generalized Ott–Antonsen ansatz follow immediately. This framework also reveals the seamless connection between the finite and infinite-N cases. Finally, we show that special forms of coupling yield gradient dynamics with respect to the hyperbolic metric and use that fact to obtain global stability results about convergence to the synchronized state.
Efficacy of homemade face masks against human coughs: Insights on penetration, atomization, and aerosolization of cough droplets
Authors: Krishan Bal , Gupta Dipendra , Vadlamudi Gautham , Sharma Shubham , Chakravortty Dipshikha , Basu Saptarshi
Published: September 2021

Ever since the emergence of the ongoing COVID-19 pandemic, the usage of makeshift facemasks is generally advised by policymakers as a possible substitute for commercially available surgical or N95 face masks. Although such endorsements could be economical and easily accessible in various low per-capita countries, the experimental evidence on the effectiveness of such recommendations is still lacking. In this regard, we carried out a detailed experimental investigation to study the fate of a large-sized surrogate cough droplet impingement at different velocities (corresponding to mild to severe coughs) on various locally procured cloth fabrics. Observation shows that larger ejected droplets (droplets that would normally settle as fomites in general) during a coughing event have enough momentum to penetrate single-layer cloth masks; the penetrated volume atomize into smaller daughter droplets that fall within aerosol range, thereby increasing infection potential. Theoretically, two essential criteria based on the balances of viscous dissipation-kinetic energy and surface tension-kinetic energy effects have been suggested for the droplet penetration through mask layers. Furthermore, a new parameter called η (the number density of pores for a fabric) is developed to characterize the volume penetration potential and subsequent daughter droplet size. Finally, the effect of mask washing frequency is analyzed. The outcomes from the current study can be used as a guide in selecting cloth fabrics for stitching multi-layered.
Multi-mode lasing in terahertz metasurface quantum-cascade VECSELs
Authors: Wu Yu , Addamane Sadhvikas , Reno John L. , Williams Benjamin S.
Published: September 2021

To date, terahertz quantum-cascade vertical-external-cavity surface-emitting lasers (QC-VECSELs) have tended to oscillate in only one or two lasing modes at a time. This is due to the fact that the interaction between all of the longitudinal external cavity modes and the QC gain material is mediated through a single metasurface resonance, whose spatial overlap changes little with frequency; this suppresses spatial-hole-burning induced multi-mode operation. In this Letter, a VECSEL external cavity is demonstrated using an output coupler based upon a high-resistivity silicon etalon, which presents a periodic reflectance spectrum that is nearly matched with the external cavity mode spectrum. As the cavity length is varied, a systematic transition between a single/double-mode lasing regime and a multi-mode lasing regime is realized due to the Vernier effect. Up to nine modes lasing simultaneously with a free-spectral-range of approximately 21 GHz is demonstrated. This result provides a path toward the multi-mode operation necessary for eventual frequency comb operation.
Fluid dynamics of droplet generation from corneal tear film during non-contact tonometry in the context of pathogen transmission
Authors: Roy Durbar , M Sophia , Rasheed Abdur , Kabi Prasenjit , Roy Abhijit Sinha , Shetty Rohit , Basu Saptarshi
Published: September 2021

Noninvasive ocular diagnostics demonstrate a propensity for droplet generation and present a potential pathway of distribution for pathogens such as the severe acute respiratory syndrome coronavirus 2. High-speed images of the eye subjected to air puff tonometry (glaucoma detection) reveal three-dimensional, spatiotemporal interaction between the puff and tear film. The interaction finally leads to the rupture and breakup of the tear film culminating into sub-millimeter sized droplet projectiles traveling at speeds of 0.2 m/s. The calculated droplet spread radius (∼0.5 m) confirms the likelihood of the procedure to generate droplets that may disperse in air as well as splash on instruments, raising the potential of infection. We provide a detailed physical exposition of the entire procedure using high fidelity experiments and theoretical modeling. We conclude that air puff induced corneal deformation and subsequent capillary waves lead to flow instabilities (Rayleigh–Taylor, Rayleigh–Plateau) that lead to tear film ejection, expansion, stretching, and subsequent droplet formation.
Hitting time of rapid intensification onset in hurricane-like vortices
Authors: Fan Wai-Tong (Louis) , Kieu Chanh , Sakellariou Dimitrios , Patra Mahashweta
Published: September 2021

Predicting tropical cyclone (TC), rapid intensification (RI) is an important yet challenging task in current weather forecast due to our incomplete understanding of TC nonlinear processes. This study examines the variability of RI onset, including the probability of RI occurrence and the timing of RI onset, using a low-order stochastic model for TC development. Defining RI onset as the first hitting time for a given subset in the TC-scale state space, we quantify the probability of the occurrence of RI onset and the distribution of the timing of RI onset for a range of initial conditions and model parameters. Based on asymptotic analysis for stochastic differential equations, our results show that RI onset occurs later, along with a larger variance of RI onset timing, for weaker vortex initial condition and stronger noise amplitude. In the small noise limit, RI onset probability approaches one and the RI onset timing has less uncertainty (i.e., a smaller variance), consistent with observation of TC development under idealized environment. Our theoretical results are also verified against Monte Carlo simulations and compared with explicit results for a general one-dimensional system, thus providing new insights into the variability of RI onset and helping better quantify the uncertainties of RI variability for practical applications.
In-flight distribution of an electron within a surface acoustic wave
Authors: Edlbauer Hermann , Wang Junliang , Ota Shunsuke , Richard Aymeric , Jadot Baptiste , Mortemousque Pierre-André , Okazaki Yuma , Nakamura Shuji , Kodera Tetsuo , Kaneko Nobu-Hisa , Ludwig Arne , Wieck Andreas D. , Urdampilleta Matias , Meunier Tristan , Bäuerle Christopher , Takada Shintaro
Published: September 2021

Surface acoustic waves (SAWs) have large potential to realize quantum-optics-like experiments with single flying electrons employing their spin or charge degree of freedom. For such quantum applications, highly efficient trapping of the electron in a specific moving quantum dot (QD) of a SAW train plays a key role. Probabilistic transport over multiple moving minima would cause uncertainty in synchronization that is detrimental for coherence of entangled flying electrons and in-flight quantum operations. It is thus of central importance to identify the device parameters enabling electron transport within a single SAW minimum. A detailed experimental investigation of this aspect is so far missing. Here, we fill this gap by demonstrating time-of-flight measurements for a single electron that is transported via a SAW train between distant stationary QDs. Our measurements reveal the in-flight distribution of the electron within the moving acousto-electric quantum dots of the SAW train. Increasing the acousto-electric amplitude, we observe the threshold necessary to confine the flying electron at a specific, deliberately chosen SAW minimum. Investigating the effect of a barrier along the transport channel, we also benchmark the robustness of SAW-driven electron transport against stationary potential variations. Our results pave the way for highly controlled transport of electron qubits in a SAW-driven platform for quantum experiments.
Effect of gas generation by chemical reaction on viscous fingering in a Hele–Shaw cell
Authors: Wang Weicen , Zhang Chunwei , Patmonoaji Anindityo , Hu Yingxue , Matsushita Shintaro , Suekane Tetsuya , Nagatsu Yuichiro
Published: September 2021

Herein, the effect of gas-bubble generation by a chemical reaction on viscous fingering (VF) is investigated using a Hele–Shaw cell in a miscible two-phase liquid. Sodium bicarbonate (NaHCO3) and citric acid (C6H8O7) solutions were used as displacing and displaced fluids, respectively. As factors affecting the displacement pattern with gas bubbles, four characteristic times of displacement, chemical reaction, bubble nucleation, and bubble coalescence, as well as the viscosity ratio, were discussed. In the experiments conducted herein, the characteristic time of the chemical reaction was shorter than those of other characteristic factors. Bubble coalescence occurred quickly, and the coalescence time was almost the same as the nucleation time. Therefore, if the displacement time changes with the injection flow rate, then the flow pattern changes depending on the competition between the displacement and nucleation times. When the displacement time was shorter than the nucleation time, the bubble generation did not follow the onset of VF. First, a VF pattern was formed, and small gas bubbles were then generated in the mixture inside the fingers. On the backbone of the fingers, small gas bubbles lined up and grew bigger with time. Moreover, when the nucleation time was lower than the displacement time, the bubbles coalesced more rapidly, thereby inducing outward flow with gas nucleation in addition to fluid injection. These gas bubbles prevented the mixing of the displacing and displaced fluids. Furthermore, the effects of C6H8O7 concentration and the viscosity ratio were discussed from the viewpoint of the characteristic time.
Radial development of pentanol–biodiesel fuel spray in a high-pressure common-rail system
Authors: Li Fengyu , Lin Qizhao
Published: September 2021

Pentanol is a potential alternative fuel. The effect of blending pentanol on the radial diffusion of biodiesel spray was studied. There are seldom eyes on the comprehensive study on the radial development of spray. For evaluating the radial development ability, the spray characteristic parameters such as the maximum width, the actual distance from the widest part to the nozzle, the cone angle, and the spray mean width were chosen for study. The influences of ambient pressure and injection pressure were also analyzed. The radial diffusion ability of biodiesel spray could be improved by adding pentanol, and it would also be affected by the varying of ambient and injection pressures. With the addition of pentanol, the maximum width of spray increased, the distance from the nozzle to the widest range shortened, the spray cone angle increased, and the average spray width increased, which means the maximum radial diffusivity and average radial diffusivity of the spray were enhanced. When the ambient pressure increased, the distance from the nozzle to the widest range was shortened, the spray cone angle increased, and the average spray width increased. When the injection pressure increased, the maximum spray width of the blended fuel containing a small amount of pentanol increased, the distance from the nozzle to the widest width increased, and the average spray width increased. The maximum radial diffusivity of spray was only affected by ambient pressure, and the average radial diffusion capacity was affected by both ambient pressure and injection pressure.
Transition to turbulence in a heated non-Newtonian pipe flow
Authors: Romanò Francesco , Charles Antoine , Dottori François , Amir Bahrani S.
Published: September 2021

A simplified mono-dimensional model for investigating the transition to turbulence in nonisothermal and non-Newtonian pipe flows is proposed. The flow stability is analyzed within the framework of such a model, showing that uniformly heating the pipe wall leads to an earlier transition to turbulence, while differentially heating the pipe wall produces a stabilizing effect. For power-law fluids, we also demonstrate that an increase in the power-law index, i.e., passing from shear-thinning to shear-thickening fluids, leads to a stabilization of the system.