bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular dynamics of preferential adsorption in mixed alkali–halide electrolytes at graphene electrodes
Authors: Dočkal Jan , Lísal Martin , Moučka Filip
Published: August 2022

Understanding the microscopic behavior of aqueous electrolyte solutions in contact with graphene and related carbon surfaces is important in electrochemical technologies, such as capacitive deionization or supercapacitors. In this work, we focus on preferential adsorption of ions in mixed alkali–halide electrolytes containing different fractions of Li+/Na+ or Li+/K+ and/or Na+/K+ cations with Cl− anions dissolved in water. We performed molecular dynamics simulations of the solutions in contact with both neutral and positively and negatively charged graphene surfaces under ambient conditions, using the effectively polarizable force field. The simulations show that large ions are often intuitively attracted to oppositely charged electrodes. In contrast, the adsorption behavior of small ions tends to be counterintuitive. In mixed-cation solutions, one of the cations always supports the adsorption of the other cation, while the other cation weakens the adsorption of the first cation. In mixed-cation solutions containing large and small cations simultaneously, adsorption of the larger cations varies dramatically with the electrode charge in an intuitive way, while adsorption of the smaller cations changes oppositely, i.e., in a counterintuitive way. For (Li/K)Cl mixed-cation solutions, these effects allow the control of Li+ adsorption by varying the electrode charge, whereas, for LiCl single-salt solutions, Li+ adsorption is nearly independent of the electrode charge. We rationalize this cation–cation lever effect as a result of a competition between three driving forces: (i) direct graphene–ion interactions, (ii) the strong tendency of the solutions to saturate the network of non-covalent intermolecular bonds, and (iii) the tendency to suppress local charge accumulation in any region larger than typical interparticle distances. We analyze the driving forces in detail using a general method for intermolecular bonding based on spatial distribution functions and different contributions to the total charge density profiles. The analysis helps to predict whether an ion is more affected by each of the three driving forces, depending on the strength of the ion solvation shells and the compatibility between the contributions of the charge density profiles due to the ion and water molecules. This approach is general and can also be applied to other solutions under different thermodynamic conditions.
High repetition rate mapping of the interaction between a laser plasma and magnetized background plasma via laser induced fluorescence
Authors: Dorst R. S. , Schaeffer D. B. , Le A. , Pilgram J. J. , Constantin C. G. , Vincena S. , Tripathi S. K. P. , Winske D. , Larson D. , Cowee M. , Niemann C.
Published: August 2022

The laminar coupling of energy between a laser-produced plasma and a background magnetized plasma was investigated via planar laser induced fluorescence diagnostic and magnetic flux probes. Experiments performed on the Large Plasma Device at the University of California, Los Angeles, mapped out the two-dimensional spatiotemporal evolution of the laser-plasma (debris) ion velocity distribution function (VDF) to assess debris-background coupling in a sub-Alfvénic regime. The acquisition of these data necessitates high repetition rate (1 Hz) as each dataset is the accumulation of thousands of laser shots, which would not be feasible in single-shot experiments. Fully kinetic, three-dimensional particle-in-cell simulations are compared to the measured VDFs to provide a framework in which we can understand the coupling of a sub-Alfvénic plasma flow through a preformed, magnetized plasma. The simulations display the same departure from the expected gyromotion of the debris plasma as observed in the experimental data, and in conjunction with the measured magnetic field traces, have led to the direct observation of the collisionless coupling via laminar fields.
Precise equilibrium structures of 1H- and 2H-1,2,3-triazoles (C2H3N3) by millimeter-wave spectroscopy
Authors: Zdanovskaia Maria A. , Esselman Brian J. , Kougias Samuel M. , Amberger Brent K. , Stanton John F. , Woods R. Claude , McMahon Robert J.
Published: August 2022

The 1H- and 2H-1,2,3-triazoles are isomeric five-membered ring, aromatic heterocycles that may undergo chemical equilibration by virtue of intramolecular hydrogen migration (tautomerization). Using millimeter-wave spectroscopy in the 130–375 GHz frequency range, we measured the spectroscopic constants for thirteen 1H-1,2,3-triazole and sixteen 2H-1,2,3-triazole isotopologues. Herein, we provide highly accurate and highly precise semi-experimental equilibrium (reSE) structures for the two tautomers based on the spectroscopic constants of each set of isotopologues, together with vibration–rotation interaction and electron-mass distribution corrections calculated using coupled-cluster singles, doubles, and perturbative triples calculations [CCSD(T)/cc-pCVTZ]. The resultant structures are compared with a “best theoretical estimate” (BTE), which has recently been shown to be in exceptional agreement with the semi-experimental equilibrium structures of other aromatic molecules. Bond distances of the 1H tautomer are determined to <0.0008 Å and bond angles to <0.2°. For the 2H tautomer, bond angles are also determined to <0.2°, but bond distances are less precise (2σ ≤ 0.0015). Agreement between BTE and reSE values is discussed.
Excitonic performance and ultrafast dynamics in defective WSe2
Authors: Zhang Shengxia , Xu Lijun , Hu Peipei , Maaz Khan , Zeng Jian , Zhai Pengfei , Li Zongzhen , Liu Li , Liu Jie
Published: August 2022

Understanding and facilitating defects in two-dimensional transition metal dichalcogenides (TMDCs) are of fundamental importance for their application in optoelectronic devices and valleytronic devices. In this study, swift heavy ion (SHI) irradiation was applied to introduce defects in monolayer WSe2 in a controlled manner. Temperature-dependent photoluminescence and transient absorption spectroscopy are employed to investigate the excitonic performances in defective WSe2. It is observed that the trion emission rises up alongside exciton emission for WSe2 irradiated with elevated ion fluences. Defects introduced by SHI irradiation can strongly localize carriers and weaken the exciton–phonon coupling and further affect the optical signatures of the excitons. Photoexcited electron–hole pairs were suppressed to form excitons due to the weaken phonon scattering, and the population of exciton was reduced for the irradiated WSe2. These results reveal that SHI irradiation is an effective technique to explore defect dependence of exciton formation and evolution dynamics in TMDCs, which have important implications for various optoelectronic applications.
Fine and hyperfine interactions of PbF studied by laser-induced fluorescence spectroscopy
Authors: Zhu Chengcheng , Wang Hailing , Chen Ben , Chen Yini , Yang Tao , Yin Jianping , Liu Jinjun
Published: August 2022

The fine and hyperfine interactions in PbF have been studied using the laser-induced fluorescence (LIF) spectroscopy method. Cold PbF molecular beam was produced by laser-ablating a Pb rod under jet-cooled conditions, followed by the reaction with SF6. The LIF excitation spectrum of the (0, 0) band in the B2Σ+–X2Π1/2 system of the 208PbF, 207PbF, and 206PbF isotopologues has been recorded with rotational, fine structure, and hyperfine-structure resolution. Transitions in the LIF spectrum were assigned and combined with the previous X2Π3/2–X2Π1/2 emission spectrum in the near-infrared region [Ziebarth et al., J. Mol. Spectrosc. 191, 108–116 (1998)] and the X2Π1/2 state pure rotational spectrum of PbF [Mawhorter et al., Phys. Rev. A 84, 022508 (2011)] in a global fit to derive the rotational, spin–orbit, spin–rotation, and hyperfine interaction parameters of the ground (X2Π1/2) and the excited (B2Σ+) electronic states. Molecular constants determined in the present work are compared with previously reported values. Particularly, the significance of the hyperfine parameters, A⊥ and A‖, of 207Pb is discussed.
A short-circuited coplanar waveguide for low-temperature single-port ferromagnetic resonance spectroscopy setup to probe the magnetic properties of ferromagnetic thin films
Authors: Pal Sayani , Aon Soumik , Manna Subhadip , Mitra Chiranjib
Published: August 2022

A coplanar waveguide shorted in one end is proposed, designed, and implemented successfully to measure the properties of magnetic thin films as a part of the vector network analyzer ferromagnetic resonance (FMR) spectroscopy setup. Its simple structure, potential applications, and easy installation inside the cryostat chamber made it advantageous especially for low-temperature measurements. It provides a wide band of frequencies in the gigahertz range essential for FMR measurements. Our spectroscopy setup with a short-circuited coplanar waveguide has been used to extract the Gilbert damping coefficient and effective magnetization values for standard ferromagnetic thin films, such as Permalloy (Py) and Cobalt (Co). The thickness and temperature-dependent studies of those magnetic parameters have also been done here for the afore-mentioned magnetic samples.
Filamentation of the surface plasma layer during the electrical explosion of conductors in strong magnetic fields
Authors: Oreshkin V. I. , Chaikovsky S. A. , Datsko I. M. , Labetskaya N. A. , Oreshkin E. V. , Ratakhin N. A. , Rousskikh A. G. , Vankevich V. A. , Chuvatin A. S.
Published: August 2022

A model has been considered to describe the development of a surface discharge over a conductor electrically exploding in a strong magnetic field. A simulation performed using this model has shown that in the initial stage of the conductor explosion, a plasma layer of several tens of micrometers thick with an electron temperature of several electronvolts is formed on the metal surface. Based on the theory of small perturbations, the development of thermal filamentation instabilities that form in the surface plasma layer has been analyzed. The characteristic growth rates and wavelengths of these instabilities have been determined. The theoretical results were compared with the results of experiments performed on the ZEBRA generator (providing load currents of amplitude about 1 MA and rise time about 100 ns) and on the MIG generator (providing load currents of amplitude about 2 MA and rise time about 100 ns). For the conditions implemented with these generators, the filamentation model gives rise times of thermal filamentation instabilities of tens of nanoseconds at characteristic wavelengths of the order of 100 μm. These values are in good agreement with experimental data, which indicates the adequacy of both the surface discharge development model and the filamentation model.
Electrical characterization and extraction of activation energies of the defect states in the LaAlO3/SrTiO3 heterostructure
Authors: Lechaux Yoann , Chen Yu , Minj Albert , Sánchez Florencio , Herranz Gervasi , Méchin Laurence , Guillet Bruno
Published: August 2022

In this work, we study the electronic properties of defects in the LaAlO3/SrTiO3 heterostructure, which is known to host a high mobility two-dimensional electron gas (2DEG) at the interface. This 2DEG also shows photoconductance, which could be related to defects that act as deep center trapping and releasing carriers by interaction with light. This phenomenon has raised an interest for the identification of deep energy levels in the LaAlO3/SrTiO3 heterostructure. We have studied the defect state properties using electrical characterization such as capacitance–voltage (C–V), current–voltage (I–V) measurements, and deep-level transient Fourier spectroscopy (DLTFS). From C–V and I–V analyses, a hysteresis was observed indicating an effect of mobile charges in the LaAlO3. Using DLTFS, we identify three defect states located at around 0.17 eV below conduction band and at 0.23 and 0.26 eV above the valence band. These defect states were attributed to defects in SrTiO3 such as strontium vacancies or titanium vacancies. We identify a fourth defect state having an energy of about 0.69 eV below the conduction band that could be related to oxygen vacancies in LaAlO3 or in SrTiO3. In addition, the observation of an effect of the electric field with DLTFS indicated that oxygen vacancies might be involved in Fowler–Nordheim or trap-assisted tunneling through the LaAlO3 layer.
Experimental and simulation research on microscopic damage of HTPB propellant under tension-shear loading
Authors: Cui Jia-yuan , Qiang Hong-fu , Wang Jia-xiang
Published: August 2022

In order to study the influence of loading conditions on propellant mesoscopic failure morphology, scanning electron microscopy was carried out to observe the morphology of the failure section of a hydroxyl-terminated polybutadiene propellant under different temperatures, loading speeds, and loading conditions. Using the finite element method, a mesoscopic model of a composite solid propellant was constructed, and the mechanical parameters of the propellant particle–matrix interface were obtained based on the parameter inversion method. A meso-model of a hydroxyl-terminated polybutadiene propellant under different loading conditions was constructed, and numerical results were compared with experimental results to analyze the meso-damage. With decreasing temperature and increasing loading speed, the level of propellant damage increased, and the particle–matrix interface became more prone to damage under the combined action of tensile and shear loads. In addition, with an increasing loading angle, ammonium perchlorate particles were more prone to dewetting.
Resonance broadening effect for relativistic electron interaction with electromagnetic ion cyclotron waves
Authors: Tonoian D. S. , Artemyev A. V. , Zhang X.-J. , Shevelev M. M. , Vainchtein D. L.
Published: August 2022

Relativistic electron scattering by electromagnetic ion cyclotron (EMIC) waves is one of the most effective mechanisms for >1 MeV electron flux depletion in the Earth's radiation belts. Resonant electron interaction with EMIC waves is traditionally described by quasi-linear diffusion equations, although spacecraft observations often report EMIC waves with intensities sufficiently large to trigger nonlinear resonant interaction with electrons. An important consequence of such nonlinear interaction is the resonance broadening effect due to high wave amplitudes. In this study, we quantify this resonance broadening effect in electron pitch-angle diffusion rates. We show that resonance broadening can significantly increase the pitch-angle range of EMIC-scattered electrons. This increase is especially important for ∼1 MeV electrons, where, without the resonance broadening, only those near the loss cone (with low fluxes) can resonate with EMIC waves.
Precessed electron diffraction study of defects and strain in GaN nanowires fabricated by top-down etching
Authors: Martín Gemma , López-Conesa Lluís , Pozo Daniel del , Portillo Quim , Doundoulakis George , Georgakilas Alexandros , Estradé Sònia , Peiró Francesca
Published: August 2022

Gallium nitride (GaN) nanowires (NWs) have been fabricated by top-down etching from GaN heteroepitaxial films, which provides an accurate control of their position and dimensions. However, these NWs contain, similar to the initial GaN films, high density of structural defects such as threading dislocations (TDs). In this work, different strategies to reduce the density of defects along the NWs have been compared based on two different wet etching approaches followed by a rapid thermal annealing (RTA) at 750 °C. The addition of a 30 nm SiNx coating is also explored. The defects and strain/stress along the NWs have been studied by high resolution transmission electron microscopy, diffraction contrast imaging in two-beam conditions and 4D STEM, as well as strain maps calculated from scanning precession electron diffraction measurements. RTA reduced the density of TDs at the middle of GaN NWs with bare surfaces by approximately 25%. The reduction increased to approximately 70% by RTA of GaN NWs with surfaces coated by amorphous SiNx, which is attributed to enhancement of dislocation movements by stresses induced from differential thermal expansion of GaN and SiNx. These results suggest a process route that, if optimized and combined with reduction of NW diameter, could establish etching as an efficient fabrication method for high crystal quality GaN NWs.
A convenient method for assessing steady-state carrier density and lifetime in solar cell materials using pulse excitation measurements
Authors: Handa Taketo , Yamada Takumi , Kanemitsu Yoshihiko
Published: August 2022

We describe the relation of the carrier lifetime of a light-absorber material determined with pulse-excitation time-resolved techniques to the steady-state carrier density and lifetime in a solar cell under continuous-wave excitation. Our approach constitutes a simple experimental examination of the excitation-fluence-dependent carrier lifetime of absorber materials. It provides the steady-state carrier density and lifetime under 1-sun solar illumination for metal halide perovskite solar cells. The determination of the steady-state carrier responses allows the clarification of optical and photovoltaic properties under 1-sun illumination and thus the identification of loss mechanisms in device performance. Model calculations are also provided to show how the carrier lifetime governs the luminescence quantum yields and open-circuit voltages. The calculations quantify a scaling law between a monomolecular recombination lifetime and an open-circuit voltage as a result of a combination of two density-dependent effects.
Temperature-dependent photoluminescence of violet phosphorus quantum dots as temperature sensors
Authors: Zhao Rongzheng , Zhao Xuewen , Liu Shuhao , Cheng Yonghong , Zhang Jinying
Published: August 2022

Violet phosphorus quantum dots (VPQDs) have been recently produced to give intense green photoluminescence with excellent stability. Quantum dots are promising temperature sensors. However, the temperature-dependent photoluminescence of VPQDs is still unexplored. Herein, both the steady-state and time-resolved photoluminescence of VPQDs have been investigated at 263–353 K. With increasing temperature, the photoluminescence of VPQDs has been demonstrated to have decreasing intensity, blue shifts, and broaden bandwidth with excellent temperature reversibility. The non-radiative heat escape was found to cause the intensity to decrease. The blue shift was deduced to be due to the interplay between the electron–phonon renormalization and the thermal expansion. The enhanced exciton–phonon coupling was found to be the main cause of broaden bandwidth. The photoluminescence lifetime of VPQDs was measured to be stable at different temperatures. The non-radiation recombination processes have been demonstrated to play a crucial role in the photoluminescence by linking static and dynamic processes to calculate the radiative rate and non-radiative rate variation with temperature. The activation energy of VPQDs was deduced to be 90.25 meV, which is suitable for temperature sensing. The linear correlation of photoluminescence intensity and peak position to temperature gives more accurate dual mode sensing for a wide-range of ratiometric temperature sensors.
Tuning and controlling antiplane shear wave propagation in elastic membranes
Authors: Liu Mao , Yu Haijie , Wang Ben
Published: August 2022

In this paper, a rotary-focusing device for the antiplane shear wave is constructed to control and guide elastic wave energy transmission in elastic membranes. The designed device can cloak the antiplane shear waves outside the device and has a rotary-focusing effect on the shear waves energy inside the device in a membrane. The multilayered isotropic material properties of the rotary-focusing device are derived based on the transformation and rotary medium method, and a rotation parameter to guide the propagating trajectories of the antiplane shear waves is introduced. The efficiency of the rotary-focusing device for the antiplane shear waves is verified. The stability of shear wave fields in a membrane with the rotary-focusing device is analyzed to study the performance of rotary-focusing. Numerical examples show that the constructed rotary-focusing device for antiplane shear waves can effectively rotate and focus the antiplane shear wave energy into the device for a wide range of exciting frequencies, which can enhance the antiplane shear energy. Therefore, this study can provide theoretical support for potential applications in the fields of energy harvesting and vibration control.
Formation and interaction of multi-dimensional electrostatic ion-acoustic solitons in two-electron temperature plasmas
Authors: Shohaib Muhammad , Masood W. , Alyousef Haifa A. , Siddiq M. , El-Tantawy S. A.
Published: August 2022

Ion-acoustic waves are investigated in an unmagnetized collisionless plasma comprising dynamical ions and inertialess cold and hot (C–H) electrons expressed by Maxwellian, kappa, and (r, q) distributions. The reductive perturbation theory is applied for deriving a modified Kadomtsev–Petviashvili (mKP) equation to examine the characteristics of ion-acoustic structures (solitary waves, IASWs). The Hirota bilinear formalism is used to investigate the propagation of a single soliton and the interaction of two solitons with special reference to space plasmas. It is found that ratio of number density of cold to hot electrons and non-Maxwellian nature of cold electrons not only affect the propagation characteristics of single mKP solitons but also alter the interaction time of the IASWs. It is found that the swiftness of the interaction of solitons for flat-topped distribution surpasses both kappa and Maxwellian distributions. It is also found that the bipolar and tripolar structures depend on the ratio of the propagation vectors. The ranges of electric field amplitude for the IASWs are calculated for C–H electron distributions corresponding to Saturn's B-ring and the region just beyond terrestrial magnetopause, and are shown to agree with Cassini wideband receiver observational data and wideband plasma wave instrument's waveform data.
Deriving force fields with a multiscale approach: From ab initio calculations to molecular-based equations of state
Authors: Lyra Emerson P. , Franco Luís F. M.
Published: August 2022

Using theoretical and computational tools for predicting thermophysical properties of fluid systems and the soft matter has always been of interest to the physical, chemical, and engineering sciences. Certainly, the ultimate goal is to be able to compute these macroscopic properties from first-principles calculations beginning with the very atomic constitution of matter. In this work, Mie potential parameters were obtained through dimer interaction energy curves derived from ab initio calculations to represent methane and substituted-methane molecules in a spherical one-site coarse-grained model. Bottom-up-based Mie potential parameters of this work were compared with top-down-based ones from the statistical associating fluid theory (SAFT) models for the calculation of thermodynamic properties and critical point by molecular dynamics simulations and SAFT-VR Mie equation of state. Results demonstrated that bottom-up-based Mie potential parameters when averaging the Mie potential parameters of a representative population of conformers provide values close to the top-down-based ones from SAFT models and predict well properties of tetrahedral molecules. This shows the level of consistency embedded in the SAFT-VR Mie family of models and confers the status of a purely predictive equation of state for SAFT-VR Mie when a reasonable model is considered to represent a molecule of interest.
Demonstration of MOCVD-grown BGaN with over 10% boron composition
Authors: AlQatari Feras , Liao Che-Hao , Li Xiaohang
Published: August 2022

BGaN is an emerging ultrawide bandgap semiconductor with important applications ranging from power electronics to ultraviolet light emitters. To date, BGaN boron composition has been limited to <10% in the wurtzite phase. Herein, a 200 nm thick high quality mixed-phase BGaN film was grown via horizontal–reactor metalorganic chemical vapor deposition with boron composition exceeding 10%. The growth was performed under low temperature and pressure conditions of 600 °C and 75 Torr, respectively, with a growth rate of 0.29 µm/h. Triethylborane and triethylgallium were used as the source gases for boron and gallium, respectively. Pure nitrogen gas was used as the carrier for all reactants. A root mean square roughness value of 2.56 nm was determined using an atomic force microscopy scan on an area of 5 × 5 µm2. X-ray diffraction (XRD) 2θ–ω scans show a nearly lattice-matched BGaN/AlN film corresponding to a boron composition of ∼10%. A mixed wurtzite and zincblende phase was confirmed via an XRD pole figure and transmission electron microscopy. Additionally, the high crystalline quality of the mixed (002)wz/(111)ZB planes was shown using an XRD rocking curve with 810 arcsec full width at half maximum. The boron composition was precisely measured as 15% using Rutherford backscattering spectrometry combined with nuclear reaction analysis.
Homeostasis limits keratinocyte evolution
Authors: Schenck Ryan O. , Kim Eunjung , Bravo Rafael R. , West Jeffrey , Leedham Simon , Shibata Darryl , Anderson Alexander R. A.
Published: August 2022

Recent studies have revealed that normal human tissues accumulate many somatic mutations. In particular, human skin is riddled with mutations, with multiple subclones of variable sizes. Driver mutations are frequent and tend to have larger subclone sizes, suggesting selection. To begin to understand the histories encoded by these complex somatic mutations, we incorporated genomes into a simple agent-based skin-cell model whose prime directive is homeostasis. In this model, stem-cell survival is random and dependent on proximity to the basement membrane. This simple homeostatic skin model recapitulates the observed log-linear distributions of somatic mutations, where most mutations are found in increasingly smaller subclones that are typically lost with time. Hence, neutral mutations are “passengers” whose fates depend on the random survival of their stem cells, where a rarer larger subclone reflects the survival and spread of mutations acquired earlier in life. The model can also maintain homeostasis and accumulate more frequent and larger driver subclones if these mutations (NOTCH1 and TP53) confer relatively higher persistence in normal skin or during tissue damage (sunlight). Therefore, a relatively simple model of epithelial turnover indicates how observed passenger and driver somatic mutations could accumulate without violating the prime directive of homeostasis in normal human tissues.
Single-cell RNA sequencing uncovers the nuclear decoy lincRNA PIRAT as a regulator of systemic monocyte immunity during COVID-19
Authors: Aznaourova Marina , Schmerer Nils , Janga Harshavardhan , Zhang Zhenhua , Pauck Kim , Bushe Judith , Volkers Sarah M. , Wendisch Daniel , Georg Philipp , Ntini Evgenia , Aillaud Michelle , Gündisch Margrit , Mack Elisabeth , Skevaki Chrysanthi , Keller Christian , Bauer Christian , Bertrams Wilhelm , Marsico Annalisa , Nist Andrea , Stiewe Thorsten , Gruber Achim D. , Ruppert Clemens , Li Yang , Garn Holger , Sander Leif E. , Schmeck Bernd , Schulte Leon N.
Published: August 2022

The systemic immune response to viral infection is shaped by master transcription factors, such as NF-κB, STAT1, or PU.1. Although long noncoding RNAs (lncRNAs) have been suggested as important regulators of transcription factor activity, their contributions to the systemic immunopathologies observed during SARS-CoV-2 infection have remained unknown. Here, we employed a targeted single-cell RNA sequencing approach to reveal lncRNAs differentially expressed in blood leukocytes during severe COVID-19. Our results uncover the lncRNA PIRAT (PU.1-induced regulator of alarmin transcription) as a major PU.1 feedback-regulator in monocytes, governing the production of the alarmins S100A8/A9, key drivers of COVID-19 pathogenesis. Knockout and transgene expression, combined with chromatin-occupancy profiling, characterized PIRAT as a nuclear decoy RNA, keeping PU.1 from binding to alarmin promoters and promoting its binding to pseudogenes in naïve monocytes. NF-κB–dependent PIRAT down-regulation during COVID-19 consequently releases a transcriptional brake, fueling alarmin production. Alarmin expression is additionally enhanced by the up-regulation of the lncRNA LUCAT1, which promotes NF-κB–dependent gene expression at the expense of targets of the JAK-STAT pathway. Our results suggest a major role of nuclear noncoding RNA networks in systemic antiviral responses to SARS-CoV-2 in humans.
Register variation across text lengths
Authors: Liimatta Aatu
Published: August 2022

This paper explores variation in lexico-grammatical register features across text lengths in a large-scale sample of Reddit comments. Very short texts are known to be problematic for many statistical methods, so understanding their nature is important for the corpus-linguistic study of social media, where most contributions are short. I show that the frequencies of linguistic features change with comment length, even between longer comments, although longer texts are often considered similar in statistical terms. Moreover, I classify the variation found between short comments of different lengths into two main patterns, although other patterns can also be found, and there is variation even within these patterns. Furthermore, I interpret the observed differences in terms of register variation. For example, shorter comments appear to be more casual and less edited in terms of their feature makeup, whereas narrative and informational registers seem to favor longer comments.
Thymic epithelial cells require lipid kinase Vps34 for CD4 but not CD8 T cell selection
Authors: Postoak J. Luke , Song Wenqiang , Yang Guan , Guo Xingyi , Xiao Shiyun , Saffold Cherie E. , Zhang Jianhua , Joyce Sebastian , Manley Nancy R. , Wu Lan , Van Kaer Luc
Published: August 2022

The generation of a functional, self-tolerant T cell receptor (TCR) repertoire depends on interactions between developing thymocytes and antigen-presenting thymic epithelial cells (TECs). Cortical TECs (cTECs) rely on unique antigen-processing machinery to generate self-peptides specialized for T cell positive selection. In our current study, we focus on the lipid kinase Vps34, which has been implicated in autophagy and endocytic vesicle trafficking. We show that loss of Vps34 in TECs causes profound defects in the positive selection of the CD4 T cell lineage but not the CD8 T cell lineage. Utilizing TCR sequencing, we show that T cell selection in conditional mutants causes altered repertoire properties including reduced clonal sharing. cTECs from mutant mice display an increased abundance of invariant chain intermediates bound to surface MHC class II molecules, indicating altered antigen processing. Collectively, these studies identify lipid kinase Vps34 as an important contributor to the repertoire of selecting ligands processed and presented by TECs to developing CD4 T cells.
A fake instability in string inflation
Authors: Cicoli Michele , Guidetti Veronica , Muia Francesco , Pedro Francisco G , Vacca Gian Paolo
Published: August 2022

In type IIB fibre inflation models the inflation is a Kähler modulus which is kinetically coupled to the corresponding axion. In this setup the curvature of the field space induces tachyonic isocurvature perturbations normal to the background inflationary trajectory. However we argue that the associated instability is unphysical since it is due to the use of ill-defined entropy variables. In fact, upon using the correct relative entropy perturbation, we show that in fibre inflation axionic isocurvature perturbations decay during inflation and the dynamics is essentially single-field.
Photo-induced image current
Authors: Koksal K , Celik F A
Published: August 2022

We study the possibility of generation of photo-induced image currents at a distance from the surface of nano-sized metal clusters by using the time-dependent perturbation theory. We reveal that the wave function of an electron excited to the image state is localized outside the surface and the current flows in a spherical shell whose radius is a few times the radius of the sphere. Circularly polarized light has been applied to a perfect icosahedral metal cluster Li13 whose optimization is achieved by molecular dynamic simulation and band structure is obtained by the DFT method and by the solution of the radial Schrödinger equation. To the best of our knowledge, despite the great effort put into determining their characteristics, image electrons have not been the subject of studies on photo-induced current.
Molecular transistors as substitutes for quantum information applications
Authors: Dhingra Archit , Hu Xuedong , Borunda Mario F , Johnson Joseph F , Binek Christian , Bird Jonathan , N’Diaye Alpha T , Sutter Jean-Pascal , Delahaye Emilie , Switzer Eric D , Barco Enrique del , Rahman Talat S , Dowben Peter A
Published: August 2022

Applications of quantum information science (QIS) generally rely on the generation and manipulation of qubits. Still, there are ways to envision a device with a continuous readout, but without the entangled states. This concise perspective includes a discussion on an alternative to the qubit, namely the solid-state version of the Mach–Zehnder interferometer, in which the local moments and spin polarization replace light polarization. In this context, we provide some insights into the mathematics that dictates the fundamental working principles of quantum information processes that involve molecular systems with large magnetic anisotropy. Transistors based on such systems lead to the possibility of fabricating logic gates that do not require entangled states. Furthermore, some novel approaches, worthy of some consideration, exist to address the issues pertaining to the scalability of quantum devices, but face the challenge of finding the suitable materials for desired functionality that resemble what is sought from QIS devices.
Mathematical model of solidification of melt with high-speed cooling
Authors: Dudorov M V , Drozin A D , Stryukov A V , Roshchin V E
Published: August 2022

A new mathematical model of supercooled melt crystallization based on the variational principles of thermodynamics has been developed. The model takes into account the crystal formation and diffusion growth regularities, as well as the diffusionless crystal growth with the deviation from the local equilibrium at the surface. The model also takes into account the growing crystals mutual influence on the components concentration in the melt. The calculations for the supercooled eutectic melt Fe83B17 showed that the nucleation and growth of the phases Fe and Fe2B with a metastable phase Fe3B occur in the melt. The local equilibrium on the surface of the growing Fe3B crystals with the melt probably does not maintained. The regularities of the nucleation and mutual influence of the growing crystals of the phases are studied. The nucleation and growth rate of the Fe3B nuclei differs from the growth of Fe and Fe2B nuclei due to the diffusionless capture of boron atoms by the growing Fe3B crystals surface. The model will help to calculate the melt cooling technology mode for producing amorphous ribbons on a copper rotating drum. The calculation made it possible to analyze changes in the temperature and the crystallization degree in the various ribbon layers. The calculation results have been verified experimentally by x-ray diffraction and calorimetric studies of the obtained ribbons. The correspondence of the calculation and the experimental results confirms the effectiveness developed methodology for studying the regularities of crystal growth in supercooled melts.
The uniqueness and monotonicity of incompressible jet with two fluids*
Authors: Du Lili , Huang Jinli
Published: August 2022

In the previous paper by Alt et al (1984 Indiana Univ. Math. J.
33 367–91), the existence of the symmetric plane flows of two fluids with two free boundaries has been established by variational approach. However, the uniqueness of the two-phase fluids with two free boundaries is an unsolved problem. In the present paper, we will deal with the uniqueness of the two-phase fluids. In addition, if we assume that the two nozzles both converge, we shall show the monotonicity of the two free boundaries of the incompressible two-phase fluids issuing from these two nozzles.
Underdamped oscillations of a mass between two springs
Authors: Herrera-Suárez H J , Morales-Aranguren H L , Muñoz J H , Ossa-Novoa J
Published: August 2022

The oscillations of one mass m suspended between two different springs, assuming a friction force proportional to the velocity

(

x
˙

)

, have been studied. For this purpose, an assembly for this system has been made. The movement of the mass is recorded with a smartphone and analysed with Tracker. It is obtained that the graph of the position of the mass m in function of the time is similar to that of an underdamped harmonic oscillator. The registered data with Tracker are exported to Excel and fit to a nonlinear model through the expression

x
(
t
)
=
A

e

−
λ
t

sin
(
ω
t
+
α
)

. The nonlinear equation of motion is numerically solved with the free Octave package. This solution es very sensitive to the mass of the particle and the stretching of the springs.
Comparison of student performance between virtual and in-person modalities of introductory calculus-based physics
Authors: Haldolaarachchige Neel , Hettiarachchilage Kalani
Published: August 2022

Physics educators keep adding many skill developments to science and engineering students during their education as individuals and groups including critical thinking, conceptual understanding, problem-solving, mathematical implementation, computational implementation, etc. Here, we are discussing how to reach and analyse students’ outcomes within the context of introductory calculus-based physics courses by investigating two different teaching modalities. We found that there is no significant impact of teaching modality on student learning. By performing two different assessments: chapter-ending midterm assessments and unit-based (three to four chapters) midterm assessments, shows that students can perform much better with short-time assessments in contrast to the long-time assessments. Further, we study any possible effects on students’ final grades from students’ prior knowledge of calculus and conceptual physics. This investigation shows that although there is no correlation between student’s prior proficiency in calculus the class performance, however, there is a correlation of conceptual physics understanding towards class performance.
Monte Carlo optimization of a GRID collimator for preclinical megavoltage ultra-high dose rate spatially-fractionated radiation therapy
Authors: Clements Nathan , Bazalova-Carter Magdalena , Esplen Nolan
Published: August 2022

Objective. A 2-dimensional pre-clinical SFRT (GRID) collimator was designed for use on the ultra-high dose rate (UHDR) 10 MV ARIEL beamline at TRIUMF. TOPAS Monte Carlo simulations were used to determine optimal collimator geometry with respect to various dosimetric quantities. Approach. The GRID-averaged peak-to-valley dose ratio (PVDR) and mean dose rate of the peaks were investigated with the intent of maximizing both values in a given design. The effects of collimator thickness, focus position, septal width, and hole width on these metrics were found by testing a range of values for each parameter on a cylindrical GRID collimator. For each tested collimator geometry, photon beams with energies of 10, 5, and 1 MV were transported through the collimator and dose rates were calculated at various depths in a water phantom located 1.0 cm from the collimator exit. Main results. In our optimization, hole width proved to be the only collimator parameter which increased both PVDR and peak dose rates. From the optimization results, it was determined that our optimized design would be one which achieves the maximum dose rate for a PVDR

≥
5

at 10 MV. Ultimately, this was achieved using a collimator with a thickness of 75 mm, 0.8 mm septal and hole widths, and a focus position matched to the beam divergence. This optimized collimator maintained the PVDR of 5 in the phantom between water depths of 0–10 cm at 10 MV and had a mean peak dose rate of

3.06
±
0.02

Gy

s

−
1

at 0–1 cm depth. Significance. We have investigated the impact of various GRID-collimator design parameters on the dose rate and spatial fractionation of 10, 5, and 1 MV photon beams. The optimized collimator design for the 10 MV ultra-high dose rate photon beam could become a useful tool for radiobiology studies synergizing the effects of ultra-high dose rate (FLASH) delivery and spatial fractionation.
Polynomial synchronization of complex-valued inertial neural networks with multi-proportional delays
Authors: Yao Zhuang , Zhang Ziye , Wang Zhen , Lin Chong , Chen Jian
Published: August 2022

This paper investigates the polynomial synchronization (PS) problem of complex-valued inertial neural networks with multi-proportional delays. It is analyzed based on the non-separation method. Firstly, an exponential transformation is applied and an appropriate controller is designed. Then, a new sufficient criterion for PS of the considered system is derived by the Lyapunov function approach and some inequalities techniques. In the end, a numerical example is given to illustrate the effectiveness of the obtained result.
Complex field verification using a large area CMOS MAPS upstream in radiotherapy
Authors: Pritchard J.L. , Velthuis J.J. , Beck L. , Li Y. , De Sio C. , Ballisat L. , Duan J. , Shi Y. , Hugtenburg R.P.
Published: August 2022

A multileaf collimator (MLC) is an integral component in modern radiotherapy machines as it dynamically shapes the photon field used for patient treatment. Currently, the MLC leaves which collimate the treatment field are mechanically calibrated to ±1 mm every 3 months and during pre-treatment calibration are calibrated to the mechanically set leaf positions. Leaf drift can occur between calibration dates and hence exceed the ±1 mm tolerance. Pre-treatment verification, increases LINAC usage time so is seldom performed for each individual patient treatment, but instead for an acceptable sample of patients and/or treatment fractions. Independent real-time treatment verification is therefore desirable. We are developing a large area CMOS MAPS upstream of the patient to monitor MLC leaf positions for real-time treatment verification. CMOS MAPS are radiation hard for photon and electron irradiation, have high readout speeds and low attenuation which makes them an ideal upstream radiation detector for radiotherapy. Previously, we reported on leaf position reconstruction for single leaves using the Lassena, a 12 × 14 cm2, three side buttable MAPS suitable for clinical deployment. Sobel operator based methods were used for edge reconstruction. It was shown that the correspondence between reconstructed and set leaf position was excellent and resolutions ranged between 60.6 ± 8 and 109 ± 12 μm for a single central leaf with leaf extensions ranging from 1 to 35 mm using 0.3 sec of treatment beam time at 400 MU/min. Here, we report on leaf edge reconstruction using updated methods for complex leaf configurations, as occur in clinical use. Results show that leaf positions can be reconstructed with resolutions of 62 ± 6 μm for single leaves and 86 ± 16 μm for adjacent leaves at the isocenter using 0.15 sec at 400 MU/min of treatment beam. These resolutions are significantly better than current calibration standards.
A bioinspired fishbone continuum robot with rigid-flexible-soft coupling structure
Authors: Zhou Pan , Yao Jiantao , Zhang Shuai , Wei Chunjie , Zhang Hongyu , Qi Shupeng
Published: August 2022

Rigid-flexible-soft coupled robots are an important development direction of robotics, which face many theoretical and technical challenges in their design, manufacture, and modeling. Inspired by fishbones, we propose a novel cable-driven single-backbone continuum robot which has a compact structure, is lightweight, and has high dexterity. In contrast to the existing single-backbone continuum robots, the middle backbone of the continuum robot is serially formed by multiple cross-arranged bioinspired fishbone units. The proposed bioinspired fishbone unit, having good one-dimensional bending properties, is a special rigid-flexible-soft structure mainly made by multi-material 3D printing technology. The unique design and manufacture of the middle backbone provide the continuum robot with excellent constant curvature characteristics and reduce the coupling between different motion dimensions, laying a foundation for the continuum robot to have a more accurate theoretical model as well as regular and controllable deformation. Moreover, we build the forward and inverse kinematics model based on the geometric analysis method, and analyze its workspace. Further, the comparison between the experimental and theoretical results shows that the prediction errors of the kinematics model are within the desired 0.5 mm. Also, we establish the relation between the cable driving force of the bioinspired fishbone unit and its bending angle, which can provide guidance for the optimization of the continuum robot in the future. The application demos prove that the continuum robot has good dexterity and compliance, and can perform tasks such as obstacle crossing locomotion and narrow space transportation. This work provides new ideas for the bioinspired design and high-precision modeling of continuum robots.
Shocks, socio-economic status, and food security across Kenya: policy implications for achieving the Zero Hunger goal
Authors: Mutea Emily , Hossain Md Sarwar , Ahmed Ali , Ifejika Speranza Chinwe
Published: August 2022

This study assessed the association between shocks, socio-economic factors, and household food security across Kenya, and provided policy implications for achieving the Zero Hunger goal at national and local levels in Kenya. We analysed the Kenya Integrated Household Budget Survey 2015–16 data for 24 000 households by employing regression models. Our multiple findings show that: (a) half of the surveyed population across Kenya were food insecure; (b) large disparities in food security status exist across the country; (c) demographics (e.g. gender, urban areas), and other socio-economic aspects (e.g. education, income, remittances), positively influence food security; and (d) social and economic shocks negatively influence food security. In summary, the food security status in Kenya is not satisfactory. Our findings suggest that, in general, achieving the sustainable development goals (SDGs) Zero Hunger goal by 2030 will likely remain challenging for Kenya. Ultimately, a redoubling of efforts is required to achieve SDG 10 (reducing inequality) to ensure no one is left behind. Further, the findings could be useful in the formulation and implementation of national and regional policies for achieving the Zero Hunger goal by 2030 in Kenya.