bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen peroxide production from oxygen and formic acid by homogeneous Ir–Ni catalyst
Authors: Shimoyama Yoshihiro , Ohgomori Yuji , Kon Yoshihiro , Hong Dachao
Published: May 2021

Hydrogen peroxide was directly produced from oxygen and formic acid, catalysed by a hetero-dinuclear Ir–Ni complex with two adjacent sites, at ambient temperature.
Principles of interlayer-spacing regulation of layered vanadium phosphates for superior zinc-ion batteries
Authors: Hu Linfeng , Wu Zeyi , Lu Chengjie , Ye Fei , Liu Qiang , Sun Zhengming
Published: May 2021

Phenylamine molecules can be controllably introduced into the interlayer spacing of layered VOPO4 to regulate the interlayer spacing. An approximate linear dependence between Zn2+ storage specific capacity and interlayer spacing is revealed.
Development of methods for Mg, Sr and Pb isotopic analysis of crude oil by MC-ICP-MS: addressing the challenges of sample decomposition
Authors: Henn Alessandra S. , Chernonozhkin Stepan M. , Vanhaecke Frank , Flores Erico M. M.
Published: May 2021

In this work, methods were developed for the determination of isotope ratios of Mg, Sr and Pb in crude oil by multi-collector inductively coupled plasma-mass spectrometry.
Synthesis and structure–activity relationships of 3,4,5-trisubstituted-1,2,4-triazoles: high affinity and selective somatostatin receptor-4 agonists for Alzheimer's disease treatment
Authors: Neumann William L. , Sandoval Karin E. , Mobayen Shirin , Minaeian Mahsa , Kukielski Stephen G. , Srabony Khush N. , Frare Rafael , Slater Olivia , Farr Susan A. , Niehoff Michael L. , Hospital Audrey , Kontoyianni Maria , Crider A. Michael , Witt Ken A.
Published: May 2021

3,4,5-Trisubstituted-1,2,4-triazole somatostatin receptor-4 agonist SAR.
Cyano-substituted oligo(p-phenylene-vinylene)s having linear and branched octyloxy groups: control of aggregation and emission properties via C8 alkyl chain difference
Authors: Hayashi Shotaro
Published: May 2021

Alkyl chain structures, linear and branched C8, induced the tuning of H- and J-aggregation, resulting in different solid-state optical properties.
Time-dependent re-organization of biological processes by the analysis of the dynamic transcriptional response of yeast cells to doxorubicin
Authors: Karabekmez Muhammed Erkan , Taymaz-Nikerel Hilal , Eraslan Serpil , Kirdar Betul
Published: May 2021

Integration of co-expression clusters with TFs involved in the dynamic regulatory events revealed re-organization of the transcriptional landscape in S. cerevisae cells in reaction to a sudden pulse of the chemotherapeutic agent doxorubicin.
3-R-4-(5-Methyleneazide-1,2,4-oxadiazol-3-yl)furazan and its ionic salts as low-sensitivity and high-detonation energetic materials
Authors: Yang Rui , Liu Yifei , Dong Zhen , Li Haiyan , Ye Zhiwen
Published: May 2021

3-R-4-(5-Methyleneazide-1,2,4-oxadiazol-3-yl)furazan compounds as low-sensitivity and high-detonation energetic materials.
A study on the cataluminescence of propylene oxide on FeNi layered double hydroxides/graphene oxide
Authors: Li Ming , Hu Yufei , Li Gongke
Published: May 2021

In this work, FeNi layered double hydroxides/graphene oxide (FeNi LDH/GO) was prepared, which exhibits excellent selective cataluminescent performance towards propylene oxide.
Fabrication of a solid sensor based on a phenazine derivative film for enhancing the sensing properties of biogenic amine and applying for monitoring shrimp freshness
Authors: Qi Xiao-Ni , Zhang You-Ming , Yao Hong , Lin Qi , Wei Tai-Bao
Published: May 2021

In practical applications, fixing a fluorescent sensor on a solid composite film matrix can settle the boundaries of keeping the sensor in the solution state.
Na3VO4as a new anode material for lithium-ion batteries
Authors: Lu Junlin , Zhang Dongmei , Wang Yueqi , Ni Shibing
Published: May 2021

The electrochemical performance of Na3VO4as a new anode material for lithium-ion batteries is assessed for the first time.
Cu-Doped Co3O4 microstructure as an efficient non-noble metal electrocatalyst for methanol oxidation in a basic solution
Authors: Zhao Shuang , Yang Hui , Liu Yaru , Xing Yaodong , Cui Guangwen , Liu Qingyun
Published: May 2021

Co3O4 doped with copper at different concentrations was used to catalyze methanol oxidation reactions.
The synthesis of the very long chain polyunsaturated fatty acid (VLC-PUFA) 32:6 n-3
Authors: Wade Alexander , Rallabandi Rameshu , Lucas Steven , Oberg Catrina , Gorusupudi Aruna , Bernstein Paul S. , Rainier Jon D.
Published: May 2021

This work describes the synthesis of the VLC-PUFA 32:6 n-3 along with its uptake into mouse retinal tissue.
Sequential one-pot synthesis of N-sulfonyl spiroaziridine oxindoles from spiroepoxy oxindoles
Authors: Biswas Anurag , Saleh SK Abu , Hazra Atanu , Debnath Subhas Chandra , Hajra Saumen
Published: May 2021

A sequential one-pot direct strategy for N-sulfonyl spiroaziridine oxindoles has been developed from spiroepoxy oxindoles with excellent yields by regioselective amination of spiroepoxide and a subsequent ring enclosure reaction of amino alcohol.
Acetyl nitrate mediated conversion of methyl ketones to diverse carboxylic acid derivatives
Authors: Capilato Joseph N. , Pellegrinelli Peter J. , Bernard Josephine , Schnorbus Logan , Philippi Shane , Mattiucci Joseph , Hoy Erik P. , Perez Lark J.
Published: May 2021

The development of a novel acetyl nitrate mediated oxidative conversion of methyl ketones to carboxylic acid derivatives is described. We demonstrate examples and propose a mechanism for this transformation.
Cross-Validation and Normative Values for the German Vocal Tract Discomfort Scale
Authors: Lukaschyk Julia , Abel Jakob , Brockmann-Bauser Meike , Keilmann Annerose , Braun Angelika , Rohlfs Anna-Katharina
Published: May 2021

Purpose

The Vocal Tract Discomfort Scale (VTD Scale) is a self-rating questionnaire investigating physical symptoms in the larynx associated with vocal pathology. The aim of this work was to investigate the reliability, validity, sensitivity, and specificity of the first German version and to provide normative data with thresholds for pathology and a scaling scheme.

Study Design

A retrospective multicenter study was performed.

Method

A total of 571 participants (409 female and 162 male), with a mean age of 47.2 years, were recruited at three German centers; of these, there were 447 participants with voice disorder and 124 vocally healthy participants. The clinical examination consisted of patient history, visual laryngeal examination, acoustic and aerodynamic assessment, perceptual analysis by the Grading-Roughness-Breathiness-Asthenia-Strain Scale, and subjective evaluation using the VTD Scale and the Voice Handicap Index (VHI). Statistics included group comparisons (
t
test and analysis of variance), Pearson correlation coefficient (between VTD Scale and VHI), and Cronbach's alpha to assess validity and reliability. Analysis of receiver operating characteristics was performed to examine VTD Scale's discriminatory ability and provide a cutoff score. Additionally, percentiles were applied to provide VTD Scale ranges.

Results

There were highly significant differences between healthy participants and participants with voice disorder regarding the total score and both subscales of the VTD Scale. Internal consistency was excellent (α = .928). We found moderate, positive correlation between the VTD Scale and VHI (ρ = .596,
p
< .001). Receiver operating characteristics analysis showed an area under the curve of 0.876 (
p
< .001, 95% confidence interval [0.846, 0.906]). VTD Scale ranges were no (score: 0–13), mild (score: 14–26), moderate (score: 27–40), and severe (score: 41–96) disorder.

Conclusions

Results confirm an excellent reliability and validity of the German VTD Scale. It provides additional and independent diagnostic information and is a useful instrument to complement voice assessment. The scaling into four severity subgroups allows the tool to be used for screening patients and considers a transferral to a voice specialist.
Investigating ionospheric calibration for LOFAR 2.0 with simulated observations
Authors: Edler H. W. , de Gasperin F. , Rafferty D.
Published: May 2021

Context. There are a number of hardware upgrades for the Low-Frequency Array (LOFAR) currently under development. These upgrades are collectively referred to as the LOFAR 2.0 upgrade. The first stage of LOFAR 2.0 will introduce a distributed clock signal and allow for simultaneous observations using all the low-band and high-band antennas of the array.

Aims. Our aim is to provide a tool for obtaining accurate simulations for LOFAR 2.0.

Methods. We present our software for simulating LOFAR and LOFAR 2.0 observations, which includes realistic models for all important systematic effects such as the first- and second-order ionospheric corruptions, time-variable primary-beam attenuation, station-based delays, and bandpass response. The ionosphere is represented as a thin layer of frozen turbulence. Furthermore, thermal noise can be added to the simulation at the expected level. We simulate a full eight-hour simultaneous low- and high-band antenna observation of a calibrator source and a target field with the LOFAR 2.0 instrument. The simulated data are calibrated using readjusted LOFAR calibration strategies. We examine novel approaches of solution-transfer and joint calibration to improve direction-dependent ionospheric calibration for LOFAR.

Results. We find that the calibration of the simulated data behaves very similarly to a real observation and reproduces certain characteristic properties of LOFAR data, such as realistic solutions and image quality. We analyze strategies for direction-dependent calibration of LOFAR 2.0 and find that the ionospheric parameters can be determined most accurately when combining the information of the high-band and low-band in a joint calibration approach. In contrast, the transfer of total electron content solutions from the high-band to the low-band shows good convergence but is highly susceptible to the presence of non-ionospheric phase errors in the data.
Impact of common envelope development criteria on the formation of LIGO/Virgo sources
Authors: Olejak A. , Belczynski K. , Ivanova N.
Published: May 2021

The treatment and criteria for development of unstable Roche lobe overflow (RLOF) that leads to the common envelope (CE) phase have hindered the area of evolutionary predictions for decades. In particular, the formation of black hole-black hole (BH-BH), black hole-neutron star (BH-NS), and neutron star-neutron star (NS-NS) merging binaries depends sensitively on the CE phase in classical isolated binary evolution model. All these mergers are now reported as LIGO/Virgo sources or source candidates. CE is even considered by some as a mandatory phase in the formation of BH-BH, BH-NS, or NS-NS mergers in binary evolution models. At the moment, there is no full first-principles model for the development of the CE. We employed the StarTrack population synthesis code to test the current advancements in studies on the stability of RLOF for massive donors to assess their effect on the LIGO/Virgo source population. In particular, we allowed for more restrictive CE development criteria for massive donors (M >  18 M⊙). We also tested a modified condition for switching between different types of stable mass transfer and between the thermal or nuclear timescale. The implemented modifications significantly influence the basic properties of merging double compact objects, sometimes in non-intuitive ways. For one of the tested models, with restricted CE development criteria, the local merger rate density for BH-BH systems increased by a factor of 2–3 due to the emergence of a new dominant formation scenario without any CE phase. We find that the changes in highly uncertain assumptions on RLOF physics may significantly affect: (i) the local merger rate density; (ii) shape of the mass and mass ratio distributions; and (iii) dominant evolutionary formation (with and without CE) scenarios of LIGO/Virgo sources. Our results demonstrate that without sufficiently strong constraints on RLOF physics, it is not possible to draw fully reliable conclusions about the population of double compact object systems based on population synthesis studies.
Zipf’s law for cosmic structures: How large are the greatest structures in the universe?
Authors: De Marzo Giordano , Sylos Labini Francesco , Pietronero Luciano
Published: May 2021

The statistical characterization of the distribution of visible matter in the universe is a central problem in modern cosmology. In this respect, a crucial question still lacking a definitive answer concerns how large the greatest structures in the universe are. This point is closely related to whether or not such a distribution can be approximated as being homogeneous on large enough scales. Here we assess this problem by considering the size distribution of superclusters of galaxies and by leveraging the properties of Zipf–Mandelbrot law, providing a novel approach which complements the standard analysis based on the correlation functions. We find that galaxy superclusters are well described by a pure Zipf’s law with no deviations and this implies that all the catalogs currently available are not sufficiently large to spot a truncation in the power-law behavior. This finding provides evidence that structures larger than the greatest superclusters already observed are expected to be found when deeper redshift surveys will be completed. As a consequence, the scale beyond which galaxy distribution crossovers toward homogeneity, if any, should increase accordingly.
Role of some modifiers on the thermo-mechanical properties of Se90In10 chalcogenide glass (ChGs)
Authors: Dahshan Alaa , Kumar Horesh , Mehta Neeraj
Published: May 2021

The studies on the micro-hardness of ChGs provide useful information regarding their straightforward involvement in the fabrication of sensors, fibers, and other optical elements for direct use in infrared optics. This work deals with the mechanical response of the glassy Se90In10 alloy under the influence of additives (Sn, Ag, Sb, and Ge). For this, we have determined the micro-hardness of all glassy alloys. Using the values of Vickers hardness (Hv), glass transition temperature (Tg), and present glasses, we have calculated the other significant thermo-mechanical parameters. The effect of Sn, Ag, Sb, and Ge additives on the micro-hardness of glassy Se90In10 alloy is also discussed.
Revalidation of the Spanish stone loach Barbatula hispanica (Lelek, 1987) (Teleostei, Nemacheilidae) according to morphological and mitochondrial data
Authors: Denys Gaël P.J. , Perea Silvia , Dettai Agnès , Gauliard Camille , Persat Henri , Doadrio Ignacio
Published: May 2021

This study revalidates Barbatula hispanica, previously considered a junior synonym of B. quignardi. This species is found in the Ebro drainage and in Cantabria (Spain) as well as in the Adour drainage (Southwestern France). It is characterized by an upper lip with a well-marked medial incision and an interorbital width 18.5–33.7% of the HL. The species delineation is corroborated by the cytochrome oxidase subunit 1 molecular marker. We provide the sequence of 12S rDNA (950 bp) as reference for environmental DNA studies, and discuss also the taxonomy of B. quignardi which would be restricted to the Lez River.
A generalized kinetic model of the advection-dispersion process in a sorbing medium
Authors: Vieru Dumitru , Fetecau Constantin , Ahmed Najma , Shah Nehad Ali
Published: May 2021

A new time-fractional derivative with Mittag-Leffler memory kernel, called the generalized Atangana-Baleanu time-fractional derivative is defined along with the associated integral operator. Some properties of the new operators are proved. The new operator is suitable to generate by particularization the known Atangana-Baleanu, Caputo-Fabrizio and Caputo time-fractional derivatives. A generalized mathematical model of the advection-dispersion process with kinetic adsorption is formulated by considering the constitutive equation of the diffusive flux with the new generalized time-fractional derivative. Analytical solutions of the generalized advection-dispersion equation with kinetic adsorption are determined using the Laplace transform method. The solution corresponding to the ordinary model is compared with solutions corresponding to the four models with fractional derivatives.
Experiments on plasma arcs at a water–air interface
Authors: Jacobs M. , Gekelman W. , Pribyl P. , Qian Y. , Abarzhi S.
Published: May 2021

An exploding water plasma experiment at UCLA investigated the expansion and morphology of a fireball with and without an external magnetic field. Diagnostics include photographs and movies (which may be downloaded) acquired with a framing camera, magnetic probes, and visible light spectra. The expansion and internal magnetic fields are very different from the unmagnetized case when a magnetic field of order 300G is applied along the expansion axis. Visible light spectra are brighter and additional lines are seen in the presence of the magnetic field. The experiment can serve as a platform for studies of interfacial mixing and possibly shed light on very different processes such as laser target physics.
A fast spectral method for electrostatics in doubly periodic slit channels
Authors: Maxian Ondrej , Peláez Raúl P. , Greengard Leslie , Donev Aleksandar
Published: May 2021

We develop a fast method for computing the electrostatic energy and forces for a collection of charges in doubly periodic slabs with jumps in the dielectric permittivity at the slab boundaries. Our method achieves spectral accuracy by using Ewald splitting to replace the original Poisson equation for nearly singular sources with a smooth far-field Poisson equation, combined with a localized near-field correction. Unlike existing spectral Ewald methods, which make use of the Fourier transform in the aperiodic direction, we recast the problem as a two-point boundary value problem in the aperiodic direction for each transverse Fourier mode for which exact analytic boundary conditions are available. We solve each of these boundary value problems using a fast, well-conditioned Chebyshev method. In the presence of dielectric jumps, combining Ewald splitting with the classical method of images results in smoothed charge distributions, which overlap the dielectric boundaries themselves. We show how to preserve the spectral accuracy in this case through the use of a harmonic correction, which involves solving a simple Laplace equation with smooth boundary data. We implement our method on graphical processing units and combine our doubly periodic Poisson solver with Brownian dynamics to study the equilibrium structure of double layers in binary electrolytes confined by dielectric boundaries. Consistent with prior studies, we find strong charge depletion near the interfaces due to repulsive interactions with image charges, which points to the need for incorporating polarization effects in understanding confined electrolytes, both theoretically and computationally.
On the temporal linear stability of the asymptotic suction boundary layer
Authors: Yalcin A. , Turkac Y. , Oberlack M.
Published: May 2021

A temporal linear stability analysis of the asymptotic suction boundary layer is presented. For this, the Orr–Sommerfeld equation is solved in terms of generalized hypergeometric functions. Together with the corresponding boundary conditions, an algebraic eigenvalue problem is formulated. Thereof we derive the temporal continuous spectrum yielding a rather distinct spectrum if, for example, compared to the one from the Blasius solution. A second key result is that the discrete spectrum in the limits α→0,that is, small streamwise wave numbers, and Re→∞ is only present in the distinguished limit Re α=O(1). This results in a degenerated Orr–Sommerfeld equation and the expanded algebraic eigenvalue problem poses a lower limit of (Re α)min≈0.841 91. We show that this lower bound corresponds to a maximum extension of the viscous eigenfunction in the wall-normal direction. The full algebraic eigenvalue problem is numerically solved for the temporal case up to Re=6.0×106. Besides the further refined critical values αcr=0.155 46,  ωcr=0.023 297,  Recr=54 378.620 32, discrete spectra and eigenfunctions are examined and ω=ωr+iωi is the complex frequency. In particular, eigenvalue spectra are investigated with regard to their behavior due to a variation of the Reynolds number and the wave number, respectively, and only A-modes according to the definition of Mack [“A numerical study of the temporal eigenvalue spectrum of the Blasius boundary layer,” J. Fluid Mech. 73, 497–520 (1976)] were identified. From these, three different classes of eigenfunctions of the wall-normal disturbance velocity are presented. Finally, we find that the inviscid part of the eigenfunctions is dominant in wall-normal direction and only propagates in streamwise direction, while the viscous part is limited to the vicinity of the wall and propagates toward it in an almost perpendicular direction.
Local-probe based electrical characterization of a multiphase intermetallic γ-TiAl based alloy
Authors: Kratzer M. , Huszar M. , Tengg L. , Billovits T. , Kaufmann B. , Supancic P. , Clemens H. , Mayer S. , Teichert C.
Published: May 2021

The requirements for high performance and low energy consumption call for novel light-weight high-temperature structural materials. A possible answer can be intermetallic γ-TiAl-based alloys, which—in terms of weight—clearly outperform the classical Ni based alloys. However, not only their mechanical properties, such as high specific strength and high creep resistance, are important for device design and use, but also their electrical behavior is of significant importance. In order to correctly interpret the results of electrical material testing techniques, such as eddy current testing, a profound knowledge on the electrical properties is essential. In this study, local-probe techniques, such as conductive atomic force microscopy (CAFM) and micro four-point probe (μ4PP) measurements, were used to determine the specific resistivity of the constituent phases of a Ti-43.5Al-4Nb-1Mo-0.1B (at. %) TNM γ-TiAl based alloy. It turned out that the different phases exhibit noticeably different resistivity values, which vary over two orders of magnitude, whereas the βo phase has the smallest resistivity and the α2 phase the highest. CAFM and μ4PP results were in rather good agreement for the α2 and γ phases with resistivity values of ρα2,CAFM = (1.0 ± 0.7) × 10−5 Ω m and ρα2,4PP = (1.5 ± 1.5) × 10−5 Ω m for the α2-phase, and ργ,CAFM = (6.5 ± 2.1) × 10−6 Ω m, and ργ,4PP = (1.4 ± 1.2) × 10−6 Ω m for the γ-phase. For the βo phase, μ4PP measurements resulted in ρβo,4PP = (9.0 ± 5.0) × 10−7 Ω m. In this case, CAFM values are not reliable due to the formation of a contact barrier that deteriorates the measurements.
Approximate analytical solution for the flow of a Phan-Thien–Tanner fluid through an axisymmetric hyperbolic contraction with slip boundary condition
Authors: Pérez-Salas Karen Y. , Ascanio Gabriel , Ruiz-Huerta Leopoldo , Aguayo Juan P.
Published: May 2021

An analytic approximation for the flow of a linear Phan-Thien–Tanner model fluid through an axisymmetric semi-hyperbolic contraction is presented. Such an approximation allows us to compute velocity and pressure response for the flow through axisymmetric contraction geometries; in particular, we have considered here the semi-hyperbolic contraction, which is a geometry where an almost constant extension-rate is reached at different radial positions. In addition, we present a semi-analytic solution capable of representing the exponential version of the selected viscoelastic model; this solution was compared to the results of commercial software, demonstrating the excellent approximation level of the semi-analytic model proposed. Alternatively, for both approaches (linear and exponential Phan-Thien–Tanner), the flow model equations are solved by considering the Navier boundary condition, which allows these models to represent flows with some degree of slip at the geometry wall.
Phase stability of colloidal mixtures of spheres and rods
Authors: Opdam J. , Guu D. , Schelling M. P. M. , Aarts D. G. A. L. , Tuinier R. , Lettinga M. P.
Published: May 2021

We determined the phase boundaries of aqueous mixtures containing colloidal rod-like fd-viruses and polystyrene spheres using diffusing-wave spectroscopy and compared the results with free volume theory predictions. Excluded volume interactions in mixtures of colloidal rods and spheres lead to mediated depletion interactions. The strength and range of this attractive interaction depend on the concentrations of the particles, the length L and diameter D of the rods, and the radius R of the spheres. At strong enough attraction, this depletion interaction leads to phase separation. We experimentally determined the rod and sphere concentrations where these phase transitions occur by systematically varying the size ratios L/R and D/R and the aspect ratio L/D. This was done by using spheres with different radii and modifying the effective diameter of the rods through either the ionic strength of the buffer or anchoring a polymeric brush to the surface of the rods. The observed phase transitions were from a binary fluid to a colloidal gas/liquid phase coexistence that occurred already at very low concentrations due to the depletion efficiency of highly anisotropic rods. The experimentally measured phase transitions were compared to phase boundaries obtained using free volume theory (FVT), a well established theory for calculating the phase behavior of colloidal particles mixed with depletants. We find good correspondence between the experimental phase transitions and the theoretical FVT model where the excluded volume of the rod-like depletants was explicitly accounted for in both the reservoir and the system.
Poiseuille–Rayleigh–Bénard instability of a channel flow with uniform cross-flow and thermal slip
Authors: Khan Mohamin B M , Sani Muhammad , Ghosh Sukhendu , Behera Harekrushna
Published: May 2021

Stability characteristics of a pressure-driven Poiseuille type flow are explored in a horizontal channel with porous walls. The flow is modified with a thermal gradient, and the temperature slips alongside a uniform cross-flow for three different configurations: (i) the flow having heat influx/outflux and temperature jump across the channel walls with internal heat generation in the fluid, (ii) the flow with constant wall temperatures (not necessarily equal) and no internal heat source, and (iii) the flow having a temperature jump/slip at the upper wall and lower wall with a constant temperature. The Reynolds, Péclet, and Rayleigh numbers govern the behavior of the thermal and velocity profiles along with the physical aspects of the flow. The modified Orr–Sommerfeld and energy equations are derived for the perturbed system by the normal mode analysis and solved using the Chebyshev collocation method, while the energy budget analysis is used to further illustrate the stability characteristics of the system. The resulting eigenvalues and eigenfunctions are used to analyze the growth rate characteristics, neutral stability ranges, velocity isolines, and temperature isotherms for each flow configuration. Further, the energy from various sources is calculated by making use of eigenfunctions corresponding to the unstable eigenmodes. An increase in the Rayleigh and Reynolds numbers promotes the flow instability; whereas, a higher cross-flow Reynolds number suppresses the instability by raising the upward cross-flow. The porous walls, characterized by the velocity slip and wall shear, inhibit the Poiseuille–Rayleigh–Bénard instability of the system. The higher temperature difference/lower wall temperature and the stronger thermal slip, respectively, destabilize and stabilize the flow. Conclusively, the flow instability varies depending on the configuration.
Propagation of wave packets along intensive simple waves
Authors: Kamchatnov A. M. , Shaykin D. V.
Published: May 2021

We consider propagation of high-frequency wave packets along a smooth evolving background flow whose evolution is described by a simple-wave type of solutions of hydrodynamic equations. In geometrical optics approximation, the motion of the wave packet obeys the Hamilton equations with the dispersion law playing the role of the Hamiltonian. This Hamiltonian depends also on the amplitude of the background flow obeying the Hopf-like equation for the simple wave. The combined system of Hamilton and Hopf equations can be reduced to a single ordinary differential equation whose solution determines the value of the background amplitude at the location of the wave packet. This approach extends the results obtained in the paper by Congy et al. [J. Fluid Mech. 875, 1145 (2019)] for the rarefaction background flow to arbitrary simple-wave type background flows. The theory is illustrated by its application to waves obeying the KdV equation.
Prediction of the effects of rf irradiation on the I–V curves of a CDW compound
Authors: Nikonov S. A. , Zybtsev S. G. , Maizlakh A. A. , Pokrovskii V. Ya.
Published: May 2021

The Shapiro steps (ShSs) developing in sliding charge-density wave (CDW) under rf irradiation are considered in terms of the CDW travel in the periodic (washboard) potential. We demonstrate that treating the CDW as an inertialess object whose velocity is defined by the instantaneous voltage one can predict the positions of the ShSs in dc voltages for the given amplitude of rf voltage. Moreover, the approximation allows indicating the rf voltages at which the ShSs' magnitudes show maxima and minima. The only information necessary in advance is the I–V characteristic without rf irradiation and the cross-sectional area of the sample. Thus, one can recover the course of an I–V curve in average and the positions of ShSs on it, though not their forms.
F-cluster: Reaction-induced spin correlation in multi-radical systems
Authors: Kattnig Daniel R.
Published: May 2021

We provide a theoretical analysis of spin-selective recombination processes in clusters of n ≥ 3 radicals. Specifically, we discuss how spin correlation can ensue from random encounters of n radicals, i.e., “F-clusters” as a generalization of radical F-pairs, acting as precursors of spin-driven magnetic field effects. Survival probabilities and the spin correlation of the surviving radical population, as well as transients, are evaluated by expanding the spin density operator in an operator basis that is closed under application of the Haberkorn recombination operator and singlet–triplet dephasing. For the primary spin cluster, the steady-state density operator is found to be independent of the details of the recombination network, provided that it is irreducible; pairs of surviving radicals are triplet-polarized independent of whether they are actually reacting with each other. The steady state is independent of the singlet–triplet dephasing, but the kinetics and the population of sister clusters of smaller size can depend on the degree of dephasing. We also analyze reaction-induced singlet–triplet interconversion in radical pairs due to radical scavenging by initially uncorrelated radicals (“chemical Zeno effect”). We generalize previous treatments for radical triads by discussing the effect of spin-selective recombination in the original pair and extending the analysis to four radicals, i.e., radical pairs interacting with two radical scavengers.
Multiple trans-Torres Strait colonisations by tree frogs in the
Authors: Oliver Paul M. , Rittmeyer Eric N. , Torkkola Janne , Donnellan Stephen C. , Dahl Chris , Richards Stephen J.
Published: May 2021

Australia and New Guinea (together referred to as Sahul) were linked by land for much of the late Tertiary and share many biotic elements. However, New Guinea is dominated by rainforest, and northern Australia by savannah. Resolving patterns of biotic interchange between these two regions is critical to understanding the expansion and contraction of both habitat types. The green tree frog (Litoria caerulea) has a vast range across northern and eastern Australia and New Guinea. An assessment of mitochondrial and morphological diversity in this nominal taxon in New Guinea reveals two taxa. True Litoria caerulea occurs in disjunct savannahs of the Trans-Fly, Central Province and across northern Australia, with very low genetic divergence, implying late Pleistocene connectivity. A previously unrecognised taxon is endemic to New Guinea and widespread in lowland swampy rainforest. Date estimates for the divergence of the new species suggest Pliocene connectivity across lowland tropical habitats of northern Australia and New Guinea. In contrast, the new species shows shallow phylogeographic structuring across the central mountains of New Guinea, implying recent dispersal between the northern and southern lowlands. These results emphasise that the extent and connectivity of lowland rainforest and savannah environments across northern Australia and southern New Guinea have undergone profound shifts since the late Pliocene. http://zoobank.org/urn:lsid:zoobank.org:pub:A577A415-0B71-4663-B4C1-7271B97298CD
Laser-induced transient magnons in Sr
3
Ir
2
O
7
throughout the Brillouin zone
Authors: Mazzone Daniel G. , Meyers Derek , Cao Yue , Vale James G. , Dashwood Cameron D. , Shi Youguo , James Andrew J. A. , Robinson Neil J. , Lin Jiaqi , Thampy Vivek , Tanaka Yoshikazu , Johnson Allan S. , Miao Hu , Wang Ruitang , Assefa Tadesse A. , Kim Jungho , Casa Diego , Mankowsky Roman , Zhu Diling , Alonso-Mori Roberto , Song Sanghoon , Yavas Hasan , Katayama Tetsuo , Yabashi Makina , Kubota Yuya , Owada Shigeki , Liu Jian , Yang Junji , Konik Robert M. , Robinson Ian K. , Hill John P. , McMorrow Desmond F. , Först Michael , Wall Simon , Liu Xuerong , Dean Mark P. M.
Published: May 2021

Significance

Ultrafast manipulation of magnetic states holds great promise for progress in our understanding of new quantum states and technical applications, but our current knowledge of transient magnetism is very limited. Our work elucidates the nature of transient magnetism in gapped antiferromagnets using

S
r

3

I
r

2

O

7

as a model material. We find that transient magnetic fluctuations are trapped throughout the entire Brillouin zone while remaining present beyond the time that is required to restore the original spin network. The results are interpreted in the context of a spin-bottleneck effect, in which the existence of an explicit magnetic decay channel allows for an efficient thermalization of transient spin waves.
Taking regulatory T cells into medicine
Authors: Sakaguchi Shimon
Published: May 2021

Regulatory T cells (Tregs) are indispensable for the establishment and maintenance of immunological self-tolerance. Their genetic anomalies or variations in function are causative of various monogenic and polygenic autoimmune diseases. Treg-based reestablishment of self-tolerance is envisioned to cure autoimmune diseases in the clinic.
Non-adiabatic ionization with tailored laser pulses
Authors: Azizi Sajad , Saalmann Ulf , Rost Jan M
Published: May 2021

Non-adiabatic photo-ionization is difficult to control as it relies on the derivatives of the envelope and not on phase-details of the short ionizing pulse. Here, we introduce a catalyzing state, whose presence render non-adiabatic ionization sensitive to phase-details of tailored pulses. Since a catalyzing state is in general easy to create, this opens a perspective for coherent control of ultra-fast ionization.
Principal component analysis of diffuse magnetic neutron scattering: a theoretical study
Authors: Twyman Robert , Gibson Stuart J , Molony James , Quintanilla Jorge
Published: May 2021

We present a theoretical study of the potential of principal component (PC) analysis to analyse magnetic diffuse neutron scattering data on quantum materials. To address this question, we simulate the scattering function

S

q

for a model describing a cluster magnet with anisotropic spin–spin interactions under different conditions of applied field and temperature. We find high dimensionality reduction and that the algorithm can be trained with surprisingly small numbers of simulated observations. Subsequently, observations can be projected onto the reduced-dimensionality space defined by the learnt PCs. Constant-field temperature scans correspond to trajectories in this space which show characteristic bifurcations at the critical fields corresponding to ground-state phase boundaries. Such plots allow the ground-state phase diagram to be accurately determined from finite-temperature measurements.
Performance of a low gain avalanche detector in a medical linac and characterisation of the beam profile
Authors: Isidori T , McCavana P , McClean B , McNulty R , Minafra N , Raab N , Rock L , Royon C
Published: May 2021

Low gain avalanche detectors can measure charged particle fluences with high speed and spatial precision, and are a promising technology for radiation monitoring and dosimetry. A detector has been tested in a medical linac where single particles were observed with a time resolution of 50 ps. The integrated response is similar to a standard ionising chamber but with a spatial precision twenty times finer, and a temporal precision over 100 million times better, with the capability to measure the charge deposited by a single linac pulse. The unprecedented resolving power allows the structure of the ∼3 μs linac pulses to be viewed and the 350 ps sub-pulses in the train to be observed.
Non-Hermitian topological phases and dynamical quantum phase transitions: a generic connection
Authors: Zhou Longwen , Du Qianqian
Published: May 2021

The dynamical and topological properties of non-Hermitian systems have attracted great attention in recent years. In this work, we establish an intrinsic connection between two classes of intriguing phenomena—topological phases and dynamical quantum phase transitions (DQPTs)—in non-Hermitian systems. Focusing on one-dimensional models with chiral symmetry, we find DQPTs following the quench from a trivial to a non-Hermitian topological phase. Moreover, the critical momenta and critical time of the DQPTs are found to be directly related to the topological invariants of the non-Hermitian system. We further demonstrate our theory in three prototypical non-Hermitian lattice models, the lossy Kitaev chain (LKC), the LKC with next-nearest-neighbor hoppings, and the nonreciprocal Su–Schrieffer–Heeger model. Finally, we suggest a proposal to experimentally verify the found connection by a nitrogen-vacancy center in diamond.
Faraday rotations, ellipticity, and circular dichroism in magneto-optical spectrum of moiré superlattices*
Authors: Crosse J A , Moon Pilkyung
Published: May 2021

We study the magneto-optical conductivity of a number of van der Waals heterostructures, namely, twisted bilayer graphene, AB–AB and AB–BA stacked twisted double bilayer graphene and monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride. As the magnetic field increases, the absorption spectrum exhibits a self-similar recursive pattern reflecting the fractal nature of the energy spectrum. Whilst twisted bilayer graphene displays only weak circular dichroism, the other four structures display strong circular dichroism with monolayer graphene and AB-stacked bilayer graphene on hexagonal boron nitride being particularly pronounced owing to strong inversion symmetry breaking properties of the hexagonal boron nitride layer. As the left and right circularly polarized light interact with these structures differently, plane-polarized incident light undergoes a Faraday rotation and gains an ellipticity when transmitted. The size of the respective angles is on the order of a degree.
Lattice plasmon mode excitation via near-field coupling
Authors: Lin Yun , Shen Shuo , Gao Xiang , Wang Liancheng
Published: May 2021

The optical response of metal nanoparticles can be modified through near-field or far-field interaction, yet the lattice plasmon modes (LPMs) considered can only be excited from the latter. Here instead, we present a theoretical evaluation for LPM excitation via the near-field coupling process. The sample is an arrayed structure with specific units composed of upper metal disks, a lower metal hole and a sandwiched dielectric post. The excitation process and underlying mechanism of the LPM and the influence of the structure parameters on the optical properties have been investigated in detail by using a finite-difference time-domain (FDTD) numerical method. Our investigation presented here should advance the understanding of near-field interaction of plasmon modes for LPM excitation, and LPMs could find some potential applications, such as in near-field optical microscopes, biosensors, optical filters and plasmonic lasers.
Comparison of resonant tunneling diodes grown on freestanding GaN substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy*
Authors: Zhou Xiang-Peng , Qiu Hai-Bing , Yang Wen-Xian , Lu Shu-Long , Zhang Xue , Jin Shan , Li Xue-Fei , Bian Li-Feng , Qin Hua
Published: May 2021

AlN/GaN resonant tunneling diodes (RTDs) were grown separately on freestanding GaN (FS-GaN) substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy (PA-MBE). Room temperature negative differential resistance (NDR) was obtained under forward bias for the RTDs grown on FS-GaN substrates, with the peak current densities (J
p) of 175–700 kA/cm2 and peak-to-valley current ratios (PVCRs) of 1.01–1.21. Two resonant peaks were also observed for some RTDs at room temperature. The effects of two types of substrates on epitaxy quality and device performance of GaN-based RTDs were firstly investigated systematically, showing that lower dislocation densities, flatter surface morphology, and steeper heterogeneous interfaces were the key factors to achieving NDR for RTDs.
Pressure- and temperature-dependent luminescence from Tm3+ ions doped in GdYTaO4
Authors: Zhou Peng-Yu , Dou Xiu-Ming , Sun Bao-Quan , Dou Ren-Qin , Zhang Qing-Li , Liu Bao , Hou Pu-Geng , Chi Kai-Lin , Ding Kun
Published: May 2021

Luminescent properties of Tm3+-doped GdYTaO4 are studied for exploring their potential applications in temperature and pressure sensing. Two main emission peaks from 3H4 → 3H6 transition of Tm3+ are investigated. Intensity ratio between the two peaks evolves exponentially with temperature and has a highest sensitivity of 0.014 K−1 at 32 K. The energy difference between the two peaks increases linearly with pressure increasing at a rate of 0.38 meV/GPa. Intensity ratio between the two peaks and their emission lifetimes are also analyzed for discussing the pressure-induced variation of the sample structure. Moreover, Raman spectra recorded under high pressures indicate an isostructural phase transition of GdYTaO4 occurring at 4.46 GPa.
Implant- and anesthesia-related factors affecting cardiopulmonary threshold intensities for vagus nerve stimulation
Authors: Ahmed Umair , Chang Yao-Chuan , Lopez Maria F , Wong Jason , Datta-Chaudhuri Timir , Rieth Loren , Al-Abed Yousef , Zanos Stavros
Published: May 2021

Objective. Vagus nerve stimulation (VNS) is typically delivered at increasing stimulus intensity until a neurological or physiological response is observed (‘threshold’) for dose calibration, preclinically and therapeutically. Factors affecting VNS thresholds have not been studied systematically. In a rodent model of VNS we measured neural and physiological responses to increasing VNS intensity, determined neurological and physiological thresholds and examined the effect of implant- and anesthesia-related factors on thresholds. Approach. In acute and chronic vagus implants (45 and 20 rats, respectively) VNS was delivered under isoflurane, ketamine-xylazine, or awake conditions. Evoked compound action potentials (CAPs) were recorded and activation of different fiber types was extracted. Elicited physiological responses were registered, including changes in heart rate (HR), breathing rate (BR), and blood pressure (BP). CAP and physiological thresholds were determined. Main results. The threshold for evoking discernable CAPs (>10 µV) (CAP threshold) is significantly lower than what elicits 5%–10% drop in heart rate (heart rate threshold, HRT) (25 µA ± 1.8 vs. 80 µA ± 5.1, respectively; mean ± SEM). Changes in BP and small changes in BR (bradypnea) occur at lowest intensities (70 µA ± 8.3), followed by HR changes (80 µA ± 5.1) and finally significant changes in BR (apnea) (310 μA ± 32.5). HRT and electrode impedance are correlated in chronic (Pearson correlation r= 0.47; p< 0.001) but not in acute implants (r = −0.34; p NS); HRT and impedance both increase with implant age (r= 0.44; p< 0.001 and r = 0.64; p < 0.001, respectively). HRT is lowest when animals are awake (200 µA ± 35.5), followed by ketamine-xylazine (640 µA ± 151.5), and isoflurane (1000 µA ± 139.5). The sequence of physiological responses with increasing VNS intensity is the same in anesthetized and awake animals. Pulsing frequency affects physiological responses but not CAPs. Significance. Implant age, electrode impedance, and type of anesthesia affect VNS thresholds and should be accounted for when calibrating stimulation dose.
Augmentation on CNNs for Handwritten Digit Classification in a Small Training Sample Size Situation
Authors: Mitani Y , Fujita Y , Hamamoto Y
Published: May 2021

In general, a deep learning needs a lot of samples. However, in a practical pattern recognition problem, the number of training samples is usually limited. We investigate the effect of an image data augmentation by a perspective transformation on a convolution neural network(CNN) for handwritten digit classification in a small training sample size situation. The experimental results show the effectiveness of the image data augmentation by the perspective transformation on the CNN for handwritten digit classification particularly in the small training sample size situation.
Can new mobile technologies enable fugitive methane reductions from the oil and gas industry?
Authors: Fox Thomas A , Hugenholtz Chris H , Barchyn Thomas E , Gough Tyler R , Gao Mozhou , Staples Marshall
Published: May 2021

New mobile platforms such as vehicles, drones, aircraft, and satellites have emerged to help identify and reduce fugitive methane emissions from the oil and gas sector. When deployed as part of leak detection and repair (LDAR) programs, most of these technologies use multi-visit LDAR (MVL), which consists of four steps: (a) rapidly screen all facilities, (b) triage by emission rate, (c) follow-up with close-range methods at the highest-emitting sites, and (d) conduct repairs. The proposed value of MVL is to identify large leaks soon after they arise. Whether MVL offers an improvement over traditional single-visit LDAR (SVL), which relies on undirected close-range surveys, remains poorly understood. We use the Leak Detection and Repair Simulator (LDAR-Sim) to examine the performance and cost-effectiveness of MVL relative to SVL. Results suggest that facility-scale MVL programs can achieve fugitive emission reductions equivalent to SVL, but that improved cost-effectiveness is not guaranteed. Under a best-case scenario, we find that screening must cost < USD 100 per site for MVL to achieve 30% cost reductions relative to SVL. In scenarios with non-target vented emissions and screening quantification uncertainty, triaging errors force excessive close-range follow-up to achieve emissions reduction equivalence. The viability of MVL as a cost-effective alternative to SVL for reducing fugitive methane emissions hinges on accurate triaging after the screening phase.