bluuebunny/crossref_metadata_2025 huggingface dataset:
Pronostic chirurgical lors de syndrome hémorragique jéjunal chez la vache laitière en ferme : 58 cas (2013-2024)
Authors: Guélou Kévin , Boucon Mathieu , Liron Marie
Published: December 2024

Première cause d’obstruction digestive chez le bovin dans notre clientèle rurale, le syndrome hémorragique jéjunal (SHJ) a fait l’objet de nombreuses études rétrospectives.

L’objet de cet article est d’apporter des éléments épidémiologiques de la maladie et de rapporter les résultats obtenus en condition de terrain, après massage des anses intestinales lésées, à court (8 jours après intervention), moyen (entre 30 jours et 6 mois) et long termes (au-delà de 12 mois). Les données relatives aux animaux opérés ont été recueillies après examen des ordonnances, consultation de la base de données BDIVET, ou après interrogation de l’éleveur. Seules les vaches debout, opérées, par taxis de l’anse lésée, ont été retenues dans cette étude.

Entre septembre 2023 et octobre 2024, 58 vaches, de race Montbéliarde exclusivement, issues de 42 cheptels, ont été opérées avec ce mode opératoire. L’âge moyen des vaches malades était de 4,8 ans. Le rang de lactation moyen des animaux malades était en moyenne de 2,6 lactations. Le nombre moyen de jours en lactation était de 134 jours.

Le délai entre l’apparition des signes et l’intervention chirurgicale était compris entre 0 et 4 jours. La chirurgie intervenait en moyenne 12 à 24 heures après la découverte des premiers signes cliniques (moyenne 0,7 jour). Cinq animaux sont morts le jour suivant la chirurgie (8,5 %), pour un taux de survie à 8 jours estimé à 67,2 % (39/58). À 30 jours, il était de 62 % (36/58) alors que 39,3 % des vaches étaient encore vivantes 6 mois après la chirurgie, et 32 % un an plus tard (16/50). Le délai d’intervention n’a pas été un facteur contributif des taux de survie, quel que soit le terme (p < 0.05).

Les limites principales de cette étude tiennent au manque d’analyse des conditions pré- et peropératoires, lié à la qualité rétrospective de l’enquête. Il pourrait être intéressant d’y ajouter ce point d’étude pour améliorer la prise en charge du SHJ en ferme, avec une chirurgie plus facile à réaliser que l’entérectomie. Néanmoins, le nombre élevé de cas, exclusivement en race Montbéliarde, le contexte de terrain et les paramètres étudiés (taux de survie à moyen et long terme) la rendent originale.
An Amphiphilic Pentaaryl Cyclopentadienyl Ruthenium(II) Molecular Rotor with a Luminescent Tag
Authors: Rapenne Gwénaël , Nishino Toshio , Ohno Yorie , Ishihara Mika , Nishikawa Yoshiko , Martin Colin J. , Yasuhara Kazuma
Published: December 2024

This study presents a chemically modified molecular motor designed for interactions with lipid bilayers. By incorporating long alkyl chains into the anchoring fragment and a rhodamine luminescent tag onto the rotating subunit, we aimed to monitor the position of the motor and to permit its real-time visualization during membrane-perforation experiments. The synthesis of the functionalized tripodal ligand involved a seven-step process, culminating in the formation of a piano-stool Ru(II) complex that exhibits distinctive spectroscopic properties. The luminescence of the rhodamine tag, although slightly quenched upon incorporation in the Ru(II) complex, remains sufficiently strong to permit single-molecule observation using a total-internal-reflection fluorescence microscope.
Some features of the low-frequency branches of the vibration spectrum and the low-temperature heat capacity of spiral structures
Authors: Telezhenko Yu. V. , Sukharevskii B. Ya.
Published: December 2024

We propose a method of calculating low-frequency branches of the vibration spectra in polymers and biopolymers. We carry out a comparison analysis of low-frequency spectral characteristics and low-temperature heat capacities of discrete spirals of various types in terms of a simple model consisting of monatomic discrete spirals. We consider the physical causes which give rise to the linear dependence and conformation sensitivity of the low-temperature heat capacity of high-molecular-weight compounds
Dynamics of librational motion in N2-type crystals. I. Self-consistent-field theory and the harmonic approximation
Authors: Antsygina T. N. , Slyusarev V. A. , Freiman Yu. A. , Érenburg A. I.
Published: December 2024

Two approaches are proposed to describe a system of interacting rotors. The version developed of the self-consistent-field approximation, explicitly including simplifications related to the quasi-oscillatory nature of molecular motion in the orientationally ordered phase, makes it possible to consider anharmonic effects. The dynamics of the librational subsystem in the harmonic approximation make it possible to describe correlation effects, but completely neglect anharmonicity. The relations derived are used as a basis for a theory combining the advantages of both approaches mentioned.
Point-contact spectroscopy in copper: temperature measurements. Dependence of point-contact spectra on contact parameters
Authors: Akimenko A. I. , Verkin A. B. , Ponomarenko N. M. , Yanson I. K.
Published: December 2024

Measurements of the temperature dependence of the point-contact resistance R(T) are used to determine the effective contact size d and the mean free path li of an electron in the neighborhood of the contact. The dependence of the parameters of point-contact spectra on li and d is studied. The experimental results are compared with the predictions of a theoretical model for reabsorption of nonequilibrium phonons. This allows the temperature of the nonequilibrium phonons to be estimated (near the L peak the temperature is about 70–80 °K). The observed dependence R(T) ∼T4 for 20 < T <40°K is explained by single-phonon Umklapp processes, which make the greatest contribution to the point-contact spectrum of copper.
X ray diffraction investigation of the thermal expansion of CsDy(MoO4)2
Authors: El’chaninova S. D. , Zvyagin A. I. , Kazei Z. A.
Published: December 2024

We have studied the temperature dependence of the thermal expansion coefficient of CsDy(MoO4)2 in the temperature range 30–300 °K. A sharp anomaly in the anisotropy of the thermal expansion coefficient, characteristic of layered crystals, is found. It is established that in the vicinity of the phase transition there is a large negative peak in the coefficient α100 and a much smaller positive peak in α0l0.
The Kondo effect in states with nonlocalized spin in compounds with intermediate valence
Authors: Karnaukhov I. N.
Published: December 2024

Within the framework of the Anderson Hamiltonian we consider an electron–phonon interaction describing the change in the overlap integral of the wave functions of s and f electrons during the deformation of the lattice. It is shown that consideration of the electron–phonon interaction in substances with intermediate valence leads to the Kondo effect. We calculate the single-particle Green’s function for s electrons and determine the Kondo temperature.
Impedance of a nonequilibrium tunnel junction with a nonuniform order parameter
Authors: Levchenko E. B.
Published: December 2024

It is shown that a superconducting tunnel junction with a nonuniform order parameter has an intrinsic resonant frequency, and that by measuring this as a function of current one can investigate transitions between nonuniform states in nonequilibrium superconductors during tunneling injection of quasiparticles.
Energy gap of superconducting Nb–Ga alloys
Authors: Dzhuraev D. R. , Levchenko I. S. , Motulevich G. P.
Published: December 2024

The superconducting energy gaps Δ of Nb–Ga alloy films are measured by the method of electron tunneling, and their R (T) dependences are studied. The geometry of the sputtering permitted obtaining specimens with a gradient in the composition that resulted in spatial inhomogeneity of the film. A structure of “domain” type was hence formed, in which different sections of the film possessed different gaps and different temperature ranges for the superconducting transition. This was observed both in tunneling experiments in which a number of gaps was observed, and in the function R (T) which was multistep in nature. It turned out to be possible to compare the gap magnitudes with their corresponding Tc. The dependence of Δ on Tc turned out to be approximately linear. The maximum is Δ = 3.71 MeV. The ratio 2Δ/kTc is a monotonically increasing function; however, its growth slows down as Tc increases, indicating a tendency to saturation. For specimens with low Tc the ratio 2Δ/kTc is smaller than the theoretical value (BCS). For Tc ∼ 13−15 °K it equals the theoretical value, and for Tc > 15 °K it is higher than the theoretical value.
Transition from a normal to a superconducting state observed on heating in an amorphous bismuth–hydrogen system
Authors: Belevtsev B. I. , Komnik Yu. F. , Odnokozov V. I. , Fomin A. V.
Published: December 2024

We report a study of the electrical and superconducting properties of bismuth films obtained by condensation in a hydrogen atmosphere (at pressure PH2 in the range 5 · 10−6 to 2 · 10−5 Torr) onto a substrate cooled by liquid helium. The dissolved hydrogen leads to a significant increase in the resistivity, a lowering of Tc, and an increase in the temperature of the transformation from the amorphous phase to the crystal line. If PH2 exceeds some critical value, then the films obtained take the form of a strongly hydrogen saturated metastable phase a-Bi (H). This phase transforms around 5 °K to the usual amorphous bismuth phase, which is also metastable. At this transition, the resistivity falls sharply (by two orders of magnitude) and the value of Tc is elevated (the change approaches 2 °K). In many cases this process appears as a sharp transition on heating from a resistive to a superconducting state.
The observation of coherent magnetic breakdown in aluminum from features of the temperature dependence of the magnetoresistance
Authors: Morgun V. N. , Slutskin A. A. , Khotkevich V. I.
Published: December 2024

It is shown that in the case of magnetic breakdown (MB) a temperature dependence for the magnetoresistance of a metal of the form p ∼ T−3 is a reliable indicator of quantum coherence of the MB.
Thermal conductivity of niobium–titanium alloys in the mixed state
Authors: Herzog R. , Khukhareva I. S.
Published: December 2024

The behavior of the thermal conductivity in the mixed state has been investigated experimentally in niobium–titanium alloys. The measurements were conducted in magnetic fields of up to 7 T on the alloy Nb45Ti55, which has been the highest critical field in this system, and on Nb80T20, which has a substantially lower critical field. The Nb45T55 specimen was measured in the cold-worked and recrystallized (annealed at 1000 °C for 1 h) states. It has been established that the thermal conductivity in the mixed state depends markedly on the concentration of the alloys and the structure of the defects. The results are compared with the theory which Caroli and Cyrot1 developed for dirty alloys in the direct proximity of the upper critical field.
Symmetry analysis of the static and high-frequency properties of CuCI2 • 2H2O and CuCl2 • 2D2O
Authors: Pashkevich Yu. G. , Sobolev V. L. , Telepa V. T.
Published: December 2024

We consider the ground states, antiferromagnetic resonance frequencies, and dynamic susceptibilities of CuCl2•2H2O and CuCl2 • 2D2O in terms of a four-sublattice model taking into account the Dzyaloshinskii interaction. We treat the case of a field H||Ox for T = 0. We show that for the two lowest AFMR branches the use of a four-sublattice model leads to the same results as in the two-sublattice model. We have studied the exchange branches of the spectrum as a function of magnetic field and we discuss the possibility of observing them in IR absorption spectra.
Microcontact spectroscopy of dilute magnetic alloys CuMn and CuFe
Authors: Naĭdyuk Yu. G. , Shklyarevskiĭ O. I. , Yanson I. K.
Published: December 2024

The method of microcontact spectroscopy is used to study alloys with magnetic impurities CuMn and CuFe in the range of concentrations 0.01–1 at.%. Minima or maxima (so-called zero anomalies) were observed in the microcontact spectra of these alloys at voltages ∼ 1 mV. The Landé g-factor for the Mn impurity in a Cu matrix was determined from the splitting of the minimum of the zero anomaly in a magnetic field. The quantitative calculations carried out agree well with theory and permit determining both the important geometric contact parameter ⟨K(v ,v ’)⟩, i.e., the averaged geometric form factor, and the characteristics of the alloy itself, for example, J/εF, i.e., the ratio of the magnitude of the exchange interaction energy between an electron and the magnetic impurity to the Fermi energy, from the microcontact spectra.
Properties of bismuth under conditions of elastic wave generation (Review)
Authors: Bogod Yu. A.
Published: December 2024

Effects that arise with supersonic drift of mobile charge carriers under the action of external fields are discussed: amplification of sound, generation of acoustic noise, nonlinearity of current–voltage characteristics (CVC), and excitation of electrical oscillations. In particular, the characteristics of amplification and generation in an isotropic medium, quantum oscillations of CVC parameters of bismuth under generation conditions, the nonreciprocity effect, and negative differential resistance are examined. It is suggested that the mechanism of stabilization of nonequilibrium phonons and the relation between the dimensions of the specimen and the phonon–electron free path, which explains the properties of the dynamic CVC, are interrelated.
On the nature of the maximum of the longitudinal magnetoresistance in thin films of bismuth and bismuth–antimony alloys
Authors: Andrievskii V. V. , Butenko A. V. , Komnik Yu. F. , Nikitin Yu. V.
Published: December 2024

The behavior of the maximum in the longitudinal magnetoresistance in bismuth and Bi-Sb alloy thin films with changes in the thickness and alloy composition has been studied. It is proposed that the decrease in the film resistance in a strong magnetic field occurs basically due to the growth in the carrier concentration upon reaching the ultraquantum field region. The position of the maximum of the longitudinal magnetoresistance does not depend on L for sufficiently great film thicknesses (with L ≳3000–4000 Å for Bi and with L ≳ 6000–8000 Å for Bi0.963Sb0.037 alloys). With a lower thickness the field at the maximum increases due to the change in the parameters of the spectrum and the growth of the carrier concentration. A dependence of the form Hmax3/2∼1/L agrees well with the proposed explanation of the nature of the maximum of the longitudinal magnetoresistance.
Variation of the direction of the easy magnetization axis with temperature in monoclinic magnetically ordered systems
Authors: Borisenko V. G. , Pereverzev Yu. V.
Published: December 2024

We consider the magnetic properties of ferromagnets and antiferromagnets which have an interaction of monoclinic symmetry. It is shown that this type of interaction leads to temperature dependence in the orientation of the easy magnetization axis. We obtain analytical expressions for this dependence in the low temperature region.
Conduction bands of crystalline neon
Authors: Zarochentsev E. V. , Tolpygo K. B. , Troitskaya E. P.
Published: December 2024

The OPW method is used to calculate the conduction bands of neon from the first principles. The matrix elements of the pseudopotential are obtained by exact evaluation of the exchange term and the Phillips–Kleinmann potential, using the electron functions of an isolated atom for the calculation of the Wannier functions. The band structure is very similar to that calculated by other methods which involve the expansion of the basis in plane waves, and agrees well with the available experimental data.
Numerical modeling of phase transition in a system of parametrically excited spin waves
Authors: Bakai A. S. , Panasenko A. M. , Sergeeva G. G.
Published: December 2024

The system of differential equations of motion describing parametrically excited spin waves in magnetic materials at various temperatures is solved numerically. It is shown that at low temperatures, close to zero, in a system with spontaneous symmetry breaking a symmetrical distribution of spin waves is unstable, and a singular distribution is established. With an increase in the temperature the symmetry of the distribution is restored. The reported numerical experiment can be used to determine the presence of a phase transition in the investigated system and to explain the essential details of that transition near the critical temperature.
Fine structure of the spectrum of self-trapped luminescence of neon
Authors: Grigorashchenko O. N. , Rybalko Yu. I. , Savchenko E. V. , Fugol’ I. Ya.
Published: December 2024

Fine structure in the spectrum of self-trapped states in crystalline neon has been discovered. It is shown that the spectrum of the “hot” quasimolecular luminescence is produced by transitions from several vibrationally excited states. There is a significant difference between the single-centered quasiatomic states trapped within the specimen and in the surface layer.
Exciton migration in crystals of antiferromagnetic manganese compounds
Authors: Matyushkin É. V. , Smushkov V. I.
Published: December 2024

The luminescence and excitation spectra of antiferromagnetic RbMnCl3 and CsMnCl3 crystals are investigated. Exciton autolocalization has been found. The nature of exciton motion in antiferromagnetic CsMnF3, NaMnCl3, RbMnCl3, and CsMnCl3 crystals is compared. It is shown that the interaction of an exciton with lattice vibrations exerts a decisive influence on the electron excitation energy transport process.
Kinetics of vacancions in solid He4
Authors: Kal’noi S. E. , Strzhemechnyi M. A.
Published: December 2024

A semiquantitative calculation of the cross sections for interaction of vacancions in solid He4 with different lattice defects is performed. Estimates are obtained for the coefficient of diffusion of vacancions. A macroscopic equation describing the kinetics of vacancions, including the possibility of their creation and absorption, is formulated. The contribution of vacancions to thermal conductivity is calculated.
The influence of the proximity effect in the electrodes on the stationary properties of S−N−S Josephson structures
Authors: Kupriyanov M. Yu. , Lukichev V. F.
Published: December 2024

The influence of the proximity effect in the superconducting electrodes on the critical current of thin SNS sandwiches has been studied within the framework of the microscopic theory of superconductivity. It has been shown that Ic depends substantially on the parameter γ=σNξs∗/σsξN∗ and coincides in order of magnitude with the current I0, calculated without considering the suppression of superconductivity in the electrodes, only for γ < 0.1. For low resistance (γ ≫ 1) and high-resistance (γ ≪ 1) N layers analytical expressions are found which determine the critical current of an SNS sandwich as a function of the temperature and the parameter γ. The function I0(T, γ) is calculated for arbitrary T and γ and graphs are given which allow one to determine simply the degree of suppression of Ic due to the proximity effect.
Influence of aging on the pinning of magnetic flux vortices and dislocations in lead–cadmium alloys
Authors: Dotsenko V. I.
Published: December 2024

The influence of the quantity and morphology of the normal phase on the mechanical and superconducting properties of lead– cadmium alloys is investigated. The influence of aging on the magnitude of the yield point and the hysteresis of the magnetization curves of a lead—3.3 wt.% cadmium alloy, as well as directionally and volume crystallized eutectic alloys of this same system, is investigated.
Low temperature specific heat of strongly anisotropic crystals
Authors: Syrkin E. S. , Feodos’ev S. B.
Published: December 2024

Using a Jacobian matrix method for a particular microscopic model of a crystal we have analyzed the variation of the low temperature specific heat as a function of the ratio of the interlayer and intralayer interactions.
Charge complexes in helium films
Authors: Monarkha Yu. P.
Published: December 2024

The effects of the interaction of positive ions with surface electrons (SE) in a superfluid helium film are theoretically investigated. The possibility of using the Coulomb crystallization of positive ions to produce a surface-electron band spectrum is investigated. It is shown that the electron-ion coupling is weak (i.e., the bands are broad) in the case of high positive-ion concentrations and strong (i.e., the bands are narrow) in the case of low concentrations. The dynamics of the dipolar crystal in a helium film is investigated in the strong-coupling limit and in the case when the number of electrons is equal to the number of ions, and the melting point of the crystal is determined. The surface-excitation spectrum of a helium film electrified by dipolar quasiparticles is computed. It is shown that the stability of the film strongly depends on the phase state (liquid or crystalline) of the dipolar system. The possibility of the existence of complex charge lattices in a helium film with concentrations of positive and negative charges that are multiples of each other are analyzed.
Critical currents in columnar vanadium films
Authors: Cherkasova V. G. , Kolin’ko A. E. , Slatin A. E. , Fogel’ N. Ya.
Published: December 2024

The angular dependence of the critical current Ic is studied in columnar vanadium films. In measurements in constant magnetic fields an anomalous maximum Ic is found on the Ic(θ) curves at arbitrary values of the external magnetic field and temperature, when the magnetic field is perpendicular to the plane of the specimen. The angular dependence of Ic measured in constant reduced magnetic fields h = H/Hc2(T, θ) shows no singularities in the vicinity of the angle at which the Ic peak is found in the case H = const, i.e., the critical current is isotropic. This implies that a change in the relative orientation of the vortices and column boundaries produces no change in critical current. The experimental data obtained permit the conclusion that the anisotropy of Ic observed in a constant magnetic field H is merely a consequence of the anisotropy of the critical magnetic field Hc—the critical current “tracks” the magnitude and angular dependence of Hc.
Investigation of the nature of the excess magnetization of europium
Authors: Bezverkhii P. P. , Blinov A. G. , Dikovskii V. Ya. , Kuskova N. V.
Published: December 2024

The magnetization of polycrystalline metallic europium is investigated in the temperature range 4.2–270 °K and in magnetic fields up to 30 kOe. It is shown experimentally that the excess magnetization, responsible for the quasiferromagnetic behavior of europium at low temperatures, is due to gaseous impurities, primarily hydrogen. Hydrogen concentrations in two europium specimens are determined using the method of vacuum melting. The values obtained are close to the computed concentrations, necessary to explain the observed excess magnetization by cluster ferromagnetism of europium dihydride.
Coupling molecular and continuum numerical methods for evaluation of thermal and mechanical drives on high rotating isotopic gas flow
Authors: Ebrahimgol H. , Aghaie Moghanloo M. , Zolfaghari A.
Published: December 2024

The main objective of this study is to develop a hybrid molecular–continuum method to model a gas flow within a centrifuge machine. By implementation of this coupled approach, the effects of mechanical and thermal drives on gas flow and separation process inside a high rotating cylinder are evaluated. In simulating the gas flow inside the high rotating cylinder, there are certain situations where the particle density experiences significant fluctuations. To accurately simulate these events, the direct simulation Monte Carlo (DSMC) approach can be employed as the most effective particle method. However, obtaining a high level of accuracy with this method necessitates a significant amount of computation time. Alternatively, the less time-consuming computational approach, known as fluid technique or computational fluid dynamics (CFD), can be utilized when the flow is in the state of continuum. The goal of coupled DSMC–CFD solution is to integrate particle and fluid simulations to speed up calculation for transitional flows that involve both fields in a unified domain. The DSMC–CFD method is implemented in the OpenFOAM framework to simulate the flow of UF6 gas throughout the regions of a centrifuge machine. This open-source software offers the capability to solve the molecular region and code the coupling between the continuum and molecular regions. This work introduces a modified code based on OpenFOAM to simulate the gas flow in the supersonic rotating cylinder, which provides both molecular and fluid areas. This simulation is conducted under axisymmetric and steady-state to analyze the impact of thermal and mechanical drivers on flow regimes. Also, the isotopic separation and separative work are evaluated.
Testing the validity of the Wiedemann–Franz law for metals and alloys at high pressures
Authors: Hsieh Wen-Pin , Lin Chung-Hung , Chen Chao-Chih , Chang Jen-Wei
Published: December 2024

The Wiedemann–Franz (WF) law is a fundamental, empirical law that originally relates the electronic thermal conductivity (Λe) of a metal to its electrical resistivity (ρ) via the Lorenz number L = ρΛe/T, where T is the absolute temperature. Conventionally as ρ is measured or calculated, it has often been used to infer the Λe through the WF law at a wide range of pressure (P)–temperature (T) conditions. However, since the WF law was originally formulated based on a simple electron gas model with L being approximately the Sommerfeld value L0 = 2.44 × 10−8 W Ω K−2, its validity to transition metals involving correlated d-orbital electrons at a variety of P-T conditions has been questioned, not to mention to metallic alloys. Here, we report experimental measurements on the thermal conductivity and electrical resistivity of platinum (Pt), iron (Fe), as well as Fe0.85Si0.15 and FeS alloys at high pressures and room temperature. We demonstrate that the L of Pt and Fe both reasonably agree with L0 from ambient to ∼60 GPa, except for Fe around the pressures where a structural transition (∼12 GPa) and an electronic topological transition (∼30–40 GPa) occur. The L of Fe0.85Si0.15 and FeS alloys, however, both considerably deviate from L0, presumably due to significant inelastic scatterings between carriers and impurities. Our results suggest that using the WF law with ideal L0 to convert ρ of metallic alloys to Λe (and vice versa) at high pressures could lead to a large discrepancy from that obtained by direct measurements.
Origin of added parameters in laminar flow around oscillating submerged plates through force decomposition
Authors: Bahrami Mohammad Amin , Cervantes Michel J. , Raisee Mehrdad , Nourbakhsh Ahmad
Published: December 2024

This study investigates the physical mechanisms behind added mass and added damping during the transverse oscillation of a two-dimensional (2D) plate in a quiescent fluid. Added mass and added damping are defined as the components of the force in-phase and out-of-phase with the solid's acceleration, respectively. To achieve this goal, the force between the fluid and the solid is decomposed into physically meaningful components, establishing a direct link between the phenomena responsible for force generation and the added parameters. The study reveals that the added damping is solely dependent on vortex-induced and viscous forces, while added mass is predominantly influenced by inertia but also exhibits a significant contribution from vortex-induced and viscous forces. The results show that dimensionless frequency (β) significantly influences added mass and added damping at low frequencies, with its impact decreasing as frequency increases. Additionally, added damping increases as the plate thickness ratio decreases, primarily due to the enhancement of the vortex-induced force mechanism. Reducing the thickness ratio (Δ) from Δ = 0.04 to Δ = 0.01 results in an increase in the damping coefficient by up to 60% within the intermediate range of the Keulegan–Carpenter (KC) number studied.
Energy optimization design for the driving source for rock fragmentation by high-voltage pulsed discharge (RHPD)
Authors: Liao Hongbin , Liu Yi , Zhao Yong , Cheng Jin , Huang Shijie , Xu Youlai , Lin Fuchang
Published: December 2024

The energy parameter of the driving source for rock fragmentation by high-voltage pulsed discharge (RHPD) determines the effectiveness of rock fragmentation. The mapping relationship between the energy parameter of the RHPD driving source and the stress parameter is established, and an energy optimization design criterion for the RHPD driving source is proposed. The time-varying impedance of the plasma channel is simulated, and the spatial and temporal distribution of stress within the rock under the channel pressure loading is analyzed. A rock fragmentation criterion based on the stress impulse criterion is proposed, and a nonlinear constrained mathematical model for the energy optimization design for the RHPD driving source is developed. Using the existing driving source and load parameters as examples, the feasibility and accuracy of the proposed energy optimization design criterion for the RHPD driving source are verified, which provides theoretical guidance for the design of the RHPD driving source.
Atomistic insights into liquid crystals of board-like molecules via molecular dynamics simulation
Authors: Díaz-Acosta Adrián , Adroher-Benítez Irene , Zerón Iván M. , Patti Alessandro
Published: December 2024

As the temperature decreases, rigid anisotropic molecules that usually incorporate polar groups, aromatic rings or multiple bonds, orient along a common direction, eventually forming liquid-crystalline phases under specific thermodynamic conditions. This study explores the phase behavior and dynamics of board-shaped mesogens with a 1,4,5,8-tetraphenyl-anthraquinone core and four lateral arms forming an oligo(phenyleneethynylene) scaffold. These molecules are promising candidates for forming the elusive biaxial nematic phase. Through atomistic molecular dynamics simulations, we observe the formation of nematic and smectic liquid crystals, in qualitative agreement with experimental observations. To characterize the structure, we compute pair correlation functions along relevant symmetry directions and the nematic order parameter, which indicate a dominant uniaxial ordering with very weak biaxiality. In addition, we analyze the dynamics of our board-shaped mesogens along and perpendicular to the nematic director, revealing an intriguing non-Gaussian behavior and dynamical heterogeneities, with coexisting slow and fast molecules. Building on our recent simulations at the colloidal scale, which demonstrated that monodisperse board-like particles are unable to form biaxial nematics while polydisperse particles can, we hypothesize that a similar behavior may occur at the molecular scale in mixtures of molecules. Although pure-component molecular systems reveal weak biaxiality, our findings suggest that investigating mixtures of the most promising candidates, those molecules that form nematic or smectic phases, could uncover conditions conducive to the formation of biaxial nematic liquid crystals.
Large-scale and very-large-scale motions in a moderate-Reynolds-number turbulent boundary layer over a flat plate towed in a tank
Authors: Yu Lei , Bai Honglei , Zhang Weiguo , Peng Junjie , Shi Zheyu
Published: December 2024

An experimental work is conducted to investigate large-scale motions (LSMs) and very-large-scale motions (VLSMs) of a turbulent boundary layer generated by a flat plate towed in a tank. Reynolds number based on friction velocity and boundary layer thickness covers a range of 1200 ≤Reτ≤ 3100. The streamwise–wall-normal plane and the streamwise–spanwise plane are separately measured using time-resolved stereoscopic particle image velocimetry (TR-SPIV) and time-resolved planar PIV (TR-PIV), respectively. The large-scale coherent structures in the two orthogonal planes are identified by the clustering method. Based on spatiotemporal evolutions of instantaneous flow fields, it is observed that low- and high-speed coherent structures collide and lean against each other, generating a strong shear layer between them. The low-speed coherent structures move away from the wall, while the high-speed coherent structures travel toward the wall near the interaction regions during the shearing, which may lead to merging and splitting of the coherent structures. The coherent structures grow in streamwise scales by self-stretching and coalescence with adjacent coherent structures. The properties of the LSMs and VLSMs, including scales, inclination angles, meandering behaviors, and contributions of high- or low-speed VLSMs to skin friction, are quantitatively examined. Furthermore, the dynamic characteristics of the LSMs and VLSMs are classified into merging, splitting, growing, and shortening, with occurrence frequencies independent of Reynolds number. Effects of shearing on the merging and splitting events are discussed. Results from this work suggest that the primary formation mechanism of the VLSMs is the self-growing of LSMs vigorously stretching along the streamwise direction.
Susceptibility formulation of density matrix perturbation theory
Authors: Niklasson Anders M. N. , Habib Adela , Finkelstein Joshua D. , Rubensson Emanuel H.
Published: December 2024

Density matrix perturbation theory based on recursive Fermi-operator expansions provides a computationally efficient framework for time-independent response calculations in quantum chemistry and materials science. From a perturbation in the Hamiltonian, we can calculate the first-order perturbation in the density matrix, which then gives us the linear response in the expectation values for some chosen set of observables. We present an alternative, dual formulation, where we instead calculate the static susceptibility of an observable, which then gives us the linear response in the expectation values for any number of different Hamiltonian perturbations. We show how the calculation of the susceptibility can be performed with the same expansion schemes used in recursive density matrix perturbation theory, including generalizations to fractional occupation numbers and self-consistent linear response calculations, i.e., similar to density functional perturbation theory. As with recursive density matrix perturbation theory, the dual susceptibility formulation is well suited for numerically thresholded sparse matrix algebra, which has linear scaling complexity for sufficiently large sparse systems. Similarly, the recursive computation of the susceptibility also seamlessly integrates with the computational framework of deep neural networks used in artificial intelligence (AI) applications. This integration enables the calculation of quantum response properties that can leverage cutting-edge AI-hardware, such as NVIDIA Tensor Cores or Google Tensor Processing Units. We demonstrate performance for recursive susceptibility calculations using NVIDIA Graphics Processing Units and Tensor Cores.
Electric polarization induced by low magnetic field in the W-type hexaferrite BaCoFe17O27 single crystal
Authors: Tang Yongsen , Zheng Shuhan , Weng Yakui , Zhang Anlei , Zhang Yalin , Zhou Shuang , Li Xing'ao
Published: December 2024

Recently, the noncollinear magnetic structure with varying Co/Zn ratios was reported in the W-type hexaferrites using neutron powder diffraction. It is believed that these noncollinear spin orderings may stimulate magnetoelectric (ME) effect in the W-type hexaferrite. Herein, we present distinct evidence of ME response through systematic investigation on the magnetic and ferroelectric properties in BaCoFe17O27. Magnetization exhibits two different anomalies at TC1 ∼ 350 K and TC2 ∼ 150 K, indicating the formation of long-range longitudinal spin configurations and the spin reorientation transition, respectively. We have found that the low field-driven electric polarization has been observed under the ME poling condition of E ⊥ (H ⊥ c, and c). Spin current mechanism is mainly considered as the physics origin in its ME response, corresponding to the other hexaferrites as reported early. In addition, the weak electric polarization observed with E(⊥c)//H(⊥c) suggests that the p–d hybridization mechanism should also be contributed to the ME response in this compound. Therefore, BaCoFe17O27 presents an intrinsic magnetoelectric effect and provides a thought for people to seek and study the more single-phase ME compounds from the viewpoint of foundational and applications.
Mapping driven oscillations in the size of a bubble to the dynamics of a Newtonian particle in a potential
Authors: Shimon Uri , Stern Ady
Published: December 2024

The non-linear dynamics of driven oscillations in the size of a spherical bubble are mapped to the dynamics of a Newtonian particle in a potential within the incompressible liquid regime. The compressible liquid regime, which is important during the bubble's sonic collapse, is approached adiabatically. This new framework naturally distinguishes between the two time scales involved in the non-linear oscillations of a bubble. It also explains the experimentally observed sharp rebound of the bubble upon collapse. Guided by this new vantage point, we develop analytical approximations for several key aspects of bubble motion. First, we formulate a tensile strength law that integrates the bubble's ideal gas behavior with a general polytropic index. Next, we establish a straightforward physical criterion for Bjerknes force reversal, governed by the driving pressure, ambient pressure, and tensile strength. Finally, we derive an acoustic energy dissipation formula for the bubble's sonic collapse, dependent solely on the bubble's collapse radii and velocity.
Experimental investigation on transition mechanisms and modal decomposition analysis of gas–liquid flow patterns in horizontal–vertical elbow
Authors: Han Fenghui , Lan Qingyuan , Ong Muk Chen , Yin Guang , Li Wenhua
Published: December 2024

A series of experiments are conducted to investigate the transition mechanisms and characteristics of six typical gas–liquid flow patterns in a horizontal–vertical elbow using electrical capacitance tomography and high-speed camera. The dominant modes and corresponding time coefficients are obtained by performing proper orthogonal decomposition on the pulsating gas holdup (GHU) distribution data to explore their physical mechanisms and correlations. Reduced-order descriptions for different flow patterns are discussed. The results show that after passing through the elbow, the horizontal slug or bubble flow turns into vertical bubble flow due to the small gas volume content and the mixing effect of secondary flow, accompanied by a swirl-switching phenomenon. A slug flow forms at the elbow outlet when there is a stratified flow comes from the horizontal pipe, and changes in flow conditions will affect the generation frequency and stability of Taylor bubbles. The horizontal annular or mist flow with high gas volume content will be transformed into churn flow in the vertical pipe. The modal decomposition analysis indicates that, for all the investigated conditions in the present study, mode 1 represents the mean distribution of GHU fluctuations, and there is a pair of modes representing the dominant swirling features. For the slug and churn flows, mode 2 characterizes the features of gas slug or large bubbles, the time coefficient of which is highly connected with that of mode 1. Meanwhile, it is also shown that the obtained low-dimensional descriptions of different flow patterns using the dominant modes are able to reconstruct most of the GHU distribution features in gas–liquid flows with the reconstructive loss less than 3%.
Wake effect on floating offshore wind turbine fatigue load
Authors: Kang Yujoo , Lee Sang
Published: December 2024

Wind turbines submerged in the upstream wind turbine (UWT) wake lead to reduced power production and increased fatigue loads. However, current wind farm layout optimization processes prioritize power production without addressing fatigue load due to the complexities associated with fatigue load assessment within the UWT wake. In this study, the impacts of wake-turbine overlap on the fatigue load for floating offshore wind turbines are investigated. A large-eddy simulation is used to generate the UWT wake, followed by extensive aeroelastic simulations to meticulously examine the wake-turbine overlap effect over the wake domain. The blade fatigue load results reveal significant influences on the degree of wake-turbine overlap. Blade fatigue load correlates with wake deficit and turbulence, exhibiting a bimodal distribution in the lateral direction with peaks at approximately 0.5 turbine diameter (D) offset while diminishing in the streamwise direction. Despite the complete recovery of power production at 1D lateral offset, a significant fatigue load persists. Furthermore, tower fatigue load and platform motions are notably affected by the degree of wake-turbine overlap and the wave. These findings underscore the importance of incorporating fatigue load analysis into the wind farm layout optimization process to extend the turbine lifespan and reduce operation and maintenance costs.
Detection of spin current generated by the acoustic spin–rotation coupling mechanism via acoustic voltage
Authors: Mi Shuai , Zhao Chenbo , Liu Meihong , Wang Jianbo , Liu Qingfang
Published: December 2024

The method of combining surface acoustic waves (SAWs) with electrical detection has promoted the study of phonon–spin coupling and spintronics. Aiming at problems of difficult detection of DC voltage and unknown origin of spin current caused by SAW in ferromagnetic/light metal systems, we constructed the Ni/Cu/Ta on LiNbO3 substrate and measured acoustic voltages directly, which are used to analyze the spin current induced by SAW. By analyzing the angular dependence of acoustic voltages and estimating the maximum spin current, it is determined that acoustic voltages originate from the acoustic spin–rotation (ASR) coupling and the acoustic spin pumping (ASP) effects. The angular dependence shows that for the longitudinal voltage, the contribution of ASR to ASP is in the ratio of 3.22/3.77, while the transverse voltage is mainly contributed by the ASR. The maximum spin current due to ASR is 0.97 × 105 A/m2, while that due to ASP is 1.47 × 105 A/m2. This work provides ideas for the design of phonon–spin coupled devices.
Dynamics of drop impact and contact line motion on micro-pillared surfaces
Authors: Dwivedi Raghvendra Kumar , Muralidhar K.
Published: December 2024

Physical texturing creates patterned and pillared surfaces that display superhydrophobicity in drop spreading and drop impact studies. Often, such surfaces are accompanied by large hysteresis since the three-phase contact line may get trapped over and within the pillars. In this context, wetting characteristics of a water drop spreading over a micro-pillared surface of copper are investigated. Apart from drop spreading on a bare pillared surface, two companion studies where the pillars are fully and partially coated using superhydrophobic and hydrophobic coatings have been carried out. The Weber number and Reynolds number based on the drop diameter and impact speed are varied over the range 1–41 and 440–2870, respectively, while the Bond number remains constant, ∼1.03. Imaging sequences show spreading behavior that is distinctive of the surface chosen. For a fully coated surface, the drop is seen to jump-off upon impact while a residual drop remains over uncoated and partially coated pillars during the receding phase. These observations are compared against three-dimensional numerical simulations that resolve the pillar shapes. Simulations are seen to be qualitatively in good agreement with experiments. Simulations additionally probe the contact line movement over coated and uncoated pillars for comparison with experiments. The filling of the interpillar space with liquid and the resulting interface deformation are examined. Jointly, the emptying of the interpillar gap is also discussed. Experiments and simulation show a jump in drop footprint when the contact line leaves the pillar, and the associated velocity becomes large.
Insights into fractal space features in nonlinear electrohydrodynamic Rayleigh–Taylor instability of viscous fluids
Authors: El-Dib Yusry O.
Published: December 2024

This paper describes a unique method for detecting and evaluating nonlinear Rayleigh–Taylor instability (RTI) in electro-viscous fluids exposed to an external vertical electric field. The governing equations are based on a linearized Navier–Stokes framework with nonlinear boundary conditions, capturing the system's complexity. Using a traveling wave transformation, the analysis reduces the system's complicated dynamics to a nonlinear characteristic equation in the elevation function that includes quadratic and cubic nonlinearities. The strategy utilizes El-Dib's frequency formula, which allows for the derivation of an equivalent linearized form of the characteristic equation, simplifying the nonlinear equation and making it more tractable for analytical investigation. The study emphasizes the critical function of the electric field in the system's stability. Smaller electric fields improve stability and equilibrium, resulting in damped oscillations that maintain the fluid–fluid interface. Larger electric fields, on the other hand, enhance instabilities, causing the system to behave nonlinearly, which might lead to chaotic motion if the oscillations are severe. The analysis is extended to convert the characteristic equation into a fractal space description. The fractal derivative form enables the modeling and study of complicated, nonlinear, and chaotic processes commonly encountered in fluid dynamics problems. This methodology is especially well-suited to handling multi-scale dynamics and nonlinear growth in RTI. The influence of fractal factors on system behavior is examined. Increasing the fractal order consistently has a stabilizing effect, lowering the oscillation amplitude and increasing damping, hence improving stability. In contrast, raising the fractalness parameter introduces a destabilizing influence, resulting in bigger oscillations and lower damping, destabilizing the system over time. This study sheds light on the behavior of nonlinear RTI in electro-viscous fluids in the presence of electric fields and fractal dynamics.
Discrete state model of a self-aggregating colloidal system with directional interactions
Authors: Navas Salman Fariz , Klapp Sabine H. L.
Published: December 2024

The construction of coarse-grained descriptions of a system’s kinetics is well established in biophysics. One prominent example is Markov state models in protein folding dynamics. In this paper, we develop a coarse-grained, discrete state model of a self-aggregating colloidal particle system inspired by the concepts of Markov state modeling. The specific self-aggregating system studied here involves field-responsive colloidal particles in orthogonal electric and magnetic fields. Starting from particle-resolved (Brownian dynamics) simulations, we define the discrete states by categorizing each particle according to its local structure. We then describe the kinetics between these states as a series of stochastic, memoryless jumps. In contrast to other works on colloidal self-assembly, our coarse-grained approach describes the simultaneous formation and evolution of multiple aggregates from single particles. Our discrete model also takes into account the changes in transition dynamics between the discrete states as the size of the largest cluster grows. We validate the coarse-grained model by comparing the predicted population fraction in each of the discrete states with those calculated directly from the particle-resolved simulations as a function of the largest cluster size. We then predict population fractions in the presence of noise-averaging and in a situation where a model parameter is changed instantaneously after a certain time. Finally, we explore the validity of the detailed balance condition in the various stages of aggregation.