Vector Potential Research Articles

Fully Microscopic Treatment of Magnetic Field Using Bogoliubov–De Gennes Approach

This work introduces an algorithm designed to solve the Bogoliubov–de Gennes equations of superconductivity theory. What sets this algorithm apart is its remarkable ability to precisely and consistently consider the impact of an external magnetic field, all within the microscopic approach. The computation scheme’s convergence is guaranteed by addressing the Biot–Savart equation for the field where the vector potential appears on both of its sides. To showcase the capabilities of this approach, we provide several key examples: the Abrikosov lattice, vortex core states, and the vortex structure in the intermediate mixed state of a superconductor. This method promises to offer valuable insights into the microscopic physics of intertype superconductivity.

Behavior of spin-0 scalar particles in Eddington-inspired Born–Infeld gravity global monopole with harmonic oscillator potential

In this paper, we investigate the behavior of a scalar bosonic field within the backdrop of Eddington-inspired Born–Infeld gravity with a global monopole configuration. Additionally, we consider the presence of both scalar and vector potentials. To introduce the scalar potential, we perform a transformation on the mass term, replacing [Formula: see text] with [Formula: see text]. For the vector potential, we apply a minimal coupling scheme, transforming [Formula: see text] within the relativistic Klein–Gordon equation. We opt for a harmonic oscillator scenario where the scalar and vector potentials are equal, i.e. [Formula: see text]. Through this setup, we analytically solve the wave equation using the confluent Heun equation form. Subsequently, we delve into the quantum system in the absence of any potential, determining the permissible values for bound-state relativistic energy levels and the scalar field’s wave function. Our analysis reveals that the energy levels and wave function are influenced by various parameters present in the eigenvalue expression.

Error analysis of the linearized Crank-Nicolson FEM for the incompressible vector potential magnetohydrodynamic system

A linearized fully discrete Crank-Nicolson finite element scheme is proposed for solving the three-dimensional incompressible magnetohydrodynamic equations based on a magnetic vector potential formulation, where the magnetic induction is written to a rotation of magnetic vector potential. By using the MINI element and lowest order Nédélec edge element to approximate the velocity field and pressure of fluid and magnetic vector potential, respectively, the numerical solution of magnetic induction can preserve the exactly divergence-free condition in fully discrete level. Error estimates for the velocity field and magnetic vector potential are rigorously analyzed under some reasonable regularity assumptions of exact solution. Finally, numerical results are given to support the theoretical analysis.

Exchange energies with forces in density-functional theory.

We propose exchanging the energy functionals in ground-state density-functional theory with physically equivalent exact force expressions as a new promising route toward approximations to the exchange-correlation potential and energy. In analogy to the usual energy-based procedure, we split the force difference between the interacting and auxiliary Kohn-Sham system into a Hartree, an exchange, and a correlation force. The corresponding scalar potential is obtained by solving a Poisson equation, while an additional transverse part of the force yields a vector potential. These vector potentials obey an exact constraint between the exchange and correlation contribution and can further be related to the atomic shell structure. Numerically, the force-based local-exchange potential and the corresponding exchange energy compare well with the numerically more involved optimized effective potential method. Overall, the force-based method has several benefits when compared to the usual energy-based approach and opens a route toward numerically inexpensive nonlocal and (in the time-dependent case) nonadiabatic approximations.

Design of protein-binding peptides with controlled binding affinity: the case of SARS-CoV-2 receptor binding domain and angiotensin-converting enzyme 2 derived peptides.

The development of methods able to modulate the binding affinity between proteins and peptides is of paramount biotechnological interest in view of a vast range of applications that imply designed polypeptides capable to impair or favour Protein-Protein Interactions. Here, we applied a peptide design algorithm based on shape complementarity optimization and electrostatic compatibility and provided the first experimental in vitro proof of the efficacy of the design algorithm. Focusing on the interaction between the SARS-CoV-2 Spike Receptor-Binding Domain (RBD) and the human angiotensin-converting enzyme 2 (ACE2) receptor, we extracted a 23-residues long peptide that structurally mimics the major interacting portion of the ACE2 receptor and designed in silico five mutants of such a peptide with a modulated affinity. Remarkably, experimental KD measurements, conducted using biolayer interferometry, matched the in silico predictions. Moreover, we investigated the molecular determinants that govern the variation in binding affinity through molecular dynamics simulation, by identifying the mechanisms driving the different values of binding affinity at a single residue level. Finally, the peptide sequence with the highest affinity, in comparison with the wild type peptide, was expressed as a fusion protein with human H ferritin (HFt) 24-mer. Solution measurements performed on the latter constructs confirmed that peptides still exhibited the expected trend, thereby enhancing their efficacy in RBD binding. Altogether, these results indicate the high potentiality of this general method in developing potent high-affinity vectors for hindering/enhancing protein-protein associations.

Noncommutativity in Configuration Space Induced by a Conjugate Magnetic Field in Phase Space

An external magnetic field in configuration space coupled to quantum dynamics induces noncommutativity in its velocity momentum space. By phase space duality, an external vector potential in the conjugate momentum sector of the system induces noncommutativity in its configuration space. Such a rationale for noncommutativity is explored herein for an arbitrary configuration space of Euclidean geometry. Ordinary quantum mechanics with a commutative configuration space is revisited first. Through the introduction of an arbitrary positive definite ∗-product, a one-to-one correspondence between the Hilbert space of abstract quantum states and that of the enveloping algebra of the position quantum operators is identified. A parallel discussion is then presented when configuration space is noncommutative, and thoroughly analysed when the conjugate magnetic field is momentum independent and nondegenerate. Once again the space of quantum states may be identified with the enveloping algebra of the noncommutative position quantum operators. Furthermore, when the positive definite ∗-product is adapted to the conjugate magnetic field, the coordinate operators span a Fock algebra of which the coherent states are the analogues of the structureless points in a commutative configuration space. These results generalise and justify a posteriori within ordinary canonical quantisation the heuristic approach to quantum mechanics in the noncommutative Euclidean plane as constructed and developed by F. G. Scholtz and his collaborators.

A description of the sources of magnetic field using edge values of the current vector potential

A description of the sources of magnetic field using edge values of the current vector potential

Emergence of symmetric and asymmetric Dirac points under periodic electric and vector potentials in ABA-trilayer graphene superlattice.

We have theoretically investigated the impact of both periodic electric and vector potentials on the low energy spectrum of ABA-trilayer graphene superlattice. Finite energy Dirac points appear in the energy spectrum due to the application of the vector potential. These extra Dirac points are symmetric about k y = 0 plane for equal barrier and well widths. For different barriers and well widths, one Dirac point shifts away and the second Dirac point shifts towards the k y = 0 plane. The extra Dirac points are not only generated from the original Dirac point but also emerge from the valleys developed in the energy spectrum. The application of both electric and vector potentials with identical barrier and well widths breaks the symmetry of the spectrum about the Fermi level. When the electric and vector potentials are asymmetric with all three layers having the same electric potentials, the energy spectrum becomes asymmetric about the Fermi level, and this asymmetric behavior of both potentials annihilates the original Dirac point from the spectrum. When all the layers have different electric potentials and both electric and vector potentials are asymmetric, the spectrum becomes asymmetric again, but this time the asymmetry of the spectrum occurs across the k y = 0 plane.

Structure of ectoparasite communities of Nyctalus species (Chiroptera: Vespertilionidae) in the Zhiguli State Nature Reserve and Samarskaya Luka National Park (European Russia)

The ectoparasites of the bats (Chiroptera) often act as carriers of infectious agents dangerous to animals and humans. This determines the relevance of studying ectoparasite communities. In this regard, the composition of communities and interspecific relations of ectoparasites of migratory bats are of particular interest, since they can be a source of arthropods with vector potential that are atypical in a studied area. This research was aimed to study the species composition, community structure and parasite-host specificity of ectoparasites in syntopic populations of bats of the genus Nyctalus. The study has been carried out in the Zhiguli State Biosphere Reserve and Samarskaya Luka National Park (Russia). A total of 78 individuals of Nyctalus were examined, namely Nyctalus noctula (47 individuals), N. leisleri (21 individuals) and N. lasiopterus (ten individuals). They were captured by ornithological nets in the summer period in 2017–2019. The collected ectoparasites were fixed in alcohol, and permanent preparations were made using Fora-Berlese liquid. In total, we found 19 ectoparasite species, namely one Hemiptera species (Cimex lectularius), four Ischnopsyllidae species, and 14 species of Spinturnicidae and Macronyssidae families. Of these, eight ectoparasite species have been found for the first time in Russia on Nyctalus species. Nine ectoparasites species were found on Nyctalus leisleri, 15 species on N. noctula, and 11 species on N. lasiopterus. The most massive and widespread parasite on Nyctalus is Macronyssus flavus. In addition, we demonstrated a high infestation of Nyctalus noctula by Spinturnix acuminatus and Steatonyssus noctulus, of Nyctalus lasiopterus by Spinturnix acuminatus and of Nyctalus leisleri by Steatonyssus spinosus. Among casual parasites of Nyctalus, there are Spinturnix helvetiae, S. myoti, S. plecotinus, Ischnopsyllus octactenus, I. variabilis, Macronyssus ellipticus, and Steatonyssus periblepharus. The correspondence analysis of certain ectoparasite communities, differing in qualitative and quantitative composition, with the host species demonstrated the general structure of parasite-host relationships. Nyctalus noctula has the highest diversity of ectoparasite communities and the model of the log-normal distribution of species abundance confirmed this. In terms of species composition, the parasite communities of Nyctalus noctula and N. lasiopterus were the most similar, while the parasite communities of Nyctalus noctula and N. leisleri were the least similar. The key components involved in the differentiation of ectoparasitic communities were the following species: Spinturnix acuminatus, S. kolenatii, Steatonyssus spinosus, and Macronyssus flavus, which have different infestation values in their hosts. Co-occurrence analysis revealed a strong positive relationship for 28 ectoparasite species pairs and a strong negative relationship for 26 species, which may be explained by weakened competitive relations between the ectoparasites. The observed assortativity of parasite species among themselves has been discussed.

Hybrid finite-volume–finite-element scheme for 3D simulation of thermal plasma arc configuration

The plasma dynamics in a three-dimensional free-burning arc configuration are studied using an iterative hybrid finite-volume–finite-element scheme. In this scheme, Navier–Stokes equations are solved with a classical finite volume approach. It is a conservative method that is suitable for solving conservation equations. In addition, a nodal finite element analysis is used to solve Maxwell’s equations for the scalar and vector potentials. The finite-volume and finite-element modules are verified against well-known simple problems. The plasma is considered an incompressible fluid in chemical and thermal equilibrium or local thermodynamic equilibrium. The profiles of fluid and electromagnetic characteristics are depicted for a total current equal to 200 A. The results of this simulation method are in agreement with experimental and numerical predictions.

A model of radiofrequency and plasma coupling for compact ion sources and design

Inductive coupling of radiofrequency power to plasma is a complicate process, since it depends from the density of plasma itself, because ionization is a chain reaction process, and, at low density a capacitive coupling may mix with inductive coupling (with no Faraday screen). Plasma temperature Te , density ne and vector potential are closely coupled, giving nonlinear and singular systems of Partial Differential equations, which require slow iterative solutions, motivating the consideration of a 2D model, also as rapid design and first approximation tool. Plasma conductivity and heating depend on collision rate, which includes also the so-called stochastic collisions (mainly electron collisions with walls), proportionally more important at low gas density ng . Conductivity is also affected by static and radiofrequency magnetic fields; results for skin depth and stochastic collision estimates are reported. The transport of Te and ne inside source can be controlled by a magnetic filter B f . Considering a 5 cm radius H- ion source as example, solution of ne and Te are reported as a function of filter strength B fa, applied rf power and wall status; solver convergence methods andkey plasma observables are briefly discussed. Due to small dimension, a filter strength B fa in the order of 8 mT is needed to achieve electron temperature lower than 2 eV (for negative ion production) at extraction.

Studies on the breeding potential and entomological indices of dengue vectors in urban Chirimiri area District Manendragarh Chirimiri Bharatpur Chhattisgarh

Studies on the breeding potential and entomological indices of dengue vectors in urban Chirimiri area District Manendragarh Chirimiri Bharatpur Chhattisgarh

MVA-based vaccine candidates expressing SARS-CoV-2 prefusion-stabilized spike proteins of the Wuhan, Beta or Omicron BA.1 variants protect transgenic K18-hACE2 mice against Omicron infection and elicit robust and broad specific humoral and cellular immune responses.

Despite the decrease in mortality and morbidity due to SARS-CoV-2 infection, the incidence of infections due to Omicron subvariants of SARS-CoV-2 remains high. The mutations acquired by these subvariants, mainly concentrated in the receptor-binding domain (RBD), have caused a shift in infectivity and transmissibility, leading to a loss of effectiveness of the first authorized COVID-19 vaccines, among other reasons, by neutralizing antibody evasion. Hence, the generation of new vaccine candidates adapted to Omicron subvariants is of special interest in an effort to overcome this immune evasion. Here, an optimized COVID-19 vaccine candidate, termed MVA-S(3P_BA.1), was developed using a modified vaccinia virus Ankara (MVA) vector expressing a full-length prefusion-stabilized SARS-CoV-2 spike (S) protein from the Omicron BA.1 variant. The immunogenicity and efficacy induced by MVA-S(3P_BA.1) were evaluated in mice in a head-to-head comparison with the previously generated vaccine candidates MVA-S(3P) and MVA-S(3Pbeta), which express prefusion-stabilized S proteins from Wuhan strain and Beta variant, respectively, and with a bivalent vaccine candidate composed of a combination of MVA-S(3P) and MVA-S(3P_BA.1). The results showed that all four vaccine candidates elicited, after a single intramuscular dose, protection of transgenic K18-hACE2 mice challenged with SARS-CoV-2 Omicron BA.1, reducing viral loads, histopathological lesions, and levels of proinflammatory cytokines in the lungs. They also elicited anti-S IgG and neutralizing antibodies against various Omicron subvariants, with MVA-S(3P_BA.1) and the bivalent vaccine candidate inducing higher titers. Additionally, an intranasal immunization in C57BL/6 mice with all four vaccine candidates induced systemic and mucosal S-specific CD4+ and CD8+ T-cell and humoral immune responses, and the bivalent vaccine candidate induced broader immune responses, eliciting antibodies against the ancestral Wuhan strain and different Omicron subvariants. These results highlight the use of MVA as a potent and adaptable vaccine vector against new emerging SARS-CoV-2 variants, as well as the promising feature of combining multivalent MVA vaccine candidates.

Shift in virus composition in honeybees (Apis mellifera) following worldwide invasion by the parasitic mite and virus vector Varroa destructor.

Invasive vectors can induce dramatic changes in disease epidemiology. While viral emergence following geographical range expansion of a vector is well known, the influence a vector can have at the level of the host's pathobiome is less well understood. Taking advantage of the formerly heterogeneous spatial distribution of the ectoparasitic mite Varroa destructor that acts as potent virus vector among honeybees Apis mellifera, we investigated the impact of its recent global spread on the viral community of honeybees in a retrospective study of historical samples. We hypothesized that the vector has had an effect on the epidemiology of several bee viruses, potentially altering their transmissibility and/or virulence, and consequently their prevalence, abundance, or both. To test this, we quantified the prevalence and loads of 14 viruses from honeybee samples collected in mite-free and mite-infested populations in four independent geographical regions. The presence of the mite dramatically increased the prevalence and load of deformed wing virus, a cause of unsustainably high colony losses. In addition, several other viruses became more prevalent or were found at higher load in mite-infested areas, including viruses not known to be actively varroa-transmitted, but which may increase opportunistically in varroa-parasitized bees.

Исследование электровихревого течения между плоскостями с помощью различных вычислительных подходов

Electrovortex flows arise when an electric current of varying density passes through a well-conducting fluid (e.g., acid or metal melt). In such a case, the electric current generates a magnetic field, which leads to the Lorentz force causing swirling currents of the medium. There are different methods of theoretical study of such currents. As a rule, to avoid the necessity to find the pressure dependence on coordinates, the variables "vector potential of velocity - swirl" ("scalar current function – swirl" in the case of axisymmetric flows) are used. In such a case, it is quite effective to use automodel variables, which allow to reduce the dimensionality of the problem. In this case, the solution for the introduced function can be sought in the form of an expansion by the electro-vortex flow parameter proportional to the square of the magnetic Reynolds number. Also, this solution can be obtained numerically, for example, using finite-difference methods. Nowadays, more and more often the solutions are investigated by means of direct numerical modeling methods, when no automodel approximations are made, which reduce the accuracy of the solution. Nevertheless, in such a case the number of computations can be quite large and requires the use of supercomputer resources. A separate difficulty is presented by the boundary conditions: for example, for the velocity vector potential we obtain a fourth-order equation, which imposes significant restrictions on the time steps in the evolution equation. The problem can be avoided by using approximate boundary conditions, but this again reduces the accuracy of the solution. In this paper, using the example of electro-vortex flow between planes, the solutions that can be obtained using the various computational approaches mentioned above are examined. The results obtained are compared, and they are also compared with analytical approximations.

Preliminary electromagnetic analysis of the COOL blanket for CFETR

The supercritical CO2 cOoled Lithium-Lead (COOL) blanket has been designed as one advanced blanket candidate for the Chinese Fusion Engineering Test Reactor (CFETR). This work focuses on the electromagnetic (EM) loads (Maxwell force and Lorentz force) acting on the COOL blanket, which are important mechanical loads in further structural analysis of the COOL blanket. A 3D electromagnetic analysis is performed using the ANSYS finite element method to obtain EM loads on the COOL blanket in this study. At first, the magnetic scalar potential (MSP) method is used to obtain the magnetic field and the Maxwell force on the COOL blanket. Then, the magnetic vector potential (MVP) method is performed during a plasma disruption event to get the eddy current distribution. At last, a multi-step method is adopted for the calculation of the Lorentz force and the torque. The maximum Lorentz forces of inboard and outboard blanket structural components are 5624 kN and 2360 kN respectively.

Polar coherent states in bilayer graphene under a constant uniform magnetic field

In this work, the interaction of the electrons in bilayer graphene with a constant, homogeneous magnetic field perpendicular to its surface is analyzed. A symmetric gauge is used for the electromagnetic vector potential, which leads to the use of polar coordinates. The symmetries associated with the Hamiltonian that describes this system are applied to explain some fundamental properties, such as the spectrum and the integer pseudo-spin character of the eigenfunctions. The current densities associated with the bilayer Hamiltonian have been calculated in both Cartesian and polar coordinates showing that they are gauge invariant. Additionally, the appropriate coherent states of this system have been derived as eigenstates of a suitable annihilation operator with complex eigenvalues. The local current densities of these coherent states have been calculated, revealing a type of radial component interference effect that has been overlooked until now. Some of these newly presented results are illustrated graphically.

Experimental verification and electromagnetic analysis of axial flux permanent magnet motor using the subdomain method

This study investigates a subdomain method for performing the characteristic analysis of an axial flux permanent magnet motor (AFPM). Initially, the AFPM was simplified for the analytical model and analysis regions were defined to apply the subdomain method. Subsequently, a general solution was derived for the governing equations of each analysis region using the variable separation method. Subsequently, the undetermined coefficients of the general solution were obtained from the matrix using appropriate boundary conditions, and the magnetic flux density in the air-gap region was derived based on the defined magnetic vector potential. Finally, the induced voltage and electromagnetic torque of the analytical model were calculated. The analytical results were verified using the finite element method and the experimental results.

Over-30-GeV intense laser phase-locked direct electron acceleration

When an intense laser obliquely irradiates a solid, a pre-pulse will first ionize the solid surface, followed by the main pulse interacting with the plasma and ultimately being reflected by the plasma. Simultaneously, certain electrons within the plasma will be trapped in the accelerating phase of the laser field, subsequently gaining effective acceleration within the field, this phenomenon is known as phase-locked electron acceleration. Given the current intense lasers' electric field intensity nearing the TV/m range, electrons could potentially acquire energy levels on the order of hundreds of GeV or even TeV, provided they stay in the accelerating phase of the laser field long enough. Here, we initially use PIC (Particle-in-Cell) simulations to simulate the interaction process between laser pulses and plasma, thereby obtaining the properties of phase-locked electrons. In order to reduce computational demands, we turn to use a three-dimensional (3D) test particle model to calculate the subsequent interactions of these electrons with the reflected laser field. By this model, we obtain the data of the locked-phase electrons after having interacted with the reflected laser (Fig. (a)). Furthermore, we use this model to calculate the dynamical behavior of electrons under different initial conditions (Fig. (b)). Under the laser intensity of <inline-formula><tex-math id="M1">\begin{document}$ {a}_{0}=350 $\end{document}</tex-math></inline-formula>(<inline-formula><tex-math id="M2">\begin{document}$ {a}_{0} $\end{document}</tex-math></inline-formula> is the normalized laser vector potential), the energy of the electrons directly accelerated by the laser is enhanced to 32 GeV. In contrast, under the same laser intensity, the energy of the electrons accelerated by ponderomotive force is only 0.35 GeV. The research findings indicate that the strong laser with peak power around 10 PW can directly accelerate electrons to approximately 30 GeV. Additionally, this study outlines the optimal initial conditions for injecting electrons into the laser field and the final electron energy within the phase-locked acceleration mechanism, thereby establishing a calibration relationship with the laser field intensity. Given the continual enhancement of laser intensity and the potential application of the laser phase-locked electron acceleration mechanism to positron acceleration, this research holds promise for its implementation in fields such as miniaturized positron-electron colliders and high-energy gamma-ray sources.

Stethoscopes as vectors of staphylococci at a veterinary teaching hospital

The issue of nosocomial infections, or healthcare-associated infections (HAIs), remains a significant concern in healthcare settings worldwide. In recent times, there has been growing attention towards medical devices, notably stethoscopes, as potential vectors for pathogen transmission. This study aimed to evaluate the prevalence of Staphylococcal contamination on stethoscopes used by students and staff at Istanbul University-Cerrahpasa Faculty of Veterinary Medicine’s animal hospital. Furthermore, it gathered information about stethoscope usage habits, cleaning practices, handwashing routines, participants' knowledge about nosocomial infections, and their interest in learning more about these infections and stethoscope hygiene. The analysis of 50 stethoscope samples revealed that 27 (54%) were contaminated with one or more Staphylococci. The isolated 30 Staphylococcus spp. included Staphylococcus epidermidis (n=17; 56.7%), Staphylococcus hominis (n=10; 33.3%), Staphylococcus pasteuri (n=1; 3.3%), Staphylococcus capitis (n=1; 3.3%), and Staphylococcus schleiferi (n=1; 3.3%). Notably, the absence of the highly pathogenic Staphylococcus aureus in all samples provides some reassurance. However, the presence of various Staphylococcus spp. raises concerns due to their pathogenic potential. These findings align with previous research on stethoscope contamination, emphasizing the persistent problem of bacterial colonization on these crucial medical devices. Despite variations in bacterial prevalence among studies, Staphylococcus spp. consistently emerge as common contaminants, emphasizing the need for comprehensive stethoscope hygiene protocols in veterinary healthcare settings. To the best of our knowledge, this is the first report describing the vector potential of stethoscopes in a veterinary setting within Turkey. The study suggests the necessity for further research, taking a proactive approach to tackle the challenges of nosocomial infections. This would enable the development of strategies to ensure a safer healthcare environment for patients and healthcare providers.