Vol. 70 No. 5 Sep-Oct (2024): Revista Mexicana de Física

In this letter, we investigate the momentum dispersion in a MoS₂ flake as a function of the thickness in a single crystal with several height steps. The outcomes of our study rely on the utilization of near-field microscopy and an excitation field in the strong-coupling regime. The observed propagating modes have characteristics that are consistent with transverse magnetic (TM) modes, which can be attributed to the investigated thicknesses. Numerical simulations support our experimental findings and correspond with previously reported studies.

The water molecule has many biological functions and is one of the most abundant molecules in the human body. Then, in order to carry out a study of the molecule in physical and chemical phenomena, the model used depends on the phenomenon. For some cases, it is necessary to consider the electronic distribution, while in other cases, it is necessary to consider the protons of the hydrogen atoms, for example, to explain the physics in magnetic resonance imaging. In this work, the water molecule model considered is conformed by three particles: The two nuclei of the hydrogen atom and the oxygen atom negatively double charged and unstructured. The spatial wave function and the interaction of the angular momentum of protons with a constant magnetic field has been studied in a previous work. The present work is a completion, in order to have the complete wave function of this model, considering the spin of the protons, where the energy is degenerated (B = 0). Finally, the interaction of the spin of the nuclei of hydrogen atoms with a magnetic field is studied, representing the case of magnetic resonance imaging, where it is obtained a break in the degeneration of the energy levels, which are in the order of radiofrequency.

Despite decades of research, the Mpemba Effect challenges scientists, prompting further investigation and refinement of existing hypotheses. This work uses optical tools such as thermography to analyze and study the Mpemba effect on drops. We analyze times and contact angle changes with temperature with an easily controlled experiment. This work contributes to the ongoing discourse surrounding the Mpemba Effect, emphasizing the need for interdisciplinary collaboration and experimental rigor to unravel the complexities of this intriguing phenomenon. A deeper understanding of the Mpemba Effect enhances our knowledge of thermodynamics and fluid dynamics and opens avenues for practical applications in fields such as cryopreservation, meteorology, and materials science.

Observed reactor and atmospheric neutrino oscillation mixing values appear to be related to the neutrino scale ratio p ∆m2 sol/∆2 ATM in a way that suggest that the neutrino mass matrix can be expanded as a power series by using this ratio as the smallness parameter. This approach provides a simple and natural way to expose the inner hierarchies among neutrino mass terms, which amounts to also explain the solar oscillation mixing as well as solar oscillation scale. We explore a class of mass matrix textures that realize this scenario, for both normal and inverted neutrino mass hierarchies, as well as CP violation and their stability under renormalization scaling.

This paper addresses the problem of a three-dimensional Klein-Gordon oscillator with position-dependent mass in a non-inertial cosmic string background. We provide solutions to this problem and analyze the eigensolutions, considering the influence of non-inertial effects and the presence of position-dependent mass (PDM) on the eigenvalues. Expressions are obtained for the bound state energies and wave functions.

This work introduces a systematic and efficient approach for producing stable AgNPs utilizing Nigella sativa (Ns) seed aqua extract (AE), which exhibit strong antibacterial properties. The characterization of Ns-AgNPs was performed using a UV-visible spectrophotometer (UV-Vis), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electronic microscopy (SEM), and transmission electronic microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The Ns-AgNPs did not show aggregation, as shown by the results of STEM and XRD. According to the EDX analysis in this research, it was determined that Ns-AgNPs, gave signals in the silver region (~3 KeV) at 92.3%. Ns-AgNPs showed significant antibacterial performance against Staphylococcus aureus, Escherichia coli and were effective at the low concentrations. Ns-AgNPs may be incorporated into wound dressings, surgical instruments, and medical devices to prevent infections and promote healing.

CuO and 3 % Mn-doped CuO nanofibers were synthesized employing the electrospinning method. X-ray diffraction (XRD) verified a monoclinic phase with a C 2/c space group. An electronic density analysis, obtained using Fullprof software, was projected on the (110) and (001) planes for both materials, showing modifications in the Cu positions. This fact generated vacancies involved in the paramagnetism formation in the Mn-doped CuO nanofibers, in contrast to the mixed magnetic phase composed by both ferromagnetic and paramagnetic behaviors found in the undoped CuO. The vacancy amount was quantified by X-ray absorption spectroscopy (XAS) applying CASTEP software. In addition, an analysis from Cu 2p XPS peaks supports the predicted Cu-Cu rearrangement by the Fullprof software study, while the presence of Cu1+ confirms the substitution of Mn for Cu in the doped sample.

This research investigated the optical characteristics of Cd-doped gadolinium oxide (Gd₂O₃) by employing density functional theory (DFT) along with the CASTEP simulation package. After the creation of a Gd₂O₃ supercell at an initial [2x1x1] scale, the study evaluated the altered properties of Gd₂O₃ at the supercell level to assess the impact of Cd-doping on the optical features of doped one. Optical properties which were explored included the examining the dielectric function, refractive index, conductivity, and loss function. The dielectric function exhibited distinct peaks at certain photon energies that corresponded to various electronic transitions between energy levels of the material. The prominent absorption peaks observed in the energy range of 0.174-1.55 eV in the imaginary part of the dielectric function. This was attributed to energy transitions occurring between specific orbitals for pure and Cd-doped gadolinium oxide. The refractive index exhibited stability at lower energy levels, while the conductivity curves displayed excitonic behavior in response to Cd-doping at the supercellular level. Furthermore, the Cd-doping resulted in an increase in absorption, as indicated by the simulated changes in the loss function

The behavior of magnetic nanoparticles covering the surface with positive charges (MN), suspended in a continuous medium, was simulated by Brownian dynamics. Then, we studied the behavior of the MN in an aqueous-like suspension and their adsorption on a negatively charged surface, mimicking a mica surface. After several microseconds, particles are deposited onto the charged surface. Experimental results of ordered magnetic nanoparticles in surfaces are compared with the present simulation results of MN in two dimensions. We also demonstrate the effect of charged MN on the hexagonal structure when electrical repulsions dominate against magnetic dipole-dipole and van der Waals attractions. On one hand, the adsorption of MN on the surface depends on the electrostatic attraction force with the surface, while the surface organization of MN results from balancing electrostatic repulsion forces and magnetic attraction forces among particles. In magnetic nanoparticles simulated with a non-charged surface or weakly charged surface, dipole-dipole interactions dominate the particle-particle interactions, and the interactions between particles and a mica-like surface are conducted by van der Waals forces.

Equivalent local potential with energy-momentum dependence is developed for the combined interaction of Hulthén modified Yamaguchi potential by developing its exact Jost solution. The generated local potentials are applied to compute scattering phase parameters for (p-p) and (p-d) systems through the phase function method (PFM). The same are also calculated for the nonlocal potential from the expression of the Fredholm determinant. Our obtained data for both the energy-momentum dependent local and the pure nonlocal interactions are in reasonable agreement with the standard data. Reasonable correspondence between the results for the phase equivalent and the nonlocal potentials indicate that our equivalent local analysis is in proper order.

In this paper, the improved and modified version of the Sardar sub-equation method (IMSSEM) and the improved generalized Riccati equation mapping method (IGREMM) are manipulated effectively and generously to determine the exact solitary wave soliton solutions of the improved modified KdV (mKdV) equation. The purpose of this study is to provide novel exact solutions to the improved mKdV equation. Specifically, we utilized IMSSEM and IGREMM to study different solutions of the nonlinear improved mKdV equation, focusing on exponential, trigonometric, and trigonometric hyperbolic type solutions. Furthermore, the plotting of various solutions for direct viewing analysis is provided in two and three-dimensional graphs. The new strategies are straightforward, quick, and efficient and have many other advantages, whereas, they provide the most accurate and unique solution to many other types of nonlinear partial differential equations (NPDEs), which usually arise in engineering and applied sciences. It should be noted that these methodologies are novel mathematical instruments that have shown to be the most effective mathematical tools for solving higher-order nonlinear partial differential equations in mathematical physics. Symbolic computation was used to validate all of the solutions that were established. Thus, it is also hoped that these techniques will ultimately reduce the cumbersome workload involved during the process of solutions to complicated NLPDEs.

We experimentally demonstrate a highly temperature-sensitive external Fabry-Perot cavity. The interferometric structure is composed of an air-microcavity; its fabrication uses a microcapillary and UV polymer. A temperature sensitivity close to 5.7 nm/ºC is achieved with suitable linearity (0.9896) and minimal hysteresis; a phase analysis technique is proposed and applied to overcome the trade-off between sensitivity and range of operation. This technique provides a competitive sensitivity (0.84 rad/ºC), good linearity (0.9934), and a range of operation from 25 °C to 41 °C.

The analysis and a mathematical approximation of the dielectric properties of Pouteria sapota (Mamey) pulp compounds in the Terahertz (THz) range are presented. Since THz electromagnetic waves show a high sensitivity to detect water content when interacting with organic materials, this technique was used to determine the effective dielectric function (EDF) of a wet and a dry sample from the THz spectrum data. By fitting the EDF to the Landau-Lifshitz-Looyenga (LLL) dielectric mixture equation, the theoretical dielectric functions of each pulp compounds were approximated. The approach proposed here not only considered dry matter and water content in the Pouteria sapota pulp, as has been reported in the literature for organic samples, but also included the contribution of the volatile components (VC) that allowed a better adjustment to the experimental results. The water and VC content increase the value of the real and imaginary part of the calculated EDF of the wet sample. The use of the non-destructive THz spectroscopy technique allows determining the dielectric properties of fruits that have been dehydrated. Therefore, the methodology proposed here can be used as a method of in situ and ex situ quality control in the agri-food industry.

The microstructure of the interface and inter-diffusion behavior during bonding plays an important role to understand and to control the joining process for better mechanical properties of an interface. In this work, the microstructure of the formed interlayer between cermet WC-Co and metallic Ni after solid state bonding (the WC-Co/Ni interface) was analyzed by scanning (SEM) and transmission (TEM) electron microscopy, and characteristic energy dispersive x-ray spectroscopy (EDS). The WC-Co/Ni joint was produced at 980°C for 25 minutes in argon atmosphere. For SEM observation, the samples were mechanically polished and etched. TEM samples were produced parallel (sample P), perpendicular (sample T) and oblique (sample TP) to the interface by focused ion beam (FIB). The EDS results indicate the inter-diffusion at the interface of W, Ni, Co and C and the segregation of Ni and Co, together with the formation of crystalline phases and an amorphous carbon layer. W follows a homogeneous diffusion while Ni and Co show a non-homogeneous diffusion behavior.

Ti6Al4V alloy is currently the most common metal alloy of the α+β phase type, its application is increasing as it has excellent properties at elevated temperatures. The main users of Ti6Al4V alloy are industries like of  aerospace, naval, and biomedical; therefore, Ti6Al4V alloys one of the most studied material worldwide. One of the great advantages that Ti6Al4V alloy offers is the possibility of manufacturing components in situ by means of additive technologies.. Similar studies, in additive manufacturing, have reported the formation of titanium oxide on the surface of the material, followed by an oxygen-enriched region called "α-case". By means of thermogravimetric analysis, the oxidation effect on the surface of Ti6Al4V samples, obtained  by wire arc additive manufacturing as well as samples from conventional manufacture, were studied. Argon gas, with an oxygen partial pressure of 1x10^-5 atm, was used as the oxidation atmosphere within a range of 550°C to 950°C and oxidatión times of 60 min and 180 min.  For the oxidation reaction, the kinetic analyses led to calculate the activation energy as 250 kJ/mol and 166 kJ/mol for the Ti6Al4V alloy processed by conventinal and additive manufacturing, respectively. The results of the of thermogravimetric analysis were fitted to a parabolic-type kinetic model. Furthemore, a mathematical model was proposed to predict the oxidation kinetics. The experimental data were fitted to the mathematical model in the range of 750 - 950°C for Ti6Al4V alloy by wire arc additive manufacturing.  The oxidized microstructures were analized by optical and electronic microscopy finding α-case on the surface of the samples.

The investigation of structural stability, electronic, mechanical, spontanous polarization, and thermodynamic properties of simple cubic perovskite oxides XGeO3 (X =Sr, Ca) has been performed through density functional theory as introduced in Wien2K code. The tolerence factor, Born criteria, and phonon dispersion confirm the stability and the formation of both materials in the ideal cubic structure. Additionally, the application of nmBJ approach in electronic properties shows an exceptional semiconducting aspect. The strain effect on spontaneous polarization of XGeO3 (X =Sr, Ca) perovskites presents an excellent ferroelectric behavior. The thermodynamic parameters such as volume, bulk modulus, thermal expansion coefficient, Debye temperature, Gibbs free energy, enthalpy, heat capacities, and Gruneisen, have been ¨ calculated and discussed with a wide range of pressures (0−20 GPa) and temperatures (0−1000 K). Based on the exceptional semiconducting nature and significant spontaneous polarization, the studied materials can be considered as ferroelectric materials, which make them as a suitable candidates in ferroelctric devices.

The use of the Dunkl derivative, defined by a combination of the difference-differential and reflection operators, allows the classification of the solutions according to even and odd solutions. Recently, we considered the Dunkl formalism to investigate the Bose-Einstein condensation of an ideal Bose gas confined in a gravitational field. In this work, we address another essential problem and examine an ideal Bose gas trapped by a three-dimensional harmonic oscillator within the Dunkl formalism. To this end, we derive an analytic expression for the critical temperature of the N particle system, discuss its value at large-N limit and
finally derive and compare the ground state population with the usual case result. In addition, we explore two thermal quantities, namely the Dunkl-internal energy and the Dunkl-heat capacity functions.