Revista Mexicana de Física

Time-dependent conserved operators for Schrödinger equation with constant electromagnetic field and quantization of resistance

2024-08-04T18:03:00+00:00

Two systems are studied: the first one involves a charged particle under the influence of a constant electric field, and the second one involves a charged particle under the influence of a constant electromagnetic field. For both systems, it is possible to find time-dependent conserved operators that can be used to derive time-dependent solutions to the complete Schrodinger equation. These conserved operators are employed ¨ to define the symmetries of the system. An argument of invariance of the wave function under the action of a unitary operator leads to the quantization of resistance and resistivity, in integer multiples of the von Klitzing’s constant, for the first and second case respectively.

Electronic, phonon and thermoelectric properties of RbLaGe half-Heusler alloy: A DFT study including spin-orbit coupling

2025-03-09T18:37:32+00:00

The phonon, electronic and structural properties of the novel RbLaGe half-Heusler alloy are analysed using density functional theory (DFT) with the generalized gradient approximation (GGA). The semiclassical Boltzmann transport theory under the constant relaxation time approximation is employed specifically to evaluate the thermoelectric properties. The results reveal that RbLaGe is energetically, structurally, and dynamically stable, suggesting its potential for experimental synthesis. RbLaGe exhibits semiconducting behaviour with a direct bandgap, 0.79 eV. Spin-orbit coupling has a more pronounced effect on the conduction band other than on the valence band, leading to a splitting of 0.01 eV approximately at point X. Thermoelectric properties, including power factor (P F/τ ), merit figure (ZT), electronic thermal conductivity (κ_e/τ), electrical conductivity (σ/τ ) and Seebeck coefficient, are analyzed using Boltzmann transport theory within the rigid band approximation. The results propose that RbLaGe exhibits high thermopower, which is attributed to the flat band near the Fermi level. Furthermore, the power factor (P F) shows a strong temperature dependence, reaching a maximum value,9.9 × 10¹¹ W/mK²s at 900 K. The calculated thermal conductivity of the lattice (κL) reveals a significant temperature-dependent reduction, improving the merit thermoelectric figure (ZT). Incorporating spin-orbit coupling (SOC) further improves ZT by optimizing the electronic transport properties.

Development of a novel relationship between salt content and radium concentration in crude oil

2025-08-28T01:14:16+00:00

Radium is one of the most important natural radioactive sources associated with crude oil and its extraction processes. The importance of this radioactive element is highlighted by its ability to precipitate inside oil pipelines, forming what is known as scales. Depending on its concentrations in the extracted oils, its concentrations vary according to the type of oil reservoir and its geological formations. The aim of the current study is to find a mathematical relationship linking the salt content of crude oil with the concentration of radium. Thirty samples of crude oil were taken from the fields in Thi Qar province, Iraq, and tested to determine the concentrations of radium resulting from the 238U and 232Th series using gamma ray spectroscopy based on a sodium iodide scintillation detector with dimensions of 3 × 3 inch. At the same time, the salt content was also determined in each of the studied samples. The obtained results were used to create a mathematical relationship linking the radioactive concentration of radium isotopes to the salt content in crude oil. The relationship showed an accuracy of nearly 90% and demonstrated a direct relationship between the salt content and the concentrations of radium isotopes.

Monitoring cancer cell proliferation through etched optical fiber sensor

2025-09-23T23:33:34+00:00

In the present work, the real-time monitoring of murine lung cancer cell line proliferation using the evanescent field generated in an etched optical fiber is presented. The sensor was fabricated by removing 1 cm of the cladding from a single-mode optical fiber using hydrofluoric acid, exposing the 10 µm diameter core. Cell proliferation was monitored using a continuous-wave 1550 nm infrared laser by monitoring power transmission variations in the cell culture medium. The cell proliferation results obtained with this technique were compared with those from an automatic quantifier, showing an inverse relationship between cell proliferation and laser transmission. The present study validates the sensor's effectiveness by correlating light transmission with cell density and refractive index changes. This detection method can be used for rapid cell proliferation analysis in laboratories and hospitals, as well as for studying properties such as refractive index and penetration depth of biological media, making these sensors ideal for studying biological compounds in biochemistry and biomedicine.

Structural upgrade in three adjacent 6 MV linac bunkers operating simultaneously to limit exposure to radiation in controlled and uncontrolled areas

2025-09-01T20:40:58+00:00

The increasing in cancer incidence and advancements in teletherapy technology have necessitated shielding verification in linear accelerator bunkers, which may involve structural changes. This work proposes a hybrid methodology that combines analytical calculations and Monte Carlo simulation (TOPAS/Geant4 simulation toolkit) to determine, validate, and optimise shielding thicknesses in three adjacent bunkers where next-generation 6 MV linear accelerators will operate simultaneously. Findings indicate that the current secondary barriers in the hospital structure comply with international radiation exposure limits. However, the primary barriers require modifications to ensure radiological protection in both controlled and uncontrolled areas.

Assessment of radionuclide concentrations and radiological safety for seeds and roots parts of selected medicinal plants from Iraq markets

2025-09-09T02:19:17+00:00

The present study conducted to determine the natural radioactivity levels and evaluate the health impact of 25 samples of seeds and roots of some medicinal plants widely used in Iraq. A ''3×3'' NaI(Tl) gamma-ray spectroscopy system was utilized to measure and analyze the specific activities of 238U, 232Th, 226Ra, 228Ra, and 40K in the selected samples. The specific activities (Bq/Kg) varied from (5.86 to 1.39) Bq/Kg, (4.36 to 1.62) Bq/Kg, (2.28 to 0.99) Bq/Kg, (7.61 to 1.34) Bq/Kg, and (232.92 to 102.96) Bq/Kg, for 238U, 232Th, 226Ra, 228Ra and 40K, respectively. The average values obtained were 16.7 Bq/Kg for Radium Equivalent activity, 11.866 Bq/Kg for Thorium Equivalent activity, 217.2 Bq/Kg for Potassium Equivalent activity, 8.79 nGy/h for absorbed dose DICRP, 9.068 nGy/h for absorbed dose DBeck, 10.98 nGy/h for absorbed dose DUNSCEAR, 0.049 for internal hazard index, 0.045 for external hazard index, 0.136 Bq/Kg for gamma representative level index, 0.0539 mSv/y for total annual effective dose equivalent, and 0.189×10–3 for total excess lifetime cancer risk. The specific concentration and all the hazard indices associated with it were lower than the maximum permissible limits recommended for safety therefore, there was no threat to the health of the consumer.

Development and experimental validation of a low-cost CMOS based spectrometer for optical and fluorescence applications

2025-08-20T23:39:12+00:00

This work presents the design, construction, and experimental validation of a low-cost CMOS-based spectrometer built using a 3D-printed structure, a general-purpose webcam, and a low-cost diffraction grating. The system was calibrated using LED light sources and validated against a commercial Ocean HR4000CG-UV-NIR spectrometer. Results show that the CMOS-based spectrometer achieves wavelength detection accuracy within ±7 nm and is capable of resolving emission spectra with ~1 nm resolution spacing in the visible range (440–620 nm). The device was also applied to measure fluorescence in vitamin-enriched beverages and to analyze the absorbance properties of colored filters, demonstrating its utility in both chemical and optoelectronic applications. These findings confirm the feasibility of implementing low-cost spectroscopic tools for educational and scientific use.

Interface states effect on conduction mechanisms and barrier height homogeneities of Au/n-GaAs Schottky structures in a wide temperature range

2025-09-11T01:01:22+00:00

In this paper, a study of interface states Nss effect on the conduction mechanisms and the barrier height homogeneities of Au/n-GaAs Schottky structures, in a large range of temperatures. As demonstrated, the structure with low Nss shows that the ideality factor n decreases and the barrier heightɸ_b increases as the temperature increases. On the other hand, the structure with high Nss shows that the ideality factor n decreases then increases with increasing temperature. The increasing of the ideality factor in high temperatures is due to the tunnel current, caused by the interface states. The structure of low Nss shows that the dominant current is the TFE conduction mechanism and gives a homogeneous barrier height over all temperature range. While the structure of high Nss shows that the dominant current is TFE at low temperatures (75-300 K) and deviates to FE at high temperatures (300-400 K), and gives an inhomogeneous barrier height.

Effects of loading types on micro-fracturing and the inherent acoustic emissions in isotropic rocks: a numerical study

2025-10-09T16:34:27+00:00

This study investigates the micro-fracturing of a Statistical Element Volume (SEV), and the emergent acoustic emissions under three loading conditions: simple tension, direct shear, and uniaxial compression. Employing the Discrete Element Method (DEM), the spring-beam bond model, and an elliptic fracture criterion, the SEV created simulates quasi-brittle materials, akin to rocks, featuring key properties like Young’s modulus, shear modulus, Poisson’s ratio, and ratios between maximum compression /tensile strengths around 10. Our analysis reveals a fracture behavior in bond energy (and AE) following a power law behavior analogous to Gutenberg-Richter law. In tension and shear, the power laws are similar. It is under uniaxial compression that a difference is observed. The statistics of bond energy displays two regimes corresponding to two exponents b in the Gutenberg Richter law. These two regimes can be distinguished by considering the state of stress upon failure. In the post peak regime, which is also a dilatant regime of deformation, high energy events are related to compression-shear loads. Such events are very seldom in tension, shear or in the pre-peak regime under uniaxial compression.

Radiation magnetohydrodynamics modeling of an impulsively driven chromospheric jet in the solar atmosphere

2025-09-11T01:16:09+00:00

In this paper, we present a numerical simulation of an impulsively driven chromospheric jet in the solar atmosphere using the non-ideal magnetohydrodynamic (MHD) equations coupled with frequency- and angle-averaged radiation transport equations. These include the dynamics of the radiation energy density and radiation flux. The jet is initiated by a localized Gaussian pulse applied to the vertical velocity component in the upper chromosphere (y = 1.75 Mm), producing a collimated plasma structure that exhibits characteristics similar to macrospicules. We focus on the formation and evolution of the chromospheric jet as it propagates through an optically thin region encompassing the upper chromosphere and solar corona, where both the Planck-averaged absorption and Rosseland-averaged scattering opacities are low. Although radiation transport terms only slightly affect the jet’s morphology, they play a significant role in governing radiative processes in the corona. In particular, radiation transport contributes to the dissipation of the chromospheric jet, which effectively acts as a radiative cooling mechanism as the jet evolves through the optically thin solar corona.

Método de elemento finito discontinuo Padé-LDG para la ecuación de Schrödinger

2025-10-07T02:08:05+00:00

Se describe un metodo de alta precisión numérica para la aproximación de la solución de la ecuación de Schrödinger con potenciales independientes del tiempo. El esquema combina el método de elemento finito discontinuo ”Local Discontinuous Galerkin” para la discretización espacial y aproximaciones racionales [m/m]-Pade para el avance en tiempo. Se analiza la conservación de los análogos discretos de la probabilidad y energía. Los experimentos numéricos validan la conservación de los invariantes y además muestran que para problemas suficientemente regulares el método converge con orden τ 2m + h p+1, donde h y τ son los parámetros de discretización en espacio y tiempo, respectivamente; y p es el grado de los polinomios en la aproximación espacial.

A highly accurate numerical method is described for the approximation of the solution of the Schrödinger equation with time-independent potentials. The scheme combines the Local Discontinuous Galerkin finite element method for spatial discretization and rational [m/m]-Padé approximations as time advancing scheme. The conservation of the discrete analogue of the probability and energy is analyzed. Numerical experiments validate the conservation of the invariants and also show that for sufficiently regular problems the method converges with order τ 2m + hp+1 , where h and τ are the discretization parameters in space and time, respectively; and p is the polynomial degree of the spatial approximation.

Non-geometrical perturbation on homogeneous stealth dust

2025-03-07T18:48:30+00:00

In this work, we study a non-geometrical perturbation to the stealth field, which means the background remains invariant. The stealh is homogeneous in a universe whose source is dust and demand that perturbation unchanged density. As a regular procedure, we introduce a parameter λ to perturb the scalar field equation and get an intriguing expression of the equation, similar to a series expansion in λ. From this procedure, we distinguish and approach to discriminate solutions, and the numerical solutions show that the most significant contribution to the solution comes from the linear term of λ.

Thermal characterization of jatropha-oil blends in the 20-55°C temperature range and tribological study

2025-09-11T01:24:59+00:00

The increasing need for sustainable industrial supplies makes the use of vegetable oil additives a viable option for making industries more environmentally friendly. In this sense, the use of vegetable-based oils can reduce the friction coefficient of oil, decrease wear rates over working temperature ranges, and decrease environmental impact by extending equipment lifetime and potentially reducing the need for oil changes. In this work, motor oil-Jatropha blends at different ratios (97:3, 95:5, 92:8, and 90:10) were investigated for their thermal properties as a function of temperature, and a tribological characterization was performed to obtain the friction coefficients from each motor-Jatropha oil blend. Within the studied temperature range, the results indicate that it is possible to modify the thermal properties or even the friction coefficient by adjusting the mixture ratio. In this work, a further investigation on refined Jatropha as a lubricant oil additive is presented, adding the variation of thermal properties in the temperature range of 20 − 55◦C.

Impact of semi-elliptical cracks on risk assessment for rocket nozzle structural integrity using a fluid-solid interaction

2025-10-21T19:09:08+00:00

Rocket propulsion systems rely on efficient fluid dynamics within their nozzles to achieve optimal performance. However, rocket nozzles can be susceptible to various failure modes that significantly impact their performances. The aim of this study was to investigate the interaction between fluid flow and rocket nozzle structure to identify critical position prone to failure. It was performed in two steps. In the CFD section, Mach number, static pressure, wall Yplus and axial wall shear stress were predicted. In the FEA section, semi-elliptical cracks were intentionally created at the critical position where the maximum hoop stress was located, provided by the CFD analysis. To comprehensively analyze the nozzle’s failure potential, stress intensity factor was numerically carried out and Failure Assessment Diagram (FAD) was employed, as an analytical tool. Each defect depth ratio was evaluated based on its corresponding position within the assessment diagram, while considering factors such as material properties and operating conditions. The main results obtained show that the CFD analysis demonstrated good agreement with the experimental data, with a predicted separation location deviating by only 0.3%. The error between the numerical results and the local measurements on the nozzle wall is 3.84%, which is quite satisfactory. Additionally, the failure assessment indicated that crack depth ratios (a/t > 0.5) in the critical position of the nozzle lead to failure, while ratios (a/t < 0.5) remain within the safe region.

Added mass estimation for a pivoted cylinder undergoing vortex induced vibrations

2025-03-06T18:14:11+00:00

In the present article, we propose and solve an inverse problem to estimate hydrodynamic parameters relevant to the vortex induced vibrations of a pivoted cylinder in laminar flow. For the analysis, we utilized published results from high-performance simulations of this scenario. The study focuses on estimating the added mass parameter, which is crucial in the design of fluid-structure interaction devices and certain numerical techniques for general fluid-structure interaction solvers. We obtain a quadratic relationship between the added mass parameter and the angular acceleration of the cylinder. Moreover, not only are the results significant, but the methodology employed in this article is adaptable to other numerical or experimental fluid-structure interaction results and can assist in determining important design parameters for fluid-structure interaction devices.

Thermal response of a Maxwell fluid in oscillatory boundary layer flow over a wavy wall

2025-11-11T08:41:00+00:00

The thermal behavior of a viscoelastic fluid, modeled using the linear Maxwell model, is analyzed in oscillatory boundary layer flow over a wavy wall. Based on a previously derived velocity field (Cuevas et al. J. Non-Newton. Fluid Mech. 321 (2023) 105125)
that assumes both a small oscillation amplitude and a Stokes layer thickness much smaller than the wall wavelength, the heat transfer equation is solved using a perturbation method. A time-harmonic temperature is prescribed at the wall, and a constant temperature is imposed at the outer edge of the boundary layer. The first order solution corresponds to the thermal analogue of the Stokes' second problem and is independent of the viscoelasticity of the fluid. At second order, convective heat transport gives rise to a temperature field composed of a time-periodic component and a steady distribution, analogous to the steady streaming observed in the corresponding flow problem. The non-vanishing steady temperature at the edge of the inner thermal layer leads to a generalized form of the Rayleigh's law of streaming for the thermal viscoelastic case and, consequently, to the formation of an outer thermal layer whose thickness is estimated.

A century lookback of the physics of drops: A bibliometric and text mining review

2025-04-23T18:55:32+00:00

Droplets are all around us and have been a subject of study since Leonardo Da Vinci made some drawings in the Leicester Codex. Over the years, scientists such as Lord Rayleigh and Worthington have laid the foundations of the fluid dynamics of drops. The central idea of instabilities on a jet or elongated liquid filament leading to breakup of drops depending on surface tension led to numerous discoveries. Today, the study of drop dynamics resides at the frontiers of research and technology, owing to the diverse range of phenomena involved and new experimental and numerical techniques to study them, making it a hot topic in fluid dynamics.
Bibliometrics and text mining offer profound insights into specific topics, and computational tools have provided novel visualization tools to assist science, technology, and innovation management. We performed a query in the WoS database and found more than 12,000 papers dealing with the physics of droplets throughout a century. This study uses bibliometrics and text mining techniques to analyze the abstract of a paper dealing with the physics of drops, using four methods to analyse the evolution of the topic.
We present information on the more frequent authors, journals, categories, institutions, and countries in drops' research, allowing us to view where the research has been done and how it has moved over time. Our study shows that the most simple natural language processing can help understand the evolution and importance of specific research topics.

Behavior of the Feshbach-Villars Oscillator in Gürses space-time under Coulomb-type potential

2025-02-25T16:05:44+00:00

This study investigates the impact of gravitational fields on the spectroscopic structure of the Feshbach-Villars oscillator (FVO) within Gürses space-time. Utilizing the first-order Feshbach-Villars formulation of the Klein-Gordon equation, which describes relativistic wave dynamics for spinless particles, we analyze the quantum mechanical properties of the oscillator under a Coulomb-type potential. The corresponding wave functions and energy levels are derived for both free and interacting cases. Furthermore, we explore the effects of the interaction between the Coulomb-type potential and Gürses space-time on the behavior of the Feshbach-Villars oscillator, particularly in relation to its spectroscopic characteristics. This research provides valuable insights into the intricate relationship between quantum mechanics, relativity, and gravitational fields at the microscopic level.

Identifying the complex underlying transmission network of COVID-19 in México from 2020 to 2024

2025-02-18T19:23:40+00:00

Has been demonstrated that the interaction of individuals in a social network can be modeled using the complex networks theory. In this sense, we believe that knowing at least approximately the underlying network of interaction among the individuals in a society could help to understand the dynamic of diseases transmission among the individuals and elucidate the most effective mechanisms to contain the spread and minimize negative effects like the over-saturation of health systems, such as hospitals and medical clinics. In this work, we study the spread of COVID-19 in Mexico from 2020 to 2024 using the statistical data available in the public health departments of Mexico. Through stochastic simulations we found a complex network that could represent a simplification of the real underlying network of interaction among the Mexican population, in particular we found that the network has degree distribution following a power law P(k) ∼ k −γ with exponent close to γ ≈ 2.5. As mentioned before it could help to understand the spread of future diseases through stochastic simulations using a network structure closer to reality and consequently implement best healthy policies.

The generalized Hubbard model applied to triplet p-wave pairing in Sr1−xKxFe2As2

2025-09-11T01:09:35+00:00

Nowadays several superconductors with singlet pairing of d-wave symmetry are known, but very few triplet-pairing superconductors have been found. It is believed that Sr₂RuO₄ and some uranium compounds such as UTe₂, with very low critical temperatures (T_c) around 1 K, could have Cooper pairs in a triplet state. Other possible candidates that could present triplet pairing are magnetic compounds based in Fe, for example Sr_1−xK_xFe₂As₂, which have optimal doping around x = 0.5 with maximum critical temperature T_c−max=37K. On the other hand, p-wave pairing in a slightly distorted square lattice, described by a generalized Hubbard model, has been investigated considering that the next-nearest neighbor correlated hopping interactions along the two lattice diagonals are slightly different. In this work, we investigate the appearance of triplet-pairing p-wave superconducting states in square lattices where the electron dynamics is described by the generalized Hubbard model. An optimal electron density (n_op), where the maximum critical temperature occurs, was found for each value of the ratio between the next-nearest-neighbor and the nearest-neighbor one-electron hoppings (t'/t), and a search of Hamiltonian parameters was performed to fit T_c as a function of x in the compound Sr_1−xK_xFe₂As₂. An optimal electron density (n_op), where the maximum critical temperature occurs, was found for each value of the ratio t'/t . In particular, the set of Hamiltonian parameters adjusting the fitting is ∆t = 0.5eV , ∆t₃ = 0.05eV and δ₃ = 0.08eV , and the ratio −t′/t = 0.29 adjust in order to obtain a maximum of the critical temperature of T_c−max ≈ 36K at n_op = 0.50, which agrees with the maximum critical temperature (≈ 37K) of the compound Sr_0.5K_0.5Fe₂As₂. With this set of Hamiltonian parameters, other superconducting properties were calculated, such as the amplitude of the p-wave superconducting gap, the ground state and condensation energies, and the electronic specific heat as a function of the temperature and the jump of this at T_c. Additionally, a comparison between the ground states energies of the d- and p-wave superconducting states was made, finding that the p-wave superconducting state has the lowest energy and it can be considered as the ground state. Hence, the compound Sr_1−xK_xFe₂As₂ can be studied under the assumption of triplet pairing with a p-wave superconducting gap symmetry, and probably other similar pnictides, such as Ba_0.4K_0.6Fe₂As₂ with T_c−max = 38K, may present a p-wave triplet pairing.

DFT-driven insights into X2MgGeY6 (X = Na, K; Y = Cl, I) perovskites for photovoltaic and optoelectronic applications

2025-08-18T19:09:14+00:00

We presents in this study a comprehensive analysis of the structural, mechanical, electronic, and optical properties of X₂MgGeY₆ (X = Na, K; Y = Cl, I) perovskite compounds via density functional theory (DFT). The analyzed structural parameters are in close agreement with the available data of the computed structures. The tolerance factor and the positive phonon frequencies in the band structures, authenticate the structural and dynamic stabilities. Analysis of electronic spectra shows that all examined compounds exhibit semiconducting characteristics, with indirect bandgap of 3.13, 1.70, 3.16 and 1.72 eV, respectively. Mechanical analysis confirmed the ionic bonding nature of these materials, as evidenced by positive Cauchy pressure values. As well, the mechanical stability criteria and elastic constants further validate their stability, anisotropy, and ductile behavior. Multiple optical parameters are analyzed including dielectric functions, absorption coefficients, optical conductivity, refractive index and related features with the findings suggest the outstanding optoelectronic performance for photodetectors and LEDs, while iodine-based compounds demonstrate superior potential for solar cell applications. Furthermore, all materials exhibited elastic, thermodynamic, and dynamical stability, confirming their feasibility for practical applications.

Tuning electronic properties of graphene nanoribbons for enhanced detection of toxic gases (F₂, AsH3, PH₃ and HF): A density functional theory study

2025-09-19T23:24:41+00:00

This study investigates the potential of graphene nanoribbons (GNRs) with zigzag and armchair edge configurations as highly sensitive sensors for toxic gases (F₂, AsH₃, PH₃, and HF) using density functional theory (DFT) with the B3LYP/6-31G basis set to model and optimize the geometric and electronic structures of pristine and gas-adsorbed GNR compounds. The electronic, structural, and adsorption properties of these GNRs were analyzed to evaluate their gas-sensing performance. Results reveal that zigzag-edged GNRs exhibit superior sensitivity due to their localized edge states, which significantly alter electronic properties upon gas adsorption, particularly for F₂, as evidenced by a notable reduction in the energy gap (from 1.22 eV to 0.97 eV). Meanwhile, armchair paradigms display stable electronic structures with smaller band gap fluctuations (~0.5 eV). This means that the armchair-edged GNRs demonstrate greater stability and selectivity, with minimal changes in their electronic structure, suggesting robust sensor performance under ambient conditions. Adsorption energy calculations and infrared spectra further highlight the distinct interactions between the gases and GNRs, with zigzag edges showing stronger responses. Additionally, descriptors such as chemical hardness, softness, electronegativity, and dipole moment provide insights into the reactivity and polarizability of the systems. The findings suggest that zigzag GNRs are promising candidates for high-sensitivity gas sensors, while armchair GNRs may be better suited for robust and selective detection applications. This work contributes to the optimization of graphene-based sensors for environmental and industrial toxic gas monitoring.