Revista Mexicana de Física

Study of plasma parameters of non-thermal plasma jet for antimicrobial treatment

2024-08-09T00:14:04+00:00

This study examined the effectiveness of inhibiting bacteria that cause skin diseases using a homemade plasma system known as a microwave-induced plasma jet (MIPJ) operating under atmospheric pressure (APPJ). The system utilized argon gas and a voltage source of up to 2.4 GHz to generate a non-thermal plasma. The inhibition efficiency of thermal plasma was tested against gram-positive (Staphylococcus aureus) and gram-negative (Pseudomonas aeruginosa) bacteria. These bacteria were exposed to the plasma column at various voltages (175-200 V), with a gas flow rate of 5 L/min, a 60-second exposure time, and a 5 cm distance between the plasma and the bacteria samples. The plasma system inhibited Gram-negative bacteria (Pseudomonas) by changing voltages during exposure. At 175 volts, the rate of bacterial inhibition was measured (100%), at 180 volts, the rate was (85%), at 185 volts, the rate was (75%), at 190 volts, the rate was (80%), at 195 volts, the rate was (99%), at 200 volts, the rate was (60%), when exposed to the plasma system, gram-positive bacteria (Staphylococcus aureus) were completely inhibited at all voltage levels. The MIPJ system proved to be an effective tool for treating different types of bacteria. The study also highlighted the impact of argon gas flow rate on bacteria inactivation, emphasizing that the increased gas flow rate and high-speed particle discharge could penetrate the external structure of bacteria, playing a crucial role in bacteria inactivation by the plasma jet.

Optimizing a Physics-Informed Neural Network to solve the Reynolds Equation

2024-06-18T18:00:33+00:00

This study focuses on the optimization of a Physics-Informed Neural Network (PINN) to address Partial Differential Equation (PDE) problems associated with fluid flow. Specifically, the stationary, one-dimensional classical Reynolds equation is solved using the PINN. Within the conducted studies, a comparison is made between the solutions obtained using the PINN, the numerical Finite Difference Method (FD), and the analytical solution. We study various scenarios with diverse hyper-parameters such as learning rate, epochs, number of training points, etc., for constructing the neural network to identify the optimal setup. The PINN accurately approximated the solution to the Reynolds equation (up to O(10−2 ). This suggests that PINNs can be used to address diverse problems in fluid dynamics. We proposed a PINN configuration that outperformed the PINN presented in the literature. The finite differences method obtains a better approximation than the PINNs, however, the full potential of the PINNs is yet to be determined, as it can include data from the problem, that finite difference method (FD) can not. Further studies are planned to investigate the capabilities of PINNs.

Consistency and errors in Smoothed Particle Hydrodynamics using several approaches in a 2D pipe

2024-10-29T20:02:54+00:00

Smoothed Particle Hydrodynamics (SPH) has become a promising tool for the simulation of fluids. Although too much research has been addressed to improve the method over the years, a comparison of the errors and consistency evolution when trying different approaches are still necessary to define the best scheme for practical applications. Here, a two-dimensional Poiseuille flow test benchmark is employed to enforce comparisons when varying the kernel, the definition of the sound speed in
the pressure term, the viscosity and the Reynolds number.

Cluster folding analysis for 15N ions scattered by 13C and 27Al targets

2024-09-17T17:53:42+00:00

Motivated by two well-known cluster structures for the ¹⁵N nucleus, ¹³C + d and ¹¹B + α, which appear at excitation energies (E_x) = 16.159 and 10.992 MeV, respectively, the angular distributions (ADs) for ¹⁵N nucleus elastically scattered in the field of two medium-mass targets, namely, ¹³C and ²⁷Al are investigated within the cluster folding model. Reasonable agreements between the measured and calculated ADs data for the considered nuclear systems are obtained, which validates the cluster structure description of the ¹⁵N ground-state, configured as a core (¹³C/¹¹B) with a valence particle (d/α) orbiting the core. We aim at quantitatively investigating the ¹³C + d and ¹¹B + α cluster structure of the ground state of ¹⁵N nucleus, providing new insight into the fundamental nuclear interactions.

Medición de radón 222 en lugares de trabajo ubicados en sótanos, utilizando detectores LR 115- tipo 2

2024-03-26T17:43:05+00:00

El radon-222 es un gas de origen natural el cual se produce a partir de la desintegración radiactiva natural del Uranio, que está presente en suelos y rocas. El radón emana fácilmente del suelo y pasa al aire, donde se desintegra y emite partículas alfa y produce a su vez una serie de partículas de vida corta (Polonio-218, Polonio-214, y Polonio-210) que tambien decaen emitiendo partículas alfa. Las personas inhalan las partículas de vida corta, y estas pueden causar significativo daño a las células interiores de los bronquiolos y además pueden terminar conduciendo a la aparición de cáncer de pulmón. Por el motivo antes expuesto es de suma importancia medir y evaluar los niveles de exposición debido al radón. En este trabajo de investigación se determina la concentración de radón-222 en 26 lugares de trabajo ubicados en sótanos que pertenecen a 10 edificios en la ciudad de Lima-Perú. En las mediciones se emplean detectores LR-115 Tipo 2 los cuales se colocan sobre la pared de los sótanos en estudio en tres niveles, 40 cm, 100 cm 160 cm de altura medidos a partir del piso. Los detectores luego son grabados y leídos siguiendo el protocolo usado en el Laboratorio de del Grupo de Investigación de Técnica de Huellas Nucleares de la PUCP (GITHUNU-PUCP). Los resultados estadísticos demuestran que 12 lugares de trabajo presentaron niveles de concentración mayores a 150 Bq/m3 , en diferentes periodos de medición, y esto se debió a limitaciones en la ventilación en estos ambientes. Además, empleando el coeficiente de Pearson se logró evaluar la correlación de la concentración de radón-222 con la humedad relativa y temperatura, en 20 ambientes de trabajo. De estos, solo un ambiente muestra una correlación lineal positiva significativa entre concentración y temperatura; y solo un ambiente muestra una correlación lineal negativa significativa entre la concentración y la humedad relativa. De esto concluimos que probablemente las variables meteorológicas de humedad y temperatura no influencian significativamente en la concentración de radón-222 en este tipo de recintos.

Radon-222 is a naturally occurring gas produced by the natural radioactive decay of Uranium, which is present in soil and rock. Radon readily emanates from the soil and passes into the air, where it decays and emits alpha particles and produces a series of short-lived particles (Polonium-218, Polonium-214, and Polonium-210) that also decay by emitting alpha particles. People inhale the short-lived particles, and these can cause significant damage to the inner cells of the bronchioles and may also lead to the development of lung cancer. For the reasons stated above, it is of utmost importance to measure and evaluate the levels of exposure due to Radon. In this research work, the concentration of Radon-222 is determined in 26 workplaces located in basements belonging to 10 buildings in the city of Lima, Peru. In the measurements, LR-115 Type 2 detectors are used, which are placed on the walls of the basements under study at three levels, 40 cm, 100 cm and 160 cm high, measured from the floor. The detectors are then recorded and read following the protocol used in the Laboratory of the Nuclear Fingerprint Technique Research Group of the PUCP (GITHUNU-PUCP). The statistical results show that 12 workplaces presented concentration levels greater than 150 Bq/m3 , in different measurement periods, and this was due to limitations in ventilation in these environments. In addition, using the Pearson coefficient, it was possible to evaluate the correlation of the concentration of radon-222 with relative humidity and temperature, in 20 work environments. Of these, only one environment shows a significant positive linear correlation between concentration and temperature; and only one environment shows a significant negative linear correlation between concentration and relative humidity. From this we conclude that meteorological variables of humidity and temperature probably do not significantly influence the concentration of radon-222 in this type of enclosure.

Phase shift analysis with half-shell quantities for nucleus-nucleus systems using a simplified potential model

2024-08-13T13:36:33+00:00

In this work we propose a combined interaction, nuclear and electromagnetic in origin, to treat the charged hadronic systems by considering the same range of both the potentials under consideration. Since the effect due to charges becomes screened at a certain distance, we believe it desirable to include the effect of very short-range electromagnetic interaction. It is worthwhile to mention that in such situations the effect of the combined potential is often examined within the nuclear domain. Keeping this in view we consider nuclear Manning-Rosen plus the atomic Hulthén potential of equal range parameter for simplicity of calculation. The validity of our conjecture is examined through some model calculations with respect to their on- and off-shell effects.

Investigating the effects of phase-space non-commutativity coordinates on the modified Deng-Fan Yukawa potential model and thermodynamic properties in 3D(NR-NCPS) and 3D(NR-QM) symmetries

2024-08-26T00:09:14+00:00

An approximate new bound state solution of the three-dimensional deformed Schrodinger equation under the deformed phase-space sym- ¨ metries for the modified Deng-Fan Yukawa potential model that is obtained from the combination of the corresponding expression in threedimensional non-relativistic quantum mechanics symmetries and some central terms [exp (−αr)/r (1 − exp (−αr)), exp (−2αr)/r (1 − exp (−αr))2 , exp (−3αr)/r (1 − exp (−αr))3 , exp (−αr)/r 2 , exp (−αr)/r 3 and 1/r 4 ] coupled with the infinitesimal non-commutativity vector Θ and the angular momentum operator L. With the help of the parametric generalized Bopp’s shifts method, the independent time perturbation theory method, and an approximation scheme, the analytical energies of the studied were obtained for both symmetries, for different quantum numbers. The new non-relativistic energy equation under the studied potential for the homogenous diatomic molecules (HODMs) (H2, I2); the heterogeneous diatomic molecules (CO, HCl, LiH); the neutral transition metal hydrides (ScH, TiH, VH, CrH); the transition-metal lithide (CuLi); the transition-metal carbides (TiC, NiC); the transition metal nitrite (ScN) and the transition metal fluoride (ScF) and in the presence of deformation phase-space are dependent on the discrete atomic quantum numbers (j, l, s and m), the dissociation energy, the equilibrium bond length, and the screening parameter (re, De, and α), the deformation phase parameters (P nc p and S nc p ). The new resulting energy equation is utilized to calculate spin-averaged mass spectra of the heavy mesons under the studied potential and Deng-Fan Yukawa potential model in three-dimensional non-relativistic quantum mechanics and 3it’s extended symmetries. Furthermore, we have calculated the partition function, from which thermodynamic properties such as mean energy, specific heat capacity, entropy, and free energy are derived in both three-dimensional non-relativistic quantum mechanics and the deformed phase-space symmetries symmetries. Notably, the two special cases, representing the modified Yukawa potential and the modified Deng-Fan potential were treated in extended phase-space symmetry for energies and thermodynamic properties. Our current study promises to apply to different areas of physics in various domains, including atomic and molecular physics.

Approximate energy spectra of diatomic molecules (LiH, HCl, VH, I2) case of the Hulthén plus screened Kratzer potential

2024-10-24T02:31:14+00:00

In this research, we used the Nikiforov Uvarov functional analysis method to solve the Schrödinger equation with the Hulthén plus screened Kratzer potential using the Greene Aldrich approximation to remove the centrifugal barrier. We determine the bound state energies and corresponding wave functions. We applied our results to several diatomic molecules (LiH, HCl, VH, and I2) to analyze their energy spectra. Our technique produced accurate results, which were validated by comparing our eigenvalue data with numerical data obtained by other researchers. Given the precision of this analytical method, we recommend its application in solving problems in non-relativistic and relativistic systems, particularly those involving exponential potentials.

Multiphoton dissociation of thiophene with 532 and 355 nm

2024-10-15T23:36:03+00:00

The fragmentation of thiophene was investigated using incident laser radiation with two wavelengths, 532 and 355 nm. The results indicate that the intense fragmentation of thiophene molecules decreases at high radiation intensities as was evidenced by the ion C⁺. Additionally, the effect of wavelength on the formation of the parent ion, as well as the production of lighter fragments, such as C₂H₂⁺, is examined. Finally, the dissociation between thiophene and furan to assess the influence of heteroatoms on the fragmentation of these heterocyclic molecules is compared. Our observations reveal the role of hydrogen migration on these heteroatoms.

Elastic constants and thermophysical properties of CuPd: First-principles study

2024-07-23T19:49:20+00:00

Based on density functional theory, the structural parameters, elastic moduli and thermophysical properties of Copper-palladium CuPd inter-metallic compound at various temperatures and under high pressures have been studied using first-principles calculations. The pseudopotential-plane wave method within the generalized gradient approximation approach have been utilized to perform the calculations presented in this paper. The material being considered is a pure substance of solid CuPd, arranged in the body centered cubic fashion. The calculated lattice constant is found to be around 3.001 Å, which is in good agreement with the experimental one of 2.96 Å reported in the literature. The elastic stiffness constants are found to increase monotonically and almost linearly with raising pressure. The mechanical stability under compression and the hardness of CuPd are predicted using the elastic constants. Moreover, the isothermal bulk modulus, the constant volume heat capacity, the Debye temperature and the entropy are studied in the pressure range from 0 to 12 GPa and at temperatures ranging from 0 up to 600 K. At room temperature and zero-pressure, the constant volume heat capacity and the entropy are found to be 45.65 and 53.94 J/mol.K, respectively.

Structural and AC conductivity of polyaniline doped nickle oxide nanocomposites

2024-08-10T20:18:13+00:00

In this work, we have investigated the influence of polyaniline on the structural and electrical properties of polyaniline-nickel oxide (PANI-NiO) nanocomposites prepared by in-situ chemical polymerization. The experimental procedure involved the synthesis of Polyaniline (PANI) and their composites with varying weight percentages of NiO nanoparticles using an in-situ polymerization route. The structure of NiO@PANI nanocomposites was verified using the X-ray diffraction technique. It was observed that NiO exhibited a single-crystalline structure, whereas PANI displayed a non-crystalline structure. Scanning electron microscopy (SEM) revealed spherical NiO and granular PANI, both with homogeneous distribution, and increased polymer content resulted in more porosity. The measured values of dielectric constant, dielectric loss, and AC conductivity decreased as frequency and temperature increased. The optimum presence of conductive PANI with nickel oxide in a composite is responsible for the increase in AC electrical conductivity. The prepared composite material behaves as a semiconductor and may be helpful for charge storage devices and related field applications.

On the Euler collinear motion of three bodies interacting with the Newton gravitational force

2024-09-14T21:32:27+00:00

We present a set of mathematical properties that are very simple notwithstanding these properties are hidden in the literature, considering the Euler case of collinear motion of three bodies, including simple mathematical properties enabling the non-specialists to become very familiar with this classical pearl of the mechanics of the three body problem.

Inflation in an R 2 -Corrected f(R) gravity model

2024-08-20T15:48:58+00:00

We conducted an analysis of the inflationary scenario within the f(R) gravity framework, focusing on the Gogoi-Goswami model defined by the parameters α > 0, β > 0, and the characteristic curvature constant R_c. This model exhibits a potential in the Einstein frame characterized by V ∝ φ p . The spectral index for this model is given by n_s = 1 − (p + 2)/2N, while the tensor-to-scalar ratio is r = 4p/N, where N denotes the e-folding number at horizon crossing. Although this model aligns with the Planck 2018 observational data within a narrow range, specifically 1.10 ≤ p ≤ 1.25 for N = 50, it becomes increasingly difficult to find an appropriate value for p when N ≥ 54. To overcome this limitation, we propose incorporating an R 2 correction term from the Starobinsky model to enhance the inflationary predictions. Our analysis indicates that this correction improves the model’s performance when optimal parameters are selected, specifically by setting x₀ = R₀/R_c«1 (with R0 representing the scalar curvature during the late-time accelerated expansion), α_max = O(1), and introducing a parameter γ related to the R² term within the range −0.024600 < γ < 0. The parameter x₀ establishes a connection between α and β via the de Sitter solution of the model. Additionally, the parameter Rc can be estimated similarly to that in the Starobinsky model, as R_c ~ (1.3 × 10⁻⁵ /κ)² .

Application of Laskin Fractional Quantum mechanics with a changed fractional differential operator to one-dimensional potentials

2024-07-01T21:51:05+00:00

We studied the quantum mechanics problem of certain one-dimensional potential functions using Laskin fractional quantum mechanics. We used different representations to describe the kinetic energy operator, including the conformable and Riemann-Liouville-Caputo fractional differential operators. We then compared each approach's energy states and wave function outcomes for single and double rectangular and harmonic potentials. As the fractional index increased, there was a noticeable difference between the excited level energy values resulting from each method. Additionally, we find a noticeable change in the probability density when the system exhibits degenerate states. Our results provide a straightforward and standardized approach for solving the one-dimensional fractional Schrödinger equation numerically.

Solutions of the Schrödinger-Poisson equations for n―dimensional states

2024-10-17T20:13:09+00:00

We construct stationary solutions for the Schrödinger-Poisson system of equations for n–dimensional states. We find that these have the solitonic profile of the ground state solution of the scalar case n = 1 for all the fields. We numerically study the cases n = 1; 2; 3; 4; 5, because these multifield scenarios have been proposed as a generalization of the scalar field dark matter n = 1, specially vector n = 3 and tensor n = 5 fields. In order to verify the formation of core-halo density profiles we simulate multi-core mergers of equilibrium configurations and show that every field accommodates itself with its own solitonic+halo profie, showing in this way that equilibrium solutions are attractor cores.

Preparation and characterization of potato starch/bentonite organophylized by SDS

2024-08-03T02:20:23+00:00

This study focuses on the development of nanocomposite films using potato starch via a casting technique. Glycerol was incorporated as a plasticizer, while Sodium Dodecyl Sulfate (SDS)-modified bentonite acted as reinforcement. Various analytical methods, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), UV/vis spectroscopy, Electron microscopy (SEM), and Optical microscopy (MOP), were utilized to assess the material properties. Different concentrations of SDS, below, at, and above the critical micelle concentration (CMC), were investigated. The findings suggest that films containing higher SDS levels demonstrate enhancements in both physical and chemical characteristics. XRD assessments reveal that films with SDS concentrations surpassing the CMC level display homogeneity, indicating effective intercalation or exfoliation processes. This compatibility of the biofilm components is further evidenced through FTIR, SEM, and MOP. Moreover, the introduction of SDS significantly improves the film’s biodegradability, as confirmed by thermogravimetric analysis.

Potential-pulse assisted adsorption of carminic acid dye onto TiO2 nanoparticles for faster fabrication of higher efficiency sensitized solar cells

2024-10-22T02:45:36+00:00

Dye adsorption onto the TiO₂ nanoparticles thin film is typically the slowest step in the preparation of dye-sensitized solar cells. Potential assisted adsorption has previously shown to significantly reduce the adsorption time from several hours to minutes. However, it also reduced the cell efficiency in most of the cases and increased it up to 13 % compared to the classical adsorption method, by applying a constant potential for 60 min. In this work, pulsed potential assisted adsorption of carminic acid dye onto TiO₂ nanoparticles significantly reduced the adsorption time and increased the cell efficiency up to 33 % compared to classical adsorption, applying a pulse time of 10 ms and amplitude of 0.5/-0.4 V for 30 min. On the other hand, a single-frequency electrochemical impedance measurement method for monitoring the dye adsorption onto the nanoparticles was tested and provided similar results to the capacitance measurement method. This single-frequency value was determined with the help of relative contribution impedance plots.

Synthesis of boron nanoparticles by a hybrid “polyol-solvothermal” process using glycerol as reducing agent

2024-10-15T23:26:36+00:00

In this article, a novel hybrid synthesis process called the “polyol-solvothermal process” is presented. This process utilizes a polyol-solvothermal hybrid method under acidic conditions (pH = 1) to obtain amorphous boron nanoparticles with a spherical morphology. The synthesis parameters include different concentrations of metalloid ions (1 and 2 M), glycerol (50% and 80% w/w), and PVP (0.01 g and 0.02 g). To examine the morphology and particle size, surface plasmon resonance (SPR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were employed. The TEM analysis revealed the presence of spherical nanoparticles with an average size of ~5 nm and quasi-spherical microparticles with an average diameter of 3.5 µm. This suggests the presence of microparticles composed of smaller particles, which was confirmed by the surface plasmon resonance (SPR) results. The SPR analysis revealed bands around 275 nm, indicating the presence of boron nanoparticles. The x-ray diffraction (XRD) results show a single peak associated with the formation of amorphous boron. Furthermore, the FT-IR studies identified a peak between 1019 and 1040 cm^-1, which is related to the stretching vibrational bond of CH₂-OH, indicating the decomposition of glycerol into primary alcohols, which acted as reducers. Another band, located at approximately 500 cm^-1and characteristic of the M-O vibrational bond, was associated with the formation of metal nanoparticles.

On the split Voigt profile and its use in the analysis of X-ray diffraction patterns

2024-10-28T18:15:11+00:00

The main properties (integral breadth, FWHM, Fourier transform) of the split Voigt function have been analysed. These are important in the study of the X-ray diffraction peaks. In this way, some X-ray diffraction lines of a sample of quartz and zirconia has been analysed by using single line methods, describing the instrumental-spectral asymmetric peaks by means of split Voigt functions.

A novel optical flow method based on a second-order non-linear differential equation

2024-10-11T18:04:30+00:00

A novel optical flow algorithm based on a second-order nonlinear differential equation is presented. This equation expresses the difference between two sequential images, and from its solution, the optical flow information between the images can be extracted. The new algorithm is compared with standard optical flow algorithms, as well as some of their recent generalizations. The comparisons are conducted using common tests applied in particle image velocimetry. The results show that the new algorithm outperforms classical algorithms in these particular tests.

Fusion of coherent-solitonic states

2024-04-14T20:20:43+00:00

We report numerical results on the interaction between lowest order solutions of the Gross-Pitaevskii equation, the coherent-solitonic states. It is shown that under specific conditions two zero-order states can almost fuse into a first-order state and nearly maintain the shape during propagation. The conditions of fusion are analyzed. To a lesser extent, the same behavior is observed for three state fusion.