Revista Cubana de Física
type: channel
description: The Revista Cubana de Física (RCF, Cuban Journal of Physics) is a biannual open access journal (e-ISSN 2224-7939, p-ISSN 0253-9268) published by the Cuban Physical Society (SCF) and the School of Physics of the University of Havana (FF-UH) solely funded by its publishers (without charges to the authors). Three types of articles are considered for publications: Regular Original Articles, Original Short Articles and Review Articles. Likewise, the RCF includes other several sections as: Moments of the Cuban Physics, For Physics and Non-Physics, News and Obituaries. Concerning the language, manuscripts in Spanish as well as in English are welcome in Microsoft Office Word (.doc or .docx) and LaTex (.tex) formats. The peer-review is blind and performed by external reviewers outside the editorial team of the RCF, the SCF or the FF-UH.
publisher: Sociedad Cubana de Física & Facultad de Física de la Universidad de La Habana
language: en
publication name: Revista Cubana de Física
issn: 0253-9268
items: Temperature-Dependent Resistivity and Conduction Mechanisms in Co and F Codoped NiO Thin Films
items: A Superconductivity Breakthrough: Feeling the Pressure to Release the Pressure
items: Adsorption of Piperazine-dithiocarbamate on Au(111): An electrochemical Scanning Tunneling Microscopy Study
items: Computational Analysis of Structural Stability and Resistance to Gamma and Electron Radiation in LMO and LNMO Spinels
items: Influence of the Repulsion of Twin Impactors on Granular Craters: Preliminary Experiments
items: Scrutinizing with Antimatter
items: Ivar Giaever: An Unlikely Hero of Quantum Times
items: Belief Propagation with Informed Initialization in Combinatorial Optimization Problems
items: Testing the Thin Capillary Model
items: The Institute of Materials Science and Technology (IMRE) of The University of Havana: 40th Anniversary
items: Effects of Coherence and Domain Walls on Diffraction Profiles in Rare-Earth Doped PbTiO₃
items: Mathematical Model for Estimating Soil Redistribution Rate by Water Erosion Using The Nuclear and Isotopic FRN Technique
items: Role of Radiofrequency Power on the Crystallographic, Morphological and Optical Properties of Sputtered Aluminium Thin Films
items: High-power Laser Prototype for Soft Tissue Surgery in Dentistry
items: Mw-ML and MW-Mc Seismic Magnitude Scaling Relationships for Cuba
items: Problem-based Learning with Video Analysis: The Case of the Variable-Mass Atwood Machine
items: Computational Optimization of A Stochastic Model for Simulating Apoptotic Signaling
items: New Sigmoid Curves
items: Demonstrative Teaching Experiment to Motivate the Study of Radioactivity with a Research Approach
items: Mathematical Treatment of the Canonical Finite State Machine for the Ising Model
items: The Role of Clay Charge in The Mobility of Compensating Cations
items: Metal-Insulator Transition described by NOFT
items: Radioactivity Levels and Radiation Hazard in Sands from Cuban Beaches
items: Pyroelectric Response and Figures of Merit of Lead-Free Ferroelectric Ceramics
items: Towards the STM: The Story Behind The First Atomic Resolution Image in Cuba
items: Photodissociation Dynamics of the Collinear Van Der Waals Complex NeBr2(B, ν=14-34)
items: Study of the Rotation Dynamics of a Rigid Body through the accelerometer of a Mobile Device
items: Quasi-classical Dynamics of Hydrogen Molecules Trapped Inside Fullerene Cages
items: The Two-state Diffusion Problem with Resetting
items: Particle Fluence Estimation for Samples Irradiated at a Long-Term Exposure Station (NICA Complex, Dubna)

Temperature-Dependent Resistivity and Conduction Mechanisms in Co and F Codoped NiO Thin Films
type: item
description: In this work, Co- and F-codoped NiO thin films were successfully deposited on glass substrates using a pneumatic spray deposition method at 420 °C. The influence of temperature and dopant concentrations on the electrical and optical properties of the films was systematically investigated. Electrical measurements were performed in two stages, based on the evaluation of voltage and current over the temperature range of 30–180 °C. It was observed that temperature significantly affected the voltage and current, with optimum values obtained at higher temperatures. The lowest electrical resistivity was achieved for the film doped with 2% Co and 12% F. Optical analysis indicated that the Co- and F-codoped NiO films exhibited high transparency in the visible region. Furthermore, the optical band gap increased with higher Co and F concentrations in all deposited samples. The minimum Urbach energy, 0.342 eV, was observed for the film containing 2% Co and 8% F, indicating reduced localized states in the band tails and improved optical quality.
subject: Original Articles
  topic: section
subject: NiO
  topic: keywords
subject: Thin films
  topic: keywords
subject: Co and F cooping
  topic: keywords
subject: TCO
  topic: keywords
subject: spray pneumatic method
  topic: keywords
creator: S. Benramache
creator: A. Arif
creator: A. Guettaf
creator: A. Sbaihi
creator: N. Chaouch
creator: A. Lakel
creator: O. Belahssen
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 32
ending page: 39

A Superconductivity Breakthrough: Feeling the Pressure to Release the Pressure
type: item
description: The discovery of high-temperature superconductivity in cuprates during the late 1980s triggered an intense race to raise the critical temperature (Tc), driven both by scientific pressure and physical pressure applied via diamond anvil cells. While mercury-based cuprates, particularly HgBa2Ca2Cu₃O8+δ (Hg-1223), held the ambient-pressure record of 134 K for over three decades, achieving higher Tc at ambient conditions remained elusive. This paper reviews the history of pressure-enhanced superconductivity and presents a recent breakthrough: the Pressure-Quench Protocol (PQP). By applying high pressure at room temperature, cooling the sample under pressure, releasing the pressure at cryogenic temperatures (below 20 K), and finally warming to ambient temperature, the high-pressure superconducting phase becomes “kinetically trapped”. This protocol yields an ambient-pressure Tc of approximately 150 K in Hg-1223—the highest ever recorded at ambient pressure. Structural retention is confirmed by synchrotron X‑ray diffraction, and the method opens new pathways for discovering and stabilizing high-temperature superconducting phases without requiring continuous external pressure.
subject: For Physicists and Non-physicists
  topic: section
subject: Superconductivity
  topic: keywords
subject: Pressure-Quench Protocol (PQP)
  topic: keywords
subject: Mercury-based cuprates (Hg-1223)
  topic: keywords
subject: Metastable high-pressure phase
  topic: keywords
subject: Ambient-pressure record critical temperature
  topic: keywords
creator: E. Altshuler
creator: A. Batista-Leyva
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 43
ending page: 46

Adsorption of Piperazine-dithiocarbamate on Au(111): An electrochemical Scanning Tunneling Microscopy Study
type: item
description: The adsorption process of piperazine-dithiocarbamate potassium salt, which occurs on the Au(111) surface, was studied by using electrochemical scanning tunneling microscopy. Perchloric acid and sodium hydroxide were used as electrolytes. The results revealed that, depending on the applied potential and the nature of the electrolyte, the entire molecule or just individual sulfur atoms were adsorbed forming different sulfur phases, instead of the entire molecule.
subject: Original Articles
  topic: section
subject: Thin films
  topic: keywords
subject: scanning tunneling microscopy
  topic: keywords
subject: electrochemistry
  topic: keywords
subject: microscopy of surfaces
  topic: keywords
subject: interfaces
  topic: keywords
creator: Mayra P. Hernández Sánchez
creator: Javier Alberto Martínez Pons
creator: Gema Navarro-Marín
creator: José Valenzuela
creator: José Alfredo Herrera
creator: Mario H. Farías
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 25
ending page: 31

Computational Analysis of Structural Stability and Resistance to Gamma and Electron Radiation in LMO and LNMO Spinels
type: item
description: This study investigates the response to gamma and electron radiation of materials used as cathodes in lithium-ion batteries, specifically LiMn2O4 (LMO) and LiNi0.5Mn1.5O4 (LNMO), through the computational analysis of displacement crosssections per atom. The results indicate that the partial substitution of Mn with Ni in LNMO significantly increases radiation resistance, which is attributed to the strengthening of Ni-O covalent bonds, the reduction of Jahn-Teller distortions, and the stabilization of the crystal lattice. Monte Carlo simulations using the MCCM software reveal that LNMO requires energies 1.3 − 1.8 times higher for the initiation of atomic displacement cascades compared to LMO.
subject: Original Articles
  topic: section
subject: Spinel materials (81.05.Ja), Radiation damage (61.80.-d), Threshold displacement energy (61.72.Cc), Lithium-ion batteries (82.45.-h), Atomic displacement cascades (61.82.-d)
  topic: keywords
creator: D. Valdés .
creator: A. Leyva Fabelo
creator: Carlos Manuel Cruz Inclán
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 20
ending page: 24

Influence of the Repulsion of Twin Impactors on Granular Craters: Preliminary Experiments
type: item
description: We perform experiments where pairs of identical spheres are simultaneously dropped, side-by-side, into a granular bed. The spheres are either glued together (Siamese) or unglued (Free twins). In the Free twin protocol, the spheres separate from each other in the horizontal direction, resulting in a non-circular, elongated crater. This happens in a significantly lesser degree for Siamese intruders. So we demonstrate that force-chain mediated repulsion implies an increase of the aspect ratio of double-impact granular craters. The effect is reinforced if the granular bed is more compact, so the spheres penetrate only partially.
subject: Original Communications
  topic: section
subject: Granular matter
  topic: keywords
subject: impact cratering
  topic: keywords
subject: soft condensed matter
  topic: keywords
creator: P. Altshuler
creator: R. Pupo-Santos
creator: A. Rivera
creator: E. Altshuler
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 40
ending page: 42

Scrutinizing with Antimatter
type: item
description: Physics suggests that Nature is made of matter and the so-called anti-matter, the latter in lesser extent. Antimatter is made up of antiparticles with the same mass, but although their charge and magnetic moment are of the same magnitude, they are opposite to those of the corresponding particle of ordinary matter. The collision of particles and antiparticles generates high-energy photons. This paper presents an introduction to the use of antimatter, specifically antielectrons or positrons, to explore and study, through their annihilation with present electrons, aspects as diverse as the metabolism of tissue in a living being and the characteristics of vacancy defects in various materials.
subject: For Physicists and Non-physicists
  topic: section
subject: Matter and anti-matter
  topic: keywords
subject: positron annihilation
  topic: keywords
subject: positron emission tomography
  topic: keywords
subject: positron annihilation spectroscopy
  topic: keywords
creator: A.A. Iribarren-Alfonso
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 133
ending page: 137

Ivar Giaever: An Unlikely Hero of Quantum Times
type: item
description: Giaever, who passed away in June 2025, transformed quantum physics through his experimental discovery of tunnelling in superconductors, a phenomenon predicted by BCS theory and intimately linked to the superconducting gap. Despite his modest academic beginnings, he achieved groundbreaking results at General Electric by demonstrating quasiparticle tunnelling across superconductor–insulator–superconductor junctions. His curiosity, perseverance, and collaborative environment enabled this achievement. The author, whose own research was shaped by tunnelling effects in ceramic superconductors, reflects on Giaever’s profound influence during a fleeting elevator encounter.
subject: For Physicists and Non-physicists
  topic: section
subject: Superconductivity
  topic: keywords
subject: Nobel prize in physics
  topic: keywords
subject: quantum tunnelling
  topic: keywords
subject: history of science
  topic: keywords
creator: E. Altshuler
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 131
ending page: 132

Belief Propagation with Informed Initialization in Combinatorial Optimization Problems
type: item
description: In this work, we study the behavior of the Belief Propagation (BP) algorithm in solving two combinatorial optimization problems: 3-SAT and 3-XORSAT. We examine the performance of BP on planted instances, applying the algorithm with a fraction of the variables fixed from the beginning. The probability of reaching any solution using this informed initialization displays abrupt changes with the number of fixed variables. In both problems, BP requires fixing a smaller fraction of variables than the Monte Carlo algorithm to solve a given instance. We also extended a known analytical description of the Unit Clause Propagation Algorithm to accurately predict BP’s behavior with an informed initialization for 3-XORSAT in random regular graphs.
subject: Original Articles
  topic: section
subject: combinatorial optimization
  topic: keywords
subject: planted model
  topic: keywords
subject: belief propagation
  topic: keywords
creator: D. Machado Pérez
creator: R. Mulet
creator: A. Pérez
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 4
ending page: 12

Testing the Thin Capillary Model
type: item
description: We provide a detailed and accessible introduction to the exact theory of capillary phenomena in a cylindrical tube of finite radius. We demonstrate explicitly that Jurin's law always somewhat underestimates the height of liquid rise. The largest deviations occur for small contact angles. In the limiting case of a very large capillary radius, the true column height becomes independent of the radius and approaches a finite limiting value. The mean curvature of a real meniscus is a monotonically increasing function of the capillary radius. We argue that the force balance method is most appropriate for deriving Jurin’s law, whereas the exact capillary equation requires the use of the pressure balance method or the Helmholtz energy minimization procedure.
subject: Original Articles
  topic: section
subject: capillary
  topic: keywords
subject: Jurin's law
  topic: keywords
subject: column height
  topic: keywords
subject: mean curvature
  topic: keywords
creator: V. V. Ivchenko
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 120
ending page: 123

The Institute of Materials Science and Technology (IMRE) of The University of Havana: 40th Anniversary
type: item
description: This article presents a short review of the scientific history of the Institute of Materials Science and Technology (IMRE) of the University of Havana, from its creation in 1985 to its 40th anniversary. We analyze the main research results achieved during these 40 years, as well as an study of its historical performance.
subject: Moments of the Cuban Physics
  topic: section
subject: History of science
  topic: keywords
subject: national and international laboratory facilities
  topic: keywords
subject: materials science
  topic: keywords
subject: nano-science
  topic: keywords
subject: nanotechnology
  topic: keywords
creator: J. A. Martínez
creator: K. Valdiviés-Cruz
creator: C. R. Milian-Pila
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 138
ending page: 144

Effects of Coherence and Domain Walls on Diffraction Profiles in Rare-Earth Doped PbTiO₃
type: item
description: The paper presents a study concerning the coherence and domain wall effects on the profile of selected X-ray diffraction (XRD) peaks from the ferroelectric system Pb0.92Ln0.08TiO3 (Ln3+ = La3+, Dy3+). The analysis focuses on the hkl-dependent broadening and asymmetry of certain diffraction peaks. The study was conducted using a diffraction model evaluated with experimentally determined parameters from XRD and Transmission Electron Microscopy (TEM). The results show that both coherence effects and domain wall scattering contribute significantly to peak asymmetries and diffuse intensity between (h00)/(00h) doublets. The results also show that these effects are sensitive to domain size being more pronounced in lower-order reflections. The choice of dopant directly impacts microstructural parameters. The study highlights the complexity of quantifying ferroelectric microstructures alone from diffraction data alone.
subject: Original Articles
  topic: section
subject: X-ray diffraction
  topic: keywords
subject: microstructure
  topic: keywords
subject: Crystal defects
  topic: keywords
subject: Fourier analysis
  topic: keywords
subject: Ferroelectric materials
  topic: keywords
creator: D. Camejo-González
creator: A. Penton-Madrigal
creator: A. Peláiz-Barranco
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 96
ending page: 102

Mathematical Model for Estimating Soil Redistribution Rate by Water Erosion Using The Nuclear and Isotopic FRN Technique
type: item
description: The use of nuclear techniques for the evaluation of soil water erosion is based on empirical relations to evaluate inventories of radionuclides in the soil (137Cs, 210Pb and 7Be). In applying the fallout radionuclides technique (FRN) to croplands, the most widely used model is the Mass Balance Model (MBM-II), which employs 137Cs isotope inventories (Bq m-2) to estimate soil redistribution rate. This work develops a mathematical model (MRS-2) to obtain this soil redistribution rate, yielding results comparable to those of MBM-II. The model estimates the soil redistribution rate based on areal activity density (AAD) values (Bq m-2) used in FRN techniques. This linear model is notable for its internal and external validation, providing reliable estimates of soil redistribution rate down to values of -60 t ha-1 y-1. Its use is therefore recommended.
subject: Original Articles
  topic: section
subject: water erosion
  topic: keywords
subject: soil redistribution
  topic: keywords
subject: conversion model
  topic: keywords
subject: fallout radionuclides
  topic: keywords
creator: J. L. Peralta Vital
creator: F. H. Martínez-Luzardo
creator: R. Gil-Castillo
creator: Y. Llerena-Padrón
creator: O. Díaz-Rizo
rights: Copyright (c) 2026 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2026-07-15
publication date: 2026-07-15
starting page: 13
ending page: 19

Role of Radiofrequency Power on the Crystallographic, Morphological and Optical Properties of Sputtered Aluminium Thin Films
type: item
description: Aluminum (Al) thin films are of great interest for applications in telecommunications, microelectronics, and the automotive industry, among others, due to their high conductivity, excellent optical properties and low weight. Their properties depend on the depositition technique and its parameters. In this work, the crystallographic, morphological, and optical characteristics of Al thin films grown by radio-frequency (RF) magnetron sputtering were analyzed. An aluminum target was used in an argon (Ar) atmosphere, and the effect of sputtering power on film properties was investigated. The samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and UV-Vis Spectroscopy. The crystalline quality improved with increasing power. AFM and SEM results revealed an increase in roughness, thickness, and grain size with higher sputtering power. UV-Vis spectroscopy showed lower diffuse reflectance at lower power across the 190-900 nm range. The enhancement of film properties is mostly attributed to the increased kinetic energy of sputtered species, directly related to the applied RF power.
subject: Original Articles
  topic: section
subject: Thin films
  topic: keywords
subject: Aluminium
  topic: keywords
subject: RF sputtering
  topic: keywords
creator: R. Ramos-Blazquez
creator: F. Solis-Pomar
creator: A. Fundora Cruz
creator: A. Collado-Hernádez
creator: C. García-Rodríguez
creator: M. J. Martínez-Carrion
creator: A. Fragiele
creator: A. Martínez-Huerta
creator: E. G. Pérez-Tijerina
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 124
ending page: 130

High-power Laser Prototype for Soft Tissue Surgery in Dentistry
type: item
description: The development of a high-power semiconductor laser device for soft tissue surgery in dentistry is presented. The block diagram and the elements that they include, the main technical specifications of the prototype, as well as the results obtained from the measurements carried out for its adjustment and start-up, are shown, guaranteeing its reliable operation.
subject: Original Articles
  topic: section
subject: Lasers
  topic: keywords
subject: Applications of Lasers
  topic: keywords
subject: Biomedical devices
  topic: keywords
subject: laser-assisted surgery
  topic: keywords
creator: O. Morales-Valdés
creator: P. Larrea-Cox
creator: S. Fernández-Yanes
creator: L. Hernández-Tabares
creator: G. Mesa-Pérez
creator: A. Rodríguez-Álvarez
creator: D. Ojeda-Díaz
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 109
ending page: 112

Mw-ML and MW-Mc Seismic Magnitude Scaling Relationships for Cuba
type: item
description: Earthquake catalogs typically report multiple magnitude types, which makes it difficult to perform comprehensive statistical analysis. Internationally, moment magnitude is the preferred reference scale for unification. This study establishes empirical relationships between MW and two magnitudes used in Cuba: (1) amplitude-based ML and (2) coda-duration-based MC, as computed by the National Seismological Service of Cuba for earthquakes recorded from 1998–2022. We evaluated linear and nonlinear regression models, including those accounting for uncertainties in the independent variable (ML or MC). Model parameters were estimated via standard least squares, orthogonal distance least squares, and higher-order moments regression. Using the Akaike (AIC) and Schwarz (BIC) information criteria, we identified the segmented model using orthogonal distance regression (ODR) as most recommended for both MW–ML and MW–MC relationships. These results provide a robust basis for magnitude conversions in Cuban catalog homogenization and seismicity analysis.
subject: Original Articles
  topic: section
subject: Earthquakes
  topic: keywords
subject: Earthquakes magnitudes
  topic: keywords
subject: Errors in Physics
  topic: keywords
subject: Seismicity
  topic: keywords
subject: Statistics
  topic: keywords
creator: J. L. Noas-Hernández
creator: M. N. Vega-Garriga
creator: E. D. Arango-Arias
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 113
ending page: 119

Problem-based Learning with Video Analysis: The Case of the Variable-Mass Atwood Machine
type: item
description: This study applies Problem-Based Learning (PBL) to teaching advanced mechanics in undergraduate physics, focusing on variable mass systems through the Atwood machine with chains. Using the Hmelo-Silver PBL model, a structured sequence guided students in problem analysis, hypothesis generation, self-directed study, experimentation, and reflection. The case study combined Newtonian and Lagrangian modeling with experimental validation via Tracker video analysis, enabling students to connect theoretical derivations with accessible empirical data. Results showed strong consistency between theoretical predictions and experimental measurements, despite minor discrepancies from chain oscillations, link impacts, and video resolution limitations. The approach demonstrated how low-cost tools can effectively support experimental inquiry in physics education. Beyond content knowledge, PBL fostered research-oriented skills such as autonomous planning, problem-solving, and collaborative inquiry. The proposed framework provides a replicable model for integrating abstract theory with experimental practice, strengthening active learning and advancing the role of inquiry-based methodologies in STEM curricula.
subject: Original Articles
  topic: section
subject: Teaching methods and strategies
  topic: keywords
subject: Research in Physics education
  topic: keywords
subject: Formalisms in classical mechanics
  topic: keywords
subject: Problem-based Learning
  topic: keywords
subject: Variable mass systems
  topic: keywords
creator: J. L. Saquinaula-Brito
creator: J. J. Plaza-Santillán
creator: J. D. Ortiz-Mata
creator: E. A. Lamilla-Rubio
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 87
ending page: 95

Computational Optimization of A Stochastic Model for Simulating Apoptotic Signaling
type: item
description: The development of mathematical models to simulate biological processes is essential for understanding the complexity of living systems, allowing for predictions and virtual experiments that would be difficult to carry out under real conditions. In this work, we present a mathematical model to simulate the process of apoptosis or programmed cell death, using the Gillespie algorithm. Additionally, an optimization of this model is proposed, which reduces computation time and enables the model to simulate apoptosis in the cells of a tumor under topical treatment. Results are also presented demonstrating that both models are equivalent. The optimization reduced the execution time of the simulation by two days.
subject: Original Articles
  topic: section
subject: Stochastic models
  topic: keywords
subject: Complex systems
  topic: keywords
subject: Computer modeling
  topic: keywords
subject: Monte Carlo methods
  topic: keywords
subject: Systems biology
  topic: keywords
creator: J. German-Serra
creator: N. López-Marín
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 51
ending page: 57

New Sigmoid Curves
type: item
description: S-shaped or sigmoid curves can be defined as the solutions of autonomous first-order differential equations that satisfy four conditions. Without solving the equations, we demonstrate that the solutions of the logistic family and the Smith-Birch model satisfy these conditions. We introduce two generalizations of the Smith-Birch, whose solutions are identified as S-shaped for some range of variation of the parameters. The new models introduced here predict the spread of the disease better than traditional logistic family models for time series of the cumulative number of cases for the first 61 days of the COVID-19 pandemic in some countries.
subject: Original Articles
  topic: section
subject: Complex systems modelling
  topic: keywords
subject: Sigmoid curves
  topic: keywords
subject: Growth models
  topic: keywords
subject: Data fitting
  topic: keywords
subject: Early warning
  topic: keywords
creator: M. T. Pérez-Maldonado
creator: J. Bravo-Castillero
creator: R. Mansilla
creator: O. Caballero-Pérez
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 44
ending page: 50

Demonstrative Teaching Experiment to Motivate the Study of Radioactivity with a Research Approach
type: item
description: A demonstrative experiment on radioactivity is proposed, applying a research learning approach. The experiment utilizes a radioactive source (90Sr), Geiger-Müller counters, magnets, and electromagnets. Through heuristic discussion, students are guided to discover, among other things, the presence of electrically charged particles in the studied radioactive emission. The experiment was conducted one month before the students formally began their nuclear physics course, the final topic in the Physics 3 subject (Modern Physics) for engineering students. A survey conducted during the first few minutes of the lecture introducing the topic revealed that a high percentage of students recalled the fundamental characteristics of the radioactive decay process of the isotope under study.
subject: Original Articles
  topic: section
subject: Demonstration experiments
  topic: keywords
subject: general physics
  topic: keywords
subject: Radioactive beams
  topic: keywords
subject: physics education
  topic: keywords
creator: J. B. Cruz-Arencibia
creator: J.J. Llovera-González
creator: A. D. Rodríguez-Llerena
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-12-23
publication date: 2025-12-23
starting page: 103
ending page: 108

Mathematical Treatment of the Canonical Finite State Machine for the Ising Model
type: item
description: The complete framework for the minimal deterministic automata construction of the one-dimensional Ising model is presented. The approach follows the known treatment of the Ising model as a Markov random field, where the local characteristic is usually obtained from the stochastic matrix. The problem is the inverse relation or how to get the stochastic matrix from the local characteristics given via the transfer matrix treatment. The obtained expressions allow for performing complexity-entropy analysis of particular instances of the Ising model. Two examples are discussed: the 1/2-spin nearest neighbour and next nearest neighbours Ising model.
subject: Original Articles
  topic: section
subject: Ising Model
  topic: keywords
subject: Complexity
  topic: keywords
subject: Entropy
  topic: keywords
creator: E. Estevez-Rams
creator: E. Rodríguez-Horta
creator: R. Lora-Serrano
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 3
ending page: 11

The Role of Clay Charge in The Mobility of Compensating Cations
type: item
description: The charge of clays plays an important role in the mobility of compensating cations and in swelling processes. In this work we have developed a method to generate Lithium Fluorhectorite (Li-Fh) clay models with a charge of -1.2e and a non-homogeneous charge distribution. This charge is closer to the experimentally reported value. We used this approach to study their interaction with water using Molecular Dynamics (MD) simulations. The MD simulations showed that the Li+ diffusion coefficient increases by two orders of magnitude with decreasing clay charge. Population analyses and Li+ coordination indicate a greater interaction of the cations with water molecules with decreasing clay charge, leading to a deformation in the stacking of clay layers in the 010 model. These results highlight the important influence of clay charge on cation dynamics and structural behavior, providing insight into delamination and swelling mechanisms.
subject: Original Articles
  topic: section
subject: Molecular Dynamics Calculations
  topic: keywords
subject: Diffusion in Nanoscale Solids
  topic: keywords
subject: Computer modeling and Simulation
  topic: keywords
creator: C. D. Marrero-Pérez
creator: G. Rojas-Lorenzo
creator: A. Lam
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 37
ending page: 43

Metal-Insulator Transition described by NOFT
type: item
description: The metal–insulator transition (MIT) is a fundamental phenomenon in condensed matter physics and a hallmark of strong electronic correlations. Hydrogen-based systems offer a simple yet powerful model for investigating the MIT, as their insulating behavior arises purely from electron–electron interactions. In this work, we study finite hydrogen clusters with cubic geometries using Natural Orbital Functional Theory (NOFT), a method capable of accurately describing correlated systems beyond mean-field approaches. We focus on two key signatures of the MIT: the fundamental energy gap and the harmonic average of the atomic one-particle reduced density matrix. Our results show that NOFT captures the transition from insulating to metallic behavior as the interatomic distance decreases. By extrapolating the energy gap to the thermodynamic limit, we estimate a critical distance rc ~1.2 Å, in excellent agreement with quantum Monte Carlo benchmarks. These findings demonstrate the reliability of NOFT for describing strong correlation effects in large-scale models.
subject: Original Articles
  topic: section
subject: Strongly Correlated Electrons
  topic: keywords
subject: Reduced Density Matrix Functional Theory
  topic: keywords
subject: Hydrogen Clusters
  topic: keywords
subject: Natural Orbitals
  topic: keywords
subject: Metal-Insulator Transition
  topic: keywords
creator: J. F. H. Lew-Yee
creator: M. Piris
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 30
ending page: 36

Radioactivity Levels and Radiation Hazard in Sands from Cuban Beaches
type: item
description: This study assesses the natural radioactivity levels of 226Ra, 232Th, and 40K in sand samples from six Cuban white-sand beaches to evaluate potential radiological risks. Samples were analyzed using high-resolution gamma spectrometry after a one-month equilibrium period. Activity concentrations were determined via key gamma transitions of daughter nuclides. Results show that all measured values of activity, radium equivalent (Raeq), absorbed dose rate (DR), and gamma index (Iγ) are below internationally recommended safety thresholds. La Coloma beach exhibited the highest 232Th activity, slightly exceeding the global mean, but still within safe radiological limits. The calculated gamma index values (0.04–0.52) and dose rates (3–33 nGy·h⁻¹) confirm minimal radiological risk. This work provides a radiological baseline for Cuban beach sands and supports the need for further studies in other major resort areas across the island
subject: Original Communications
  topic: section
subject: radioactivity
  topic: keywords
subject: radiation hazard
  topic: keywords
subject: beach sands
  topic: keywords
subject: Cuba
  topic: keywords
creator: G. Pérez
creator: H. Cartas
creator: A.O. Casanova
creator: O. Díaz
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 65
ending page: 66

Pyroelectric Response and Figures of Merit of Lead-Free Ferroelectric Ceramics
type: item
description: (Bi0.5Na0.5)1-xBaxTiO3 were synthetized via the conventional solid-state reaction sintering method (considering x = 16 and 18 at%) and polarized under an electric field of 2 kV/mm. The pyroelectric behaviour of the studied samples has been analysed by the static method, from the temperature dependence of the pyroelectric current. The figures of merit FV, FD, Fi and FE were investigated in a wide temperature range. The composition with x = 18 at% showed better results than that of x = 16 at% and other reported ceramic systems, especially for FV and FE parameters. A high thermal stability through the studied temperature range was obtained, which is a relevant behaviour for applications involving high-temperature sensors. The results have suggested that (Bi0.5Na0.5)1-xBaxTiO3 is a suitable candidate for pyroelectric sensors and energy harvesting applications.
subject: Original Communications
  topic: section
subject: Ferroelectrics
  topic: keywords
subject: pyroelectrics
  topic: keywords
subject: pyroelectric devices
  topic: keywords
creator: A. C. Iglesias-Jaime
creator: A. Peláiz-Barranco
creator: J.D.S. Guerra
creator: Tongqing Yang
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 61
ending page: 64

Towards the STM: The Story Behind The First Atomic Resolution Image in Cuba
type: item
description: Scanning tunneling microscopy is a widely used tool in nanoscience and nanotechnology research. This technique has the advantage of allowing the study of surface layers without damaging or destroying them and of achieving atomic resolution. Its simplicity compared to other scientific instruments has allowed different laboratories to build their own microscopes. Here we present how the STM at the University of Havana was built and how it achieved atomic resolution for the first time in Cuba.
subject: Moments of the Cuban Physics
  topic: section
subject: Laboratory experiments and apparatus
  topic: keywords
subject: History of science
  topic: keywords
subject: Scanning tunneling microscopes
  topic: keywords
creator: J. A. Martínez
creator: M. P. Hernández
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 67
ending page: 73

Photodissociation Dynamics of the Collinear Van Der Waals Complex NeBr2(B, ν=14-34)
type: item
description: We perform trajectory-based simulations of the dissociative dynamics of the collinear van der Waals complex NeBr2(B,ν) following photoexcitation to the B electronic state and for varying vibrational excitations of the dihalogen molecule in the range ν=14-34. The quantum dynamics of unimolecular decay is mapped onto a classical-like dynamics in an extended phase space. This methodology allows us to compute the time-dependent dissociation probability, intramolecular energy transfer mechanisms, and transient vibrational state distributions of the linear triatomic system, which are challenging to access experimentally using modern pump-probe spectroscopy techniques. The computed quantities can be used to refine interaction potential models at collinear geometries, which are less well characterized than the T-shaped isomer.
subject: Original Articles
  topic: section
subject: Quantum molecular dynamics
  topic: keywords
subject: Quantum trajectory method
  topic: keywords
subject: Computational physics
  topic: keywords
subject: Molecular physics
  topic: keywords
creator: C.A. Piñeiro-Moreno
creator: Ll. Uranga-Piña
creator: A. Martínez-Mesa
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2024-12-15
publication date: 2024-12-15
starting page: 88
ending page: 92

Study of the Rotation Dynamics of a Rigid Body through the accelerometer of a Mobile Device
type: item
description: The introduction of the mobile devices in the teaching of physics has gained importance in recent times due to the ample range of sensors they contain and their ability to accomplish measurements in real time. The study of the dynamics of a rigid body rotation using the accelerometer of a smart phone was tackled. The problem is a modification of the standard laboratory device consisting in a crossbeam that rotates in a horizontal plane around a vertical axis. Through an ad hoc Android application, it was possible to visualize the behavior and to measure the radial and tangential components to a linear acceleration. Moreover, the moment of inertia and the friction torque of the crossbeam was calculated. Finally, we discuss some particular cases of the main problem that shows the potential of these devices for physics teaching.
subject: Original Articles
  topic: section
subject: general physics
  topic: keywords
subject: mobile device
  topic: keywords
subject: Solid rigid body
  topic: keywords
subject: accelerometer sensor
  topic: keywords
creator: J. Rodríguez
creator: C. García
creator: E. Govea
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2024-12-15
publication date: 2024-12-15
starting page: 124
ending page: 127

Quasi-classical Dynamics of Hydrogen Molecules Trapped Inside Fullerene Cages
type: item
description: We perform molecular dynamics simulations of hydrogen molecules inside fullerene cages, incorporating quantum effects via the Feynman-Hibbs effective potential method. The distance between hydrogen atoms in the molecule is kept fixed by using the constraint dynamics algorithm. We evaluate the energetic properties and the influence of quantum effects for hydrogen molecules in fullerene cages of varying size and geometry (Cn, n=24, 28, 60, 70), and within a wide range of thermodynamics conditions (i.e., from T=130 K to T=320 K). We compute the temperature dependence of quantities such as the translational and rotational kinetic energies, the total energy and the contribution of quantum effects. It is found that quantum corrections to the total energy are significant even at room temperature. We discuss the possible influence of these properties on the hydrogen storage capacity of these materials.
subject: Original Articles
  topic: section
subject: Molecular dynamics simulations
  topic: keywords
subject: Semiclassical molecular dynamics
  topic: keywords
subject: Hydrogen storage
  topic: keywords
creator: J. A. Heredia-Kindelán
creator: L. D. Fernández-Quintana
creator: N. Halberstadt
creator: L. Uranga-Piña
creator: A. Martínez-Mesa
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 20
ending page: 25

The Two-state Diffusion Problem with Resetting
type: item
description: The concept of stochastic resetting emerged in 2011, introducing a simple modification to [15] the one-dimensional Random Walk that leads to a stationary distribution and where the first-passage time can be easily optimized. In this context, we will investigate what happens when modeling these phenomena in a framework where a Brownian particle alternates between different states. We will derive the Fokker-Planck equations of the model and analyze the behavior of the probability density of the particle positions for long times and solve the corresponding first-passage time problem. Contrasting with the two-state Brownian motion, we will observe how resetting ensures a stationary behavior in the long run leading to a finite expectation for the first-passage problem. Finally, we will demonstrate how the existence of this expectation guarantees minimum values by varying the resetting or state-change parameters.
subject: Original Articles
  topic: section
subject: Stochastic resetting
  topic: keywords
subject: double diffusivity
  topic: keywords
subject: first-passage time
  topic: keywords
subject: Fokker-Planck Equation
  topic: keywords
subject: Brownian motion
  topic: keywords
creator: J.J. Díaz-Perez
creator: R. Mulet
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2024-12-15
publication date: 2024-12-15
starting page: 93
ending page: 98

Particle Fluence Estimation for Samples Irradiated at a Long-Term Exposure Station (NICA Complex, Dubna)
type: item
description: The prototype of the Target Station for Long-Term Exposure was assembled after all detectors of BM@N Experiment. During collection of the physical data with the 124Xe54 beam of 3.8 GeV kinetic energy at BM@N, different samples were irradiated. Data was analyzed for precise determination of the intensity, the fluence and the absorbed dose for irradiated materials. The beam intensity and profile distributions were determined for each sample. From the obtained intensity, the fluence was calculated for each irradiated sample. Then, the absorbed dose of irradiated materials was be calculated. The study was performed within the ARIADNA Collaboration.
subject: Original Articles
  topic: section
subject: fluence
  topic: keywords
subject: absorbed dose
  topic: keywords
subject: high energy ion beam
  topic: keywords
subject: irradiated samples
  topic: keywords
creator: M. Pérez-Tápanes
creator: N. Pukhaeva
creator: N. Zamiatin
creator: O. Diaz
creator: D. Chemezov
rights: Copyright (c) 2025 Cuban Physical Society & Faculty of Physics of the University of Havana https://creativecommons.org/licenses/by-nc/4.0
date: 2025-07-15
publication date: 2025-07-15
starting page: 26
ending page: 29