2025-12-23
E. Altshuler
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.
2025-12-23
D. Camejo-González, A. Penton-Madrigal, A. Peláiz-Barranco
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 Pb 0.92 Ln 0.08 TiO 3 (Ln 3+ = La 3+ , Dy 3+ ). 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.
2025-12-23
J. B. Cruz-Arencibia, J.J. Llovera-González, A. D. Rodríguez-Llerena
A demonstrative experiment on radioactivity is proposed, applying a research learning approach. The experiment utilizes a radioactive source ( 90 Sr), 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.
2025-12-23
R. Ramos-Blazquez, F. Solis-Pomar, A. Fundora Cruz, A. Collado-Hernádez, C. García-Rodríguez, M. J. Martínez-Carrion, A. Fragiele, A. Martínez-Huerta, E. G. Pérez-Tijerina
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.
2025-12-23
V. V. Ivchenko
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.
2025-12-23
J. A. Martínez, K. Valdiviés-Cruz, C. R. Milian-Pila
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 40 th anniversary. We analyze the main research results achieved during these 40 years, as well as an study of its historical performance.
2025-07-15
G. Pérez, H. Cartas, A.O. Casanova, O. Díaz
This study assesses the natural radioactivity levels of 226 Ra, 232 Th, and 40 K 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 (R aeq ), absorbed dose rate (D R ), and gamma index (I γ ) are below internationally recommended safety thresholds. La Coloma beach exhibited the highest 232 Th 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
2025-07-15
H. Reborido, R. Machado-García, D. A. Cascaret-Carmenaty, O. Quesada-Rodríguez, P. Muné
This study presents a simplified experimental method for evaluating the electro-mechanical behavior of activated carbons derived from agro-industrial residues such as sugarcane bagasse, coconut shells, peanut hulls, and rice husks. Using a two-point electrical measurement under controlled uniaxial pressure, we introduce and analyze the parameter ρm/ρ, which shows a strong linear correlation with pressure across all samples. The effective conductivity (σₑ) is modeled using an effective-medium approximation, revealing two competing effects of pressure: improved grain contact at low pressures and grain fracture at high pressures. The derived expression for σₑ(P) incorporates four key parameters that act as a fingerprint for each material. Experimental results confirm the model's predictive capability and highlight the influence of material composition, notably SiO₂ content, on conductivity. This approach provides a reliable, low-cost tool for preliminary assessment of the textural and conductive properties of activated carbons, with potential implications for their optimization in electrical applications.
2025-07-15
M. Pérez-Tápanes, N. Pukhaeva, N. Zamiatin, O. Diaz, D. Chemezov
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 124 Xe 54 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.
2025-07-15
E. Estevez-Rams, E. Rodríguez-Horta, R. Lora-Serrano
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.
2024-12-15
J.J. Díaz-Perez, R. Mulet
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.