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Se presenta una carta al editor acerca del artículo "La cultura científica y la desfactualización de la enseñanza de la física" de F.A. Horta Rangel y A. González Arias, y publicado originalmente en volumen 29, número 2, de esta revista.

This paper aims at introducing the Kalman's filter to science and engineering undergraduate students by means of a simple experiment. It consists in the free fall of an umbrella equipped with a mobile phone from a height of a few-meters. Using the data provided by the accelerometer embedded in the phone, it is shown that the use of the Kalman filter allows determining the terminal velocity without the need of performing multiple repetitions of the experiment. Three methods for finding the covariance matrix of the control vector are tested, and their results are compared. [ABSTRACT FROM AUTHOR]

The article summarizes the details of the XVI Symposium of the Cuban Society of Physics, which took place at the University of Havana from April 8th to 11th, 2024. The symposium had the participation of 150 attendees and 152 papers were presented in different formats. The collaboration of the Cuban Society of Physics with related international associations, such as the American Physical Society (APS), is highlighted. Additionally, information is provided about the XIV congress of the Cuban Society of Physics, where the situation of physics education in the country, which has consistently worsened, was discussed. The "Manuel F. Gran" National Physics Award was presented to Dr. Cs. Ernesto Altshuler Álvarez for his contribution to the development of physics in Cuba. [Extracted from the article]

Molecular simulations have been useful tools in the research of the host-guest interactions in clays. It has been possible due to the implementation of appropriate force fields to simulate clays, as the CLAYFF. It uses the SPC potential to reproduce the water interactions. However, this is a limitation when combined with the most commonly used organic force fields, AMBER and CHARMM, that use the TIP3P water potential. In the present paper, molecular dynamics simulations of the water-clay model system was done using a combination of CLAYFF with SPC and TIP3P water force fields in order to validate the use of TIP3P water model with the CLAYFF. The results shows very good agreement between radial distribution functions and diffusion coefficients using both water potentials combined with CLAYFF. This fact opens the possibility of using this clay force field with the CHARMM and AMBER force fields. [ABSTRACT FROM AUTHOR]

In the wake of the 2022 Nobel Prize in Physics, this paper recounts the fundamental milestones related to some problems in the foundations of Quantum Physics. After a brief historical journey, the superposition of states, the random character of measurements, quantum encryption and entanglement and the phenomenon of quantum teleportation are discussed. The meaning of the Einstein-Podolski-Rosen paradox and Bell's theorem are also analyzed. Some of the experiments carried out by the 2022 laureates aimed at analyzing the fulfillment or violation of Bell's inequality and the resolution of the conflict between local hidden variables theory and Quantum Physics are described. Finally, some of the most relevant interpretations of Quantum Physics are discussed, such as those of multiple universes, Bohn's mechanics and, of course, the Copenhagen interpretation. [ABSTRACT FROM AUTHOR]

In this paper we present the first research results of the optical station at the Russian-Cuban observatory. The observatory includes two stations - optical and geodynamical, created by The Institute of Geophysics and Astronomy of Cuba in collaboration with The Institute of Astronomy of The Russian Academy of Sciences and the Institute of Applied Mathematics of The Russian Academy of Sciences. The main instrument of the optical station is a 20-cm wide-field robotic telescope with a CCD camera equipped with the wheel of photometric filters. We present the first photometric researches of active stars V410 Tau, FR Cnc and FK Com obtained in the late 2021 and early 2022. [ABSTRACT FROM AUTHOR]

Lead-based piezoelectric compounds are used in a wide applications range spanning from sensors to transducers. However, these materials are environmentally-aggressive, so these must be replaced by using lead-free compounds. This paper presents the study on the electromechanical behavior and the main piezoelectric parameters of five piezoelectric ceramic compositions within the (Bi0.5Na0.5)1-xBaxTirO3family, where x = 8; 10; 12; 16; 18 at %. The samples have been prepared by using the standard solid-state reaction method and then polarized under an electric field of 2 kV/mm for a temperature lower than that of the phase's transition temperature. Our results revealed d33 values higher than 120 pC/N for x = 8; 10; 12at %, better than those for lead-based compounds. There were also obtained d33, d31 and g31 values higher than those reported in the literature for a large number of lead-free systems. [ABSTRACT FROM AUTHOR]

In this paper, we present an architectural and electrical design of an integrated A/D converter configuration, based on Δ∑ modulation, for data acquisition from an ISFET (Ion Sensitive Field Effect Transistor) microsensor, applied to the development of a Smart ISFET. This A/D architecture in continuous-time, incorporates the microsensor as a component of the integrated circuit, together with the required electronics for the automatic correction of the ISFET's offset fulfilling the necessary requirements for the development of a portable device. [ABSTRACT FROM AUTHOR]

This paper has academic nature, nevertheless it is an application from [9] that we think can be interesting to students and instructors of undergraduate level of physics. With low level of geometric and computational techniques the readers can reproduce the results of the present paper. The most important thing is that these results clearly show that it is not enough take numerical measures of the orbits of the bodies to decide which are the real equations and laws that govern them. We present an approximation of the Kepler's ellipse of the planets' trajectory by circular arcs, which is quasi-equivalent; that is: we present the approximation of the Kepler's ellipse εb by the eight-centered oval Oεb having the same center, axes, vertices, perimeter length and curvature at the vertices as εb, and also having practically negligible difference with respect to the surface area of εb, and also having barely distinguishable deformation error in relation to εb. [ABSTRACT FROM AUTHOR]

The article reports on three scientific events that took place in Cuba. The first one was the "Interciencia" Fair at the Institute of Cybernetics, Mathematics, and Physics (ICIMAF), where talks and demonstrations were offered in areas of science such as Physics, Cosmology, and Artificial Intelligence. The second event was the First Meeting of Students of Natural, Exact, and Technical Sciences, where scientific papers by students from the Faculty of Physics at the University of Havana and other educational centers were presented. The third event was the seminar "Nanos: Synthesis, Characterization, and Toxicological Evaluations," organized by the Center for Technological Applications and Nuclear Development (CEADEN), where aspects related to carbon nanomaterials and their biomedical applications were addressed. Additionally, the signing of a Memorandum of Agreement for Cooperation between the Cuban Journal of Physics and the Latin American Association of Medical Physics (ALFM) is highlighted to strengthen the ties between both institutions. [Extracted from the article]

The XV Symposium and XIII Congress of the Cuban Society of Physics took place at the University of Havana from March 9th to 13th, 2020. The event featured the participation of Cuban and foreign specialists, and a total of 217 papers were presented. During the Congress, the work of the Cuban Society of Physics in strengthening relationships with related associations was highlighted, and the society's 40th anniversary was celebrated. In addition, organizations and individuals who have contributed to the development of physics in Cuba were recognized. The Cuban Society of Physics has also organized the Latin American University Physics Olympiad since 2017 and publishes the Cuban Journal of Physics. Awards were presented to outstanding professors during the congress, and discussions were held on the current situation of physics in Cuba. [Extracted from the article]

The prolongation of a project to create an optical observation station in the frame of the Russian-Cuban Observatory (RCO) is described. The paper reports some important elements regarding the creation of the RCO optical station layout in Havana. The equipment and some scientific observation projects planned to be done using the layout are discussed. The main instrument of the optical station layout is a wide-field 20 cm robotic telescope. The observational project program includes both fundamental and applied tasks. It is argued that the layout itself could be used as an independent observatory because of its ability to solve universal observational tasks and to serve as a real segment of a global optical telescope network. [ABSTRACT FROM AUTHOR]

This paper deals with new approaches towards the Jablonski diagram and the ¿ state concepts from the viewpoint of the relationship between electronic deactivation and vibrational relaxation processes in electronically excited species. In both concepts, vibrational relaxation precedes the electronic deactivation processesofexcited molecules. The experimental data accumulated up to the present using mainly time-resolved luminescence and transient absorption spectroscopy from the field of the photophysics of transition metal compounds and different organic molecules have clearly demonstrated that even spin-forbidden electronic deactivations are in many cases faster processes that vibrational relaxation. It means that the classical Jablonski diagram indicating that electronic deactivation processes occur after vibrational relaxation should be modified. In general, electronic deactivations occur from vibrationally higher states. [ABSTRACT FROM AUTHOR]

Gender discrimination is an universal phenomenon, and although in recent decades important advances have been observed in women's education, the application of equality legislation, changes in family roles and the challenge of traditional gender norms, the progress has not been the same in all regions. In science, gender difference has been decreasing, but this does notmean thatwomen have opportunities to achieve academic performance and leadership position sequal to that of men, particularly in science and technology. Cuba is not free from the problem, and although its progress is remarkable, there is still a long way to go in this area. The present paper analyzes the presence of Cuban women in science, and particularly in physics, where male presence has been traditionally dominant. [ABSTRACT FROM AUTHOR]

Physics teaching in the basic formation of engineers in Cuba has evolved through different stages since the 1960's until the present. Each stage has been marked by changes in the plans of study, which have been modified substantially both in terms of contents and of teaching hours. This paper presents a brief summary of these changes, the current state of the Physics programs, and warns about the challenges to be faced nowadays in order to guarantee a solid basic formation of the future engineers in connection with the physical foundations of present and future technologies. [ABSTRACT FROM AUTHOR]

In this paper, we propose to numerically simulate the spatial-temporal (axial and radial) evolution of the density of certain nitrogen oxides present in the gaseous mixture: 74 % N2, 10 % O2, 8% H2O and 8 % CO2 which is subject to a negative corona discharge at room temperature and atmospheric pressure. We study the influence of the reduced electric field E/n (E electric field, n the density) on the chemical kinetics of this mixture. The gas chemistry takes into account 18 species such as: the radicals N, O, H, OH, the ground state molecules N2, O2, H2O, CO2, O3, H2, HNO3, the nitrogen oxides NO, N2O, NO2, NO3, N2 O5, metastable species N(2D) and the electrons e-, reacting with one another 80 selected chemical reactions. The purpose of this simulation is to complete these studies by analyzing different plasma species under three selected values of reduced electric fields: 100, 200 and 300 Td. The results obtained show an evolution closely related to the reduced electric field. [ABSTRACT FROM AUTHOR]

The main objective of this study is to understand the time evolution of the nitrogen dioxide specie in N2 /O2 /H2 O/CO2 mixture gas induced by negative corona discharge at atmospheric pressure. The fundamental chemistry governing NO2 evolution developed in this paper is based on a full set of processes regrouped in one hundred selected chemical reactions involving twenty molecular, excited, atomic, and charged species. The density was calculated using the continuity equation without the diffusion and convective terms. In literature it has generally been emphasized that certain radicals N, O, and O3 influence the NO2 conversion. In this study, we complete them by analysing others species such as negative ions and radicals. The results show that the environmental condition rate of NO2 is well affected by the increase of reduced electric field and concentration. [ABSTRACT FROM AUTHOR]

In this paper we review the system made up by two blocks connected by a string over a smooth pulley with variable tension. One block lies on an horizontal surface and the another block is hanging vertically. We carry out a complete and systematic analysis for the tension of the string as function of the angle θ and the horizontal distance x, at static equilibrium. We find a symmetry-like that corresponds to two different configurations with the same tension and obtain the relationship that must satisfy two angles or two horizontal distances to obtain equal tension. [ABSTRACT FROM AUTHOR]

Cancer diagnosis by non-invasive techniques is subject of cutting-edge research in biomedical field. This paper presents experimental results of absorption and reflectance spectroscopy for ex-vivo assessment of cancerous and pre-cancerous cervical tissue. Results show promising and provide a methodology to be integrated with the standard papsmear or screening and tests aimed at preventing deaths due to cervical cancer. [ABSTRACT FROM AUTHOR]

Radiometry, the measurement of the energy of electromagnetic waves (EMW) is one of the most important fields of experimental physics, reaching all Natural Sciences. Photobiology, for instance, is based in the quantification of the action of light on biological systems. The interaction of EMW with photosensitive cells (an eye in a mammalian, for instance) is key in the understanding of the interaction of living beings with their environment. A human eye is sensitive only to a fraction of the EM spectrum, ranging approximately from 400 to 760 nm. Eye's sensitivity varies with wavelength, growing from 400 to 555 nm, where it reaches a maximum, then monotonically decreasing up to 760 nm, where it reaches a value of zero. That is the reason of the existence of two different (though related) system of units. In one hand the radiometric or energetic units, characterizing the energy of a light beam and, on the other, the photometric units, characterizing the action of EMW upon a human eye. Both systems are often confused, and the extent and exact definition of their magnitudes misinterpreted, without a precise relation among related units of both systems. This is so even in some textbooks. In the present contribution we will try to clarify all these topics. This paper could be useful in courses of Optics, Ophthalmic Optics, Metrology and design of illuminating systems. [ABSTRACT FROM AUTHOR]

In this paper, nano-CuO films, fabricated using the simple "doctor blade" technique, are studied as photoelectrodes in a two-electrode PEC cell for water photolysis. SEM analysis confirm the nanometric size of film grains and the photoelectrode porosity. The photocurrent behavior is studied, particularly, photocurrent transients for non-assisted and assisted water photolysis. Existing defects acting as carrier traps explain the different transient behaviors found. The existence of defects is explored using X-ray diffraction technique and the Williamson-Hall method. [ABSTRACT FROM AUTHOR]

Smartphones may be seen as miniature toolboxes to perform Physics experiments. In this paper, we present three different experimental optics designs mainly based on the light meter of a smartphone. One is aimed at the precise study of Malus law and other effects associated to linearly polarized light, the second allows quantifying the energy distribution of diffraction or interference patterns projected on a screen, and the third demonstrates the so-called inverse square law obeyed by the illumination from a point-like source. These experiments allow to quantitatively demonstrate three fundamental laws of optics using quite inexpensive equipment. [ABSTRACT FROM AUTHOR]

After a brief presentation of the Physics Nobel Prize 2018 and its winners, the paper is divided into two main parts. In the first one, the foundations of the optical tweezers are described, and a few of its applications are reviewed in some detail. The second part of the article discusses the physics beyond the technique for obtaining ultrashort, powerful laser pulses, and some of its applications are mentioned. [ABSTRACT FROM AUTHOR]

In previous papers it has been shown that the presence of negative-norm states or negative-frequency solutions is indispensable for a fully covariant quantization (Krein space quantization) of the minimally coupled free scalar field in de Sitter spacetime. The new method of quantization has been extended to free boson fields (charged scalar field, massive and massless vector field) in Minkowski spacetime. In this paper, quantization of free spinor field is reformulated in generalized Krein space. The presence of unphysical negative-frequency states plays the role of an automatic renormalization tool for the theory. [ABSTRACT FROM AUTHOR]

Archaeological American mirrors are common findings and the images obtained with them are often described by archaeologists as possessing high quality. However, photographs attesting this fact are rare, if any. To the best of my knowledge, only two papers show that quality concerning the Olmeca culture, and only one of them mentions the pre-Inca cultures case. Certainly more images are needed to increase awareness of the importance of the existence of sophisticated imaging elements, particularly when evaluating the cultural degree of the pre-Columbian civilizations. In this paper we show images made in three museums in Lima, Peru, by means of mirrors and the lens action on a necklace element. [ABSTRACT FROM AUTHOR]

The article reports on two scientific events in Cuba. The first is the "Interciencia" Fair that took place at the Institute of Cybernetics, Mathematics, and Physics (ICIMAF) on December 10, 2022, where talks and demonstrations were offered in areas of science such as Physics, Cosmology, and Artificial Intelligence. The second event is the First Meeting of Students of Natural, Exact, and Technical Sciences, which took place within the international convention "SABER UH" at the University of Havana from May 29 to June 2, 2023. In this meeting, scientific papers were presented by students from the Faculty of Physics of the University of Havana, Instec, and other educational centers. Additionally, a seminar on nanoscience organized by the Center for Technological Applications and Nuclear Development (CEADEN) on June 19, 2023, is mentioned, where topics related to the synthesis, characterization, and toxicological evaluations of carbon nanomaterials were addressed. [Extracted from the article]

The Institute of Cybernetics, Mathematics, and Physics (ICIMAF) held the "Interciencia" Fair on December 10, 2022, where talks and demonstrations were offered in areas of science such as Physics, Cosmology, and Artificial Intelligence. The event had substantial participation from pre-university students. Additionally, the First Meeting of Students of Natural, Exact, and Technical Sciences was held at the University of Havana, where scientific papers from the Faculty of Physics and other educational centers were presented. A seminar on nanoscience was also held at the Center for Technological Applications and Nuclear Development (CEADEN), addressing topics such as the synthesis and characterization of carbon nanomaterials and their biomedical applications. [Extracted from the article]

Many of the drums played all over the world are circular in shape. There are many practical reasons for the instrument makers to choose a circular shape for the drums. Apart from practical side, there are some scientific bases for the circular shape of drums. This paper investigates the physics behind the circular shape of the drums. [ABSTRACT FROM AUTHOR]

During the World War I, the German army showed a great armament power, designing weapons that go beyond to the ever known technological and physical limits at that time. Among these, the most remarkable gun was the Wilhemgeschutze, known as Paris gun. It surpassed almost three times the range of the best cannons of the time, and for the first time is reached the stratosphere by a projectile. In this paper, we use the reported data of the gun during the bombard to Paris, to develop a mathematical and computational model, that describes the trajectory of a Paris gun projectile. The model considers the drag force, gravity, centrifugal force and Coriolis effect. [ABSTRACT FROM AUTHOR]

In this paper, we design a system of two symmetrical containers communicated by an aperture, in which a granular gas of glass spheres is created by shaking laterally the whole system in a planetary mill. If the aperture consists in a symmetrical hole, the two halves end up with the same number of grains after some time when initially all particles are into in one of the containers. However, when a funnel-like aperture is used, a robust symmetry breaking is induced: if all the grains are originally deposited in the container facing the wide side 95% of the grains pass to the opposite side in a relatively small time. [ABSTRACT FROM AUTHOR]

In the course of General Physics it is possible to find the problem related to the study of the motion of bodies in a liquid when their densities are greater than that of the liquid. A problem not found in the bibliography consulted is: What depth will be obtained for an sphere when it falls freely from a height H above the free surface, if its density is less than that of the liquid? To carry out the study of this problem, a theoretical model was applied and an analytical solution was found to this depth. In addition, an experiment was designed based in the video analysis technique, using Tracker for Windows to know the real depth obtained. The main goal of this paper is to estimate the energy interchanged in the impact of the sphere on the surface linking both results. [ABSTRACT FROM AUTHOR]

The red blood cells (RBCs) have a critical role in order to understand the properties of blood in a high confinement regime. Thus, the ability of RBCs to change the shape allows them to flowing through small microcapillaries in the order of 10 µm of diameter, according to the membrane viscoelastic properties, with a complex non-linear blood flow behavior. In the previously mentioned conditions it is very important to take into account that the inter-cells hydrodynamical interaction can be critically important in order to consider the effect of solvent media like an indirect interaction transmission media. In the bibliography consulted were shown the dependence of the confinement and the flow ratio on the RBCs shape and on the length of perturbation in the surrounding flow for the case of single vesicle simulation, but the effects of closed RBCs and it dynamics behavior were omitted. In the present paper, we use the length of perturbation as a critical parameter to estimate the hydrodynamics interacting range. Subsequently, simulations in a system with two RBCs were used to study the inter-cells hydrodynamic interaction, a two-dimensional reduced model is used. The RBC was modeled as a vesicle formed by a ring of interacting particles. The solvent-solvent and solvent-RBC particles interactions were computed by Multiparticle Collision Dynamics mesoscale computational technique. Here we propose a general hydrodynamic interaction model description including the relative cell-cell distance, velocity, flow and confinement regime. As result of simulations a stochastic exponential decay hydrodynamic force was observed, when the cell-cell distance is near to the double of lengths of perturbation. [ABSTRACT FROM AUTHOR]

Since 2013, five editions of the University Physics Olympics have taken held in Cuba, with participation of Latin American students in the last two. In this paper we review the different topics approached by the problems proposed in the Olympics, as well as the performance of the competitors, for each Olympiad and academic year. The topics were divided into three types: traditional problems, problems related to current science, and unusual problems. The results allow making a comparison of the performance of the students depending on the type of problems and academic year. [ABSTRACT FROM AUTHOR]

The main features of ozone are reviewed. Its protecting role in the stratosphere, as a polluting agent in the troposphere and essential ingredient in unproven therapies. The following elements are discussed in detail: ozone in the stratosphere and troposphere; as a polluting agent; synthesis, storage, measurement and disinfectant capacity; Evidence-Based Medicine (MBE) and ozone therapies; ozone in Mexico and Cuba. Stratospheric ozone protects animal and vegetal life from ultraviolet solar radiation, while the tropospheric is an active pollutant, harmful to health. In spite of the bulky amount of papers published on the subject, and in agreement with present criteria on clinical trials and the MBE, there are no proofs recognized by the scientific community, nor valid theoretical basis, endorsing the efficacy of ozone as a drug. [ABSTRACT FROM AUTHOR]

The spectacular and unprecedented rise of so-called perovskite solar cells (PSCs) in conversion efficiency with low-cost manufacturing processes has grabbed the attention of the scientific community in the field of photovoltaics during the last four years. The inclusion of perovskite type absorber materials, typically CHgNHgPblg, has been the key factor for the development of this emerging technology that has created great of expectations. However, many poorly understood aspects of its operating modes still need convincing explanations. This paper provides a brief introduction to the structure, materials and characteristics of PSCs. In addition, some remarks about the stability of these devices are provided and the state-of-the-art of several subjects of interest is discussed, such as the hysteresis phenomenon of current-voltage curves. [ABSTRACT FROM AUTHOR]

The exact solution of the propagation of light in turbid media is possible only in very simple problems. In almost all practical cases numerical methods are mandatory. In this paper we calculate the absorbance of light in tumoral tissue using Monte Carlo (MC) simulation in order to optimize the execution time of several parallel algorithms for Graphic Processing Units (GPU) and a serial code running on the Central Processing Unit (CPU) for 106 to 1010 photon packets. The plots of absorbance versus time and tissue depth are presented, showing that the precision of the methods depend on the number of photons and it is algorithm independent. The implementation of MC algorithms using GPU have shown that simulations may be 300 times faster than on a CPU providing an effective time framework to study complex systems. [ABSTRACT FROM AUTHOR]

In this paper, we study the effect of AC electric field on the onset of electrohydrodynamic instability in a viscoelastic fluid layer saturating a porous medium caused by dielectrophoretic force due to variation in the dielectric constant with temperature. Walters' (model B') fluid model is used to describe the behaviour of a viscoelastic dielectric fluid and for porous medium, Darcy model is employed. The fluid layer is induced by the dielectrophoretic force due to the variation of dielectric constant with temperature. We derive the dispersion relation describing the influence of viscoelasticity, Darcy number and AC electric field by applying linear stability theory and normal mode analysis method. It is observed that Walters' (model B') fluid behaves like an ordinary Newtonian fluid in the stationary convection whereas Darcy number and AC electric field have destabilizing effect on the stationary convection. The present results are in good agreement with the earlier published results. [ABSTRACT FROM AUTHOR]

The article titled "II Workshop on the Teaching of Basic Sciences" reports on a workshop held at the Technological University of Havana "José Antonio Echeverría" in Cuba. The objective of the workshop was to promote exchange and scientific debate on the training in basic sciences for engineers and architects, in the context of the challenges of the 2030 Agenda. 166 delegates participated, including representatives from Peru, Ecuador, Mexico, Brazil, Spain, and Italy. During the event, conferences were held and papers related to the teaching of physics, mathematics, social sciences, engineering graphics, and languages were presented. [Extracted from the article]

Desde el curso 2009-2010 se aplica una experiencia con los estudiantes de onceno grado interesados en cursar carreras de Matemática, Física, Química y Ciencias Biológicas, como parte de los esfuerzos que se realizan para elevar el nivel de entrada exigido por la enseñanza superior y mejorar los índices de acceso y permanencia en estas carreras. Estos estudiantes son seleccionados de acuerdo a los resultados obtenidos en los llamados "exámenes de requisitos adicionales" establecidos por cada facultad universitaria, para cursar el duodécimo grado en la universidad bajo la dirección de profesores universitarios. En este artículo se explican algunas de las acciones realizadas en la enseñanza de la Física con estos estudiantes en el caso de la Universidad de La Habana, dirigidas a garantizar una asimilación más eficiente de los conceptos, leyes y teorías de la asignatura, una mayor independencia en su actuación, un desarrollo superior de sus habilidades prácticas e intelectuales y la elevación de su interés por la Física. Since the academic year 2009-2010, a new plan has been applied to 11th grade students who are interested in pursuing higher level education in Mathematics, Physics, Chemistry and Biological Sciences, as an effort to increase the knowledge demanded by the university level, and to improve the indices of access and permanence in the careers mentioned above. Based on their performance in the "additional requisites" exams established by the higher education institutions, these students are selected to take the 12th grade at the universities, under the guidance of university staff. In this paper we explain some of the actions taken on these students at the University of Havana in order to improve their learning of the concepts, laws and theories of Physics, to increase their independence, to develop their practical and intellectual abilities, and to raise their interest in Physics. [ABSTRACT FROM AUTHOR]

At present the laser diodes used in optical fiber communications systems are based on GaInPAs. These lasers have a bad thermal performance and promising substitutes are GaInNAs lasers. In this paper a study of in_uence of the ridge height on the temperature distribution in GaInNAs laser diodes is presented. To find the temperature distribution the heat conduction equation was solved using the Finite Difference Method and a two-dimensional model of heat flow. The simulation was performed in Mathematica 7.0 varying: the length of the diode, the amount of wells in the active zone and the height of the ridge contact. The thermal resistance (Rt) of the devices was calculated and compared with experimental results reported by other authors, obtaining good agreement.Our results suggest the potential of GaInNAs lasers. [ABSTRACT FROM AUTHOR]

A mechanism to describe the apoptosis process at mesoscopic level through p53 is proposed in this paper. A deterministic model given by three differential equations is deduced from the mesoscopic approach, which exhibits sustained oscillations caused by a supercritical Andronov-Hopf bifurcation. Taking as hypothesis that the p53 sustained oscillation is the fundamental mechanism for apoptosis regulation; the model predicts that it is necessary a strict control of p53 to stimulated it, which is an important consideration to established new therapy strategy to fight cancer. [ABSTRACT FROM AUTHOR]

Climatic changes are not an exclusively terrestrial phenomenon. Evidences of changes exist in climatic patterns in other planets of the Solar System. The complexity of global climate changes on Earth requires a multidisciplinary approach due to different factors and concomitant contributing phenomenology. In particular, purely astronomical phenomena have had an incidence in the variability of the Earth climate and weather. This paper resumes some of the evidences that point toward a relationship between solar activity and climatic changes occurred on our planet. [ABSTRACT FROM AUTHOR]

In this paper are exposed the didactic actions that were implemented in order to improve the way in which students carry out laboratory practices of Electromagnetism. For this experimental study were selected different physical processes of the great concern for Computer Engineers in formation. To support the preparation, performance, and valuation of the results in the laboratory practices a website was created with simulations that approach to the content of the real experiment to carry out, and which symbols agree favorably with the learning styles of the same ones. This study was developed during the academic period 2007-2010. The progress reached by the learners was verified concerning the tools and accessories selection, oral explanation of the theoretical referents, operation performance time spent, technological tool employment, and the communication of aftermath. [ABSTRACT FROM AUTHOR]