ESTIMATION OF THE REAL AREA OF AU NANOPARTICLES OVER HOPG USING ELECTROCHEMICAL TECHNIQUES

The metallic electrodes show a high affinity for the electroadsorption processes of hydrogen and/or oxygen in acid solutions, so it is possible to characterize them by electrochemical techniques. In the present work the electroreduction of oxygenated species will be used to estimate the real areas of the electrodes designed with Au nanostructures in HOPG at different times of deposition. The results allow to conclude that Au nanostructures in HOPG can reach important electroactive areas. That is to say that despite their nanometric sizes they have a great capacity to experience the transfer of charge.

SELECTION OF POWER LINE COMMUNICATIONS PROTOCOL APPLIED TO A WIND TURBINE UNDER SEVERE CLIMATE CONDITIONS

The main purpose of this paper is to study the preliminary selection of one or more Power Line Communications protocols or standards, to be used in a full duplex communication between a wind turbine and a command center powered by this wind turbine. This situation considers that the wind turbine is located in an isolated area in the Patagonia Austral region, working under severe climate conditions.

QUANTITATIVE ANALYSIS OF CARDIAC PLANAR SPECT IMAGES OF 99mTC-MIBI RADIOPHARMACEUTICAL

In this work 99mTc-MIBI cardiac scintigraphs are quantitively analyzed with the aim to determine the radiopharmaceutical uptake in the heart (organ of interest) and in the liver. The impact of the radioactivity distribution in the diagnostic quality of the images is discussed.

ELECTRICAL POTENTIAL BETWEEN NON-PARALLEL FLAT ELECTRODES – SIMULATION OF A CELL USED WITH TOMATO

The equipotential lines of the field generated by the cell used in dielectric measurements of whole fruit tomato are plotted. This cell consists of two inclined electrodes, at inverse potentials, and is an adaptation made in the Dielectric Laboratory of the cell used by Varlan-Sansen. To obtain the graphs, the Laplace equation was solved by finite differences and a program in Fortran language was written, which performs the calculations by numerical iteration. The field generated by the cell at different electrode separation distances was analyzed.

REACTION OF OXYGEN REDUCTION ON THE SURFACE OF AU ON TI WITH OXIDEFORMED POTENTIODYNAMICALLY BEFORE AND AFTER THE DEPOSITION OF AU

One of the most important reactions for electrochemical science and technology is the electrocatalytic reduction ofoxygen. It is particularly relevant in fuel cells because it is slow to react and requires high overpotentials. This workaims to study electrodes with deposits of Au on Ti obtained by electrodeposition. The substrates have undergone po-tentiodynamic growths of oxides before deposition for some electrodes and after deposition for other electrodes understudy, at different final potentials. Both procedures resulted in the formation of a composite Au layer on the Ti surface.The electrochemical behavior of these composite layers was examined in a 0.01 M HClO4solution, both oxygen-freeand oxygen-saturated, and compared with the behavior of Ti as a target, using the cyclic voltammetry technique. In thepotential region of the oxygen reduction reaction (RRO), the Au layer on the Ti obtained by first performing the Audeposition and then the growth of the anode oxide showed a better response, not only in the onset potential of the RRO,but also in the current densities. In all cases the voltammetry curves of the Au and TiO2 composite layers were similarto those shown by the Au polycrystalline.

SELF-MIXING LASER VIBROMETER WITHE RESOLUTION IN THE MICRO AND NANO METERS SCALE

We present the development of an interferometer capable of making contactless measurements of vibrations. The resultsshow the we achieve micro- and/or nano-metric measurements without the stabilization of the laser. While there aremultiple techniques to achieve this objective, in this case we use a method whose main virtue is the low componentcount and the self-alignment capacity. The method is based on the optical feedback effect in a laser diode which relieson the use of an internal reference for calibration.

PHOTOPHYSICAL AND PHOTOCHEMICAL SYSTEMS WITH SEMICONDUCTORS FOR THE CONVERSION OF SOLAR ENERGY. A REVIEW

Electrochemical energy sources are an alternative to replace technology based on the burning of fossil fuels. In an elec-trochemical system the potential drop spreads over a very narrow region at an interphase, creating high electric fields.So, there are good technological reasons to study semiconductor / electrolyte interphases. Currently, one of the ways touse renewable resources is through photovoltaic technology that directly converts solar radiation into electrical energy.This technology is manufactured from semiconductors, generally silicon, following an extremely careful and expensivemanufacturing procedure. An option for photovoltaic devices is photoelectrochemical cells.These cells are made bythe contact of a semiconductor electrode with a solution, which can be easily prepared and offers the possibility oflow-cost manufacturing. Understanding how these devices work requires knowledge of the characteristics of semicon-ductors and how these materials behave in contact with an electrolytic solution and under illumination by sunlight. Thepresent work describes, through an updated review, the principles and applications of semiconductor electrodes as themain components in a photoelectrochemical solar cell (PEC), to carry out chemical reactions of technological interest.In addition, the elements that are required for the improvement in the performance and construction of the PEC are discussed.

SELF-REGULATED LEARNING IN ENGINEERING STUDENTS: STRATEGIES FOR PEDAGOGICAL RESOURCE

This paper presents some findings of the investigation "Self-regulated learning in engineering students of the Army Engineering Faculty (FIE)". The central theoretical contributions on the “self-regulation of learning” comes from theconceptual approaches of Zimmerman and Pintrich since they allow the understanding of the processes that takes placein the control of: thoughts, feelings, motivations and actions for the achievement of the learning objectives.It was found that to achieve this self-regulation in their learning, the students in this sample developed strategies throughwhich they manage and internalize resources from the academic environment. They are grouped into two large catego-ries: group study and the use of elements of the environment. The dynamics of conformation and functioning of work incollaborative study teams are similar among students. In addition, they describe the progressive use of elements of theinstitutional environment: study spaces, materials, technologies, institutional devices and also codes and dynamics ofsocial interaction typical of this faculty. The achievement of self-regulation implies the progressive incorporation of theresources of the academic context and this is a process that demands time and effort from the student. The acquisitionof self-regulation is evidence of the solid construction of the student ́s craft and a successful educational affiliation tothe university context.

STABILITY OF ALFVEN WINGS IN HMHD

A conducting source moving uniformly through a magnetized plasma generates, among a variety of perturbations,Alfvén waves. Alfvén waves can build up structures in the plasma called Alfvén wings. The wings have been detec-ted and measured in many solar system bodies, and their existence have been theoretically proved also. Under certainconditions, Hall and electronic pressure must be taken into account in the Ohm’s law and so one gets Hall Magne-tohydrodynamics (HMHD). In spite of Sallago and Platzeck have shown the existence of Alfvén wings in HMHD, theirstability under such conditions remains to be studied. The aim of this paper is to analyze the stability of an Alfvén wing,in the presence of an incompressible perturbation that has the same symmetry than the structure and polarization, inHMHD. Palumbo has developed an analytical method for the study of the stability of static structures with a symmetryin magnetized plasmas, in the presence of incompressible perturbations with the same symmetry than the structure.Since Alfvén wings are stationary structures, Sallago and Platzeck have shown the stability of such Alfvén wings in MHD conditions by extending Palumbo’s method. In the present paper this method is extended for Alfvén wings in HMHD conditions, and one concludes that in the presence of this kind of perturbations they are stable.

CYCLE STRATEGY OF LOCKDOWN AND ECONOMIC ACTIVITY DURING THE PANDEMIC COVID-19

The investigation focuses on an on-off protocol for relieving the COVID-19 widespread. The protocol establishes a working period of 4 days for all the citizens, followed by 8 days of lock-down. We further propose splitting people into smaller groups that accomplish the on-off protocol, but shifted in time. This procedure is expected to regularize the overall economic activity. Our results show that either the protocol and the splitting procedure relieve the spreading. However, the latter seems to be better for economic reasons. Our simulations further show that the start-up time is a key issue for the success of the implementation.