Héctor Cadavid

Chemical and spectroscopic characterization of a vegetable oil used as dielectric coolant in distribution transformers

In this work, a complete UV-Vis, IR and (1H, 13C and DEPT) NMR spectroscopic analysis was performed for a FR3® vegetable oil sample used as dielectric coolant in an experimental distribution transformer. The same spectroscopic analysis was performed for three used FR3® oil samples (i.e., 4 months in use, 8 months in use and 7 years in use), removed from several operating distribution transformers. Comparison of the data indicated that no significant spectroscopic changes, and hence, no structural changes occurred to the oils by the use. Chemical transformations like catalytic hydrogenation (hardening) and hydrolysis were performed to the FR3® oil sample and the obtained products were analyzed by spectroscopic methods in order to collect further structural information about the FR3® oil. Accelerated aging tests in laboratory were also performed for three FR3® oil samples affording interesting information about the structure of the degradation products. These findings would be valuable to search for a spectroscopy-based technique for monitoring the life-time and performance of this insulating vegetable oil.

Design Study for a Cellular Culture Bioreactor Coupled with a Magnetic Stimulation System

This article presents a design study performed to integrate a cellular culture bioreactor along with an external magnetic stimulation system, aimed at creating ideal environmental conditions that allow for cellular culture and cellular tissue growth to take place in three dimensions, under a sterile environment favorable for the development of bioorganic grafts which have been exposed to controlled electromagnetic fields. The different systems that have been designed and constructed are described along with their particular characteristics and all general considerations that were taken into account during the design process are presented, as well as the main variables that must be considered during implementation in order to guarantee constant and adequate function of the integrated systems, as well as reproducible results.

A new ray-tracing acceleration technique for radio propagation

Since site measurements are costly, propagation models have been developed as a convenient, adequate, and low-cost alternative to design personal communication systems, such as mobile phone. With the rapid advance in computing, ray-tracing techniques have become one of the most popular methods for characterizing the radio propagation in different environments. These techniques are attractive due to its high accuracy in dense urban areas [1]-[3] and indoor environments [4]. The disadvantage of ray-tracing method is the large computational cost that may be inappropriate in complex environments. For this reason, it is necessary to use efficient propagation models and ray-tracing acceleration techniques [5].

Resultados preliminares del crecimiento de tejido celular usando un bioreactor con sistema de estimulación magnética

This article presents the preliminary results obtained from an earlier publication of a design study performed to integrate a cellular culture bioreactor along with an external magnetic stimulation system, which was aimed at creating ideal environmental conditions that allowed for cellular culture and cellular tissue growth to take place in three dimensions, under a sterile environment favorable for the development of bioorganic grafts which were exposed to controlled electromagnetic fields. Cellular tissue was used from cellular lines of Normal Human Skin Fibroblast (NHSF) and was seeded on bio-synthetic scaffolds synthesized from polylactic acid (PLA) and Chitosan mixtures. The cellular tissue covered scaffold was then introduced into the cellular culture bioreactor, subsequently it was filled with cellular culture medium and put under dynamic flow conditions in while at the same time using the external magnetic stimulation system to irradiate the cellular tissue with controlled magnetic fields. The results present static tests of cell growth where the maximum change in growth was after 48 hours when the cells were exposed to a 1 mT, 60 Hz magnetic field; they proliferated at a rate of 52% without Chitosan, 75% with Chitosan and 53% under dynamic flow versus the non-exposed cellular tissue. These results have allowed us to continue our experimentation techniques to evaluate changes in 3-dimensional growth of magnetically stimulated tissues under dynamic flow.

Growth rates of dynamic dermal model exposed to laminar flow and magnetic fields

Introduction Ongoing research in the use of electromagnetic stimulation as coadjuvant in fracture healing has led the authors to begin generating computer models in order to predict cellular growth changes when cells are electromagnetically stimulated. By generating these models, scientists will be able to better understand how electromagnetic fields affect cellular development. The experimental design integrated a cellular culture bioreactor along with an external magnetic stimulation system, which allowed for dermal models to be exposed to controlled magnetic fields. Methods Initially, it was necessary to analyze the static growth of Normal Human Skin Fibroblast (NHSF) cells when they were exposed to Extremely Low Frequency – Electromagnetic Fields (ELF-EMFs). Using optimal conditions for the NHSF culture, from stimulation signal to scaffolding material, we were able to perform the dynamic flow stimulation experiments. Results The following systems were developed: (1) a bioreactor aimed at cellular tissue culture, and (2) Helmholtz coils capable of generating stimulation signals for the cultured tissue. The authors were able to appreciate the quantified values of cellular density diluted in all the experiment samples that were taken and overall, the irradiated samples displayed an average increase of 53% higher cellular density for the same amount of initial cellular seeding when the cells were exposed to a 1 mT, 60 Hz magnetic field signal. Conclusion ELF-EMF’s indeed alter NHSF cell growth rates and it is the challenge of the authors to continue investigating what cellular mechanisms are altered when cells are exposed to ELF-EMF’s.

Mapeo del Campo Magnético de Frecuencia Industrial en un Ambiente Hospitalario

The hospital environment is rich both in number and diversity of electronic equipment, which is susceptible of receiving signals that may produce functional disturbances in these devices. The increase of electromagnetic fields sources in these environments, has led to researchers around the world to quantify the potential risk of electromagnetic interference on medical equipment. To reduce risks in these equipments, it is important to know the electromagnetic field environment that can be found in the hospitals and clinics. In this paper, the results of power frequency magnetic field measurements carried out in different services of a large hospital are presented. The results show that magnetic field in some rooms was higher than immunity test levels established by international standard for medical devices.

Medición del Campo Eléctrico Ambiente de Alta Frecuencia en un Hospital

Each hospital has a unique electromagnetic environment. This can be extremely variable, particularly as a result of the great growth of wireless communications. This complex system is marked by numerous sources of electromagnetic energy both inside and outside hospitals and clinics. In this paper, the results of high frequency electric field measurements carried out in different departments of a large hospital are presented. The results show that electric field environment in all rooms measured was lower than radiated immunity test levels for medical devices established by international standard.