Revista Visión Electrónica: algo más que un estado sólido

6-18

Authors: Juan Jairo Vaca González, Juan Felipe Escobar Huertas, Diego Alexander Garzón Alvarado

Electrical stimulation is a non-invasive therapy used to stimulate chondrocyte dynamics: proliferation, migration, morphology and molecular synthesis. Some studies have evidenced the role of frequency in the generation of electric fields; however, the electrical stimulation sensed by chondrocytes when the frequency varies is not well-documented. Accordingly, a computational model was implemented to assess the frequency dependence of electric fields that stimulate chondrocytes. Cells were modelled in three different scenarios: monolayer cultures, cartilage explants and scaffolds. Chondrocytes were stimulated with 100 Vp-p at frequencies of 0.001, 1, 10, 50, 100 and 1000 kHz. Results showed that frequency is a relevant factor when considering the stimulation of biological samples, since electric fields increased as frequencies were higher. Moreover, chondrocytes experienced different electric fields in both cytoplasm and extracellular environment. This model provides relevant information about the electrical parameters to stimulate cells; in fact, it could enhance experimental procedures, predicting the stimulation that improves chondrocyte dynamics. Electric fields are a promising tool to maintain either well-structured chondrocytes or biomimetic materials used in regenerative therapies such as autologous implantation to treat hyaline cartilage injuries.

26-34

Authors: Ernesto Cadena-Muñoz, Luis Fernando Pedraza-Martínez, Enrique Rodríguez-Colina

This paper presents the results of the characterization of the attack known as the "primary user emulation" in mobile cognitive radio networks performing the implementation and testing. The tools and their configuration to carry out the attack are presented and their effects on the network are analyzed. The results show how to generate the attack with a software-defined radio equipment (SDR) using GNU-Radio and OpenBTS. The effects of the possible configurations of the attack on the network are shown, the malicious type generates constant interference on the primary or cognitive network, the selfish type allows to imitate a licensed or primary user generating interference to the primary network and inability to access the Cognitive Network while active. If the emulator's power level is fixed, the services it provides are stable. If the power is variable the services suffer intermittency. Primary user emulation is the attack that most affects the cognitive radio network so its effects are analyzed in order to propose ways of detecting or applying countermeasures.