Applied Mechanics and Materials Vol. 15

Abstract: The behavior of solar radiation fluctuations in Mexico City is analyzed under a fractal framework. We find that solar radiation fluctuations display an antipersistent long horizon behavior. It means that is more probable to observe less solar radiation in the following day, if there is a rising trend in solar radiation intensity, and vice versa.

Abstract: Sol-gel nanostructured titania (TiO2) was functionalized in order to produce a nanomaterial biocompatible with brain tissue. Neuroreservoirs made from titania microtubes have been used to release sodium phenytoin and valproic acid. In vitro and in vivo probes were used to treat the epilepsy disease. Pore space topology and interactions between matrix and drug are the most important phenomena that affect the drug diffusion and liberation kinetics. Accordingly, fractal morphology of nanostructured titania as a function of pH and polarity of the drug added during the gelation reactions was studied. The transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), and N2 adsorption (BET) were employed to characterize the nanomaterials with maximum amount of air hollows occluded inside a drug. It was found that the clusters and pores in nanostructured titania are characterized by the universal fractal dimensions and . However, the characteristic sizes of particles and pores, the porosity, and the fractal dimension of pore surface ( ) are dependent on hydrolysis water concentration added during the gelation reaction. So, the matrix hydroxylation permits to control the drug liberation kinetics.

Abstract: Current epilepsy rates in Mexico are 4% (SERSAME-Health Ministry), of which 80% correspond to Temporal Lobe Epilepsy (TLE). Antiepileptic drug administration is systemic, meaning that 90% of the active agent is lost between administration and delivery to the epileptic focus in the brain. Severe toxic secondary effects may occur as a result. The present study is aimed at developing an alternative antiepileptic drug delivery system. In this study, a sol-gel nanostructured titania device, in which valproic acid (VPA) has been encapsulated. This is a nanoparticulate device, which is biocompatible with brain tissue. Stereotactic surgery was used to implant the reservoirs in the temporal lobe of Wistar rats, using chemical kindling, which was used to induce epilepsy. The reservoir was designed to release the drug at a constant rate over a period of at least one year. A functional study was performed on the efficiency of drug delivery in order to evaluate the effect on spontaneous and induced neuron electrical activity. A new discovery, which is presented here, shows that in the case of damaged brain tissue, as is the case in epilepsy, the accumulation of red globules, oxygen transportation results in the formation of calcium carbonate crystals which surround the epileptic focus. Because these crystals have a specific polarization, we propose to characterize their influence on the EEG using statistical methods. The electrical activity was measured by electroencephalography using 5 healthy rats without and 5 rats with an implanted VPA/device. Cerebral signals describe the complex behavior of the brain dynamics as a function of time. Fractal algorithms are sensitive to fluctuations and lead to the analysis and characterization of this kind of complex phenomena. A systematic study of these EEG’s was made in order to observe the variation of signals during seizures and on the controlled rate of release of VPA. We have estimated the Hurst exponent (H) to measure long range-dependence. Preliminary results show that for the control group, signal behavior is persistent (H>0.5), while for the epileptic group antipersistency was observed (H<0.5), with variations due seizure stages. During the protection period using VPA, preliminary results show that values tend to reach original behavior, as the crisis is stabilized.

Abstract: The parametric analysis of the electrical conductivity distribution for the Perfect Matched Layer (PML) method, is discussed in this communication. The Berenger’s PML defines a new computational space around the area of interest yielding to reduce any undesirable reflection that may perturb the main computational domain. The optimal parameters values for the conductivity distribution are obtained in order to provide lower levels of reflection, given raise to model infinite electromagnetic propagation spaces and as a consequence, to optimize the computing resources.