Papers by Author: Alexander S. Balankin

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: 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: In this work, the mechanical properties of randomly folded thin sheets in the hydrostatic and non-hydrostatic stress states were studied. It is pointed out that under the hydrostatic compression the sheet, rigidity is governed by the volume dependence of its enthalpy, whereas in a non-hydrostatic stress state, the rigidity of folded sheets is controlled by the shape dependence of the Edwards entropy of the network of crumpling creases. Furthermore, the stress relaxation in folded sheets after uni-axial compression was studied. It was found that stress relaxation in folded elasto-plastic sheets differs from this in the folded predominantly plastic sheets and obeys an unusual relaxation law with the universal characteristic exponent.

Abstract: The fracture toughness of the Fe2B phase was evaluated in this study. Formation of the Fe2B boride is carried out though paste boriding process applied on AISI 1045 steel surface. The treatment was carried out at temperatures of 1193, 1223 and 1273 K for 6 h using a 5 mm thick boron paste. A Vickers microhardness tester was used to generate microcracks at a load of 200g. The indentations were made across the thickness of the iron boride layer at four different distances from the substrate. The experimental results show that the critical stress intensity factor KIC for the Fe2B phase shows a potential law dependence on crack length; this contradicts the concepts of Linear Elastic Fracture Mechanics, which establish that the fracture toughness value is a constant of the material.

Abstract: In this study, the evaluation of interfaces on iron boride Fe2B growth obtained by paste boriding process was carried out. Fractal geometry is used like a powerful tool for the roughness analysis present during iron boride growth. Experiments were performed in AISI 1045 steel at temperatures of 1193K for exposure times of 2, 4 and 6 h, and 1223K for treatment times of 2, 4, 5 and 6 h, varying the boron paste thicknesses in the range of 1 – 5 mm for each temperature and time. The fronts of the interfaces in iron boride coatings were characterized and digitized with mean of an optic microscope and Scion Image software. Self-affine methods were applied to the interface growths for validate the fractality of the system. It was established that the interface width, ω , scales to ω (L) ∼ L H , where H represents the roughness exponent of the boride layers.