Thirty crude extracts of eight plants belonging to Asteraceae and two to Rubiaceae families collected at different places from the Regional Natural Park Ucumarí (RNPU), Colombia, were tested for their antibacterial activity against two Gram-positive and two Gram-negative bacteria and three fungi. Both the antibacterial and the antimycotic activities were tested by the agar well diffusion method. The cytotoxic activity on the same plant extracts was determined through the brine shrimp lethality bioassay. The extracts from the Asteraceae family were more bioactive against Bacillus subtilis and Staphylococcus aureus. The extracts of both families studied were bioactive against the fungi Candida albicans and Fusarium solani. In addition, the extracts of Asteraceae species displayed the greatest cytotoxic activities. However, the most important specie in this research was Gonzalagunia rosea Standl (Rubiaceae) because of the strong and moderate activities of the methanol and dichloromethane extracts against C. albicans and F. solani, respectively; as well as the strong cytotoxic activity of the methanol extract. None of these ten plants has previously been reported for their biological activities.

Objective:The aim of this study was to determine ancestry informative markers, mitochondrial DNA haplogroups, and the association between HLA-DRB1 alleles and multiple sclerosis (MS) in a group of patients from Bogotá, Colombia.Methods:In this case-control study, genomic DNA was isolated and purified from blood samples. HLA-DRB1 allele genotyping was done using PCR. Mitochondrial hypervariable region 1 was amplified and haplogroups were determined using HaploGrep software. Genomic ancestry was estimated by genotyping a panel of ancestry informative markers. To test the association of HLA polymorphisms and MS, we ran separate multivariate logistic regression models. Bonferroni correction was used to account for multiple regression tests.Results:A total of 100 patients with MS (mean age 40.4 ± 12 years; 70% females) and 200 healthy controls (mean age 37.6 ± 11 years; 83.5% females) were included in the analysis. Ancestry proportions and haplogroup frequencies did not differ between patients and controls. HLA-DRB1*15 was present in 31% of cases and 13.5% of controls, whereas HLA-DRB1*14 was present in 5% of cases and 15.5% of controls. In the multivariate model, HLA-DRB1*15 was significantly associated with MS (odds ratio [OR] = 3.05, p < 0.001), whereas HLA-DRB1*14 was confirmed as a protective factor in our population (OR = 0.16, p = 0.001).Conclusions:This study provides evidence indicating that HLA-DRB1*15 allele confers susceptibility to MS and HLA-DRB1*14 allele exerts resistance to MS in a highly admixed population. This latter finding could partially explain the low prevalence of MS in Bogotá, Colombia.

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The chaos in a system is a very important element for a complete analysis in its dynamics. This is an indicator that allows to quantify this phenomenon which can be studied using the exponents of Lyapunov [1]. Here we present the methodology of determining them from the dynamics of the system (differential equations). When the dynamics of the system are known, it is necessary to reconstruct the phase space from the time series that are arranged.

The spatial distribution of an electrical potential in a cell membrane subjected to an electric field was numerically obtained using an equivalent electrical circuit where the spatial variables that depend on the geometry are combined and an electrical circuit that relates the dynamics in the time of said excitation in four branches that represent the middle. It was observed that the potential decreases linearly in the geometry of the membrane due to the characteristics of the medium (sodium, potassium). On the other hand, the finite element method was developed for a two-dimensional domain that represents the geometry of a membrane, in such a way that it is possible to qualitatively analyze the behavior of the potential at any point of the membrane for an electrical pulse (electrode).

This paper presents the mathematical analysis of the linear interpolation equations that form a basis around the finite element method for the formulation of a global function by parts that approximates the solution of a second order ordinary differential equation. The numerical solutions for the systematic calculation are compared with three elements and 26 elements supported on a computer with the exact solution that satisfies a second order ordinary differential equation [1]. It is also intended to take the reader with the demonstrations and obtain each of the equations described in this document in such a way that the results can be reproduced manually or with specialized software [5].

Ti x Al 1-x N coatings were grown using the triode magnetron sputtering technique with various bias voltages between -40 V and -150 V. As the bias voltage increased, an increase in the Al atomic percentage was observed, presenting a competition with Ti and producing structural changes. Moreover, the grain size and roughness were also strongly influenced by the bias voltage. It was observed that coatings with concentrations of approximately 25% Al and 75% Ti exhibited an optimum mixture of mechanical and tribological properties. The average coefficient of friction was low for the TiAlN coating that was grown at -40 V. Additionally, the critical load was obtained by measuring the adhesion using the scratch test.

In the present paper a detailed analysis of the bifurcation of the Van der Pol oscillator is carried out, which starts by giving an account of the theory of chaos and dynamic systems, complements mentioning the main theoretical concepts of the dynamic systems and the different forms of analysis that exist, then continues to expose the discovery of the Van der Pol oscillator, to finally expose the results obtained from the bifurcation analysis of the oscillator.