National Pedagogic University (Colombia)

About: National Pedagogic University (Colombia) is a education organization based out in Bogotá, Colombia. It is known for research contribution in the topics: Anharmonicity & Differential equation. The organization has 230 authors who have published 226 publications receiving 1229 citations.

Occurrence of Antibiotic Resistance Genes and Bacterial Markers in a Tropical River Receiving Hospital and Urban Wastewaters

Abstract: The occurrence of emerging biological contaminants including antibiotic resistance genes (ARGs) and Faecal Indicator Bacteria (FIB) is still little investigated in developing countries under tropical conditions. In this study, the total bacterial load, the abundance of FIB (E. coli and Enterococcus spp. (ENT)), Pseudomonas spp. and ARGs (blaTEM, blaCTX-M, blaSHV, blaNDM and aadA) were quantified using quantitative PCR in the total DNA extracted from the sediments recovered from hospital outlet pipes (HOP) and the Cauvery River Basin (CRB), Tiruchirappalli, Tamil Nadu, India. The abundance of bacterial marker genes were 120, 104 and 89 fold higher for the E. coli, Enterococcus spp. and Pseudomonas spp., respectively at HOP when compared with CRB. The ARGs aadA and blaTEM were most frequently detected in higher concentration than other ARGs at all the sampling sites. The ARGs blaSHV and blaNDM were identified in CRB sediments contaminated by hospital and urban wastewaters. The ARGs abundance strongly correlated (r ≥ 0.36, p < 0.05, n = 45) with total bacterial load and E. coli in the sediments, indicating a common origin and extant source of contamination. Tropical aquatic ecosystems receiving wastewaters can act as reservoir of ARGs, which could potentially be transferred to susceptible bacterial pathogens at these sites.

Thermodynamic quantities of metals investigated by an analytic statistical moment method

Abstract: The thermodynamic properties of metals are studied by including explicitly the anharmonic effects of the lattice vibrations going beyond the quasiharmonic approximations. The free energy, thermal lattice expansion coefficients, mean-square atomic displacements, and specific heats at the constant volume and those at the constant pressure, ${C}_{v}$ and ${C}_{p},$ are derived in closed analytic forms in terms of the power moments of the atomic displacements. The analytical formulas give highly accurate values of the thermodynamic quantities, which are comparable to those of the molecular dynamics or Monte Carlo simulations for a wide temperature range. The present formalism is well suited to calculate the thermodynamic quantities of metals and alloys by including the many body electronic effects and by combining it with the first-principles approaches.

hcp-bcc structural phase transformation of titanium: Analytic model calculations

Abstract: We show that the hcp $(\ensuremath{\alpha})\ensuremath{\rightarrow}\mathrm{bcc}\phantom{\rule{0.3em}{0ex}}(\ensuremath{\beta})$ structural phase transformation of titanium occurs via anharmonicity effect of thermal lattice vibrations. The full-potential linear muffin-tin orbital method in the local density approximation with the generalized gradient correction is used to derive the embedded atom potential for Ti, which allows us the analytic and realistic calculations of the thermodynamic quantities. We also discuss the similar phase transformation but slightly different mechanism occurring in zirconium in terms of the anharmonicity of thermal lattice vibrations.