The Indoor Radon Concentration within the Tunnels of the Cholula Pyramid Through a Nuclear Tracks Methodology

Global organizations, including the World Health Organization (WHO), the Environmental Protection Agency of the United States (US-EPA) and the European Atomic Energy Community (EURATOM) recognize that radon gas as one of the main contributors to environmental radiation exposure for humans. Accordingly, a study and analysis of the indoors radon concentrate in the Cholula Pyramid contributes to understand the Radon dynamic inside of the Pyramid tunnels and to evaluate the radiological health risk to visitors, archaeologists, anthropologists and persons who spend extended periods inside the Pyramid. In this paper, the radon measurements along the Pyramid tunnels are presented. The Nuclear Track Methodology (NTM) was chosen for the measurements, using a close end-cup device developed at the Dosimetry Application Project (DAP) of the Physics Institute UNAM, following very well established protocols for the chemical etching and reading with the Counting Analysis Digital Imaging System (CADIS). The Cholula Pyramid consists of eight stages of constructions, each built in different periods of time. Cholula Pyramid is recognized as the pyramid with the largest base in the World, with 400 meters per side and 65 meters high. The tunnels of the pyramid were built in 1931 by architect Ignacio Marquina, with the aim of exploring and studying the structure. The results show an important indoor radon concentration in the measured tunnels, several times higher than levels recommended by United States Environmental Protection Agency (US-EPA). The recommendation will be to mitigate the radon concentration levels, in order to avoid unnecessary exposition to the people

Study of secondary muons detected within the tunnels of the Cholula pyramid

The pyramid of Cholula was built at the beginning of 100 B.C. and during of period of 500 years it was finished, had several new constructions, based on the previous constructions. The primarily material of construction is the adobe. Early in 1931 archaeological excavations began with the intention of exploring the interior of the pyramid, excavations were stopped in 1971, and to date no further excavations have been carried out. This work shows the first measurements of muons, particles that are very penetrating, these are generated by primary cosmic rays that was incoming in the atmosphere and these generates a rain of secondary particles, among them the muons. To measure this kind of particles was implemented a detector system, it is formed by a scintillator plastic coupled to a tube photomultiplier; the signals were acquired by mean of an oscilloscope. The detector was collocated near of the center of the pyramid; the location belongs to the maxima concentration in mass over the detector. Graphs of the charge distribution, maximum amplitude and characteristic rise times of the generated pulses in a plastic scintillator are shown, this is scintillator was synthesized in the materials laboratory of the FCFM-BUAP. In addition the optical characterization of the same was realized

The dynamic architecture of the metabolic switch in Streptomyces coelicolor

Background: During the lifetime of a fermenter culture, the soil bacterium S. coelicolor undergoes a major metabolic switch from exponential growth to antibiotic production. We have studied gene expression patterns during this switch, using a specifically designed Affymetrix genechip and a high-resolution time-series of fermenter-grown samples. Results: Surprisingly, we find that the metabolic switch actually consists of multiple finely orchestrated switching events. Strongly coherent clusters of genes show drastic changes in gene expression already many hours before the classically defined transition phase where the switch from primary to secondary metabolism was expected. The main switch in gene expression takes only 2 hours, and changes in antibiotic biosynthesis genes are delayed relative to the metabolic rearrangements. Furthermore, global variation in morphogenesis genes indicates an involvement of cell differentiation pathways in the decision phase leading up to the commitment to antibiotic biosynthesis. Conclusions: Our study provides the first detailed insights into the complex sequence of early regulatory events during and preceding the major metabolic switch in S. coelicolor, which will form the starting point for future attempts at engineering antibiotic production in a biotechnological setting