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Antofagasta, Chile

The presence of the arsenic oxidation, reduction, and extrusion genes arsC, arrA, aioA, and acr3 was explored in a range of natural environments in northern Chile, with arsenic concentrations spanning six orders of magnitude. A combination of primers from the literature and newly designed primers were used to explore the presence of the arsC gene, coding for the reduction of As (V) to As (III) in one of the most common detoxification mechanisms. Enterobacterial related arsC genes appeared only in the environments with the lowest As concentration, while Firmicutes-like genes were present throughout the range of As concentrations. The arrA gene, involved in anaerobic respiration using As (V) as electron acceptor, was found in all the systems studied. The As (III) oxidation gene aioA and the As (III) transport gene acr3 were tracked with two primer sets each and they were also found to be spread through the As concentration gradient. Sediment samples had a higher number of arsenic related genes than water samples. Considering the results of the bacterial community composition available for these samples, the higher microbial phylogenetic diversity of microbes inhabiting the sediments may explain the increased number of genetic resources found to cope with arsenic. Overall, the environmental distribution of arsenic related genes suggests that the occurrence of different ArsC families provides different degrees of protection against arsenic as previously described in laboratory strains, and that the glutaredoxin (Grx)-linked arsenate reductases related to Enterobacteria do not confer enough arsenic resistance to live above certain levels of As concentrations.

Bernal G.,Catolica del Norte University
International Journal of Biological Markers | Year: 2012

Colorectal cancer is one of the most common forms of cancer worldwide. Early detection would allow patients to be treated surgically and halt the progression of the disease; however, the current methods of early detection are invasive (colonoscopy and sigmoidoscopy) or have low sensitivity (fecal occult blood test). The altered expression of genes in stool samples of patients with colorectal cancer can be determined by RT-PCR. This is a noninvasive and highly sensitive technique for colorectal cancer screening. According to information gathered in this review and our own experience, the use of fecal RNA to determine early alterations in gene expression due to malignancy appears to be a promising alternative to the current detection methods and owing to its low cost could be implemented in public health services. © 2012 Wichtig Editore.

Velazquez Abad L.,Catolica del Norte University
Annals of Physics | Year: 2012

Quantum mechanics and classical statistical mechanics are two physical theories that share several analogies in their mathematical apparatus and physical foundations. In particular, classical statistical mechanics is hallmarked by the complementarity between two descriptions that are unified in thermodynamics: (i)the parametrization of the system macrostate in terms of mechanical macroscopic observables I={I i}, and (ii) the dynamical description that explains the evolution of a system towards the thermodynamic equilibrium. As expected, such a complementarity is related to the uncertainty relations of classical statistical mechanics δI iδη i≥k. Here, k is the Boltzmann constant, η i=∂S(I{pipe}θ)/∂I i are the restituting generalized forces derived from the entropy S(I{pipe}θ) of a closed system, which is found in an equilibrium situation driven by certain control parameters θ={θ α}. These arguments constitute the central ingredients of a reformulation of classical statistical mechanics from the notion of complementarity. In this new framework, Einstein postulate of classical fluctuation theory dp(I{pipe}θ)~exp[S(I{pipe}θ)/k]dI appears as the correspondence principle between classical statistical mechanics and thermodynamics in the limit k→0, while the existence of uncertainty relations can be associated with the non-commuting character of certain operators. © 2012 Elsevier Inc.

Bekios-Calfa J.,Catolica del Norte University | Buenaposada J.M.,Rey Juan Carlos University | Baumela L.,Technical University of Madrid
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

Emerging applications of computer vision and pattern recognition in mobile devices and networked computing require the development of resource-limited algorithms. Linear classification techniques have an important role to play in this context, given their simplicity and low computational requirements. The paper reviews the state-of-the-art in gender classification, giving special attention to linear techniques and their relations. It discusses why linear techniques are not achieving competitive results and shows how to obtain state-of-the-art performances. Our work confirms previous results reporting very close classification accuracies for Support Vector Machines (SVMs) and boosting algorithms on single-database experiments. We have proven that Linear Discriminant Analysis on a linearly selected set of features also achieves similar accuracies. We perform cross-database experiments and prove that single database experiments were optimistically biased. If enough training data and computational resources are available, SVM's gender classifiers are superior to the rest. When computational resources are scarce but there is enough data, boosting or linear approaches are adequate. Finally, if training data and computational resources are very scarce, then the linear approach is the best choice. © 2011 IEEE.

Prieto M.,Catolica del Norte University
Mountain Research and Development | Year: 2015

(Figure Presented) The Chilean water model has been described as a textbook example of a free-market water system. This article contributes to the critiques of this model by showing the effect of its implementation in the Atacameño community of Chiu-Chiu, located in the Atacama Desert in the south-central Andes. In this community, the privatization of water rights ignored local water management practices that had produced a high-altitude wetland (known as a vega). This led to the inhabitants' dispossession of crucial water rights and to wetland degradation. This process belies statements that the Chilean model relies on an unregulated market and instead highlights the state's role in marginalizing local irrigation practices by reducing the water consumption of the indigenous population while keeping the copper mining industry (the main source of Chilean income) and related growing urban populations supplied with water. © 2015 by the authors.

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