Barranquilla, Colombia
Barranquilla, Colombia

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Vicencio R.A.,University of Chile | Cantillano C.,University of Chile | Morales-Inostroza L.,University of Chile | Real B.,University of Chile | And 5 more authors.
Physical Review Letters | Year: 2015

We present the first experimental demonstration of a new type of localized state in the continuum, namely, compacton-like linear states in flat-band lattices. To this end, we employ photonic Lieb lattices, which exhibit three tight-binding bands, with one being perfectly flat. Discrete predictions are confirmed by realistic continuous numerical simulations as well as by direct experiments. Our results could be of great importance for fundamental physics as well as for various applications where light needs to be conducted in a diffractionless and localized manner over long distances. © 2015 American Physical Society.

Vega Monroy R.,University of the Atlantic
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

In this paper we point out the possible observation of the Bose-Einstein condensation for a gas of paired photon-dressed electrons in a graphene monolayer. At T=0 the condensation presents a strong crossover from the BCS state to the Bose-Einstein condensate. In an explicit way we calculated the fraction of condensed photon-dressed electron pairs as a function of the photon-electron bound energy and the temperature. The range of coherence of condensed quasiparticles is circumscribed to local bound states, where the Off-diagonal long-range order is guaranteed via the BCS state. © 2014 Elsevier B.V.

In conflicts between primate groups, the resource-holding potential (RHP) of competitors is frequently related to group size or male group size, which can remain relatively constant for long periods of time, promoting stable intergroup dominance relationships. Demographic changes in neighboring groups, however, could introduce uncertainty into existing relationships. Among tufted capuchin monkeys (Cebus apella nigritus), dominant male replacement is a relatively infrequent demographic event that can have a profound effect on both the composition and size of the social group. Here, we report such a case and the consequences for home range use and intergroup aggression. Between June 2008 and August 2010, we periodically followed two neighboring groups (Macuco and Rita) in Iguazú National Park, recording daily paths (N = 143) and encounters between the groups (N = 28). We describe the events leading to a change in the male dominance hierarchy in the larger group (Macuco), which resulted in the death or dispersal of all adult males, followed by the succession of a young adult male to the dominant position. This takeover event reduced the numerical advantage in number of males between the two groups, although the ratio of total group sizes remained nearly constant. Following this shift in numerical asymmetry, the degree of escalation of intergroup aggression increased, and we observed reversals in the former intergroup dominance relationship. These changes in behavior during intergroup encounters were associated with changes in the use of overlapping areas. In the 6 months following the takeover, the area of home range overlap doubled, and the formerly dominant group's area of exclusive access was reduced by half. These results suggest that RHPin tufted capuchin monkeys is related to male group size. Furthermore, they highlight the importance of considering rare demographic events in attempts to understand the dynamics of aggression between primate groups. © 2012 Wiley Periodicals, Inc.

Reslen J.,University of the Atlantic
Revista Mexicana de Fisica | Year: 2013

A protocol to obtain the matrix product state representation of a class of boson states is introduced. The proposal is presented in the context of linear systems and is tested by performing simulations of a reference model. The method can be applied regardless of the details of the coupling among modes and can be used to extract the most significant contribution of the tensorial representation. Characteristic issues as well as potential variants of the proposed protocol are discussed.

Pistollato F.,Marche Polytechnic University | Battino M.,Marche Polytechnic University | Battino M.,University of the Atlantic
Trends in Food Science and Technology | Year: 2014

Plant-based diets are known to preserve body tissues from oxidative stress and inflammation, both hallmarks of chronic-degenerative diseases. In particular, plant-derived foods, such as legumes, represent a natural source of bioactive nutrients known to contribute to the prevention and amelioration of insulin resistance, dyslipidemia, hypertension and impaired glucose metabolism, all factors implicated in metabolic syndrome (MetS), but also osteoporosis, neurodegeneration and some types of cancers. Here we revise recent literature on the role of plant-based diets, plant-foods and specific plant-nutrients in the prevention and regression of MetS and neurodegenerative diseases. We describe some of the molecular mechanisms underlying these protective effects, highlighting the role of diet in the control of hyper-homocysteinemia and insulin resistance, often implicated in the etiology of both metabolic and neurodegenerative syndromes. © 2014 Elsevier Ltd. All rights reserved.

Ordonez-Lasso A.F.,University of Antioquia | Cardona J.C.,University of the Atlantic | Sanz-Vicario J.L.,University of Antioquia
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We have implemented a method based on the Feshbach formalism along with an explicitly correlated configuration interaction method to perform a systematic study on the behavior of resonance parameters (energies and lifetimes) of the autoionizing states of plasma-embedded He 1,3Se, 1,3Po, and 1,3De, as a function of the screening strength. In particular, we study the evolution of the lowest states in the series located below the He+(N=2) ionization threshold in the unscreened case. At variance with one-electron atoms (where shape resonance widths vary monotonically with the screening strength) the evolution of the Auger width with respect to screening is found to be different for each series represented by (K,T)A pseudoquantum numbers until resonances merge into the upper electronic continuum, when crossing the He+(2s) threshold. We conclude from our ab initio calculations that, although resonances pertaining to the same (K,T)A series share a similar tendency in their widths against the screening strength, general propensity rules for the robustness of lifetimes, based on the isomorphic series in the (K,T)A classification, cannot be established in plasma-embedded helium. © 2013 American Physical Society.

Reslen J.,University of the Atlantic
Journal of Physics A: Mathematical and Theoretical | Year: 2015

An approach to the simulation of locally interacting systems is demonstrated and assayed. The proposal is built upon the concept of folding of bosonic modes previously introduced in the context of linear dynamics and can be seen as an alternative to Trotter-Susuki expansion in studies of quantum propagation based on tensor states. It is shown that evolution as well as ground state computations can be implemented and that test simulations deliver comparatively accurate results. The whole analysis provides insight into the way well-known quantum structures affect mean values and fluctuations in realistic setups. The proposed method can be used to study a variety of systems and phenomena arising in optical lattice experiments such as superfluid or Mott insulator regimes, quantum phase transitions, soliton propagation in Bose-Einstein condensates or Bose mixtures and elementary vortex excitations. © 2015 IOP Publishing Ltd.

Trujillo J.C.,University of the Atlantic | Carrillo B.,University of the Atlantic | Iglesias W.J.,University of the Atlantic
Health Policy and Planning | Year: 2014

The determinants of maternal and child health have been the recurrent topics of study in developing countries. Using the Demographic and Health Survey (2010) of Colombia, this study aimed to identify the determinants for professional antenatal care and institutional delivery, taking into account the interdependence of these two decisions, which we consider using a bivariate probit model. This study found that when certain factors affecting both the decision to seek prenatal care and giving birth in a hospital are neglected, the results of the estimates are inefficient. Estimates show that the effects of education, parity, regional location and economic status on institutional delivery tend to be underestimated in a univariate probit model. The results indicate that economic status, level of education, parity and medical-insurance affiliation influenced the joint likelihood of accessing professional antenatal care and delivering in a health facility. An important finding is that mothers with a higher level of education are 9 percentage points more likely to access these two health services compared with mothers who are illiterate. Another observed finding is the regional disparities. The evidence indicates that mothers in the Pacific Region, the poorest region of Colombia, are 6 percentage points less likely to access such services. Thus, the results indicate that the Colombian health policy should emphasize increasing the level of schooling of mothers and establish health facilities in the poorest regions of the country to ensure that women in need are provided with social health insurance. © The Author 2013; all rights reserved.

Hernandez J.,University of Caldas | Hernandez J.,National University of Colombia | Gordillo G.,National University of Colombia | Vallejo W.,University of the Atlantic
Applied Energy | Year: 2013

This paper presents a methodology to predict in a statistically reliable way the behavior of a grid-connected photovoltaic system. The methodology developed can be implemented either in common programming software or through an off-the-shelf simulation of electrical systems. Initially, the atmospheric parameters that influence the behavior of PV generators (radiation and temperature) are characterized in a probabilistic manner. In parallel, a model compound by various PV generator components is defined: the modules (and their electrical and physical characteristics), their connection to form the generator, and the inverter type. This model was verified for comparing their behavior with output measured on a real installed system of 3.6. kWp. The solar resource characterized and the photovoltaic system model are integrated in a non-deterministic approach using the stochastic Monte Carlo method, developed in the programming language DPL of the electrical-systems simulation software DIGSILENT®. It is done to estimate the steady-state electrical parameters describing the influence of the grid-connected photovoltaic system. Specifically, we estimated the nominal peak power of the PV generator to minimize network losses, subject to constraints on nodes voltages and conductor currents. © 2012 Elsevier Ltd.

Sandoval-Diaz L.-E.,University of the Atlantic | Martinez-Gil J.-M.,University of the Atlantic | Trujillo C.A.,National University of Colombia
Journal of Catalysis | Year: 2012

NaCl and [VO(C 5H 7O 2) 2] were impregnated on a commercial ultra-stabilized Y zeolite (USY). Samples were calcined in dry air at 700 °C and examined by X-ray diffraction (XRD), N 2 adsorption, isopropylamine decomposition and the n-butane cracking reaction. Sodium concentration was kept constant but in excess related to a variable vanadium concentration. Dry thermal treatment in the presence of metal contamination was found to induce framework destruction by sodium but not by vanadium. Vanadium was found to neutralize preferentially the Bronsted acid sites (BASs) responsible for alkane cracking. Selectivity to dehydrogenation increases with vanadium loading due to its intrinsic redox activity. No evidence of a vanadium-sodium compound was found; sodium reacts preferentially with the framework than with vanadium. Arrhenius plots rendered quite linear relations, and isokinetic behavior was established for cracking and dehydrogenation reactions. The findings clearly show that the slopes in Constable-Cremer plots are sensitive to the reaction mechanism. © 2012 Elsevier Inc. All rights reserved.

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