University of Santiago de Cali
Cali, Colombia
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Quintero N.,University of Santiago de Cali | Quintero N.,CINVESTAV
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

In this work we study the short-range contributions that induce effective lepton number violating (LNV) interactions. We obtain a full set of constraints on the effective short-range couplings from a large variety of low-energy |ΔL|=2 processes of pseudoscalar mesons K,D,Ds,B, and τ-lepton. These constraints provide complementary and additional information to the one obtained from the neutrinoless double-β (0νββ) decay. As expected, the bounds on electron–electron short-range couplings are the only ones that are strongly constrained by the 0νββ decay. Although weaker, LNV effective couplings with different flavors are not accessible to 0νββ decay and these can be probe by the |ΔL|=2 processes in consideration. © 2016 The Author

Gomez H.,University of Santiago de Cali
Physical Review D | Year: 2017

Recently, the Cachazo-He-Yuan (CHY) approach has been extended to the loop level, but the resulting loop integrand has propagators that are linear in the loop momentum unlike Feynman's. In this paper, we present a new technique that directly produces quadratic propagators identical to Feynman's from the CHY approach. This paper focuses on the Φ3 theory, but extensions to other theories are briefly discussed. In addition, our proposal has an interesting geometric meaning; we can interpret this new formula as a unitary cut on a higher genus Riemann surface. © 2017 American Physical Society.

Cardona C.,National Tsing Hua University | Feng B.,Zhejiang University | Gomez H.,University of Sao Paulo | Gomez H.,University of Santiago de Cali | Huang R.,Zhejiang University
Journal of High Energy Physics | Year: 2016

The evaluation of generic Cachazo-He-Yuan(CHY)-integrands is a big challenge and efficient computational methods are in demand for practical evaluation. In this paper, we propose a systematic decomposition algorithm by using cross-ratio identities, which provides an analytic and easy to implement method for the evaluation of any CHY-integrand. This algorithm aims to decompose a given CHY-integrand containing higher-order poles as a linear combination of CHY-integrands with only simple poles in a finite number of steps, which ultimately can be trivially evaluated by integration rules of simple poles. To make the method even more efficient for CHY-integrands with large number of particles and complicated higher-order pole structures, we combine the Λ-algorithm and the cross-ratio identities, and as a by-product it provides us a way to deal with CHY-integrands where the Λ-algorithm was not applicable in its original formulation. © 2016, The Author(s).

Bueno Sanchez J.C.,University of Santiago de Cali | Bueno Sanchez J.C.,Antonio Nariño University | Bueno Sanchez J.C.,Industrial University of Santander | Bueno Sanchez J.C.,Complutense University of Madrid
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Single-field inflation, arguably the simplest and most compelling paradigm for the origin of our Universe, is strongly supported by the recent results of the Planck satellite and the BICEP2 experiment. The results from Planck, however, also confirm the presence of a number of anomalies in the Cosmic Microwave Background (CMB), whose origin becomes problematic in single-field inflation. Among the most prominent and well-tested of these anomalies is the Cold Spot, which constitutes the only significant deviation from Gaussianity in the CMB. Planck's non-detection of primordial non-Gaussianity on smaller scales thus suggests the existence of a physical mechanism whereby significant non-Gaussianity is generated on large angular scales only. In this Letter, we address this question by developing a localized version of the inhomogeneous reheating scenario, which postulates the existence of a scalar field able to modify the decay of the inflaton on localized spatial regions only. We demonstrate that if the Cold Spot is due to an overdensity in the last scattering surface, the localization mechanism offers a feasible explanation for it, thus providing a physical mechanism for the generation of localized non-Gaussianity in the CMB. If, on the contrary, the Cold Spot is caused by a newly discovered supervoid (as recently claimed), we argue that the localization mechanism, while managing to enhance underdensities, may well shed light on the rarity of the discovered supervoid. © 2014 The Author.

Chaur M.N.,University of Santiago de Cali
Acta Crystallographica Section E: Structure Reports Online | Year: 2013

In the mononuclear title complex, [ZnCl2(C15H16N4O)], the ZnII cation is five-coordinated in a strongly distorted square-pyramidal environment by two Cl- anions and a neutral tridentate Schiff base ligand. The ZnII cation is chelated by the carbonyl O atom, the imine N atom and the pyridine N atom, which causes a slight loss of planarity for the ligand; the dihedral angle between the aromatic rings is 4.61 (8)°.

Bravo J.J.,University of Santiago de Cali | Vidal C.J.,University of Santiago de Cali
Expert Systems with Applications | Year: 2013

Supply chain mathematical programming models mainly used for computer-aided decision-making processes, have been widely used to date as an advanced support to the experts' opinions. Transportation operations are often a central aspect of such models. We developed a detailed review of the freight transportation function included in supply chain models, and some transportation aspects were identified and analyzed in recent articles (2009-2013). We identified one paradigm, two trends and an anomaly regarding transportation modeling. The main anomaly-related observation refers to the absence of correspondence between the modeling of transportation operations and the transportation cost function considered in the models. This gap has not been so far considered in the literature and we propose a framework to guide, in a more systemic way, the transportation considerations into optimization models. In addition, some concerns regarding trade-off analysis, private/outsourced fleet considerations, the role of time and distance in transportation cost analysis, among others, were also included. These issues are expected to be significant for supply chain analysts whose decisions emerge from modeling and computer-aided tools. © 2013 Elsevier Ltd. All rights reserved.

Pachon L.A.,University of Antioquia | Rueda J.A.,University of Rome La Sapienza | Valenzuela-Toledo C.A.,University of Santiago de Cali
Astrophysical Journal | Year: 2012

Whether or not analytic exact vacuum (electrovacuum) solutions of the Einstein (Einstein-Maxwell) field equations can accurately describe the exterior space-time of compact stars still remains an interesting open question in relativistic astrophysics. As an attempt to establish their level of accuracy, the radii of the innermost stable circular orbits (ISCOs) of test particles given by analytic exterior space-time geometries have been compared with those given by numerical solutions for neutron stars (NSs) obeying a realistic equation of state (EOS). It has been so shown that the six-parametric solution of Pachón et al. (PRS) more accurately describes the NS ISCO radii than other analytic models do. We propose here an additional test of accuracy for analytic exterior geometries based on the comparison of orbital frequencies of neutral test particles. We compute the Keplerian, frame-dragging, and precession and oscillation frequencies of the radial and vertical motions of neutral test particles for the Kerr and PRS geometries and then compare them with the numerical values obtained by Morsink & Stella for realistic NSs. We identify the role of high-order multipole moments such as the mass quadrupole and current octupole in the determination of the orbital frequencies, especially in the rapid rotation regime. The results of this work are relevant to cast a separatrix between black hole and NS signatures and to probe the nuclear-matter EOS and NS parameters from the quasi-periodic oscillations observed in low-mass X-ray binaries. © 2012. The American Astronomical Society. All rights reserved.

Alvarez Valencia J.A.,University of Santiago de Cali
Computer Assisted Language Learning | Year: 2015

Social networking has compelled the area of computer-assisted language learning (CALL) to expand its research palette and account for new virtual ecologies that afford language learning and socialization. This study focuses on Busuu, a social networking site for language learning (SNSLL), and analyzes the views of language that are enacted through the semiotic design of this participatory online environment. The study draws on methodological principles of multimodality to examine the website and data collected through auto-ethnographic accounts of the researcher, who participated as a member of the Busuu community for 10 weeks. Results indicate that Busuu is an ecological system composed of nested sub-systems that reflect structural, interactional, and ecological views of language that interweave in conflicting and complementary ways. Suggestions to improve SNSLLs concern the need to reach alignment in terms of the theoretical and pedagogical tenets that underscore the design of instructional materials. Implications pinpoint the potential of intersecting multimodality and CALL in the study of participatory online environments. © 2015 Taylor & Francis

Crespo-Ortiz M.P.,University of Santiago de Cali | Wei M.Q.,Griffith University
Journal of Biomedicine and Biotechnology | Year: 2012

Improvement of quality of life and survival of cancer patients will be greatly enhanced by the development of highly effective drugs to selectively kill malignant cells. Artemisinin and its analogs are naturally occurring antimalarials which have shown potent anticancer activity. In primary cancer cultures and cell lines, their antitumor actions were by inhibiting cancer proliferation, metastasis, and angiogenesis. In xenograft models, exposure to artemisinins substantially reduces tumor volume and progression. However, the rationale for the use of artemisinins in anticancer therapy must be addressed by a greater understanding of the underlying mechanisms involved in their cytotoxic effects. The primary targets for artemisinin and the chemical base for its preferential effects on heterologous tumor cells need yet to be elucidated. The aim of this paper is to provide an overview of the recent advances and new development of this class of drugs as potential anticancer agents. © 2012 Maria P. Crespo-Ortiz and Ming Q. Wei.

Andrade-Bejarano M.,University of Santiago de Cali
Weather and Forecasting | Year: 2013

Data for this research come from time series of monthly average temperatures from 28 sites over the Valle del Cauca of Colombia in South America, collected over the period 1971-2002. Because of thegeographical location of the study area, monthly average temperature is affected by altitude and El Niño-La Niña (El Niño-Southern Oscillation, or ENSO phenomenon). Time series for some of the sites show a tendency to increase. Also, because of the two dry and wet periods in the studyarea, a seasonal pattern of behavior in monthly average temperature is seen. Linear mixed models are formulated andfitted to account for withinand between-site variations. The ENSOphenomenon is modeled by the Southern Oscillation index (SOI) and dummy variables. Spatial and temporal covariance structures in the errors are modeled individually using isotropic variogram models. The fitted models demonstrate the influence of the ENSO phenomenon on monthly average temperatures; this is seen in the maps produced from the models for ENSO and normal conditions. These maps show the predicted spatial patterns for differences in temperature throughout the study area. © 2013 American Meteorological Society.

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