Los Andes University (Colombia)
Recent publications
A preliminary stability and dispersion study for wave propagation problems is developed for mimetic finite difference discretizations. The discretization framework corresponds to the fourth-order staggered-grid Castillo-Grone operators that offer a sextuple of free parameters. The parameter-dependent mimetic stencils allow problem discretization at domain boundaries and at the neighbor grid cells. For arbitrary parameter sets, these boundary and near-boundary mimetic stencils are lateral, and we here draw first steps on the parametric dependency of the stability and dispersion properties of such discretizations. As a reference, our analyses also present results based on Castillo-Grone parameters leading to mimetic operators of minimum bandwidth that have been previously applied in similar physical problems. The most interior parameter-dependent mimetic stencils exhibit a specific Toeplitz-like structure, which reduces to the standard central finite difference formula for staggered differentiation at grid interior. Thus, our results apply to the whole discretization grid. The study done for the 1-D problem could be applied to the discretization of a free surface boundary condition along an orthogonal gridline to this boundary.
Natural carotenoids are secondary metabolites that exhibit antioxidant, anti-inflammatory, and anti-cancer properties. These types of compounds are highly demanded by pharmaceutical, cosmetic, nutraceutical, and food industries, leading to the search for new natural sources of carotenoids. In recent years, the production of carotenoids from bacteria has become of great interest for industrial applications. In addition to carotenoids with C40-skeletons, some bacteria have the ability to synthesize characteristic carotenoids with C30-skeletons. In this regard, a great variety of methodologies for the extraction and identification of bacterial carotenoids has been reported and this is the first review that condenses most of this information. To understand the diversity of carotenoids from bacteria, we present their biosynthetic origin in order to focus on the methodologies employed in their extraction and characterization. Special emphasis has been made on high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the analysis and identification of bacterial carotenoids. We end up this review showing their potential commercial use. This review is proposed as a guide for the identification of these metabolites, which are frequently reported in new bacteria strains.
In this chapter, I will I try to demonstrate that reading Dōgen through the lens of contemporary logic can help dispel obscurities and solve interpretative dilemmas. I hope to argue in favor of this hermeneutic technique performatively by showing its advantages when faced with one of the most difficult sides of Dōgen’s writings, his ideas on time. In detail, I will argue that, instead of there being one paradox in Dōgen’s writings, there are two distinct paradoxical issues, the first concerning the ontological imbrication of distinct times, and the second, the fact that Dōgen at times seems to emphasize the ontological priority of temporal instants and, at other times, the ontological priority of time as a continuous flow. I then look back to Nāgārjuna to clarify the philosophical foundations of Dōgen’s ideas on time, specially concerning the nature of co-dependently arisen entities and their occupation of space, and use this to reformulate the paradoxes. Then, following recent works pertaining to the formal mereology of time and its occupiers, I makes use of the distinction between extensive and intensive occupation to solve these same paradoxes.
Brewer’s spent grain (BSG) is a biomass with a high lignocellulosic content that can be reused in thermal processes, however it has high moisture content, which avoids it from being used in these processes. Pretreatment by drying rotating equipment turns out to be a suitable alternative. This work studied the rotational drying of BSG analyzing the effects of adhesion of solids. To do this, a standard pan combined with an external blower was chosen as a rotary dryer due to the easy access to the bed and the inner surface of the dryer. In addition, this type of dryer made possible to determine the relationship between BSG moisture and adhesion force. Under the operating conditions of the experiments, the moisture content of BSG decreased from 80 to 8.6% (wb), making it possible for the biomass to be utilized in thermal processes. Moisture ratios higher than 0.6 led to greater adherence and consequent agglomeration of solids, reducing their mobility and heat transfer with the internal surface of the dryer. At the start of drying, the bed’s rotational speed rate of BSG was approximately 14 rpm, half of the maximum rate of 28 rpm, also the temperatures of the BSG and the inner wall of the tray were in equilibrium, showing that changes in biomass adhesion would take non-uniform drying. Graphical Abstract Novelty Statement. Understanding of the drying of spent grain with focus on adhesion and cohesion mechanisms allows adequate strategies to reduce negative effects of agglomeration, allowing the reuse of this biomass.
Inexpensive porous activated biocarbons were prepared from biomass and agriculture waste following the method of thermal and hydrothermal carbonization and activation with superheated water vapor. The activated biocarbons were characterized by nitrogen adsorption−desorption at 77 K, SEM, XRD, Raman spectrometry, FTIR spectroscopy, determination of particle size, and elemental composition by XRF. The specific surface area was in the range of 240−709 m 2 /g, and the total pore volume was from 0.12 to 0.43 cm 3 /g. The percentage of microporosity in activated biocarbons was 89−92%. These activated biocarbons have been used for CO 2 and heavy metal sorption. Activated biocarbons based on pine cones and birch prepared by thermal carbonization and activation with superheated water vapor had the highest ability to capture CO 2 and amounted to 6.43 and 6.00 mmol/g at 273 K, as well as 4.57 and 4.22 mmol/g at 298 K, respectively. The best activated biocarbon was characterized by unchanged stability after 30 adsorption and desorption cycles. It was proved that the adsorption of CO 2 depends on narrow micropores (<1 nm). Activated biocarbons have also been analyzed as effective adsorbents for removing Cu 2+ , Zn 2+ , Fe 2+ , Ni 2+ , Co 2+ , and Pb 2+ ions from aqueous solutions. Activated biocarbons are effective adsorbents for the removal of lead and zinc ions from aqueous solutions.
Colombia’s mental health services have a complex history shaped by 60 years of armed conflict, a predominantly clinical approach to mental health, and social factors such as inequities and stigma. The 1990 Caracas declaration proposed a shift towards decentralised community mental health services and interventions based on the recovery approach and emphasis on social determinants of mental health in the Americas. Colombia has adopted these approaches in its legal and practical framework in recent years, but implementation has been uneven. This systematic review aims to contribute to mental health services understanding in Colombia by examining the barriers and facilitators to the implementation of mental health services in Colombia. A search was conducted to explore available peer-reviewed studies on Colombian mental health services across five databases (Medline, PubMed, Scopus, Scielo and BVS) on quantitative and qualitative research papers published in the last ten years and without language restrictions. The Consolidated Framework for Implementation Research (CFIR) was used to structure the analysis and identify barriers and facilitators during the implementation of mental health services. We adapted the CFIR to attend to gender, race and age informed by the Socio-Political Economy of Global Mental Health framework, given the importance of these factors to the Colombian health landscape. Finally, narrative synthesis was used to summarise the data. 1 530 records were identified, and 12 articles met all inclusion criteria and were included in the analysis. 8 papers described substance use disorders services, 11 involved multidisciplinary healthcare professionals, and 7 were implemented at a local scale. The primary barriers to implementation were the lack of coordination, high workloads, and low funding. Facilitators included the use of protocols, and the involvement of communities, stakeholders, users, and external champions. Findings suggest the continued importance of community and recovery approaches and efforts to improve coordination between multi-sector actors involved in the mental health spaces (e.g., public, and private organisations, users and their families).
Scholarship in colonial and nineteenth-century Latin American studies often does not reach beyond specialized academic audiences. The majority of work continues to be largely traditional in nature, with monographs, journal articles, and book chapters remaining the most common types of publications.Only a small portion of that production is distributed in an open-access format online, and even when that is the case, such scholarly output is generally not conceived with broader publics in mind, and engagement with stakeholder communities seldom plays a role in its creation.Digital methodologies and tools present opportunities to explore new modes of scholarly production and publication in these fields. Researchers working in a digital realm are designing and carrying out projects that speak to contemporary communities and involve diverse constituencies in new ways. Without seeking to supplant the more conventional scholarship that grounds their fields, these scholars are asking questions about how we conduct academic work in the twenty-first century and how we can make the products of our work relevant to larger audiences.This article examines five digital projects through which scholars of colonial and nineteenth-century Latin America are conducting work that looks outward from the academy towards inclusive scholarship: Ticha, the Biblioteca Digital Soledad Acosta de Samper, the Mexico team of the multinational project Oceanic Exchanges, Rendering Revolution, and coloniaLab. Through a commitment to producing scholarship for, and in collaboration with, diverse communities,these projects suggest models for conducting the work of colonial and nineteenth-century Latin American studies in the public sphere.Les études sur l'Amérique latine coloniale et du XIXème siècle ne s'adressent souvent qu'à un public universitaire spécialisé. Seule une petite partie de cette production est distribuée en ligne dans un format à accès libre, et même lorsque c'est le cas, cette production scientifique n'est généralement pas conçue pour un public plus large, et l'engagement avec les communautés concernées joue rarement un rôle dans sa création.Les méthodologies et les outils numériques offrent la possibilité d'explorer de nouveaux modes de production et de publication scientifiques dans ces domaines. Sans chercher à supplanter la recherche plus conventionnelle qui fonde leurs domaines, ces chercheurs posent des questions sur la manière dont nous menons le travail universitaire au XXIe siècle et sur la manière dont nous pouvons rendre les produits de notre travail pertinents pour des publics plus larges. Cet article examine cinq projets numériques dans le cadre desquels des chercheurs de l'Amérique latine coloniale et du XIXème siècle mènent des travaux qui s'éloignent de l'académie pour s'ouvrir à un public plus large : Ticha, la Biblioteca Digital Soledad Acosta de Samper, l'équipe mexicaine du projet multinational Oceanic Exchanges, Rendering Revolution et coloniaLab. En s'engageant à produire des études pour diverses communautés et en collaboration avec elles, ces projets proposent des modèles pour mener à bien le travail des études latino-américaines coloniales et du dix-neuvième siècle dans la sphère publique.
The discharge of synthetic dyes from different industrial sources has become a global issue of concern. Enormous amounts are released into wastewater each year, causing concerns due to the high toxic consequences. Photocatalytic semiconductors appear as a green and sustainable form of remediation. Among them, graphitic carbon nitride (g-C3N4) has been widely studied due to its low cost and ease of fabrication. In this work, the synthesis, characterization, and photocatalytic study over methylene blue of undoped, B/S-doped, and exfoliated heterojunctions of g-C3N4 are presented. The evaluation of the photocatalytic performance showed that exfoliated undoped/S-doped heterojunctions with 25, 50, and 75 mass % of S-doped (g-C3N4) present enhanced activity with an apparent reaction rate constant (kapp) of 1.92 × 10–2 min–1 for the 75% sample. These results are supported by photoluminescence (PL) experiments showing that this heterojunction presents the less probable electron–hole recombination. UV–vis diffuse reflectance and valence band-X-ray photoelectron spectroscopy (VB-XPS) allowed the calculation of the band-gap and the valence band positions, suggesting a band structure diagram describing a type I heterojunction. The photocatalytic activities calculated demonstrate that this property is related to the surface area and porosity of the samples, the semiconductor nature of the g-C3N4 structure, and, in this case, the heterojunction that modifies the band structure. These results are of great importance considering that scarce reports are found concerning exfoliated B/S-doped heterojunctions.
Given the short time intervals in which short‐circuit faults occur in a power system, a certain time delay between the moment of a fault's inception in the system to the moment in which the fault is actually detected is introduced. In this small time margin, the high amplitudes of the fault current can deal significant damage to the power system. A technique to characterise different types of short circuit faults in a power system for real‐time detection, namely AB, BC, CA, ABC, AG, BG and CG faults (and normal operation), is presented based on the geometry of the curve generated by the Clarke transform of the three‐phase voltages of the power system. The process was conducted in real time using the HIL402 system and a Raspberry Pi 3, and all programming done in the Python programming language. It was concluded that the tested types of faults can be accurately characterised using the eigenvalues and eigenvectors of the matrix that characterises an ellipse associated with each fault: eigenvalues can be used to determine the fault inception distance and eigenvectors can be used to determine the type of fault that occurred. Next, the design of a machine learning model was done based on the previously mentioned characterisation technique. The model was embedded into a Raspberry Pi 3, thus enabling fault detection and classification in a base power system in real time. Finally, the accuracy of the model was tested under different measurement conditions, yielding satisfactory results for a selected set of conditions and overcoming the shortcomings presented in the current research, which do not perform detection and classification in real time.
Colombia is a Latin American outlier in that it has traditionally been a very violent country, yet at the same time remarkably democratic. This chapter explores Colombia’s puzzle from a political economy perspective, shedding light on the broader relationship between democracy and violence. The chapter studies some of the most important democratization reforms since Colombia’s independence 200 years ago. It argues that the reforms often failed to curb violence and sometimes even actively, though perhaps unintendedly, exacerbated violent political strife. Democratic reforms were unable to set the ground for genuine power-sharing. They were often implemented amidst a weak institutional environment that allowed powerful elites, the reforms’ ex-ante political losers, to capture the State and offset the benefits of the reforms for the broader society. We conclude by highlighting the implications of the argument for other countries facing democratic reforms, as well as for Colombia’s current peace-building efforts.
The present chapter includes a well-detailed introduction and the beginnings of HIPEC. Mechanism and role of temperature including different modalities to apply HIPEC procedure are well defined in this chapter. Special description has been done including general indications and the entire procedure step by step, with exhaustive details. Drugs used, dosage ranges in liquid and nanoparticles presentation used in HIPEC are described in a clear subject. Success and failure of HIPEC compared to clinical trials, demonstrating the limitations of the technique, are also mentioned. Finally, we got our opinion on HIPEC in colorectal cases fleshed out writing by an independent expert. We introduce with permission the concepts and the future of HIPEC with the emergence of new technology.
The aim of this study was to develop and achieve consensus on a cariology teaching framework for dental schools in Latin American Spanish-speaking countries. The Delphi process, with a ≥8 0% pre-defined participants' agreement, included three phases and a Coordinating Group. During the Preparation phase three panels of experts were selected and invited to participate: a) Regional academic/professional Dental Associations (Associations-Panel): n = 12; b) Regional Dental Schools (Dental-Schools-Panel): existing dental schools (n = 263) from the 19 Spanish-speaking regional countries; c) International academic/professional associations Peer Experts (Peer-Panel): n = 4. Based on consensus documents from Europe, Colombia, the Caribbean, USA, Chile and Spain, and updated scientific evidence, the Coordinating Group developed a baseline framework proposal of domains, main competencies (MC) and specific competencies (SC). The Consultation-Agreement and Consensus phases included three rounds of questionnaires with a step-wise sharing of the MC updated version of the consensus framework with the Dental-Schools-Panel and including SC with the Associations-Panel. Diverse communication strategies were used ( e.g ., independent google-form questionnaires and workshops). Consensus was reached after an on-site Associations-Panel workshop and secret voting, followed by an online meeting with the Peers-Panel. A total of 127 academic/professional institutions participated (Associations-Panel: 11, 91.6%; Dental-Schools-Panel: 112, 42.6%, all countries; Peers-Panel: 4, 100%). The baseline Cariology teaching framework of 5 domains, 10 MC and 92 SC underwent modifications after agreements for a final consensus framework consisting of 5 domains, 10 MC and 85 SC. A Core Cariology curriculum framework in Spanish for Latin American Dental Schools was successfully developed and agreed upon with regional dental academic and professional institutions.
Cervical cancer is one of the most dangerous and widespread illnesses afflicting women throughout the globe, particularly in East Africa and South Asia. In industrialised nations, the incidence of cervical cancer has consistently decreased over the past few decades. However, in developing countries, the reduction in incidence has been considerably slower, and in some instances, the incidence has increased. Implementing routine screenings for cervical cancer is something that has to be done to protect the health of women. Cervical cancer is famously difficult to diagnose and cure due to the slow rate at which it spreads and develops into more advanced stages of the disease. Screening for cervical cancer using a Pap smear, more often referred to as a Pap test, has the potential to detect the illness in its earlier stages. For the purpose of selecting features for this article, a gray level co-occurrence matrix (GLCM) technique was used. Following this step, classification is performed with methods such as convolutional neural network (CNN), support vector machine, and auto encoder. According to the findings of this experiment, the GLCM-CNN classifier proved to be the one with the highest degree of precision.
In the era of globalization and the deregulation of the air transportation industry, public and private stakeholders have been increasingly interested in making airports attractive for passengers and airlines. Multiple service-like indicators (i.e., satisfaction, experience, liking, and quality of service) have been used to evaluate transportation infrastructure and systems, including airport terminals. Despite literature providing a clear definition of the different indicators separately, the similarities and differences are not clear, nor is it clear whether they are equivalent and could be used interchangeably. The purpose of this paper is to further understanding of the roots and essence of the four frequently used service indicators (SIs) in airport terminals—namely satisfaction, liking, quality of service, and experience—by comparing regressors. Using a travelers’ perception survey ( N = 377) at the domestic terminal in Bogotá’s El Dorado Airport, we found that, despite their correlation, the four service proxies were, in essence, different from each other conceptually, meaning that they have to be carefully chosen for the successful evaluation of a terminal. Each SI comprises different categories, representing a unique user perception. Recognizing and acknowledging that all these terms are different furthers the transparency in defining what each indicator measures.
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13,417 members
Augusto Valderrama
  • Department of Biological Sciences
Juan Gabriel Ramirez
  • Department of Physics
Luis A. Guzman
  • Department of Civil & Environmental Engineering
Cra 1 Nº 18A- 12, Bogotá, Colombia
Head of institution
Alejandro Gaviria
+571 3394949