2.1 Estudios de doctorado y postdoctorado

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https://hdl.handle.net/20.500.12390/329

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  • Publicación
    A GWAS in Latin Americans highlights the convergent evolution of lighter skin pigmentation in Eurasia
    (Nature Publishing Group, 2019)
    Adhikari K.
    ;
    Mendoza-Revilla J.
    ;
    Sohail A.
    ;
    Fuentes-Guajardo M.
    ;
    Lampert J.
    ;
    Chacón-Duque J.C.
    ;
    Hurtado M.
    ;
    Villegas V.
    ;
    Granja V.
    ;
    Acuña-Alonzo V.
    ;
    Jaramillo C.
    ;
    Arias W.
    ;
    Lozano R.B.
    ;
    Everardo P.
    ;
    Gómez-Valdés J.
    ;
    Villamil-Ramírez H.
    ;
    Silva de Cerqueira C.C.
    ;
    Hunemeier T.
    ;
    Ramallo V.
    ;
    Schuler-Faccini L.
    ;
    Salzano F.M.
    ;
    Gonzalez-José R.
    ;
    Bortolini M.-C.
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    Canizales-Quinteros S.
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    Gallo C.
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    Poletti G.
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    Bedoya G.
    ;
    Rothhammer F.
    ;
    Tobin D.J.
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    Fumagalli M.
    ;
    Balding D.
    ;
    Ruiz-Linares A.
    We report a genome-wide association scan in >6,000 Latin Americans for pigmentation of skin and eyes. We found eighteen signals of association at twelve genomic regions. These include one novel locus for skin pigmentation (in 10q26) and three novel loci for eye pigmentation (in 1q32, 20q13 and 22q12). We demonstrate the presence of multiple independent signals of association in the 11q14 and 15q13 regions (comprising the GRM5/TYR and HERC2/OCA2 genes, respectively) and several epistatic interactions among independently associated alleles. Strongest association with skin pigmentation at 19p13 was observed for an Y182H missense variant (common only in East Asians and Native Americans) in MFSD12, a gene recently associated with skin pigmentation in Africans. We show that the frequency of the derived allele at Y182H is significantly correlated with lower solar radiation intensity in East Asia and infer that MFSD12 was under selection in East Asians, probably after their split from Europeans.
  • Publicación
    A hybrid high-order formulation for a Neumann problem on polytopal meshes
    (Wiley, 2019)
    Bustinza, Rommel
    ;
    Munguia-La-Cotera, Jonathan
    In this work, we study a hybrid high-order (HHO) method for an elliptic diffusion problem with Neumann boundary condition. The proposed method has several features, such as: (a) the support of arbitrary approximation order polynomial at mesh elements and faces on polytopal meshes, (b) the design of a local (element-wise) potential reconstruction operator and a local stabilization term, that weakly enforces the matching between local element- and face-based on degrees of freedom, and (c) cheap computational cost, thanks to static condensation and compact stencil. We prove the well-posedness of our HHO formulation, and obtain the optimal error estimates, according to previous study. Implementation aspects are thoroughly discussed. Finally, some numerical examples are provided, which are in agreement with our theoretical results.
  • Publicación
    A low-cost measurement device for recording perceptions of thermal comfort
    (Institute of Physics Publishing, 2020)
    Molina J.R.
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    Nakama V.L.
    ;
    Lefebvre G.
    In this article, we describe the implementation of a low-cost device that registers perceptions of thermal comfort. The parameters of relative humidity (RH), temperature, thermal sensation (cold, cool, neutral, warn, hot) and clothing worn by people are collected. The design and validation of the device in an indoor environment are explained, and the calibration curves of the temperature and relative humidity sensors are obtained. The measurement results for the device from 10 people are shown. The study was carried out in the village of Imata (high Andean zone), at 4700 masl in the south of Peru. © Published under licence by IOP Publishing Ltd.
  • Publicación
    A new assessment in total and extreme rainfall trends over central and southern Peruvian Andes during 1965-2010
    (Wiley Online Library, 2018)
    Heidinger, H
    ;
    Carvalho, L
    ;
    Jones, C
    ;
    Posadas, A
    ;
    Quiroz, R
    Understanding the spatio-temporal variability of rainfall over mountainous regions such as the Andes is crucial for the maintenance of water resources and ecosystems. This study provided a comprehensive analysis of the signal, statistical significance and spatial pattern of rainfall trends in central and southern Peruvian Andes (CSPA) from 1965 to 2010. Rainfall from 47 quality-controlled rain gauge stations was examined using the hydrologic calendar year. Total and extreme rainfall indices proposed by the Expert Team on Climate Change Detection and Indices (ETCCDI) were calculated and trends were examined with Mann–Kendall test and Sen's slope estimator. Significant regional patterns of changes in rainfall extremes were investigated and compared with previous studies. Four major regions of stations were identified based on principal component analysis and clustering techniques: Amazon, central Pacific, southern Pacific and Titicaca basins. Statistically significant trend patterns showed that the annual total rainfall has decreased in the Amazon basin, despite the increase in the number of rainy days and some extreme rainfall indices. Decrease in 1-day and 5-day yearly maximum rainfall was observed in central Pacific, along with an increase in the number of wet days. Positive trends in indices related to the intensity of very strong daily rainfall were detected in southern Pacific. Titicaca basin showed an increase in the intensity of rainfall extremes. Rainfall variability and trends were evaluated during contrasting El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). Most stations in the CSPA exhibited positive (negative) anomaly of total and extreme rainfall indices (consecutive dry days) during La Niña (El Niño) years. Positive (negative) anomalies of annual total rainfall and consecutive dry days during positive (negative) PDO occurred in the Amazon, southern Pacific and Titicaca basins, respectively. The ENSO–PDO conditions may have influenced the complex and mostly non-statistically significant long-term trends in CSPA.
  • Publicación
    A new electrochemical platform based on carbon black paste electrode modified with α-cyclodextrin and hierarchical porous carbon used for the simultaneous determination of dipyrone and codeine
    (Elsevier Inc., 2021)
    Wong, Ademar
    ;
    Cardenas Riojas, Andy
    ;
    Baena-Moncada, Angélica M.
    ;
    Sotomayor, Maria D.P.T.
    The present study reports the simultaneous determination of dipyrone and codeine by a simple, fast and low-cost method using carbon black paste electrode (CBPE) modified with α-cyclodextrin (CD) and hierarchical porous carbon (HPC). Using optimum conditions, the CD-HPC/CBPE sensor proposed in this study presented excellent electrochemical catalysis. Based on square wave voltammetry (SWV) analysis, linear concentration ranges of 0.46 to 35 µmol L−1 and 0.5 to 38 µmol L−1 were obtained for dipyrone and codeine, respectively, with nanomolar limits of detection for both analytes. The proposed sensor exhibited good stability, satisfactory repeatability and high sensibility in the determination of the analytes of interest. The application of the sensor in real samples was found to be successful, with recovery rates ranging from 96 to 106%. The method proposed in this study was found to be reliable for the simultaneous detection of dipyrone and codeine in different matrices. © 2021 Elsevier B.V.
  • Publicación
    A note on the zeros of approximations of the Ramanujan Ξ -function
    (Springer, 2020)
    Chirre A.
    ;
    Castañón O.V.
    In this paper we review the study of the distribution of the zeros of certain approximations for the Ramanujan Ξ -function given by Ki (Ramanujan J 17(1):123–143, 2008), and we provide new proofs of his results. Our approach is motivated by the ideas of Velásquez (J Anal Math 110:67–127, 2010) in the study of the zeros of certain sums of entire functions with some condition of stability related to the Hermite–Biehler theorem. © 2020, The Author(s).
  • Publicación
    A Novel EEG-Based Four-Class Linguistic BCI
    (IEEE, 2019)
    Jahangiri, Amir
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    Achanccaray, David
    ;
    Sepulveda, Francisco
    In this work, we present a novel EEG-based Linguistic BCI, which uses the four phonemic structures "BA", "FO", "LE", and "RY" as covert speech task classes. Six neurologically healthy volunteers with the age range of 19-37 participated in this experiment. Participants were asked to covertly speak a phonemic structure when they heard an auditory cue. EEG was recorded with 64 electrodes at 2048 samples/s. The duration of each trial is 312ms starting with the cue. The BCI was trained using a mixed randomized recording run containing 15 trials per class. The BCI is tested by playing a simple game of "Wack a mole" containing 5 trials per class presented in random order. The average classification accuracy for the 6 users is 82.5%. The most valuable features emerge after Auditory cue recognition (~100ms post onset), and within the 70-128 Hz frequency range. The most significant identified brain regions were the Prefrontal Cortex (linked to stimulus driven executive control), Wernicke's area (linked to Phonological code retrieval), the right IFG, and Broca's area (linked to syllabification). In this work, we have only scratched the surface of using Linguistic tasks for BCIs and the potential for creating much more capable systems in the future using this approach exists.
  • Publicación
    A Novel Fuzzy Probabilistic Clustering Algorithm for Satellite Image Segmentation
    (2018 IEEE International Conference on Fuzzy Systems (FUZZ-IEEE), 2018)
    Mantilla, L
    ;
    Yari, Y
    ;
    Meza-Lovon, G
    Satellite Image Segmentation is a task widely investigate since we can extract and analyze information of an image. In satellite image, the information of each one of the bands must be considered. We propose a new method based on the New Fuzzy Centroid Model and includes spatial information. Furthermore, we use the occurrence of each intensity value in a particular band and the Gaussian function in order to compute the degree of contribution of pixels in the neighborhood. By incorporating spatial information (global and local), we improve the clustering process and consequently, a better segmentation is obtained. This paper reports preliminary results of experiments that show that the proposed algorithm performs accurately on a real data set. For the evaluation of the algorithm, different cluster validity indexes are employed.
  • Publicación
    A One Health approach to prevention, treatment, and control of campylobacteriosis
    (Lippincott Williams and Wilkins, 2019)
    Schiaffino F.
    ;
    Platts-Mills J.
    ;
    Kosek M.N.
    Purpose of review: To review recent findings regarding the control and treatment of campylobacteriosis. Recent findings: The application of improved diagnostics has led to an upward shift in the attributable burden of Campylobacter infections, in both the United States and Europe as well as in resource-poor settings. Increased focus has brought a fundamental feature of campylobacteriosis - the ability to cause relapsing disease back into focus, and expanding data on antimicrobial resistance has lead from a switch in first-line therapy for severe diarrhea from quinolones to azithromycin in most contexts, even as evidence of expanding macrolide resistance emerges. Summary: Campylobacter spp. infection is a common infection worldwide. Antibiotic-resistant Campylobacter spp. has become an emerging threat with the increase in industrial poultry production, as well as the broad use of antibiotics in both animals and humans. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.
  • Publicación
    A peptidomic approach of meat protein degradation in a low-sodium fermented sausage model using autochthonous starter cultures
    (Elsevier Ltd, 2018)
    de Almeida M.A.
    ;
    Saldaña E.
    ;
    da Silva Pinto J.S.
    ;
    Palacios J.
    ;
    Contreras-Castillo C.J.
    ;
    Sentandreu M.A.
    ;
    Fadda S.G.
    Fermented sausage technology is currently compromised in decreasing the addition of NaCl. Use of starter cultures with peptidogenic potential could be a valuable strategy that can mask or hide off flavors produced by the use of NaCl substituents. In the present work, the peptidogenic potential of four lactic acid bacteria species was evaluated in a low-sodium beaker sausage (BS) model. Using a peptidomic approach, a total of 86 low molecular weight (LMW) peptides were accurately identified, mostly derived from myofibrillar proteins, especially actin, which generated 53 peptides. The BS inoculated with L. curvatus CRL705 generated 56 LMW peptides, followed by Enterococcus (E.) mundtii CRL35 with 43 peptides. In addition, BS inoculated with Lactobacillus (L.) plantarum and with L. sakei produced higher amino acid amounts over time as compared to the rest of BS models, highlighting the importance of both, time and sample effect on the overall free amino acid generation. The presence of each LAB strain in BS models generated a unique profile of small peptides and amino acids that could serve as a distinctive biochemical trait to differentiate specific fermented products. According to these results, E. mundtii and L. sakei, which are compatible between them, are proposed as the most efficiently adapted to low-sodium conditions. The use of selected strains during the processing of low-sodium fermented sausages could have a positive effect on the production of small peptides and free amino acids.
  • Publicación
    A Retrospective Analysis of Sociodemographic and Hematologic Characteristics Associated with Achieving Optimal Hydroxyurea Therapy in Children with Sickle Cell Disease
    (Lippincott Williams and Wilkins, 2018)
    George P.E.
    ;
    Bazo-Alvarez J.C.
    ;
    Sheehan V.A.
    Hydroxyurea (HU) has proven hematologic and clinical benefits, especially when escalated to the maximum tolerated dose (MTD). We reviewed clinical data from patients with sickle cell disease (January 2011 to 2016) to determine baseline sociodemographic and laboratory parameters associated with reaching HU MTD without significant delays. In total, 210 patients (mean HU start age, 6.6 y) were included. Initial Kaplan-Meier event analysis showed 1 year to be an inflection point for reaching MTD. In total, 116 patients (55%) reached MTD in <1 year, with 56 (27%) taking >1 year to reach MTD and 38 (18%) patients not successfully reaching MTD during follow-up. In both crude and adjusted analyses, age at HU start was found to be significantly and inversely associated with reaching MTD within 1 year. The data presented, specifically the inflection point of reaching MTD at 1 year and the association of young HU start age with reaching MTD within a year, suggest that successful achievement of MTD may be facilitated by starting patients on HU at a young age and that older patients should receive additional intervention to attain MTD within 1 year. Patients who do not achieve MTD within a year may need the most extensive intervention.
  • Publicación
    A study of observation scales based on felzenswalb-huttenlocher dissimilarity measure for hierarchical segmentation
    (Springer Verlag, 2019)
    Cayllahua-Cahuina E.
    ;
    Cousty J.
    ;
    Guimarães S.
    ;
    Kenmochi Y.
    ;
    Cámara-Chávez G.
    ;
    de Albuquerque Araújo A.
    Hierarchical image segmentation provides a region-oriented scale-space, i.e., a set of image segmentations at different detail levels in which the segmentations at finer levels are nested with respect to those at coarser levels. Guimarães et al. proposed a hierarchical graph based image segmentation (HGB) method based on the Felzenszwalb-Huttenlocher dissimilarity. This HGB method computes, for each edge of a graph, the minimum scale in a hierarchy at which two regions linked by this edge should merge according to the dissimilarity. In order to generalize this method, we first propose an algorithm to compute the intervals which contain all the observation scales at which the associated regions should merge. Then, following the current trend in mathematical morphology to study criteria which are not increasing on a hierarchy, we present various strategies to select a significant observation scale in these intervals. We use the BSDS dataset to assess our observation scale selection methods. The experiments show that some of these strategies lead to better segmentation results than the ones obtained with the original HGB method.
  • Publicación
    A three-dimensional plasticity-damage constitutive model for timber under cyclic loads
    (Elsevier Ltd, 2018)
    Sirumbal-Zapata, LF
    ;
    Malaga-Chuquitaype, C
    ;
    Elghazouli, AY
    The performance of timber structures is governed by the nonlinear response at their connections, where high deformation levels and stress concentrations are developed, particularly when subjected to load reversals. To date, no constitutive model for wood under cyclic load exists which is able to incorporate its most important failure modes while considering plastic deformations and cyclic stiffness and strength degradation simultaneously. This paper presents the formulation and implementation of a plasticity-damage model with these characteristics within a continuum mechanics approach. The theoretical framework of both plasticity and damage models is described, and a detailed derivation of the constitutive equations required for their computational implementation and coupling as well as the return mapping and iterative algorithms for their integration are presented. The damage evolution process is handled by two independent scalar variables for tension and compression. A general orthotropic plasticity yield surface with isotropic hardening is employed to incorporate timber plastic flow in compression. A closed-form expression for the plasticity-damage consistent tangent operator is derived. It is demonstrated that the proposed constitutive model captures all the key characteristics required for an accurate modelling of timber under large deformation levels until failure.
  • Publicación
    A unified splitting algorithm for composite monotone inclusions
    (Heldermann Verlag, 2020)
    Oré-Albornoz E.
    ;
    Mahey P.
    ;
    Ocaña-Anaya E.
    Operator splitting methods have been recently concerned with inclusions problems based on composite operators made of the sum of two monotone operators, one of them associated with a linear transformation. We analyze here a general and new splitting method which indeed splits both operator proximal steps, and avoiding costly numerical algebra on the linear operator. The family of algorithms induced by our generalized setting includes known methods like Chambolle-Pock primal-dual algorithm and Shefi-Teboulle Proximal Alternate Direction Method of Multipliers. The study of the ergodic and non ergodic convergence rates show similar rates with the classical Douglas-Rachford splitting scheme. We end with an application to a multi-block convex optimization model which leads to a generalized Separable Augmented Lagrangian Algorithm.
  • Publicación
    Active transpressional tectonics in the Andean forearc of southern Peru quantified by 10Be surface exposure dating of an active fault scarp
    (Blackwell Publishing Ltd, 2017)
    Benavente C.
    ;
    Zerathe S.
    ;
    Audin L.
    ;
    Hall S.R.
    ;
    Robert X.
    ;
    Delgado F.
    ;
    Carcaillet J.
    ;
    ASTER Team
    ;
    Aumaître G.
    ;
    Bourlès D.L.
    ;
    Keddadouche K.
    Our understanding of the style and rate of Quaternary tectonic deformation in the forearc of the Central Andes is hampered by a lack of field observations and constraints on neotectonic structures. Here we present a detailed analysis of the Purgatorio fault, a recently recognized active fault located in the forearc of southern Peru. Based on field and remote sensing analysis (Pléiades DEM), we define the Purgatorio fault as a subvertical structure trending NW-SE to W-E along its 60 km length, connecting, on its eastern end, to the crustal Incapuquio Fault System. The Purgatorio fault accommodates right-lateral transpressional deformation, as shown by the numerous lateral and vertical plurimetric offsets recorded along strike. In particular, scarp with a 5 m cumulative throw is preserved and displays cobbles that are cut and covered by slickensides. Cosmogenic radionuclide exposure dating (10Be) of quartzite cobbles along the vertical fault scarp yields young exposure ages that can be bracketed between 0 to 6 ka, depending on the inheritance model that is applied. Our preferred scenario, which takes in account our geomorphic observations, implies at least two distinct rupture events, each associated with ~3 and ~2 m of vertical offset. These two events plausibly occurred during the last thousand years. Nevertheless, an interpretation invoking more tectonic events along the fault cannot be ruled out. This work affirms crustal deformation along active faults in the Andean forearc of southern Peru during the last thousand years. ©2017. American Geophysical Union. All Rights Reserved.
  • Publicación
    Acylpolyamine mygalin as a TLR4 antagonist based on molecular docking and in vitro analyses
    (MDPI AG, 2020)
    Espinoza-Culupú, Abraham
    ;
    Vázquez-Ramírez, Ricardo
    ;
    Farfán-López, Mariella
    ;
    Mendes, Elizabeth
    ;
    Sato, Maria Notomi
    ;
    da Silva Junior, Pedro Ismael
    ;
    Marques Borges, Monamaris
    Toll-like receptors (TLRs) are transmembrane proteins that are key regulators of innate and adaptive immune responses, particularly TLR4, and they have been identified as potential drug targets for the treatment of disease. Several low-molecular-weight compounds are being considered as new drug targets for various applications, including as immune modulators. Mygalin, a 417 Da synthetic bis-acylpolyamine, is an analog of spermidine that has microbicidal activity. In this study, we investigated the effect of mygalin on the innate immune response based on a virtual screening (VS) and molecular docking analysis. Bone marrow-derived macrophages and the cell lines J774A.1 and RAW 264.7 stimulated with lipopolysaccharide (LPS) were used to confirm the data obtained in silico. Virtual screening and molecular docking suggested that mygalin binds to TLR4 via the protein myeloid differentiation factor 2 (MD-2) and LPS. Macrophages stimulated by mygalin plus LPS showed suppressed gene expression of tumor necrosis factor (TNF-α), interleukine 6 (IL-6), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), as well as inhibition of signaling protein p65 of the nuclear factor κB (NF-κB), resulting in decreased production of nitric oxide (NO) and TNF-α. These results indicate that mygalin has anti-inflammatory potential, being an attractive option to be explored. In addition, we reinforce the importance of virtual screening analysis to assist in the discovery of new drugs. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
  • Publicación
    Advances and gaps in studies on healthy meat products and their relationship with regulations: The Brazilian scenario
    (Elsevier Ltd, 2021)
    Rios-Mera, Juan D.
    ;
    Saldaña, Erick
    ;
    Patinho, Iliani
    ;
    Selani Miriam, M.
    ;
    Contreras-Castillo, Carmen J.
    Background: Strategies for the reformulation of meat products respond to consumers’ demand for healthier food alternatives. The reduction of salt or sodium and animal fat, and the substitution of synthetic antioxidants by natural ones have been a subject of study for Brazilian researchers for many years, but the industrial application of new technological alternatives presents the challenge of adapting to regulations related to the processing of meat products. Scope and approach: Reports by Brazilian researchers from 2011 to 2019 were collected from the Scopus database and their abstracts were submitted to a textual analysis to visualize the trend of studies over these years. The relationship between the approaches/ingredients proposed in the studies and the Brazilian regulation was discussed. Key findings and conclusions: Numerous alternatives for natural antioxidants and salt and animal fat substitutes have been proposed, but Brazilian regulation is restrictive with respect to the use of natural antioxidants and the most studied salt substitute in meat products. However, studies using alternatives more compatible with Brazilian regulations have been proposed. For industrial application purposes, some flavorings and spices may have antioxidant activity and act as natural antioxidants, delaying the lipid oxidation of meat products; the sodium content can be reduced using several morphologies or sizes of salt particles; and the incorporation of oils rich in polyunsaturated fatty acids, embedded in oleogels and microparticles using encapsulating proteins, seem to be a viable alternative for reducing animal fat in meat products. © 2021 Elsevier Ltd
  • Publicación
    Agaricus bisporus mushroom as partial fat replacer improves the sensory quality maintaining the instrumental characteristics of beef burger
    (Elsevier Ltd, 2021)
    Patinho, Iliani
    ;
    Selani, Miriam Mabel
    ;
    Saldaña, Erick
    ;
    Bortoluzzi Teixeira, Ana Clara
    ;
    Rios-Mera, Juan Dario
    ;
    da Silva, Claudia Maria
    ;
    Kushida, Marta
    ;
    Contreras-Castillo, Carmen J.
    The effect of Agaricus bisporus (AB) mushroom as a fat replacer in beef burgers was evaluated. Four treatments were compared: control (0% AB, 20% fat) and 3 treatments with partial fat replacement: AB 5% (5% AB, 15% fat); AB 10% (10% AB, 10% fat); AB 15% (AB 15%, 5% fat). Mushroom addition increased moisture content and yield and decreased cooking loss and diameter reduction of the burgers. Formulations with the highest AB concentrations were lighter and redder than the control. AB incorporation affected texture, resulting in less hard and less chewy products. In general, lipid oxidation increased during the storage time, however the lowest values were observed in AB 15%, i.e. the lowest fat content and the presence of AB increased the oxidative stability. AB 10% and AB 15% had good overall liking and were sensorially characterized as juicy, tender and flavorsome burgers. The partial replacement of animal fat by AB is a promising strategy for developing a low-fat burger. © 2020 Elsevier Ltd
  • Publicación
    Alternativas económicas para la conservación de los bosques húmedos del Perú con énfasis en la región Ucayali
    (Universidad Nacional Autónoma de México, 2016-03-01)
    Estrada Tuesta, Zenayda Emilia
    Los Bosques Húmedos del Perú tienen el potencial para ser una fuente abundante de riquezas. Según el informe “Estado de los Bosques del Mundo 2014”, publicado por la Organización de las Naciones Unidas para la Agricultura y la Alimentación 1 (FAO), el Perú cuenta con más de 72 millones de hectáreas de cobertura forestal. De la superficie total (128.5 millones de hectáreas) se calcula que el 60% son bosques, lo que ubica al país en el segundo lugar en cuanto a la extensión cubierta por bosques naturales en Sudamérica y en el noveno lugar a nivel mundial. Según la Organización de las Naciones Unidas para la Agricultura (FAO, 2014), alrededor del 89% de los bosques de Perú es primario y el país ocupa el cuarto lugar a nivel mundial con respecto a la extensión de sus bosques tropicales. Según la clasificación de suelos por la capacidad de uso mayor, el 80% del territorio nacional peruano corresponde a tierras aptas para la producción forestal y a tierras de protección. Existen más de 800 mil hectáreas de plantaciones forestales y unos 10 millones de hectáreas de tierras aptas para la reforestación. Pese a su gran potencial, la contribución del sector forestal a la economía nacional es muy reducida: menos del 1% del Producto Bruto Interno (PIB) 2 nacional (FAO, 2014). De la misma manera, según el informe “Evaluación de los Recursos Forestales Mundiales 2011” de la Organización para la Agricultura y la Alimentación (FAO), del 2000 al 2011, la pérdida anual neta de los bosques del mundo fue de 5.2 millones de hectáreas. América del Sur fue la región más afectada en ese periodo, puesto que perdió alrededor de 4 millones de hectáreas por año. La depredación desmedida de sus recursos forestales ha seguido inmutablemente su curso. La tasa actual de deforestación es en promedio de 725 hectáreas de bosques destruidos por día, ocasionando importantes problemas ecológicos-ambientales y socio-económicos como la pérdida de biomasa, conversión de uso de suelos, escasez de agua, tala ilegal, así como incremento de la pobreza entre otros. Todo ello por la ausencia de una política económica ecológica y ambiental, que permita realizar la valoración efectiva de los bosques y sus servicios 2 dentro de las cuentas nacionales. El valor económico de los recursos naturales y los ecosistemas son desconocidos y mucho menos cuantificados, lo que impide un análisis y un manejo adecuado de los bienes y servicios ambientales (Gorfinkiel, 1999). La valoración económica de los bosques tropicales amazónicos es un tema que está cobrando interés en el sector forestal peruano. El conocimiento del potencial productivo y su significado económico permiten demostrar la importancia de conservar el recurso e identificar políticas que contribuyan a una mayor viabilidad económica, a través del manejo sostenible de los recursos que albergan estos bosques (Malky, 2007).
  • Publicación
    An algorithm of feasible directions to mixed nonlinear complementarity problems and applications
    (Universidad Nacional de Ingeniería, 2017)
    Ramírez Gutiérrez, Ángel Enrique
    ;
    Ramírez Gutiérrez, Ángel Enrique
    This work investigates the Feasible Direction Algorithm using interior points applied to the Mixed Nonlinear Complementarity Problem and some applications. This algorithm is based in Feasible Directions Algorithm for Nonlinear Complementarity Problem, which is described briefly. The proposed algorithm is important because many mathematical models can be written as mixed nonlinear complementarity problem. The principal idea of this algorithm is to generate, at each iteration, a sequence of feasible directions with respect to the region, defined by the inequality conditions, which are also monotonic descent directions for one potential function. Then, an approximate line search along this direction is performed in order to define the next iteration. Global and asymptotic convergence properties for the algorithm are proved. In order to validade the robustness the algorithm is tested on several benchmark problems, that were found in the literature, considering the same para- meters. In this work one dimensional models describing Oxygen Diffusion inside one cell and In Situ Combustion are also presented together with bidimensional model of the Elastic-Plastic Torsion Problem. These models are re-written as nonlinear com¬plementarity problem and mixed nonlinear complementarity problem. These new formulations are discretized by Finite Diference Scheme or Finite Element Method and, for its discrete forms, the algorithm will be applied. The numerical results are compared with direct numerical simulation using Newton’s method (in the case of Oxygen Diffusion and In Situ Combustion) or exact solution (in the case of Elastic- Plastic Torsion Problem). It is shown that the obtained results are in good agreement with the asymptotic analysis. For the In situ combustion model the corresponding Riemann’s problem is studied in order to validate numerical solutions.