Papers by MIGUEL LEONARDO CORREA ESPINOSA
Dada la realidad histórica del deterioro del suelo en Chile y el aporte de los distintos cultivos... more Dada la realidad histórica del deterioro del suelo en Chile y el aporte de los distintos cultivos para revertir este proceso la Facultad de Ciencias Forestales de la Universidad de Concepción decidió organizar en conjunto con la Corporación Nacional de la Madera, el presente Simposio. El objetivo de este seminario "Erosión, cultivos y recuperación de suelos", es ayudar al intercambio de ideas y conocimientos al respecto, así como la búsqueda de soluciones relacionadas con el uso de los suelos utilizados en plantaciones.
There has been so much debate on the increasing use of formal mathematical methods in Eco-nomics.... more There has been so much debate on the increasing use of formal mathematical methods in Eco-nomics. Although there are some studies tackling these issues, those use either a little amount of papers, a small amount of scholars or cover a short period of time. We try to overcome these challenges constructing a database characterizing the main socio-demographic and academic output of a survey of 438 scholars divided into three groups: Economics Nobel Prize winners; scholars awarded with at least one of six prestigious recognitions in Economics; and academic faculty ran-domly selected from the top twenty Economics departments worldwide. Our results provide concrete measures of mathematization in Economics by giving statistical evidence on the increasing trend of number of equations and econometric outputs per article. We also show that for each of these variables there have been four structural breaks and three of them have been increasing ones. Fur-thermore, we found that the training an...
Scripta Nova-revista Electronica De Geografia Y Ciencias Sociales, 2012
La cuestion nacional viene siendo invocada con particular fuerza desde diferentes sectores de la ... more La cuestion nacional viene siendo invocada con particular fuerza desde diferentes sectores de la academia a nivel internacional y constituye uno de los aspectos mas relevantes presentes en la literatura geografica, referida en este caso a la geografia politica. La tension global-nacional-regional-local, pone de manifiesto la necesidad de asumir la comprension de las logicas del ejercicio del poder, pero al mismo tiempo devela la presencia de elementos que subyacen las configuraciones territoriales actuales, obligando a urgar en la historicidad de los procesos geohistoricos mismos. El texto del articulo centra su atencion en tres aspectos criticos, tomando como referente la configuracion territorial de los paises andino amazonicos de Suramerica (Bolivia, Peru, Ecuador y Colombia): el primero, relacionado con las herencias de una configuracion territorial, que acumula elementos tanto de las sociedades ancestrales indigenas como de la sociedad colonial que perduro a lo largo de tres si...
Social Science Research Network, 2021
Firms allocate workers to clients to provide services. On the job, workers acquire skills that in... more Firms allocate workers to clients to provide services. On the job, workers acquire skills that increase their client-specific productivity and therefore raise the probability that clients poach them. In this paper, we advance the understanding of this important, yet understudied feature of service industries. We show, both theoretically and empirically, that in order to mitigate poaching risk firms may forgo potential productivity gains by moving workers from one client to the other. Focusing on a security service-industry firm in Colombia, we find that an increase in client-specific experience increases both workers’ productivity and probability that the workers are poached. After a policy change that forbids talent poaching, the firm sharply decreased the frequency of rotation, especially for workers who were more likely to be poached before the policy change. The theoretical model we propose is consistent with these empirical patterns and substantiates the broad applicability of ...
We study the effect of apprenticeship programs on firms and welfare, using novel administrative d... more We study the effect of apprenticeship programs on firms and welfare, using novel administrative data on the universe Colombian manufacturing firms with at least 10 workers, and a unique reform to apprenticeship regulation. The reform simultaneously establishes apprentice quotas that vary discontinuously in firm size and lowers apprentices' wages. We begin by documenting that the policy is successful in increasing the number of trained apprentices more than threefold. However, the reform also induces significant firm size distortions driven by heterogeneous firm responses. In sectors with high skill requirements, firms avoided hiring apprentices decreasing their size and bunching just below the regulation thresholds. In contrast, firms in low-skilled sectors, increase their size and bunch just above the regulation thresholds in order to be able to hire more apprentices. As a consequence, the regulation results in most apprentices being trained in low-skilled sectors. We develop a...
This thesis contains three chapters examining firms’ behaviour and decision making when they seek... more This thesis contains three chapters examining firms’ behaviour and decision making when they seek to influence policies in the US through lobbying activities. The first chapter studies the main trade-off that firms face when they face the decision to integrate or outsource knowledge workers. The chapter proposes a model that predicts that firms requiring large firm-specific skills, or low levels of issue-specific skills, or facing a large number of transactions will integrate as opposed to outsource the service provider. Using a newly collected dataset on the US federal lobbying industry, I conduct firm-fixed effect estimations and I find strong evidence supporting the theoretical predictions. To provide further empirical evidence, I exploit a quasi-experiment that the Oil and Gas industry faced: The BP oil spill. The spill increased the issue-specific skills needed to conduct advocacy activities and in line with the theory developed in the chapter, I show that the affected industry...
SUMMARY Using the information from the two main online scientific databases, Scopus and Web of Sc... more SUMMARY Using the information from the two main online scientific databases, Scopus and Web of Science (WoS), the scientific productivity of Chilean research institutions associated with the forestry sector was analyzed for the period 2000-2011. The following factors were analyzed: number of publications indexed in WoS and Scopus, citation frequency, impact indexes, h-Index, international contribution, self-citing and subject area of publications. The articles selected indicated affiliation either to faculties that offered undergraduate Forestry Programs in March 2012 or to public and private institutions associated with the forestry sector. Using this information, a ranking of scientific productivity for each institution was established according to the number of publications registered in WoS. Results show that the universities which offered Forestry Programs published 515 articles in WoS indexed journals and 625 in Scopus, corresponding to 88.5 and 85.0 % of the publications in t...
Revista Mexicana de Ciencias Pecuarias, 2006
The aim of this study was to determine the soil-erodibility parameters of the WEPP erosion model ... more The aim of this study was to determine the soil-erodibility parameters of the WEPP erosion model (Water Erosion Prediction Project) for an Andisol used to raise cattle in the Patzcuaro Lake watershed, Michoacan, Mexico. It was used a solenoid-operated rainfall simulator. Interrill detachment was measured in 0.5 m wide, 1.2 m long plots, and the detachment of flowing water was measured in 1 m wide, 3 m long plots, in both cases it was used a completely randomized design with four replications. Soil moisture affected runoff and interrill erosion, whereas the bulk density of the surface layer was lower in the cropland use than under the rangeland use. The interrill and rill erodibility parameters were 774.7x103 kg sec m-4, and 0.5x10-4 sec m-1. These values in comparison with those reported in the literature permit to establish that the rangeland Andisol under study showed a moderated susceptibility to interrill erodibility and low detchment of flowing water. Soil compaction due to liv...
SSRN Electronic Journal, 2020
We study firm responses to a large-scale change in apprenticeship regulation in Colombia. The ref... more We study firm responses to a large-scale change in apprenticeship regulation in Colombia. The reform requires firms to train, setting apprentice quotas that vary discontinuously in firm size. We document strong heterogeneity in responses across sectors, where firms in sectors with high skill requirements tend to avoid training apprentices, while firms in low-skill sectors seek apprentices. Guided by these reduced-form findings, we structurally estimate firms' training costs. Especially in high-skill sectors, many firms face large training costs, limiting their willingness to train apprentices. Yet, we find substantial overall benefits of expanding apprenticeship training, in particular when the supply of trained workers increases in general equilibrium. Finally, we show that counterfactual policies taking into account heterogeneity across sectors can deliver similar benefits from training while inducing less distortions in the firm-size distribution and in the allocation of resources across sectors.
Chilean journal of agricultural research, 2010
The leaf area index (LAI) of a vineyard (Vitis vinifera L.) cv. Cabernet Sauvignon located in the... more The leaf area index (LAI) of a vineyard (Vitis vinifera L.) cv. Cabernet Sauvignon located in the commune of Cauquenes, Maule Region in Chile, was estimated from digital images obtained with a commercial camera using two indirect methods: Leaf Area Gap and Brightness (LAGB) and Photogrammetric Leaf Area Quantification System (PLAQS). The latter requires deleafing of the grapevine. In a normalized difference vegetation index (NDVI) map, three points of vine vigor were selected: high, medium, and low for which horizontal and vertical images were obtained. Images were filtered with the Arc View GIS 3.1 program to provide only leaf images and corresponding pixel numbers. Image area and square meters per linear meter were calculated. The best models were selected from three linear regression adjustments: i) LAI of LAGB vertical images of with LAI of PLAQS, ii) LAI of PLAQS horizontal images with and, iii) LAI of both types of images with PLAQS. The parameters in all models were significant. Adjustment between the LAGB and PLAQS vertical images provides greater simplicity and easy calculation since it requires only a vertical image to estimate LAI. Images thus obtained can accurately estimate LAI in this type of cultivar.
Ra Ximhai, 2012
En este trabajo investigación, se estudia la capacidad de adsorción de tolueno sobre una serie de... more En este trabajo investigación, se estudia la capacidad de adsorción de tolueno sobre una serie de siete combinaciones de óxidos de aluminio, cerio y zirconio, preparados por el método solgel mediante cromatografía de gases en un intervalo de temperatura de 200°C a 250°C. El área superfi cial, es alta para las cuatro muestras que contienen alúmina, entre 196 y 272 m2/g, mientras que las tres restantes poseen áreas superficiales menores a 40 m2/g. La adsorción de tolueno se observóen las siete muestras, sin embargo, las cuatro que contienen alúmina presentan isotermas cóncavas lo que indica adsorción favorable, mientras que en las de ceriazirconia, la forma de las isotermas es convexa indicando adsorción no favorable, lo anterior se confi rma al observar menor cantidad de tolueno adsorbido comparada con las muestras anteriores. La temperatura que favorece la adsorción en la mayoría de las muestras es la de 200 °C.
Natural Product Communications, 2013
Quillaja saponaria (Quillay), an evergreen tree found in Chile, is one of the main sources of sap... more Quillaja saponaria (Quillay), an evergreen tree found in Chile, is one of the main sources of saponins. Quillaja saponins have hypocholesterolaemic, anticarcinogenic, antioxidant and pesticidal properties, and are used as adjuvants for vaccines. Samples of Quillay growing at three zones in O'Higgins Region, Chile (Coastal, Central and Mountain zones) were analyzed for content of saponins and physiological status. The results revealed differences in the content of saponins depending on the zone of sample collection. The highest contents were found in samples from the Mountain zone, where the highest saponin contents were accompanied by the lowest foliar nitrogen contents, the highest antioxidant activity and the highest carotenoid contents. The results suggest a physiological and adaptive mechanism of saponins in plants to survive under unfavourable environmental conditions. The results have important implications for a theoretical basis for the design of a reasonable harvest, to...
Revista Forestal Mesoamericana Kurú, 2017
Las plantaciones dendroenergéticas han mostrado rendimientos que han sido sitio-específicos. En a... more Las plantaciones dendroenergéticas han mostrado rendimientos que han sido sitio-específicos. En algunos países se está iniciando una producción a gran escala sin conocer los niveles de productividad que las mismas tendrán en función a la disponibilidad de recursos de un sitio. Modelos ecofisiológicos permiten predecir la productividad de plantaciones forestales a partir de la estimación de algunos parámetros ambientales y de cada especie. El modelo 3PG ha mostrado capacidad de estimación en plantaciones de Eucalyptus. Hasta hoy, no existen experiencias de uso de este modelo en plantaciones dendroenergéticas de alta densidad, esta publicación trata de la parametrización de 3PG para estimar con mayor certeza la productividad de plantaciones dendroenergéticas a nivel sitio-específico. Para evaluar la predicción del modelo 3PG en plantaciones dendroenergéticas se utilizaron parámetros de la literatura para la especie Eucalyptus camaldulensis y se evaluó la eficiencia del modelo en plant...
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 28, 2017
Unlike their isocyano and isothiocyanato analogues, isocyanato esters remain almost unexplored as... more Unlike their isocyano and isothiocyanato analogues, isocyanato esters remain almost unexplored as formal 1,3-dipoles in asymmetric catalytic reactions. In this communication, the first asymmetric formal [3+2] cycloaddition involving isocyanato esters and electrophilic alkenes is reported. Diisopropyl 2-isocyanatomalonate reacts with α,β-unsaturated N-(o-anisidyl) imines in the presence of a Mg(OTf)2-BOX complex to give highly substituted chiral pyrrolidinones featuring a conjugate exocyclic double bond with excellent yields and enantiomeric excesses up to 99%. Several transformations of the resulting heterocycles, including the synthesis of a pyroglutamic acid derivative have been carried out.
Organic & biomolecular chemistry, Jan 13, 2017
Copper triflate-BOX complexes catalyse the enantioselective conjugate addition of methyl malonate... more Copper triflate-BOX complexes catalyse the enantioselective conjugate addition of methyl malonate to β-trifluoromethyl-α,β-unsaturated imines to give the corresponding enamines bearing a trifluoromethylated stereogenic centre with good yields, and diastereo- and enantioselectivities. The usefulness of the method has been shown with the synthesis of optically active β-trifluoromethyl δ-amino esters and optically active trifluoromethyl piperidones.
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Papers by MIGUEL LEONARDO CORREA ESPINOSA