Intención de abandono en estudiantes de pregrado: factores y soluciones

El presente estudio abordó la problemática del abandono estudiantil desde un enfoque a priori, el cual fue se basó conceptual y metodológicamente en Suriñach et al (2007), Duque et al (2012), Duque (2013a) y Duque (2013b). El principal propósito fue medir el efecto que tiene la satisfacción y los resultados del aprendizaje de los estudiantes en su intención de abandono. Para lograr el objetivo se aplicó un cuestionario aplicado a los estudiantes activos de todos los pregrados de la Universidad EAFIT. El análisis se realizó por medio de un modelo de ecuaciones estructurales estimado con el algoritmo parcial de mínimos cuadrados (PLS). Los resultados evidencian que, en promedio, el efecto es 0.38, lo que significa que si se aumenta la satisfacción en una unidad, la intención de abandono disminuye en 0.25. Asimismo, se encontró que a mejores percepciones en los resultados del aprendizaje (afectivos y cognitivos), los estudiantes disminuyen su intención de abandono en 0.25.The present study addressed dropout intention problem from a priori perspective. Conceptually and methodologically it was based on Suriñach et al (2007), Duque et al (2012), Duque (2013a) y Duque (2013b). Measuring the effect from satisfaction and academic development to dropout intentions was the main purpose. To achieve this objective, we applied a survey with active students from all undergraduate programs at Universidad EAFIT. The analysis was carried out through structural equations based on the partial least squares algorithm (PLS). The results show that, on average, the effect is 0.38. It means that if students’ satisfaction would increase in one unit, dropout intention reduced in 0.25. At the same way, we found that better learning outcome perceptions (cognitive and affective), students decrease their dropout intention in 0.25

PT-symmetry from Lindblad dynamics in a linearized optomechanical system

We analyze a lossy linearized optomechanical system in the red-detuned regime under the rotating wave approximation. This so-called optomechanical state transfer protocol provides effective lossy frequency converter (quantum beam-splitter-like) dynamics where the strength of the coupling between the electromagnetic and mechanical modes is controlled by the optical steady-state amplitude. By restricting to a subspace with no losses, we argue that the transition from mode-hybridization in the strong coupling regime to the damped-dynamics in the weak coupling regime, is a signature of the passive parity-time (PT) symmetry breaking transition in the underlying non-Hermitian quantum dimer. We compare the dynamics generated by the quantum open system (Langevin or Lindblad) approach to that of the PT-symmetric Hamiltonian, to characterize the cases where the two are identical. Additionally, we numerically explore the evolution of separable and correlated number states at zero temperature as well as thermal initial state evolution at room temperature. Our results provide a pathway for realizing non-Hermitian Hamiltonians in optomechanical systems at a quantum level

MARINE INFLUENCE DURING LATE EOCENE IN EASTERN AND SOUTH EASTERN COLOMBIA

Durante el Eoceno Tardío en las Cuencas Subandinas de Colombia tuvo lugar la depositación de uno de los más importantes reservorios del país: la Formación Mirador. Diversos modelos deposicionales reconocen un ambiente típicamente fluvial para su base, y ambientes más transicionales para su tope. Sin embargo, la presencia de una influencia marina en el tope del Mirador es aún discutida, y la distribución geográfica de este probable evento es desconocida. Con el objeto de establecer la paleogeografía de esta ingresión marina se analizaron palinológicamente 77 pozos y 3 secciones ubicados en el Oriente de Colombia. La influencia marina en los sedimentos se estableció determinando la Paleosalinidad asociada mediante un Índice de Salinidad (SI), que describe la relación entre palinomorfos marinos y continentales. La ingresión marina está registrada en dos áreas: la primera, en la Cordillera Oriental y el Piedemonte Llanero Central; y la segunda, en la cuenca del Putumayo. El comportamiento de la paleosalinidad sugiere que al Sur, en la Cuenca del Putumayo, la ingresión marina invadió el territorio Colombiano en sentido S-N a través de la costa Ecuatoriana. Sin embargo, cómo ingresó a la Cordillera Oriental y al sector central del Piedemonte no es claro, y los modelos paleogeográficos propuestos no lo explican satisfactoriamente. Un nuevo modelo paleogeográfico para el Eoceno Tardío deberá ser planteado.   Palabras Claves: Eoceno Tardío; Palinología; Índice de Salinidad; Influencia Marina; Formación Mirador          During Late Eocene in the Colombian Subandean basins one of the most important oil bearing Rocks in Colombia was deposited: The Mirador Formation. Most of the depositional models proposed recognize a typically fluvial environment for the Mirador´s base and transitional environments for its top. These models disagree about a probable Marine Influence in the Mirador´s Top, and the geographical distribution of this event remains unknown. In order to determine the paleogeography of this event, 77 wells and 3 sections were palynologically analyzed. The presence of the marine influence in the sediments was determined using a Salinity Index (SI) which describes the reverse relationship between continental and marine palynomorphs. Marine Influence was recognized in two areas: the first one, in the Eastern Cordillera and the Central-Eastern Foothills; and the second one, in the Putumayo Basin. Paleosalinity patterns suggest that in the Putumayo Basin the marine ingression flooded in to the Colombian territory in a South-North direction, through the Ecuatorian Coast. How the Marine Ingression flooded into the Eastern Cordillera and Central-Eastern Foothills is not clear, and paleogeographical models proposed can not explain it. A new paleogeographical model for the Colombian Late Eocene considering this event must be proposed.   Key Words: Late Eocene; Palynology; Salinity Index; Marine Influence; Mirador Formation &nbsp

MARINE INFLUENCE DURING LATE EOCENE IN EASTERN AND SOUTH EASTERN COLOMBIA

Durante el Eoceno Tardío en las Cuencas Subandinas de Colombia tuvo lugar la depositación de uno de los más importantes reservorios del país: la Formación Mirador. Diversos modelos deposicionales reconocen un ambiente típicamente fluvial para su base, y ambientes más transicionales para su tope. Sin embargo, la presencia de una influencia marina en el tope del Mirador es aún discutida, y la distribución geográfica de este probable evento es desconocida. Con el objeto de establecer la paleogeografía de esta ingresión marina se analizaron palinológicamente 77 pozos y 3 secciones ubicados en el Oriente de Colombia. La influencia marina en los sedimentos se estableció determinando la Paleosalinidad asociada mediante un Índice de Salinidad (SI), que describe la relación entre palinomorfos marinos y continentales. La ingresión marina está registrada en dos áreas: la primera, en la Cordillera Oriental y el Piedemonte Llanero Central; y la segunda, en la cuenca del Putumayo. El comportamiento de la paleosalinidad sugiere que al Sur, en la Cuenca del Putumayo, la ingresión marina invadió el territorio Colombiano en sentido S-N a través de la costa Ecuatoriana. Sin embargo, cómo ingresó a la Cordillera Oriental y al sector central del Piedemonte no es claro, y los modelos paleogeográficos propuestos no lo explican satisfactoriamente. Un nuevo modelo paleogeográfico para el Eoceno Tardío deberá ser planteado.   Palabras Claves: Eoceno Tardío; Palinología; Índice de Salinidad; Influencia Marina; Formación Mirador          During Late Eocene in the Colombian Subandean basins one of the most important oil bearing Rocks in Colombia was deposited: The Mirador Formation. Most of the depositional models proposed recognize a typically fluvial environment for the Mirador´s base and transitional environments for its top. These models disagree about a probable Marine Influence in the Mirador´s Top, and the geographical distribution of this event remains unknown. In order to determine the paleogeography of this event, 77 wells and 3 sections were palynologically analyzed. The presence of the marine influence in the sediments was determined using a Salinity Index (SI) which describes the reverse relationship between continental and marine palynomorphs. Marine Influence was recognized in two areas: the first one, in the Eastern Cordillera and the Central-Eastern Foothills; and the second one, in the Putumayo Basin. Paleosalinity patterns suggest that in the Putumayo Basin the marine ingression flooded in to the Colombian territory in a South-North direction, through the Ecuatorian Coast. How the Marine Ingression flooded into the Eastern Cordillera and Central-Eastern Foothills is not clear, and paleogeographical models proposed can not explain it. A new paleogeographical model for the Colombian Late Eocene considering this event must be proposed.   Key Words: Late Eocene; Palynology; Salinity Index; Marine Influence; Mirador Formation &nbsp

Drainage And Sedimentary Response Of The Northern Andes And The Pebas System To Miocene Strike-slip Tectonics: A Source To Sink Study Of The Magdalena Basin

Miocene strike-slip tectonics was responsible for creating and closing short-lived (ca. 6 Ma) passages and the emergence of isolated topography in the Northern Andes. These geological events likely influenced the migration and/or isolation of biological populations. To better understand the paleogeography of the Miocene hinterland and foreland regions in the Northern Andes, we conducted a source-to-sink approach in the Magdalena Basin. This basin is located between the Central and Eastern Cordilleras of Colombia and contains an ample Miocene record, which includes Lower Miocene fine-grained strata and Middle Miocene to Pliocene coarsening-up strata. Our study presents a new data set that includes detrital U–Pb zircon ages (15 samples), sandstone petrography (45 samples) and low-temperature thermochronology from the Southern Central Cordillera (19 dates); which together with previously published data were used to construct a paleogeographical model of the Miocene hinterland and foreland regions in the Northern Andes. The evolution of the Magdalena Basin during the Miocene was characterized by playa and permanent lake systems at ca. 17.5 Ma, which may be related to a marine incursion into NW South America and western Amazonia. The appearance of Eocene to Miocene volcanic sources in the Honda Group after ca. 16 Ma suggests the development of fluvial passages, which connected the Pacific with the western Amazonia and Caribbean regions. These passages were synchronous with a time of Miocene exhumation and topographic growth (ca. 16 to 10 Ma) in the Central Cordillera and the transition from lacustrine to fluvial deposition in the Magdalena Basin. Middle to Late Miocene strike-slip deformation promoted by oblique plate convergence and the oblique collision of the Panamá-Chocó Block likely explains the synchronous along-strike fragmentation and exhumation in the Central Cordillera

Chondrocyte Turnover in Lung Cartilage

Cartilage is a highly differentiated connective tissue that forms mechanical support to soft tissues and is important for bone development from fetal period to puberty. It is conformed by chondrocytes and extracellular matrix. It is generally believed that adult cartilage has no capacity to renewal. A delicate balance between cell proliferation and cell death ensures the maintenance of normal tissue morphology and function. Stem cells play essential roles in this process. Mesenchymal stem cells (MSCs) can give rise to multiple lineages including bone, adipose and cartilage. Nestin protein was initially identified as a marker for neural stem cells, but its expression has also been detected in many types of cells, including MSCs. In vivo, chondrocyte turnover has been almost exclusively studied in articular cartilage. In this chapter we will review the findings about the chondrocyte turnover in lung cartilage. We have presented evidence that there exist nestin-positive MSCs in healthy adulthood that participates in the turnover of lung cartilage and in lung airway epithelium renewal. These findings may improve our knowledge about the biology of the cartilage and of the stem cells, and could provide new cell candidates for cartilage tissue engineering and for therapy for devastating pulmonary diseases

Functional upgrading in China’s export processing sector

Functional upgrading occurs when a firm acquires more sophisticated functions within an existing value chain. In this paper, we analyze if there is evidence of this type of upgrading in China’s export processing regime by investigating dynamics in the relative prevalence of Import & Assembly (IA) versus Pure Assembly (PA) processing trade over the period 2000-2013. Firms in both regimes provide similar manufacturing services to foreign companies, but IA firms also conduct the sophisticated tasks of quality control, searching, financing and storing imported materials. Consistent with a trend of functional upgrading, we show that the share of IA trade in total processing trade has increased rapidly during the period 2000-2006, both overall and within product categories. Furthermore, we find that this trend has gone hand in hand with improvements in a sector’s labor productivity and unit values. Against expectations, we find that this process has slowed down notably during the period 2006-2013.status: publishe

Sublittoral soft bottom communities and diversity of Mejillones Bay in northern Chile (Humboldt Current upwelling system)

The macrozoobenthos of Mejillones Bay (23°S; Humboldt Current) was quantitatively investigated over a 7-year period from austral summer 1995/1996 to winter 2002. About 78 van Veen grab samples taken at six stations (5, 10, 20 m depth) provided the basis for the analysis of the distribution of 60 species and 28 families of benthic invertebrates, as well as of their abundance and biomass. Mean abundance (2,119 individuals m-2) was in the same order compared to a previous investigation; mean biomass (966 g formalin wet mass m-2), however, exceeded prior estimations mainly due to the dominance of the bivalve Aulacomya ater. About 43% of the taxa inhabited the complete depth range. Mean taxonomic Shannon diversity (H', Log e) was 1.54 ± 0.58 with a maximum at 20 m (1.95 ± 0.33); evenness increased with depth. The fauna was numerically dominated by carnivorous gastropods, polychaetes and crustaceans (48%). About 15% of the species were suspensivorous, 13% sedimentivorous, 11% detritivorous, 7% omnivorous and 6% herbivorous. Cluster analyses showed a significant difference between the shallow and the deeper stations. Gammarid amphipods and the polychaete family Nephtyidae characterized the 5-mzone, the molluscs Aulacomya ater, Mitrella unifasciata and gammarids the intermediate zone, while the gastropod Nassarius gayi and the polychaete family Nereidae were most prominent at the deeper stations. The communities of the three depth zones did not appear to be limited by hypoxia during non-El Niño conditions. Therefore, no typical change in community structure occurred during El Niño 1997–1998, in contrast to what was observed for deeper faunal assemblages and hypoxic bays elsewhere in the coastal Humboldt Current system

Polygenic adaptation and negative selection across traits, years and environments in a long-lived plant species (Pinus pinaster Ait., Pinaceae)

17 Pág.A decade of genetic association studies in multiple organisms suggests that most complex traits are polygenic; that is, they have a genetic architecture determined by numerous loci, each with small effect-size. Thus, determining the degree of polygenicity and its variation across traits, environments and time is crucial to understand the genetic basis of phenotypic variation. We applied multilocus approaches to estimate the degree of polygenicity of fitness-related traits in a long-lived plant (Pinus pinaster Ait., maritime pine) and to analyse this variation across environments and years. We evaluated five categories of fitness-related traits (survival, height, phenology, functional, and biotic-stress response) in a clonal common-garden network planted in contrasted environments (over 20,500 trees). Most of the analysed traits showed evidence of local adaptation based on Qst -Fst comparisons. We further observed a remarkably stable degree of polygenicity, averaging 6% (range of 0%-27%), across traits, environments and years. We detected evidence of negative selection, which could explain, at least partially, the high degree of polygenicity. Because polygenic adaptation can occur rapidly, our results suggest that current predictions on the capacity of natural forest tree populations to adapt to new environments should be revised, especially in the current context of climate change.This study was funded by the Spanish Ministry of Economy and Competitiveness through projects RTA2010-00120-C02- 02 (CLONAPIN), CGL2011-30182- C02- 01 (AdapCon) and AGL2012-40151- C03- 02 (FENOPIN). The study was also supported by the “Initiative d’Excellence (IdEx) de l’Université de Bordeaux - Chaires d'installation 2015” (EcoGenPin) and the European Union's Horizon 2020 research and innovation programme under grant agreement No 773383 (B4EST)Peer reviewe