La curva de rendimientos a plazo y las expectativas de tasas de interés en el mercado de renta fija en Colombia 2002-2007

¿Cómo se incorporan la expectativas de las tasas de interés en la estructura de tipos de interés en Colombia? Las dos principales teorías propuestas en este sentido son la Hipótesis de las Expectativas (HE) y la Hipótesis de prima por liquidez (HPL). Este estudio contrasta ambas teorías tanto para las tasas de los TES como las de los CDTs, empleando modelos econométricos de series de tiempo que controlan por la persistencia de las tasas y su heterocedasticidad. Los resultados soportan la HPL, consistente con el hecho de que en Colombia, las tasas de largo plazo tienden a ser mayores que las de corto plazo. De otro lado, las tasas de largo plazo presentan algún poder predictivo sobre las tasas futuras de corto plazo, consistente con la HE.How does the yield curve incorporate the expectations on the Colombian future short-term interest rates?. Two theories have been proposed to explain it: the Expectation Hypothesis and the Liquidity Preference Hypothesis. This paper tests both theories for the TES yield curve as well as for the CDT yield curve, using time-series models that account for the persistence and heteroskedasticity of the interest rates. The results support the Liquidity Preference Hypothesis, consistent with the fact that in Colombia long-term rates have been consistently higher than short-term rates. However we found evidence of some predictive power of the long-term rates on the future short term rates, consistent with the Expectation Hypothesis

Contributions of cluster shape and intercellular adhesion to epithelial discohesion and emergent dynamics in collective migration

As a physical system, a cell interacts with its environment through physical and chemical processes. The cell can change these interactions through modification of its environment or its own composition. This dissertation presents the overarching hypothesis that both biochemical regulation of intercellular adhesion and physical interaction between cells are required to account for the emergence of cluster migration and collective dynamics observed in epithelial cells. Collective migration is defined as the displacement of a group of cells with transient or permanent cell-cell contacts. One mode, cluster migration, plays an important role during embryonic development and in cancer metastasis. Despite its importance, collective migration is a slow process and hard to visualize, and therefore it has not been thoroughly studied in three dimensions (3D). Based on known information about cluster migration from 2D studies of epithelial sheets and 3D single cell migration, this dissertation presents theoretical and experimental techniques to assess the independent contribution of physical and biochemical factors to 3D cluster migration. It first develops two computational models that explore the interaction between cells and the ECM and epithelial discohesion. These discrete mechanistic models reveal the need to account for intracellular regulation of adherens junctions in space and time within a cluster. Consequently, a differential algebraic model is developed that accounts for cross-reactivity of three pathways in a regulatory biochemical network: Wnt/β-catenin signaling, protein N-glycosylation, and E-cadherin adhesion. The model is tested by matching predictions to Wnt/β-catenin inhibition in MDCK cells. The model is then incorporated into a self-propelled particle (SPP) model, creating the first SPP model for study of adhesive mammalian cellular systems. MDCK cell clusters with fluorescent nuclei are grown, seeded, and tracked in 3D collagen gels using confocal microscopy. They provide data on individual cell dynamics within clusters. Borrowed from the field of complex systems, normalized velocity is used to quantify the order of both in vitro and simulated clusters. An analysis of sensitivity of cluster dynamics on factors describing physical and biochemical processes provides new quantitative insights into mechanisms underlying collective cell migration and explains temporal and spatial heterogeneity of cluster behavior

How does information disclosure affect liquidity? Evidence from an Emerging Market

Cross-sectional models positively relate firm information disclosure with stock liquidity, but dynamic models in news releases days show an opposite relation. We address this puzzle by studying the effects of information arrival on liquidity and its determinants. We use trade and quote data from Colombia for 2015 and 2016, along with the complete database of news releases as reported by companies to the regulator. The results of Panel data and PVAR models suggest that news releases increase both informed and uninformed trading. All in all, the temporal negative effect of news releases on liquidity is explained by increasing asymmetric information

Nicardipine for Hypertension following Aortic Coarctectomy and Superior Cavopulmonary Anastomosis

Background: Literature on the use of nicardipine, a dihydropyridine calcium channel antagonist, in children recovering from cardiac surgery is sparse and, to our knowledge, nonexistent in children with single ventricle anatomy. We aimed to report our experience with nicardipine in these patient populations. Methods: We performed a retrospective review of children recovering from aortic coarctectomy or superior cavopulmonary anastomoses who received nicardipine for hypertension at our institution between 2007 and 2013. Hemodynamic variables prior to and after nicardipine initiation were compared using paired t tests. Results: Seven children recovering from aortic coarctectomy (median age 8.6 months, range: 1.5 months-7.9 years) and four children recovering from superior cavopulmonary anastomosis (median age: seven months, range: five-nine months) were reviewed. For all patients, at six hours after initiation of nicardipine, mean systolic blood pressure was significantly decreased, 123 ± 19 versus 103 ± 14 mm Hg (P = .001), as were diastolic blood pressure, 68 ± 20 versus 53.5 ± 10 mm Hg (P = .041), and sodium nitroprusside dose, 4.3 ± 2.9 versus 1.3 ± 1.7 mcg/kg/min (P = .002). Further, within 24 hours, serum lactate decreased from 1.45 ± 0.82 to 0.81 ± 0.29 mg/dL (P = .016). Heart rate, blood urea nitrogen, and serum creatinine measurements were statistically unchanged. Conclusions: Nicardipine effectively decreased blood pressure without apparent adverse events in a small cohort of children with postoperative hypertension while recovering from aortic coarctectomy or superior cavopulmonary anastomosis. Further research comparing nicardipine to more conventional titratable antihypertensive agents in these patient populations is warranted

Registro

Esta sección es un medio de comunicación para divulgar las actividades académicas y de investigación de la Facultad de Comunicación de la Universidad de Medellín

Comportamiento fenológico de Euterpe oleracea (Arecaceae) en bosques inundables del Chocó biogeográfico

ResumenEuterpe oleracea Mart. (Arecaceae) es una palma cespitosa y dominante en bosques de zonas inundables de la cuenca del río Atrato, Colombia. Es considerada de importancia económica por el palmito que se extrae de ella y por los múltiples productos que se derivan de sus frutos. Se estudió la fenología reproductiva de Euterpe oleracea en 2 comunidades vegetales: murrapal mixto, donde E. oleracea ocurre junto a otras especies, y murrapal puro, dominado casi en su totalidad por E. oleracea. Los registros fenológicos se llevaron a cabo en 2 periodos: entre octubre de 1999 y diciembre de 2001, en ambos tipos de bosque; y entre octubre de 2006 y mayo de 2009, sólo en el murrapal mixto. La fenología reproductiva de Euterpe oleracea respondió a un patrón anual en ambos ecosistemas; sin embargo, las épocas de mayor producción de flores y frutos no coincidieron entre ellos. Se encontró una correlación significativa entre la precipitación y las fenofases, frutos verdes y frutos maduros en el murrapal puro; lo que sugiere un efecto de la inundabilidad sobre la producción temporal de flores y frutos. En el murrapal mixto no se halló relación significativa entre la pluviosidad y las fenofases reproductivas, probablemente debido a que en esta posición topográfica la inundación durante la estación lluviosa no fue tan severa y, por tanto, no alcanzó a cubrir los neumatóforos de las palmas.AbstractEuterpe oleracea Mart. (Arecaceae) is a clustered palm tree occurring in seasonally flooded areas of the Atrato river basin, where it forms homogeneous forests. This palm has economic importance because of the production of palm hearts and numerous products derived from its fruits. The reproductive phenology of Euterpe oleracea was studied in 2 forest types: mixed murrapal, where other species occur, and pure murrapal, almost totally dominated by this palm tree. Phenological observations were made in 2 periods: from October 1999 to December 2001 in both forest types, and from October 2006 to May 2009 in the mixed murrapal only. The reproductive phenology showed an annual pattern in both ecosystems; however, the timing of flowering and fruiting in each forest type was different. A significant correlation was found between rainfall and reproductive structures (fruits) in the pure murrapal, suggesting an effect of flooding on timing of flowering and fruiting. Contrarily, no significant correlation was found in the mixed murrapal, probably because flooding during rainy season was less severe in this topographic position, and therefore, water did not cover the palm pneumatophores