The quark anti-quark potential and the cusp anomalous dimension from a TBA equation

We derive a set of integral equations of the TBA type for the generalized cusp anomalous dimension, or the quark antiquark potential on the three sphere, as a function of the angles. We do this by considering a family of local operators on a Wilson loop with charge L. In the large L limit the problem can be solved in terms of a certain boundary reflection matrix. We determine this reflection matrix by using the symmetries and the boundary crossing equation. The cusp is introduced through a relative rotation between the two boundaries. Then the TBA trick of exchanging space and time leads to an exact equation for all values of L. The L = 0 case corresponds to the cusped Wilson loop with no operators inserted. We then derive a slightly simplified integral equation which describes the small angle limit. We solve this equation up to three loops in perturbation theory and match the results that were obtained with more direct approaches.Instituto de Física La Plat

The quark anti-quark potential and the cusp anomalous dimension from a TBA equation

We derive a set of integral equations of the TBA type for the generalized cusp anomalous dimension, or the quark antiquark potential on the three sphere, as a function of the angles. We do this by considering a family of local operators on a Wilson loop with charge L. In the large L limit the problem can be solved in terms of a certain boundary reflection matrix. We determine this reflection matrix by using the symmetries and the boundary crossing equation. The cusp is introduced through a relative rotation between the two boundaries. Then the TBA trick of exchanging space and time leads to an exact equation for all values of L. The L = 0 case corresponds to the cusped Wilson loop with no operators inserted. We then derive a slightly simplified integral equation which describes the small angle limit. We solve this equation up to three loops in perturbation theory and match the results that were obtained with more direct approaches.Instituto de Física La Plat

Financial Stability Governance and Communication

Resumen de la comunicación[EN] We investigate how differences in governance frameworks across central banks explain their financial stability communication strategies and the effect of these strategies on the evolution of each country’s financial cycle. To do so, we propose a simple conceptual framework that explains how central banks conduct their communication strategy, which eventually affects the evolution of financial conditions. To empirically validate our framework, we use a database with the financial stability governance characteristics of 24 central banks and the sentiment conveyed in the financial stability reports published by these central banks. We find that, after observing a deterioration of financial conditions, central banks participating in interagency financial stability committees or with an oversight role transmit a calmer message than banks without these characteristics. We also find that the effect of communication on the evolution of the financial cycle depends on each central bank's governance framework. In particular, communication by central banks participating in an interagency financial stability committee or with a financial supervisory role has an alleviating effect on the deterioration of financial conditions.Londono, JM.; Claessens, S.; Correa, R.; Mislang, N. (2018). Financial Stability Governance and Communication. En 2nd International Conference on Advanced Reserach Methods and Analytics (CARMA 2018). Editorial Universitat Politècnica de València. 262-262. https://doi.org/10.4995/CARMA2018.2018.8577OCS26226

Taxonomía y biogeografía del género hormigas Megalomyrmex Forel (Hymenoptera: Formicidae) en Ecuador

El género neotropical de hormigas Megalomyrmex es revisado taxonómicamente para Ecuador y sus patrones de distribución utilizando un enfoque panbiogeográfico son analizados. Datos morfológicos apoyan el reconocimiento de 19 especies válidas y 2 especies nuevas para la ciencia. Se propone el siguiente esquema taxonómico: grupo de Leoninus: M. bidentatus Fernández & Baena, M. cyendyra Brandão, M. foreli Emery, M. glaesarius Kempf, M. leoninus Forel, M. pacova Brandão, M. staudingeri Emery, M. sp. nov. A; grupo de Modestus: M. caete Brandão, M. cupecuara Brandão, M. modestus Emery; grupo de Pusillus: M. drifti Kempf, M. incisus M. R. Smith; grupo de Silvestrii: M. cuatiara Brandão, M. mondabora Brandão, M. mondaboroides Longino, M. piriana Brandão, M. silvestrii Wheeler, M. symmetochus Wheeler, M. tasyba Brandão, M. sp. nov. B, M. sp. (cf. cuatiara)

Comparación por intervalos entre diferentes métodos de estimación de la media de la distribución Poisson

The construction of confidence intervals for the estimate of the parameter of the Poisson distribution is an important problem in applied statistic work. We reviewed different procedures for its construction and we carried out a simulation study to analyze the performance of thereal confidence levels when comparing them to the theoretical levels.La construcción de intervalos de confianza para la estimación del parámetro de la distribución Poisson es un problema importante en el trabajo estadístico aplicado. Se revisan diferentes procedimientos para su construcción y se realiza un estudio de simulación para mostrar que para muestras grandes los procedimientos basados en el criterio de la raíz y el de razón de verosimilitudes tienen un comportamiento similar y más eficiente que el de los otros procedimientos usualmenteutilizados

Comparación por intervalos entre diferentes métodos de estimación de la media de la distribución Poisson

La construcción de intervalos de confianza para la estimación del parámetro de la distribución Poisson es un problema importante en el trabajo estadístico aplicado. Se revisan diferentes procedimientos para su construcción y se realiza un estudio de simulación para mostrar que para muestras grandes los procedimientos basados en el criterio de la raíz y el de razón de verosimilitudes tienen un comportamiento similar y más eficiente que el de los otros procedimientos usualmente utilizados

Molecular phylogenetics of the Pristimantis lacrimosus species group (Anura: Craugastoridae) with the description of a new species from Colombia

The Pristimantis lacrimosus species group, with 24 species distributed in the Neotropics, is a group of arboreal frogs commonly inhabiting bromeliads. Previous studies have claimed the group to be monophyletic but few species have been included in phylogenetic analyses. In this paper, we included five additional species from the northern Andes in Colombia and tested the monophyly of this phenetic group using genetic data under a Bayesian approach. Our results show that the P. lacrimosus group represents two distant and unrelated clades. Clade “A” is endemic to Colombia while Clade “B” encompasses species distributed in Central America, Ecuador and Peru. For the first time, we reveal the phylogenetic position of P. boulengeri and a new species is described. The new taxon is most closely related to P. brevifrons from southwestern Colombia with a genetic distance of 4.3% for 16S and 10.6% for COI. Our results suggest, one more time, that morphological similarity among species in the most diverse vertebrate genus not necessarily agree with its evolutionary history and that more effort in alpha taxonomy needs to be done in order to understand the tremendous radiation of this lineage in the Neotropics

Modifying the histogram using deciles

Presentamos algunas modificaciones que producen un histograma basado en los deciles, el cual es visualmente más informativo que el histograma de igual longitud de clases y el boxplot de cuartiles,  más comúnmente utilizados para representar un conjunto de datos. Se muestra también la convergencia asintótica de los deciles lo mismo que su convergencia conjunta para llegar a la conclusión de que los límites de clase de las barras son realmente estimaciones puntuales y que consecuentemente pueden estimarse por  intervalos de confianza. El investigador adquiere cierto dominio de la información en el sentido de que conoce el porcentaje de datos que cae dentro de cada barra; además, en la medida que aumente el tamaño poblacional, podrá extender el histograma al número de clases que desee, teniendo dominio siempre sobre el número de datos que cae en cada una de estas clases. Discutimos algunos problemas del boxplot e ilustramos  ambas gráficas utilizando los datos de la media maratón de Medellín 2009.   ABSTRACT We present some modifications that produce a histogram based on deciles which is visually more informative than the equal-width histogram and the quartile boxplot currently used   to represent a dataset. We also present the asymptotic convergence of the deciles and their joint asymptotic convergence to conclude that the class limits actually are point estimations and, consequently,  can be estimated through confidence intervals. The researcher has certain control of the information, since he or she knows the part of the dataset pertaining to each class; besides, the larger the sample size is the larger the number of classes can ever he or she choose knowing the amount of data included into each class. We also discuss some problems of the boxplot , and illustrate both the histogram and the boxplot using the Medellín 2009 half-marathon data.

DNAM-1 and the TIGIT/PVRIG/TACTILE Axis: Novel Immune Checkpoints for Natural Killer Cell-Based Cancer Immunotherapy

Natural killer (NK) cells are lymphocytes of the innate immune response characterized by their role in the destruction of tumor cells. Activation of NK cells depend on a fine balance between activating and inhibitory signals mediated by different receptors. In recent years, a family of paired receptors that interact with ligands of the Nectin/Nectin-like (Necl) family has attracted great interest. Two of these ligands, Necl-5 (usually termed CD155 or PVR) and Nectin-2 (CD112), frequently expressed on different types of tumor cells, are recognized by a group of receptors expressed on T and NK cells that exert opposite functions after interacting with their ligands. These receptors include DNAM-1 (CD226), TIGIT, TACTILE (CD96) and the recently described PVRIG. Whereas activation through DNAM-1 after recognition of CD155 or CD112 enhances NK cell-mediated cytotoxicity against a wide range of tumor cells, TIGIT recognition of these ligands exerts an inhibitory effect on NK cells by diminishing IFN-γ production, as well as NK cell-mediated cytotoxicity. PVRIG has also been identified as an inhibitory receptor that recognizes CD112 but not CD155. However, little is known about the role of TACTILE as modulator of immune responses in humans. TACTILE control of tumor growth and metastases has been reported in murine models, and it has been suggested that it negatively regulates the anti-tumor functions mediated by DNAM-1. In NK cells from patients with solid cancer and leukemia, it has been observed a decreased expression of DNAM-1 that may shift the balance in favor to the inhibitory receptors TIGIT or PVRIG, further contributing to the diminished NK cell-mediated cytotoxic capacity observed in these patients. Analysis of DNAM-1, TIGIT, TACTILE and PVRIG on human NK cells from solid cancer or leukemia patients will clarify the role of these receptors in cancer surveillance. Overall, it can be speculated that in cancer patients the TIGIT/PVRIG pathways are upregulated and represent novel targets for checkpoint blockade immunotherapy

Evidence for subaerial development of the Caribbean oceanic plateau in the Late Cretaceous and palaeo-environmental implications

The formation of oceanic plateaus in the Pacific in the Mesozoic has been proposed to create major environmental impacts, including global anoxic events OAE-1 in the Aptian (ca. 120 Ma) and OAE-2 in the Cenomanian–Turonian (ca. 90 Ma). However, our understanding of the formation of these large volcanic systems and their environmental effects are strongly limited by difficulties in accessing them and characterising their volcanic evolution. In particular, it remains significant to determine whether Pacific oceanic plateaus experience a phase of subaerial volcanic activity as this has critical implications in terms of their environmental impacts. Herein we provide the first unequivocal evidence for an emergent volcanic phase of the Caribbean oceanic plateau in the Late Cretaceous. This subaerial phase is evidenced by accreted oceanic sequences in Colombia that include fallout tuffs with accretionary lapilli and lahar deposits. This facies assemblage, recognised for the first time in an oceanic plateau, reflects phreatomagmatic eruptions coeval with subaerial erosion on an oceanic island. This result, combined with previous evidence of subaerial development of the Ontong Java Plateau and Shatsky Rise, suggests that syn-volcanic emergence of oceanic plateaus was common in the Pacific during the Mesozoic. Although temporal and spatial scales of these emergences remain poorly constrained it confirms that emergence of the Caribbean plateau in the Late Cretaceous (ca. 90 Ma) could have actively contributed to atmospheric changes and the establishment of OAE-2. Significantly, emergence of the Caribbean plateau occurred synchronously to the beginning of its tectonic displacement between the Americas. We propose that this unusual volcanic and tectonic evolution led to drastic reduction of the flow of Pacific oxygenated bottom waters into the early Atlantic basin, leading to a series of regional anoxic events previously documented between the Coniacian and Santonian (OAE-3, ca. 89 to 84 Ma). In addition, emergence of the Caribbean Plateau in the early inter-American seaway could have facilitated migration of terrestrial organisms between the Americas in the Late Cretaceous. The formation of the Caribbean plateau had therefore a large range of possible environmental effects, from atmospheric to palaeo-oceanographic and biotic impacts