The Political Economy of Exchange Rate Policy in Colombia

This paper looks into the political economy forces that helped shape exchange rate policy in Colombia since the early 1960s. As witnessed by the remarkable longevity of the managed crawl, Colombian exchange rate policies since 1967 did not take the form of major regime changes. Policy shifts came about through variations in the rate of crawl, varying degrees of administrative restrictions on capital flows and, on occasions, ad-hoc measures to generate multiple exchange rates.

Flavored axions and the flavor problem

A Peccei-Quinn~(PQ) symmetry is proposed, in order to generate in the Standard Model~(SM) quark sector a realistic mass matrix ansatz with five texture-zeros. Limiting our analysis to Hermitian mass matrices we show that this requires a minimum of 4 Higgs doublets. This model allows assigning values close to 1 for several Yukawa couplings, giving insight into the origin of the mass scales in the SM. Since the PQ charges are non-universal the model features Flavor-Changing Neutral Currents~(FCNC) at the tree level. From the analytical expressions for the FCNC we report the allowed region in the parameter space obtained from the measurements of branching ratios of semileptonic meson decays.Comment: 20 pages, 2 figure

Diseño un controlador robusto basado en observador para el modelo lineal de un helicóptero de un grado de libertad (VTOL)

Este artículo propone un controlador basado en observador para un modelo de helicóptero tipo VTOL de un grado de libertad. El objetivo de control es mantener la posición del VTOL en un punto de operación, a pesar de las incertidumbres ocasionadas por inexactitud en el modelo y ruido en las mediciones. El controlador y el observador son diseñados con base en algoritmos que inducen modos deslizantes en el sistema en lazo cerrado, ofreciendo características de robustez y convergencia en tiempo finito. Los resultados de simulación muestran un buen desempeño del esquema propuesto tanto en condiciones de ausencia de ruido como cuando se consideran mediciones ruidosas.Universidad Nacional de ColombiaCinvestavColcienciasBanco Mundia

Most influential journals and authors in digital business research: A bibliometric analysis

In the last few decades many firms have been making large investments in e-commerce applications, digital technologies or the use of the Internet in several business activities and processes, giving rise to the notions of digital business and digital economy. Consequently, the number of academic articles on digital business has grown exponentially. The aim of this study is to present the evolution of academic research in digital business between 1990 and 2015. The main contribution is to provide an overview of the current academic state of the art in digital business research. The analysis focuses on identifying the most productive and influential journals in digital business research, as well as the leading authors in the field. The results show a strong increase in digital business research during the last fifteen years due to the development of a good number of specialized journals of information systems. We suggest that the field of business research should expand beyond its traditional boundaries and embrace a more multidisciplinary perspective

Estudio de enfermedades progresivas usando un modelo de Markov de estados múltiples

ResumenLos factores de riesgo y su grado de asociación con una enfermedad progresiva, tal como la enfermedad de Alzheimer o el cáncer de hígado, puede identificarse usando modelos epidemiológicos;algunos ejemplos de estos modelos  incluyen los de región logística, Poisson,Log-lineales, regresión lineal y mixtos.[Salazar JC, Iral R. Estudio de enfermedades progresivas usando un modelo de Markov de estados múltiples. MedUNAB 2005; 8:202-7].Palabras clave: Enfermedad de Alzheimer, marcadores genéticos, modelos de estados múltiples, datos longitudinales, dependencia de Markov

Six-axis force sensors : a comparative study

A comparative study of three six-axis force sensors selected after an extensive literature survey is presented. A sensor to measure ground contact force at each foot of a walking machine is recommended. Principles of force sensing are reviewed and characteristics of sensing elements are discussed. Results of simulation of three six-axis force sensors are presented as behavior curves, sensitivity plots and compliance matrices. These simulations use finite element techniques. Condition numbers of compliance matrices are presented as a measure of overall sensor performance. Estimates of manufacturing costs are included as a final selection criterion

Complete Genomes of Symbiotic Cyanobacteria Clarify the Evolution of Vanadium-Nitrogenase.

Plant endosymbiosis with nitrogen-fixing cyanobacteria has independently evolved in diverse plant lineages, offering a unique window to study the evolution and genetics of plant-microbe interaction. However, very few complete genomes exist for plant cyanobionts, and therefore little is known about their genomic and functional diversity. Here, we present four complete genomes of cyanobacteria isolated from bryophytes. Nanopore long-read sequencing allowed us to obtain circular contigs for all the main chromosomes and most of the plasmids. We found that despite having a low 16S rRNA sequence divergence, the four isolates exhibit considerable genome reorganizations and variation in gene content. Furthermore, three of the four isolates possess genes encoding vanadium (V)-nitrogenase (vnf), which is uncommon among diazotrophs and has not been previously reported in plant cyanobionts. In two cases, the vnf genes were found on plasmids, implying possible plasmid-mediated horizontal gene transfers. Comparative genomic analysis of vnf-containing cyanobacteria further identified a conserved gene cluster. Many genes in this cluster have not been functionally characterized and would be promising candidates for future studies to elucidate V-nitrogenase function and regulation

Reversible Motion In a Contact Line

When a body of liquid sits on a surface, an irregular border between the wet and dry regions of the surface exists, called the contact line. Driving this contact line back and forth repeatedly can change its shape.We use a syringe pump to cyclically infuse and withdraw a predetermined volume of water, and take photos of the contact line after each cycle. Comparing these images to each other determines if the contact line is returning to the same shape. We find that below a critical value of infused volume, after many cycles the contact line reaches a steady state in which it always returns to the same shape. Above that value the shape fluctuates in the steady state. This suggests a transition similar to that seen in other systems like particle suspensions and solids

Hysteroscopic findings and intrauterine pathology treatment in Mexican infertile women

Background: Hysteroscopy is a minimally invasive approach in gynecologic surgery and one of the main procedures performed on women undergoing fertility treatments. Intrauterine pathology negatively affects fertility by decreasing endometrial receptivity and embryo implantation success, and its prevalence has been reported between 19% and 62%. The aim of our study was to describe the hysteroscopic findings, prevalence of intrauterine pathology, the instruments used for the treatment of structural lesions in Mexican infertile women; and to compare the relationship of positive findings with the type of infertility. Methods: This was a descriptive, cross-sectional study conducted at fertility clinic at a private hospital. Results: We evaluated 191 hysteroscopies; the mean age of women was 35.5+3.2 years and the mean time of infertility 5.7+3.2 years. Primary infertility was the most prevalent (79.1%). In 118 cases (61.8%), uterine cavity abnormalities were diagnosed, the most frequent findings were: polyps (n=51, 26.7%), endometritis (n=30, 15.7%), fibroids (n=15, 7.6 %), synechiae (n=12, 6.5%), and müllerian anomalies (n=10, 5.3%). For structural pathology treatment, cold scissors and bipolar energy were used in 65.5% and 34.5%, respectively. Conclusions: Overall intrauterine pathology prevalence in our study population was 61.8%. Cold scissors and bipolar energy were used for structural lesions treatment. When comparing the relationship of hysteroscopic findings, no statistically significant difference was found in the presence of positive findings, with the type of infertility.