Explanatory Note to the Proposal for the Establishment of a Cooperative Programme for Field Bean Research in Latin America and the Caribbean Zone

Personal note by Luis Marcano on the background of the proposed Cooperative Program for Field Bean Research in Latin America, participation of member countries, the selection of IICA as its secretariat, and the presence of strong international, regional, and national institutes that will serve the program. Agenda item presented at TAC Seventh Meeting, February 1974

La dinámica de las relaciones diplomáticas entre Venezuela y los Estados Unidos durante el gobierno del general Isaías Medina Angarita (1941–1945)

This research paper analyzes the relations between the United States of America and Venezuela in times of the democratic government of General Isaías Medina Angarita. We start from the hypothesis that the relations between Venezuela and the United States, based on diplomatic recognition and the consequent political acceptance, were conditioned by economic and political factors derived from the US interest in Venezuelan petroleum and the need to guarantee stability of commercial markets, even during World War II.La presente investigación analiza las relaciones entre los Estados Unidos de América y Venezuela en tiempos del gobierno democrático del general Isaías Medina Angarita. Partimos de la hipótesis que considera que las relaciones entre Venezuela y los Estados Unidos en función del reconocimiento diplomático y de la consecuente aceptación política estuvieron condicionadas por factores de orden económico y político derivado por el interés estadounidense en el petróleo venezolano y por la necesidad de garantizar la estabilidad de los mercados comerciales, inclusive durante la Segunda Guerra Mundial

La sostenibilidad de la política fiscal en el América Latina: El caso de Venezuela

La economía venezolana se ha visto sometida desde mediados de la década de los setenta a un proceso de marcada inestabilidad y volatilidad, causado fundamentalmente por los shocks provenientes del mercado petrolero. La política fiscal ha jugado un rol determinante en la transmisión de esos shocks al resto de la economía. Por una parte, el gasto público ha mostrado un comportamiento procíclico en relación a los ingresos petroleros, transmitiendo la volatilidad de estos últimos a través de la demanda agregada interna y por tanto en las presiones inflacionarias y en el crecimiento económico. Por otra parte, el uso del tipo de cambio como mecanismo de corrección fiscal en algunas oportunidades y en otras como ancla nominal, conjuntamente con el comportamiento procíclico del gasto, han creado una situación prolongada de "stop and go" o de expansiones y ajustes recurrentes y transitorios con elevados costos de crecimiento, inflación y empobrecimiento de la población.

On the queuing delay of time-varying channels in Low Earth Orbit satellite constellations

Low Earth Orbit (LEO) satellite constellations are envisioned as a complementary or integrated part of 5G and future 6G networks for broadband or massive access, given their capabilities of full Earth coverage in inaccessible or very isolated environments. Although the queuing and end-to-end delays of such networks have been analyzed for channels with fixed statistics, currently there is a lack in understanding the effects of more realistic time-varying channels for traffic aggregation across such networks. Therefore, in this work we propose a queuing model for LEO constellation-based networks that captures the inherent variability of realistic satellite channels, where ground-to-satellite/satellite-to-ground links may present extremely poor connection periods due to the Land Mobile Satellite (LMS) channel. We verify the validity of our model with an extensive event-driven simulator framework analysis capturing the characteristics of the considered scenario. We later study the queuing and end-to-end delay distributions under such channels with various link, traffic, packet and background conditions, while observing good match between theory and simulation. Our results show that ground-to-satellite/satellite-to-ground links and background traffic have a much stronger impact over the end-to-end delay in mean and particularly variance, even with moderate queues, than unobstructed inter-satellite connections in outer space on an established path between two ground stations and through the constellation. This might hinder the usability of these networks for services with stringent time requirements.This work was supported in part by the European Union’s Horizon 2020 Research and Innovation Programme under Grant 861111, in part by the Innovation Fund Denmark Project Drones4Energy under Project J.nr.8057-00038A, and in part by the Spanish Government through the Ministerio de Economía y Competitividad, Fondo Europeo de Desarrollo Regional (MINECO-FEDER) by the Project Future Internet Enabled Resilient smart CitiEs (FIERCE) under Grant RTI2018-093475-AI00

Finite buffer queuing delay performance in the low earth orbit land mobile satellite channel

Low Earth Orbit (LEO) satellite constellations have been identified for new massive access networks, as a complement to traditional cellular ones, due to their native ubiquity. Despite being a feasible alternative, such networks still raise questions on their performance, in particular regarding the delay and queuing management under realistic channels. In this work, we study the queuing delay of a single satellite-to-ground link, considering a Land Mobile Satellite (LMS) channel in LEO with finite buffer lengths. We analyze the trade-off between delay and packet loss probability, using a novel model based on Markov chains, which we assess and extend with an extensive analysis carried out by means of system level simulation. The developed tools capture with accuracy the queuing delay statistical behavior in the S and Ka frequency bands, where LEO communications are planned to be deployed. Our results show that we can use short buffers to ensure less than 5-10% packet loss, with tolerable delays in such bands.This project was funded by the EU Horizon 2020 re search and innovation program, Drones4Safety-agreement No 861111, the Innovation Fund Denmark project Drones4Energy with project J. nr. 8057-00038A and by the Spanish Government (Ministerio de Economía y Competitividad, Fondo Europeo de Desarrollo Regional, MINECO-FEDER) by means of the project FIERCE: Future Internet Enabled Resilient Smart CitiEs (RTI2018-093475-AI00)

Sustratos orgánicos para la producción de plántulas de tomate en vivero

El empleo de sustratos orgánicos proporciona condiciones adecuadas para maximizar la expresión del vigor de las semillas de tomate y por consiguiente la obtención de plántulas más vigorosas en la etapa de crecimiento inicial. El objetivo de este estudio fue evaluar diferentes sustratos orgánicos para la producción de plántulas de tomate cultivado en vivero. Los tratamientos fueron: (T1) 50% tierra + 25% estiércol + 25% cascarilla de arroz (Testigo), (T2) Vermicompost 40% + arena 50% + bocashi 10%, (T3) Vermicompost 35% + arena 50% + bocashi 15%, (T4) Vermicompost 30% + arena 50% + bocashi 20%, (T5) Vermicompost 25% + arena 50% + bocashi 25%, (T6) Vermicompost 50% + arena 50%, (T7) Turba 100 %. Se evaluó: número de hojas, germinación, diámetro de tallo, peso húmedo de tallo, altura de planta, longitud de raíz y peso húmedo de raíz. El diseño experimental fue completamente al azar con 9 repeticiones. El tratamiento T3, mostró el mejor desarrollo de plántula en todas las variables evaluadas. El sustrato orgánico compuesto por 35% de vermicompost + 50% de arena + 15% de bocashi, mostró el mejor desempeño