Browsing by Autor "Luis Rivera"

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Car pooling optimization: A case study in Strasbourg (France)
(2008) Miguel A. Vargas; Jorge A. Sefair; Jose L. Walteros; Andrés L. Medaglia; Luis Rivera
Most of the cities around the world face mobility challenges, reflected in the ever increasing commuting times, and causing a dramatic environmental impact. At the same time, environmentally friendly individuals have become aware of the role they play in this problem and they are looking for new transportation alternatives. This is the case of a group of faculty in Strasbourg (France) who commute a significant distance from their home to their workplace and have found in car pooling a solution for their mobility problem. However, car pooling does not come for free. This group of commuters needs to come up with a timetable every two weeks, specifying the faculty who drive, the passengers in each car, the departing and returning time, taking into account multiple departing points and workplaces, and also, guaranteeing that each vehicle carries a prepaid toll card. After modeling the system as a network, two integer linear optimization models are proposed. The first one determines the best vehicle timetable, while the second model finds an efficient way in which the toll cards must be transferred.
Primera evaluación de la abundancia de tarucas Hippocamelus antisensis (Artiodactyla: Cervidae) en Santa Ana y Caspalá, Provincia de Jujuy, Argentina
(Fundación Miguel Lillo, 2024) Constanza G. Vivanco; Ana Sofía Alcalde; Mauro Ogara; Cesar Bracamonte; José Segovia; Juan Manuel Nadalino Rioja; David Sarapura; Luis Biancucci; Natalia Politi; Luis Rivera
En Argentina, la taruca, Hippocamelus antisensis, se distribuye en las provincias de Jujuy, Salta, Tucumán, Catamarca y La Rioja. Habita pastizales y estepas de altura entre 2.000 - 5.000 m de altura y esta categorizada a nivel global como Vulnerable y En peligro en Argentina, habiendo sido declarada Monumento Natural Nacional y Provincial en Jujuy. Aún son escasos los trabajos que evalúen las abundancias de tarucas fuera de áreas protegidas. Los objetivos de este trabajo fueron: estimar la abundancia de tarucas en inmediaciones de las localidades de Santa Ana y Caspalá, provincia de Jujuy, en base a registros directos e indirectos, caracterizar los grupos y el uso de hábitat y la distancia de los registros de tarucas a caminos y puestos. Entre abril y diciembre del año 2021 se realizaron 29 transectas de longitud variable que totalizaron 88.2 km recorridos. Se obtuvieron 13 registros directos y 56 registros indirectos y de estos últimos 13 (23.2%) fueron de huellas, 42 (75%) de heces y 1 (1.8%) de restos óseos. La abundancia relativa total de registros indirectos fue de 0.63 registros/km y de registros directos de 0.82 individuos/km y se registraron 13 individuos jóvenes. Los grupos de tarucas registrados fueron de 5.5 ± 5.4 (rango 1-16) individuos y 88 % de los registros ocurrieron en pastizal bajo y 12 % en roquedales. El área estudiada parece sustentar una población importante de tarucas con grupos de hasta 15-16 individuos y la presencia de individuos jóvenes sugiere que se trata de una población reproductiva.
SARS-CoV-2 sero-surveillance after the first and second waves of the epidemic in Panama
(2025) Carlos Lezcano-Coba; Josefrancisco Galué; Charles Whittaker; Cathal Mills; Rodrigo de Antonio; Xavier Saenz-llorens; Luis Rivera; Xacdiel Rodríguez; Danilo Franco; Arturo Rebollón
Abstract Introduction In the context of the ongoing global SARS-CoV-2 pandemic and potential future viral epidemics, seroepidemiological studies are essential for understanding epidemic dynamics. Panama, a country with a strategic geographic position that serves as a regional hub for international travel and commerce. As such, understanding local transmission patterns is critical for developing evidence based on interventions that can effectively anticipate and mitigate emerging viral threats. Methodology We conducted a population-based cross-sectional study in the provinces of Panamá and Panamá Oeste, targeting the 10 townships with the highest cumulative COVID-19 incidence. A multi-stage cluster sampling strategy was employed using the 2010 National Housing Framework. The first survey was conducted from November 30 to December 4, 2020. A follow-up survey was carried out from June 14 to July 10, 2021, to assess seroconversion and seroreversion. Serum samples were analyzed using two electrochemiluminescence immunoassays (Cobas and Vitros) to detect SARS-CoV-2-specific IgG, IgM, and IgA. We estimated the effective reproduction number (Rt) and fitted modified Poisson regression models to identify risk factors associated with seropositivity. Results A total of 2198 participants were recruited in the first round, and 547 were successfully followed up in the second round. SARS-CoV-2 seroprevalence increased from 24.7% (95% CI: 23.0–27.0%) in the first round to 66.2% (95% CI: 62.0 - 70.0%) in the second. The seroconversion rate was 42.9% (95% CI: 38.0 - 47.0%), while seroreversion was rare (0.9%; 95% CI: 0.3 - 2.0%). The most parsimonious multivariable model identified Indigenous ethnicity, contact with a confirmed case, cohabiting with an infected household member, and prior COVID-19 diagnosis as significant risk factors for seropositivity. In contrast, higher education, belonging to other ethnic groups, and consistent mask use at work were protective factors. Conclusions SARS-CoV-2 transmission persisted in Panama despite strict public health interventions. Household transmission, particularly among Indigenous and socioeconomically vulnerable populations, was a major driver of infection. Higher education and adherence to preventive behaviors emerged as protective factors. These findings emphasize the importance of targeted, equity focused strategies to strengthen epidemic control in Panama and comparable settings.
The Near Threatened Tucumán parrot <i>Amazona tucumana</i> in Bolivia: insights for a global assessment
(Cambridge University Press, 2009) Luis Rivera; Raul Rojas Llanos; Natalia Politi; Bennett Hennessey; Enrique H. Bucher
Abstract The Tucumán parrot Amazona tucumana is restricted to the southern Yungas mountains, from south-eastern Bolivia to north-western Argentina, and has undergone intense capture for the pet trade. We provide updated information on the status of the Bolivian population of the species and past capture levels for the international pet trade. We surveyed 18 sites during the non-breeding season in 2006 and 2007 and recorded a total of 1,643 individuals. In the 1980s 5,400 Tucumán parrots were captured for the international pet trade before the species was listed on CITES Appendix I. Capture of the Tucumán parrot for local trade appears to continue but at a reduced scale. Available evidence from this study and from Argentina indicates a need to change the categorization of the species on the IUCN Red List from Near Threatened to Vulnerable.