The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about development issues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry the names of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely those of the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank and its affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent.

Many cities in the developing world are reforming transit by formalizing bus services to capture user and nonuser benefits. A forerunner in transit reform, the city of Bogotá, Colombia, first implemented the TransMilenio bus rapid transit (BRT) system and then more recently undertook a large-scale initiative to formalize and regulate traditional urban buses in the city. This integrated public transport system [Sistema Integrado de Transporte Público (SITP)] is transforming Bogotá’s traditional urban bus system into a regulated, concessionary system with restructured bus routes that integrates operations, fares, and infrastructure with the TransMilenio BRT. An investigation was conducted to determine whether the SITP has increased affordability and employment accessibility for public transit users in Bogotá. Results revealed that most accessibility improvements resulted from the recent expansion (and significantly higher speeds) of TransMilenio rather than the SITP. Results of an analysis conducted with budget constraints to determine affordable accessibility indicated that employment accessibility was reduced overall; however, the new integrated fare increased accessibility over traditional buses, especially on the periphery and in southern areas of the city, as a result of reduced transfer costs. Overall, results partly explain the lack of enthusiasm for the bus reform process on the part of public transit users and the political discomfort that becomes apparent when embarking on this process in developing-world cities. Also, more incremental, flexible reform might be crafted for public transportation systems that are dominated by informal services.

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The misuse of antibiotics in the cattle sector can lead to milk contamination, with concomitant effects on the dairy industry and human health. Biosensors can be applied in this field; however, the influence of the milk matrix on their activity has been poorly studied in light of the preanalytical process. Herein, aptamer-conjugated gold nanoparticles (nanoaptasensors) were investigated for the colorimetric detection in raw milk of four antibiotics used in cattle. The effect of milk components on the colorimetric response of the nanoaptasensors was analyzed by following the selective aggregation of the nanoparticles, using the absorption ratio A520/A720. A preanalytical strategy was developed to apply the nanoaptasensors to antibiotic-contaminated raw milk samples, which involves a clarification step with Carrez reagents followed by the removal of cations through dilution, chelation (EDTA) or precipitation (NaHCO3). The colorimetric signals were detected in spiked samples at concentrations of antibiotics as low as 0.25-fold the maximum residue limits (MRLs) for kanamycin (37.5 μg/L), oxytetracycline (25 μg/L), sulfadimethoxine (6.25 μg/L) and ampicillin (1 μg/L), according to European and Chilean legislation. Overall, we conclude that this methodology holds potential for the semiquantitative analysis of antibiotic residues in raw milk obtained directly from dairy farms.

Mundo Atómico fue una revista editada entre 1950 y 1955 durante la presidencia de Juan Domingo Perón. Se propuso crear un vínculo entre la ciencia y el pueblo con la idea de que el acceso al conocimiento CyT y la política científica del país no quedarán solamente en manos de los especialistas, sino que fueran abiertas al resto de la sociedad. Ciencia e Investigación es una revista publicada por la Asociación Argentina para el Progreso de las Ciencias desde 1946. Se propone despertar el interés por la ciencia y estimular el desarrollo de la investigación científica basada en la libertad de investigación. Ambas revistas se proponían la divulgación científica, pero con miradas y perspectivas muy diferentes. En este artículo se analizan y comparan las características de ambas revistas como reflejo de dos enfoques del desarrollo científico tecnológico nacional, que más allá del contexto histórico en que se manifestaron, conserva vigencia en la actualidad.