The disruption index is biased by citation inflation

A recent analysis of scientific publication and patent citation networks by Park et al. (Nature, 2023) suggests that publications and patents are becoming less disruptive over time. Here we show that the reported decrease in disruptiveness is an artifact of systematic shifts in the structure of citation networks unrelated to innovation system capacity. Instead, the decline is attributable to 'citation inflation', an unavoidable characteristic of real citation networks that manifests as a systematic time-dependent bias and renders cross-temporal analysis challenging. One driver of citation inflation is the ever-increasing lengths of reference lists over time, which in turn increases the density of links in citation networks, and causes the disruption index to converge to 0. A second driver is attributable to shifts in the construction of reference lists, which is increasingly impacted by self-citations that increase in the rate of triadic closure in citation networks, and thus confounds efforts to measure disruption, which is itself a measure of triadic closure. Combined, these two systematic shifts render the disruption index temporally biased, and unsuitable for cross-temporal analysis. The impact of this systematic bias further stymies efforts to correlate disruption to other measures that are also time-dependent, such as team size and citation counts. In order to demonstrate this fundamental measurement problem, we present three complementary lines of critique (deductive, empirical and computational modeling), and also make available an ensemble of synthetic citation networks that can be used to test alternative citation-based indices for systematic bias.Comment: 10 pages, 6 figure

Adaptación de las cepas de Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans y Leptospirillum ferrooxidans en el concentrado de esfalerita de residuos mineros

One of the main characteristics of the microorganisms used in the leaching process is their capacity to adapt to aggressive environments, characterized by a notable presence of heavy metals. In this study the adaptation of the strains Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans was evaluated on a sphalerite concentrate from mining waste. In the adaptation tests, the energy source (ferrous sulphate) was gradually replaced by percentages of mineral pulp, ending with subcultures without the addition of an external energy source. The results show that the strains A. ferrooxidans and A. thiooxidans are more resistant to high concentrations of sphalerite, compared to the strain of L. ferrooxidans, since, in the case of this strain, it was necessary to repeat some tests (8% of pulp), since a deficient development was evident. This was associated with factors such as the decrease of the Fe+2 energy source, the increase of the pulp density, the accumulation of toxic metals and secondary products of the dissolution of minerals and the increase of the pH.Una de las principales características de los microorganismos empleados en el proceso de lixiviación, es su capacidad de adaptación a ambientes agresivos, caracterizados por una notable presencia de metales pesados. En  este  estudio  se  evaluó  la  adaptación  de  las  cepas  Acidithiobacillus  ferrooxidans,  Acidithiobacillus  thiooxidans  y  Leptospirillum  ferrooxidans,  sobre  un  concentrado  de  esfalerita,  proveniente  de  residuos  mineros. En los ensayos de adaptación, se suplementó paulatinamente la fuente de energía (sulfato ferroso) cambiándola por porcentajes de pulpa mineral, finalizando con subcultivos sin adición de fuente de energía externa.  Los resultados muestran que las cepas A. ferrooxidans y A. thiooxidans son más resistentes a altas concentraciones de esfalerita, frente a la cepa de L. ferrooxidans, puesto que, en el caso de esta cepa, fue necesario repetir algunos ensayos (8% de pulpa), ya que era evidente un desarrollo deficiente. Lo anterior se asoció con factores como la disminución de la fuente energética Fe+2, el aumento de la densidad de pulpa, la acumulación de metales tóxicos y productos secundarios de la disolución de los minerales y el aumento del pH

Bioenergy transition as a strategic mechanism to diversify energy sources in rural areas in Colombia

Received: February 1st, 2023 ; Accepted: May 27th, 2023 ; Published: October 14th, 2023 ; Correspondence: [email protected], [email protected] growth in population has resulted in an increase in the consumption of goods and services, which has led to a surge in waste generation and the use of fossil fuels. To mitigate the envi-ronmental issues associated with improper waste management and reduce greenhouse gas emissions from fossil fuels, residual organic matter can be used to produce bioenergy in the form of biogas and biomethane through anaerobic digestion (AD). These biofuels can act as substitutes for liquefied petroleum gas (LPG) and natural gas (NG) and can be utilized for power and heat generation. In Colombia, the current production of biogas is 4 MW, and the government aims to increase its utilization by promoting the inclusion of biogas and biomethane in the energy matrix through a supportive regulatory framework. Studies suggest that the theoretical energy potential of livestock waste in Colombia is estimated to be 2,673 MW, but the current technological conditions allow for the utilization of only 198 MW, with the pork sector contributing 34%. This study examines the legal context and the present state of biogas in the Colombian energy matrix, while exploring the potential of the Colombian pig farming sector for biogas production. The social, economic, and environmental barriers and opportunities faced by this sector in becoming an energy producer during the transition period are also identified. The findings suggest that biogas presents a sustainable energy solution for rural areas of Colombia where pig farming is a prominent economic activity. Biogas can replace traditional fuels like LPG and firewood for cooking purposes or serve as a complementary source for electricity and thermal energy production in non-interconnected zones. This could mitigate environmental issues and reduce the prevalence of respiratory diseases associated with the use of firewood

La lenteja de agua (Lemna minor L.): una planta acuática promisoria

Se describen las principales características morfológicas y ecológicas de la planta acuática Lemna minor L., al igual que la utilización que tiene como complemento alimenticio para animales domésticos y en labores de fitorremediación, por su capacidad de absorber nutrientes y contaminantes de los ecosistemas acuáticos. Asimismo se discute su potencial como una especie adecuada para realizar ensayos de fitotoxicidad.The main morphological and ecological characteristics of the aquatic plant Lemna minor L. are described, as well as its use as food complement for domestic animals, and in phytoremediation for its ability to absorb nutrients and pollutants from aquatic ecosystems. Its potential as a species used in phytotoxicity tests is also discussed

Simulacion de operación de celdas de manufactura flexible fmc, utilizando las redes de petri

En este artículo se presenta un procedimiento de simulación en tiempo real para la operación de Celdas de Manufactura Flexible aplicando Redes de Petri; se utiliza el Toolbox “Petrinet” de Matlab, el cual fue desarrollado para este fin y predice el comportamiento funcional de la celda y de cada uno de los equipos que la conforman. El modelo desarrollado, la simulación de la operación y la posterior verificación de resultados fue aplicada sobre una Celda real de mecanizado, existente en el Laboratorio de proyectos de Maestría, en la Facultad de Ingeniería Mecánica de la Universidad Tecnológica de Pereira. La utilización de la red de Petri permitió predecir la estrategia de operación bajo la cual operaría la Celda en mención