Conflict Dynamics in Scale-Free Networks with Degree Correlations and Hierarchical Structure

We present a study of the dynamic interactions between actors located on complex networks with scale-free and hierarchical scale-free topologies with assortative mixing, that is, correlations between the degree distributions of the actors. The actor’s state evolves according to a model that considers its previous state, the inertia to change, and the influence of its neighborhood. We show that the time evolution of the system depends on the percentage of cooperative or competitiveinteractions. For scale-free networks, we find that the dispersion between actors is higher when all interactions are either cooperative or competitive, while a balanced presence of interactions leads to a lower separation. Moreover, positive assortative mixing leads to greater divergence between the states, while negative assortative mixing reduces this dispersion. We also find that hierarchical scale-free networks have both similarities and differences when compared with scale-free networks. Hierarchical scale-free networks, like scale-free networks, show the least divergence for an equal mix of cooperative and competitive interactions between actors. On the other hand, hierarchical scale-free networks, unlike scale-free networks, show much greater divergence when dominated by cooperative rather than competitive actors, and while the formation of a rich club (adding links between hubs) with cooperative interactions leads to greater divergence, the divergence is much less when they are fully competitive. Our findings highlight the importance of the topology where the interaction dynamics take place, and the fact that a balanced presence of cooperators and competitors makes the system more cohesive, compared to the case where one strategy dominates

Tapping into the environmental co-benefits of improved tropical forages for an agroecological transformation of livestock production systems

Livestock are critical for incomes, livelihoods, nutrition and ecosystems management throughout the global South. Livestock production and the consumption of livestock-based foods such as meat, cheese, and milk is, however, under global scrutiny for its contribution to global warming, deforestation, biodiversity loss, water use, pollution, and land/soil degradation. This paper argues that, although the environmental footprint of livestock production presents a real threat to planetary sustainability, also in the global south, this is highly contextual. Under certain context-specific management regimes livestock can deliver multiple benefits for people and planet. We provide evidence that a move toward sustainable intensification of livestock production is possible and could mitigate negative environmental impacts and even provide critical ecosystem services, such as improved soil health, carbon sequestration, and enhanced biodiversity on farms. The use of cultivated forages, many improved through selection or breeding and including grasses, legumes and trees, in integrated crop-tree-livestock systems is proposed as a stepping stone toward agroecological transformation. We introduce cultivated forages, explain their multi-functionality and provide an overview of where and to what extent the forages have been applied and how this has benefited people and the planet alike. We then examine their potential to contribute to the 13 principles of agroecology and find that integrating cultivated forages in mixed crop-tree-livestock systems follows a wide range of agroecological principles and increases the sustainability of livestock production across the globe. More research is, however, needed at the food system scale to fully understand the role of forages in the sociological and process aspects of agroecology. We make the case for further genetic improvement of cultivated forages and strong multi-disciplinary systems research to strengthen our understanding of the multidimensional impacts of forages and for managing agro-environmental trade-offs. We finish with a call for action, for the agroecological and livestock research and development communities to improve communication and join hands for a sustainable agri-food system transformation

Levantamiento del velo corporativo. Panorama y perspectivas. El caso colombiano

Son múltiples y constantes los debates que se han dado en la comunidad jurídica nacional sobre permitir que los socios o accionistas de una sociedad respondan directamente con su patrimonio por las acreencias de la persona jurídica a través de la utilización de la "teoría del levantamiento del velo corporativo". Dada la importancia de este tema, expertos colombianos de primer nivel se reúnen en esta obra para exponer sus puntos de vista sobre la aplicación de esta institución en Colombia. Adicionalmente, este libro incluye el informe de ejecución del proyecto de investigación , adelantado por la línea de investigación en Derecho Comercial del Grupo de Derecho Privado de la Facultad de Jurisprudencia, el cual fue financiado por el Centro de Investigaciones, Estudios y Consultoría (CIEC) de la Universidad del Rosario.Dada la importancia de este tema, expertos colombianos de primer nivel se reúnen en esta obra para exponer sus puntos de vista sobre la aplicación de esta institución en Colombia

Conflict Dynamics in Scale-Free Networks with Degree Correlations and Hierarchical Structure

We present a study of the dynamic interactions between actors located on complex networks with scale-free and hierarchical scale-free topologies with assortative mixing, that is, correlations between the degree distributions of the actors. The actor’s state evolves according to a model that considers its previous state, the inertia to change, and the influence of its neighborhood. We show that the time evolution of the system depends on the percentage of cooperative or competitive interactions. For scale-free networks, we find that the dispersion between actors is higher when all interactions are either cooperative or competitive, while a balanced presence of interactions leads to a lower separation. Moreover, positive assortative mixing leads to greater divergence between the states, while negative assortative mixing reduces this dispersion. We also find that hierarchical scale-free networks have both similarities and differences when compared with scale-free networks. Hierarchical scale-free networks, like scale-free networks, show the least divergence for an equal mix of cooperative and competitive interactions between actors. On the other hand, hierarchical scale-free networks, unlike scale-free networks, show much greater divergence when dominated by cooperative rather than competitive actors, and while the formation of a rich club (adding links between hubs) with cooperative interactions leads to greater divergence, the divergence is much less when they are fully competitive. Our findings highlight the importance of the topology where the interaction dynamics take place, and the fact that a balanced presence of cooperators and competitors makes the system more cohesive, compared to the case where one strategy dominates

Intensive short-duration rotational grazing is associated with improved soil quality within one year after establishment in Colombia

Large-scale conversion of natural ecosystems to grazed grasslands and subsequent soil degradation due to overgrazing and inadequate pasture management in tropical agroecosystems urgently call for sustainable intensification of grazing systems, i.e. increasing animal productivity while maintaining or improving soil quality and ecosystem services. We investigated the impact of intensive short-duration rotational grazing (IRG) management on soil properties in two study sites in Colombian Eastern Plains. In each site, one farm with stocking rates as high as 4.2 livestock units (LU) ha−1 managed by IRG was compared with an adjacent traditionally managed (reference) farm with low animal stocking rate (1 LU ha−1), where cattle grazing was either continuous (Morichal site), or rotational with long grazing period and short periods of pasture recovery (Villasol site). As early as nine months after the adoption of IRG management, both farms managed by IRG had lower bulk density and higher water retention capacity than their respective reference farms, despite the more than four-times higher stocking rates. The animal feed supplement at the IRG farm at Morichal likely contributed to higher soil organic carbon stocks and improved soil aggregation when compared to the reference farm and to the Villasol site, where no supplement was applied. The improvement of soil properties found in IRG farms, compared to reference farms, was associated with a higher macrofauna abundance, particularly that of earthworms and beetles, which play a crucial role in soil structure improvement through bioturbation. Our results demonstrate the capacity of IRG management to intensify cattle production per unit area, while simultaneously improving soil properties and increasing soil macrofauna biodiversity as early as nine months since the implementation of IRG management

Gross N transformation rates in soil system with contrasting Urochloa genotypes do not confirm the relevance of BNI as previously assessed in-vitro

The capacity of several plant species or landraces to inhibit nitrification in soil (biological nitrification inhibition, BNI) has been assessed in certain tropical pastures. These assessments are commonly based on potential net nitrification rates, which do not differentiate between gross nitrification and other processes that may reduce the amount of nitrate in soil. In a greenhouse experiment using two genotypes of Urochloa humidicola with contrasting BNI capacity in vitro, we evaluated gross N transformation rates before and after (7 and 21 days) N fertilization, while periodically measuring N2O emissions. Gross nitrification rates (in fact gross nitrate production assessed by pool dilution technique) were comparable in both genotypes and were low in comparison to strong microbial NH4+ immobilization. The N2O emissions were higher in pots with low-BNI plants. The discrepancy between the potential net nitrification rates assessed in laboratory assays (higher in low-BNI plants) and gross nitrification in pot or field experiments (no differences between genotypes) can be attributed to the out-competition of ammonia oxidizers by plant N uptake and ammonia immobilizing heterotrophic microbes, resulting in low nitrification under conditions where growing plants are present. This study confirmed the capacity of certain U. humidicola genotypes to reduce N2O emissions but warrants further investigation of the underlying mechanisms. It also questions the relevance of BNI in the rhizosphere of this plant species as other mechanisms (rather than the inhibition of gross nitrification) seem to be more important in maintaining low-nitrate soil environments in soil–plant systems of U. humidicola

Optimizing nitrogen use efficiency of six forage grasses to reduce nitrogen loss from intensification of tropical pastures

We aimed to evaluate the effect of different types and rates of nitrogen (N) fertilizers on plant biomass production, nitrogen use efficiency (NUE), and nitrous oxide (N2O) emissions of six tropical forage grass cultivars. This field study was conducted in Colombia under tropical conditions in two phases. Phase 1: we evaluated the effect of different types of N fertilizers (urea; calcium ammonium nitrate (CAN); and urea-ammonium sulfate (U-AS) using a single dose of application of 25 kg N ha−1 cut−1, along with a control treatment for each grass without application of fertilizer) on forage dry matter, crude protein, N uptake, N surplus, and NUE. The study focused on six tropical forage grass cultivars: Urochloa humidicola cv. Tully, U. hybrid cv. Cobra, U. hybrid cv. Cayman, Megathyrsus maximus cv. Mombasa, Cynodon nlemfuensis cv. Stargrass and U. decumbens cv. Basilisk. We found that the biomass production and protein content of each forage grass cultivar responded differently to different N fertilizer types. In consequence, the NUE of each forage grass cultivar was strongly affected by the type of N fertilizer applied. For example, Cayman showed a NUE of 87.8% with CAN and 40.4% with urea, while the NUE of Basilisk with CAN was 8.0% and 76.4% with urea. Maximum NUE values were obtained for Stargrass and Cayman with CAN (91.7 and 87.8%, respectively) and for Mombasa with urea (89.9%). Phase 2: we selected three combinations of forage grass cultivars and type of N fertilizer, and we evaluated the impact of four rates of N application (0, 10, 20, and 30 kg N ha−1 cut−1) on forage production and N2O emissions upon fertilization. In general, higher N fertilization rates increased the accumulated N2O emissions. However, we observed that the fertilization of Stargrass and Cayman grass with a rate of 20 kg N−1 cut−1 and Mombasa grass with a rate of 30 kg N−1 cut−1 were more beneficial than the other rates of N fertilization based on the biomass production and amount of N2O emitted are considered. This study highlights the importance of optimizing NUE in tropical pasture systems using an appropriate design of N fertilization strategy. Inappropriate N fertilizer use can significantly increase the N losses (e.g., through N2O emissions, with a potential contribution from N leaching). These findings provide valuable information for sustainable intensification of productive tropical livestock systems to spare land for other uses.ISSN:0167-8809ISSN:1873-230

Prognostic factors of progressive fibrotic hypersensitivity pneumonitis: a large, retrospective, multicentre, observational cohort study

Background Fibrotic hypersensitivity pneumonitis ( fHP) is an immune-mediated interstitial lung disease caused by sensitisation to chronic allergen inhalation. This study aimed to determine prognostic indicators of progression and mortality in fHP. Methods This was a retrospective, multicentre, observational, cross-sectional cohort study of consecutive patients diagnosed with fHP from 1 January 2012 to 31 December 2021. Multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% confidence intervals for predictors of progression and survival. Results A total of 403 patients were diagnosed with fHP: median (interquartile range) age 66.5 (14.0) years, 51.9% females and 55.1% never-smokers. The cause of fHP was mainly fungal (39.7%) or avian (41.4%). Lung biopsy was performed in 269 cases (66.7%). In the whole cohort the variables that were related to mortality or lung transplant were older age (HR 1.08; p<0.001), percentage predicted forced vital capacity (HR 0.96; p=0.001), lymphocytosis in bronchoalveolar lavage (BAL) (HR 0.93; p=0.001), presence of acute exacerbation during follow-up (HR 3.04; p=0.001) and GAP (gender, age and lung physiology) index (HR 1.96; p<0.01). In the group of biopsied patients, the presence of fibroblastic foci at biopsy (HR 8.39; p<0.001) stands out in multivariate Cox regression analyses as a highly significant predictor for increased mortality or lung transplant. GAP index (HR 1.26; p=0.009), lymphocytosis in BAL (HR 0.97; p=0.018) and age (HR 1.03; p=0.018) are also predictors of progression. Conclusions The study identified several prognostic factors for progression and/or survival in fHP. The presence of fibroblastic foci at biopsy was a consistent predictor for increased mortality and the presence of lymphocytosis in BAL was inversely related to mortality