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"Martínez, Alejandro"
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Effects of Amazon basin deforestation on regional atmospheric circulation and water vapor transport towards tropical South America
The water cycle over the Amazon basin is a regulatory mechanism for regional and global climate. The atmospheric moisture evaporated from this basin represents an important source of humidity for itself and for other remote regions. The deforestation rates that this basin has experienced in the past decades have implications for regional atmospheric circulation and water vapor transport. In this study, we analyzed the changes in atmospheric moisture transport towards tropical South America during the period 1961–2010, according to two deforestation scenarios of the Amazon defined by Alves et al. (Theor Appl Climatol 100(3-4):337–350, 2017). These scenarios consider deforested areas of approximately 28% and 38% of the Amazon basin, respectively. The Dynamic Recycling Model is used to track the transport of water vapor from different sources in tropical South America and the surrounding oceans. Our results indicate that under deforestation scenarios in the Amazon basin, continental sources reduce their contributions to northern South America at an annual scale by an average of between 40 and 43% with respect to the baseline state. Our analyses suggest that these changes may be related to alterations in the regional Hadley and Walker cells. Amazon deforestation also induces a strengthening of the cross-equatorial flow that transports atmospheric moisture from the Tropical North Atlantic and the Caribbean Sea to tropical South America during the austral summer. A weakening of the cross-equatorial flow is observed during the boreal summer, reducing moisture transport from the Amazon to latitudes further north. These changes alter the patterns of precipitable water contributions to tropical South America from both continental and oceanic sources. Finally, we observed that deforestation over the Amazon basin increases the frequency of occurrence of longer dry seasons in the central-southern Amazon (by between 29 and 57%), depending on the deforestation scenario considered, as previous studies suggest.
Journal Article
On the effectiveness of communication strategies as non-pharmaceutical interventions to tackle epidemics
When pharmaceutical interventions are unavailable to deal with an epidemic outbreak, adequate management of communication strategies can be key to reduce the contagion risks. On the one hand, accessibility to trustworthy and timely information, whilst on the other, the adoption of preventive behaviors may be both crucial. However, despite the abundance of communication strategies, their effectiveness has been scarcely evaluated or merely circumscribed to the scrutiny of public affairs. To study the influence of communication strategies on the spreading dynamics of an infectious disease, we implemented a susceptible-exposed-infected-removed-dead (SEIRD) epidemiological model, using an agent-based approach. Agents in our systems can obtain information modulating their behavior from two sources: (i) through the local interaction with other neighboring agents and, (ii) from a central entity delivering information with a certain periodicity. In doing so, we highlight how global information delivered from a central entity can reduce the impact of an infectious disease and how informing even a small fraction of the population has a remarkable impact, when compared to not informing the population at all. Moreover, having a scheme of delivering daily messages makes a stark difference on the reduction of cases, compared to the other evaluated strategies, denoting that daily delivery of information produces the largest decrease in the number of cases. Furthermore, when the information spreading relies only on local interactions between agents, and no central entity takes actions along the dynamics, then the epidemic spreading is virtually independent of the initial amount of informed agents. On top of that, we found that local communication plays an important role in an intermediate regime where information coming from a central entity is scarce. As a whole, our results highlight the importance of proper communication strategies, both accurate and daily, to tackle epidemic outbreaks.
Journal Article
Sarcopenia: Molecular Pathways and Potential Targets for Intervention
This study was supported by ISABIAL (grant number 190290) and the Official Funding Agency for Biomedical Research of the Spanish Government, Institute of Health Carlos III (ISCIII) through CIBEROBN (CB12/03/30038), which is co-funded by the European Regional Development Fund.
Journal Article
Moisture sources to the 2010–2012 anomalous wet season in northern South America
During 2010–2012, northern South America experienced one of the strongest wet seasons during the recent decades, with socio-economic implications of wide proportions. This period was characterized by two stronger-than-average La Niña events, one occurred in 2010–2011 and another less intense event in 2011–2012. This study focused on identifying the main moisture sources, besides the eastern Pacific, for the anomalous wet season occurred in this region during 2010–2012, and their association with the La Niña events observed in the equatorial Pacific. The results discussed here suggest that the main moisture sources to this anomalous wet season were the Pacific Ocean (via the westerly flow of the Choco jet) and the Caribbean Sea (via the weakening of the Caribbean low-level jet and the development of southward anomalies toward northern South America). Such changes appear to be associated not only to El Niño-Southern Oscillation (ENSO)-driven sea surface temperature anomalies in the eastern Pacific, Caribbean Sea, and north Atlantic, but also to ENSO-independent variability in the Atlantic Ocean. The latter is related to an enhanced Atlantic Meridional Mode.
Journal Article
Bioelectric stimulation controls tissue shape and size
Epithelial tissues sheath organs and electro-mechanically regulate ion and water transport to regulate development, homeostasis, and hydrostatic organ pressure. Here, we demonstrate how external electrical stimulation allows us to control these processes in living tissues. Specifically, we electrically stimulate hollow, 3D kidneyoids and gut organoids and find that physiological-strength electrical stimulation of ∼ 5 - 10 V/cm powerfully inflates hollow tissues; a process we call electro-inflation. Electro-inflation is mediated by increased ion flux through ion channels/transporters and triggers subsequent osmotic water flow into the lumen, generating hydrostatic pressure that competes against cytoskeletal tension. Our computational studies suggest that electro-inflation is strongly driven by field-induced ion crowding on the outer surface of the tissue. Electrically stimulated tissues also break symmetry in 3D resulting from electrotaxis and affecting tissue shape. The ability of electrical cues to regulate tissue size and shape emphasizes the role and importance of the electrical micro-environment for living tissues.
Electrical stimulation of hollow, 3D kidney tissues causes these tissues to inflate and change shape. The authors call this process electro-inflation and connect it to electricity driving ions into the center of the tissues, causing water to follow by osmosis.
Journal Article
Quasiperiodic granular chains and Hofstadter butterflies
We study quasiperiodicity-induced localization of waves in strongly precompressed granular chains. We propose three different set-ups, inspired by the Aubry-André (AA) model, of quasiperiodic chains; and we use these models to compare the effects of on-site and off-site quasiperiodicity in nonlinear lattices. When there is purely on-site quasiperiodicity, which we implement in two different ways, we show for a chain of spherical particles that there is a localization transition (as in the original AA model). However, we observe no localization transition in a chain of cylindrical particles in which we incorporate quasiperiodicity in the distribution of contact angles between adjacent cylinders by making the angle periodicity incommensurate with that of the chain. For each of our three models, we compute the Hofstadter spectrum and the associated Minkowski-Bouligand fractal dimension, and we demonstrate that the fractal dimension decreases as one approaches the localization transition (when it exists). We also show, using the chain of cylinders as an example, how to recover the Hofstadter spectrum from the system dynamics. Finally, in a suite of numerical computations, we demonstrate localization and also that there exist regimes of ballistic, superdiffusive, diffusive and subdiffusive transport. Our models provide a flexible set of systems to study quasiperiodicity-induced analogues of Anderson phenomena in granular chains that one can tune controllably from weakly to strongly nonlinear regimes.
This article is part of the theme issue 'Nonlinear energy transfer in dynamical and acoustical systems'.
Journal Article
Morphodynamics of surface-attached active drops
Many biological and synthetic systems are suspensions of oriented actively-moving components. Unlike in passive suspensions, the interplay between orientational order, active flows, and interactions with boundaries gives rise to fascinating new phenomena in such active suspensions. Here, we examine the paradigmatic example of a surface-attached drop of an active fluid (an “active drop”), which has so far only been studied in the idealized limit of thin drops. We find that such surface-attached active drops can exhibit a wide array of stable steady-state shapes and internal flows that are far richer than those documented previously, depending on boundary conditions and the strength of active stresses. Our analysis uncovers quantitative principles to predict and even rationally control the conditions under which these different states arise—yielding design principles for next-generation active materials.
Active matter systems, which include biological and synthetic components that consume energy to generate motion, exhibit complex behaviors influenced by their interactions with boundaries. This study reveals that surface-attached active drops can adopt a diverse range of stable shapes and internal flows, significantly expanding our understanding of their morphodynamics and providing insights for the design of advanced active materials.
Journal Article
Psychological Stress Phenocopies Brain Mitochondrial Dysfunction and Motor Deficits as Observed in a Parkinsonian Rat Model
Psychological distress is a public health issue as it contributes to the development of human diseases including neuropathologies. Parkinson’s disease (PD), a chronic, progressive neurodegenerative disorder, is caused by multiple factors including aging, mitochondrial dysfunction, and/or stressors. In PD, a substantial loss of substantia nigra (SN) neurons leads to rigid tremors, bradykinesia, and chronic fatigue. Several studies have reported that the hypothalamic-pituitary-adrenal (HPA) axis is altered in PD patients, leading to an increase level of cortisol which contributes to neurodegeneration and oxidative stress. We hypothesized that chronic psychological distress induces PD-like symptoms and promotes neurodegeneration in wild-type (WT) rats and exacerbates PD pathology in PINK1 knockout (KO) rats, a well-validated animal model of PD. We measured the bioenergetics profile (oxidative phosphorylation and glycolysis) in the brain by employing an XF24e Seahorse Extracellular Flux Analyzer in young rats subjected to predator-induced psychological distress. In addition, we analyzed anxiety-like behavior, motor function, expression of antioxidant enzymes, mitochondrial content, and neurotrophic factors brain-derived neurotrophic factor (BDNF) in the brain. Overall, we observed that psychological distress diminished up to 50% of mitochondrial respiration and glycolysis in the prefrontal cortex (PFC) derived from both WT and PINK1-KO rats. Mechanistically, the level of antioxidant proteins, mitochondrial content, and BDNF was significantly altered. Finally, psychological distress robustly induced anxiety and Parkinsonian symptoms in WT rats and accelerated certain symptoms of PD in PINK1-KO rats. For the first time, our collective data suggest that psychological distress can phenocopy several aspects of PD neuropathology, disrupt brain energy production, as well as induce ataxia-like behavior.
Journal Article
New concepts in anaerobic digestion processes: recent advances and biological aspects
Waste treatment and the simultaneous production of energy have gained great interest in the world. In the last decades, scientific efforts have focused largely on improving and developing sustainable bioprocess solutions for energy recovery from challenging waste. Anaerobic digestion (AD) has been developed as a low-cost organic waste treatment technology with a simple setup and relatively limited investment and operating costs. Different technologies such as one-stage and two-stage AD have been developed. The viability and performance of these technologies have been extensively reported, showing the supremacy of two-stage AD in terms of overall energy recovery from biomass under different substrates, temperatures, and pH conditions. However, a comprehensive review of the advantages and disadvantages of these technologies is still lacking. Since microbial ecology is critical to developing successful AD, many studies have shown the structure and dynamics of archaeal and bacterial communities in this type of system. However, the role of Eukarya groups remains largely unknown to date. In this review, we provide a comprehensive review of the role, abundance, dynamics, and structure of archaeal, bacterial, and eukaryal communities during the AD process. The information provided could help researchers to select the adequate operational parameters to obtain the best performance and biogas production results.
Journal Article