Lithium‐sulfur batteries stands out as a promising technology for energy storage owing to a combination of favorable characteristics including a high theoretical gravimetric capacity, energy density, ...inexpensive character, and environmental benignity. Covalent organic frameworks (COFs) are a rapidly developing family of functional nanostructures which combine porosity and crystallinity, and which have been already used in these kinds of batteries to build sulfur electrodes, by embedding sulfur into porous COFs in order to enhance cycle lifetimes. In this contribution, this is taken one step forward and a COF endowed with vinyl groups is used, in order to graft sulfur to the COF skeleton through inverse vulcanization. The main aim of the article is to show the synergistic effect of covalent bonding and physical encapsulation of sulfur in the pores of the COF in order to alleviate the fatal redox shuttling process, to improve the cycling performance, and to provide faster ion diffusion pathways. In addition, it is shown how the material with covalently‐bound S provides better electrochemical performance under demanding and/or changeable charge conditions than a parent analogue material with sulfur physically confined, but without covalent linkage.
COF it up: Synergistic effect of covalent bonding and physical encapsulation of sulfur in the pores of a COF alleviates the fatal redox shuttling process, improves the cycling performance and provides faster ion diffusion pathways in lithium‐sulfur batteries.
There is great scientific and popular interest in understanding the genetic history of populations in the Americas. We wish to understand when different regions of the continent were inhabited, where ...settlers came from, and how current inhabitants relate genetically to earlier populations. Recent studies unraveled parts of the genetic history of the continent using genotyping arrays and uniparental markers. The 1000 Genomes Project provides a unique opportunity for improving our understanding of population genetic history by providing over a hundred sequenced low coverage genomes and exomes from Colombian (CLM), Mexican-American (MXL), and Puerto Rican (PUR) populations. Here, we explore the genomic contributions of African, European, and especially Native American ancestry to these populations. Estimated Native American ancestry is 48% in MXL, 25% in CLM, and 13% in PUR. Native American ancestry in PUR is most closely related to populations surrounding the Orinoco River basin, confirming the Southern American ancestry of the Taíno people of the Caribbean. We present new methods to estimate the allele frequencies in the Native American fraction of the populations, and model their distribution using a demographic model for three ancestral Native American populations. These ancestral populations likely split in close succession: the most likely scenario, based on a peopling of the Americas 16 thousand years ago (kya), supports that the MXL Ancestors split 12.2kya, with a subsequent split of the ancestors to CLM and PUR 11.7kya. The model also features effective populations of 62,000 in Mexico, 8,700 in Colombia, and 1,900 in Puerto Rico. Modeling Identity-by-descent (IBD) and ancestry tract length, we show that post-contact populations also differ markedly in their effective sizes and migration patterns, with Puerto Rico showing the smallest effective size and the earlier migration from Europe. Finally, we compare IBD and ancestry assignments to find evidence for relatedness among European founders to the three populations.
•Utilization of an algebraic differential approach and a modified, augmented system (immersion) of the A-SIR model.•Development of a non redundant and model-free observer. No reconstruction of known ...variables. Full model is not required•The estimation algorithm is robust. Asymptotically stable (noise-free) or ultimate uniformly bounded (noise).•.•Reconstruction of the variables of interest by means of integration processes (Liouvillian system).•Validation of the methodology with real data reported by the Mexican Government.
Due to the current COVID-19 pandemic, much effort has been put on studying the spread of infectious diseases to propose more adequate health politics. The most effective surveillance system consists of doing massive tests. Nonetheless, many countries cannot afford this class of health campaigns due to limited resources. Thus, a transmission model is a viable alternative to study the dynamics of the pandemic. The most used are the Susceptible, Infected and Removed type models (SIR). In this study, we tackle the population estimation problem of the A-SIR model, which takes into account asymptomatic or undetected individuals. By means of an algebraic differential approach, we design a model-free (no copy system) reduced-order estimation algorithm (observer) to determine the different non-measured population groups. We study two types of estimation algorithms: Proportional and Proportional-Integral. Both shown fast convergence speed, as well as a minimal estimation error. Additionally, we introduce random fluctuations in our analysis to represent changes in the external conditions and which result in poor measurements. The numerical results reveal that both model-free estimators are robust despite the presence of these fluctuations. As a point of reference, we apply the classical Luenberger type observer to our estimation problem and compare the results. Finally, we consider real data of infected individuals in Mexico City, reported from February 2020 to March 2021, and estimate the non-measured populations. Our work’s main goal is to proportionate a simple and therefore, an accessible methodology to estimate the behavior of the COVID-19 pandemic from the available data, such that the competent authorities can propose more adequate health politics.
This paper presents a methodology and design of a model-free-based proportional-integral reduced-order observer for a class of nondifferentially flat systems. The problem is tackled from a ...differential algebra point of view, that is, the state observer for nondifferentially flat systems is based on algebraic differential polynomials of the output. The observation problem is treated together with that of a synchronization between a chaotic system and the designed observer. Some basic notions of differential algebra and concepts related to chaotic synchronization are introduced. The PI observer design methodology is given and it is proven that the estimation error is uniformly ultimately bounded. To exemplify the effectiveness of the PI observer, some cases and their respective numerical simulation results are presented.
This contribution considers proto-cell structures associated with asymmetries, mainly gravity, in the framework of reaction–diffusion. There are equivalent solutions for defined morphogen parameters ...in the equations that allow for defining proto-tissue complexity and configurational entropy. Using RNA data, improvements to the complexity and entropy due to the Earth’s gravity are presented. The theoretical proto-tissues complexity estimation, as a function of arbitrary surface gravity, is likewise proposed. In this sense, hypothetical aggregates of proto-cells on Mars would have a lower complexity than on Earth, which is equally valid for the Moon. Massive planets, or exoplanets like BD+20594b, could have major proto-tissue complexity and, eventually, rich biodiversity.
A series of 8‐hydroxyquinoline derivatives were theoretically characterized and tested as potential antennas in a set of designed lanthanide complexes. The molecular structure and ligand localized ...nature of the excited states were studied in the framework of the multiconfigurational methods CASSCF/NEVPT2 combined with TD‐DFT‐based approaches, which allow applying a fragmentation scheme in the analysis of the most probable sensitization pathway via antenna effect. The photophysical properties of all the complexes and antennas were carefully analyzed, predicting the most probable energy transfer pathways. Rate constants for photophysical processes involved in the mechanism showed a significant contribution of the vibronic coupling in all cases, and the predominant intersystem‐crossing between S1 and T1 states was demonstrated from the analysis of the nature of the wave function of those states. The energy transfer process described herein demonstrates the possibility of Eu(III) and Nd(III) sensitization by the studied ligands. The proposed methodology gives a complete picture of the antenna excited state dynamics.
A series of 8‐hydroxyquinoline derivatives were characterized and tested as potential antennas in a set of designed lanthanide complexes. Multiconfigurational (CASSCF/NEVPT2) and TDDFT calculations in the ground and excited states allows to determine the most probable energy transfer pathway to NdIII, EuIII, and TbIII ions.
Although long‐standing theory suggests that biotic variables are only relevant at local scales for explaining the patterns of species' distributions, recent studies have demonstrated improvements to ...species distribution models (SDMs) by incorporating predictor variables informed by biotic interactions. However, some key methodological questions remain, such as which kinds of interactions are permitted to include in these models, how to incorporate the effects of multiple interacting species, and how to account for interactions that may have a temporal dependence. We addressed these questions in an effort to model the distribution of the monarch butterfly Danaus plexippus during its fall migration (September–November) through Mexico, a region with new monitoring data and uncertain range limits even for this well‐studied insect. We estimated species richness of selected nectar plants (Asclepias spp.) and roosting trees (various highland species) for use as biotic variables in our models. To account for flowering phenology, we additionally estimated nectar plant richness of flowering species per month. We evaluated three types of models: climatic variables only (abiotic), plant richness estimates only (biotic) and combined (abiotic and biotic). We selected models with AICc and additionally determined if they performed better than random on spatially withheld data. We found that the combined models accounting for phenology performed best for all three months, and better than random for discriminatory ability but not omission rate. These combined models also produced the most ecologically realistic spatial patterns, but the modeled response for nectar plant richness matched ecological predictions for November only. These results represent the first model‐based monarch distributional estimates for the Mexican migration route and should provide foundations for future conservation work. More generally, the study demonstrates the potential benefits of using SDM‐derived richness estimates and phenological information for biotic factors affecting species distributions.
Periodontal disease refers to inflammation of the tissues that support the tooth. It is of multifactorial etiology. Innate and adaptive immune cells participate jointly through the release of their ...molecules and mechanisms of action in order to maintain homeostasis in periodontal tissues, so the host's immune response plays an essential role in defense against microorganisms. However, bacterial persistence and the dysregulation of the immune system as an exaggerated response can lead to the worsening of periodontal disease, leading to loss of gingival tissue and alveolar bone and thereby loss of teeth. Therefore, a better understanding of the cellular mechanisms involved in the development of periodontal disease is necessary to design new treatments and prophylactic measures in order to decrease the prevalence of this disease that afflicts a large part of the world population.
Health systems worldwide consider cancer a disease that causes the highest number of deaths per year. The low efficacy of current cancer therapies has led other areas of science to search for new ...alternatives, including nanomaterial sciences. Selenium nanoparticles have anticancer activity, as revealed by in vitro tests performed on prostate, breast, cervical, lung, colorectal, and liver cancer cell lines. Studies attribute anticancer activity to the anti-metastatic effect due to the inhibition of migration and invasion processes. The antiproliferative effect is the low expression of molecules such as cyclin D1, cyclin E, and CDK2. In addition to the activation of cell apoptosis by caspase-dependent mechanisms, there is a low expression of anti-apoptotic proteins such as Bcl-2 and a high expression of the apoptotic proteins like Bax and Bad. Other studies attribute anticancer activity to the activation of cell necroptosis, where molecules such as TNF and IRF1 participate. The pharmacological potential of selenium nanoparticles depends primarily on the administered dose, particle size, and chemical composition. Furthermore, several studies have shown that the administration of these nanoparticles is safe due to their low toxicity in non-cancerous cells. In this review, the most relevant antecedents on the anticancer potential of selenium nanoparticles in prostate, breast, cervical, lung, liver, and colorectal cancer cell lines are discussed.
Many of today's central banks in Latin America were established in the interwar period. During the 1920s, most of them were designed under the influence of money doctors. The main mandate of these ...new institutions was to cope with inflation and provide exchange stability. This article analyses how these central banks responded to the onset of the Great Depression. I show that, in accordance with the requirements of the monetary regime, central banks initially acted to prevent capital outflows and to protect their gold reserves. This led to a credit drop to the private sector. Additional credit was made available once governments decided to intervene more actively in the economy, thereby disregarding the advice of money doctors. The central banks that were founded in the 1930s, and the reforms introduced to those already operating, were conceived to face the effects of the crisis.
PDF
