Background
Different skin manifestations of COVID‐19 are being reported. Acral lesions on the hands and feet, closely resembling chilblains, have been recognized during the peak incidence of the ...COVID‐19 pandemic.
Material and methods
A retrospective review of 22 children and adolescents with chilblain‐like lesions seen over a short period of time in the Emergency Department of a children's hospital during the peak incidence of COVID‐19 in Madrid, Spain.
Results
All patients had lesions clinically consistent with chilblains of the toes or feet, with three also having lesions of the fingers. Pruritus and mild pain were the only skin symptoms elicited, and only 10 had mild respiratory and/or GI symptoms. None had fever. Coagulation tests, hemogram, serum chemistry, and lupus anticoagulant were normal in all patients tested. One out of 16 tested cases had elevated D‐dimer results, but without systemic symptoms or other laboratory anomalies. SARS‐CoV‐2 PCR tested in 19 cases was positive in just one case. Skin biopsies obtained in six patients were consistent with chilblains. On follow‐up, all cases showed spontaneous marked improvement or complete healing.
Conclusion
Acute chilblains were observed during COVID‐19 pandemic in children and teenagers. It is a mildly symptomatic condition with an excellent prognosis, usually requiring no therapy. Etiopathogenesis remains unknown.
Abstract
Proton exchange membrane water electrolysis is a promising technology to produce green hydrogen from renewables, as it can efficiently achieve high current densities. Lowering iridium amount ...in oxygen evolution reaction electrocatalysts is critical for achieving cost-effective production of green hydrogen. In this work, we develop catalysts from Ir double perovskites. Sr
2
CaIrO
6
achieves 10 mA cm
−2
at only 1.48 V. The surface of the perovskite reconstructs when immersed in an acidic electrolyte and during the first catalytic cycles, resulting in a stable surface conformed by short-range order edge-sharing IrO
6
octahedra arranged in an open structure responsible for the high performance. A proton exchange membrane water electrolysis cell is developed with Sr
2
CaIrO
6
as anode and low Ir loading (0.4 mg
Ir
cm
−2
). The cell achieves 2.40 V at 6 A cm
−2
(overload) and no loss in performance at a constant 2 A cm
−2
(nominal load). Thus, reducing Ir use without compromising efficiency and lifetime.
The development of new magnetic refrigerants demands an effective investigation of materials with a large magnetocaloric effect in a wide temperature range. Herein, we report on the structural, ...magnetic, and magnetocaloric properties of the two-site disordered double perovskite GdSrCoFeO6 prepared by the modified solid-state synthesis method. Temperature-dependent synchrotron X-ray diffraction analysis revealed that GdSrCoFeO6 crystallizes in the orthorhombic phase (Pnma), with Gd3+/Sr2+ and Co2+/3+/Fe3+/4+ ions randomly distributed on the A- and B-sites, respectively. An observed lattice parameter anomaly around 60 K indicates the occurrence of the magnetoelastic coupling, which coincides with the presence of ferro/ferrimagnetic (FM/FiM) ordering below T C ≈ 65 K from the magnetic measurements. These results match well with our first-principles calculation prediction of low-temperature magnetic (FM/FiM) and electronic (insulating/metal) transitions related to a combined effect of Co and Fe short- and long-range competitions, crossings of spin state at Co ions, and the hybridization degree between Gd-4f and Co-3d states. Additionally, a modified Arrott plot and Kouvel–Fisher analysis were used to establish the nature of the magnetic phase transition in GdSrCoFeO6, yielding the critical exponent β = 1.46(6)/1.45(6), γ = 1.48(5)/1.17(2), and δ = 2.01(3)/1.80(5), respectively. The specific heat analysis reveals two well-defined broad peaks (∼10 and ∼70 K), which match well with a Schottky anomaly (Gd-4f) and the magnetic transition of FM/FiM to paramagnetic order, respectively. The magnetocaloric effect (MCE) analysis reveals a maximum magnetic entropy change ΔS M max ≈ 13 J kg–1 K–1 (at ∼8 K) under a field of 0–7 T. These results evidence that the Schottky anomaly and the magnetoelastic coupling seem to be key factors for driving further enhancements to the MCE in GdSrCoFeO6, making it a possible candidate for cryogenic applications.
During examination of cases of chilblains in children and adolescents, we identified four patients who also showed skin lesions similar to erythema multiforme (EM). They had no other known triggers ...for EM. One of them had a positive PCR for SARS‐CoV‐2, while the other three were negative. Skin biopsies from two patients showed features not typical of EM, such as deep perivascular and perieccrine infiltrate and absence of necrosis of keratinocytes. Immunohistochemistry for SARS‐CoV/SARS‐CoV‐2 spike protein showed granular positivity in endothelial cells and epithelial cells of eccrine glands in both biopsies. All patients had an excellent outcome, and had minimal or no systemic symptoms. The coincidence of EM, a condition commonly related to viruses, and chilblains in the setting of COVID‐19, and the positivity for SARS‐CoV/SARS‐CoV‐2 spike protein by immunohistochemistry strongly suggest a link between EM‐like lesions and SARS‐CoV‐2.
This paper analyzes the process of related diversification at the regional level in two emerging countries: Brazil and Mexico. It claims that apart from regional available capabilities, capabilities ...coming from abroad in the form of imports may play an important role in the development of new products. In this sense, it proposes a new index to measure the impact of imports on the process of product diversification. The empirical analysis confirms that: the process of productive diversification is highly path dependent; productive density explains the creation of advantages in related products; and interregional and international relations contribute to encourage new activities.
The level of unpredictability of the COVID-19 pandemics poses a challenge to effectively model its dynamic evolution. In this study we incorporate the inherent stochasticity of the SARS-CoV-2 virus ...spread by reinterpreting the classical compartmental models of infectious diseases (SIR type) as chemical reaction systems modeled via the Chemical Master Equation and solved by Monte Carlo Methods. Our model predicts the evolution of the pandemics at the level of municipalities, incorporating for the first time (i) a variable infection rate to capture the effect of mitigation policies on the dynamic evolution of the pandemics (ii) SIR-with-jumps taking into account the possibility of multiple infections from a single infected person and (iii) data of viral load quantified by RT-qPCR from samples taken from Wastewater Treatment Plants. The model has been successfully employed for the prediction of the COVID-19 pandemics evolution in small and medium size municipalities of Galicia (Northwest of Spain).
•A stochastic SIR model predicts the evolution of COVID-19 using data from sewage.•Model and software are easily calibrated to be applied in different municipalities.•The model is robust and flexible, adaptable for surveillance of other pathogens.•The model successfully predicts COVID-19 spread in Galician municipalities.
Several compounds with enhanced functional properties of interest in the nutraceutical and medical sectors can be recovered by using the biomass currently wasted in fishing extractive and processing ...activities, promoting the sustainability of this sector and leading to its development under a bio-economical framework. In particular, it has been observed that crustaceans are an important fraction of the total biomass discarded by fisheries, mainly in those metiers involving coastal waters. Crustacean biomass can be destined to the production of chitin/chitosan (in combination with food use of muscle or protein hydrolysates production) since their exoskeletons are one of the most important sources of this polysaccharide available for commercial use. In this work, the sustainability of both the chemical and enzymatic process to obtain chitin at pilot scale was analysed. The three sustainability dimensions were evaluated and integrated by hierarchical methods to provide a consistent comparison baseline between processes. The results indicated that the enzymatic process could be an adequate alternative that should be considered for chitin extraction, especially if water recovery is employed.
Mathematical models provide abstract representations of the information gained from experimental observations on the structure and function of a particular biological system. Conferring a predictive ...character on a given mathematical formulation often relies on determining a number of non-measurable parameters that largely condition the model's response. These parameters can be identified by fitting the model to experimental data. However, this fit can only be accomplished when identifiability can be guaranteed.
We propose a novel iterative identification procedure for detecting and dealing with the lack of identifiability. The procedure involves the following steps: 1) performing a structural identifiability analysis to detect identifiable parameters; 2) globally ranking the parameters to assist in the selection of the most relevant parameters; 3) calibrating the model using global optimization methods; 4) conducting a practical identifiability analysis consisting of two (a priori and a posteriori) phases aimed at evaluating the quality of given experimental designs and of the parameter estimates, respectively and 5) optimal experimental design so as to compute the scheme of experiments that maximizes the quality and quantity of information for fitting the model.
The presented procedure was used to iteratively identify a mathematical model that describes the NF-kappaB regulatory module involving several unknown parameters. We demonstrated the lack of identifiability of the model under typical experimental conditions and computed optimal dynamic experiments that largely improved identifiability properties.
A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health ...risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible.
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