Catalysts, autocatalysis and the origin of metabolism

If life on Earth started out in geochemical environments like hydrothermal vents, then it started out from gasses like CO2, N2 and H2. Anaerobic autotrophs still live from these gasses today, and they still inhabit the Earth's crust. In the search for connections between abiotic processes in ancient geological systems and biotic processes in biological systems, it becomes evident that chemical activation (catalysis) of these gasses and a constant source of energy are key. The H2-CO2 redox reaction provides a constant source of energy and anabolic inputs, because the equilibrium lies on the side of reduced carbon compounds. Identifying geochemical catalysts that activate these gasses en route to nitrogenous organic compounds and small autocatalytic networks will be an important step towards understanding prebiotic chemistry that operates only on the basis of chemical energy, without input from solar radiation. So, if life arose in the dark depths of hydrothermal vents, then understanding reactions and catalysts that operate under such conditions is crucial for understanding origins

Mechanical study of PLA-PCL fibers during in vitro degradation

The aliphatic polyesters are widely used in biomedical applications since they are susceptible to hydrolytic and/or enzymatic chain cleavage, leading to alpha-hydroxyacids, generally metabolized in the human body. This is particularly useful for many biomedical applications, especially, for temporary mechanical supports in regenerative medical devices. Ideally, the degradation should be compatible with the tissue recovering. In this work, the evolution of mechanical properties during degradation is discussed based on experimental data. The decrease of tensile strength of PLA-PCL fibers follows the same trend as the decrease of molecular weight, and so it can also be modeled using a first order equation. For each degradation stage, hyperelastic models such as Neo-Hookean, Mooney-Rivlin and second reduced order, allow a reasonable approximation of the material behavior. Based on this knowledge, constitutive models that describe the mechanical behavior during degradation are proposed and experimentally validated. The proposed theoretical models and methods may be adapted and used in other biodegradable materials, and can be considered fundamental tools in the design of regenerative medical devices where strain energy is an important requirement, such as, for example, ligaments, cartilage and stents

Linear-in-the-parameters oblique least squares (LOLS) provides more accurate estimates of density-dependent survival

Survival is a fundamental demographic component and the importance of its accurate estimation goes beyond the traditional estimation of life expectancy. The evolutionary stability of isomorphic biphasic life-cycles and the occurrence of its different ploidy phases at uneven abundances are hypothesized to be driven by differences in survival rates between haploids and diploids. We monitored Gracilaria chilensis, a commercially exploited red alga with an isomorphic biphasic life-cycle, having found density-dependent survival with competition and Allee effects. While estimating the linear-in-the-parameters survival function, all model I regression methods (i.e, vertical least squares) provided biased line-fits rendering them inappropriate for studies about ecology, evolution or population management. Hence, we developed an iterative two-step non-linear model II regression (i.e, oblique least squares), which provided improved line-fits and estimates of survival function parameters, while robust to the data aspects that usually turn the regression methods numerically unstable

A baseline evaluation of atmospheric and river discharge conditions in the Hudson Bay Complex during 2016-2018

In this article, we examine atmospheric and river discharge conditions within the Hudson Bay Complex for the BaySys 2016–2018 field program time frame. Investigated in particular is a subset of European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis - Interim (ERA-Interim) atmospheric forcing variables, namely 2-m surface temperature, 10-m surface winds, precipitation, and sea-level pressure, in addition to river discharge. Results from this assessment show that 2016 was characterized by unusually warm conditions (terrestrial and marine) throughout the annual cycle; 2017 by strong cyclone activity in March and high precipitation in January, October, and November; and 2018 by cold and windy conditions throughout the annual cycle. Evaluation of terrestrial conditions showed higher than normal land surface temperatures (the Hudson Bay physical watershed) for all of the 2016–2018 period (excluding a colder than normal spell August–November 2018), particularly in January (2016 and 2017), higher than normal precipitation in October (2016 and 2017), and higher than normal terrestrial discharge to the Hudson Bay Complex in March (2016 and 2017), with drier than average June through October (2016–2018)

Intravenous immunoglobulin in dermatology – clinical experience in Hospital de Braga

Introdução: Nos últimos anos tem aumentado a experiência clínica com o uso de Imunoglobulinas Endovenosas (IgEv) em Dermatologia. Apesar da informação limitada na literatura, a utilização off-label das IgEv tem demonstrado eficácia na terapêutica de várias dermatoses refratárias aos tratamentos convencionais. Material e métodos: Efetuou-se um estudo retrospetivo dos doentes com patologia dermatológica tratados com IgEv entre Janeiro de 2004 e Outubro de 2011 no Serviço de Dermatologia do Hospital de Braga. Foram analisadas as características demográficas e clínicas, as terapêuticas efetuadas, a resposta clínica e o perfil de segurança. Resultados: Foram tratados 21 doentes com IgEv em 10 diferentes patologias dermatológicas: quatro doentes com Pênfigo Vulgar [2 com resposta completa (RC), um com resposta parcial (RP) e outro que interrompeu o tratamento por efeito lateral grave]; dois doentes com Penfigóide Bolhoso (um com RC e outro com RP); três doentes com Necrólise Epidérmica Tóxica (NET) com RC; dois doentes com Dermatomiosite (ambos com RP); quatro doentes com Urticária Crónica (um com RC, um com RP, um que não respondeu e outro que suspendeu o tratamento por efeito lateral); dois doentes com Vasculopatia Livedóide com RP; um doente com Síndrome CREST que não melhorou; um doente com Escleromixedema com RP; um doente com Pioderma Gangrenoso com RC e uma doente com Dermite Atópica que interrompeu o tratamento na sequência de gravidez. Com excepção dos 3 doentes com NET, em todos os outros a doença havia sido refratária aos tratamentos sistémicos convencionais. Conclusões: Apesar de a nossa experiência ser limitada, o tratamento com IgEv pode ser benéfico em determinadas patologias que não melhoram com o tratamento clássico. Atendendo ao seu custo elevado e efeito terapêutico variável, o seu uso deve ser criterioso até que mais estudos definam a relação risco-benefício