Temperature and particle concentration influence on the complex viscous behavior of a hydrophilic fumed silica suspension

Shear-thinning behavior (decrease of the apparent steady viscosity with shear) due to breaking of weak particle flocs and posterior alignment of individual particles in layers parallel to the flow direction is usually observed before the appearance of the shear-thickening behavior (increase of the apparent steady viscosity with shear). The shear-thickening behavior is mainly due to the dominant role played by hydrodynamic over Brownian and colloidal forces at relatively high shear. As a rule, the onset of shear-thickening behavior and the maximum viscosity value appear at lower shear rates when solid concentration increases, and temperature decreases. However, the influence of solid concentration and temperature on shear stress characteristic values have received less attention despite being the shear stress the true cause of microstructure changes that can provoke the appearance of the shear-thickening behaviour. A recently published empirical equation for the shear stress dependence of the steady viscosity of shear thickening fluids [T. Shende, V.J. Niasar, M. Babaei, J. Mol. Liq. 325 (2021) 115220] has been used for fitting experimental data (MARSIII, Thermo-Haake, Germany) of a hydrophilic fumed silica suspension (A200 (Evonik, Germany) in PPG400 (Sigma-Aldrich, Germany)). The influence of temperature (10,\ 30,\ 50,\ 70\degc) and solid concentration (10,\ 15,\ 20,\ 25%\ wt) on the shear-thickening behavior has been monitored recording their influence on the model parameters.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cabbage and fermented vegetables : From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT(1)R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT(1)R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.Peer reviewe

Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity

Genetic contributors to serum uric acid levels in Mexicans and their effect on premature coronary artery disease

International audienc