Space-time adaptive reduction of unsteady flamalets

The Wavelet Adaptive Multiresolution Representation (WAMR) code and the G-Scheme framework are used for the numerical time integration of the flamelet model. The steep gradients are efficiently captured by the WAMR algorithm with an a-priori defined accuracy and an associated large reduction of the number of degrees of freedom (DOFs). A further opportunity to reduce the complexity of the problem is represented by the G-Scheme, to achieve multi-scale adaptive model reduction along-with the time integration of the differential equations

Numerical generation of multidimensional flamelet databases using an adaptive wavelet method

The Wavelet Adaptive Multiresolution Representation (WAMR) code is used for the numerical time integration of the one-dimensional laminar diffusion flames equations in trans-critical and supercritical conditions, where the thermodynamic and transport properties exhibit large changes. These steep gradients are efficiently captured by the WAMR algorithm with an a-priori defined accuracy and an associated large reduction of the number of degrees of freedom, allowing a highly efficient flamelet database generation critical conditions

The European transhumance network. The ancestral infrastructuring of the territory for settlement rebalance in post-pandemic society.

The lockdown caused by the Covid-19 outbreak was an involuntary socio-environmental experiment demonstrating that the conditions exist to pursue alternative solutions to our short-sighted economic-productive system. Long neglected themes have returned to the center of the debate: the potential of inland areas in the policies of redistribution of settlement density; the value, not only cultural, of secondary historical settlements; the enhancement of ecosystem services due to large-area environmental systems; the role of urban spaces and proximity green spaces for the sustainability of dense settlements. For all these issues, the transhumance system has played a central role over time. In this new scenario, the article reports on a research effort aimed at defining a territorial model for the European transhumance network. The territorial system of transhumance, observed according to the taxonomic hierarchy proposed by the research, will be able to constitute a knowledge base for implementing policies for the conservation of customs, traditions, beliefs, food and wine culture, and expression of the pastoral world. Furthermore, the system may become a coherent framework aimed at assessing the environmental and landscape sustainability of rebalancing settlement transformations in a climate-proof way, with particular reference to the new mobility strategies and new settlement choices that will become appropriate in the post-pandemic era

Do hypoxia/normoxia culturing conditions change the neuroregulatory profile of Wharton Jelly mesenchymal stem cells secretome?

Introduction: The use of human umbilical cord Wharton Jelly-derived mesenchymal stem cells (hWJ-MSCs) has been considered a new potential source for future safe applications in regenerative medicine. Indeed, the application of hWJ-MSCs into different animal models of disease, including those from the central nervous system, has shown remarkable therapeutic benefits mostly associated with their secretome. Conventionally, hWJ-MSCs are cultured and characterized under normoxic conditions (21 % oxygen tension), although the oxygen levels within tissues are typically much lower (hypoxic) than these standard culture conditions. Therefore, oxygen tension represents an important environmental factor that may affect the performance of mesenchymal stem cells in vivo. However, the impact of hypoxic conditions on distinct mesenchymal stem cell characteristics, such as the secretome, still remains unclear. Methods: In the present study, we have examined the effects of normoxic (21 % O2) and hypoxic (5 % O2) conditions on the hWJ-MSC secretome. Subsequently, we address the impact of the distinct secretome in the neuronal cell survival and differentiation of human neural progenitor cells. Results: The present data indicate that the hWJ-MSC secretome collected from normoxic and hypoxic conditions displayed similar effects in supporting neuronal differentiation of human neural progenitor cells in vitro. However, proteomic analysis revealed that the use of hypoxic preconditioning led to the upregulation of several proteins within the hWJ-MSC secretome. Conclusions: Our results suggest that the optimization of parameters such as hypoxia may lead to the development of strategies that enhance the therapeutic effects of the secretome for future regenerative medicine studies and applications. © 2015 Teixeira et al.Portuguese Foundation for Science and Technology (FCT) (Ciência 2007 program and IF Development Grant (AJS); and pre-doctoral fellowships to FGT (SFRH/69637/ 2010) and SIA (SFRH/BD/81495/2011); Canada Research Chairs (LAB) and a SSE Postdoctoral Fellowship (KMP); The National Mass Spectrometry Network (RNEM) (REDE/1506/REM/2005); co-funded by Programa Operacional Regional do Norte (ON.2 – O Novo Norte), ao abrigo do Quadro de Referência Estratégico Nacional (QREN), através do Fundo Europeu de Desenvolvimento Regional (FEDER).info:eu-repo/semantics/publishedVersio

Structure of n-heptane/air triple flames in partially-premixed mixing layers

Results of a detailed numerical analysis of an n-heptane/air edge flame are presented. The equations of a low-Mach number reacting flow are solved in a two-dimensional domain using detailed models for species transport and chemical reactions. The reaction mechanism involves 560 species and 2538 reversible reactions. We consider an edge flame that is established in a mixing layer with a uniform velocity field. The mixing layer spans the equivalence ratios between pure air and 3.5. The detailed model enables us to analyze the chemical structure of the n-heptane edge flame. We identify major species profiles, discuss reactions causing the heat-release, and exploit Computational Singular Perturbation (CSP) to discuss the main fuel-consumption pathways and the structure of explosive modes in the edge flame. This analysis is performed for several regions in the edge flame to discuss the different processes at work in the premixed branches and the trailing diffusion flame. We compare different cuts through the 2D edge flame to canonical 1D premixed and diffusion flames. We also analyze the accuracy of a skeletal mechanism which was previously developed using CSP from homogeneous ignition calculations of n-heptane and show that a significant reduction in size of the mechanism can be achieved without a significant decrease in accuracy of the edge flame computation. This skeletal mechanism is then used to study the effects of increasing the equivalence ratio in the partially-premixed fuel stream

Computational singular perturbation method and tangential stretching rate analysis of large scale simulations of reactive flows: Feature tracking, time scale characterization, and cause/effect identification. Part 1, basic concepts

This chapter provides a review of the basic ideas at the core of the Computational Singular Perturbation (CSP) method and the Tangential Stretching Rate (TSR) analysis. It includes a coherent summary of the theoretical foundations of these two methodologies while emphasizing theirmutual interconnections. The main theoretical findings are presented in a systematic fashion. Their virtues and limitations will be discussed with reference to auto-ignition systems, laminar and turbulent premixed flames, and non-premixed jet flames. The material presented in the chapter constitutes an effective guideline for further studies.SCOPUS: ch.binfo:eu-repo/semantics/publishe

An efficient iterative algorithm for the approximation of the fast and slow dynamics of stiff systems

The relation between the iterative algorithms based on the computational singular perturbation (CSP) and the invariance equation (IE) methods is examined. The success of the two methods is based on the appearance of fast and slow time scales in the dynamics of stiff systems. Both methods can identify the low-dimensional surface in the phase space (slow invariant manifold, SIM), where the state vector is attracted under the action of fast dynamics. It is shown that this equivalence of the two methods can be expressed by simple algebraic relations. CSP can also construct the simplified non-stiff system that models the slow dynamics of the state vector on the SIM. An extended version of IE is presented which can also perform this task. This new IE version is shown to be exactly similar to a modified version of CSP, which results in a very efficient algorithm, especially in cases where the SIM dimension is small, so that significant model simplifications are possible. (c) 2005 Elsevier Inc. All rights reserved