Étude expérimentale et numérique pour la caractérisation thermique des bétons à changement de phase (BCP)

In order to satisfy the technological challenges required by the new building concepts in the aim of improved performances in terms of durability, thermal comfort and respect for the environment, many research ideas have been considered by researchers and building professionals. Among these ideas, the reinforcement of construction materials by innovative and eco-efficient materials known as phase change materials (PCM) has attractive and promising advantages. Known for their high latent heat storage capacities, PCMs combined with cementitious materials such as concrete, are presented in the construction market as potential and intelligent actors for “clean” and sustainable construction. However, when PCMs are incorporated into the concrete paste, the estimation of the thermal conductivity and the specific heat capacity of the latter is not trivial and thus requires solving the optimization problems known as “inverse heat transfer problems”. In this context, this work proposes an iterative parametric optimization procedure, using a numerical model developed in order to estimate the thermal conductivity and the specific heat of the material containing the PCMs, such as phase change concrete, for example. To achieve this, we will use thermograms obtained from experimental tests carried out with an experimental DEsProTherm, developed at the I2M laboratory of ENSAMBordeaux and based on the method of the hot plan. The tests were carried out on different types of concrete samples incorporating different amounts of PCM

Hypoxia promotes the phenotypic change of aldehyde dehydrogenase activity of breast cancer stem cells

Stable breast cancer cell (BCC) lines are valuable tools for the identification of breast cancer stem cell (BCSC) phenotypes that develop in response to several stimuli as well as for studying the basic mechanisms associated with the initiation and maintenance of BCSCs. However, the characteristics of individual, BCC-derived BCSCs varies and these cells show distinct phenotypes depending on the different BCSC markers used for their isolation. Aldehyde dehydrogenase (ALDH) activity is just such a recognized biomarker of BCSCs with a CD44+/CD24− phenotype. We isolated BCSCs with high ALDH activity (CD44+/CD24−/Aldefluorpos) from a primary culture of human breast cancer tissue and observed that the cells had stem cell properties compared to BCSCs with no ALDH activity (CD44+/CD24−/Aldefluorneg). Moreover, we found Aldefluorpos BCSCs had a greater hypoxic response and subsequent induction of HIF-1α expression compared to the Aldefluorneg BCSCs. We also found that knocking down HIF-1α, but not HIF-2α, in Aldefluorpos BCSCs led to a significant reduction of the stem cell properties through a decrease in the mRNA levels of genes associated with the epithelial-mesenchymal transition. Indeed, HIF-1α overexpression in Aldefluorneg BCSCs led to Slug and Snail mRNA increase and the associated repression of E-cadherin and increase in Vimentin. Of note, prolonged hypoxic stimulation promoted the phenotypic changes of Aldefluorneg BCSCs including ALDH activity, tumorigenesis and metastasis, suggesting that hypoxia in the tumor environment may influence BCSC fate and breast cancer clinical outcomes