89 research outputs found
Lateral pressure of nano-engineered SCC combining nanoclays, nanosilica and viscosity modifying admixtures
Self-compacting concrete (SCC) is an energy efficient building technology widely used for multiple constructive applications. However, the large flowability of fresh SCC produces an increase of the lateral pressure exerted on the formwork regarding to conventional concretes. One solution to reduce the maximum lateral pressure (Pmax) is to modulate the fresh performance of SCC by the addition of rheology modifiers. Among them, nanocomponents highlight due to their larger efficiency derived from their tiny particle size. In this study, the efficiency of nano-engineered SCC (NE-SCC) combining small amounts of nanocomponents, as nanoclays and nanosilica, with viscosity modifying admixtures (VMAs) to decrease Pmax is explored. Lateral pressure exerted by NE-SCC on cylindrical columns subjected to self-weight and to air pressure was assessed using wall and capillary pressure sensors over time. It was found that the incorporation of attapulgite and bentonite nanoclays combined with VMAs could reduce Pmax. This reduction was measured with wall and capillary pressure sensors on self-weight column and air pressure column laboratory tests, and good correlation between them over time was obtained. A predictive model of the maximum lateral Pressure (Pmax) and its evolution over time (PL) was proposed, related to SCC paste thixotropy (Athix,p), casting height (H) and SCC pressure decay coefficient (Cd).The authors acknowledge with thanks the financial support provided by the projects NanoCompaC (BIA2016-77911-R), funded by the Spanish Ministry of Economy and Competitiveness, and Print3Dcement (PID2019-106525RB-I00), funded by the Spanish Ministry of Science and Innovation, and the Grant for training of Lecturers (FPU-UAH 2019), funded by University of Alcalå. Finally yet importantly, the authors are grateful to TOLSA GROUP S.A, Master Builders Solutions España SLU, Omya Clariana and Cementos Portland Valderrivas, SA for supplying at no charge some components used in the tests
Intramolecular carbolithiation of <i>N</i>-allyl-<i>N</i>-2-lithioallylamines: effect of the allyl moiety
Iodine Atoms: A New Molecular Feature for the Design of Potent Transthyretin Fibrillogenesis Inhibitors
The thyroid hormone and retinol transporter protein known as transthyretin (TTR) is in the origin of one of the 20 or so known amyloid diseases. TTR self assembles as a homotetramer leaving a central hydrophobic channel with two symmetrical binding sites. The aggregation pathway of TTR into amiloid fibrils is not yet well characterized but in vitro binding of thyroid hormones and other small organic molecules to TTR binding channel results in tetramer stabilization which prevents amyloid formation in an extent which is proportional to the binding constant. Up to now, TTR aggregation inhibitors have been designed looking at various structural features of this binding channel others than its ability to host iodine atoms. In the present work, greatly improved inhibitors have been designed and tested by taking into account that thyroid hormones are unique in human biochemistry owing to the presence of multiple iodine atoms in their molecules which are probed to interact with specific halogen binding domains sitting at the TTR binding channel. The new TTR fibrillogenesis inhibitors are based on the diflunisal core structure because diflunisal is a registered salicylate drug with NSAID activity now undergoing clinical trials for TTR amyloid diseases. Biochemical and biophysical evidence confirms that iodine atoms can be an important design feature in the search for candidate drugs for TTR related amyloidosis
Ruthenium/TFA-catalyzed regioselective C-3-alkylation of indoles with terminal alkynes in water: efficient and unprecedented access to 3-(1-methylalkyl)-1H-indoles
Los retos de nuestra sociedad en el siglo XXI: una breve reflexiĂłn desde el ĂĄmbito de la QuĂmica
This article is thought to give a brief reflection about the dependence of the society on
chemistry. Specifically, it is focused on topics as relevant as health, national security, food, and
energy. Finally, the responsibility that we have to assume as chemists in order to propose further
actions is taken into consideration.En este artĂculo se muestra una breve reflexiĂłn sobre la dependencia que tiene nuestra
sociedad de la QuĂmica en ĂĄmbitos tan importantes como la salud, la seguridad nacional la
alimentaciĂłn o la energĂa y la responsabilidad, que como quĂmicos, tenemos y debemos asumir de
cara al futuro
A simple and efficient âone-potâ synthesis of 2-aza-1,3-butadienes from N-vinylic λ5phosphazenes
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