Mitigation of the negative effects of recycled aggregate water absorption in concrete technology

The widespread use of natural aggregates in construction activities, together with the global population increase, gave rise to a depletion of this natural resource and to progressive increase of its transport distances. On the other hand, the construction and demolition wastes (C&DW) resulting from the construction activities are often deposited in landfills and city outskirts, causing environmental and social problems, such as erosion, deforestation, water contamination and human conflicts. The reuse of C&DW in concrete preparation would be a good solution for both problems. Recycled aggregates show, however, high water absorption due to porosity. At saturation, water flows from the inside to the engaging cement paste matrix and at dryness the opposite process occurs. This water flow breaks the aggregate-cement paste bonds and increases the W/C ratio in the interfacial transition zone, this degrades the fresh and hardened concrete properties. In this work a staged mixing method based on the aggregate water absorption over time was developed. A staged mixing procedure was optimized to regulate the water flow and manufacture concrete, using recycled aggregates, with levels of workability, strength and shrinkage equivalent to those of conventional concrete. The physical, mechanical and geometrical properties of the aggregates were related to the properties of concrete in its fresh and hardened state. Three types of commercial recycled aggregates were evaluated. Two types of natural aggregates were also studied for comparison purposes. (C) 2016 Elsevier Ltd. All rights reserved.European Regional Development Fund, via Algarve Operational Program [REN 30307 Multi-valor

Reconstructing the projected gravitational potential of Abell 1689 from X-ray measurements

Context. Galaxy clusters can be used as cosmological probes, but to this end, they need to be thoroughly understood. Combining all cluster observables in a consistent way will help us to understand their global properties and their internal structure. Aims. We provide proof of the concept that the projected gravitational potential of galaxy clusters can directly be reconstructed from X-ray observations. We also show that this joint analysis can be used to locally test the validity of the equilibrium assumptions in galaxy clusters. Methods. We used a newly developed reconstruction method, based on Richardson-Lucy deprojection, that allows reconstructing projected gravitational potentials of galaxy clusters directly from X-ray observations. We applied this algorithm to the well-studied cluster Abell 1689 and compared the gravitational potential reconstructed from X-ray observables to the potential obtained from gravitational lensing measurements. [...] Results. Assuming spherical symmetry and hydrostatic equilibrium, the potentials recovered from gravitational lensing and from X-ray emission agree very well beyond 500 kpc. Owing to the fact that the Richardson-Lucy deprojection algorithm allows deprojecting each line of sight independently, this result may indicate that non-gravitational effects and/or asphericity are strong in the central regions of the clusters. Conclusions. We demonstrate the robustness of the potential reconstruction method based on the Richardson-Lucy deprojection algorithm and show that gravitational lensing and X-ray emission lead to consistent gravitational potentials. Our results illustrate the power of combining galaxy-cluster observables in a single, non-parametric, joint reconstruction of consistent cluster potentials that can be used to locally constrain the physical state of the gas.Comment: 8 pages, 4 figures. Accepted in A&

Sedimentation of colloidal plate-sphere mixtures and inference of particle characteristics from stacking sequences

We investigate theoretically the effect of gravity on a plate-sphere colloidal mixture by means of an Onsager-like density functional to describe the bulk, and sedimentation path theory to incorporate gravity. We calculate the stacking diagram of the mixture for two sets of buoyant masses and different values of the sample height. Several stacking sequences appear due to the intricate interplay between gravity, the sample height, and bulk phase separation. These include the experimentally observed floating nematic sequence, which consists of a nematic layer sandwiched between two isotropic layers. The values of the thicknesses of the layers in a complex stacking sequence can be used to obtain microscopic information of the mixture. Using the thicknesses of the layers in the floating nematic sequence we are able to infer the values of the buoyant masses from the colloidal concentrations and vice versa. We also predict new phenomena that can be experimentally tested, such as a nontrivial evolution of the stacking sequence by increasing the sample height in which new layers appear either at the top or at the bottom of the sample

Sedimentation path theory for mass-polydisperse colloidal systems

Both polydispersity and the presence of a gravitational field are inherent to essentially any colloidal experiment. While several theoretical works have focused on the effect of polydispersity on the bulk phase behavior of a colloidal system, little is known about the effect of a gravitational field on a polydisperse colloidal suspension. We extend here sedimentation path theory to study sedimentation of a mass-polydisperse colloidal system: the particles possess different buoyant masses but they are otherwise identical. The model helps to understand the interplay between gravity and polydispersity on sedimentation experiments. Since the theory can be applied to any parent distribution of buoyant masses, it can be also used to study sedimentation of monodisperse colloidal systems. We find that mass-polydispersity has a strong influence in colloidal systems near density matching for which the bare density of the colloidal particles equals the solvent density. To illustrate the theory, we study crystallization in sedimentation-diffusion-equilibrium of a suspension of mass-polydisperse hard spheres

Prediction of regulatory targets of alternative isoforms of the epidermal growth factor receptor in a glioblastoma cell line.

BackgroundThe epidermal growth factor receptor (EGFR) is a major regulator of proliferation in tumor cells. Elevated expression levels of EGFR are associated with prognosis and clinical outcomes of patients in a variety of tumor types. There are at least four splice variants of the mRNA encoding four protein isoforms of EGFR in humans, named I through IV. EGFR isoform I is the full-length protein, whereas isoforms II-IV are shorter protein isoforms. Nevertheless, all EGFR isoforms bind the epidermal growth factor (EGF). Although EGFR is an essential target of long-established and successful tumor therapeutics, the exact function and biomarker potential of alternative EGFR isoforms II-IV are unclear, motivating more in-depth analyses. Hence, we analyzed transcriptome data from glioblastoma cell line SF767 to predict target genes regulated by EGFR isoforms II-IV, but not by EGFR isoform I nor other receptors such as HER2, HER3, or HER4.ResultsWe analyzed the differential expression of potential target genes in a glioblastoma cell line in two nested RNAi experimental conditions and one negative control, contrasting expression with EGF stimulation against expression without EGF stimulation. In one RNAi experiment, we selectively knocked down EGFR splice variant I, while in the other we knocked down all four EGFR splice variants, so the associated effects of EGFR II-IV knock-down can only be inferred indirectly. For this type of nested experimental design, we developed a two-step bioinformatics approach based on the Bayesian Information Criterion for predicting putative target genes of EGFR isoforms II-IV. Finally, we experimentally validated a set of six putative target genes, and we found that qPCR validations confirmed the predictions in all cases.ConclusionsBy performing RNAi experiments for three poorly investigated EGFR isoforms, we were able to successfully predict 1140 putative target genes specifically regulated by EGFR isoforms II-IV using the developed Bayesian Gene Selection Criterion (BGSC) approach. This approach is easily utilizable for the analysis of data of other nested experimental designs, and we provide an implementation in R that is easily adaptable to similar data or experimental designs together with all raw datasets used in this study in the BGSC repository, https://github.com/GrosseLab/BGSC

Avaliação da influência da retração inicial no controlo da fissuração dos betões

A fissuração em idade precoce reemergiu como um problema em betão/argamassa moderno, com o uso de materiais com altas resistências mecânicas. Este tipo de fissuração resulta da retração do betão, que quando associada a restrições internas e externas cria tensões, aumentando a suscetibilidade à fissuração. Distinguem-se vários tipos de retração: plástica, química, autogénea térmica e por secagem, que são influenciadas por fatores ambientais e fatores intrínsecos ao material. A fissuração permite o ingresso de agentes atmosféricos que conduzem a uma deterioração pré-matura do betão, cuja mitigação constitui a motivação desta tese de mestrado. O objetivo do trabalho experimental consiste em avaliar a influência dos tempos de presa na atuação de adições expansivas em betão autocompactável. Espera-se que diferentes estados de rigidez microestrutural modifiquem o efeito de expansão. Para esse fim foram executados ensaios de: trabalhabilidade, tempos de presa, resistência à compressão e tração, módulo de elasticidade, retração química e total, perda de peso e por último, o ensaio de anel. Os resultados do trabalho experimental mostram que o aumento dos tempos de presa prolongam a fase expansiva, o que levou à diminuição de retração e fissuração a médio prazo, mas a longo prazo não se verificou qualquer alteração da retração. Conclui-se que este estudo constitui uma informação importante para avaliar o efeito de retardadores de presa nas propriedades avaliadas e que a sua combinação com expansivos trás algumas melhorias na fissuração; ### ABSTRACT: Evaluation of the Influence of Early Age Shrinkage on the Control of Concrete Cracking The early age cracking reemerged as a problem in modern concrete/mortar, with the use of high strength materials. This type of cracking results from the concrete shrinkage, when it is associated to selfand external-restraint it creates tensions, increasing the cracking susceptibility. There are discriminated several types of shrinkage: plastic, chemical, autogenous, thermal and drying, which are influenced by environmental factors and inherent factors to the material. The cracking allows the ingress of atmospheric agents that lead to pre-mature deterioration of concrete, whose mitigation is the motivation of this master thesis. The objective of the experimental work consists in evaluate the influence of setting-time on the performance of expansive admixtures in self-compacting concrete. It is expected that different states of microstructural stiffness modifies the expansion effect. For this purpose were executed tests for: workability; setting time; compressive and tensile-strength; Young's modulus; chemical and overall shrinkage; mass loss and finally the Ring Test. The results of the experimental work show that the increase of setting time extends the expansive phase, that leaves to an decrease of shrinkage and cracking at medium term, but at long term there was no change of the shrinkage. It can be concluded that this study constitutes an important information to evaluate the effect of retarder in the evaluated properties and that it's combination with expansive admixtures brings some improvements in cracking