Ana Silva

Recent Developments in Polyurethane Catalysis: Catalytic Mechanisms Review

Abstract In recent years polyurethanes have been confronted with several challenges. Some of these challenges have been overcome with the development of new catalysts. This review article covers recent developments in the field of polyurethane catalysis. An overview of the different types of catalysts, their applications, and their actuation mechanisms, followed by a general survey of the stability of one‐component polyurethane systems in which the latent catalyst is already incorporated is presented.

Control of human β-globin mRNA stability and its impact on beta-thalassemia phenotype

Messenger RNA (mRNA) stability is a critical determinant that affects gene expression. Many pathways have evolved to modulate mRNA stability in response to developmental, physiological and/or environmental stimuli. Eukaryotic mRNAs have a considerable range of half-lives, from as short as a few minutes to as long as several days. Human globin mRNAs constitute an example of highly stable mRNAs. However, a wide variety of naturally occurring mutations that result in the clinical syndrome of thalassemia can trigger accelerated mRNA decay thus controlling mRNA quality prior to translation. Distinct surveillance mechanisms have been described as being targeted for specific defective globin mRNAs. Here, we review mRNA stability mechanisms implicated in the control of β-globin gene expression and the surveillance pathways that prevent translation of aberrant β-globin mRNAs. In addition, we emphasize the importance of these pathways in modulating the severity of the β-thalassemia phenotype.

Tag recommendation for georeferenced photos

This paper presents methods for annotating georeferenced photos with descriptive tags, exploring the annotations for other georeferenced photos which are available at online repositories like Flickr. Specifically, by using the geospatial coordinates associated to the photo which we want to annotate, we start by collecting the photos from an online repository which were taken from nearby locations. Next, and for each tag associated to the collected photos, we compute a set of relevance estimators with basis on factors such as the tag frequency, the geospatial proximity of the photo, the image content similarity, and the number of different users employing the tag. The multiple estimators can then be combined through supervised learning to rank methods such as Rank-Boost or AdaRank, or through unsupervised rank aggregation methods well-known in the information retrieval literature, namely the CombSUM or the CombMNZ approaches. The most relevant tags are finally suggested. Experimental results with a collection of photos collected from Flickr attest for the adequacy of the proposed approaches.

Probabilistic transition of condition: render facades

The service life of cement-rendered facades is closely related to the environmental conditions to which they are exposed. The probability distribution is determined for the degradation condition of render facades considering different environmental exposures. A sample of 100 render facades was subjected to meticulous fieldwork to determine their condition. The analysis focuses on the environmental factors that most influence the overall degradation of the facades, evaluated through the condition level. Probabilistic models based on Markov chains are developed to predict the evolution of facade deterioration according to exposure to outdoor environmental conditions. The proposed model provides data on the synergy between the degradation agents and the degradation condition of render facades, the average time of permanence in each degradation level, and indications of the effect of degradation on the durability of render that may be applied in the implementation and fine-tuning of maintenance procedures. A better understanding of the durability of render facades allows a more rational management of their maintenance, contributing to a reduction of their life cycle costs. The proposed stochastic model provides information that can be applied in the context of insurance policies, allowing an evaluation of the risk of failure of coatings.

Resistance of mRNAs with AUG-proximal nonsense mutations to nonsense-mediated decay reflects variables of mRNA structure and translational activity

Nonsense-mediated mRNA decay (NMD) is a surveillance pathway that recognizes and selectively degrades mRNAs carrying premature termination codons (PTCs). The level of sensitivity of a PTC-containing mRNA to NMD is multifactorial. We have previously shown that human β-globin mRNAs carrying PTCs in close proximity to the translation initiation AUG codon escape NMD. This was called the ‘AUG-proximity effect’. The present analysis of nonsense codons in the human α-globin mRNA illustrates that the determinants of the AUG-proximity effect are in fact quite complex, reflecting the ability of the ribosome to re-initiate translation 3′ to the PTC and the specific sequence and secondary structure of the translated ORF. These data support a model in which the time taken to translate the short ORF, impacted by distance, sequence, and structure, not only modulates translation re-initiation, but also impacts on the exact boundary of AUG-proximity protection from NMD.

Uncertainty modelling of service life and environmental performance to reduce risk in building design decisions

Life-cycle assessment (LCA) is increasingly used to quantify the environmental impacts of construction materials. However, the relationship between the durability and LCA of these complex products with long life-cycles must be analysed in detail, namely using stochastic data from service life prediction (SLP) studies. However, SLP uncertainty is not yet considered in LCA, thus resulting in insufficiently sound decisions at the design stage. This paper presents the modelling of the uncertainty of SLP using advanced statistical methods and its application in the estimation of SL and corresponding number of replacements of claddings (renderings and stone claddings). These results are used in an interdisciplinary study of SLP and LCA to apply in the stochastic comparison of the LCA of claddings. This methodology aids in the choice of the option with better environmental performance right at the design stage, via the comparison of their standard, deterministic and stochastic LCA results.

Sealing Ability of Three Fiber Dowel Systems

PURPOSE To study the sealing ability of two new fiber dowel systems. MATERIALS AND METHODS Thirty-six extracted single-rooted teeth were endodontically treated and randomly assigned to two new fiber dowel systems and a control group: (1) an E-glass-based dowel, everStick-POST, cemented with ParaCem Universal DC resin cement (EV); (2) a glass-fiber dowel, RelyX Fiber Post, cemented with RelyX Unicem self-adhesive resin cement (RX). The control group was restored with a glass-fiber dowel, ParaPost Fiber Lux, cemented with ParaCem Universal DC resin cement (PP). The roots were isolated and immersed in a 50 wt% ammoniacal silver nitrate solution for 24 hours followed by 8 hours in a photo-developing solution. The roots were sectioned in 1-mm-thick disks perpendicular to the long axis of the root. The specimens were processed for backscattered FESEM observation. For each tooth, the depth of silver infiltration into the root canal was measured by ranks from 0 to 8. For each disk, silver infiltration was measured as the percentage of leakage around the adhesive interface. Data were analyzed with Kruskal-Wallis nonparametric tests at a significance level of 95%. RESULTS When the silver infiltration was computed from the coronal to the apical aspects of the root, RX resulted in the lowest degree of silver infiltration, but not statistically different from that of EV (p < 0.148). RX, however, resulted in a lower depth of silver infiltration than the control group PP at p < 0.023. EV resulted in a statistically similar depth of penetration to PP (p= 0.492). Although the total mean percentage of silver infiltration at the dentin-resin cement interface was statistically similar for all groups (p= 0.632), EV resulted in the greater number of disks with silver infiltration (23 out of 96), followed by PP (21 out of 96) and RX (14 out of 96). None of the specimens showed leakage around the dowel-resin cement interface. CONCLUSION The use of the E-glass dowels in EV did not improve the root-wall sealing ability compared with the control group PP. The system RX, which uses a new simplified self-adhesive protocol, resulted in a lower depth of silver infiltration than the control group PP.

Intertidal pools as alternative nursery habitats for coastal fishes

ABSTRACT Fish were sampled monthly in four tidal pools, for two years, on the west Portuguese coast. Species diversity of transient fish was higher than that found in previous studies, in other parts of the world. The transient fish population comprised six species: the white seabream, Diplodus sargus, sand smelt, Atherina spp., the thinlip grey mullet, Liza ramada, the Baillons wrasse, Symphodus bailloni, the zebra seabream, Diplodus cervinus and the European pilchard, Sardina pilchardus. Abundance varied seasonally, yearly, and among pools, with peak numbers in spring and summer. The most abundant species in all pools, both as larvae and juveniles, was D. sargus. Diplodus sargus and Atherina spp. were present in most pools, from spring to autumn, while rare species were present mostly in the spring-summer period. Smaller mean sizes of larvae and juveniles were observed at the beginning of spring of 2011 (March–April) and at the end of spring/beginning of summer of 2012 (May–June). Mean size of larvae and juveniles often showed a continuous increase from spring to autumn in both years. The highest density peaks were due to the high number of post-larvae entering the pools in spring. In most pools, the overall condition (Fultons K) of D. sargus increased throughout the year, in both years. The species richness, the high densities of early stages, and their continuous growth observed in tidal pools strongly emphasize the importance of these environments for larvae and juveniles of several transient marine fishes.

Functional and Physical Service Life of Natural Stone Claddings

AbstractDuring their lifecycle, a building and its components should fulfill a set of performance requirements. However, in reality, from the moment in which a building is placed in use, its deterioration process begins. Buildings and especially their facades, more exposed to the external environmental agents, suffer throughout their service life several types of depreciation, becoming obsolete, economically destitute, or physically deteriorated, leading to the end of their service life. This paper intends to establish a correlation between functional criteria (FBSL) and physical degradation (Sw) in the definition of service-life prediction models. In this study, these models are applied to 203 natural stone claddings (directly adhered to the substrate), located in the Lisbon area, Portugal. The functionality and degradation condition of the facades analyzed are evaluated through visual inspections. Vulnerability and risks (intrinsic and extrinsic variables) are considered in the evaluation of both method...

RAC1b overexpression stimulates proliferation and NF-kB-mediated anti-apoptotic signaling in thyroid cancer cells

Overexpression of tumor-associated RAC1b has been recently highlighted as one of the most promising targets for therapeutic intervention in colon, breast, lung and pancreatic cancer. RAC1b is a hyperactive variant of the small GTPase RAC1 and has been recently shown to be overexpressed in a subset of papillary thyroid carcinomas associated with unfavorable outcome. Using the K1 PTC derived cell line as an in vitro model, we observed that both RAC1 and RAC1b were able to induce a significant increase on NF-kB and cyclin D1 reporter activity. A clear p65 nuclear localization was found in cells transfected with RAC1b-WT, confirming NF-kB canonical pathway activation. Consistently, we observed a RAC1b-mediated decrease in IκBα (NF-kB inhibitor) protein levels. Moreover, we show that RAC1b overexpression stimulates G1/S progression and protects thyroid cells against induced apoptosis, the latter through a process involving the NF-kB pathway. Present data support previous findings suggesting an important role for RAC1b in the development of follicular cell-derived thyroid malignancies and point out NF-kB activation as one of the molecular mechanisms associated with the pro-tumorigenic advantage of RAC1b overexpression in thyroid carcinomas.