The Two-Dimensional Analogue of General Relativity

General Relativity in three or more dimensions can be obtained by taking the limit $\omega\rightarrow\infty$ in the Brans-Dicke theory. In two dimensions General Relativity is an unacceptable theory. We show that the two-dimensional closest analogue of General Relativity is a theory that also arises in the limit $\omega\rightarrow\infty$ of the two-dimensional Brans-Dicke theory.Comment: 8 pages, LaTeX, preprint DF/IST-17.9

BLACK HOLES IN THREE-DIMENSIONAL DILATON GRAVITY THEORIES

Three dimensional black holes in a generalized dilaton gravity action theory are analysed. The theory is specified by two fields, the dilaton and the graviton, and two parameters, the cosmological constant and the Brans-Dicke parameter. It contains seven different cases, of which one distinguishes as special cases, string theory, general relativity and a theory equivalent to four dimensional general relativity with one Killing vector. We study the causal structure and geodesic motion of null and timelike particles in the black hole geometries and find the ADM masses of the different solutions.Comment: 19 pages, latex, 4 figures as uuencoded postscript file

Pyrethroid pesticide metabolite, 3-PBA, in soils: method development and application to real agricultural soils

3-Phenoxybenzoic acid (3-PBA) is a shared metabolite of several synthetic pyrethroid pesticides (SPs) resulting from environmental degradation of parent compounds and thus occurs frequently as a residue in samples. Hence, the importance of 3-PBA evaluation after pyrethroid application. There is a gap of analytical methods to determine 3-PBA in soil samples. Therefore, an analytical method that combines the solid-phase extraction (SPE) and gas chromatography-mass spectrometry (GC/MS) detection has been developed for the determination of 3-PBA in soil samples. The analytical method was validated in terms of linearity, sensitivity, intra- and inter-day batch precisions, recoveries, and quantification limits. An SPE method using a Strata X cartridge allows obtaining limits of detection and quantification equal to 4.0 and 13.3 ng g-1, respectively. Under optimized conditions, the method average recovery levels ranged from 70.3 to 93.5% with a relative standard deviation below 3.4%. Method intra- and inter-day precision was under 5.0 and 4.8%, respectively. The developed method was applied to 11 agricultural soil samples in the north of Portugal. The developed methodology allowed for the determination of the pyrethroid metabolite, 3-PBA, in agricultural soil samples at levels of few ng g-1. Graphical abstract ᅟ.I. Bragança is financially supported by FCT through the doctoral research grant financed by fellowship (SFRH/BD/52504/2014). This work was supported by the Associate Laboratory for Green Chemistry-LAQV which is financed by national funds from FCT/MCTES (UID/QUI/50006/2013) and co-financed by the ERDF under the PT2020 Partnership Agreement (POCI-01-0145-FEDER-007265).info:eu-repo/semantics/publishedVersio

Assessment of Pyrethroid Pesticides in Topsoils in Northern Portugal

Pyrethroid insecticides are emerging contam-inants broadly used for insect pest control in agriculture,veterinary, and domestic applications. Limited informa-tion can be found in literature regarding pyrethroidpesticide soil contamination in playgrounds and agricul-tural areas. The focus of this study was on new findingsrelated to the spatial and seasonal occurrence of pyre-throid pesticide contamination in soils of northern Por-tugal. The soils were tested during summer and winterseasons. Pyrethroid pesticides were not found in the tenplaygrounds sampled during both seasons. For the 18agricultural soil samples tested, deltamethrin was theonly pyrethroid detected, just during the summer sea-son. For those, three of the samples taken were found tobe positive with concentrations between 15.7 and101.7 ng g−1. The results denote the need for monitoringand assessment of pyrethroid pesticide contamination inPortuguese soil. Further research is needed to access the ecological potential impact of pyrethroid pesticides onsoil.This work was supported by the Associ-ate Laboratory for Green Chemistry - LAQV which is financed bythe national funds from FCT/MCTES (UID/QUI/50006/2013) andco-financed by the ERDF under the PT2020 Partnership Agree-ment (POCI-01-0145-FEDER - 007265).info:eu-repo/semantics/publishedVersio

A sustainable production of natural hydraulic lime mortars through bio-amendment

.This article examined the effect of a bioproduct suspension obtained from fermentation of biodiesel’s crude glycerol when used to formulate natural hydraulic lime mortars, as a fluid replacing the mixing water. The bioproduct was used either sonicated or non-sonicated and two volumes of mixing fluid were tested. The aim was to assess the advantages and drawbacks that could be achieved with a waste-based bioproduct, instead of petrochemical-based additions. The investigation revealed a positive effect on workability, producing mortars with a lower mixing fluid content, improving the mechanical performance. Finally, the bioproducts reduced the mortar water absorption by gravity and capillary.S

Impact of a Pretreatment Step on the Acidogenic Fermentation of Spent Coffee Grounds

This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (LA/P/0006/2020), Paulo C. Lemos acknowledges the support by FCT/MCTES for contract IF/01054/2014/CP1224/CT0005.Acidogenic fermentation (AF) is often applied to wastes to produce short-chain organic acids (SCOAs)—molecules with applications in many industries. Spent coffee grounds (SCGs) are a residue from the coffee industry that is rich in carbohydrates, having the potential to be valorized by this process. However, given the recalcitrant nature of this waste, the addition of a pretreatment step can significantly improve AF. In this work, several pretreatment strategies were applied to SCGs (acidic hydrolysis, basic hydrolysis, hydrothermal, microwave, ultrasounds, and supercritical CO2 extraction), evaluated in terms of sugar and inhibitors release, and used in AF. Despite the low yields of sugar extracted, almost all pretreatments increased SCOAs production. Milder extraction conditions also resulted in lower concentrations of inhibitory compounds and, consequently, in a higher concentration of SCOAs. The best results were obtained with acidic hydrolysis of 5%, leading to a production of 1.33 gSCOAs/L, an increase of 185% compared with untreated SCGs.publishersversionpublishe

Metabolic modelling of polyhydroxyalkanoate copolymers production by mixed microbial cultures

Background: This paper presents a metabolic model describing the production of polyhydroxyalkanoate (PHA) copolymers in mixed microbial cultures, using mixtures of acetic and propionic acid as carbon source material. Material and energetic balances were established on the basis of previously elucidated metabolic pathways. Equations were derived for the theoretical yields for cell growth and PHA production on mixtures of acetic and propionic acid as functions of the oxidative phosphorylation efficiency, P/O ratio. The oxidative phosphorylation efficiency was estimated from rate measurements, which in turn allowed the estimation of the theoretical yield coefficients. Results: The model was validated with experimental data collected in a sequencing batch reactor (SBR) operated under varying feeding conditions: feeding of acetic and propionic acid separately (control experiments), and the feeding of acetic and propionic acid simultaneously. Two different feast and famine culture enrichment strategies were studied: (i) either with acetate or (ii) with propionate as carbon source material. Metabolic flux analysis (MFA) was performed for the different feeding conditions and culture enrichment strategies. Flux balance analysis (FBA) was used to calculate optimal feeding scenarios for high quality PHA polymers production, where it was found that a suitable polymer would be obtained when acetate is fed in excess and the feeding rate of propionate is limited to ∼0.17 C-mol/ (C-mol.h). The results were compared with published pure culture metabolic studies. Conclusion: Acetate was more conducive toward the enrichment of a microbial culture with higher PHA storage fluxes and yields as compared to propionate. The P/O ratio was not only influenced by the selected microbial culture, but also by the carbon substrate fed to each culture, where higher P/O ratio values were consistently observed for acetate than propionate. MFA studies suggest that when mixtures of acetate and propionate are fed to the cultures, the catabolic activity is primarily guaranteed through acetate uptake, and the characteristic P/O ratio of acetate prevails over that of propionate. This study suggests that the PHA production process by mixed microbial cultures has the potential to be comparable or even more favourable than pure cultures.publishersversionpublishe

Effect of surface biotreatments on construction materials

STSM Grant from the COST Action CA15202. Spanish Ministry of Economy - project BIA2017-83526-R. project DB-Heritage – Database of building materials with historical and heritage interest (PTDC/EPH-PAT/4684/2014). IF/01054/2014/CP1224/CT0005. FCT/MCTES (UID/QUI/50006/2019; UID/Multi/04378/2019). POCI-01-0145-FEDER-007728. Nídia Almeida is supported by the Radiation Biology and Biophysics Doctoral Training Programme (RaBBiT-PD/00193/2012; UCIBIO-UID/Multi/04378/2019 and by a PhD fellowship from FCT/MCTES (PD/BD/106034/2015).Surface treatment technology is instrumental to construction material conservation and more specifically to preventing decay and improving durability. Surface treatments help protect and consolidate the built heritage against material damage, reducing repair and replacement costs. This study assessed the effect of two eco-friendly healing agents, one generated by iron-enriched Escherichia coli and the other by mixed microbial cultures that metabolise glycerol, a biodiesel processing by-product, to produce polyhydroxyalkanoates. Healing was monitored by measuring the water drop absorption rate in cement mortar, air lime mortar, ceramic brick, limestone, adobe and compressed earth block. The agents tested lengthened water absorption times in all the materials studied, confirming their efficacy as external repair treatments for construction materials.authorsversionpublishe

Biodegradable Polymers on Cementitious Materials

[EN] Nowadays the sustainability and safety requirements of structures inspire the study of new self-healing materials and preventive repair methods on cementitious elements. To achieve this undertaking, this research replaces widely employed synthetic polymers by biodegradable ones as consolidants and water-repellents, and assesses the protection and consolidation effect of biopolymers (obtained by using waste biomass of mixed microbial cultures from polyhydroxyalkanoates production processes) as eco-friendly healing agents by analysing the water absorption of two kind of materials. The first group of samples are cement mortar specimens whose external surface has been treated with biopolymer products and subsequently evaluated by water drop absorption test. The second group of samples are cement mortar specimens formulated with biopolymer products included in its mixing water and later the waterproofing efficiency is analysed by capillary water absorption tests. The water absorption behaviour of both kind of samples shows a potential improvement of cementitious elements durability, since water absorption results have decreased for treated samples in comparison with untreated one

Enzymatic Potential of Filamentous Fungi as a Biological Pretreatment for Acidogenic Fermentation of Coffee Waste

This work was developed within the scope of the project CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020), and the Associate Laboratory for Green Chemistry-LAQV (UIDB/50006/2020 and UIDP/50006/2020). It was financed by national funds through the FCT/MCTES (PIDDAC) and, when appropriate, co-financed by FEDER under the PT2020 Partnership Agreement. Paulo C. Lemos acknowledges the support of FCT/MCTES for contract IF/01054/2014/CP1224/CT0005 and Joana Pereira thanks FCT/MCTES for her Ph.D. grant SFRH/BD/130003/2017.Spent coffee grounds (SCGs) are a promising substrate that can be valorized by biotechnological processes, such as for short-chain organic acid (SCOA) production, but their complex structure implies the application of a pretreatment step to increase their biodegradability. Physicochemical pretreatments are widely studied but have multiple drawbacks. An alternative is the application of biological pretreatments that include using fungi Trametes versicolor and Paecilomyces variotii that naturally can degrade complex substrates such as SCGs. This study intended to compare acidic and basic hydrolysis and supercritical CO 2 extraction with the application of these fungi. The highest concentration of SCOAs, 2.52 gCOD/L, was achieved after the acidification of SCGs pretreated with acid hydrolysis, but a very similar result, 2.44 gCOD/L, was obtained after submerged fermentation of SCGs by T. versicolor. This pretreatment also resulted in the best acidification degree, 48%, a very promising result compared to the 13% obtained with the control, untreated SCGs, highlighting the potential of biological pretreatments.publishersversionpublishe