135,096 research outputs found

    Treatment of saline wastewater amended with endocrine disruptors by aerobic granular sludge: assessing performance and microbial community dynamics

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    An aerobic granular sludge (AGS) sequencing batch reactor (SBR) adapted to salinity (12gL-1 NaCl) was operated under alternating anaerobic-aerobic conditions for the treatment of synthetic saline wastewater containing endocrine-disrupting chemicals (EDCs), namely 17estradiol (E2), 17ethinylestradiol (EE2) and bisphenol-A (BPA). The SBR was intermittently fed with the EDCs at 2mgL-1 of each compound. E2 was completely biodegraded, with 60% to 80% removal attained anaerobically and the remaining quickly consumed under aeration. EE2 was sorbed onto the granular sludge biomass in the anaerobic period, but it was desorbed in subsequent cycles even when the compound was not supplied to the reactor. BPA removal was poor but improved after bioaugmentation with an EDCs degrading bacteria. EDCs shock loads did not significantly affect the COD removal nor the activity of ammonium- and nitrite-oxidizing bacteria (AOB and NOB, respectively). In contrast, the activity of phosphate-accumulating organisms (PAOs) was affected, implying a decrease in P removal within the aerobic phase. AGS core microbiome grouped most bacteria belonging to the phylum Proteobacteria, followed by Bacteroidetes. The microbial profile showed that the introduction of the EDCs mixture increased the relative abundance of Chryseobacterium and Flavobacterium. AOB and NOB species were detected in the AGS biomass, with the latter showing lower relative abundance. Different PAOs, such as Rhodocyclus, Tetrasphaera and Gemmatimonas, were also part of the microbial community, but the addition of EDCs decreased significantly the relative abundance of Rhodocyclus. High microbial diversity was sustained over reactor operation, with the main bacterial groups responsible for nutrients and EDCs removal preserved in the AGS system. The results pointed to the maintenance of a core microbiome over reactor operation that may be related to the stability of the AGS process during EDCs loading.This study was supported in part by the Coordena√ß√£o de Aperfei√ßoamento de Pessoal de N√≠vel Superior (CAPES/Brasil) ‚Äď Finance Code 001 and the other part was financed by National Funds from Funda√ß√£o para a Ci√™ncia e a Tecnologia (FCT/Portugal) - through the project AGeNT - PTDC/BTA-BTA/31264/2017 (POCI-01-0145-FEDER 031264)and the project CBQF - UID/Multi/50016/2019info:eu-repo/semantics/publishedVersio

    Synthetic biology approaches to engineer polyphenols microbial cell factories

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    Polyphenols are secondary metabolites isolated from plants that can be divided into flavonoids, stilbenoids, curcuminoids, coumarins, polyphenolic amides and lignans. These exhibit diverse biological and potential therapeutic activities including antioxidant, anti-inflammatory and anticancer, among others. Despite all this potential, extracting polyphenols from plants is not straightforward given the low yields of the process. The extracted amounts are not sufficient to respond to the increasing demand for polyphenols, the process is expensive and unfriendly for the environment. Hence, developing microbial cell factories to effectively produce polyphenols arises as an attractive way to address the mentioned limitations and produce high amounts of these compounds. Advances in the metabolic engineering and synthetic biology fields have been key in the design of efficient and robust microbial cell factories, mainly due to the development of proper molecular biology tools, as well as to the unravelling of new enzymes in plants or other organisms to better engineer such heterologous pathways. Several hosts have been explored as potential polyphenols microbial cell factories. However, there is still a long way before this production at an industrial scale can become a reality. The perspectives and current challenges resulting from these developments will be discussed.info:eu-repo/semantics/publishedVersio

    Encapsulated bacteriophages for pre-slaughter interventions to reduce Shiga toxin-producing E. coli (STEC) in ruminants

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    Fundação para a Ciência e Tecnologia (FCT), COMPETE 2020, NORTE 2020info:eu-repo/semantics/publishedVersio

    Optical characterization of a funnel solar cooker with azimuthal sun tracking through ray-tracing simulation

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    Funnel type solar cookers are simple and effective. Most of them rely on a multifaceted reflector to concentrate solar radiation on a cooking pot that is placed inside a transparent enclosure to create a greenhouse effect. The analysis of the resulting optical system is a complex task, as multiple reflections occur. The overall performance of funnel solar cookers is strongly affected by their optical efficiency. There is a lack of information in academic literature about this important research topic. This work aims to fill this gap presenting an optical performance analysis of a funnel solar cooker with only azimuthal sun tracking. Open-source numerical ray-tracing software Soltrace is used to investigate relevant characteristics such as the intercept factor, optical efficiency, dependency on incidence angle, performance of each reflecting surface and irradiation density flux distribution on different surfaces of the cooking pot. Some important results for beam radiation at normal incidence are the intercept factor, determined to be 0.664, and the optical efficiency with realistic optical properties, that turned out to be 0.370. When the incidence of solar beam radiation is not normal, optical efficiency remains above 90% of its normal incidence value, if the alignment errors are less than 10 degrees.info:eu-repo/semantics/publishedVersio

    Accurate estimation of grapevine bunch weight using image analysis: a case study with two Portuguese cultivars

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    Vineyard yield estimation can bring several benefits to all the grape and wine production chain. Among several methods the ones based on estimation of yield components are the most used at farm level. However, as they are manual, destructive and very time-consuming, there is a strong demand to replace them with low-cost and reliable automated methods. Recent advances in machine vision have provided accurate tools for bunch and/or berry recognition. However, converting the visible bunch area on the images into bunch mass is still a big challenge. In the frame of the EU VINBOT research project (www.vinbot.eu), an experiment was set up using the cultivars Viosinho (white; 100 bunches) and ‚ÄėTrincadeira‚Äô (red, 48 bunches) to study the relationships between the projected bunch area (Ba) on the 2D images and the corresponding bunch weight (Bw) measured at harvest. In the laboratory, bunches were submitted to image acquisition using a compact RGB camera. Then each bunch was assessed to obtain the following morphological attributes: Bw, bunch volume (Bv), berry number (BE#) and weight (BEw) and rachis length (Rl). Bunch compactness (Bc) was calculated as the ratio between BE# and Rl, while the Ba was computed using ImageJ¬ģ software. Correlation analysis shows that most part of these variables are significantly and positively correlated with Bw. However, as not all variables are easy to obtain by automated image analysis, some were excluded and a forward stepwise regression between Bw (dependent variable) and the variables BE#, Ba, Bv and Bc (independent variables) was performed. The final models obtained explained a very high proportion of bunch weight variability (R2=0.98 and 0.99 for ‚ÄėViosinho‚Äô and ‚ÄėTrincadeira‚Äô, respectively) with a very small error. These results indicate that grapevine bunch weight can be estimated with high accuracy from 2D images using explanatory variables derived from bunch morphological attributesinfo:eu-repo/semantics/publishedVersio

    Fluctuating asymmetry

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    Growth and bioactivity of two chlorophyte (Chlorella and Scenedesmus) strains co-cultured outdoors in two different thin-layer units using municipal wastewater as a nutrient source

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    The application of microalgae in wastewater treatment has recently been at the forefront of interest due to the increasing concern about environmental protection and economic sustainability. This work aimed to study two chlorophyte species, Chlorella vulgaris and Scenedesmus acutus, co-cultured outdoors in centrate of municipal wastewater as a nutrient source. Two different thin-layer units were used in these trials & mdash; thin-layer cascade (TLC) and thin-layer raceway pond (TL-RWP), suitable for this purpose due to their high biomass productivity and better culture transparency when using muddy wastewater. The units were operated in batch, and subsequently in semi-continuous growth regime & mdash; and monitored in terms of photosynthetic performance, growth, nutrient removal rate, and bioactivity. The results showed that the co-cultures grew well in the centrate, achieving the maximum biomass densities of 1.3 and 2.1 g DW L-1 in TLC and TL-RWP, respectively, by the end of the batch regime and 1.9 and 2.0 g DW L-1 by the end of the semi-continuous regime. Although TL-RWP grown cultures showed faster growth, the TLC-one revealed better nutrient removal efficiencies batch wise than the culture grown in TL-RWP & mdash; removing up to 48% of total nitrogen and 43% of total phosphorus. Conversely, the latter was more efficient under the semi-continuous regime (54% and 42% consumption of total nitrogen and phosphorus, respectively). In the harvested biomass, an important antimicrobial activity (specifically antifungal) was detected. In this sense, the in-vitro growth of the oomycete Pythium ultimum was inhibited by up to 45% with regard to the control. However, no biostimulating activity was observed. The present findings confirm the possibility of using these two species for biomass production in municipal wastewater centrate using highly productive thin-layer systems. This technology can be a valuable contribution to circular economy since the produced biomass can be re-applied for agricultural purposes.SFRH/BD/129952/2017; UIDB/00511/2020; DINOSSAUR-PTDC/BBB-EBB/1374/2014-POCI-01-0145-FEDER-016640;info:eu-repo/semantics/publishedVersio

    Factors influencing firm propensity for ISO 9001 withdrawal: Evidence on decertification tendency and antecedents

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    There are approximately 1,000,000 ISO 9001 certified companies worldwide. Every year, one third of these companies must decide whether to renew, or not, their certificate. The number of companies that abandon or lose the certificate has been growing and reached an average of 60,000 per year. Considering that there is currently no theory or model to explain this propensity of firms to decertify (18%), the aim of this study is to identify the underlying factors influencing firm propensity for ISO 9001 withdrawal and to analyse the relationships between these factors. In order to achieve these aims, the research develops a structural equation model (PLS-SEM), from extant literature, and estimates the model with survey data from a sample of 221 ISO 9001 certified companies. Results show that the main antecedents to decertification propensity are barriers to the initial certification, (absence of) external certification benefits, decertification motivations, and expected performance after decertification. This is the first study to address decertification from a systemic and comprehensive perspective and to present a structural equation model of the phenomenon. The study makes an integrated contribution to explain decertification propensity with the help of novel research variables. Results suggest several contributions to theory, and practice, and contribute to clarify a major contradiction in the field.UIDB/04007/2020info:eu-repo/semantics/publishedVersio

    Determinants of expected performance after ISO 9001 certification withdrawal

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    ISO 9001 certification impact on firm performance has been extensively researched. However, despite the high number of firms withdrawing from this certification, the impact of decertification has not received much research attention. This study contributes to filling this gap by analysing the factors that influence the expected performance after decertification (EPAD). The study reviews relevant literature and develops a structural equation model (PLS-SEM) with data from 231 certified organisations. Results reveal that the main factors influencing EPAD are external decertification motivations and internal certification benefits. Internal benefits have a U-shaped relationship with EPAD and external decertification motivations a positive linear relationship. Results show also a negative direct impact of external benefits on EPAD, which is counterbalanced and cancelled by a positive indirect impact from the same variable. Certification barriers and internal decertification motivations have no significant effect. This study is the first to identify and analyse the factors affecting EPAD and, as such, the study findings constitute innovative contributions to the literature. These findings have theoretical and practical implications for (1) the estimation of EPAD, (2) the decision to renew (or not) the certificate, and (3) further suggest that EPAD is a better predictor of decertification than past certification benefits.info:eu-repo/semantics/publishedVersio

    Resource design in federated sensor networks using RELOAD/CoAP overlay architectures

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    Sensor networks can be federated for wide-area geographical coverage using RELOAD/CoAP architectures. In this case, proxy nodes of constrained environments form a P2P overlay to announce device resources or sensor data. Although this is a standard-based solution, consistency problems may arise because P2P resources (data objects stored at the overlay network) may end up including similar device resource entries. This is so because device resource entries, or sensor data, can be announced under different P2P resource umbrellas, meaning that any update to them will require changing multiple P2P resources. Here in this article, a multi-layer approach is proposed to solve this issue, allowing for a more efficient storage/retrieval of IoT data. Information at the overlay network is kept consistent, although additional P2P anonymous resources must be created. A mathematical model is proposed for the planning of such multi-layer organization of P2P resources, together with a heuristic algorithm. A required overlay service is also discussed.info:eu-repo/semantics/publishedVersio
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