Repositório Institucional da Universidade de Aveiro
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Cryogenic nanothermometer based on the MIL-103(Tb,Eu) metal-organic framework
No full textThe microporous metal–organic framework MIL-103 doped with Tb3+ and Eu3+, formulated as [(Tb0.95Eu0.05)(btb)(H2O)]·(solv)x [H3btb = 1,3,5-tris(4-carboxyphenyl)benzene; solv = H2O, CH3OH] has been shown to be a good platform for luminescent ratiometric thermometry. Although operative over a wide range of temperatures (10–320 K), this material exhibits, in the cryogenic range (<100 K), one of the best performances of metal–organic frameworks, with a relative thermal sensitivity of 2.85 % K–1 at 14 K. The material exists in the form of nanoparticles, suitable for nanothermometry applications (e.g., microfluidics). Moreover, as MIL-103 is nanoporous, its use as a multisensing platform deserves further consideration in the near future
What's wrong with Lagergreen pseudo first order model for adsorption kinetics?
No full textAdsorption processes can be modeled on the basis of phenomenological principles using conservation,
equilibrium and transport kinetics equations. However many times an empirical approach is followed
using pseudo first order and pseudo second order models to describe adsorption kinetics. In this short
communication we discuss the use of Lagergreen model (pseudo first order kinetic model) and compare
it with the linear driving force model of Glueckauf for a linear adsorption equilibrium isotherm. A relation
between the kinetic constants of both models is derived, being possible to disclose they exhibit very dis
tinct dependency with temperature whatever the porous structure of the adsorbent particle. In conclu
sion, care must be taken when using the short cut approach of pseudo first order expressions, taking
into account their theoretically inconsistent trends
Vigilantism, masculinity and star image in Hollywood cinema
No full textMestrado em Estudos InglesesResumos indisponívei
Distributed Linear Precoding and User Selection in Coordinated Multicell Systems
No full textIn this paper, we tackle the problem of semidistributed user selection with distributed linear precoding for sum-rate maximization in multiuser multicell systems. A set of adjacent base stations (BSs) forms a cluster to perform coordinated transmission to cell-edge users, and coordination is carried out through a central processing unit (CU). However, the message exchange between BSs and the CU is limited to scheduling control signaling, and no user data or channel state information (CSI) exchange is allowed. In the considered multicell coordinated approach, each BS has its own set of cell-edge users and transmits only to one intended user while interference to nonintended users at other BSs is suppressed by signal steering (precoding). We use two distributed linear precoding schemes, namely, distributed zero forcing and distributed virtual signal-to-interference-plus-noise ratio (DVSINR). Considering multiple users per cell and the backhaul limitations, the BSs rely on local CSI to solve the user selection problem. First, we investigate how the signal-to-noise ratio regime and the number of antennas at the BSs impact the effective channel gain (the magnitude of the channels after precoding) and its relationship with multiuser diversity. Considering that user selection must be based on the type of implemented precoding, we develop metrics of compatibility (estimations of the effective channel gains) that can be computed from local CSI at each BS and reported to the CU for scheduling decisions. Based on such metrics, we design user selection algorithms that can find a set of users that potentially maximizes the sum rate. Numerical results show the effectiveness of the proposed metrics and algorithms for different configurations of users and antennas at the BSs
A adaptação de Henry James ao cinema: o caso de The Portrait of a Lady
No full textMestrado em Estudos InglesesResumos indisponívei
Comparative environmental performance of three different annual energy crops for biogas production in Northern Italy
No full textBioenergy is becoming increasingly important for agriculture. However, the use of first generation crops for biofuels and bioenergy production is controversial due to their competition with food and feed. The cultivation of three different energy crops-wheat, maize and triticale-for biomass in order to produce biogas in Lombardy, in the Po Valley (Italy), was evaluated in this study to quantify their environmental profiles and identify the best biomass source from an environmental perspective. The choice of these cropping systems was based on the fact that they are well-known and extensively cultivated for energy purposes in Italy. The standard framework of the Life Cycle Assessment (LCA) was followed in this study and detailed inventories for these crops were designed. The environmental profile was analysed in terms of abiotic depletion, acidification, eutrophication, global warming, ozone layer depletion, photochemical oxidants formation, human toxicity and ecotoxicity. In addition, an energy analysis was performed using the cumulative energy demand method. According to the results, the selection of the best biomass source depends on several factors such as the functional unit and biomass yield. Therefore, a sensitivity assessment was done in order to identify these differences. Moreover, the most critical processes throughout the life cycle of the cropping systems were identified and improvement alternatives were proposed, specifically for the mineral fertilization (one of the most important hot spots). Thus, different scenarios built on alternative nitrogen based fertilizers were assessed in detail and discussed, resulting in the identification that the use of calcium ammonium nitrate instead of urea should improve the environmental profile regardless of the energy crop. Finally, the combination of triticale or wheat with maize classes 300, 400 and 500 in rotation systems was done in order to achieve similar biomass yields, per ha, to the maize classes 600 and 700, which were also evaluated. The best results were obtained for maize classes 600 and 700 regardless of the functional unit considered in all the categories assessed except in GWP, where triticale with maize 400 and with maize 500 were the best options
Biochemical and standard toxic effects of acetaminophen on the macrophyte species Lemna minor and Lemna gibba
No full textAcetaminophen is globally one of the most prescribed drugs due to its antipyretic and analgesic properties. However, it is highly toxic when the dosage surpasses the detoxification capability of an exposed organism, with involvement of an already described oxidative stress pathway. To address the issue of the ecotoxicity of acetaminophen, we performed acute exposures of two aquatic plant species, Lemna gibba and Lemna minor, to this compound. The selected biomarkers were number of fronds, biomass, chlorophyll content, lipid peroxidation (TBARS assay), and proline content. Our results showed marked differences between the two species. Acetaminophen caused a significant decrease in the number of fronds (EC50 = 446.6 mg/L), and the establishment of a dose-dependent peroxidative damage in L. minor, but not in L. gibba. No effects were reported in both species for the indicative parameters chlorophyll content and total biomass. However, the proline content in L. gibba was substantially reduced. The overall conclusions point to the occurrence of an oxidative stress scenario more prominent for L. minor. However, the mechanisms that allowed L. gibba to cope with acetaminophen exposure were distinct from those reported for L. minor, with the likely involvement of proline as antioxidant
Use, fate and ecological risks of antibiotics applied in tilapia cage farming in Thailand
No full textThe use, environmental fate and ecological risks of antibiotics applied in tilapia cage farming were investigated in the Tha Chin and Mun rivers in Thailand. Information on antibiotic use was collected through interviewing 29 farmers, and the concentrations of the most commonly used antibiotics, oxytetracycline (OTC) and enrofloxacin (ENR), were monitored in river water and sediment samples. Moreover, we assessed the toxicity of OTC and ENR on tropical freshwater invertebrates and performed a risk assessment for aquatic ecosystems. All interviewed tilapia farmers reported to routinely use antibiotics. Peak water concentrations for OTC and ENR were 49 and 1.6 μg/L, respectively. Antibiotics were most frequently detected in sediments with concentrations up to 6908 μg/kg d.w. for OTC, and 2339 μg/kg d.w. for ENR. The results of this study indicate insignificant short-term risks for primary producers and invertebrates, but suggest that the studied aquaculture farms constitute an important source of antibiotic pollution
Hydrocarbon contamination and plant species determine the phylogenetic and functional diversity of endophytic degrading bacteria
No full textSalt marsh sediments are sinks for various anthropogenic contaminants, giving rise to significant environmental concern. The process of salt marsh plant survival in such environment is very intriguing and at the same time poorly understood. The plant–microbe interactions may play a key role in the process of environment and in planta detoxification. In this study, a combination of culture-dependent and culture-independent molecular approaches [enrichment cultures, polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), DNA sequencing] were used to investigate the effect of petroleum hydrocarbons (PH) contamination on the structure and function [polycyclic aromatic hydrocarbon (PAH) dioxygenase genes] of endophytic bacterial communities of salt marsh plant species (Halimione portulacoides and Sarcocornia perennis) in the estuarine system Ria de Aveiro (Portugal). Pseudomonads dominated the cultivable fraction of the endophytic communities in the enrichment cultures. In a set of fifty isolates tested, nine were positive for genes encoding for PAH dioxygenases (nahAc) and four were positive for plasmid carrying genes encoding PAH degradation enzymes (nahAc). Interestingly, these plasmids were only detected in isolates from most severely PH-polluted sites. The results revealed site-specific effects on endophytic communities, related to the level of PH contamination in the sediment, and plant-species-specific ‘imprints’ in community structure and in genes encoding for PAH dioxygenases. These results suggest a potential ecological role of bacterial plant symbiosis in the process of plant colonization in urban estuarine areas exposed to PH contamination
Metal accumulation and oxidative stress responses in Ulva spp. in the presence of nocturnal pulses of metals from sediment: a field transplantation experiment under eutrophic conditions
No full textIn aquatic systems under eutrophic conditions, remobilization of metals from sediment to the overlying water may occur. Consequently, adaptive responses of local organisms could result from the accumulation of metals intermittently released from the sediment. In summer 2007, a field transplantation experiment was performed in the Óbidos lagoon (Portugal) with Ulva spp. comprising three short-term exposures (between 15:30-23:30; 23:30-07:30; 07:30-15:30) during a 24-h period. In each period, Ulva spp. was collected at a reference site located in the lower lagoon (LL) and transplanted to a eutrophic site located at the Barrosa branch (BB), characterized by moderate metal contamination. For comparison purposes, macroalgae samples were simultaneously exposed at LL under the same conditions. Both sites were surveyed in short-time scales (2-4 h) for the analysis of the variability of physical-chemical parameters in the water and metal levels in suspended particulate matter. The ratios to Al of particulate Mn, Fe, Cu and Pb increased during the period of lower water oxygenation at the eutrophic site, reaching 751 × 10-4, 0.67, 12 × 10-4, 9.9 × 10-4, respectively, confirming the release of metals from the sediment to water during the night. At the reference site, dissolved oxygen oscillated around 100%, Mn/Al ratios were considerably lower (81 × 10-4-301 × 10-4) compared to BB (234 × 10-4-790 × 10-4), and no increases of metal/Al ratios were found during the night. In general, algae uptake of Mn, Cu, Fe, Pb and Cd was significantly higher at the eutrophic site compared to the reference site. The results confirmed the potential of Ulva spp. as bioindicator of metal contamination and its capability to respond within short periods. An induction of SOD, an inhibition of CAT and the increase of LPO were recorded in Ulva spp. exposed at BB (between 23:30 and 7:30) probably as a response to the higher incorporation of Mn, Fe and Pb in combination with the lack of dissolved oxygen in the water. Current findings emphasize the importance of assessing, in eutrophic systems, the relationship between the variability of chemical conditions and its repercussions on autochthonous organisms over day-night cycles