Repositório Institucional da Universidade de Aveiro
Not a member yet
41903 research outputs found
Sort by
Characterization of cholinesterases in Chironomus riparius and the effects of three herbicides on chlorpyrifos toxicity
No full textIn this study, the toxicities of four pesticides (the herbicides atrazine, terbuthylazine, metolachlor and the insecticide chlorpyrifos) previously detected in the Alqueva reservoir/dam (south of Portugal) were evaluated individually and in binary combinations of the herbicides and the insecticide using fourth-instar larvae of the aquatic midge Chironomus riparius.Chlorpyrifos induced toxicity to midges in all the 48h toxicity bioassays performed. The swimming behaviour of the larvae was impaired, with EC50values ranging from 0.15 to 0.17μg/L. However, neither s-triazine (atrazine and terbuthylazine) herbicides nor metolachlor alone at concentrations up to 200μg/L caused significant toxicity to C. riparius. When combined with both s-triazine herbicides, chlorpyrifos toxicity was enhanced by approximately 2-fold when tested in a binary mixture experimental setup, at the 50% effective concentration levels.To evaluate how chlorpyrifos toxicity was being increased, the cholinesterases (ChE) were characterized biochemically using different substrates and selective inhibitors. The results obtained suggested that the main enzyme present in this species is acetylcholinesterase (AChE) and therefore it was assayed upon C. riparius exposures to all pesticides individually and as binary mixtures. Although atrazine and terbuthylazine are not effective inhibitors of AChE, the potentiation of chlorpyrifos toxicity by the two s-triazine herbicides was associated with a potentiation in the inhibition of AChE in midges; both s-triazine herbicides at 200. μg/L increased the inhibition of the AChE activity by 7 and 8-fold, respectively. A strong correlation was observed between swimming behaviour disturbances of larvae and the inhibition of the AChE activity. In contrast, metolachlor did not affect chlorpyrifos toxicity at any of the concentrations tested. Therefore, the herbicides atrazine and terbuthylazine can act as synergists in the presence of chlorpyrifos, increasing the toxicity and consequently underestimating risk based on single chemical levels
Cationic galactoporphyrin photosensitisers against UV-B resistant bacteria: oxidation of lipids and proteins by 1O2
No full textAntimicrobial photodynamic inactivation is becoming a promising alternative to control microbial pathogens. The combination of positively charged groups and carbohydrate moieties with porphyrin derivatives results in increased cell recognition and water solubility, which improves cell membrane penetration. However, the nature of the oxidative damage and the cellular targets of photodamage are still not clearly identified. This work reports the use of four cationic galactoporphyrins as PSs against two environmental bacteria, Micrococcus sp. and Pseudomonas sp., resistant to oxidative stress induced by UV-B exposure. The effect of (1)O(2) generated during the PDI assays on oxidation of cellular lipids and proteins was also assessed. PDI experiments with Micrococcus sp. and Pseudomonas sp. were conducted with 0.5 and 5.0 μmol L(-1) of photosensitiser, respectively, under white light at a fluence rate of 150 mW cm(-2) during 15 min. The most effective compounds against Gram (+) bacteria were PSs 3a, 5a and 6a leading to ≈8.0 log of photoinactivation while PSs 3a and 6a caused the highest inactivation (≈6.0 log and 5.3 log) of the Gram (-) strain. The adsorption to cellular material and (1)O(2) generation capacity of the PS molecule were determinant factors for these inactivation profiles. The occurrence of protein carbonylation and lipid peroxidation supports the hypothesis that antibacterial PDI is triggered by damage of external cell structures such as the cell wall and membrane
Biogeography and biodiscovery hotspots of macroalgal marine natural products
No full textThis review covers the literature published for marine natural products isolated from macroalgae and addresses the taxonomic details of source organisms, the chemical types of isolated compounds and the location of sampling sites. The emphasis of this review is on the identification of the most bioprospected taxa and regions, as well as on how these trends have shifted over time
Burial grounds' impact on groundwater and public health: an overview
No full textThe most common practice for disposal of dead bodies is inhumation in soil, which favours interactions with the surrounding environment and returns nutrients to the life cycle. However, when the burial ground is located where hydrogeological, geological and climatic conditions are not favourable to the process, contamination of soils and groundwater may occur, and decomposition may be inhibited, leading to social, economic and political problems. The most critical parameters when assessing the pollution potential of a burial ground are inhumation depth, geological formation, depth of the water table, density of inhumations, soil type and climate. Considering that, this paper presents an overview of the potential threat that cemeteries can pose, analysing and discussing the influence of the main variables causing environmental impacts and public health risks
Halophyte plant colonization as a driver of the composition of bacterial communities in salt marshes chronically exposed to oil hydrocarbons
No full textIn this study, two molecular techniques [denaturing gradient gel electrophoresis (DGGE) and barcoded pyrosequencing] were used to evaluate the composition of bacterial communities in salt marsh microhabitats [bulk sediment and sediment surrounding the roots (rhizosphere) of Halimione portulacoides and Sarcocornia perennis ssp. perennis] that have been differentially affected by oil hydrocarbon (OH) pollution. Both DGGE and pyrosequencing revealed that bacterial composition is structured by microhabitat. Rhizosphere sediment from both plant species revealed enrichment of operational taxonomic units closely related to Acidimicrobiales, Myxococcales and Sphingomonadales. The in silico metagenome analyses suggest that homologous genes related to OH degradation appeared to be more frequent in both plant rhizospheres than in bulk sediment. In summary, this study suggests that halophyte plant colonization is an important driver of hydrocarbonoclastic bacterial community composition in estuarine environments, which can be exploited for in situ phytoremediation of OH in salt marsh environments
Changes of chemical chronic toxicity to Daphnia magna under different food regimes
No full textIn aquatic ecosystems several stressors may act together and affect the life traits of organisms. Pesticide runoffs are usually associated with high inputs of organic matter and depletion of oxygen in aquatic systems. This study aimed at combining anthropogenic stress (chemicals) and natural stress (food availability) and evaluates their joint effect to the life traits of Daphnia magna. The neonicotinoid insecticide imidacloprid and the heavy metal nickel chloride were used and a 21. d chronic test was carried out to obtain reproduction and growth data. The conceptual model Independent action, usually used for assessing response patterns in chemical mixtures, was used for data interpretation. Results showed an increase in the reproduction and growth pattern of D. magna as food levels increased. Both chemicals significantly impaired the reproduction as well as the somatic growth of the organism while the same happened with food concentrations lower than 3??105cells/mL. It was also observed that food availability did not change the toxicity of imidacloprid and nickel chloride when food levels were higher than 3??105cells/mL. When combined with low food levels, imidacloprid showed a slight increase in toxicity, showing that daphnids become more sensitive with reduced food availability, however in a non-significant way. However, toxicity of nickel appeared to be independent of the food level. Both chemicals induced mortality to the organisms exposed in the absence of food only at the end of the test
Acute toxicity of tralopyril, capsaicin and triphenylborane pyridine to marine invertebrates
No full textA need for environmentally acceptable alternative antifouling (AF) biocides has arisen through restrictions in the use of many common biocides in the European Union through the Biocidal Product Regulation (Regulation EU No. 528/2012). Three such alternatives are triphenylborane pyridine (TPBP), tralopyril and capsaicin. This study aims at extending the available information on the toxicity of these three emerging AF biocides to key marine invertebrates. Here we investigate the toxicity of tralopyril and capsaicin to the early life stages of the mussel Mytilus galloprovincialis and the sea urchin Paracentrotus lividus and also of tralopyril, capsaicin and TPBP to the early life stages of the copepod Tisbe battagliai. The EC50 that causes abnormal development of mussel's D-veliger larvae and impairs the growth of sea urchin pluteus larvae are respectively 3.1 and 3.0 μg/L for tralopyril and 3,868 and 5,248 μg/L for capsaicin. Regarding the copepod T. battagliai, the LC50 was 0.9 μg/L for tralopyril, 1,252 μg/L for capsaicin and 14 μg/L for TPBP. The results obtained for the three substances are compared to a reference AF biocide, tributyltin (TBT), and their ecological risk evaluated. These compounds pose a lower environmental risk than TBT but still, our results suggest that tralopyril and TPBP may represent a considerable threat to the ecosystems
A framework for modelling the transport and deposition of eroded particles towards water systems in a life cycle inventory
No full textPurpose
Topsoil erosion due to land use has been characterised as one of the most damaging problems from the perspective of soil-resource depletion, changes in soil fertility and net soil productivity and damage to aquatic ecosystems. On-site environmental damage to topsoil by water erosion has begun to be considered in Life Cycle Assessment (LCA) within the context of ecosystem services. However, a framework for modelling soil erosion by water, addressing off-site deposition in surface water systems, to support life cycle inventory (LCI) modelling is still lacking. The objectives of this paper are to conduct an overview of existing methods addressing topsoil erosion issues in LCA and to develop a framework to support LCI modelling of topsoil erosion, transport and deposition in surface water systems, to establish a procedure for assessing the environmental damage from topsoil erosion on water ecosystems.
Methods
The main features of existing methods addressing topsoil erosion issues in LCA are analysed, particularly with respect to LCI and Life Cycle Impact Assessment methodologies. An overview of nine topsoil erosion models is performed to estimate topsoil erosion by water, soil particle transport through the landscape and its in-stream deposition. The type of erosion evaluated by each of the models, as well as their applicable spatial scale, level of input data requirements and operational complexity issues are considered. The WATEM-SEDEM model is proposed as the most adequate to perform LCI erosion analysis.
Results and discussion
The definition of land use type, the area of assessment, spatial location and system boundaries are the main elements discussed. Depending on the defined system boundaries and the inherent routing network of the detached soil particles to the water systems, the solving of the multifunctionality of the system assumes particular relevance. Simplifications related to the spatial variability of the input data parameters are recommended. Finally, a sensitivity analysis is recommended to evaluate the effects of the transport capacity coefficient in the LCI results.
Conclusions
The published LCA methods focus only on the changes of soil properties due to topsoil erosion by water. This study provides a simplified framework to perform an LCI of topsoil erosion by considering off-site deposition of eroded particles in surface water systems. The widespread use of the proposed framework would require the development of LCI erosion databases. The issues of topsoil erosion impact on aquatic biodiversity, including the development of characterisation factors, are now the subject of on-going research
Setup and calibration procedure for LPE PA characterization with synchronous input-output excitations
No full textModern transmitter architectures make use of
multi-input multi-output (MIMO) techniques, employing a high number of RF power amplifiers (PAs) to excite an antenna array.
The array elements are often coupled, creating an excitation at
the output of the PAs, which is dependent on the outputs of the
other elements. Therefore, in this system, the nonlinear behavior
of each PA cannot be fully described solely as a function of its
input. In order to characterize a device that will operate in this
arrangement, it is important to develop setups that are capable of
exciting the PA at the input and output, synchronously at the RF
carrier (phase control) and envelope (delay control) levels, with
correlated or independent amplitude and phase modulations. In
this paper we propose a setup for this type of characterization
and show how it can be calibrated to correct the frequency
response of the observation paths and the excitation paths in a
simple way using broadband modulated signals, covering the full
measurement bandwidth
Estudo Experimental de Tecnologias de Segurança em Redes IP
No full textMestrado em Engenharia Electrónica e TelecomunicaçõesA maior parte dos protocolos actualmente utilizados nas redes IP, pouco
mudaram desde o início da Internet. Em grande parte dos casos a sua
concepção não teve em conta os aspectos de segurança. Isto pode levar à
perda, roubo, corrupção ou má utilização da informação, podendo
inclusivamente colocar em risco o funcionamento da rede. A insegurança de
um é, na realidade, a insegurança de todos. Por isso a utilização de
encriptação para garantir a privacidade dos dados, de mecanismos de
autenticação robustos, e de mecanismos que garantam a integridade da
informação são obrigatórios numa rede que se pretenda segura.
Esta dissertação tem como objectivo abordar a temática da segurança em
redes IP. São estudadas as principais ameaças e tipos de ataques à
segurança de uma rede, os serviços e tecnologias de segurança que podem
ser usados na sua protecção, é analisado o funcionamento de vários
protocolos de segurança utilizados nas redes IP e são discutidas soluções
que visam garantir uma rede segura. Esta dissertação recorre de forma
exaustiva à análise experimental com o objectivo de: (i) melhor compreender
e verificar o funcionamento de cada protocolo, (ii) estudar as suas
vulnerabilidades e (iii) implementar os ataques possíveis.
Em particular, nesta dissertação, é feito um estudo aprofundado sobre: (1)
os protocolos utilizados nos acessos remotos (PAP, SPAP, CHAP, MSCHAPv1,
MS-CHAPv2 e EAP) e suas vulnerabilidades; (2) a arquitectura
AAA, através do serviço RADIUS; (3) a utilização do IPSec para garantir os
serviços de autenticação, integridade e confidencialidade na troca de
informação; (4) a utilização de firewalls em routers, recorrendo a listas de
acesso estáticas, dinâmicas e reflexivas; (5) as implicações dos protocolos
de encaminhamento (RIPv1, RIPv2, IGRP, EIGRP e OSPF) na segurança
da rede. Relativamente ao encaminhamento, para lá dos aspectos de
segurança, é também efectuado um estudo aprofundado sobre aspectos
específicos de funcionamento e de desempenho dos protocolos de
encaminhamento.Most IP protocols have barely changed since the beginning of the Internet. In
most cases their conception didn’t take into account security aspects. This
fact could lead to lost, theft, corruption or misuse of the information and in
some cases disrupt network services. The insecurity of one protocol is, in
fact, the insecurity of all. That’s why encryption, authentication and integrity
services are essential to network security.
This master thesis focuses on IP network security. A study is made of the
principal threats and types of attacks to network security, security services
and technologies that can be used in network protection and IP security and
routing protocols. Solutions to network security are also discussed. This
thesis presents an exhaustive experimental analysis with the following
objectives: (i) better understanding of the protocol operations; (ii) practical
study of network weaknesses and vulnerabilities; (iii) execute possible
attacks.
This thesis focuses in particular: (1) remote access protocols (PAP, SPAP,
CHAP, MS-CHAPv1, MS-CHAPv2 and EAP) and their vulnerabilities; (2)
AAA architecture through RADIUS protocol; (3) IPSec authentication,
confidentiality and integrity services; (4) configuring a router to became a
firewall through the use of Cisco static, dynamic and reflexive access lists;
(5) IP routing protocols (RIPv1, RIPv2, IGRP, EIGRP and OSPF) implication
in network security. Beyond the aspects of network security it’s also
presented a detailed study of specific operation and performance aspects of
this routing protocols