Repositório Institucional da Universidade de Aveiro
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Assessing heavy metal pollution using Great Tits (Parus major): feathers and excrements from nestlings and adults
No full textPasserine species have been increasingly used as bioindicators of metal bioaccumulation especially by taking benefit of non-invasive procedures, such as collecting feathers and excrements. In 2009, metal (As, Cd, Cu, Hg, Ni, Pb, Se and Zn) concentrations were determined in feathers and excrements of nestling and adult female great tits (Parus major) in industrial (a paper mill) and rural sites in maritime pine forests on the west coast of Portugal. The aim of this study was to compare the levels of metals between the areas but also between sampling methods (feather vs. excrement) and age classes (nestling vs. adult). Although excrements and feathers of nestling great tits showed different concentrations, similar patterns of accumulation were detected in both study areas. There was a significantly higher concentration of mercury in the industrial area and significantly higher concentrations of arsenic in the rural area in both sample types. Metal levels in adult females had quite different results when compared to nestlings, and only nickel presented significantly higher levels near the paper mill. Since metal levels showed a consistent pattern in feathers and excrements of nestling great tits, we conclude that both represent good and non-invasive methods for the evaluation of these elements in polluted areas
Assessment of bitter taste of pharmaceuticals with multisensor system employing 3 way PLS regression
No full textThe application of the potentiometric multisensor system (electronic tongue, ET) for quantification of the bitter taste of structurally diverse active pharmaceutical ingredients (API) is reported. The measurements were performed using a set of bitter substances that had been assessed by a professional human sensory panel and the in vivo rat brief access taste aversion (BATA) model to produce bitterness intensity scores for each substance at different concentrations. The set consisted of eight substances, both inorganic and organic - azelastine, caffeine, chlorhexidine, potassium nitrate, naratriptan, paracetamol, quinine, and sumatriptan. With the aim of enhancing the response of the sensors to the studied APIs, measurements were carried out at different pH levels ranging from 2 to 10, thus promoting ionization of the compounds. This experiment yielded a 3 way data array (samples × sensors × pH levels) from which 3wayPLS regression models were constructed with both human panel and rat model reference data. These models revealed that artificial assessment of bitter taste with ET in the chosen set of API's is possible with average relative errors of 16% in terms of human panel bitterness score and 25% in terms of inhibition values from in vivo rat model data. Furthermore, these 3wayPLS models were applied for prediction of the bitterness in blind test samples of a further set of API's. The results of the prediction were compared with the inhibition values obtained from the in vivo rat model
Analysis of long-range transport of aerosols for Portugal using 3D chemical transport model and satellite measurements
No full textThe objective of this work is to assess the contribution of long-range transport of mineral dust from North Africa to the air pollution levels in Portugal based on a combination of a modelling approach and satellite observations. The Comprehensive Air Quality Model (CAMx) was applied together with the updated Dust REgional Atmospheric Model (BSC-DREAM8b) to characterise anthropogenic and natural sources of primary aerosols as well as secondary aerosols formation. The modelling results, after their validation and bias removing process, have been used in combination with aerosol measurements provided by Ozone Monitoring Instrument (OMI), using OMAERUV Level-2 v003 product, aiming to better understand the advantages and shortcomings of both, satellite and modelling aerosol data. The data analysis is presented for Portugal for July 2006 focusing on aerosol optical depth (AOD) at 500 nm and aerosol type. Based on the modelling results, the importance of the long-range transport of mineral dust was demonstrated for the simulation days, achieving a 60% contribution to AOD levels. The mineral dust is affecting atmospheric layers up to 6 km but peak concentrations are presented at layers below 2 km. The model predicts a complex mixture of different types of aerosol for the pixels classified by OMI as "mineral dust" and "sulphates". Although a good agreement between the model outputs and OMI observations has been found in terms of the spatial pattern and AOD correlation is about 0.48 for mineral dust, several problems were identified. The model is systematically underestimating the aerosol concentration at near ground level in comparison with the air quality monitoring stations, while OMI is in general overestimating AOD for the analysed period based on the comparison with AERONET data. Additionally, misclassification of mineral dust for some geographical locations and discontinuity in AOD values along the coastal line at water/land interface in the OMI data are discussed
Chemically transformed additive phases in Mg2TiO4 and MgTiO3 loaded hydrogen storage system MgH2
No full textThe present work deals with a comparative study of Mg2TiO4, MgTiO3 and titania additives incorporated
MgH2. Hydrogen storage measurements suggest that all these additives improve the hydrogen desorption/absorption
performance of MgH2. X-ray diffraction (XRD) and X ray photoelectron spectroscopy
(XPS) studies highlight that rock salt phases consisting of highly reduced Ti exist in the samples. These
results reiterate that in-situ formation of chemically reduced Ti containing active species is a critical step
in the catalysis of TiO2/Mg2TiO4/MgTiO3 additives loaded MgH2
Crystal growth of Bi2Te3 and noble cleaved (0001) surface properties
No full textA highqualityBi2Te3 crystal hasbeengrownbyBridgmanmethodwiththeuseofrotatingheat field. The
phase purityandbulkstructuralqualityofthecrystalhavebeenverified byXRDanalysisandrocking
curve observation.TheatomicallysmoothBi2Te3(0001)surfacewithanexcellentcrystallographicquality
is formedbycleavageintheair.Thechemicalandmicrostructuralpropertiesofthesurfacehavebeen
evaluatedwithRHEED,AFM,STM,SEandXPS.TheBi2Te3(0001)cleavedsurfaceisformedbyatomically
smooth terraceswiththeheightoftheelementalstepof 1.0470.1nm,asestimatedbyAFM.Thereis
no surfaceoxidationprocessdetectedoveramonthkeepingintheairatnormalconditions,asshownby
comparativecorelevelphotoelectronspectroscopy
Design advances in particulate systems for biomedical applications
No full textThe search for more efficient therapeutic strategies and diagnosis tools is a continuous challenge. Advances in understanding the biological mechanisms behind diseases and tissues regeneration have widened the field of applications of particulate systems. Particles are no more just protective systems for the encapsulated drugs, but they play an active role in the success of the therapy. Moreover, particles have been explored for innovative purposes as templates for cells growth and as diagnostic tools. Until few years ago the most relevant parameters in particles formulation were the chemistry and the size. Currently, it is known that other physical characteristics can remarkably affect the performance of particulate systems. Particles with non-conventional shapes exhibit advantages due to the increasing circulation time in blood stream, less clearance by the immune system and more efficient cell internalization and trafficking. Creation of compartments has been found useful to control drug release, to tune the transport of substances across biological barriers, to supply the target with more than one bioactive agent or even to act as theranostic systems. It is expected that such complex shaped and compartmentalized systems improve the therapeutic outcomes and also the patient's compliance, acting as advanced devices that serve for simultaneous diagnosis and treatment of the disease, combining agents of very different features, at the same time. In this review, we overview and analyse the most recent advances in particle shape and compartmentalization and applications of newly designed particulate systems in the biomedical field
Interacção de substâncias húmicas estuarinas com os iões hidrogénio, cobre(II) e chumbo(II)
No full textDoutoramento em QuímicaNeste trabalho foi estudado o comportamento ácido-base de substâncias
húmicas de águas estuarinas, bem como a sua interacção com iões de metais
vestigiários, nomeadamente os iões cobre(l1) e chumbo(ll).
As substâncias húmicas foram extraídas e isoladas da água de um estuário, por
adsorção a resina XAD-8, segundo o método adoptado pela Intemational Humic
Substances Society (IHSS). Os ácidos fúlvicos e os ácidos húmicos obtidos foram
posteriormente fraccionados segundo a carga, por eluição com solventes de pH
crescente, após a adsorção na resina X4D-8. As substâncias húmicas recolhidas foram
caracterizadas por análise elementar e espectroscopias de infravemelho e de
ressonância magnética nuclear de "C. A composição das substâncias obtidas é típica
das amostras estuarinas, verificando-se, como é usual, uma maior aromaticidade dos
ácidos húmicos relativamente aos ácidos fúlvicos. O fraccionamento segundo a carga
separa as fracções obtidas essencialmente no que respeita ao teor em grupos
carboxílicos, verificando-se que este diminui com o pH do solvente utilizado na eluição.
O grau de aromaticidade, pelo contrário, aumenta com o pH da eluição.
A quantificação e a caracterização dos grupos funcionais, muito heterogéneos,
das substâncias húmicas foi efectuada através de titulações com base, seguidas
potenciometricamente. A determinação da concentração hidrogeniónica é o passo
decisivo nos estudos de protonação e foi efectuada com o máximo rigor. Nesse sentido,
foi proposto e utilizado um método de calibração inovador, em que os parâmetros da
resposta do eléctrodo são retirados da própria titulação das substâncias húmicas.
Os parâmetros de protonação, nomeadamente as concentrações e afinidades
hidrogeniónicas, foram estimados utilizando modelos de distribuição discreta e de
distribuição contínua para as afinidades, tendo-se concluído que a heterogeneidade das
substâncias húmicas pode ser modelada satisfatoriamente dos dois modos, desde que
seja utilizado um número suficientemente elevado de parâmetros. (etc.)The aim of this work was to study the proton and metal ion interactions with
estuanne humic matter.
The humic substances were isolated from an estuanne water by adsorption onto
an XAD-8 resin, accordingly to the procedure proposed by the Intemational Humic
Substances Society. The fulvic and humic acids thus obtained were further fraccionated
on a charge base, by desorption from XAD-8 resin with solvents of sequencially higher
pH values. The substances were characterized by elemental analysis, IR and %-NMR
spectroscopies, and were found to be typical of estuanne humic matter. The carboxylic
content was higher for fulvic than for hurnic acids, and for the aromaticity the reverse
was true. The charge fraccionation separated the substances mainly for their carboxylic
content, which varied inversely with the pH of extraction.
The acid-base behaviour of the substances was studied by potentiometnc
titrations. A new method of electrode calibration was developed to determine the proton
conmtration, that withdraws the electrode parameters directly from the humic
substances titrations. The method proved to be both consistent and reliable.
Base titrations were periormed at three electrolyte concentrations, as well as
electrolyte titrations at constant pH. The dissociation of the functional groups is
enhanced when raising ionic strength values, and their heterogeneity is diminished. The
electrostatic effect was modelled using both a Donnan rnodel and a thermodynamic
double layer model. After correcting the base titrations data for this efíect, an intrinsic
distnbution for proton affinities was obtained. The estimated parameten for the
rnolecular size show that the humic molecules radius is about twice the fulvic one.
Hysteresis was observed for proton binding to the humic substances, probabiy
due to confomational changes of the particles, since revenibility of hysteresis was
dependent on ionic strength. .
The binding of copper to the hurnic and fulvic acids was studied by potentiornetric
titrations using a copper ion selective electrode. The binding of the fulvic acids was the
sarne for pH values 4, 6 and 8, but for the hurnic acids it was higher for the highest pH.
The affinity of copper(l1) was slightly stronger for phenolic than for carboxylic groups.
The cornplexation of lead with the humic substances was studied by voltarnrnetric
techniques. The experiments were perfomed at high ligandlrnetal ion ratios as usually
found in the aquatic environrnent, and so a sensitive technique such as anodic stripping
voltamrnetry was used to determine the complexing pararneters. The binding of lead to
the hurnic substances was mainly due to carboxylic goups, and was stronger for the
lowest ionic stregth. The influente of secondary phenomena, such adsorption and
surface electrode concentrations, was studied and proved to affect voltamrnetric
determinations. The conforrnation of hurnic substances particles in solution was found to
be dependent on the procedure followed for the solution preparation
Porfirinas como dienófilos em reacções de diels-alder
Full text linkA presente dissertação encontra-se dividida em três partes: uma de índole
introdutória, outra onde se apresentam e discutem os resultados obtidos e finalmente,
uma parte onde se descrevem todos os procedimentos experimentais efectuados.
Na primeira parte, de carácter geral, começamos por referir algumas
características gerais das reacções de Diels-Alder, nomeadamente ao nível da
reactividade. Devido ao papel crucial dos o-quinodimetanos no trabalho experimental
apresentado nesta dissertação, é também feita uma referência a sua importância em
reacções de Diels-Alder e a alguns dos métodos disponíveis para gerar este tipo de
intermediários. Os compostos porfírínicos ocupam, nesta dissertação, um lugar de
destaque pelo que neste capítulo também abordamos algumas características deste tipo
de compostos. Depois de referirmos algumas características gerais ao nível da sua
estrutura e reactividade, é feita também uma breve revis,ão das reacções de cicloadição
de Diels-Alder envolvendo porfírias, descritas na literatura. Por fim, referimos uma
das mais promissoras aplicações de compostos porfíícos no campo da medicina, a
Terapia Fotodinâmica do cancro, onde estes compostos são utilizados como
fotossensibilizadores.
Na segunda parte desta dissertação, descrevem-se os métodos e resultados
obtidos na síntese e a caracterização dos novos compostos porfirínicos obtidos a partir
da transformação de várias porfirinas segundo a reacção de cicloadição de Diels-Alder.
Mostra-se aqui, pela primeira vez, que o macrociclo porfirínico pode participar
como dienófilo em reacções de Diels-Alder. Foram utilizadas várias
meso-arilporfírinas, e como dienos utilizámos o o-benzoquinodimetano e dois
pirimidino-o-quinodimetanos. Esta reacção permite a formação, num só passo, de
nafto[2,3-blporfirias, clorinas e bactenoclorinas. Estes dois últimos tipos de
compostos apresentam características espectroscópicas que tornam possível o seu uso
como fotossensibilizadores de segunda geração para a Terapia Fotodinâmica do
cancro. Na Última parte são descritas pormenorizadamente todas as experiências
efectuadas e as características espectroscópicas, nomeadamente de espectcofotometria
de UV-Vis, espectrometria de massa e espectroscopia de RMN, dos compostos
sintetizados.The work presented in this thesis is based on the use of meso-arylporphyrins as
dienophiles in Diels-Alder reactions.
It has been shown that nzeso-arylporphyrins react with ortho-quinodimethanes to
give Diels-Alder adducts. The reaction of several meso-tetraarylporphyrins with
o-benzoquinodimethane, generated in situ by thermal ekation of SOz fiam
1,3-dihydrobenzo[c]thiophene-2,2-dioxide was shidied. The main products of the
reactions were identified as 2,21,26,3-tetrahydronaphtho[2,3-b]porphs(c hlorins),
21,26-dihydronaphtho[2,3-b]porphyrins and naphtho[2,3-blporphy~ins. When
meso-tetra(pentduorophenyl)porphyrjn was used as dienophile, bis-addition was also
observed and the adducts were identified as bacteriochlorins.
This study was extended to 5,15-diarylporphyrins and to other
o-quinodimethanes. Similar results were also obtained in these cases.
Considering the UV-Vis spectra of some of these new products, we can expect
that they are potential candidates to be used as photosensitiwrs in Photodynamic
Therapy of cancer.
All the synthesized compounds were characterked by nuclear magnetic
resonance, mass spectromem and UV-Vis
Tales of the grotesque and the carnivalesque: the fiction of Angela Carter and Salman Rushdie
No full textMestrado em Estudos InglesesResumos indisponívei
Joint signal alignment precoding and physical network coding for heterogeneous networks
No full textMobile traffic in cellular based networks is increasing exponentially, mainly due to the use of data intensive services like video. One effective way to cope with these demands is to reduce the cell-size by deploying small-cells along the coverage area of the current macro-cell system. The deployment of small-cells significantly improves the indoor coverage. Nevertheless, as additional spectrum licenses are difficult and expensive to acquire, it is expected that the macro and small-cells will coexist under the same spectrum. The coexistence of the two systems results in cross-tier/inter-system interference. In this context, we consider the application of joint signal alignment (SA) and physical network coding (PNC) for the uplink of heterogeneous networks, in order to cancel the interference generated from small-cells at the macro-cell user terminal. The joint design of SA and PNC allows to serve more users than the case where only PNC or interference alignment (IA) is employed individually. We compare our proposed joint SA-PNC schemes with the recently designed IA based techniques for the uplink heterogeneous systems. Simulation results show that the proposed SA-PNC is quite efficient to remove the inter-tier/system interference while allowing to increase the overall data rate, by serving more users, as compared with the IA based method