Crescimento e caracterização de fibras de TiO2 e nano/microcristais de ZnO

Mestrado em FísicaNeste trabalho foram crescidas fibras de dióxido de titânio, através da técnica de fusão de zona com laser, bem como nano e microcristais de óxido de zinco, através do método de deposição de fluxo assistido por laser. Ambos os materiais foram crescidos em atmosfera não controlada. Estas amostras foram caracterizadas óptica e estruturalmente. A caracterização englobou técnicas como a microscopia electrónica de varrimento, a difracção de raios X, a espectroscopia Raman e a fotoluminescência. Foram ainda efectuados cálculos teóricos para duas das fases estruturais do dióxido de titânio: rutilo e anatase. A partir desses cálculos foram obtidas as respectivas estruturas de bandas, bem como algumas propriedades estruturais, elásticas e ópticas destes materiais. Através de microscopia electrónica de varrimento foi observada a morfologia das fibras de TiO2 e dos cristais de ZnO e recorrendo à difracção de raios X foram identificadas as suas fases cristalinas. A espectroscopia Raman foi utilizada de forma confirmar a identificação da estrutura cristalina das amostras através dos seus modos normais de vibração. Para a caracterização óptica foi utilizada a técnica de fotoluminescência em estado estacionário. As fibras de TiO2 correspondem à fase rutilo e, a baixa temperatura, a recombinação óptica é dominada por uma banda de emissão centrada a » 1:47eV , observando-se ainda, duas linhas de zero fonões. A dependência destas linhas com a temperatura foi também estudada. Relativamente ao ZnO, observou-se uma intensa emissão na zona do UV e uma emissão verde mais fraca. Foi verificada a dependência desta emissão com a temperatura. Ambos os materiais apresentam uma boa qualidade cristalina e óptica. A deposição de fluxo assistida por laser apresenta-se como uma nova técnica no crescimento de nano/microcristais de ZnO.In this work titanium dioxide fibers were grown by the laser floating zone method, and zinc oxide nano and microcrystals were grown by the method of laser assisted flow deposition. Both materials were grown in a non-controlled atmosphere. These samples were optical and structural characterized. The samples were characterized by scanning electron microscopy (SEM), X ray diffraction, Raman spectroscopy and photoluminescense. Theoretical calculations were also carried out for two of the structural phases of titanium dioxide (rutile and anatase). From this calculations we obtained the bands structure, as well as some relevant structural, elastic and optical properties of these materials. TiO2 and ZnO fiber morphology was observed by means of electron microscopy and X-ray diffraction was used to identify their crystalline structure. Raman spectroscopy was used in order to confirm the identification of the crystalline structure of the samples through their normal modes of vibration. Optical properties were monitored by means of steady-state photoluminescence. The fibers of TiO2 corresponded to the rutile phase. At low temperature, the recombination was dominated by an emission centered at » 1:47 eV, along with two zero phonon lines. The dependence of these lines with temperature was also studied. For the ZnO, we observed a strong green emission, but the dominant emission is the excitonic one. It was verified the dependence of this emission with temperature. Both materials had a high optical and crystalline quality. The laser floating zone technique is quite stable for the growth of crystalline fibers of TiO2. The laser assisted flow deposition is presented as a new technique in the growth of nano/microcrystals of ZnO

Nanoestruturas baseadas em ZnO e GaN para aplicações optoeletrónicas : síntese e caracterização

Wide bandgap semiconductors, such as GaN and ZnO, are materials with a wide range of applications in several important technological areas including lighting, transparent electronics, sensors, catalysis or photovoltaics. This thesis focuses on the study of GaN and ZnO, including related compounds. In the first case, the emphasis is given to the incorporation of rare-earth (RE) ions (4fn) into the nitride hosts envisaging to contribute for the development of “all-nitride” solid state lighting devices. GaN and related III-nitrides ternary alloys appear as excellent hosts for the incorporation of these ions. The use of RE ions is motivated by the electromagnetic widespread spectral range (from the ultraviolet to the near infrared) covered by the intraionic radiative relaxation of the trivalent charged ions. Ion implantation appears as an alternative approach to doping since it allows the introduction of impurities in a controlled way and without solubility limits. GaN samples with different dimensionalities were analysed and their influence in the luminescence properties of the RE3+ was investigated. Photoluminescence (PL) measurements revealed that after thermal annealing a successful optical activation of the RE3+ was achieved for the samples implanted with the different RE3+. A detailed spectroscopic analysis of RE3+ luminescent tarnsitions is presented by using temperature dependent steady-state PL, room temperature PL excitation and time resolved PL. This thesis also aims to the growth and characterization of ZnO micro and nanostructures, through a new growth technique designated by laser assisted flow deposition (LAFD). LAFD is a very high yield method based on a vapour-solid mechanism that enables the growth of ZnO crystals in a very short timescale. LAFD was used in the growth of wurtzite micro/nanocrystalline ZnO with different morphologies (nanoparticles, tetrapods and microrods) as revealed by the extensive morphological characterization. Moreover, structural analysis evidenced the high crystalline quality of the produced crystals. The optical properties of the as-grown ZnO crystals were fully investigated by luminescence techniques, which revealed a high optical quality of the LAFD produced ZnO. In addition to the unintentionally doped micro/nanocrystals, ZnO/Ag and ZnO/carbon nanotubes (CNT) composite structures were also synthesized by LAFD. Silver-related spherical particles were found to be inhomogeneously distributed at the microrods surface, accumulating at the rods tips and promoting the ZnO nanorods re-nucleation. For the case of the ZnO/CNT composites two main approaches were adopted: i) a direct deposition of ZnO particles on the surface of vertically aligned multi-walled carbon nanotubes (VACNTs) forests without employing any additional catalyst and ii) ZnO/CNT buckypaper nanocomposites. It was found that the use of the LAFD technique carried out in framework of the first approach preserves the CNTs structure, their alignment, and avoids the collapse of the VACNTs array, which is a major advantage of this method. Additionally, taking into account that a crucial step in designing modern optoelectronic devices is to accomplish bandgap engineering, the optical properties of CdxZn1-xO alloy were also evaluated. A tuning of the ZnO bandgap towards the visible spectral region was accomplished by alloying this semiconductor with CdO. Finally, the potential application of the LAFD produced ZnO structures in the photocatalysis and photovoltaic fields was tested.Os semicondutores de elevado hiato energético, como é o caso do GaN e do ZnO, são materiais com aplicações em diversas áreas tecnológicas, que incluem, por exemplo, iluminação, eletrónica transparente, sensores, catalisadores ou fotovoltaicos. Esta tese é dedicada ao estudo de materiais baseados em GaN e ZnO, sendo dada ênfase à incorporação de iões terras-raras (RE) nas matrizes de nitretos, com a finalidade de contribuir para o desenvolvimento de dispositivos de iluminação de estado sólido. O uso dos iões RE é motivado pelas suas emissões intraiónicas abrangendo uma ampla gama espectral (do ultravioleta ao infravermelho próximo), quando estão no seu estado de carga trivalente. A implantação iónica surge como uma alternativa para a dopagem destes materiais, uma vez que permite a introdução de dopantes de uma forma controlada e independente dos limites de solubilidade dos iões nas matrizes. Amostras de GaN com diferentes dimensionalidades foram analisadas e a sua influência nas propriedades luminescentes dos RE3+ foi investigada. Medidas de fotoluminescência (PL) revelaram que, depois de um tratamento térmico, a ativação ótica dos iões foi bem-sucedida para as amostras implantadas com os diferentes iões. Uma análise espectroscópica detalhada das transições luminescentes dos RE3+ foi realizada usando técnicas como a PL em estado estacionário e transiente e excitação da fotoluminescência. Outro objetivo desta tese foi o crescimento e caracterização de micro e nanoestruturas de ZnO, recorrendo a uma nova técnica de crescimento designada por deposição de fluxo assistida por laser (LAFD). Este é um método com elevado rendimento, baseado num mecanismo sólido-vapor, que permite o crescimento de ZnO com diferentes morfologias (nanopartíclulas, tetrapodes e microfios). A sua análise estrutural pôs em evidência a excelente qualidade cristalina do ZnO produzido por esta técnica. As propriedades óticas foram também investigadas através de fotoluminescência, revelando a sua elevada qualidade ótica. Para além dos cristais não dopados intencionalmente, foram ainda preparados compósitos com prata e nanotubos de carbono (CNTs). No primeiro caso, foram observadas partículas esféricas de prata distribuídas de uma forma não uniforme na superfície dos microfios, mostrando uma tendência para se acumularem no topo destes e promovendo a sua renucleação. No caso dos compósitos ZnO/CNTs, foram usadas duas abordagens: i) deposição de partículas de ZnO diretamente no topo dos CNTs alinhados verticalmente, sem a utilização de nenhum catalisador adicional, e ii) produção de ZnO/CNTs buckypapers. No primeiro caso, a técnica de LAFD provou manter o alinhamento dos CNTs, evitando o seu colapso, sendo esta uma vantagem do método usado. Adicionalmente, tendo em consideração a importância do controlo do hiato energético dos materiais a ser aplicados em dispositivos optoelectrónicos, foram também estudadas as propriedades óticas da liga CdxZn1-xO. Devido ao aumento da fração molar de CdO na liga ternária observou-se um desvio do hiato do ZnO para a região visível do espetro eletromagnético. Finalmente, as estruturas de ZnO crescidas por LAFD foram testadas em dispositivos fotovoltaicos e em estudos de fotocatálisePrograma Doutoral em Nanociências e Nanotecnologi

Inclusão e direito à educação: práticas socioeducativas orientadas para a superação do insucesso e abandono escolar, na perspetiva dos atores

Enquadrada por um projeto mais amplo (financiado pela FCT), que se debruça sobre a análise de práticas, vozes e percursos de superação do insucesso e abandono escolar, esta comunicação propõe-se discutir fatores que suportam a construção de práticas socioeducativas inclusivas – ou seja, aquelas que potenciam a interrupção da espiral negativa insucesso-abandono. A base empírica desta comunicação é um estudo multi-caso de onze práticas socioeducativas, desenvolvidas em quatro municípios portugueses, focado na análise da intervenção sobre o insucesso e abandono escolar, que mapeia os pontos de vista de atores institucionais envolvidos em projetos enquadrados por dois programas de intervenção de âmbito nacional. Focar-nos-emos especificamente em quatro dessas práticas, localizadas num dos quatro municípios. Esta comunicação pretende aprofundar a discussão sobre o direito à educação, especificamente a promoção da assiduidade e a redução das taxas de abandono (Artigo 28.º da Convenção sobre os Direitos da Criança), bem como o papel da educação no fomento da igualdade com identidade (Artigo 29.º da CDC). Professores e técnicos, crianças e jovens, e encarregados de educação identificam e caracterizam práticas socioeducativas bem-sucedidas, contribuindo para a compreensão dos processos, lógicas e parcerias que as sustentam. Integraremos nesta discussão algumas reflexões sobre aspetos inovadores destas práticas socioeducativas, bem como sobre a participação de pais/famílias e comunidade na promoção do sucesso educativo de crianças e jovens, com base na análise dos resultados obtidos nas duas fases de recolha de dados, realizadas através de entrevistas semi-diretivas e análise documental/estatística (2016-2017) e grupos focais (2017-2018). Tendo sido identificadas quatro grandes tipologias de práticas (Agrupamento de Alunos, Apoio ao Estudo, Diferenciação Pedagógica e Mediação), foram os atores envolvidos em práticas de mediação que mais claramente identificaram e discutiram os modos como estas promovem a motivação das crianças/jovens para a escolaridade e para a aprendizagem, e as formas como estas práticas valorizam a cultural local e a identidade de pertença das crianças/jovens (Art.º 29). No entanto, há também vozes críticas: pais e crianças identificam algumas instâncias de discriminação por parte da Escola; professores e técnicos, por seu lado, verbalizam perceções de desinvestimento e desresponsabilização por parte das famílias.PTDC/MHC-CED/3775/2014info:eu-repo/semantics/publishedVersio

Skin Barrier Function Evaluation by Bi-compartmental Analisys of TEWL Dynamical Measurements: Validation of New Analytical Conditions

This paper reviews a methodology based on mathematical modelling of data of transepidermal water loss (TEWL) after conducting a plastic occlusion stress test (POST), to assess the hydric skin dynamic by kinetic parameters. Although simple to implement, this method is time-consuming, since it normally involves collecting data for at least 30 minutes. This research is aimed at optimizing the protocol by reducing the total time of the experiment by collecting more points during the initial stage. It was possible to significantly reduce analysis time, which is advantageous both for researchers and for volunteers since, on the one hand, there is a reduction in the cost of research, and on the other hand it ensures the comfort of the study participants

Health status and COVID-19 epidemiology in an inland region of Portugal: A retrospective study

Multiple factors, from socioeconomic development to genetic background, can affect the regional impact of some diseases, and this has also been seen during the COVID-19 pandemic. The objective of this retrospective study was to characterize a population in the interior of Portugal regarding health status and COVID-19 epidemiology. Between October 2021 and January 2023, 1553 subjects residing in Beira Baixa, Portugal, were included. Using a self-report approach, demographic and clinical data were obtained. Blood group, blood pressure, peripheral oxygen saturation and anti-spike protein immunoglobulin concentration were also analyzed. Statistical analysis was performed using IBM SPSS Statistics. The average age of the participants was 48.95 (±14.43) years, with 64% being male and 36% being female. The most prevalent comorbidities were hypertension (19.2%), dyslipidemia (12.6%) and diabetes mellitus (6.6%). Half of the population was overweight, and more than half of the subjects had no history of tobacco consumption. Among the participants, 33% were infected with SARS-CoV-2: 70.1% had mild disease, 14.1% moderate disease and 1.4% severe disease. There was a very significant adherence to vaccination (97%). Previously infected or vaccinated people had higher anti-spike protein immunoglobulin values; this value depended on the vaccine administered (p < 0.001). Patients with autoimmune diseases and smokers had lower levels of anti-S IgG antibodies (p = 0.030 and p = 0.024, respectively). The severity of COVID-19 did not affect the concentration of anti-S IgG (p = 0.430). This study highlights the general health statuses and the impact of COVID-19 on a population in the Portuguese interior. Knowledge of the circulation and impact of the virus in this specific population can alert and assist in better interventions being conducted by health authorities.This study was funded by COMPETE 2020—COVID-19 (AAC 02/SAICT/2020). This work was also financed by the European Regional Development Fund (ERDF), through the COMPETE 2020—Operational Programme for Competitiveness and Internationalisation and Portuguese national funds via FCT—Fundação para a Ciência e a Tecnologia, under project[s] UIDB/04539/2020, UIDP/04539/2020 and LA/P/0058/2020.info:eu-repo/semantics/publishedVersio

Proof-of-Concept Study of Multifunctional Hybrid Nanoparticle System Combined with NIR Laser Irradiation for the Treatment of Melanoma

Supplementary Materials - available online at https://www.mdpi.com/article/10.3390/biom11040511/s1The global impact of cancer emphasizes the importance of developing innovative, effective and minimally invasive therapies. In the context of superficial cancers, the development of a multifunctional nanoparticle-based system and its in vitro and in vivo safety and efficacy characterization are, herein, proposed as a proof-of-concept. This multifunctional system consists of gold nanoparticles coated with hyaluronic and oleic acids, and functionalized with epidermal growth factor for greater specificity towards cutaneous melanoma cells. This nanoparticle system is activated by a near-infrared laser. The characterization of this nanoparticle system included several phases, with in vitro assays being firstly performed to assess the safety of gold nanoparticles without laser irradiation. Then, hairless immunocompromised mice were selected for a xenograft model upon inoculation of A375 human melanoma cells. Treatment with near-infrared laser irradiation for five minutes combined with in situ administration of the nanoparticles showed a tumor volume reduction of approximately 80% and, in some cases, led to the formation of several necrotic foci, observed histologically. No significant skin erythema at the irradiation zone was verified, nor other harmful effects on the excised organs. In conclusion, these assays suggest that this system is safe and shows promising results for the treatment of superficial melanoma.The authors would like to thank to Fundação para a Ciência e Tecnologia (FCT) for the essential financial support under the project’s references PTDC/BBB-BMC/0611/2012, UIDB/00645/2020, UIDB/04138/2020 and UIDP/04138/2020 as well as for the PhD fellowships SFRH/BD/148044/2019 and SFRH/BD/147306/2019.info:eu-repo/semantics/publishedVersio

Proof-of-Concept Study of Multifunctional Hybrid Nanoparticle System Combined with NIR Laser Irradiation for the Treatment of Melanoma

Abstract: The global impact of cancer emphasizes the importance of developing innovative, effective and minimally invasive therapies. In the context of superficial cancers, the development of a multifunctional nanoparticle-based system and its in vitro and in vivo safety and efficacy characterization are, herein, proposed as a proof-of-concept. This multifunctional system consists of gold nanoparticles coated with hyaluronic and oleic acids, and functionalized with epidermal growth factor for greater specificity towards cutaneous melanoma cells. This nanoparticle system is activated by a near-infrared laser. The characterization of this nanoparticle system included several phases, with in vitro assays being firstly performed to assess the safety of gold nanoparticles without laser irradiation. Then, hairless immunocompromised mice were selected for a xenograft model upon inoculation of A375 human melanoma cells. Treatment with near-infrared laser irradiation for five minutes combined with in situ administration of the nanoparticles showed a tumor volume reduction of approximately 80% and, in some cases, led to the formation of several necrotic foci, observed histologically. No significant skin erythema at the irradiation zone was verified, nor other harmful effects on the excised organs. In conclusion, these assays suggest that this system is safe and shows promising results for the treatment of superficial melanoma

A neurophysiological signature of dynamic emotion recognition associated with social communication skills and cortical gamma-aminobutyric acid levels in children

IntroductionEmotion recognition is a core feature of social perception. In particular, perception of dynamic facial emotional expressions is a major feature of the third visual pathway. However, the classical N170 visual evoked signal does not provide a pure correlate of such processing. Indeed, independent component analysis has demonstrated that the N170 component is already active at the time of the P100, and is therefore distorted by early components. Here we implemented, a dynamic face emotional paradigm to isolate a more pure face expression selective N170. We searched for a neural correlate of perception of dynamic facial emotional expressions, by starting with a face baseline from which a facial expression evolved. This allowed for a specific facial expression contrast signal which we aimed to relate with social communication abilities and cortical gamma-aminobutyric acid (GABA) levels.MethodsWe recorded event-related potentials (ERPs) and Magnetic Resonance (MRS) measures in 35 typically developing (TD) children, (10–16 years) sex-matched, during emotion recognition of an avatar morphing/unmorphing from neutral to happy/sad expressions. This task allowed for the elimination of the contribution low-level visual components, in particular the P100, by morphing baseline isoluminant neutral faces into specific expressions, isolating dynamic emotion recognition. Therefore, it was possible to isolate a dynamic face sensitive N170 devoid of interactions with earlier components.ResultsWe found delayed N170 and P300, with a hysteresis type of dependence on stimulus trajectory (morphing/unmorphing), with hemispheric lateralization. The delayed N170 is generated by an extrastriate source, which can be related to the third visual pathway specialized in biological motion processing. GABA levels in visual cortex were related with N170 amplitude and latency and predictive of worse social communication performance (SCQ scores). N170 latencies reflected delayed processing speed of emotional expressions and related to worse social communication scores.DiscussionIn sum, we found a specific N170 electrophysiological signature of dynamic face processing related to social communication abilities and cortical GABA levels. These findings have potential clinical significance supporting the hypothesis of a spectrum of social communication abilities and the identification of a specific face-expression sensitive N170 which can potentially be used in the development of diagnostic and intervention tools

New bacterial biorecognition elements from phage origin

Book of Abstracts of CEB Annual Meeting 2017info:eu-repo/semantics/publishedVersio

Histological inflammation in the endoscopically uninflamed mucosa is associated with worse outcomes in limited ulcerative colitis

Background: The Montreal classification categorizes patients with ulcerative colitis (UC) based on their macroscopic disease extent. Independent of endoscopic extent, biopsies through all colonic segments should be retrieved during index colonoscopy. However, the prognostic value of histological inflammation at diagnosis in the inflamed and uninflamed regions of the colon has never been assessed.Methods: This was a multicenter retrospective cohort study of newly diagnosed patients with treatment-naïve proctitis and left-sided UC. Biopsies from at least 2 colonic segments (endoscopically inflamed and uninflamed mucosa) were retrieved and reviewed by 2 pathologists. Histological features in the endoscopically inflamed and uninflamed mucosa were scored using the Nancy score. The primary outcomes were disease complications (proximal disease extension, need for hospitalization or colectomy) and higher therapeutic requirements (need for steroids or for therapy escalation).Results: Overall, 93 treatment-naïve patients were included, with a median follow-up of 44 months (range, 2-329). The prevalence of any histological inflammation above the endoscopic margin was 71%. Proximal disease extension was more frequent in patients with histological inflammation in the endoscopically uninflamed mucosa at diagnosis (21.5% vs 3.4%, P = 0.04). Histological involvement above the endoscopic margin was the only predictor associated with an earlier need for therapy escalation (adjusted hazard ratio, 3.69; 95% confidence interval, 1.05- 13.0); P = 0.04) and disease complications (adjusted hazard ratio, 4.79; 95% confidence interval, 1.10-20.9; P = 0.04).Conclusions: The presence of histological inflammation in the endoscopically uninflamed mucosa at the time of diagnosis was associated with worse outcomes in limited UC.peer-reviewe