Libertação fotocontrolada de moléculas bioativas a partir de conjugados de cumarinas

Dissertação de mestrado em Química Medicinal

Electronic structure and optical signatures of semiconducting transition metal dichalcogenide nanosheets

CONSPECTUS: Two-dimensional (2D) crystals derived from transition metal dichalcogenides (TMDs) are intriguing materials that offer a unique platform to study fundamental physical phenomena as well as to explore development of novel devices. Semiconducting group 6 TMDs such as MoS2 and WSe2 are known for their large optical absorption coefficient and their potential for high efficiency photovoltaics and photodetectors. Monolayer sheets of these compounds are flexible, stretchable, and soft semiconductors with a direct band gap in contrast to their well-known bulk crystals that are rigid and hard indirect gap semiconductors. Recent intense research has been motivated by the distinct electrical, optical, and mechanical properties of these TMD crystals in the ultimate thickness regime. As a semiconductor with a band gap in the visible to near-IR frequencies, these 2D MX2 materials (M = Mo, W; X = S, Se) exhibit distinct excitonic absorption and emission features. In this Account, we discuss how optical spectroscopy of these materials allows investigation of their electronic properties and the relaxation dynamics of excitons. We first discuss the basic electronic structure of 2D TMDs highlighting the key features of the dispersion relation. With the help of theoretical calculations, we further discuss how photoluminescence energy of direct and indirect excitons provide a guide to understanding the evolution of the electronic structure as a function of the number of layers. We also highlight the behavior of the two competing conduction valleys and their role in the optical processes. Intercalation of group 6 TMDs by alkali metals results in the structural phase transformation with corresponding semiconductor-to-metal transition. Monolayer TMDs obtained by intercalation-assisted exfoliation retains the metastable metallic phase. Mild annealing, however, destabilizes the metastable phase and gradually restores the original semiconducting phase. Interestingly, the semiconducting 2H phase, metallic 1T phase, and a charge-density-wave-like 1T' phase can coexist within a single crystalline monolayer sheet. We further discuss the electronic properties of the restacked films of chemically exfoliated MoS2. Finally, we focus on the strong optical absorption and related exciton relaxation in monolayer and bilayer MX2. Monolayer MX2 absorbs as much as 30% of incident photons in the blue region of the visible light despite being atomically thin. This giant absorption is attributed to nesting of the conduction and valence bands, which leads to diversion of optical conductivity. We describe how the relaxation pathway of excitons depends strongly on the excitation energy. Excitation at the band nesting region is of unique significance because it leads to relaxation of electrons and holes with opposite momentum and spontaneous formation of indirect excitons.

Questões de género nas revistas generalistas de informação em Portugal: cruzamentos temáticos na Sábado e Visão

As revistas de informação generalista configuram uma interseção entre as representações socioeconómicas, políticas e culturais e os quotidianos da população. Neste artigo apresentamos uma análise temática das revistas de informação generalista Sábado e Visão, as mais lidas do segmento em Portugal. O corpus de análise foi composto por 440 peças jornalísticas de 104 edições que correspondem a todos os números editados em 2011 por estas duas publicações. O estudo empírico, realizado com recurso ao software NVivo 10, revela uma transversalidade da abordagem aos temas político-económicos, espelho da conjuntura nacional e internacional no ano de 2011. As diferenças mais visíveis entre as duas revistas revelam uma maior opção pelos temas Sexualidades e Relações de Intimidade e Jet set na Sábado e Saúde, Lazer e bem-estar na Visão. Além disso, no que concerne às representações de género, presentes em vários temas, surgem na generalidade assentes num binarismo que transpõe o olhar da dimensão de género para o sexo biológico e que opõe as representações tradicionais da feminilidade e masculinidade, condicionando o surgimento de representações alternativas.

Constraints on new phenomena via Higgs boson couplings and invisible decays with the ATLAS detector

The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb−1 of pp collision data at √s=7 TeV and 20.3 fb−1 at √s=8 TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the γγ, ZZ, W W , Zγ, bb, τ τ , and μμ decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the γγ and ZZ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of m A > 370 GeV in the “hMSSM” simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with W/Z (Z → ℓℓ, W/Z → jj) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter.

Flexible organic–inorganic hybrid layer encapsulation for organic opto-electronic devices

In this work we produce and study the flexible organic–inorganic hybrid moisture barrier layers for the protection of air sensitive organic opto-electronic devices. The inorganic amorphous silicon nitride layer (SiNx:H) and the organic PMMA [poly (methyl methacrylate)] layer are deposited alternatingly by using hot wire chemical vapor deposition (HW-CVD) and spin-coating techniques, respectively. The effect of organic–inorganic hybrid interfaces is analyzed for increasing number of interfaces. We produce highly transparent (∼80% in the visible region) hybrid structures. The morphological properties are analysed providing a good basis for understanding the variation of the water vapor transmission rate (WVTR) values. A minimum WVTR of 4.5 × 10−5g/m2day is reported at the ambient atmospheric conditions for 7 organic/inorganic interfaces. The hybrid barriers show superb mechanical flexibility which confirms their high potential for flexible applications.

Influence of the hip joint modeling approaches on the kinematics of human gait

The influence of the hip joint formulation on the kinematic response of the model of human gait is investigated throughout this work. To accomplish this goal, the fundamental issues of the modeling process of a planar hip joint under the framework of multibody systems are revisited. In particular, the formulations for the ideal, dry, and lubricated revolute joints are described and utilized for the interaction of femur head inside acetabulum or the hip bone. In this process, the main kinematic and dynamic aspects of hip joints are analyzed. In a simple manner, the forces that are generated during human gait, for both dry and lubricated hip joint models, are computed in terms of the system’s state variables and subsequently introduced into the dynamics equations of motion of the multibody system as external generalized forces. Moreover, a human multibody model is considered, which incorporates the different approaches for the hip articulation, namely ideal joint, dry, and lubricated models. Finally, several computational simulations based on different approaches are performed, and the main results presented and compared to identify differences among the methodologies and procedures adopted in this work. The input conditions to the models correspond to the experimental data capture from an adult male during normal gait. In general, the obtained results in terms of positions do not differ significantly when the different hip joint models are considered. In sharp contrast, the velocity and acceleration plotted vary significantly. The effect of the hip joint modeling approach is clearly measurable and visible in terms of peaks and oscillations of the velocities and accelerations. In general, with the dry hip model, intra-joint force peaks can be observed, which can be associated with the multiple impacts between the femur head and the cup. In turn, when the lubricant is present, the system’s response tends to be smoother due to the damping effects of the synovial fluid.

Preparação de suspensões aquosas de nanopartículas de carbono para deposição em superfícies

Dissertação de mestrado integrado em Engenharia de Materiais

Scarless laparoscopic repair of epigastric hernia in children

Background Despite the small size of the incision, the scar left by open repair of epigastric hernia in children is unaesthetic. Few laparoscopic approaches to epigastric hernia repair have been previously proposed, but none has gain wide acceptance from pediatric surgeons. In this study, we present our experience with a scarless laparo- scopic approach using a percutaneous suturing technique for epigastric hernia repair in children. Methods Ten consecutive patients presenting with epi- gastric hernia 15 mm or further from the umbilicus were submitted to laparoscopic hernia repair. A 5-mm 308-angle laparoscope is introduced through a umbilical trocar and a 3-mm laparoscopic dissector is introduced through a stab incision in the right flank. After opening and dissecting the parietal peritoneum, the fascial defect is identified and closed using 2–0 polyglactin thread through a percutaneous suturing technique. Intraoperative and postoperative clinical data were collected. Results All patients were successfully submitted to la- paroscopic epigastric hernia repair. Median age at surgery was 79 months old and the median distance from the um- bilicus to the epigastric defect was 4 cm. Operative time ranged from 35 to 75 min. Every hernia was successfully closed without any incidents. Follow-up period ranges from 2 to 12 months. No postoperative complications or recurrence was registered. No scar was visible in these patients. Conclusion This scarless laparoscopic technique for epi- gastric hernia repair is safe and reliable. We believe this technique might become gold standard of care in the near future.

Estufa de aproveitamento solar térmico para reabilitação de edifícios

Dissertação de mestrado em sustentabilidade do ambiente construido

Desenvolvimento de materiais para isolamento térmico com base em biomimética

Dissertação de mestrado Internacional em Sustentabilidade do Ambiente Construído

A study of risk-aware program transformation

In the trend towards tolerating hardware unreliability, accuracy is exchanged for cost savings. Running on less reliable machines, functionally correct code becomes risky and one needs to know how risk propagates so as to mitigate it. Risk estimation, however, seems to live outside the average programmer’s technical competence and core practice. In this paper we propose that program design by source-to-source transformation be risk-aware in the sense of making probabilistic faults visible and supporting equational reasoning on the probabilistic behaviour of programs caused by faults. This reasoning is carried out in a linear algebra extension to the standard, `a la Bird-Moor algebra of programming. This paper studies, in particular, the propagation of faults across standard program transformation techniques known as tupling and fusion, enabling the fault of the whole to be expressed in terms of the faults of its parts.

Novas funcionalidades para dispositivos médicos invasivos com imagem

Tese de Doutoramento em Engenharia Eletrónica e de Computadores.

Synthesis of new peptide derivatives that self-assemble into nanostructured hydrogels for biomedical applications

Tese de Doutoramento em Ciências (área de especialização em Química)

Silent citizens: on silence and silencing in journalism

Constructivist approaches to journalism, which have dominated the field for most of the second half of the 20th century, underline how selection and ranking processes produce representations and interpretations of social reality. Theoretical perspectives such as agenda-setting or framing have been pointing to the ways production of news messages are shaped and issues are defined. Research inspired by these contributions does however seem to keep in an area of relative shade not so much what is said and published but what is not selected: the unsaid, the withheld, the untold of journalism. The reality that remains in silence, for not being noticed or for being silenced, is the reverse of the coin of what is made visible. In this paper, it is suggested that this situation opens up the debate to a relatively unknown continent, which could contribute to the larger discussion on the current crisis in journalism. It is our contention that ‘the untold’ might be at the confluence of different levels: the journalistic agenda-setting by news sources; the deterioration of working conditions of journalists, compromising the investigation; and the social capital asymmetries from important segments of the population, hampering the public word (speech?) and the right to communicate. In order to build a comprehensive picture of the potentialities and contradictions of journalism from the unsaid side, we would put forward the outline of a typology of journalism's silences, with particular emphasis on some aspects of "discursive discrimination" (Boréus, 2006), on the one hand, and on citizen silence in the process of journalistic production, on the other hand.

As políticas tecnológicas para a educação e a literacia digital: o caso do programa governamental ‘e.escolinha’

Em 2008, o Governo português anunciou a iniciativa ‘e.escolinha’ que contemplou a distribuição de computadores ‘Magalhães’ aos alunos do 1º ciclo do ensino básico, durante três anos letivos consecutivos. Atualmente suspenso, o programa foi bandeira do XVII Governo Constitucional, liderado por José Sócrates, mas alvo de controvérsias por parte da oposição política e da comunidade escolar, sobretudo pela aparente tónica no acesso à tecnologia em vez de uma maior preocupação com a formação e as práticas pedagógicas. Ao abrigo do Plano Tecnológico da Educação, o ‘e.escolinha’ inseria-se numa política mais ampla para o desenvolvimento de uma economia competitiva e dinâmica, através das metas estabelecidas pela União Europeia na Estratégia de Lisboa 2000. A iniciativa foi apresentada ao país com objetivos ambiciosos, no que diz respeito às esperadas mudanças ao nível das práticas pedagógicas dos professores, do processo de aprendizagem das crianças e do sucesso escolar em geral. Porém, a face mais visível da política, embora possa compreender outros matizes, poderá ter ficado reduzida à questão do acesso, apostando pouco nas outras dimensões da literacia digital. Com base em entrevistas realizadas a atores-chave envolvidos no processo de conceção e implementação do ‘e.escolinha’, e nos documentos oficiais que enquadram o programa, o presente artigo pretende dar a conhecer a forma como decisores políticos e empresas enunciam e avaliam os objetivos desta iniciativa. Pretende-se, em particular, conhecer se partilham a ideia de uma deriva tecnológica desta medida governamental ou se entreveem, na mesma, objetivos de literacia digital. Este trabalho decorre do projeto de investigação “Navegando com o Magalhães: Estudo sobre o Impacto dos Media Digitais nas Crianças”, em curso no Centro de Estudos de Comunicação e Sociedade da Universidade do Minho, financiado pela Fundação para a Ciência e Tecnologia ((PTDC/CCI-COM/101381/2008) ) e co-financiado pelo FEDER (COMPETE: FCOMP-01-0124-FEDER-009056).