X-Ray Spectroscopy — The Driving Force to Understand and Develop Catalysis

Catalysis is involved in about 90% of manmade chemicals. The development of novel or improved catalysts requires fundamental understanding of the commanding steps of a catalytic reaction. In simple terms, a catalytic transformation depends on the coupling between catalyst electronic structure and reagents’ molecular orbitals. Herein, we report a spectroscopic technique capable of determining the electronic structure of metal containing catalysts under working conditions. The technique is called photon-in photon-out X-ray spectroscopy and can be employed to characterize materials, unveil substrate adsorption parameters, and follow changes in electronic structure during catalytic reactions

Heterogeneous Catalysis Experiments at XFELs. Are we Close to Producing a Catalysis Movie?

The advent of X-ray free electron lasers enabled scientist to achieve the goal of producing a movie of a catalytic transformation. This perspective highlights the technical developments both on facilities and X-ray spectroscopy that brought us a bit closer to attain the main goal. However there are a couple of issues that need to be solve, namely sample stability and selective triggering. Graphical Abstract

X‐Ray Spectroscopy on Biological Systems

In the field of biological studies, next to the standard methods, new tools are offered by contemporary physics. X‐ray spectroscopic techniques enable probing electronic structure of occupied and unoccupied states of studied atom and distinguish the oxidation state, local geometry, and ligand type of elements that occur in biological material. Direct analysis using X‐ray spectroscopy avoids many chemical preparation steps that might modify biological samples. The information obtained gives us insight into important biochemical processes all under physiological conditions. In this chapter we focus our attention to the application of X‐ray spectroscopy to the study of biological samples, with special emphasis on mechanisms revealing interaction between DNA and different cytotoxic agents and in the determination of changes in oxidation state of different elements in pathologically altered human cells and tissue

Autonomia para ensinar e aprender: pela liberdade na prática pedagógica

: Este artigo pretende refletir sobre ensinar e aprender a partir do conceito de autonomia, de Paulo Freire (1921-1997), que pressupõe a pedagogia pautada na liberdade, na democracia e no diálogo. Assim, salienta-se a necessidade da livre manifestação da curiosidade, a fim de que a prática pedagógica autoritária não iniba a invenção e, muito menos, negue a dimensão crítica da aprendizagem existencialmente manifestada no mundo. Em vista disso, fez-se uma análise do conceito de autonomia concernente ao pensamento de Freire, especialmente no que tange à sua obra Pedagogia da autonomia (1996). Dentre os possíveis resultados, conclui-se que a autonomia, além de necessária à práxis pedagógica, constitui também uma real alternativa de uma pedagogia inventiva e autêntica dentro da realidade educacional. A análise em questão evidencia, portanto, que a identidade do pensamento de Freire consiste prioritariamente em uma concepção crítica à autonomia para ensinar e aprender

In situ high energy resolution off-resonant spectroscopy applied to a time-resolved study of single site Ta catalyst during oxidation

In the present work high energy resolution off-resonant X-ray spectroscopy (HEROS) was employed at a synchrotron to study a silica supported Ta(V) bisalkyl catalyst activated in hydrogen. The Ta Lα1 HEROS spectra were measured during oxidation of the starting complex and the relative species’ concentration was successfully retrieved as a function of time using the fingerprint HEROS spectra measured for the unoxidized and the oxidized catalyst. Based on the experimental data and theory- based calculations, it was shown that oxidation of the active Ta catalyst leads to the formation of mono- and di-meric species on the SiO2 surface. The obtained results were compared to those of the previously reported time-resolved HEROS study on an inactive silica supported Ta(V) bisalkyl catalyst’s concentration evolution during its oxidation Błachucki et al. (2015). The study allowed observation of an immediate transition of the active Ta catalyst from its unoxidized form to the oxidized one. This finding is dissimilar to the result of the study on the inactive Ta catalyst, where the oxidation led through an intermediate step

Determination of conduction and valence band electronic structure of anatase and rutile TiO 2

Electronic structures of rutile and anatase polymorph of TiO2 were determined by resonant inelastic X-ray scattering measurements and FEFF9.0 calculations. Difference between crystalline structures led to shifts in the rutile Ti d-band to lower energy with respect to anatase, i.e., decrease in band gap. Anatase possesses localized states located in the band gap where electrons can be trapped, which are almost absent in the rutile structure. This could well explain the reported longer lifetimes in anatase. It was revealed that HR-XAS is insufficient to study in-depth unoccupied states of investigated materials because it overlooks the shallow traps. Graphical Abstract The resonant X-ray emission spectroscopy around Ti k-edge was applied to probe local electronic structure of TiO2 rutile and anatase. By measuring 1s→3d excitation and 3p→1s decay channel, differences between localized and delocalized orbitals were determined. The 3d pre-edge structures were compared with ab initio multiple scattering simulations

Study of the reactivity of silica supported tantalum catalysts with oxygen followed by in situ HEROS

We report on the reactivity of grafted tantalum organometallic catalysts with molecular oxygen. The changes in the local Ta electronic structure were followed by in situ high-energy resolution off-resonant spectroscopy (HEROS). The results revealed agglomeration and formation of Ta dimers, which cannot be reversed. The process occurs independently of starting grafted complex

A influência da liderança partilhada no bem-estar docente

educação e o mundo seria muito mais pobre, culturalmente e não só. Ao mesmo tempo, é uma profissão cada vez mais desafiante, mas em que nem todos os desafios são salutares, levando por vezes ao desgaste físico e psicológico. É considerada uma profissão de risco físico e mental, tornando assim os professores mais vulneráveis e suscetíveis a situações que põem em risco o seu bem-estar, o que inevitavelmente provoca impacto na qualidade da educação. A presente investigação, com o seu caráter exploratório pretende avaliar o impacto que o exercício de liderança, nomeadamente, da liderança partilhada tem sobre o bem-estar docente. Após a revisão bibliográfica sobre as temáticas: líder, liderança, liderança partilhada e bem-estar docente (em contraponto com o mal-estar), procurou-se compreender como os docentes percecionam a importância do líder e do estilo de liderança, bem como a forma como acham que este interfere no seu bem-estar. Procurou-se também perceber se consideram existir estilos de liderança que contribuam para esse bem-estar. Neste sentido, elaborou-se um questionário que foi aplicado a cinco docentes, que exercem funções em agrupamento de escolas diversificados. Os resultados alcançados parecem indicar que o estilo de liderança tem bastante influência no bem-estar do professor. A liderança partilhada é aquela que é defendida por todos como sendo a que mais contribui para o bem-estar docente. Palavras-chave: Líder, Liderança, Liderança Partilhada, Bem-estar e Mal-estar.

Reproducibility of the Vivatmopro measurements for exhaled nitric oxide values

Portable monitoring devices allow fraction exhaled nitric oxide (FeNO) measurements outside clinical settings. However, the reproducibility of the new portable device Vivatmo pro is not yet fully established. In this study, we aimed to assess the reproducibility of this device for FeNO measurements.info:eu-repo/semantics/publishedVersio

High energy resolution off-resonant spectroscopy: A review

We review the high energy resolution off-resonant spectroscopy (HEROS) technique. HEROS probes the unoccupied electronic states of matter in a single-shot manner thanks to the combination of off-resonant excitation around atomic core states using wavelength dispersive X-ray detection setups. In this review we provide a general introduction to the field of X-ray spectroscopy together with the specification of the available X-ray techniques and X-ray methodologies. Next, the theoretical description of the HEROS approach is introduced with a special focus on the derivation of the X- ray emission and X-ray absorption correspondence relation at off-resonant excitation conditions. Finally, a number of experimental HEROS reports are reviewed in the field of chemistry and material science. We emphasize the applicability of HEROS to pulsed X-ray sources, like X-ray free electron lasers, and support the review with experimental examples. The review is complemented with perspectives on and possible further applications of the HEROS technique to the field of X-ray science