Seminário do Grupo de Polímeros: “Nonlinear imaging in turbid biological media”
Nonlinear microscopy (NLM) has emerged as a powerful technique for biological imaging in a label-free manner. Two-photon fluorescence imaging of neural activity, coherent Raman scattering imaging of lipid-rich assemblies, second-harmonic generation imaging of collagen structures and sensitive screening of pharmaceuticals, are just a few representative examples. Despite the tremendous impact of NLM, all of nonlinear imaging modalities can only image at shallow depths because deeper penetration imaging into biological specimens is hindered by scattering phenomena. In the first part of this presentation, and in order to present the current state-of-the-art nonlinear imaging capabilities, I will present a study of depolarization effects due to scattering on polarization-resolved coherent anti-Stokes Raman scattering imaging of opaque spinal cords myelin sheaths. The results highlight how scattering can lead to erratic conclusions and also how shallow nonlinear imaging is currently possible on biological specimens. I will then present how we used wavefront shaping (WS) technique to image through strongly scattering media in order to enhance the (imaging) penetration depth. After an explanation of WS fundamentals, I will show how we successfully imaged nonlinear sources of second-harmonic photons after strongly scattering medium, at a sub-diffraction limited resolution. These results demonstrate that nonlinear imaging deep in biological specimens is no longer limited to shallow depths.
Current EU regulations on the mandatory labelling of genetically modified organisms (GMOs) with a minimum content of 0.9% would benefit from the availability of reliable and rapid methods to detect and quantify DNA sequences specific for GMOs. Different genosensors have been developed to this aim, mainly intended for GMOs screening. A remaining challenge, however, is the development of genosensing platforms for GMO quantification, which should be expressed as the number of event-specific DNA sequences per taxon-specific sequences. We report a simple and sensitive multiplexed electrochemical approach for the quantification of Roundup-Ready Soybean (RRS). Results indicate that the method could be applied for GMO quantification below the European labeling threshold level (0.9%), offering a general approach for the rapid quantification of specific GMO events in foods.
After a general introduction to time-dependent density-functional theory, several recent applications of the theory will be presented: We study the laser-induced ultrafast demagnetization of solid Fe, Co and Ni; we investigate the dynamics of chemical bonds and address the question, how much time an electron needs to make a transition from one state to another; we study molecular junctions focussing on cases where, after turning on a bias, no steady state is achieved; and finally we combine time-dependent density functional theory with optimal control theory to find laser pulses specifically tailored to enhance a single peak in the harmonic spectrum of atoms.
very different physical origin, such as the Quantum Hall Effect (QHE), the topological insulators (TI) and the quantum spin liquids (QSL). Because of the differences, it is at first glance hard to see any relation between these states, giving the appearance that the branch of topological condensed mater theory is completely fragmented. In spite of that some connections were recently found between the QHE, TIs and QSLs, opening new guidances to look for models that support topological phases. In this seminar, such connections will be introduced. The focus will be on a correspondence between a modified Kitaev honeycomb model and the Haldane model and on 3D strongly correlated systems in the strong spin-orbit regime. The first case inspired the generation of tight-binding models that supports either a QSL or a TI phase, establishing a method of generating certain types of desired states. In the second case, we review the research into systems that have a combination of the key elements for the generation of topologically non-trivial phases.
Photodynamic therapy (PDT) relies on the interaction between light, oxygen and a photosensitive chemical: Protoporphyrin IX (PpIX). Louise will talk about the current study being performed at Hospital Amaral Carvalho in Jahu city, where the build up of PpIX in different skin lesions is measured using the fluorescence signal produced by the drug. The research will help to gain more understanding of the kinetics and dynamics of the PDT treatment process as well as help to generate more accurate computer models. Initial results show that the PpIX builds up in the lesion linearly with time over the 3 hours of occlusive treatment.
We study the effect of strong spin-orbit coupling on bound states induced by impurities in superconductors. The presence of spin-orbit coupling breaks the SU(2)-spin symmetry and causes the superconducting order parameter to have generically both singlet (s-wave) and triplet (p-wave) components. As a result, impurity induced bound states corresponding to different angular momentum channels hybridize and display a number of qualitatively different features from that of the well-known Yu-Shiba-Rusinov states in conventional s-wave superconductors. In particular, we find that in the presence of spin-orbit coupling the spectrum of the impurity induced bound states depends on the orientation of the magnetic moment of the impurity. Our predictions can be used to distinguish the symmetry of the order parameter and have implications for the Majorana proposals based on chains of magnetic atoms placed on the surface of superconductors with strong spin-orbit coupling [1].
Molecular imaging is emerging as an incredibly powerful tool in oncology research. With unprecedented specificity to capture some of the key cancer hallmarks (e.g., proliferation), it can assess pharmacodynamic effects of various therapies on tumor response. A general overview of molecular imaging, its potential and limitations will be presented in the lecture. An example of a pharmacodynamic study using 3′-deoxy-3′[(18)F]-fluorothymidine, [(18)F]-FLT PET/CT in assessing response to anti-angiogenic therapies (VEGFR TKI) will be shown. Patient-specific modeling of tumor response to VEGFR TKI based on FLT PET/CT molecular imaging will be used to illustrate intimate connection between tumor modeling and molecular imaging-based clinical trials.