Filosofísica: “Os ‘raios N’ de René Blondlot: uma anomalia (na história) da ciência”
O físico francês René Prospet Blondlot (1849-1930) fez grandes trabalhos. Seus estudos para medir a velocidade de ondas hertzianas (eletromagnéticas) são bastante originais, obtendo o valor de 298.000 Km/s experimentalmente. René Blondlot ganhou vários prêmios da Academia de Ciência de Paris.
No começo do século XX o nosso personagem 
rincipal começa a estudar as características dos raios X, recém-descobertos, e em 1903 divulga seus achados sobre uma nova radiação, os “raios N”. Essa descoberta fez sucesso, uma nova área da física nasceu, houve trabalhos aplicando os raios N ao estudo do sistema nervoso. Em 1905 a maioria dos físicos, incluindo revistas científicas, concluiu que essa radiação não existia.
Os argumentos contrários à existência dessa radiação se baseavam na suposição de que René e outros viam o que queriam ver, por autossugestão. O que é esquecido é que Blondlot respondeu a essas críticas seriamente, com evidências fotográficas. Mesmo assim o assunto morreu. Essa apresentação tem por objetivo adentrar essa rica história e analisar os argumentos e evidências da época. Há ainda muitos mistérios sobre esse estranho episódio.
scattering amplitudes, however some complications appear if the multiplicity of particles is large. For example, in the 2 to 2 scattering of gluons there are only 4 Feynman diagrams but if we add two extra gluons it grows to 220 diagrams. In the 80’s Stephen Parke and Tomasz Taylor found an incredible way to simplify the calculation of some classes of n-gluons scattering amplitudes based on helicity arguments. Since then, a lot of progress has been made on improving the amplitude techniques and on the understanding of the S-matrix physics. After a review of the spinor helicity formalism and some well known results based on it, I will discuss how we can use the helicity structure of scattering amplitudes in the SM and in the context of an effective Lagrangian description of BSM dynamics. The analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 to 2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. This have a big impact on how we should perform the EFT analysis and where we should search for new physics.
Spectroscopic and microscopic techniques allow analysis of various aspects of biological systems on molecular level. One of the common problems of such studies is overlapping of absorption or fluorescence spectra of biological molecules of interest. Several examples of how to separate them are shown for in vitro and in vivo systems. These examples include analysis of competitive binding of two molecules (anticancer drugs, mutagens and biologically active substances) to nucleic acids via absorption spectroscopy, separation of fluorescence spectra of Photosystems via time-resolved fluorescence spectroscopy and microscopy and analysis of Forster Resonance Energy Transfer (FRET) between voltage-sensitive fluorescence proteins. As a result constants of binding of anticancer drugs and mutagens to nucleic acids are determined for molecules that absorb light in the same region with nucleic acids. Also composition and ratio of Photosystems is determined in leaves, which opens room for non-invasive “express” analysis of these parameters in plants, allowing determination of optimal growing conditions and presence of diseases. FRET studies of voltage sensitive fluorescent protein help to figure out the mechanism of its action and improve its functionality. In general, it is shown that number of different approaches can be used to analyze overlapping absorption and fluorescence spectra of biological molecules on different levels of organization in vitro and in vivo.
Quantum states, their properties and dynamics are central to the understanding of the quantum world. They have received even more attention due to the raise of quantum technologies, which exploit the ‘quirks’ of quantum mechanics. Quantum states form Hilbert spaces, which combine the properties of two different types of mathematical spaces: vector space and metric space. While the vector-space aspects are widely used, the metric-space aspects are much less exploited. Here we show that conservation laws in quantum mechanics naturally lead to metric spaces for the set of related physical quantities. All such metric spaces have an “onion-shell” geometry. We will discuss these induced ‘natural’ metrics for some of the quantities fundamental to the understanding of quantum systems, as well as some applications of the metric space approach to quantum mechanics, including applications to further the understanding of the core concepts of Density Functional Theory.
Protons and neutrons, the particles which make up the nuclei of atoms, are comprised of tiny constituents called quarks. Quantum chromodynamics (QCD) is a field theory which describes the so-called strong “colour” force, mediated by gluons, which binds the quarks together and is responsible for formation of nucleons and other objects, collectively known as hadrons. While there is ample experimental evidence that this theory is correct, there are certain phenomena related to hadrons which are not yet fully understood within the QCD framework. We attempt to elucidate some of these issues by studying QCD and similar models by means of the Dyson-Schwinger and Bethe-Salpeter (DS/BS) functional formalism. This approach allows one to work with the basic degrees of freedom of QCD, the quarks and gluons (which are not directly detectable in experiments, being eternally bound within hadrons), while at the same time giving access to physical observables like hadron masses and decay constants. We briefly discuss the main ideas behind the DS/BS framework, and give examples of its applications through an investigation of one of the fundamental interaction vertices in QCD, as well as a calculation of light hadron masses in a model similar to chromodynamics. Our findings help in building towards a better understanding of not just QCD but strongly-interacting theories in general, which is important since some of these templates play an important role in other areas of high-energy particle physics.
Research and development related to polymers from renewable resources have witnessed a spectacular development from the beginning of this millennium, with a progressively deeper and wider involvement of both academia and industry. This lecture aims at providing a succinct “state of the art” of this exciting field through a number of examples of recent advances, including contributions from my research groups. Two main approaches are discussed, namely: The chemical modification of natural polymers. This topic covers the synthesis and characterization of novel materials and composites arising from the surface, in-depth and bulk transformation of celulose fibers, including nanofibers, chitosan, starch, lignin and natural rubber. The synthesis and polymerization of monomers derived from renewable resources. The variety of such monomers and macromonomers has already reached a remarkably wide spectrum and is increasing incessantly. The examples provided in this context deal with small molecules derived from sugars and polysaccharides, lignin, and larger structures derived from vegetable oils. Particular emphasis is placed on furan monomers and furan chemistry, which provide a new class of polymer chemistry, including the application of structure-specific mechanisms like the Diels-Alder click reaction. Additionally, the peculiar properties of some of these new macromolecular materials, such as poly(lactic acid), other polyesters, polyamides and polyurethanes, are highlighted to show, among other features, their unique applications, e.g. recyclability and self-mendability.
Uma breve discussão de como as origens da produção científica e filosófica proporcionaram o apagamento histórico dos registros intelectuais e científicos das mulheres.
Com base numa abordagem de Física Estatística, determinamos quais os elementos principais, células e sinalizadores (citocinas), que regem a dinâmica da resposta imune na fase crônica da infecção pelo Schistosoma Mansoni em humanos. A identificação destes elementos e da forma como interagem, permitiu-nos construir uma rede de interação entre estes elementos. Esta rede foi então analisada dentro de uma aproximação booleana, obtendo-se assim os atratores da dinâmica.