This article offers a brief account of the theoretical path taken by Thomas Hobbes in connection with his theories of light and visual perception. It is intended to show that the succession of optical theories elaborated by Hobbes, during the period 1630 to 1658, moves in the direction of a growing mechanization and articulation of the “external” and “internal” aspects that come together for the production of sensation. The Hobbesian doctrine of vision seems to have been the only theory available in the first half of the seventeenth century sought to formulate a complete and unified explanation of the mechanism of sensory perception, or to reduce it entirely to the effects of “local movement”

Dry microwave imaging (MWI) systems are more practical, hygienic, and fast to operate since they do not require immersion liquid. However, the dielectric contrast between air and the part of the body under examination is larger, causing larger refraction effects. Including refraction in the image reconstruction algorithm significantly increases the computational effort, especially when imaging nonuniform shapes. Hence, our systematic study aims to evaluate the impact of neglecting refraction effects on MWI by using quantitative metrics and define objective guidelines that are lacking in the literature. We perform comparative studies with a spherical numerical phantom (which is typically used to represent simplified breast or head phantoms) by varying the phantom relative permittivity values between 4 and 40, metallic targets diameter between 5 and 15 mm, and the number of probing antennas. Additionally, the refraction effects are evaluated with anthropomorphic body phantoms representing a breast and the axillary region. We numerically and experimentally show that refraction tends to have a greater impact on imaging results when phantom relative permittivity values exceed 8, while it has a minor effect in the remaining tested cases. This favors potential fast real-time image reconstruction. This letter provides useful criteria to decide whether refraction should be considered or not for imaging reconstruction when developing new dry medical MWI setups.

Abstract When a swimming pool is filled with water, the tiles covering its walls appear to have smaller vertical dimensions than the real ones, due to the refraction of light from the water into the air. This condition was used to find the refractive index of water, using a trigonometric equation developed from a geometrical model. The necessary measurements were made with a common ruler and the average value obtained for the refractive index was very close to the real one, favoring the didactic potential of this experimental activity.

When a watch is submerged in water, an observer might come to realize that the glass surface appears silver, like a mirror, due to internal reflection. However, it is not possible to clearly identify in which surface - internal or external - this reflection occurs. An experimental variation is proposed, using a thicker glass, allowing better identification of the inner surface as the reflector, along with hints for qualitative and quantitative discussions.

Abstract The phenomena of reflection and refraction of plane waves incident obliquely at a plane interface between uniform elastic solid half-space and porous solid containing liquid filled bound pores and two-phase fluid in connected pores has been analyzed. The amplitude ratios of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used further to derive the expressions for the partition of incident energy among the reflected and refracted waves. Partition of incident energy among the reflected and refracted waves is studied for incidence of P and SV waves. The conservation of the energy across the interface is verified. The effect of gas saturation, wave frequency, capillary pressure and bound liquid film on the amplitude ratios and energy partitions are studied in the numerical example.

O cálculo do gradiente da função objetivo sempre foi a etapa mais custosa da tomografia sísmica de refração. Com a finalidade de reduzir este custo, o método do estado adjunto vem sendo estudado como uma alternativa aos métodos tradicionais de cálculo do gradiente, como o traçado de raios. Este método trata o cálculo do gradiente da função objetivo como uma otimização não linear, tornando o custo da obtenção do gradiente equivalente ao de mais uma solução do problema direto. Este método, porém, apresenta uma dificuldade quando se trata de regularização, uma vez que não é obtida a matriz de sensibilidade. Neste estudo realizou-se testes com técnicas de regularização convolucionais a fim de verificar a eficácia do método sob estes regularizadores. Foram realizadas tomografias de refração a partir de dados obtidos por meio de modelos sintéticos e os resultados foram analisados a fim de confirmar a estabilidade oferecida por estas técnicas de regularização

This article presents the Bakhtin's notion of Dialogism as a tool used to identification/interpretation of possible contents refracted in musical works. To this end, a dialogical analysis was realized of the LP Quarteto Novo (1967), which is considered a milestone in the history of Brazilian instrumental music, aiming to point out possible refracted contents in the compositional constructions and style of this LP. This reflection, based on the Bakhtin's theory, allows us to ascertain the influence of the various fields of human activity on musical works. This is a cut from the master's dissertation in progress of the author.

To evaluate and compare the changes in refraction and effective intraocular lens (IOL) position between a plate-haptic IOL and a c-loop single-piece IOL after neodymium-doped yttrium aluminium garnet (YAG) laser posterior capsulotomy.