Valmar Carneiro Barbosa

Um aparato experimental para o estudo do princípio de Arquimedes

Recebido em 30/3/2005; Revisado em 8/9/2005; Aceito em 16/11/2005Neste trabalho apresentamos um aparato experimental para o estudo do principio de Arquimedes, assim comoa experiencia realizada com ele e uma sugestao de roteiro para esta experiencia que pode ser usado em aulas defisica experimental.Palavras-chave: empuxo, principio de Arquimedes, experiencia.We present an experimental apparatus to study the Archimedes’ principle and the experiment carried outwith this equipment. A laboratory guide to this experiment is also presented, which may be used in teachingexperimental physics.Keywords: buoyancy, Archimedes’ principle, experiment.

Uma descrição newtoniana do movimento de um pêndulo esférico

The physical system known as spherical pendulum is usually taken as an example of the applications of analytical mechanics. This deprives those people who had no contact with this approach to classical mechanics of the complete understanding of how this system behaves. So, in this work, we use Newtonian mechanics to present a study of the motion of a spherical pendulum. To do this, we obtain its equations of motion, determine the quantities that are conserved during the time evolution of this system, analyze its effective potential energy and discuss the different motions that this system can have. We present several numerical results, and a qualitative comparison with experimental data is made

O teorema dos eixos perpendiculares para um corpo rígido qualquer

We present the general form of the perpendicular axis theorem, which can be applied to any rigid body, and we obtain its version valid for any solid of revolution. We also present a particular case for right general cylinders. Some examples are given in order to show how the determination of moments of inertia of certain rigid bodies can be simplified if we use this theorem.

Uma visualização do princípio de Huygens-Fresnel na obtenção de um padrão de difração

Using the relation for the irradiance due to the interference of point sources, we show through graphs how the Huygens-Fresnel principle works when it is applied to determine the Fraunhofer diffraction pattern due to a normally incident plane wave on a single slit. In this way, we are able to identify the origins of the principal and secondary peaks of diffraction, which is not clearly understood from the analytical determination of the present diffraction pattern.

CHAPTER 29:Sucrose Determination by Raman Spectroscopy

Raman spectroscopy is one of the most versatile instrumental techniques currently used for structural characterisation. Although Raman spectroscopy is well-known as a powerful technique for the structural characterisation of several chemical compounds, its applications in the biomedical engineering field have increased significantly in recent years. Indeed, because of the identification of various fingerprint peaks, this technique can be employed for the biochemical analysis of several biological compounds and is commonly applied to diagnosis. In this context, Raman spectroscopy has been successfully used as an important tool for the determination of food contents. Spectral profiles of sucrose in different commercial forms are discussed in the present chapter as well as the employment of vibrational techniques to quantitative and physico-chemical analyses to obtain a well-defined characterisation of sucrose.

Giant Extracellular Hemoglobin of Glossoscolex paulistus: An excellent Prototype of Biosensor and Blood Substitute

Porphyrins and their metal complexes have been investigated for many years because the richness of the properties of these compounds is of interest to a wide range of scientific disciplines, from medicine to materials science (Figure 1). Metalloporphyrins in living systems play many functions that are essential for life, and the elucidation of both the geometric and electronic structures of these compounds is of extreme relevance to a detailed understanding of their roles in biological systems. Moreover, the possibility of mimicking the complex chemistry exhibited by metalloporphyrins in living organisms with synthetic models propitiates the possibility of exploiting then in a wide range of different applications, from medical diagnostics and treatments to catalysts and sensors (Walker, 2006). The heme groups (iron porphyrins) sites are involved in a range of biological functions. These roles are developed through various biochemical processes, such as electron transfer (e.g., cytochromes a, b, c, and f), in which the heme cycle between low-spin Fe(II) and lowspin Fe(III) small-molecule binding and transport, catalysis, and O2 activation (e.g. peroxidases and cytochromes P450), where high-valent iron centers are involved in several chemical reactions, such as hydrogen atom abstraction, hydroxylation, and epoxide formation (Figure 1). Heme sites are significantly different from non-heme iron sites in which the porphyrin ligand allows the delocalization of the iron d-electrons into the porphyrin π system. This distribution of electronic density changes the properties of the iron with respect to the flexibility of the central coordination site, the energetics of reactivity, and, consequently, to its biological function (Hocking et al., 2007).

The noninertial origin of the reduced mass

A different way to obtain the equation of motion that governs the relative motion in a two-particle system is presented. It provides the physical interpretation of the reduced mass as a noninertial effect.