Thermal diffusivity of periderm from tomatoes of different maturity stages as determined by the concept of the frequency-domain open photoacoustic cell

The frequency-domain open photoacoustic cell (OPC) approach was used to determine room temperature thermal diffusivity of skins (pericarps) from the raw tomatoes (Lycopersicon esculetum Mill.) characterized by the three different stages of ripeness (from immature-green to a mature-red). Periodically interrupted 532 nm laser radiation was used to heat the dry tomato skins, typically 10 mm in diameter and up to 68 µm thick; the modulating frequency f varied from 8 to 150 Hz. Initially, a combined OPC-model that takes into account both, the thermoelastic bending and the effect of thermal diffusion (TD), has been applied. Preliminary results showed that until at least 40 Hz, the effect of TD dominates; above this value the combined model fits the experimental data only poorly. For this reason a less complex OPC-TD approach was applied to all investigated skins instead, which predicts an exponential decrease for the amplitude of measured photoacoustic signal S with increasing f. For a specimen that is simultaneously opaque and thermally thick, S depends on f as S~exp(-b f1/2) where b is a fitting parameter. The S versus f plot enables one to deduce the numerical value for b which, on its turn allows for the assessment of skin’s thermal diffusivity a. Thermal diffusivities obtained for the immature green, orange, and red skins (periderms) are 9.9×10-8 m2¿s-1, 7.2×10-8 m2¿s-1, and 4.6×10-8 m2¿s-1, respectively; the uncertainty was typically 5% of the measured value

Thermal lens spectrometry to study complex fluids

We describe applications of Thermal Lens Spectrometry to study optical and thermal properties of lyotropic liquid crystal. In particular, we refer to methods for measurements of thermal diffusivity anisotropy at different temperatures and as a function of the ferrofluids doping. The theoretical basis for quantitative measurements is discussed together with the advantages and limitations as compared with conventional methods. Finally, future developments of photothermal techniques for these applications are assessed.0000Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Ultrasound Methods for Biodiesel Production and Analysis

Ultrasonic techniques have been widely used in biodiesel production, since the acoustic cavitation is a phenomenon capable of accelerating potentially the transesterification reactions. The equipment employed in such approach was simply equipment available in any regular laboratory of chemistry. Further developments introduced the ultrasound as an important tool to produce biodiesel. The main advantage is increasing the conversion of esters at reduced reaction times, with significantly lower production costs. As a method for characterization and analysis of materials, ultrasound has been used since several decades ago. However, ultrasonic analytical methods based on metrological principles are fairly recent investigated. Using ultrasound as physical principle to interrogate biodiesel is a promising field of research, with some remarkable outcomes produced so far. The aim of this chapter is to demonstrate advances of using ultrasonic techniques in production and characterization of biodiesel, as well as an appraisal of the current technology status, and provide insights into future developments

Re-carbonized vitreous carbon substrates for optical applications

Imaging optical systems components for satellites must have low specific mass and high stiffness, as weight is a problem for payloads and stiffness is essential to keep the substrate front surface shape. In this work, Re-carbonized Vitreous Carbon (RVC) was tested as a substrate material. The process to obtain RVC is different from the traditional process to obtain the Monolithic Vitreous Carbon (MVC). It is essential to understand the process to evaluate the surface roughness data. This work describes the process to obtain RVC, as a candidate for optical component substrate, and the results of its surface roughness measurements60523rd Congress of the International Commission for Optics (ICO

Glucose tolerance is negatively associated with circulating progenitor cell levels

n/

The CMS RPC gas gain monitoring system: an overview and preliminary results

The status of the CMS RPC Gas Gain Monitoring (GGM) system developed at the Frascati Laboratory of INFN (Istituto Nazionale di Fisica Nucleare) is reported on. The GGM system is a cosmic ray telescope based on small RPC detectors operated with the same gas mixture used by the CMS RPC system. The GGM gain and efficiency are continuously monitored on-line, thus providing a fast and accurate determination of any shift in working point conditions. The construction details and the first result of GGM commissioning are described.Comment: 8 pages, 9 figures, uses lnfprepCMS.sty, presented by L. Benussi at RPC07, Mumbai, INDIA 200

Influence of Edge Effects on Laser-Induced Surface Displacement of Opaque Materials by Photothermal Interferometry

We demonstrate the influence of edge effects on the photothermal-induced phase shift measured by a homodyne quadrature laser interferometer and compare the experiments with rigorous theoretical descriptions of thermoelastic surface displacement of metals. The finite geometry of the samples is crucial in determining how the temperature is distributed across the material and how this affects the interferometer phase shift measurements. The optical path change due to the surface thermoelastic deformation and thermal lens in the surrounding air is decoded from the interferometric signal using analytical and numerical tools. The boundary/edge effects are found to be relevant to properly describe the interferometric signals. The tools developed in this study provide a framework for the study of finite size effects in heat transport in opaque materials and are applicable to describe not only the phase shift sensed by the interferometer but also to contribute to the photothermal-based technologies employing similar detection mechanisms