Luiz Miranda

Page 1. Z Lebensm Unters Forsch (1995) 201:236 240 Zeitschriftf~r Lebensmittei o und-Forschung 9 Springer-Verlag 1995 Original paper The influence of slaked lime content on the processing conditions of cooked maize tortillas: changes of thermal, ...

In this work we are proposing a new experimental configuration based in the use of two sensors to allow the simultaneous measurement of both thermal diffusivity and effusivity of the sample. This Dual Sensor Photopyroeletric - DSPPE configuration implies in a single experiment and any calibration is required. Temperature dependent experiments are allowed from a cell equipped with Peltier elements. Substituting the upper sensor for a quartz window spectroscopic experiments are permitted. Water and margarine with different fat content were used as testing samples. (Received on June 29, 2000 accepted on October 30, 2000) Photopyroeletric - PPE schemes have been used in the determination of the dynamic (diffusivity α, effusivity e and conductivity k) and static (specific heat c) thermal properties of liquid and pasty materials (01-06). Two main configurations have been usually employed, namely the SPPE (Standard or Back) and the IPPE (Inverse or Front), depending upon which surface the modulated incident light reaches first, of the sample or of the pyroeletric sensor, respectively. For some specific thermal and optical features of sample and sensor, usually one obtains the thermal diffusivity α from an experiment using the SPPE configuration (which serves also for spectroscopic purposes) and the thermal effusivity e from an experiment using the IPPE configuration. In the last case it is still necessary to calibrate the experiment using a standard, usually water. Being in possession of α and e data one can obtain the value for the thermal conductivity k from α = e k and that for the

... 463, (1999) 339; CAS Lima, et al., Meas. Sci. Technol. 11 (2000) 504. 9. CAS Lima, MMS Lima, LCM Miranda, R. Oliva, G. Car-denas, Chem. Phys. Lett. 332 (2000) 8. 10. AN Adamson, A. Gast, Physical Chemistry of Surfuces ,(J. Wiley & Sons, New York, 1997). Rev. Mex. Fıs. ...

The effect of a laser field on the inelastic scattering of electrons by one-electron ions in a dense plasma is investigated. The total cross-sections for 1s-2s and 1s-2p transitions are calculated. The laser field modifies the cross-sections by lowering the energy threshold, introducing an anisotropy with respect to the laser polarization, and giving rise to a non-monotonic dependence on the electron energy which is characteristic of multiphoton process. Pages: 612-620

A simple molecular-field model taking into account the characteristic volume distribution of an assembly of magnetically ordered microcrystals is developed to explain the observed high-temperature behaviour of the magnetisation. It is also shown that the volume distribution implies a distribution of critical temperatures.

ABSTRACT In this paper we describe the use of so‐called open‐photoacoustic cell (OPC) for thermal characterization of transparent liquid samples. The samples used to demonstrate the usefulness of the OPC configuration are water, glycerol, and diffusion pump oil.

Combined photoacoustic and impedance spectroscopy (PA/LCR) experiments on different types of papers and bleached wood pulp were carried out to determine thermal diffusivity, dielectric constant and electrical conductivity and correlate them to bleaching parameters. Results are presented and discussed in view of a possible ansatz for PA/LCR based determination of said parameters.

The rate of change in the acoustic phonon population due to scattering by conduction electrons in the presence of two laser fields is calculated. It is found that longitudinal acoustic waves propagating parallel to the direction of polarisation of the radiation fields may be amplified over a relatively narrow frequency range.