Dielektrika

Fyzika normálních dielektrik

Bernhard Gross (1905 - 2002)

    Bernhard Gross arrived in Rio de Janeiro in Brazil in 1933. He was a young physicist from Stuttgart, full of enthusiasm and creativity. He was in Brazil also when he was a child, and perhaps the image of this tropical and mysterious country lingered in his mind ever since. Today, with jets crossing the oceans within a few hours, one cannot imagine what it meant to go to another continent. Travel was possible only by sea and it would take weeks for mail to reach Brazil from Europe. Bernhard Gross learned his Portuguese only after arriving in Brazil. After one year, in 1934, he was already doing his research and publishing a paper on cosmic radiation in the Annals of the Brazilian Academy of Science.
    In the theory of dielectrics, where he excelled as he did in other areas, not only formal results that Gross obtained were fundamental from a mathematical standpoint, but he also proceeded to accomplish many of the more important experimental confirmation of such concepts as the theory of dielectric absorption, thermally stimulated currents and voltages, electrets, and related subjects. In the course of his work, he laid the groundstones to modern electret research.
    Gross influenced many young scientists in Brazil, and soon created a veritable school in Rio, with j. Costa Ribeiro, P. Rocha, A. D. Tavares, O. Castro, and others of that generation. In 1950s he inspired Costa Ribeiro who found thermodielectric effect, the occurrence of currents and voltages during phase transition in dielectrics. Gross also noticed that the formalism of dielectric and viscoelastic relaxations are identical. He therefore applied the methods he had developed to viscoelasticity, discovering a new integral transform sometimes referred to as second Gross transform (the first Gross transform relates the absorption of unidirectional and isotropic beams of radiation and was used extensively for the description of the mechanical behavior of elastic materials.

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Fig. 1 - Bernhard Gross

    Bernhard Gross was also one of the first to understand the famous Dirac delta function from the standpoint of integral analysis. He also introduced the concept of the bioelectret and investigated the presence of electrets in biological systems. For seven years, he was Director of the Division of Scientific and Technological Information of the International Atomic Energy Agency (IAEA) in Vienna. Gross introduced the concept of Compton currents and proved their existence experimentally. With that result, he was able to propose and build the Compton dosimeter, now in wide use for high radiation fields.
    He never loses his interest in all subjects, from music to literature, the international situation, cinema and of course science.

REFERENCES:
Mascarenhas, S.: Bernhard Gross and his Contribution to Physics in Brazil. Brazilian Journal of Physics, 1999, roč. 29, č. 2, s. 217-219
Sessler, G. M.: Bernhard Gross and the Evolution of Modern Electret Research. Brazilian Journal of Physics, 1999, roč. 29, č. 2, s. 220-225


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