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Kirchhoff's law has caused confusion in the discussion about the theoretical maximum work from radiation because it permits only infinitesimal or irreversible absorption. With the aid of an optical circulator, non-Kirchhoff behaviour is possible in principle which permits at the same time complete and reversible radiation absorption. The key to overcome Kirchhoff's law seems to be the magnetic field, a condition explicitly excluded by Kirchhoff. The work extracted in complete reversible conversion of radiation is calculated. The irreversibilities connected with the emission process are discussed. [ABSTRACT FROM AUTHOR]

Endothermic chemical reactions taking place at temperatures above 1000 K are candidates for the utilization of solar energy in highly concentrating solar furnaces. Special interest is focussed onto the question of whether light drives the reaction differently from heat. To observe such an effect it is important to monitor the chemical process of the sample under irradiation. In this paper we propose spectral reflectivity as a probe for chemical changes. We present laboratory measurements showing reflectivity changes associated with the oxidation of magnetite. We observed significant changes at temperatures coinciding with the oxidation temperature of magnetite. We further observed a change of the reflectivity associated with the phase transition of maghemite to hematite. Contrary to the literature, we find that this phase transition leads off at about 525 K. [ABSTRACT FROM AUTHOR]

The formalism for fragment angular distributions in photofission with unpolarized and linearly polarized photons is summarized. First experiments onTh using linearly polarized bremsstrahlung are described. The results for the analyzing power show for the first time in a model independent way that the low energy photofission can be explained by electric dipole excitation. The possibilities of this new method are discussed, in particular when using monoenergetic tagged photons, which are available soon at new high duty cycle electron accelerators. [ABSTRACT FROM AUTHOR]

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This article presents information on detection of pneumocystis carinii DNA in patients with chronic lung diseases. Pneumocystis carinii is an opportunistic fungal pathogen causing pneumonia in severely ill, malnourished and immunocompromised individuals, principally AIDS patients. Pneumocystis carinii pneumonia is a very rare event in immunocompetent adults. Serological studies, however, show a high prevalence of Pneumocystis carinii-specific antibodies, suggesting early infection in childhood and a high rate of infection throughout the population.

The comparison of fission fragment angular distributions in electron- and positron-induced fission is proposed as a new method to test virtual photon spectra. The sensitivity of this technique is shown by first experiments onTh (bombarding energy: 9 and 16 MeV). [ABSTRACT FROM AUTHOR]