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   PR # 22174
    We propose to observe the two X-ray bright, low-z,radio-quiet quasars
    PG1426+015 and MKN110, which showed in previous ROSAT PSPC observa-  
    tions a similar curved spectrum. Both sources show a strong soft     
    excess and a break between the soft and hard components in the "keV" 
    region, where the SIS sensitivity peaks. We will try to discriminate 
    between competing soft excess models. In particular, we will investi-
    gate whether the X-ray spectrum of these quasars contains signatures 
    of atomic transitions, which are predicted in many soft excess       
    thermal models, or, alternatively, it is better described by a smooth
    featureless continuum, as expected in non-thermal models,thus gaining
    information about the emission mechanisms of the soft X-ray compone  
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