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The gravitationally lensed quasar Q2237+0305 in X-rays: ROSAT/HRI detection of the "Einstein Cross"
(1999)
We report the first detection of the gravitationally lensed quasar Q2237+0305 in X-rays. With a ROSAT/HRI exposure of 53 ksec taken in Nov./Dec. 1997, we found a count rate of 0.006 counts per second for the combined four images. This corresponds to an X-ray flux of 2.2*E(-13) erg/cm(2) /sec and an X-ray luminosity of 4.2*E(45) erg/sec (in the ROSAT energy window 0.1-2.4 keV). The ROSAT/HRI detector is not able to resolve spatially the four quasar images (maximum separation 1.8 arcsec). The analysis is based on about 330 source photons. The signal is consistent with no variability, but with low significance. This detection is promising in view of the upcoming X-ray missions with higher spatial/spectral resolution and/or collecting power (Chandra X-ray Observatory, XMM and ASTRO-E).
Three studies examined the processes of mental model generation after pre-exposure to uncontrollability and in a depressive state. The main purpose of the experiments was to test the implications of the cognitive exhaustion model applying an explicit conceptualization of social mental models and a process tracing method developed by von Hecker (1997). An experimental situation was created for observation of consecutive, rule-based construction steps as a function of input diagnosticity, and for the quality assessment of the constructed mental model. The findings showed that participants pre-exposed to uncontrollability, as well as depressed students, were able as were controls, to identify rule-relevant information needed for model construction. However, they were less able than controls to engage in more cognitively demanding and generative step of processing , i.e. in integrating the pieces of input information into a coherent mental model of sentiment relations.
Si(1-x)Ge(x) laterally graded crystals as monochromators for X-Ray absorption spectroscopy studies
(1999)