University of Graz

About: University of Graz is a education organization based out in Graz, Steiermark, Austria. It is known for research contribution in the topics: Population & Context (language use). The organization has 17934 authors who have published 37489 publications receiving 1110980 citations. The organization is also known as: Carolo Franciscea Graecensis & Karl Franzens Universität.

Roche lobe effects on the atmospheric loss from "Hot Jupiters"

Abstract: Context. A study of the mass loss enhancement for very close “Hot Jupiters” due to the gravitational field of the host star is presented. Aims. The influence of the proximity to a planet of the Roche lobe boundary on the critical temperature for blow-off conditions for estimating the increase of the mass loss rate through hydrodynamic blow-off for close-in exoplanets is investigated. Methods. We consider the gravitational potential for a star and a planet along the line that joins their mass centers and the energy balance equation for an evaporating planetary atmosphere including the effect of the stellar tidal force on atmospheric escape. Results. By studying the effect of the Roche lobe on the atmospheric loss from short-periodic gas giants we derived reasonably accurate approximate formulas to estimate atmospheric loss enhancement due to the action of tidal forces on a “Hot Jupiter” and to calculate the critical temperature for the onset of “geometrical blow-off”, which are valid for any physical values of the Roche lobe radial distance. Using these formulas, we found that the stellar tidal forces can enhance the hydrodynamic evaporation rate from TreS-1 and OGLE-TR-56b by about 2 fold, while for HD 209458b we found an enhancement of about 50%. For similar exoplanets which are closer to their host star than OGLE-TR-56b, the mass loss enhancement can be even larger. Moreover, we showed that the effect of the Roche lobe allows “Hot Jupiters” to reach blow-off conditions at temperatures which are less than expected due to the stellar X-ray and EUV heating.

An AIF orthologue regulates apoptosis in yeast

Abstract: Apoptosis-inducing factor (AIF), a key regulator of cell death, is essential for normal mammalian development and participates in pathological apoptosis. The proapoptotic nature of AIF and its mode of action are controversial. Here, we show that the yeast AIF homologue Ynr074cp controls yeast apoptosis. Similar to mammalian AIF, Ynr074cp is located in mitochondria and translocates to the nucleus of yeast cells in response to apoptotic stimuli. Purified Ynr074cp degrades yeast nuclei and plasmid DNA. YNR074C disruption rescues yeast cells from oxygen stress and delays age-induced apoptosis. Conversely, overexpression of Ynr074cp strongly stimulates apoptotic cell death induced by hydrogen peroxide and this effect is attenuated by disruption of cyclophilin A or the yeast caspase YCA1. We conclude that Ynr074cp is a cell death effector in yeast and rename it AIF-1 (Aif1p, gene AIF1).