Large granulation cells on the surface of the giant star π1 Gruis.

Convection plays a major part in many astrophysical processes, including energy transport, pulsation, dynamos and winds on evolved stars, in dust clouds and on brown dwarfs. Most of our knowledge about stellar convection has come from studying the Sun: about two million convective cells with typical sizes of around 2,000 kilometres across are present on the surface of the Sun-a phenomenon known as granulation. But on the surfaces of giant and supergiant stars there should be only a few large (several tens of thousands of times larger than those on the Sun) convective cells, owing to low surface gravity. Deriving the characteristic properties of convection (such as granule size and contrast) for the most evolved giant and supergiant stars is challenging because their photospheres are obscured by dust, which partially masks the convective patterns. These properties can be inferred from geometric model fitting, but this indirect method does not provide information about the physical origin of the convective cells. Here we report interferometric images of the surface of the evolved giant star π1 Gruis, of spectral type S5,7. Our images show a nearly circular, dust-free atmosphere, which is very compact and only weakly affected by molecular opacity. We find that the stellar surface has a complex convective pattern with an average intensity contrast of 12 per cent, which increases towards shorter wavelengths. We derive a characteristic horizontal granule size of about 1.2 × 1011 metres, which corresponds to 27 per cent of the diameter of the star. Our measurements fall along the scaling relations between granule size, effective temperature and surface gravity that are predicted by simulations of stellar surface convection.

The cost of cytoreductive surgery and perioperative intraperitoneal chemotherapy in the treatment of peritoneal malignancy in one Greek institute.

PURPOSE: Cytoreductive surgery and perioperative intraperitoneal chemotherapy in the treatment of patients with peritoneal malignancy is expensive. The purpose of this study was to estimate the current cost of cytoreductive surgery combined with perioperative intraperitoneal chemotherapy and identify the most significant related parameters in one center in Greece. METHODS: A retrospective economic study was carried out on 105 patients that underwent 108 cytoreductive operations and hyperthermic intraoperative peritoneal chemotherapy (HIPEC) from 2006-2011 for peritoneal malignancy. The economic cost included the daily cost of hospital bed occupancy, the daily cost of occupancy in the intensive care unit (ICU), the expenditures (materials and drugs), and the preoperative, intraoperative, and postoperative examinations. RESULTS: The mean length of stay in the ICU and the mean hospitalization time was 5 and 23 days, respectively. The hospital mortality and morbidity was 5.6% (6 patients) and 48.17percnt; respectively. The mean cost of treatment was 15677.3±11910.6 euros (range=4258,47-95990,87) per patient. Morbidity (p=0.009), and prolonged stay in the ICU (p<0.001) were the parameters that influenced independently the cost of treatment. CONCLUSION: Cytoreductive surgery combined with perioperative intraperitoneal chemotherapy is an expensive treatment. The economic cost is largely influenced by morbidity and the length of stay in the ICU.

Orbital complexity, short-time Lyapunov exponents, and phase space transport in time-independent Hamiltonian systems.

This paper compares two alternative characterizations of chaotic orbit segments, one based on the complexity of their Fourier spectra, as probed by the number of frequencies n(k) required to capture a fixed fraction k of the total power, and the other based on the computed values of short-time Lyapunov exponents chi. An analysis of orbit ensembles evolved in several different two- and three-dimensional potentials reveals that there is a strong, roughly linear correlation between these alternative characterizations, and that computed distributions of complexities, N[n(k)] and short-time chi, N[chi] often assume similar shapes. This corroborates the intuition that chaotic segments which are especially unstable should have Fourier spectra with particularly broad-band power. It follows that orbital complexities can be used as probes of phase space transport and other related phenomena in the same manner as can short-time Lyapunov exponents.