Orbital properties of binary post-AGB stars

Binary post-asymptotic giant branch (post-AGB) stars are thought to be the products of a strong but poorly-understood interaction during the AGB phase. The aim of this contribution is to update the orbital elements of a sample of galactic post-AGB binaries observed in a long-term radial-velocity monitoring campaign. Radial velocities are computed from high signal-to-noise spectra by use of a cross-correlation method. The radial-velocity curves are fitted by using both a least-squares algorithm and a Nelder-Mead simplex algorithm. We use a Monte Carlo method to compute uncertainties on the orbital elements. The resulting mass functions are used to derive a companion mass distribution by optimising the predicted to the observed cumulative mass-function distributions, after correcting for observational bias. As a result, we derive and update orbital elements for 33 galactic post-AGB binaries, among which 3 are new orbits. The orbital periods of the systems range from 100 to about 3000 days. Over 70 percent (23 out of 33) of our binaries have significant non-zero eccentricities ranging over all periods. Their orbits are non-circular despite the fact that the Roche-lobe radii are smaller than the maximum size of a typical AGB star and tidal circularisation should have been strong when the objects were on the AGB. We derive a distribution of companion masses that is peaked around 1.09 $M_\odot$ with a standard deviation of 0.62 $M_\odot$. The large spread in companion masses highlights the diversity of post-AGB binary systems. Furthermore, we find that only post-AGB stars with high effective temperatures (> 5500 K) in wide orbits are depleted in refractory elements, suggesting that re-accretion of material from a circumbinary disc is an ongoing process. It appears, however, that chemical depletion is inefficient for the closest orbits irrespective of the actual surface temperature.Comment: 21 pages total, 3 appendices, 8 figures excluding appendix figures, 3 table

Disc-binary interactions in depleted post-AGB binaries

Binary post-asymptotic giant branch (post-AGB) stars have orbital periods in the range of 100--2500 days in eccentric orbits. They are surrounded by circumbinary dusty discs. They are the immediate result of unconstrained binary interaction processes. Their observed orbital properties do not correspond to model predictions: Neither the periods nor the high eccentricities are expected. Our goal is to investigate if interactions between a binary and its circumbinary disc during the post-AGB phase can result in their eccentric orbits, while simultaneously explaining the chemical anomaly known as depletion. For this paper, we selected three binaries (EP Lyr, RU Cen, HD 46703) with well-constrained orbits, luminosities, and chemical abundances. We used the MESA code to evolve post-AGB models, while including the accretion of metal-poor gas. This allows us to constrain the evolution of the stars and study the impact of circumbinary discs on the orbital properties of the models. We investigate the effect of torques produced by gas inside the binary cavity and the effect of Lindblad resonances on the orbit, while also including the tidal interaction following the equilibrium tide model. We find that none of our models are able to explain the high orbital eccentricities of the binaries in our sample. The accretion torque does not significantly impact the binary orbit, while Lindblad resonances can pump the eccentricity up to only $e \approx 0.2$. At higher eccentricities, the tidal interaction becomes too strong, so the high observed eccentricities cannot be reproduced. However, even if we assume tides to be ineffective, the eccentricities in our models do not exceed $\approx 0.25$. We conclude that either our knowledge of disc-binary interactions is still incomplete, or the binaries must have left their phase of strong interaction in an eccentric orbit.Comment: 17 pages + 8 pages appendix, 12 figures, accepted for publication in Astronomy and Astrophysic

Uncertainty Work:Dealing with a Psychiatric Crisis in Two European Community Mental Health Teams

The quest for how to deal with a crisis in a community setting, with the aim of deinstitutionalizing mental health care, and reducing hospitalization and coercion, is important. In this article, we argue that to understand how this can be done, we need to shift the attention from acute moments to daily uncertainty work conducted in community mental health teams. By drawing on an empirical ethics approach, we contrast the modes of caring of two teams in Utrecht and Trieste. Our analysis shows how temporality structures, such as watchful waiting, are important in dealing with the uncertainty of a crisis.</p

Uncertainty Work:Dealing with a Psychiatric Crisis in Two European Community Mental Health Teams

The quest for how to deal with a crisis in a community setting, with the aim of deinstitutionalizing mental health care, and reducing hospitalization and coercion, is important. In this article, we argue that to understand how this can be done, we need to shift the attention from acute moments to daily uncertainty work conducted in community mental health teams. By drawing on an empirical ethics approach, we contrast the modes of caring of two teams in Utrecht and Trieste. Our analysis shows how temporality structures, such as watchful waiting, are important in dealing with the uncertainty of a crisis.</p

Working on and with Relationships: Relational Work and Spatial Understandings of Good Care in Community Mental Healthcare in Trieste

Deinstitutionalization is often described as an organizational shift of moving care from the psychiatric hospital towards the community. This paper analyses deinstitutionalization as a daily care practice by adopting an empirical ethics approach instead. Deinstitutionalization of mental healthcare is seen as an important way of improving the quality of lives of people suffering from severe mental illness. But how is this done in practice and which different goods are strived for by those involved? We examine these questions by giving an ethnographic description of community mental health care in Trieste, a city that underwent a radical process of deinstitutionalization in the 1970s. We show that paying attention to the spatial metaphors used in daily care direct us to different notions of good care in which relationships are central. Addressing the question of how daily care practices of mental healthcare outside the hospital may be constituted and the importance of spatial metaphors used may inform other practices that want to shape community mental health care

Vitamin D: A modulator of cell proliferation and differentiation

Abstract 1,25-Dihydroxyvitamin D3, [1,25(OH)2D3], the biologically most active metabolite of vitamin D3, is involved in the regulation of calcium homeostasis and bone metabolism. Recently, receptors for 1,25(OH)2D3 have also been shown in cells and tissues not directly related to calcium homeostasis. Experimental data obtained with leukemic and cancer cell lines, both in vitro and in vivo, showed the effects of 1,25(OH)2D3 on cell differentiation and proliferation. However, high doses of the sterol have to be used to observe these effects. Additional studies are needed to establish whether 1,25(OH)2D3 or suitable analogues have a therapeutic potential in malignant diseases without unacceptable toxicity like the development of hypercalcemia