TY  - JOUR
A1  - Sandin, C.
A1  - Steffen, M.
A1  - Schoenberner, D.
A1  - Rühling, Ute
T1  - Hot bubbles of planetary nebulae with hydrogen-deficient winds I. Heat conduction in a chemically stratified plasma
JF  - Frontiers in psychology
N2  - Heat conduction has been found a plausible solution to explain discrepancies between expected and measured temperatures in hot bubbles of planetary nebulae (PNe). While the heat conduction process depends on the chemical composition, to date it has been exclusively studied for pure hydrogen plasmas in PNe. A smaller population of PNe show hydrogen-deficient and helium-and carbon-enriched surfaces surrounded by bubbles of the same composition; considerable differences are expected in physical properties of these objects in comparison to the pure hydrogen case. The aim of this study is to explore how a chemistry-dependent formulation of the heat conduction affects physical properties and how it affects the X-ray emission from PN bubbles of hydrogen-deficient stars. We extend the description of heat conduction in our radiation hydrodynamics code to work with any chemical composition. We then compare the bubble-formation process with a representative PN model using both the new and the old descriptions. We also compare differences in the resulting X-ray temperature and luminosity observables of the two descriptions. The improved equations show that the heat conduction in our representative model of a hydrogen-deficient PN is nearly as efficient with the chemistry-dependent description; a lower value on the diffusion coefficient is compensated by a slightly steeper temperature gradient. The bubble becomes somewhat hotter with the improved equations, but differences are otherwise minute. The observable properties of the bubble in terms of the X-ray temperature and luminosity are seemingly unaffected.
KW  - conduction
KW  - hydrodynamics
KW  - planetary nebulae: general
KW  - stars: AGB and post-AGB
KW  - stars: Wolf-Rayet
KW  - X-rays: stars
Y1  - 2016
U6  - https://doi.org/10.1051/0004-6361/201527357
SN  - 1432-0746
VL  - 586
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Distelmeyer, Jan
T1  - From object to process
BT  - Interface politics of networked computerization
JF  - Artnodes
N2  - One of the most difficult tasks today is trying to grasp the presence of computing. The almost ubiquitous and diverse forms of networked computers (in all their stationary, mobile, embedded, and autonomous modes) create a nearly overwhelming complexity. To speak of what is here evading and present at the same time, the paper proposes to reconsider the concept of interface, its historical roots, and its heuristic advantages for an analysis and critique of the current and especially everyday spread of computerization. The question of interfaces leads to isolable conditions and processes of conduction, as well as to the complexity of the cooperation formed by them. It opens both an investigative horizon and a mode of analysis, which always asks for further interface levels involved in the phenomenon I am currently investigating. As an example, the paper turns to the displacement of the file with the launch of the iPhone in 2007 and its comeback in 2017 with the "Files" apps. Both developments are profoundly related to the establishment of computers as permanently networked machines, whereby their functionality, depresentations, and ideology come into focus.
KW  - interface
KW  - conduction
KW  - network
KW  - ideology
KW  - depresentation
KW  - digital objects
Y1  - 2019
U6  - https://doi.org/10.7238/a.v0i24.3300
SN  - 1695-5951
IS  - 24
SP  - 83
EP  - 90
PB  - Universitat Oberta de Catalunya
CY  - Barcelona
ER  -