Molecular Gas in Tidal Dwarf Galaxies: On-going Galaxy Formation

We investigate the process of galaxy formation as can be observed in the only currently forming galaxies -- the so-called Tidal Dwarf Galaxies, hereafter TDGs -- through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a {\it bona fide} galaxy. We have now detected CO in 9 TDGs with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few $10^8 M_\odot$. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H$_2$. Although uncertainties are still large for individual objects as the geometry is unknown, we find that the "dynamical" masses of TDGs, estimated from the CO line widths, do not seem to be greater than the "visible" masses (HI + H$_2$ + a stellar component), i.e., TDGs require no dark matter. We provide evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.Comment: 8 pages 4 figures, to be published in: Proceedings of the IAU Symposium 217: Recycling Intergalactic and Interstellar Matte

The turbomachine blading design using S2-S1 approach

The boundary conditions corresponding to the design problem when the blades being simulated by the bound vorticity distribution are presented. The 3D flow is analyzed by the two steps S2 - S1 approach. In the first step, the number of blades is supposed to be infinite, the vortex distribution is transformed into an axisymmetric one, so that the flow field can be analyzed in a meridional plane. The thickness distribution of the blade producing the flow channel striction is taken into account by the modification of metric tensor in the continuity equation. Using the meridional stream function to define the flow field, the mass conservation is satisfied automatically. The governing equation is deduced from the relation between the azimuthal component of the vorticity and the meridional velocity. The value of the azimuthal component of the vorticity is provided by the hub to shroud equilibrium condition. This step leads to the determination of the axisymmetric stream sheets as well as the approximate camber surface of the blade. In the second step, the finite number of blades is taken into account, the inverse problem corresponding to the blade to blade flow confined in each stream sheet is analyzed. The momentum equation implies that the free vortex of the absolute velocity must be tangential to the stream sheet. The governing equation for the blade to blade flow stream function is deduced from this condition. At the beginning, the upper and the lower surfaces of the blades are created from the camber surface obtained from the first step with the assigned thickness distribution. The bound vorticity distribution and the penetrating flux conservation applied on the presumed blade surface constitute the boundary conditions of the inverse problem. The detection of this flux leads to the rectification of the geometry of the blades

Osteoidosteom: CT-gesteuerte Bohrexzision und Radiofrequenzablation

Zusammenfassung: Hintergrund: Die CT-geführte Entfernung des Nidus eines Osteoidosteoms anstelle herkömmlicher Verfahren der offenen Resektion bietet den Vorteil, die Läsion intraoperativ exakt zu lokalisieren und deren Entfernung korrekt zu kontrollieren. Zudem tritt anstelle eines oft großen Eingriffs der Vorteil eines minimal-invasiven Vorgehens. Patienten und Methode: Zwischen 1996 und 2005 wurden 52Patienten anhand von Klinik und Bildgebung diagnostizierten Osteoidosteomen entweder mittels Bohrexzision (BE, n=41) oder Radiofrequenzablation (RFA, n=11) behandelt. Das Alter der Patienten lag zwischen 7 und 48 (Durchschnitt 22,3) Jahren, der Follow-up betrug 31,3Monate. Ergebnisse: Das Osteoidosteom konnte bei allen Patienten erfolgreich behandelt werden. 50Patienten waren nach einmaligem Eingriff anhaltend beschwerdefrei. Bei 2Patienten wurde in der 1. Operation der Nidus verfehlt, sodass kurze Zeit später mit der gleichen Methode eine 2. Behandlung notwendig wurde. Schlussfolgerung: Die CT-geführte Therapie des Osteoidosteoms hat dessen Behandlung durch exakte Lokalisierung und Verkleinerung des Eingriffs entscheidend vereinfacht und besser kontrollierbar gemacht. Das Verfahren kann analog zur Biopsie von Weichteil- und Knochenprozessen genutzt werden, was den Vorteil der exakten Dokumentation des Biopsieweges und der Entnahmestelle biete