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GSI-Nachrichten 01-1999
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Ion implantation improves performance of knee joint prostheses
Industrial application planned
The tribological properties of materials, i.e. the wear resistance of the surface
layers, can considerably be improved by means of ion implantation. A promising application
of this technique is the surface modification of titanium alloys which are widely used
for medical products, such as orthopaedic endo-prostheses. For titanium-based knee joint
prostheses the wear and friction could be dramatically reduced after implantation of
carbon or nitrogen ions. The investigations were performed in close cooperation with
a medical company which plans to exploit the techniques for large-scale production.
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The long-term wear resistance of the implanted titanium surface was
demonstrated, using a knee joint simulator of Aesculap AG Tuttlingen. The picture was
taken at the Hannover Fair 1998 and shows the Hessian Ministerpräsident Hans Eichel
informing himself about the project.
Enhanced out-of-plane emission of K+ mesons in relativistic heavy- ion reactions
Further evidence for the predicted repulsive K+ nucleon potential in nuclear matter
New data from the KAOS spectrometer at GSI reveal an azimuthally anisotropic
distribution of K+ mesons in relativistic gold-gold collisions. In peripheral and
semi-central collisions, K+ mesons are preferentially emitted perpendicular to the
reaction plane. The results are consistent with the theoretical prediction of a
repulsive K+ nucleon potential in nuclear matter.
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Geometrical aspects of a relativistic heavy-ion collision event (in the center of mass
frame). In the present experiment, the azimuthally anisotropic K+ emission was measured
for gold-gold collisions at 1 AGeV.
First search for element 113 shows no event
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Plot of production cross sections for cold fusion reactions of 208Pb or
209Bi with various projectiles. Full symbols are measured cross sections, open symbols
correspond to extrapolations. The solid lines are fits for different values of Tz=(N-Z)/2.
For the production of element 113, an upper limit of 0.6 pb was deduced.
Liquid-gas phase transition in finite nuclei
Simulations in Fermionic Molecular Dynamics
The forces between the individual nucleons in a nucleus vary according to distance in a
manner similar to those between molecules in a liquid. Thus the interesting question
arises, whether with increasing excitation energy a liquid-gas phase transition can be
observed in finite nuclei. Generally it is believed that signatures of phase transitions
are washed out in systems with few constituents due to finite size effects. Theoretical
simulations show, however, that even small systems exhibit all features of a phase
transition, provided the total energy of the system can be determined well enough for
each member of the statistical ensemble. The results are compared to the caloric curve
deduced for finite nuclei by the ALADIN collaboration.
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Snapshots of an excited 16O
Proposal for a dedicated ion- beam facility for cancer therapy
Based on the successful pilot project at GSI, the
Radiologische Universitätsklinik Heidelberg, the Deutsches Krebsforschungszentrum
Heidelberg (DKFZ) and the Gesellschaft für Schwerionenforschung Darmstadt (GSI) in
cooperation with the Forschungszentrum Rossendorf jointly propose to build a hospital-based
ion beam facility for tumor therapy in Heidelberg. This facility will close a medical
care gap in Germany for established indications and will also allow the evaluation of
new indications in large-scale clinical studies. It can be constructed in five years by
the participating institutions in cooperation with industry. The required funds for capital
expenditures in the amount of DM 110 million can be refinanced through the subsequent
patient revenues. To operate the facility at a break-even level, average treatment costs
are set at DM 40,000 per patient.
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Gantry system for particle beams that allows full rotation of
the beam about the patient. The gantry has a radius of nearly 6 meters and a total
weight of 160 metric tons.
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