Few people outside of mathematics are aware of the varieties of mathemat ical experience - the degree to which different mathematical subjects have different and distinctive flavors, often attractive to some mathematicians and repellant to others. The particular flavor of the subject of minimal surfaces seems to lie in a combination of the concreteness of the objects being studied, their origin and relation to the physical world, and the way they lie at the intersection of so many different parts of mathematics. In the past fifteen years a new component has been added: the availability of computer graphics to provide illustrations that are both mathematically instructive and esthetically pleas ing. During the course of the twentieth century, two major thrusts have played a seminal role in the evolution of minimal surface theory. The first is the work on the Plateau Problem, whose initial phase culminated in the solution for which Jesse Douglas was awarded one of the first two Fields Medals in 1936. (The other Fields Medal that year went to Lars V. Ahlfors for his contributions to complex analysis, including his important new insights in Nevanlinna Theory.) The second was the innovative approach to partial differential equations by Serge Bernstein, which led to the celebrated Bernstein's Theorem, stating that the only solution to the minimal surface equation over the whole plane is the trivial solution: a linear function."

Few people outside of mathematics are aware of the varieties of mathemat ical experience - the degree to which different mathematical subjects have different and distinctive flavors, often attractive to some mathematicians and repellant to others. The particular flavor of the subject of minimal surfaces seems to lie in a combination of the concreteness of the objects being studied, their origin and relation to the physical world, and the way they lie at the intersection of so many different parts of mathematics. In the past fifteen years a new component has been added: the availability of computer graphics to provide illustrations that are both mathematically instructive and esthetically pleas ing. During the course of the twentieth century, two major thrusts have played a seminal role in the evolution of minimal surface theory. The first is the work on the Plateau Problem, whose initial phase culminated in the solution for which Jesse Douglas was awarded one of the first two Fields Medals in 1936. (The other Fields Medal that year went to Lars V. Ahlfors for his contributions to complex analysis, including his important new insights in Nevanlinna Theory.) The second was the innovative approach to partial differential equations by Serge Bernstein, which led to the celebrated Bernstein's Theorem, stating that the only solution to the minimal surface equation over the whole plane is the trivial solution: a linear function."

Der vorliegende Band gibt die Vortrage eines Symposi !Us wieder, das im Rahmen des gemeinsamen Kongresses der Deutschen und Osterreichischen Rontgen- gesellschaft imJahre 1973 in Wien durchgefuhrt wurde. Die Arb itsgemeinschaft fur Strahlenbiologie in der DRG setzte damit gemeinsam mit der Osterreichischen Rontgengesellschaft eine Serie von Veranstaltungen fort, die den Dialog zwischen dem klinisch tatigen Radiologen und dem theoretischen Radiologen, insbeson- dere dem Strahlenbiologen, verstarken sollen. Di beiden thematischen Schwer- punkte des Symposiums, lymphatisches System und kleine Dosen, konnen diesem Vorhaben in besonderem MaBe dienen. Nicht nur aufgrund der aktuellen Situation muB es ein Anliegen der Radiologen sein, die biologische Wirkung kleiner Strahlendosen zu erfassen und verstehen zu lernen. Einerseits kann man einer emotionalen Darstellung, wie sie in der Offentlichkeit hier und da versucht wird, nur mit harten Fakten wissenschaft- licher Erfahrungen und Dberlegungen gegenubertreten, andererseits ist die Ab- schlitzung des Risikos, das durch die Absorption ionisierender Strahlen einge- gangen wird, insbesondere in Hinsicht auf Spliteffekte, wie z. B. die cancerogene Wirkung, keineswegs abgeschlossen. Seit den Arbeiten von Heineke in den Jahren 1903-1905 nimmt die Strahlen- empfindlichkeit von Lymphocyten bei strahlenbiologischen Untersuchungen eine hervorragende Stellung ein, die auch fur die radiologische Klinik Bedeutung erlangt hat. So gehort die Bestimmung der Lymphocytenzahl im Blut auch heute noch zur routinemliBigen Dberwachung strahlentherapeutischer MaBnahmen.