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Rezension zu: Gisbert Laube: Der Reichskunstwart. Geschichte einer Kulturbehörde 1919-1933 (Rechtshistorische Reihe 164); Frankfurt am Main: Peter Lang 1997; 239 S., Abb.; ISBN 3-631-31977-0, Journal für Kunstgeschichte, Bd. 4 Nr. 1 (2000): Journal für Kunstgeschichte

In this dissertation we study the phase diagram of strongly interacting matter by approaching the theory of quantum chromodynamics in the functional approach of Dyson-Schwinger equations. With these quantum (field) equations of motions we calculate the non-perturbative quark propagator within the Matsubara formalism. We built up on previous works and extend the so-called truncation scheme, which is necessary to render the infinite tower of Dyson-Schwinger equations finite and study phase transitions of chiral symmetry and the confinement/deconfinement transition. In the first part of this thesis we discuss general aspects of quantum chromodynamics and introduce the Dyson-Schwinger equations in general and present the quark Dyson-Schwinger equation together with its counterpart for the gluon. The Bethe-Salpeter equation is introduced which is necessary to perform two-body bound state calculations. A view on the phase diagram of quantum chromodynamics is given, including the discussion of order parameter for chiral symmetry and confinement. Here we also discuss the dependence of the phase structure on the masses of the quarks. In the following we present the truncation and our results for an unquenched Nf=2+1 calculation and compare it to previous studies. We highlight some complementary details for the quark and gluon propagator and discus the resulting phase diagram, which is in agreement with previous work. Results for an equivalent of the Columbia plot and the critical surface are discussed. A systematically improved truncation, where the charm quark as a dynamical quark flavour is added, will be presented in Ch. 4. An important aspect in this investigation is the proper adjustment of the scales. This is done by matching vacuum properties of the relevant pseudoscalar mesons separately for Nf=2+1 and Nf=2+1+1 via a solution of the Bethe-Salpeter equation. A comparison of the resulting Nf=2+1 and Nf=2+1+1 phase diagram indicates that a dynamical charm quark has no influence on the phase structure. An open question about the phase diagram of quantum chromodynamics is the importance of hadronic degrees of freedom. These are subject to an exploratory study in Ch. 5, where we perform a two flavour calculation and include the nucleon as a degree of freedom in the well-known quark-diquark approximation. Due to the lack of explicit knowledge of in-medium properties of the nucleon, we refer to vacuum results and test their influence by variation. The results show that in this truncation baryons have only very little influence on the phase diagram. This is followed by an approach for a systematic investigation of the quark-gluon vertex Dyson-Schwinger equation at finite temperature. The presented work features an internal model vertex. Calculations taking an unquenched gluon as input are presented, where we compare the quark mass function to results from lattice calculations. We give details about the regularised condensate and study the impact of the different quark flavours and the dependence of the calculation on the chosen internal properties. In the last chapter we perform an investigation of the analytical properties of the quark. The Schwinger function, as the Fourier transform of the Euclidean quark propagator with respect to (imaginary) time, is studied in the vacuum as well as the medium. The spectral function, obtained from correlator data by solving an ill-defined inverse problem, is introduced together with the Rothkopf-Burnier Bayesian reconstruction algorithm, which returns the Bayesian answer to the given inverse problem. The status of the reconstruction for test data is presented and an outline given. In der vorliegenden Dissertation wird das Phasendiagramm von stark wechselwirkender Materie untersucht. Dazu wird im Rahmen der Quantenchromodynamik der Quarkpropagator über seine quantenfeldtheoretischen Bewegungsgleichungen bestimmt. Diese sind bekannt als Dyson-Schwinger Gleichungen und konstituieren einen funktionalen Zugang, welcher mithilfe des Matsubara-Formalismus bei endlicher Temperatur und endlichem chemischen Potential angewendet wird. Theoretische Hintergründe der Quantenchromodynamik werden erläutert, wobei insbesondere auf die Dyson-Schwinger Gleichungen eingegangen wird. Chirale Symmetrie sowie Confinement und zugehörige Ordnungsparameter werden diskutiert, welche eine Unterteilung des Phasendiagrammes in verschiedene Phasen ermöglichen. Zudem wird der sogenannte Columbia Plot erläutert, der die Abhängigkeit verschiedener Phasenübergänge von der Quarkmasse skizziert. Zunächst werden Ergebnisse für ein System mit zwei entarteten leichten Quarks und einem Strange-Quark mit vorangegangenen Untersuchungen verglichen. Eine Trunkierung, welche notwendig ist um das System aus unendlich vielen gekoppelten Gleichungen auf eine endliche Anzahl an Gleichungen zu reduzieren, wird eingeführt. Die Ergebnisse für die Propagatoren und das Phasendiagramm stimmen gut mit vorherigen Arbeiten überein. Einige zusätzliche Ergebnisse werden präsentiert, wobei insbesondere auf die Abhängigkeit des Phasendiagrammes von der Quarkmasse eingegangen wird. Im Anschluss wird eine systematische Verbesserung der Trunkierung durch die Einführung eines dynamisch betrachteten Charm-Quarks durchgeführt. In dieser Untersuchung ist es insbesondere wichtig, die Skalen richtig zu justieren. Dazu werden die Eigenschaften von pseudoskalaren Mesonen im Vakuum, separat für Nf=2+1 und Nf=2+1+1, reproduziert. Der Vergleich der sich ergebenden Phasendiagramme zeigt, dass das Charm-Quark keinen Einfluss auf die Phasenstruktur hat. Eine wichtige Frage für das Phasendiagramm von stark wechselwirkender Materie betrifft den Einfluss von hadronischen Freiheitsgraden. In einer explorativen Untersuchung für zwei Quarkarten wird der Einfluss des Nukleons in der Quark-Diquark Näherung studiert. Dazu werden unbekannte Abhängigkeiten von Temperatur und chemischem Potential durch Vakuumeigenschaften ersetzt und eine Variation selbiger untersucht. Die Studie zeigt, dass baryonische Freiheitsgrade nur sehr geringen Einfluss auf Phasenübergänge im betrachteten Phasendiagramm haben. Daraufhin wird die reduzierte Dyson-Schwinger Gleichung für den Quark-Gluon-Vertex bei endlicher Temperatur untersucht. Dieser erste Schritt in einer systematischen Studie zeigt wie sich Quarkart sowie Temperaturabhängigkeit auf den Vertex niederschlagen. Es wird offensichtlich, dass eine Rückkopplung der Gleichung für das Gluon notwendig ist. Im letzten Kapitel untersuchen wir analytische Eigenschaften des Quarkpropagators im Vakuum und bei endlicher Temperatur. Dazu wird die Schwinger Funktion, als Fourier-Transformierte des euklidischen Propagators bezüglich (imaginärer) Zeit untersucht. Zudem wird die Spektralfunktion, welche alle Informationen über die analytische Struktur enthält, eingeführt. Die Bestimmung der Spektralfunktion erfordert die Lösung eines inversen Problems, wozu eine Bayes´sche Rekonstruktion genutzt wird. Ergebnisse für die Spektralfunktion von Testdaten, die mithilfe des Rothkopf-Burnier Algorithmus bestimmt wurden, werden präsentiert und notwendige nächste Schritte diskutiert.

The wooden pavilion “Jeka” (Echo) was built in 1843 according to the plans of the Austrian Empire garden architect Franz Schücht. “Echo” pavilion is the only remaining one of ten similar pavilions that were placed in the Forest-park Maksimir during the 19th century. Since 1964 the “Echo” pavilion has been protected by law and declared as cultural monument of garden architecture together with the whole park Maksimir, in which it is situated. Although the pavilion was restored several times (last time in 1986) it was in very bad condition. The reconstruction and preservation of the complete pavilion’s wooden construction were done after a careful analysis of its recent state in 2000. During reconstruction, state of the art construction and preservation methods were applied and a monitoring system for wood moisture content at three different positions inside the roof construction was installed. Twice a year the pavilion is being carefully visually inspected and data from data logger downloaded and correctness of the equipment verified.

As an easy, fast, and effective sterilisation method, gamma irradiation changes molecular structures not only in pest’ s living cells, but also in wooden cell walls. Radiation-induced depolymerisation causes significant changes in some properties of wood crucial for restoration and for laboratory testing of wood-preservative effectiveness. The influence of gamma radiation concerning total amount of water-soluble carbohydrates (TSC), maximum swelling (α MAX) and resistance to impact milling (RIM) were investigated. Cobalt (60Co) was used as gamma source and Scots pine sapwood (Pinus sylvestris L.) was irradiated with dosages of 30, 90 and 150 kGy. A strong linear correlation between TSC and the radiation dosage was found. Leached irradiated specimens had significantly greater TSC than non-irradiated controls. RIM decreased significantly and linearly with increasing radiation dosage. After leaching, the linearity between these parameters was improved. Gamma radiation had no significant effect on α MAX and the elapsed time after irradiation did not influence α MAX, RIM, and TSC.

Zeitschrift für Ostmitteleuropa-Forschung, Bd. 55 Nr. 4 (2006)

Sterilisation by gamma radiation is very easy, fast and effective, but gamma radiation changes molecular structure not only in pest’ s living cells, but also in wooden cell walls. The preliminary study data of maximum swelling and resistance to impact milling (RIM) dependency on gamma radiation and time period after radiation are presented. 60Co was used as a gamma radiation source and the dosage of 30 kGy was applied at Scots pine (Pinus sylvestris L.). By leaching a high significant mass loss of irradiated specimens was established. 10 days after irradiation the mean value of the mass loss was 1.40 % and after 150 days it was 1.15 % while the mass loss of non-irradiated controls was 0.74 %. The radiation and time after radiation had no significant influence onto maximum swelling neither in radial nor in tangential direction. Leached irradiated wood had significant difference in maximum swelling in comparison to controls. RIM of irradiated wood is significantly minor than of the non-irradiated controls, and decrease became more emphasised and significant after leaching. After radiation with the dosage of 30 kGy, RIM decreased for 2.16 % and for leached specimens the decrease amounts 3.2 %.