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DNA-damage tolerance (DDT) in yeast is composed of two parallel pathways and mediated by sequential ubiquitinations of PCNA. While monoubiquitination of PCNA promotes translesion synthesis (TLS) that is dependent on polymerase ζ consisted of a catalytic subunit Rev3 and a regulatory subunit Rev7, polyubiquitination of PCNA by Mms2-Ubc13-Rad5 promotes error-free lesion bypass. Inactivation of these two pathways results in a synergistic effect on DNA-damage responses; however, this two-branch DDT model has not been reported in any multicellular organisms. In order to examine whether Arabidopsis thaliana possesses a two-branch DDT system, we created rad5a rev3 double mutant plant lines and compared them with the corresponding single mutants. Arabidopsis rad5a and rev3 mutations are indeed synergistic with respect to root growth inhibition induced by replication-blocking lesions, suggesting that AtRAD5a and AtREV3 are required for error-free and TLS branches of DDT, respectively. Unexpectedly this study reveals three modes of genetic interactions in response to different types of DNA damage, implying that plant RAD5 and REV3 are also involved in DNA damage responses independent of DDT. By comparing with yeast cells, it is apparent that plant TLS is a more frequently utilized means of lesion bypass than error-free DDT in plants.

Saccharomyces cerevisiae is an ideal model for lower eukaryotic microorganisms in the study of a variety of biochemical, genetic, and cellular processes. The quantitative or semiquantitative assessment of cell growth and survival under given conditions is a critical technique in the above studies. This chapter describes three complementary protocols to measure relative survival of yeast cells under specific experimental conditions. Similar methods can also be applied to other microorganisms and adapted to study cell growth in addition to survival.

Saccharomyces cerevisiae is an ideal model for lower eukaryotic microorganisms in the study of a variety of biochemical, genetic, and cellular processes. The quantitative or semiquantitative assessment of cell growth and survival under given conditions is a critical technique in the above studies. This chapter describes three complementary protocols to measure relative survival of yeast cells under specific experimental conditions. Similar methods can also be applied to other microorganisms and adapted to study cell growth in addition to survival.

The ESPRIT IV (European strategic programme for research and development in information technology)project ElectroNet aimed at defining a European data model suitable for planning applications of HV (high voltage) and EHV (extra high voltage) power systems by applying the ISO-STEP-methodology. For three years thirteen partners from seven European countries worked on this project which was finally completed by the end of September 1999. This paper presents the innovative concepts developed for ElectroNet. Finally an outlook of a subsequent planned project EPSIM is given.

Charged pions are measured with the 4π detector FOPI at GSI using the Au on Au reaction at 1.06 AGeV bombarding energy. The pion multiplicities ngp increase with the number of participants Apart. The average pion multiplicities per participant are #### and #### These values are only half as large as extrapolated from the low-mass systems studied by Harris et al. The ratio #### increases with Apart and decreases with the pion kinetic energies. The pion kinetic energy spectra have concave shapes, their parametrization in terms of thermal Boltzmann distributions yields a low (T l,π) and high (Th,π) temperature which change with the cm emission angle Θ of the pions. In the angular range 45dg is larger than , the high temperatures , are, within experimental uncertainties, the same. The inclusive polar angular distributions of pions are anisotropic, dσ/dΩ increases for forward and backward angles. The forward — backward enhancements are independent of the pion kinetic energies or the number of participants. In addition to the preferred forward — backward emission, also the enhanced emission into the transverse direction Θ = 90° is observed for pions with high energies or for pions from near-central collisions. These observations and the shape of the rapidity spectra suggest that pions, emitted from the central rapidity region, are partly rescattered by spectator matter. The strength of the rescattering process depends only weakly on the number of participants. The experimental data are compared to the results of IQMD/GEANT calculations using momentum dependent NN interactions and a hard equation of state. The calculated pion multiplicities are approximately 50% larger than experimentally determined; the existence of secondary pion sources is reproduced by the calculation, but their predicted strengths are larger than experimentally observed.

Collisions of Au on Au at incident energies of 150, 250 and 400 A MeV were studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (Z < 16) and velocity of the products were detected with full azimuthal acceptance at laboratory angles of 1-30 degrees. Isotope separated light charged particles were measured with movable multiple telescopes in an angular range of 6-90 degrees. Central collisions representing about 1 % of the reaction cross section were selected by requiring high total transverse energy, but vanishing sideflow. The velocity space distributions and yields of the emitted fragments are reported. The data are analysed in terms of a thermal model including radial flow. A comparison with predictions of the Quantum Molecular Model is presented., LateX text 62 pages, plus six Postscript files with a total of 34 figures, accepted by Nucl.Phys.A

DNA post-replication repair (PRR) functions to bypass replication-blocking lesions and is subdivided into two parallel pathways: error-prone translesion DNA synthesis and error-free PRR. While both pathways are dependent on the ubiquitination of PCNA, error-free PRR utilizes noncanonical K63-linked polyubiquitinated PCNA to signal lesion bypass through template switch, a process thought to be dependent on Mms2-Ubc13 and a RING finger motif of the Rad5 ubiquitin ligase. Previous in vitro studies demonstrated the ability of Rad5 to promote replication fork regression, a function dependent on its helicase activity. To investigate the genetic and mechanistic relationship between fork regression in vitro and template switch in vivo, we created and characterized site-specific mutations defective in the Rad5 RING or helicase activity. Our results indicate that both the Rad5 ubiquitin ligase and the helicase activities are exclusively involved in the same error-free PRR pathway. Surprisingly, the Rad5 helicase mutation abolishes its physical interaction with Ubc13 and the K63-linked PCNA polyubiquitin chain assembly. Indeed, physical fusions of Rad5 with Ubc13 bypass the requirement for either the helicase or the RING finger domain. Since the helicase domain overlaps with the SWI/SNF chromatin-remodelling domain, our findings suggest a structural role of this domain and that the Rad5 helicase activity is dispensable for error-free lesion bypass.

We report on Coulomb dissociation experiments utilizing a 208 Pb-beam (641 MeV/nucleon) impinging on C, Sn, Ho, Pb and U targets. Excitation energy distributions for 208 Pb are extracted from an exclusive measurement of the projectile decay products. The measured cross section is dominated for heavy targets by Coulomb excitation of giant resonance states in lead. A thorough analysis yields evidence for the excitation of the double-phonon giant dipole resonance. In contrast to earlier results obtained for other nuclei the extracted cross section for 208 Pb exceeds that of theoretical predictions on the basis of a harmonic oscillator scenario only slightly by about a factor 1.3.

We investigate the beam energy dependence of neutron and proton squeeze-out in collisions of197Au+197Au atE/A=400—800 MeV. The azimuthal anisotropy that describes the enhanced emission of mid-rapidity neutrons perpendicular to the reaction plane rises strongly with the transverse momentum of the neutrons. This dependence of the azimuthal anisotropy follows a universal curve — independent of beam energy — if the neutron momenta are measured in fractions of the projectile momentum per mass unit. Analogously, the kinetic energy spectra of mid-rapidity neutrons exhibit a universal behaviour as a function of the kinetic energy of the projectile.

We present data on collective flow of neutrons in collisons of [sup 197]Au + [sup 197]Au at 400 MeV/nucleon. The azimuthal distribution about the beam axis is investigated with respect to the reaction plane as determined from light charged particles. The squeezeout'' of neutrons, perpendicular to the reaction plane, is observed for the first time. Quantitative agreement to a high level of accuracy is found between the behavior of neutrons and hydrogen ions.

The nuclear response of a medium-mass nucleus ([sup 136]Xe) to electromagnetic excitation in a near-relativistic heavy-ion collision was investigated in the reaction[sup 136]Xe(0.7[ital A] GeV)+Pb. From an exclusive measurement of the neutron decay of the excited [sup 136]Xe projectiles, strong excitations of giant resonances and, in particular, of the double isovector giant dipole resonance were identified. A resonance energy of 28.3[plus minus]0.7 MeV, a width of 6.3[plus minus]1.6 MeV, and a total cross section of 215[plus minus]50 mb were found for the double giant dipole resonance.

We present design studies, results of test measurements, and Monte Carlo simulations which served as a basis for the realization of a large area neutron detector (LAND). It has a front area of 2m×2m and a depth of 1 m, and features a multilayer structure of passive converter and active scintillator material. The detector is subdivided in independently operating paddles which allow time-of-flight and position measurement. An energy resolution of ΔT n / T n =5.3% for a flight path of 15 m and an overall detection efficiency of ϵ ≈ 1 is anticipated for neutrons with T n ≈ 1 GeV. The operation of LAND at the SIS facility of GSI is described.

The exact analysis of the elemental composition at and around a soldering joint of an antique piece of jewelry can elucidate the joining technologies and give hints of the genuineness of the object. As analytical method we use PIXE, which is nondestructive, multielemental and with fundamental parameter calculations gives absolute concentration values. To obtain the necessary spot size of the H2+ beam at the Bonn cyclotron we use a piezo-controlled diaphragm, whose demagnified image is focussed on the target by two magnetic quadrupole triplets. With an electrostatic deflector the beam spot of 0.1 × 0.3 mm2 size can be moved 2 mm in each direction on the target. With a laser beam, which simulates the ion beam, an irregularly shaped archeological object can be positioned. The laser is also used to obtain the alignment of the target surface to the ion beam direction and the small beam size makes it easier to find a flat part on the surface of the object; both of these are important preconditions for using the fundamental parameter method. A scan over a joint of modern gold alloys demonstrates the ability to detect soldering joints. The analysis of four pieces of Roman gold jewelry found in the area of Cologne and Bonn shows examples of brazing with a solder as well as diffusion soldering.

Charged pions from Ni + Ni reactions at 1.05, 1.45 and 1.93 AGeV are measured with the FOPI detector. The mean $\pi^{\pm}$ multiplicities per mean number of participants increase with beam energy, in accordance with earlier studies of the Ar + KCl and La + La systems. The pion kinetic energy spectra have concave shape and are fitted by the superposition of two Boltzmann distributions with different temperatures. These apparent temperatures depend only weakly on bombarding energy. The pion angular distributions show a forward/backward enhancement at all energies, but not the $\Theta = 90^0$ enhancement which was observed in case of the Au + Au system. These features also determine the rapidity distributions which are therefore in disagreement with the hypothesis of one thermal source. The importance of the Coulomb interaction and of the pion rescattering by spectator matter in producing these phenomena is discussed., Comment: 22 pages, Latex using documentstyle[12pt,a4,epsfig], to appear in Z. Phys.A

DNA-damage tolerance (DDT) is defined as a mechanism by which eukaryotic cells resume DNA synthesis to fill the single-stranded DNA gaps left by replication-blocking lesions. Eukaryotic cells employ two different means of DDT, namely translesion DNA synthesis (TLS) and template switching, both of which are coordinately regulated through sequential ubiquitination of PCNA at the K164 residue. In the budding yeast Saccharomyces cerevisiae, the same PCNA-K164 residue can also be sumoylated, which recruits the Srs2 helicase to prevent undesired homologous recombination (HR). While the mediation of TLS by PCNA monoubiquitination has been extensively characterized, the method by which K63-linked PCNA polyubiquitination leads to template switching remains unclear. We recently identified a yeast heterotetrameric Shu complex that couples error-free DDT to HR as a critical step of template switching. Here we report that the Csm2 subunit of Shu physically interacts with Rad55, an accessory protein involved in HR. Rad55 and Rad57 are Rad51 paralogues and form a heterodimer to promote Rad51-ssDNA filament formation by antagonizing Srs2 activity. Although Rad55-Rad57 and Shu function in the same pathway and both act to inhibit Srs2 activity, Shu appears to be dedicated to error-free DDT while the Rad55-Rad57 complex is also involved in double-strand break repair. This study reveals the detailed steps of error-free lesion bypass and also brings to light an intrinsic interplay between error-free DDT and Srs2-mediated inhibition of HR.

Neutron and He-6 momentum distributions from He-8 break-up reactions in a C target have been measured at 240 MeV/u. The two-neutron removal cross section was found to be sigma(-2n) = 0.27 +/- 0.03 b. The nature of the momentum distributions is interpreted in some simple reaction scenarios.

7 pages, 3 figures, 1 table., Transverse and longitudinal momentum distributions of 9Li fragments from 11Li break-up reactions in C, Al and Pb targets have been measured at 280 MeV/u. The two-neutron removal cross-section was measured to be σ(−2n) = 0.26 ± 0.02 b for the carbon target, σ(−2n) = 0.47 ± 0.08 b for the aluminum target and σ(−2n) = 1.9 ± 0.4 b for the lead target. No significant difference is observed between the narrow widths (FWHM ≈ 47 MeV/c) of the transverse and longitudinal momentum distributions of the 9Li fragments. The physical implications of this are discussed., This work was supported by the German Federal Minister for Research and Technology (BMFT) under Contracts 06 DA 641 I, 06 BO 103 and 06 MZ 106 and by GSI via Hochschulzusammenarbeitsvereinbarungen under Contracts DA RICK, BO FRE, F ELE, Mz KRD and partly supported by the Polish Committee of Scientific Research under Contract PB 1158/P3/92/02 and CICYT under contract AEN92-078%CO2-02 (MJGB).

Neutron angular distributions from violent break-up reactions of Li-11 and Be-11 have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles.

Collective flow of nuclear matter is one important aspect of the research performed at heavy ion accelerator laboratories. The phenomenon was predicted on the basis of hydrodynamical calculations [1], and experimental evidence was first presented for the systems 93 Nb + 93 Nb and 197 Au + 197 Au in the projectile energy range between 150 and 1050 MeV/u [2]. The comparison to microscopic calculations shows that nuclear matter is compressed to about two to three times the ground state density and that a substantial fraction of the kinetic energy in the entrance channel is converted into compressional energy [3]. In these calculations, the relation between density and compressional energy depends on the parameterization of the nucleon-nucleon inter-action. The values of its parameters will hopefully be restricted by a comparison of the calculations to experimental data, and thus one can obtain information on the nucleon-nucleon interaction within the nuclear medium which is not accessible from other sources.

Interaction between the electrical transmission system and the turbine generator may induce torsional stresses to the shaft system whose magnitude and risk of damage have to be carefully analyzed in advance to ensure undisturbed operation and to preclude any damage from the unit. Within this task, the present paper investigates the torsional stressing which arise as a result of torsional resonance induced by pulsating components in the electrical torque of the generator and presents a method for assessing the susceptibility of natural torsional modes to excitation.

Turbogenerators with superconducting field winding are being developed in many countries. The incentives for this development work, basic design features and problems of superconducting generators are briefly described. Most of the dificulties involved in the development process are caused by the vast number of specific problems, new design details and manufacturing procedures arising in the course of development. The performance of superconducting generators are briefly described. Most of the difficulties involved in the the present status of the development programmes in the various countries are outlined with particular emphasis of the German programme conducted by KWU and Siemens.

At the Technical University of Munich, a superconducting 320kVA generator has been taken into operation for experimental purposes. KWU and Siemens are running an extensive program to develop superconducting (SC) generators of commercial size. This development program is described in detail, and reports are given about the experimental work on three major components, namely the superconducting field winding, the cryogenic cooling system and the helium transfer equipment

Nuclear power plants are rapidly assuming a major role in supplying the world's increasing demand for electric power. The saturated steam conditions of light-water reactors favor the use of 1500 or 1800 r/min turbines with four-pole generators which are already being built in ratings up to and even exceeding 1500 MVA. Recent developments in gas-cooled reactors give rise to an additional need for 3600 r/min turbines with large two-pole generators.

Recent concern over abnormal stresses imposed on the shafts of large turbine-generators, due to high speed switching of network faults, has led to intensive investigation of this phenomenon. Elaborate computer programs were developed for simulated model studies which revealed that hitherto unexpectedly high shaft stresses can occur merely by tripping a three-phase short circuit near the power station at an unfavorable instant. The effects of circuit breaker reclosing, both successful and unsuccessful, were also investigated together with those due to faulty synchronizing. Test data on a 780 MVA unit gained by telemetric means verified the calculated torques and established the damping coefficients in a running unit. The adverse influence of numerous repetitive instances of such over-stressing on life expenditure of rotor materials is being evaluated.

An integrated stator end-winding support design which differs from conventional support systems is described in this paper. This design is called "Ringbloc system" and features stiff end-winding support by forming a solid, resin-filled end-winding arc with the bar ends bolted to a funnel-shaped backing ring. The backing ring encircles the end winding and is mounted on heavy brackets that allow only movement in the axial direction from thermal expansion. The short-circuit analysis outlined reveals an approximately tenfold reduction of end-winding deflections and stresses due to the stiffness of the composite end-winding arc and backing ring structure. The design is described in detail and considerable information from factory and field tests is presented. The paper also provides information on the operating experience with two-pole and four-pole generators up to ratings of 1530 MVA demonstrating the effectiveness of the Ringbloc system.

The significant potential advantages of superconducting generators have stimulated large-scale efforts throughout the world to develop such generators for utility application. A thorough study of the transient performance of superconducting generators requires improved generator modeling in an efficient program for power system dynamics to adequately represent the highly complex interaction of the generator multi-damper system with the network. A novel approach to this task is presented in this paper. It consists of an advanced network-torsion- machine program to analyze electromagnetic and electromechanical transients in which iterative (repeatedly connected) T-network equivalent circuits for the generator d-q model have been integrated [1]. The capability of this program is outlined and demonstrated by a spectrum of various system disturbances imposed on a large superconducting generator. First results are discussed and highlight particular design considerations of superconducting rotors for improved transient performance.

Superconducting generators are being developed throughout the world. The present status of this effort is reviewed and the different ways in the development programs of the leading manufacturers are outlined. The report describes tne comprehensive multi-step program of advanced turbogenerator technology established by KWU/Siemens which includes the manufacture and testing of a superconducting rotor of full commercial size but reduced active length. Rotor design and materials as well as the test facilities are shown. Some major problems of superconducting generators are discussed and the technical and economic benefits in comparison with conventional generators are described.

Novel iterative T-network equivalent circuits are derived for the direct and quadrature axes of a generator with superconducting field winding and stator air-gap winding. They enable the treatment of the complex skin effect phenomena in a multi-shell damper system for any non- periodical time variation as well as of the mutual inductive couplings of the various rotor damper cylinders and the field and statorwindings. Consisting of linear RL networks, similar to the equivalent circuits of conventional generators, they can be included in existing computer programs for power system and machine dynamics. In this way an efficient tool is obtained to analyze the transient performance of a superconducting generator in the power system, including the torsional behavior, flux density distribution in the superconducting field winding and design optimization of the damper system.

Das Fehlen von geeigneten Berechnungsunterlagen und Beuteilungsmasstaben fur komplexe Beanspruchungszustande hat in der chemischen Hochdrucktechnik und speziell bei der Gestaltung von Hochdruckverschlussen gelegentlich zu unwirtschaftlichen Konstruktionen mit nicht vertretbarem Werkstoffaufwand, wenn nicht zum Versagen gefuhrt. Die Erweiterung bestehender Auslegungsrichtlinien um Elemente und Lastafalle der Schalentheorie mit punktformig oder gleichformig uber den Umfang verteilten Belastungsgrosen gibt dabei Anregungen fur ein in der Praxis verwendbares Berechnungsverfahren. Dieses wird an einem Beispiel erlautert.

Water cooling of a stator winding has already been proved to be reliable, and water cooling of a rotor winding has now been developed to such an extent that it can be used for turbo-generators with large unit ratings. After a short description of the construction of the prototype, the paper discusses the design problems encountered and presents the results of measurements and practical experiences obtained during operational testing. The paper finally presents an explanation of the performance characteristics of a water-cooled rotor.

Wir verwandten das Melanom des syrischen Goldhamsters als Laboratoriumsmodell, um eine mogliche Verwendbarkeit von radioaktiven Substanzen zur Melanomlokalisation zu prufen. Bioverteilungsdaten wurden ermittelt, und wo die Tumorhintergrundsverhaltnisse gunstig waren, wurden Szintigramme (scans) gemacht. Die untersuchten Wirkstoffe hinsichtlich ihrer %-Dosis/g-Aufnahme werden in einer Tabelle gezeigt. Die Scans waren von Nutzen bei Melanomen des Auges. Anderweitige Lokalisation von Melanomen hangen von der Organaufnahme im Gebiete des Tumors ab. Daher konnen wir nicht sagen, das alle Wirkstoffe gleich gut zur Lokalisationsdiagnostik geeignet sind; es scheint eher, das verschiedene radioaktive Substanzen fur die zu untersuchenden Bezirke ermittelt werden mussen. Klinische Studien mit Iodine-123, 4, 3 DMQ (4, 3 dimethylaminopropylamino-7-iodoquinoline) haben uns ermoglicht, zwei Aderhautmelanome und ein Hautmelanom zu lokalisieren. Negativstudien wurden in drei Fallen durchgefuhrt; alle hatten auch ein negatives Biopsieergebnis. Zur Lokalisation von Aderhautmelanomen waren spezielle Kollimatoren erforderlich.