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27 results on '"Voelkel, K A"'

8. Enhanced Out-of-plane Emission of K+ Mesons observed in Au+Au Collisions at 1 AGeV

Author

Shin, Y., Ahner, W., Barth, R., Beckerle, P., Brill, D., Cieslak, M., Debowski, M., Grosse, E., Koczon, P., Kohlmeyer, B., Mang, M., Miskowiec, D., Muentz, C., Oeschler, H., Puehlhofer, F., Schwab, E., Schicker, R., Senger, P., Speer, J., Stroebele, H., Sturm, C., Voelkel, K., Wagner, A., Walus, W., and Collaboration, The KaoS

Subjects
Nuclear Experiment
Abstract

The azimuthal angular distribution of K+ mesons has been measured in Au + Au collisions at 1 AGeV. In peripheral and semi-central collisions, K+ mesons preferentially are emitted perpendicular to the reaction plane. The strength of the azimuthal anisotropy of K+ emission is comparable to the one of pions. No in-plane flow was found for K+ mesons near projectile and target rapidity., Comment: Accepted for publication in Phys. Rev.Lett

Published
1998
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9. Evidence for Different Freeze-Out Radii of High- and Low-Energy Pions Emitted in Au+Au Collisions at 1 GeV/nucleon

Author

Wagner, A., Müntz, C., Oeschler, H., Sturm, C., Barth, R., Cieślak, M., Dȩbowski, M., Grosse, E., Koczo{ń}, P., Mang, M., Miśkowiec, D., Schicker, R., Schwab, E., Senger, P., Beckerle, P., Brill, D., Shin, Y., Ströbele, H., Waluś, W., Kohlmeyer, B., Pühlhofer, F., Speer, J., and Völkel, K.

Subjects
Nuclear Experiment
Abstract

Double differential production cross sections of negative and positive pions and the number of participating protons have been measured in central Au+Au collisions at 1 GeV per nucleon incident energy. At low pion energies the pi^- yield is strongly enhanced over the pi^+ yield. The energy dependence of the pi^-/pi^+ ratio is assigned to the Coulomb interaction of the charged pions with the protons in the reaction zone. The deduced Coulomb potential increases with increasing pion c.m. energy. This behavior indicates different freeze-out radii for different pion energies in the c.m.~frame., Comment: IKDA is the Institute for Nuclear Physics in Darmstadt/Germany

Published
1997
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10. Pankreas

Author

Mann, S., Völkel, K., Spies, V., Erdel, I., Zirngibl, H., Weimann, A., Dralle, H., Balks, H. J., Gratz, K. F., Fock, V., Löffge, O., Pichlmayr, R., Schwab, M., Schwall, G., Schmid, M., Pilch, H., Trede, M., Böttger, T., Boddin, J., Küchle, R., Junginger, T., Gansauge, F., Link, K. H., Rehwagen, C., Beger, H. G., Hartel, W., editor, and Hierholzer, G.

Published
1995
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11. Meson Production in Heavy-Ion Collisions at 1 GEV/Nucleon

Author

KaoS Collaboration, Oeschler, H., Ahner, W., Barth, R., Cieślak, M., Debowski, M., Grosse, E., Henning, W., Koczoń, P., Mang, M., Miśkowiec, D., Schicker, R., Schwab, E., Senger, P., Baltes, P., Müntz, C., Sartorius, A., Sturm, C., Wagner, A., Beckerle, P., Bormann, C., Brill, D., Shin, Y., Stein, J., Stiebing, K., Stock, R., Ströbele, H., Kohlmeyer, B., Pöppl, H., Pühlhofer, F., Schlei, B., Speer, J., Völkel, K., Waluś, W., Greiner, Walter, editor, Stöcker, Horst, editor, and Gallmann, André, editor

Published
1994
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17. DNA topoisomerase II mutant of Saccharomyces cerevisiae: topoisomerase II is required for segregation of daughter molecules at the termination of DNA replication.

Author

DiNardo, S, Voelkel, K, and Sternglanz, R

Abstract

A temperature-sensitive DNA topoisomerase II mutant of the yeast Saccharomyces cerevisiae has been identified. Genetic analysis shows that a single recessive nuclear mutation is responsible for both temperature-sensitive growth and enzymatic activity. Thus, topoisomerase II is essential for viability and the mutation is most probably in the structural gene. Experiments with synchronized mutant cells show that at the nonpermissive temperature cells can undergo one, and only one, round of DNA replication. These cells are arrested at medial nuclear division. Analysis of 2-microns plasmid DNA from these cells shows it to be in the form of multiply intertwined catenated dimers. The results suggest that DNA topoisomerase II is necessary for the segregation of chromosomes at the termination of DNA replication.

Published
1984
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18. Mutations in the gene coding for Escherichia coli DNA topoisomerase I affect transcription and transposition.

Author

Sternglanz, R, DiNardo, S, Voelkel, K A, Nishimura, Y, Hirota, Y, Becherer, K, Zumstein, L, and Wang, J C

Abstract

Mutations in top, the structural gene for Escherichia coli DNA topoisomerase I, have been identified and mapped at 28 min on the chromosome, near cysB. Strains carrying deletions of the top gene are viable. The top mutations, however, do exert pleiotropic effects on transcription and transposition. Mutants lacking DNA topoisomerase I have a more rapid rate of induction and a higher level of catabolite-sensitive enzymes including tryptophanase and beta-galactosidase. This general activation of transcription by top mutations can be attributed to an increase in the negative superhelicity of the DNA in vivo when the topoisomerase activity is abolished. The frequency of transposition of Tn5, a transposon carrying kanamycin resistance, is decreased by a factor of 40 or more in top mutants. A direct or indirect role of the topoisomerase in transposition is discussed. The transposition frequency of Tn3, however, is not dependent on top. Based on the studies of the E. coli top mutants, it appears that the supX gene, which was originally studied in Salmonella typhimurium [Dubnau, E. & Margolin, P. (1972) Mol. Gen. Genet. 117, 91-112] is likely to be the structural gene for DNA topoisomerase I.

Published
1981
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22. Kaon production in heavy ion collisions and the nuclear equation of state

Author

Senger, Peter, Ahner, W., Baltes, P., Barth, R., Beckerle, P., Bormann, Ch., Brill, D., Cieślak, M., Grosse, E., Henning, W., Koczoń, P., Kohlmeyer, B., Miśkowiec, D., Müntz, Ch., Oeschler, H., Pöppl, H., Pühlhofer, F., Sartorius, S., Schicker, R., Schwab, E., Senger, P., Shin, Y., Speer, J., Stein, J., Stock, R., Ströbele, H., Sturm, Ch., Völkel, K., Wagner, A., and Waluś, W.

Published
1993
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25. The kaon spectrometer at SIS

Author

Senger, P., Ahner, W., Baltes, P., Beckerle, P., Bormann, Ch., Brill, D., Cieślak, M., Grosse, E., Henning, W., Koczoń, P., Kohlmeyer, B., Konrad, W., Miśkowiec, D., Müntz, Ch., Oeschler, H., Pöppl, H., Prokopowicz, W., Pühlhofer, F., Sartorius, S., Schicker, R., Schlei, B., Schwab, E., Shin, Y., Speer, J., Stein, J., Stiebing, K., Stock, R., Ströbele, H., Sturm, Ch., Völkel, K., Wagner, A., and Waluś, W.

Published
1993
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27. Escherichia coli DNA topoisomerase I mutants have compensatory mutations in DNA gyrase genes.

Author

DiNardo S, Voelkel KA, Sternglanz R, Reynolds AE, and Wright A

Subjects
Chromosome Deletion, Escherichia coli genetics, Gene Expression Regulation, Genotype, Operon, Species Specificity, Transduction, Genetic, DNA Topoisomerases, Type I genetics, DNA Topoisomerases, Type II genetics, Escherichia coli enzymology, Genes, Bacterial, Genes, Viral, Mutation
Abstract

Escherichia coli deletion mutants lacking DNA topoisomerase I have been identified previously and shown to grow at a normal rate. We show that such strains grow normally only because of spontaneously arising mutations that compensate for the topoisomerase I defect. Several of these compensatory mutations have been found to map at or near the genes encoding DNA gyrase, gyrA and gyrB. DNA gyrase assays of crude extracts show that strains carrying the mutations have lower gyrase activity. Thus the mutations are in the gyrase structural genes or in nearby regulatory sequences. These results, in conjunction with DNA supercoiling measurements of others, indicate that in vivo DNA superhelicity is a result of a balance between topoisomerase I and gyrase activities. An excess of negative supercoils due to an absence of topoisomerase I is deleterious to the cell, but a moderate gyrase deficiency is not harmful.

Published
1982
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