| 1. |
- Amann, F., et al.
(författare)
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A search for murarregamma at the level of 10-13
- 1991
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Ingår i: Proceedings of the 25th International Conference on High Energy Physics. - 9810024347 ; , s. 1070-1071
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Konferensbidrag (refereegranskat)abstract
- The MEGA experiment, which is a search for the decay murarregamma with a branching ratio sensitivity of about 10-13, employs highly modular, fast detectors, state-of-the-art electronics, and a staged trigger with on-line filters. The detectors are contained in a 1.5-T solenoidal field produced by a superconducting magnet. Positrons are confined to the central region and are measured by a set of thin MWPCs. Photons are measured by one of four layers of pair spectrometers in the outer region. Most aspects of the design have been validated in engineering runs; data taking will begin in 1990 with much of the electron arm and one pair spectrometer layer installed.
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| 2. |
- Cederwall, Bo, et al.
(författare)
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NEW FEATURES OF SUPERDEFORMED BANDS IN HG-194
- 1994
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 72:20, s. 3150-3153
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Tidskriftsartikel (refereegranskat)abstract
- Two new features of superdeformed (SD) bands in the A almost-equal-to 190 region emerge from a study of Hg-194 with the Gammasphere detector array. A decrease of the dynamic moment of inertia is observed for rotational frequencies HBARomega greater-than-or-equal-to 0.4 MeV, confirming long standing expectations based on mean field calculations with pairing. Evidence for a small staggering in the SD transition energies is also observed, suggesting the presence of terms with fourfold symmetry in the SD Hamiltonian.
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| 5. |
- HUGHES, JR, et al.
(författare)
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LIFETIME MEASUREMENT IN EXCITED AND YRAST SUPERDEFORMED BANDS IN HG-194
- 1994
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 72:6, s. 824-827
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear level lifetimes have been measured in two superdeformed bands in Hg-194 using the Doppler-shift attenuation method. Average transition quadrupole moments derived from the life-times of an excited and yrast superdeformed bands are Q(t) = 17.6(30) and 17.2(20) eb, respectively. The Doppler shifts of the excited band relative to the yrast band indicate a slight difference in quadrupole moments [+4(5)%], assuming similar side feeding. These results imply that the second well is stable and rigid with respect to the particle excitation responsible for this excited band.
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| 10. |
- Tubulekas, I, et al.
(författare)
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A single amino acid substitution in elongation factor Tu disrupts interaction between the ternary complex and the ribosome
- 1993
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 175:1, s. 240-250
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Tidskriftsartikel (refereegranskat)abstract
- Elongation factor Tu (EF-Tu).GTP has the primary function of promoting the efficient and correct interaction of aminoacyl-tRNA with the ribosome. Very little is known about the elements in EF-Tu involved in this interaction. We describe a mutant form of EF-Tu, isolated in Salmonella typhimurium, that causes a severe defect in the interaction of the ternary complex with the ribosome. The mutation causes the substitution of Val for Gly-280 in domain II of EF-Tu. The in vivo growth and translation phenotypes of strains harboring this mutation are indistinguishable from those of strains in which the same tuf gene is insertionally inactivated. Viable cells are not obtained when the other tuf gene is inactivated, showing that the mutant EF-Tu alone cannot support cell growth. We have confirmed, by partial protein sequencing, that the mutant EF-Tu is present in the cells. In vitro analysis of the natural mixture of wild-type and mutant EF-Tu allows us to identify the major defect of this mutant. Our data shows that the EF-Tu is homogeneous and competent with respect to guanine nucleotide binding and exchange, stimulation of nucleotide exchange by EF-Ts, and ternary complex formation with aminoacyl-tRNA. However various measures of translational efficiency show a significant reduction, which is associated with a defective interaction between the ribosome and the mutant EF-Tu.GTP.aminoacyl-tRNA complex. In addition, the antibiotic kirromycin, which blocks translation by binding EF-Tu on the ribosome, fails to do so with this mutant EF-Tu, although it does form a complex with EF-Tu. Our results suggest that this region of domain II in EF-Tu has an important function and influences the binding of the ternary complex to the codon-programmed ribosome during protein synthesis. Models involving either a direct or an indirect effect of the mutation are discussed.
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