A model assuming coherent quadrupole-octupole vibrations and rotations is applied to describe non-yrast energy sequences with alternating parity in several eveneven nuclei from different regions, namely 152,154 Sm, 154,156,158 Gd, 236 U and 100 Mo. Within the model scheme the yrast alternating-parity band is composed by the members of the ground-state band and the lowest negative-parity levels with odd angular momenta. The non-yrast alternating-parity sequences unite levels of β-bands with higher negative-parity levels. The model description reproduces the structure of the considered alternating-parity spectra together with the observed B(E1), B(E2) and B(E3) transition probabilities within and between the different level-sequences. B(E1) and B(E3) reduced probabilities for transitions connecting states with opposite parity in the non-yrast alternating-parity bands are predicted. The implemented study outlines the limits of the considered band-coupling scheme and provides estimations about the collective energy potential which governs the quadrupole-octupole properties of the considered nuclei.

Fission of ' Au, ' Th+838-MeV ' S projectiles was studied by measuring fragment coincident neutrons. Neutron energy spectra were decomposed into preequilibrium, prescission, and postscission contributions with a constrained moving source analysis. Excitation energies deduced from the transferred linear momentum are consistent with calculations applying the Boltzmann master equation, and with an energy balance based upon the experimental neutron multiplicities and charged particles from evaporation calculations. The time scale of fission derived from the prescission neutron multiplicities extends from 5 X 10 " to 3 X 10 s; it does not depend on the initial excitation energy, is about a factor of 2 longer for symmetric than for asymmetric fragmentations, and increases with the fissility of the primary reaction system. For all mass splits, the excitation energy left at scission is 50 -60 MeV.

The model of coherent quadrupole and octupole motion (CQOM) is applied to describe nonyrast split parity-doublet spectra in odd-mass nuclei. The yrast levels are described as low-energy rotation-vibration modes coupled to the ground single-particle (s.p.) state, while the non-yrast parity-doublet structures are obtained as higher-energy rotation-vibration modes coupled to excited s.p. states. It is shown that the extended model scheme describes both the yrast and non-yrast quasi parity-doublet spectra and the related B(E1) and B(E2) transition rates in different regions of heavy odd-A nuclei. The involvement of the reflection-asymmetric deformed shell model to describe the single-particle motion and the Coriolis interaction on a deeper level is discussed.

The genes encoding the Calvin cycle enzymes of Nitrobacter vulgaris T3 are found as two separate clusters on the chromosome. One cluster contains the genes for the large and small subunits of ribulose-l,5-bisphosphate carboxylase/oxygenase (RuBisCO), glyceraldehyde-3-phosphate dehydrogenase, and one encoding a regulatory protein of the LysR family. The other cluster contains the genes for fructose-l,6-/sedoheptulose-l,7-bisphosphatase, phosphoribulokinase, and fructose-l,6-/ sedoheptulose-l,7-bisphosphate aldolase. With the exception of the LysR-like gene, the genes in each cluster are apparently transcribed in the same direction. The deduced amino acid sequence of both the large and small subunits of RuBisCO are most similar (84-86%) to those of Thiobacillus ferrooxidans and Chromatium vinosum. The deduced sequences of phosphoribulokinase and fructose/sedoheptulose bisphosphatase are 67-73% and 44-46% similar to those reported for other autotrophic bacteria, respectively.[2]. Form I, the enzyme found in most autotrophic organisms, is a hexadecamer of eight large (CbbL) and eight small (CbbS) subunits. Form II (CbbM), found in some proteobacteria, is composed of only 2-6 large subunits [2,3]. The RuBisCO of Nitrobacter hamburgensis, and presumably that of other Nitrobacter species, is of the form I type [4]. In the prokaryotes examined thus far, the form I RuBisCO genes (cbbL, cbbS) are found next to each other and are co-transcribed [2,[5][6][7][8][9]. In Rhodobacter sphaeroides, Alcaligenes eutrophus, Xanthobacter flavus, and probably in Rhodobacter capsulatus and Rhodopseudomonas palustris, a number of other Calvin cycle genes are clustered with cbbL / cbbS and/or

Prescission (v;") and postscission (est) neutron multiplicities have been measured for the reactions p+"' ' ' "U at several projectile energies between 12.7 and 25.6 MeV in coincidence with binary fragments. Separation of v;" from v~t was achieved under the assumption of isotropic emission in the respective source frames. Both multiplicities increase with initial excitation energy Ec" with comparable rates EECN/hv=17+3 MeV. v;"(E~N) extends existing data of heavy-ion induced fusion-fission with ECN 50 MeV; for EcN~2 0 MeV it is incompatible with the transitionstate model and cannot be reproduced without a delay time for the fission competition in the order of 3X10 -10 ' s. The fragment mass dependence v~"(m) shows a clear sawtooth structure for all three targets at E~= 12.6 MeV that is gradually washed out with increasing E~o r decreasing total kinetic energy TKE, because the heavier fragment receives most of the additional excitation energy. The nuclear temperatures of the heavy fragments exceed those of the light ones, but seem to approach each other with increasing fragment excitation. sa et al. " predicts the structure to persist with growing ECN (but shifted upward in absolute number}, whereas the statistical scission point model' does not. At present, there are three classes of theoretical approaches to the fission process in discussion. The statistical model of Wilkins et al. ' assumes a quasistability at the scission point. It can be applied to all kinds of nuclear fission, in particular those with high mass asymmetry and those which are strongly influenced by shell effects, but it has its problems' with the widths of the fragment mass distributions. The liquid drop model is essentially restricted to symmetric fission' and therefore not very appropriate for the reaction systems under discussion. Recently, Brosa et al. ' introduced a model based on a random neck rupture that naturally leads to the experimentally observed widths of mass distributions and predicts the sawtooth v"", (m) as a consequence of 41

In this work we examine the possibility to describe yrast positive-and negativeparity excitations of deformed even-even nuclei through a collective rotation model in which the nuclear surface is characterized by triaxial quadrupole and octupole deformations. The nuclear moments of inertia are expressed as sums of quadrupole and octupole parts. By assuming an adiabatic separation of rotation and vibration degrees of freedom we suppose that the structure of the positive-and negative-parity bands may be determined by the triaxial-rigid-rotor motion of the nucleus. By diagonalizing the Hamiltonian in a symmetrized rotor basis with embedded parity we obtain a model description for the yrast positive-and negative-parity bands in several actinide nuclei. We show that the energy displacement between the opposite-parity sequences can be explained as the result of the quadrupole-octupole triaxiality.

The Coriolis decoupling strength in nuclear single-particle (s.p.) states with mixed parity is examined within a reflection-asymmetric deformed shell model. A strong coupling scheme between the parity mixed s.p. state and a coherent quadrupole–octupole vibration mode in the core is considered for odd-mass nuclei. The Coriolis decoupling factor is obtained in a projected form corresponding to good total parity of the system. The average parity of the s.p. state and the decoupling factor are evaluated in several nuclei as functions of the quadrupole and octupole deformation parameters β2 and β3. It is found that the average s.p. parity obtains various dominant values in the (β2, β3)-plane. It is shown that by comparing the behaviour of the decoupling factor in the (β2, β3)-plane to values obtained in a collective quadrupole–octupole model and by requiring consistency between the calculated dominant parity and the experimentally established parity in the ground state one can determine physically reasonable deformation regions for the considered odd-A nuclei.

Effects of the parity-mixed single-particle (s.p.) state on the collective properties of odd nuclei with reflection-asymmetric degrees of freedom are studied. The Coriolis strength and the average s.p. parity in the nuclei 219 Ra , 225 Ra , 225 Th and 241 Cm are examined in dependence on axial quadrupole and octupole deformation parameters β2 and β3 within a reflection-asymmetric deformed shell model. The obtained behaviour of the Coriolis decoupling factor in the (β2, β3)-plane is compared with values fitted in a collective quadrupole-octupole model, which allows one to determine physically reasonable deformation regions for the considered nuclei. The study provides a relation between deformation parameters, Coriolis interaction strength and the structure of collective spectra in odd-mass nuclei with quadrupole-octupole deformations.