367 research outputs found
Half-life and spin of 60Mn^g
A value of 0.28 +/- 0.02 s has been deduced for the half-life of the ground
state of 60Mn, in sharp contrast to the previously adopted value of 51 +/- 6 s.
Access to the low-spin 60Mn ground state was accomplished via beta decay of the
0+ 60Cr parent nuclide. New, low-energy states in 60Mn have been identified
from beta-delayed gamma-ray spectroscopy. The new, shorter half-life of 60Mn^g
is not suggestive of isospin forbidden beta decay, and new spin and parity
assignments of 1+ and 4+ have been adopted for the ground and isomeric
beta-decaying states, respectively, of 60Mn.Comment: 13 pages, 5 figures, Accepted for publication in Phys. Rev.
Shell structure underlying the evolution of quadrupole collectivity in S-38 and S-40 probed by transient-field g-factor measurements on fast radioactive beams
The shell structure underlying shape changes in neutron-rich nuclei between
N=20 and N=28 has been investigated by a novel application of the transient
field technique to measure the first-excited state g factors in S-38 and S-40
produced as fast radioactive beams. Details of the new methodology are
presented. In both S-38 and S-40 there is a fine balance between the proton and
neutron contributions to the magnetic moments. Shell model calculations which
describe the level schemes and quadrupole properties of these nuclei also give
a satisfactory explanation of the g factors. In S-38 the g factor is extremely
sensitive to the occupation of the neutron p3/2 orbit above the N=28 shell gap
as occupation of this orbit strongly affects the proton configuration. The g
factor of deformed S-40 does not resemble that of a conventional collective
nucleus because spin contributions are more important than usual.Comment: 10 pages, 36 figures, accepted for publication in Physical Review
Probing shell structure and shape changes in neutron-rich sulfur isotopes through transient-field g factor measurements on fast radioactive beams of 38S and 40S
The shell structure underlying shape changes in neutron-rich nuclei near N=28
has been investigated by a novel application of the transient field technique
to measure the first-excited state g factors in 38S and 40S produced as fast
radioactive beams. There is a fine balance between proton and neutron
contributions to the magnetic moments in both nuclei. The g factor of deformed
40S does not resemble that of a conventional collective nucleus because spin
contributions are more important than usual.Comment: 10 pages, 6 figures, accepted in PR
Half Life of the Doubly-magic r-Process Nucleus 78Ni
Nuclei with magic numbers serve as important benchmarks in nuclear theory. In
addition, neutron-rich nuclei play an important role in the astrophysical rapid
neutron-capture process (r-process). 78Ni is the only doubly-magic nucleus that
is also an important waiting point in the r-process, and serves as a major
bottleneck in the synthesis of heavier elements. The half-life of 78Ni has been
experimentally deduced for the first time at the Coupled Cyclotron Facility of
the National Superconducting Cyclotron Laboratory at Michigan State University,
and was found to be 110 (+100 -60) ms. In the same experiment, a first
half-life was deduced for 77Ni of 128 (+27 -33) ms, and more precise half-lives
were deduced for 75Ni and 76Ni of 344 (+20 -24) ms and 238 (+15 -18) ms
respectively.Comment: 4 pages, 3 figure
Proton Drip-Line Calculations and the Rp-process
One-proton and two-proton separation energies are calculated for proton-rich
nuclei in the region . The method is based on Skyrme Hartree-Fock
calculations of Coulomb displacement energies of mirror nuclei in combination
with the experimental masses of the neutron-rich nuclei. The implications for
the proton drip line and the astrophysical rp-process are discussed. This is
done within the framework of a detailed analysis of the sensitivity of rp
process calculations in type I X-ray burst models on nuclear masses. We find
that the remaining mass uncertainties, in particular for some nuclei with
, still lead to large uncertainties in calculations of X-ray burst light
curves. Further experimental or theoretical improvements of nuclear mass data
are necessary before observed X-ray burst light curves can be used to obtain
quantitative constraints on ignition conditions and neutron star properties. We
identify a list of nuclei for which improved mass data would be most important.Comment: 20 pages, 9 figures, 2 table
Self-control enhancement in children:Ethical and conceptual aspects
Childhood self-control is currently receiving great scientific and public attention because it could predict much of adult’s life success and well-being. Specialized interventions based on findings in social psychology and neuroscience potentially enhance children’s capacity to exercise self-control. This perspective triggers hopes that self-control enhancement allows us to say good-bye for good to potentially unsafe psychopharmacological agents and electronic brain stimulants. This chapter provides an in-depth ethical analysis of pediatric self-control enhancement and points toward a series of serious conceptual and ethical concerns. First, it gives an overview of current psychological as well as neuroscientific research on self-control, and it presents longitudinal studies that emphasize the importance of childhood self-control for adult life success. Second, it critically discusses the concept of self-control presupposed in these approaches and points to crucial limitations. Going beyond an understanding of self-control as a sophisticated means of goal-achievement, i will argue for a comprehensive understanding that takes the inherent normativity of self-controlled behavior seriously. In that context, self-control enhancement appears as not necessarily desirable and occasionally even detrimental. Finally, this chapter questions the notion of childhood implicit in current research and how values typically put on this phase of life could get affected by self-control enhancement. I finish with an exploration of the conditions under which pediatric self-control enhancement is either impermissible, permissible, or maybe obligatory
A dual-fMRI investigation of the iterated Ultimatum Game reveals that reciprocal behaviour is associated with neural alignment
Dyadic interactions often involve a dynamic process of mutual reciprocity; to steer a series of exchanges towards a desired outcome, both interactants must adapt their own behaviour according to that of their interaction partner. Understanding the brain processes behind such bidirectional reciprocity is therefore central to social neuroscience, but this requires measurement of both individuals’ brains during realworld exchanges. We achieved this by performing functional magnetic resonance imaging (fMRI) on pairs of male individuals simultaneously while they interacted in a modifed iterated Ultimatum Game (iUG). In this modifcation, both players could express their intent and maximise their own monetary gain by reciprocating their partner’s behaviour – they could promote generosity through cooperation and/or discourage unfair play with retaliation. By developing a novel model of reciprocity adapted from behavioural economics, we then show that each player’s choices can be predicted accurately by estimating expected utility (EU) not only in terms of immediate payof, but also as a reaction to their opponent’s prior behaviour. Finally, for the frst time we reveal that brain signals implicated in social decision making are modulated by these estimates of EU, and become correlated more strongly between interacting players who reciprocate one another
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