2,304 research outputs found
Measurements of r-process nuclei
Progress in the astrophysical understanding of r-process nucleosynthesis also
depends on the knowledge of nuclear-physics quantities of extremely
neutron-rich isotopes. In this context, experiments at CERN-ISOLDE have played
a pioneering role in exploring new shell-structure far from stability. Possible
implications of new nuclear-data input on the reproduction of r-abundance
observations are presented.Comment: 10 pages, 3 figures; Proc. "Nuclei in the Cosmos 2000", Nucl. Phys.
Stellar and nuclear-physics constraints on two r-process components in the early Galaxy
Proceedings of "Nuclei in the Cosmos 2000", Aarhus, DanmarkComment: 3 pages, 2 figures; to be publ. in Nucl. Phys.
An evaluation of the efficacy of a social skills training program with young multiply handicapped students
This study was designed to analyze the efficacy of a formal social skills training (SST) program on a group of self-contained, multiply handicapped students. The treatment group, consisting of 24 students, underwent five months of formal SST, at least three times a week for a 30 to 50 minute period. The participating teachers were trained in, and followed, Elias and Clabby\u27s Social Decision Making and Problem Solving: Revised Readiness Curriculum (1988). They were asked to complete pre- and post test Likert scales (Social Problem Solving Skills Checklist) on the presence of specific social skills in each student.
Average gains in the areas of self control skills, group and social awareness, and getting along with self and others were calculated, totaled, and analyzed against three comparison groups representing a Regular Education sample (22 students), a Resource Center sample (17 students), and a Self Contained, Multiply Handicapped comparison sample (21 students).
Results indicated that formal SST not only improved the acquisition of specific skills, but enabled the Self-Contained Treatment group to obtain the highest percentage gains in all areas, progressing at a faster rate than any of the comparison groups. This study emphasized the importance of a SST program, and it\u27s efficacy on young, multiply handicapped students
Nuclear Structure Studies at ISOLDE and their Impact on the Astrophysical r-Process
The focus of the present review is the production of the heaviest elements in
nature via the r-process. A correct understanding and modeling requires the
knowledge of nuclear properties far from stability and a detailed prescription
of the astrophysical environment. Experiments at CERN/ISOLDE have played a
pioneering role in exploring the characteristics of nuclear structure in terms
of masses and beta-decay properties. Initial examinations paid attention to far
unstable nuclei with magic neutron numbers related to r-process peaks, while
present activities are centered on the evolution of shell effects with the
distance from the valley of stability. We first show in site-independent
applications the effect of both types of nuclear properties on r-process
abundances. Then, we explore the results of calculations related to two
different `realistic' astrophysical sites, (i) the supernova neutrino wind and
(ii) neutron star mergers. We close with a list of remaining theoretical and
experimental challenges needed to overcome for a full understanding of the
nature of the r-process, and the role CERN/ISOLDE can play in this process.Comment: LATEX, 38 pages, 16 figures, submitted to Hyperfine Interaction
A tentative 4- isomeric state in Sr-98
Annual Report 2001, Institut fuer Kernchemie,
Johannes-Gutenberg-Universitaet, Mainz, GermanyComment: 3 pages, 1 figur
Charged-Particle and Neutron-Capture Processes in the High-Entropy Wind of Core-Collapse Supernovae
The astrophysical site of the r-process is still uncertain, and a full
exploration of the systematics of this process in terms of its dependence on
nuclear properties from stability to the neutron drip-line within realistic
stellar environments has still to be undertaken. Sufficiently high neutron to
seed ratios can only be obtained either in very neutron-rich low-entropy
environments or moderately neutron-rich high-entropy environments, related to
neutron star mergers (or jets of neutron star matter) and the high-entropy wind
of core-collapse supernova explosions. As chemical evolution models seem to
disfavor neutron star mergers, we focus here on high-entropy environments
characterized by entropy , electron abundance and expansion velocity
. We investigate the termination point of charged-particle reactions,
and we define a maximum entropy for a given and ,
beyond which the seed production of heavy elements fails due to the very small
matter density. We then investigate whether an r-process subsequent to the
charged-particle freeze-out can in principle be understood on the basis of the
classical approach, which assumes a chemical equilibrium between neutron
captures and photodisintegrations, possibly followed by a -flow
equilibrium. In particular, we illustrate how long such a chemical equilibrium
approximation holds, how the freeze-out from such conditions affects the
abundance pattern, and which role the late capture of neutrons originating from
-delayed neutron emission can play.Comment: 52 pages, 31 figure
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