614 research outputs found
Three-body decay of Be
Three-body correlations for the ground-state decay of the lightest two-proton
emitter Be are studied both theoretically and experimentally. Theoretical
studies are performed in a three-body hyperspherical-harmonics cluster model.
In the experimental studies, the ground state of Be was formed following
the decay of a C beam inelastically excited through
interactions with Be and C targets. Excellent agreement between theory and
experiment is obtained demonstrating the existence of complicated correlation
patterns which can elucidate the structure of Be and, possibly, of the
A=6 isobar.Comment: 17 pages, 21 figures, 5 table
Deep excursion beyond the proton dripline. I. Argon and chlorine isotope chains
The proton-unbound argon and chlorine isotopes have been studied by measuring trajectories
of their decay-in-flight products by using a tracking technique with micro-strip detectors. The
proton (1p) and two-proton (2p) emission processes have been detected in the measured angular
correlations “heavy-fragment”+p and “heavy-fragment”+p+p, respectively. The ground states of
the previously unknown isotopes 30Cl and 28Cl have been observed for the first time, providing the
1p separation energies Sp of −0.48(2) and −1.60(8) MeV, respectively. The relevant systematics of
1p and 2p separation energies have been studied theoretically in the core+p and core+p+p cluster
models. The first-time observed excited states of 31Ar allow to infer the 2p-separation energy S2p
of 6(34) keV for its ground state. The first-time observed state in 29Ar with S2p = −5.50(18) MeV
can be identified either as a ground or an excited state according to different systematics.Helmholtz Association grant IK-RU-002Helmholtz International Center for FAIR HIC for FAIRRussian Science Foundation grant No. 17-12-01367Polish National Science Center Contract No. UMO- 2015/17/B/ST2/00581Polish Ministry of Science and Higher Education Grant No. 0079/DIA/2014/43, Grant DiamentowyHelmholtz- CAS Joint Research Group grant HCJRG-10
Deep excursion beyond the proton dripline. II. Toward the limits of existence of nuclear structure
Prospects of experimental studies of argon and chlorine isotopes located far beyond the proton dripline are studied by using systematics and cluster models. The deviations from the widespread systematics observed in
28
,
29
Cl
and
29
,
30
Ar
have been theoretically substantiated, and analogous deviations have been predicted for the lighter chlorine and argon isotopes. The limits of nuclear structure existence are predicted for Ar and Cl isotopic chains, with
26
Ar
and
25
Cl
found to be the lightest sufficiently long-living nuclear systems. By simultaneous measurements of protons and
γ
rays following decays of such systems as well as their
β
-delayed emission, an interesting synergy effect may be achieved, which is demonstrated by the example of
30
Cl
and
31
Ar
ground-state studies. Such a synergy effect may be provided by the new EXPERT setup (EXotic Particle Emission and Radioactivity by Tracking) being operated inside the fragment separator and spectrometer facility at GSI, Darmstadt.Helmholtz Association de Alemania. IK-RU-002Russian Science Foundation. 17-12-01367Polish National Science Center. UMO2015/17/B/ST2/00581Polish Ministry of Science and Higher Education. 0079/DIA/2014/43Helmholtz- CAS Joint Research Group de Alemania. HCJRG-108Ministerio de Educación y Ciencia, España. FPA2016-77689-C2-1-RMinistry of Education, Youth and Sports de la República Checa. LTT17003 y LM201504
Spectroscopy of excited states of unbound nuclei 30 Ar and 29 Cl
Several states of proton-unbound isotopes
30
Ar
and
29
Cl
were investigated by measuring their in-flight decay products,
28
S
+ proton + proton and
28
S
+ proton, respectively. A refined analysis of
28
S
-proton angular correlations indicates that the ground state of
30
Ar
is located at
2
.
45
+
0.05
−
0.10
MeV above the two-proton emission threshold. The investigation of the decay mechanism of the
30
Ar
ground state demonstrates that it has the transition dynamics. In the “transitional” region, the correlation patterns of the decay products present a surprisingly strong sensitivity to the two-proton decay energy of the
30
Ar
ground state and the one-proton decay energy as well as the one-proton decay width of the
29
Cl
ground state. The comparison of the experimental
28
S
-proton angular correlations with those resulting from Monte Carlo simulations of the detector response illustrates that other observed
30
Ar
excited states decay by sequential emission of protons via intermediate resonances in
29
Cl
. Based on the findings, the decay schemes of the observed states in
30
Ar
and
29
Cl
were constructed. For calibration purposes and for checking the performance of the experimental setup, decays of the previously known states of a two-proton emitter
19
Mg
were remeasured. Evidences for one new excited state in
19
Mg
and two unknown states in
18
Na
were found.Helmholtz International Center for FAIR de Alemania (HIC for FAIR) IK-RU-002Russian Ministry of Education and Science. NSh-932.2014.2Russian Science Foundation. 17-12-01367Polish National Science Center. UMO-2011/01/B/ST2/01943Polish Ministry of Science and Higher Education. 0079/DIA/2014/43HelmholtzCAS Joint Research Group de Alemania. HCJRG-108Ministerio de Ciencia, Innovación y Universidades de España (MICINN). FPA2009-0884
Observation and spectroscopy of new proton-unbound isotopes 30ar and 29cl: an interplay of prompt two-proton and sequential decay
Previously unknown isotopes 30Ar and 29Cl have been identified by measurement of the trajectories of their in-flight decay products 28S+p+p and 28S+p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of 30Ar and 29Cl were found at 2.25+0.15−0.10 and 1.8±0.1 MeV above the two- and one-proton thresholds, respectively. The lowest states in 30Ar and 29Cl point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the 30Ar ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of 30Ar∗(2+) has been obtained by detecting two decay branches into the ground and first-excited states of the 28S fragment.Polish National Science Center UMO-2011/01/B/ST2/0194
Physical Growth and Nonverbal Intelligence: Associations in Zambia
Objective: To investigate normative developmental body mass index (BMI) trajectories and associations of physical growth indicators—height, weight, head circumference (HC), and BMI—with nonverbal intelligence in an understudied population of children from sub-Saharan Africa. Study design: A sample of 3981 students (50.8% male), grades 3-7, with a mean age of 12.75 years was recruited from 34 rural Zambian schools. Children with low scores on vision and hearing screenings were excluded. Height, weight, and HC were measured, and nonverbal intelligence was assessed using the Universal Nonverbal Intelligence Test, Symbolic Memory subtest and Kaufman Assessment Battery for Children, Second Edition, Triangles subtest. Results: Students in higher grades had a higher BMI over and above the effect of age. Girls had a marginally higher BMI, although that for both boys and girls was approximately 1 SD below the international Centers for Disease Control and Prevention and World Health Organization norms. When controlling for the effect of age, nonverbal intelligence showed small but significant positive relationships with HC (r = 0.17) and BMI (r = 0.11). HC and BMI accounted for 1.9% of the variance in nonverbal intelligence, over and above the contribution of grade and sex. Conclusion: BMI-for-age growth curves of Zambian children follow observed worldwide developmental trajectories. The positive relationships between BMI and intelligence underscore the importance of providing adequate nutritional and physical growth opportunities for children worldwide and in sub-Saharan Africa in particular. Directions for future studies are discussed with regard to maximizing the cognitive potential of all rural African children
SURVEY OF THE DEPENDENCE ON TEMPERATURE OF THE COERCIVITY OF GARNET-FILMS
The temperature dependence of the domain-wall coercive field of epitaxial magnetic garnets films
has been investigated in the entire temperature range of the ferrimagnetic phase, and has been found
to be described by a set of parametric exponents. In subsequent temperature regions different slopes
were observed, with breaking points whose position was found to be sample dependent. A survey
ba.ed on literature Data as well as on a large number of our own samples shows the general
existence of this piecewise exponential dependence and the presence of the breaking points. This
type of domain-wall coercive field temperature dependence was found in all samples in the large
family of the epitaxial garnets (about 30 specimens of more than ten chemical compositionsj and
also in another strongly anisotropic material (TbFeCo)
Three-body correlations in direct reactions: Example of Be populated in reaction
The Be continuum states were populated in the charge-exchange reaction
H(Li,Be) collecting very high statistics data ( events) on the three-body ++ correlations. The
Be excitation energy region below MeV is considered, where the
data are dominated by contributions from the and states. It is
demonstrated how the high-statistics few-body correlation data can be used to
extract detailed information on the reaction mechanism. Such a derivation is
based on the fact that highly spin-aligned states are typically populated in
the direct reactions.Comment: submitted to Physical Review
Getting something out of nothing: Analyzing patterns of null responses to improve data collection methods in sub-Saharan Africa
Careful development and adaptation of assessments is imperative for cultural psychological research. However, despite the best efforts, the use of assessments in new contexts can reveal atypical and/or unexpected patterns of performance. We found this to be the case in the testing of assessments to be used for a larger investigation of Specific Reading Disabilities in Zambia. In a sample of 207 children (100 female) from grades 2 to 7, we illustrated that assessment characteristics (i.e., stimulus type, answer choice, and response type) differentially impact patterns of responsiveness. The number of missing values was highest for assessments that (1) used written stimuli, (2) had an open-ended answer choice, and (3) required an action response. Age and socio-economic status explained some of the variance in responsiveness in selected, but not all assessments. Consideration of the impact of stimulus and response types when adapting assessments cross-linguistically and cross-culturally is essential
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