450 research outputs found
Coupled-channels analyses for large-angle quasi-elastic scattering in massive systems
We discuss in detail the coupled-channels approach for the large-angle
quasi-elastic scattering in massive systems, where many degrees of freedom may
be involved in the reaction. We especially investigate the effects of single,
double and triple phonon excitations on the quasi-elastic scattering for
Ti,Cr,Fe,Ni and ZnPb systems, for
which the experimental cross sections have been measured recently. We show that
the present coupled-channels calculations well account for the overall width of
the experimental barrier distribution for these systems. In particular, it is
shown that the calculations taking into account single quadrupole phonon
excitations in Ti and triple octupole phonon excitations in Pb
reasonably well reproduce the experimental quasi-elastic cross section and
barrier distribution for the TiPb reaction. On the other hand,
Cr,Fe,Ni and ZnPb systems seem to require
the double quadrupole phonon excitations in the projectiles in order to
reproduce the experimental data.Comment: 11 pages, 6 figure
Development of genomic simple sequence repeat markers for yam
Yam (
Dioscorea
spp.) is a major staple crop
widely cultivated for its starchy tubers. To date,
very few marker resources are publicly avail
-
able as tools for genetic and genomic studies of
this economically important crop. In this study,
90 simple sequence repeat (SSR) markers were
developed from an enriched genomic library of
yellow Guinea yam (
D. cayenensis
Lam.). Cross-
amplification revealed that 85 (94.4%) and 51
(56.7%) of these SSRs could be successfully
transferred to the two major cultivated species
of
D. rotundata
Poir. and
D. alata
L., respec
-
tively. Polymorphisms in 30 markers selected
on the basis of reliability and reproducibility of
DNA bands were evaluated using a panel of 12
D. cayenensis
, 48
D. rotundata
, and 48
D. alata
accessions. Accordingly, number of alleles
per locus ranged from 2 to 8 in
D. cayenensis
(mean = 3.9), 3 to 30 in
D. rotundata
(mean =
13.9), and 2 to 22 in
D. alata
(mean = 12.1). The
average observed and expected heterozygosi
-
ties were 0.156 and 0.634 (
D. cayenensis
), 0.326
and 0.853 (
D. rotundata
), and 0.247 and 0.836
(
D. alata
), respectively. Clustering based on six
SSRs that were polymorphic in at least four of
the five cultivated
Dioscorea
species studied,
including
D. cayenensis
,
D. rotundata
,
D. alata
,
D. dumetorum
(Kunth) Pax., and
D. bulbifera
L.,
detected groups consistent with the phyloge
-
netic relationships of the species except for
D.
dumetorum
. These new SSR markers are invalu
-
able resources for applications such as genetic
diversity analysis and marker-assisted breedingYam (
Dioscorea
spp.) is a major staple crop
widely cultivated for its starchy tubers. To date,
very few marker resources are publicly avail
-
able as tools for genetic and genomic studies of
this economically important crop. In this study,
90 simple sequence repeat (SSR) markers were
developed from an enriched genomic library of
yellow Guinea yam (
D. cayenensis
Lam.). Cross-
amplification revealed that 85 (94.4%) and 51
(56.7%) of these SSRs could be successfully
transferred to the two major cultivated species
of
D. rotundata
Poir. and
D. alata
L., respec
-
tively. Polymorphisms in 30 markers selected
on the basis of reliability and reproducibility of
DNA bands were evaluated using a panel of 12
D. cayenensis
, 48
D. rotundata
, and 48
D. alata
accessions. Accordingly, number of alleles
per locus ranged from 2 to 8 in
D. cayenensis
(mean = 3.9), 3 to 30 in
D. rotundata
(mean =
13.9), and 2 to 22 in
D. alata
(mean = 12.1). The
average observed and expected heterozygosi
-
ties were 0.156 and 0.634 (
D. cayenensis
), 0.326
and 0.853 (
D. rotundata
), and 0.247 and 0.836
(
D. alata
), respectively. Clustering based on six
SSRs that were polymorphic in at least four of
the five cultivated
Dioscorea
species studied,
including
D. cayenensis
,
D. rotundata
,
D. alata
,
D. dumetorum
(Kunth) Pax., and
D. bulbifera
L.,
detected groups consistent with the phyloge
-
netic relationships of the species except for
D.
dumetorum
. These new SSR markers are invalu
-
able resources for applications such as genetic
diversity analysis and marker-assisted breedin
β-delayed neutron and γ-ray spectroscopy of ^<17>C utilizing spin-polarized ^<17>B
Excited states in ^C were investigated through the measurement of β -delayed neutrons and γ rays emitted in the β decay of ^B. In the measurement, three negative-parity states and two inconclusive states were identified in ^C above the neutron threshold energy, and seven γ lines were identified in a β -delayed multiple neutron emission of the ^Bβ decay. From these transitions, the β-decay scheme of ^B was determined. In particular, a de-excitation 1766-keVγ line from the first excited state of ^C was observed in coincidence with the emitted β-delayed neutrons, and this changes the previously reported β-decay scheme of ^B and level structure of ^C. In the present work, the β-NMR technique is combined with the β-delayed particle measurements using a fragmentation-induced spin-polarized ^B beam. This new scheme allows us to determine the spin parity of β-decay feeding excited states based on the difference in the discrete β-decay asymmetry parameters, provided the states are connected through the Gamow-Teller transition. In this work, I^π=1/2^−, 3/2^−, and (5/2^−) are assigned to the observed states at E_x = 2.71(2), 3.93(2), and 4.05(2) MeV in ^C, respectively
Recent experimental results in sub- and near-barrier heavy ion fusion reactions
Recent advances obtained in the field of near and sub-barrier heavy-ion
fusion reactions are reviewed. Emphasis is given to the results obtained in the
last decade, and focus will be mainly on the experimental work performed
concerning the influence of transfer channels on fusion cross sections and the
hindrance phenomenon far below the barrier. Indeed, early data of sub-barrier
fusion taught us that cross sections may strongly depend on the low-energy
collective modes of the colliding nuclei, and, possibly, on couplings to
transfer channels. The coupled-channels (CC) model has been quite successful in
the interpretation of the experimental evidences. Fusion barrier distributions
often yield the fingerprint of the relevant coupled channels. Recent results
obtained by using radioactive beams are reported. At deep sub-barrier energies,
the slope of the excitation function in a semi-logarithmic plot keeps
increasing in many cases and standard CC calculations over-predict the cross
sections. This was named a hindrance phenomenon, and its physical origin is
still a matter of debate. Recent theoretical developments suggest that this
effect, at least partially, may be a consequence of the Pauli exclusion
principle. The hindrance may have far-reaching consequences in astrophysics
where fusion of light systems determines stellar evolution during the carbon
and oxygen burning stages, and yields important information for exotic
reactions that take place in the inner crust of accreting neutron stars.Comment: 40 pages, 63 figures, review paper accepted for EPJ
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