This study focuses on the expansion of Phaseolus vulgaris in Europe. The pathways of distribution of beans into and across Europe were very complex, with several introductions from the New World that ...were combined with direct exchanges between European and other Mediterranean countries. We have analyzed here six chloroplast microsatellite (cpSSR) loci and two unlinked nuclear loci (for phaseolin types and Pv-shatterproof1). We have assessed the genetic structure and level of diversity of a large collection of European landraces of P. vulgaris (307) in comparison to 94 genotypes from the Americas that are representative of the Andean and Mesoamerican gene pools. First, we show that most of the European common bean landraces (67%) are of Andean origin, and that there are no strong differences across European regions for the proportions of the Andean and Mesoamerican gene pools. Moreover, cytoplasmic diversity is evenly distributed across European regions. Secondly, the cytoplasmic bottleneck that was due to the introduction of P. vulgaris into the Old World was very weak or nearly absent. This is in contrast to evidence from nuclear analyses that have suggested a bottleneck of greater intensity. Finally, we estimate that a relatively high proportion of the European bean germplasm (about 44%) was derived from hybridization between the Andean and Mesoamerican gene pools. Moreover, although hybrids are present everywhere in Europe, they show an uneven distribution, with high frequencies in central Europe, and low frequencies in Spain and Italy. On the basis of these data, we suggest that the entire European continent and not only some of the countries therein can be regarded as a secondary diversification center for P. vulgaris. Finally, we outline the relevance of these inter-gene pool hybrids for plant breeding.
Atomic nuclei with certain combinations of proton and neutron numbers can adopt reflection-asymmetric or octupole-deformed shapes at low excitation energy. These nuclei present a promising avenue in ...the search for a permanent atomic electric dipole moment—the existence of which has implications for physics beyond the Standard Model of particle physics. Theoretical studies have suggested that certain thorium isotopes may have large octupole deformation. However, due to experimental challenges, the extent of the octupole collectivity in the low-energy states in these thorium nuclei has not yet been demonstrated. Here, we report measurements of the lifetimes of low-energy states in 228Th (Z = 90) with a direct electronic fast-timing technique, the mirror symmetric centroid difference method. From lifetime measurements of the low-lying Jπ = 1− and Jπ = 3− states, the E1 transition probability rates and the intrinsic dipole moment are determined. The results are in agreement with those of previous theoretical calculations, allowing us to estimate the extent of the octupole deformation of 228Th. This study indicates that the nuclei 229Th and 229Pa (Z = 91) may be good candidates for the search for a permanent atomic electric dipole moment.The intrinsic dipole moment of 228Th is reported, from which the degree of the nucleus’s octupole deformation is estimated, suggesting that 229Th and 229Pa may be suitable candidates for the search for a permanent atomic electric dipole moment.
Phaseolus coccineus
L. is closely related to
P. vulgaris
and is the third most important cultivated
Phaseolus
species. Little is known about the patterns of its diversity. In this work, a ...representative collection of its worldwide diversity was initially developed. The collection includes 28 wild forms (WFs) and 52 landraces (LRs) from Mesoamerica (the crop domestication area), and 148 LRs from Europe (where the crop was introduced in the sixteenth century). The collection was studied by using 12 SSR molecular markers that were developed for the
P. vulgaris
genome. They were proved to be effective and reliable in
P. coccineus
in this work. Fourteen LRs of
P. dumosus
(previously identified as a subspecies of
P. coccineus
) were also studied. The genetic diversity, population structure and phylogenetic relationships were investigated. The results indicate that: (a) the European and Mesoamerican gene pools are clearly differentiated, (b) a certain reduction of diversity occurred with introduction into Europe, and (c) the Mesoamerican LRs (
P. dumosus
included) and WFs are closely related and are connected by a high gene flow. Inferences on the domestication process of
P. coccineus
are also presented. This study provides a picture of the genetic diversity distribution and outcomes with introduction into the Old World, which was not available before. It also underlines that the genetic diversity of both WFs and LRs is an important source for
Phaseolus
spp. breeding programs and deserves to be preserved in situ and ex situ.
In this contribution it is explored whether γ-ray spectroscopy following β decay with high Q values from mother nuclei with low ground-state spin can be exploited as a probe for the pygmy dipole ...resonance. The suitability of this approach is demonstrated by a comparison between data from photon scattering, ^{136}Xe(γ,γ^{'}), and ^{136}I J_{0}^{π}=(1^{-})→^{136}Xe^{*} β-decay data. It is demonstrated that β decay populates 1^{-} levels associated with the pygmy dipole resonance, but only a fraction of those. The complementary insight into the wave functions probed by β decay is elucidated by calculations within the quasiparticle phonon model. It is demonstrated that β decay dominantly populates complex configurations, which are only weakly excited in inelastic scattering experiments.
Half-lives of the low-lying yrast states of 212Po have been measured using the delayed coincidence fast-timing method. We report on the first measurement of the 41+ half-life, as well as a new ...measurement of the 61+ half-life with improved accuracy compared to previous studies. The extracted lifetime of the 41+ and 61+ state have been determined to be 100(14) ps and 1.66(28) ns respectively. With these measurements, precise values are now available for the reduced transition strengths B(E2) of all ground state band levels in 212Po up to the first 8+ state, in particular B(E2; 41+→21+) = 9.4(13) W.u. and B(E2;61+→41+) = 8.7(15) W.u. Comparison of the new available data with an α-clustering model calculation provides evidence that the inclusion of the α-cluster degree of freedom significantly improves agreement with experimental data compared to earlier shell model calculations.
The nature of the high-lying final levels of the 96Ygsβ decay, one of the three most important contributors to the high-energy reactor antineutrino spectrum, has been investigated in high-resolution ...γ-ray spectroscopy following the β decay as well as in a campaign of inelastic photon scattering experiments. The comprehensive approach establishes 1− levels associated with the Pygmy Dipole Resonance as high-lying final levels in the β decay. Branching ratios extracted from β decay complement photon scattering and allow the absolute E1 excitation strength to be determined for levels populated in both reactions. The combined data represents a comprehensive approach to the wavefunction of the 1− levels below the Qβ value, which are investigated in the Quasiparticle Phonon Model. The calculations reveal that the components populated in β decay contribute only with small amplitudes to the complex wavefunction of these 1− levels. A comparison of the β decay results to data from total absorption γ-ray spectroscopy demonstrates a good agreement between both measurements.
.
For the
N
= 50-56 zirconium (
Z
= 40) and molybdenum (
Z
= 42) isotopes, the evolution of subshells is evaluated by extracting the effective single-particle energies from available ...particle-transfer data. The extracted systematic evolution of neutron subshells and the systematics of the excitation energy of the octupole phonons provide evidence for type-II shape coexistence in the Zr isotopes. Employing a simplistic approach, the relative effective single-particle energies are used to estimate whether the formation of low-lying octupole-isovector excitations is possible at the proposed energies. The results raise doubts about this assignment.
We present the results from an experiment dedicated to measure the lifetime of the
2
2
+
state, candidate for the one-phonon mixed-symmetry state, of
208
Po. This nucleus was studied in the
α
...-transfer reaction
204
Pb(
12
C,
8
Be)
208
Po and the lifetime of the
2
2
+
state was determined by utilizing the Doppler-shift attenuation method. The experimental data show that the
2
2
+
state decays with a sizable
M
1 transition to the
2
1
+
state revealing its isovector nature.
There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity ...in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
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