334 research outputs found
Cluster structures in B
Structures of excited states in B are investigated with a method of
- constraint antisymmetrized molecular dynamics in combination
with the generator coordinate method. Various excited states with developed
cluster core structures are suggested in positive- and negative-parity states.
For negative-parity states, we suggest a band with a cluster
structure. This band starts from the state and can correspond to
the experimental band observed recently. In positive-parity states, two
core cluster structures with surrounding nucleons are found. A
band is suggested to be constructed from a remarkably developed
cluster structure with a large prolate deformation. We discuss features of the
cluster structure in association with molecular orbital structures of
Be.Comment: 13 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1004.495
Cluster structures of excited states in C
Structures of excited states in C are investigated with a method of
- constraint antisymmetrized molecular dynamics in combination
with the generator coordinate method. Various excited states with the developed
-cluster core structures are suggested in positive- and
negative-parity states. In the positive-parity states, triaxial deformed and
linear-chain structures are found to construct excited bands. Interestingly,
Be+ correlation is found in the cluster states above the
Be+ threshold energy.Comment: 17 pages, 9 figure
Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei
We present a review of recent works on clustering phenomena in unstable
nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in
these decades have uncovered novel types of clustering phenomena brought about
by the excess neutrons. Among them, this review focuses on the molecule-like
structure of unstable nuclei. One of the earliest discussions on the clustering
in unstable nuclei was made for neutron-rich Be and B isotopes. AMD
calculations predicted that the ground state clustering is enhanced or reduced
depending on the number of excess neutrons. Today, the experiments are
confirming this prediction as the change of the proton radii. Behind this
enhancement and reduction of the clustering, there are underlying shell effects
called molecular- and atomic-orbits. These orbits form covalent and ionic
bonding of the clusters analogous to the atomic molecules. It was found that
this "molecular-orbit picture" reasonably explains the low-lying spectra of Be
isotopes. The molecular-orbit picture is extended to other systems having
parity asymmetric cluster cores and to the three cluster systems. O and Ne
isotopes are the candidates of the former, while the linear chains in
C isotopes are the latter. For both subjects, many intensive studies are now in
progress. We also pay a special attention to the observables which are the
fingerprint of the clustering. In particular, we focus on the monopole and
dipole transitions which are recently regarded as good probe for the
clustering. We discuss how they have and will reveal the exotic clustering.Comment: 96 pages, 44 figure
Dineutron correlations in nuclear surface
Two-neutron correlation in quasi two-dimensional (2D) neutron matter is studied by means of the BCS theory to understand formation of nn pairs in nuclear surface of neutron-rich nuclei. The spin-zero nn pair correlation in low density neutron systems confined in an infinite slab is investigated in a simplified model that neutron motion of one direction is frozen. It is found that, when the slab is thin enough, the nn pairing gap enhances and the size shrinking of nn Cooper pair occurs at finite low-density region in the quasi-2D system
Honesty mediates the relationship between serotonin and reaction to unfairness
How does one deal with unfair behaviors? This subject has long been investigated by various disciplines including philosophy, psychology, economics, and biology. However, our reactions to unfairness differ from one individual to another. Experimental economics studies using the ultimatum game (UG), in which players must decide whether to accept or reject fair or unfair offers, have also shown that there are substantial individual differences in reaction to unfairness. However, little is known about psychological as well as neurobiological mechanisms of this observation. We combined a molecular imaging technique, an economics game, and a personality inventory to elucidate the neurobiological mechanism of heterogeneous reactions to unfairness. Contrary to the common belief that aggressive personalities (impulsivity or hostility) are related to the high rejection rate of unfair offers in UG, we found that individuals with apparently peaceful personalities (straightforwardness and trust) rejected more often and were engaged in personally costly forms of retaliation. Furthermore, individuals with a low level of serotonin transporters in the dorsal raphe nucleus (DRN) are honest and trustful, and thus cannot tolerate unfairness, being candid in expressing their frustrations. In other words, higher central serotonin transmission might allow us to behave adroitly and opportunistically, being good at playing games while pursuing self-interest. We provide unique neurobiological evidence to account for individual differences of reaction to unfairness
Effects of sports participation on psychiatric symptoms and brain activations during sports observation in schizophrenia
Weight gain has been identified as being responsible for increased morbidity and mortality rates of schizophrenia patients. For the management of weight gain, exercise is one of the most acknowledged interventions. At the same time, exercise and sports have been recognized for their positive impact on psychiatric symptoms of schizophrenia. However, the neurobiological basis for this remains poorly understood. We aimed to examine the effect of sports participation on weight gain, psychiatric symptoms and brain activation during sports observation in schizophrenia patients. Thirteen schizophrenia patients who participated in a 3-month program, including sports participation and 10 control schizophrenia patients were studied. In both groups, body mass index (BMI), Positive and Negative Syndrome Scale (PANSS), and brain activation during observation of sports-related actions measured by functional magnetic resonance imaging were accessed before and after a 3-month interval. BMI and general psychopathology scale of PANSS were significantly reduced in the program group but not in the control group after a 3-month interval. Compared with baseline, activation of the body-selective extrastriate body area (EBA) in the posterior temporal-occipital cortex during observation of sports-related actions was increased in the program group. In this group, increase in EBA activation was associated with improvement in the general psychopathology scale of PANSS. Sports participation had a positive effect not only on weight gain but also on psychiatric symptoms in schizophrenia. EBA might mediate these beneficial effects of sports participation. Our findings merit further investigation of neurobiological mechanisms underlying the therapeutic effect of sports for schizophrenia
From the stable to the exotic: clustering in light nuclei
A great deal of research work has been undertaken in alpha-clustering study
since the pioneering discovery of 12C+12C molecular resonances half a century
ago. Our knowledge on physics of nuclear molecules has increased considerably
and nuclear clustering remains one of the most fruitful domains of nuclear
physics, facing some of the greatest challenges and opportunities in the years
ahead. The occurrence of "exotic" shapes in light N=Z alpha-like nuclei is
investigated. Various approaches of the superdeformed and hyperdeformed bands
associated with quasimolecular resonant structures are presented. Evolution of
clustering from stability to the drip-lines is examined: clustering aspects
are, in particular, discussed for light exotic nuclei with large neutron excess
such as neutron-rich Oxygen isotopes with their complete spectroscopy.Comment: 15 pages, 5 figures, Presented at the International Symposium on "New
Horizons in Fundamental Physics - From Neutrons Nuclei via Superheavy
Elements and Supercritical Fields to Neutron Stars and Cosmic Rays" held at
Makutsi Safari Farm, South Africa, December 23-29, 2015. arXiv admin note:
substantial text overlap with arXiv:1402.6590, arXiv:1303.0960,
arXiv:1408.0684, arXiv:1011.342
- …