The spin and orbital magnetic moments, as well as the magnetic anisotropy energy (MAE), of small 4d transition metal (TM) clusters are systematically studied by using the spin-orbit coupling (SOC) implementation of the density-functional theory (DFT). The effects of spin-orbit interactions on geometrical structures and spin moments are too weak to alternate relative stabilities of different low-lying isomers. Remarkable orbital contributions to cluster magnetic moments are identified in Ru, Rh, and Pd clusters, in contrast to immediate quenching of the atomic orbital moment at the dimer size in other elemental clusters. More interestingly, there is always collinearity between total spin and orbital moments (antiferromagnetic or ferromagnetic coupling depends on the constituent atoms whose 4d subshell is less or more than half-filled). The clusters preserve the validity of Hund's rules for the sign of orbital moment. The calculations on MAEs reveal the complicated changes of the easy axes in different structures. The perturbation theory and the first-principles calculations are compared to emphasize how MAEs evolve with cluster size. Finally, large orbital moments combined with strong spin-orbit coupling are proposed to account for large MAEs in Ru, Rh, and Pd clusters.
Together, results supported contentions that exposure to depictions of physical exercise corresponds to reduced activation of reward centers and heightened activation in regions associated with negative affect regulation among O-W women compared with leaner peers.
Cheaper permanent magnetic nanostructures with magnetic properties equivalent to those of noble-metal or rare-earth nanomagnets have been experimentally developed for their potential applications in ultrahigh storage densities in magnetic memory. To date, their intrinsic magnetic properties are not well understood under the micro-level of local atomic arrangements and electronic structures. In this work, we performed theoretical investigations on the CoW bulk, the clean surface, nanoclusters, and the Co|CoW bilayers and superlattices for their geometrical structures, magnetic moments, and magnetic anisotropy energies (MAEs). We found that the CoW nanostructures we constructed are stable and have the local minima in the energetic landscape, whose stabilities increase with increasing proportion of W and cluster size. The Co and W atoms in clusters are antiferromagnetically coupled, and their local magnetic moments decrease with increasing proportion of W. The breakdown of the Hund's third rule in W atoms observed in experiment can be interpreted as the competition between the intra-atomic spin-orbit coupling in W atoms and interatomic Co-W hybridizations. The highest MAE of about a few tens of meV is obtained in small cluster sizes, whereas it is an order of magnitude reduction in large cluster sizes. The magnetic systems of CoW clean surface, Co|CoW bilayer and superlattice can present large MAEs, and their easy-axes of magnetization are perpendicular to the (001) surface. Our calculated MAEs are of the same order of magnitude as that of the experimental measurements, and the electronic origin is revealed through the second-order perturbation method.
A large cross section for e+e~ -* A+A" pair production near its threshold provides an opportunity to study the charm baryon A+ /A " at a r-charm factory with e+e~ colhsions. We call for the determination of the A+/A~ spin using the process e+e~ -* AfAj, A+ -* pK°s, and we present a formula and a method to estimate the statistical significance for spin assignment J = \ and J = A Monte Carlo study shows that the significance is sensitive to the number of observed events. A few hundred observed signal events will yield the statistical significance larger than five standard deviations.
Psychological theories have implicated an active role of the default mode network (DMN) in natural speech comprehension. However, as listeners need to keep tracking the external audio streams, the DMN is regularly de-activated and anticorrelated with externally-oriented networks. Such a pattern has been interpreted as the suppression of the DMN to support externally-oriented cognitive processes. The current study aims to resolve this seeming contradiction. Brain activities from a speaker telling autobiographical stories and a group of participants (N = 62) listening to the recordings were collected with fMRI. By analyzing the listeners' brains alone, we found the DMN was deactivated during speech listening relative to a fixation period and anticorrelated with the task-positive perisylvian language network (pLN). Dynamic Causal Modeling showed the pLN had inhibitory influence on the DMN, whereas the DMN had excitatory influence on the pLN. Further between-brain analyses revealed the activities of DMN in the listener's brain were tightly coupled with the activities of the homologous network in the speaker's brain. Significant interbrain couplings were also observed in the pLN, but were weaker and faded quicker. Moreover, listeners showing stronger coupling responses to the speaker in the DMN understood the speech better, and tended to exhibit more positive DMN -to-pLN effective connections. We conclude that the DMN may occupy an internal system that works cooperatively with the externally-oriented pLN to support narrative speech comprehension.
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