Weyl law for open systems with sharply divided mixed phase space

A generalization of the Weyl law to systems with a sharply divided mixed phase space is proposed. The ansatz is composed of the usual Weyl term which counts the number of states in regular islands and a term associated with sticky regions in phase space. For a piecewise linear map, we numerically check the validity of our hypothesis, and find good agreement not only for the case with a sharply divided phase space, but also for the case where tiny island chains surround the main regular island. For the latter case, a non-trivial power law exponent appears in the survival probability of classical escaping orbits, which may provide a clue to develop the Weyl law for more generic mixed systems.Comment: 8 pages, 14 figure

Effect of Water on the Manifestation of the Reaction Selectivity of Nitrogen-Doped Graphene Nanoclusters toward Oxygen Reduction Reaction

We investigated the selectivity of N-doped graphene nanoclusters (N-GNCs) toward the oxygen reduction reaction (ORR) using first-principles calculations within the density functional theory. The results show that the maximum electrode potentials (UMax) for the four-electron (4e–) pathway are higher than those for the two-electron (2e–) pathway at almost all of the reaction sites. Thus, the N-GNCs exhibit high selectivity for the 4e– pathway, that is, the 4e– reduction proceeds preferentially over the 2e– reduction. Such high selectivity results in high durability of the catalyst because H2O2, which corrodes the electrocatalyst, is not generated. For the doping sites near the edge of the cluster, the value of UMax greatly depends on the reaction sites. However, for the doping sites around the center of the cluster, the reaction-site dependence is hardly observed. The GNC with a nitrogen atom around the center of the cluster exhibits higher ORR catalytic capability compared with the GNC with a nitrogen atom in the vicinity of the edge. The results also reveal that the water molecule generated by the ORR enhances the selectivity toward the 4e– pathway because the reaction intermediates are significantly stabilized by water

Structural stability and aromaticity of pristine and doped graphene nanoflakes

We have quantitatively investigated the relationship between the aromaticity and structural stability of graphene nanoflakes (GNFs) using first-principles calculations. The aromaticity of each six-membered ring of GNFs is evaluated with the nucleus-independent chemical shifts (NICS). We have found that for armchair-edge GNFs, the degree of stability, that is, the edge formation energy, is proportional to the average NICS for all six-membered rings. Even for nitrogen- and boron-doped GNFs, the average NICS strongly correlates with the doping formation energy. Our results indicate that NICS is a good measure not only for the aromaticity but also for the structural stability of pristine/doped nanographene systems

First-principles study of locally disordered structures of Mn-induced GaAs(001)-(2 × 2) surface

Various atomic arrangements of the Mn-induced GaAs(001) surface, consisting of one Ga–As dimer and one Mn atom in the (2 × 2) unit, have been investigated by first-principles calculations. The most stable arrangement is reasonable in view of the classical electrostatic theory. It has been revealed that the topmost Ga–As dimers tend to be aligned along the [11 ̅0] direction, while they are less ordered along the [110] direction. These anisotropic orderings, that is, anisotropic interactions, imply that the Mn atom, which is located between the Ga–As dimers, enhances the local electrostatic interaction between the dimers along the [11 ̅0] direction, as a result of the dielectric anisotropy at the surface

Can We Extract Lambda-Lambda Interaction from Two-Particle Momentum Correlation ?

We analyze the invariant mass spectrum of Lambda-Lambda in $^{12}C(K^-,K^+ Lambda Lambda)$ reaction at P(K^+)=1.65 GeV/c by using a combined framework of IntraNuclear Cascade (INC) model and the correlation function technique. The observed enhancement at low-invariant masses can be well reproduced with attractive Lambda-Lambda interactions with the scattering length either in the range a = -6 \sim -4 fm (no bound state) or a = 7 \sim 12 fm (with bound state). We also discuss Lambda-Lambda correlation functions in central relativistic heavy-ion collisions as a possible way to eliminate this discrete ambiguity.Comment: 4 Pages, LaTeX with psfig, embedded 4 ps figures. Talk given at KEK-Tanashi Int. Symp. on "Physics of Hadrons and Nuclei", 14-17 Dec. 1998, Tokyo, Japan, Nuclear Physics A, to appea

Mechanism of stabilization and magnetization of impurity-doped zigzag graphene nanoribbons

Doping is an efficient way to modify the electronic structure of graphene. Although there have been a considerable number of studies on the electronic structure of impurity-doped graphene, every study has suggested a different interpretation of the appearance of impurity levels of dopants located near the so-called zigzag edge of graphene nanoribbons (GNRs). Here, we propose a charge transfer model that satisfactorily explains the change in electronic structure upon N(B) doping of zigzag GNR (ZGNR). The structural stability and electronic structure of the doped ZGNR have been investigated using first-principles calculations based on the density functional theory. The formation energy of doping increases as a function of the distance between the N(B) atom and the zigzag edge, and two tendencies are observed depending on whether the dopant is an odd or even number of sites away from the zigzag edge. Such peculiar behavior of the formation energy can be successfully explained by charge transfer between the so-called edge state localized at the edge and the 2p-state of the dopant. Such an electron (hole) transfer leads to the compensation (disappearance) of the local spin-magnetic moment at one side of the ZGNR, manifesting in the ferromagnetic ground state of ZGNR

Attitudes toward and current status of disclosure of secondary findings from next-generation sequencing: a nation-wide survey of clinical genetics professionals in Japan

The management of secondary findings (SFs), which are beyond the intended purpose of the analysis, from clinical comprehensive genomic analysis using next generation sequencing (NGS) presents challenges. Policy statements regarding their clinical management have been announced in Japan and other countries. In Japan, however, the current status of and attitudes of clinical genetics professionals toward reporting them are unclear. We conducted a questionnaire survey of clinical genetics professionals at two time points (2013 and 2019) to determine the enforcement of the SF management policy in cases of comprehensive genetic analysis of intractable diseases and clinical cancer genome profiling testing. According to the survey findings, 40% and 70% of the respondents stated in the 2013 and 2019 surveys, respectively, that they had an SF policy in the field of intractable diseases, indicating that SF policy awareness in Japan has changed significantly in recent years. Furthermore, a total of 80% of respondents stated that their facility had established a policy for clinical cancer genome profiling testing in the 2019 survey. In both surveys, the policies included the selection criteria for genes to be disclosed and the procedure to return SFs, followed by recommendations and proposals regarding SFs in Japan and other countries. To create a better list of the genes to be disclosed, further examination is needed considering the characteristics of each analysis

Down-regulation of transcription elogation factor A (SII) like 4 (TCEAL4) in anaplastic thyroid cancer

BACKGROUND: Anaplastic thyroid cancer (ATC) is one of the most aggressive human malignancies and appears to arise mainly from transformation of pre-existing differentiated thyroid cancer (DTC). However, the carcinogenic mechanism of anaplastic transformation remains unclear. Previously, we investigated specific genes related to ATC based on gene expression profiling using cDNA microarray analysis. One of these genes, transcription elongation factor A (SII)-like 4 (TCEAL4), encodes a member of the transcription elongation factor A (SII)-like gene family. The detailed function of TCEAL4 has not been described nor has any association between this gene and human cancers been reported previously. METHODS: To investigate the role of TCEAL4 in ATC carcinogenesis, we examined expression levels of TCEAL4 in ACLs as well as in other types of thyroid cancers and normal human tissue. RESULTS: Expression of TCEAL4 was down-regulated in all 11 ACLs as compared to either normal thyroid tissues or papillary and follicular thyroid cancerous tissues. TCEAL4 was expressed ubiquitously in all normal human tissues tested. CONCLUSION: To our knowledge, this is the first report of altered TCEAL4 expression in human cancers. We suggest that loss of TCEAL4 expression might be associated with development of ATC from DTC. Further functional studies are required