Atomic structure and magnetism of the Au-Ga-Ce 1/1 approximant crystal

We report a new Au-Ga-Ce 1/1 approximant crystal (AC) which possesses a significantly wide single-phase region of 53 - 70 at% Au and 13.6 - 15.1 at% Ce. Single crystal X-ray structural analyses reveal the existence of two types of structural degrees of freedom, i.e., the Au/Ga mixing sites and the fractional Ce occupancy site: the former enables a large variation in the electron concentration and the latter allows a variation in the occupancy of a magnetic impurity atom at the center of the Tsai-type cluster. Following these findings, the influences of two types of structural modifications on the magnetism are thoroughly investigated by means of magnetic susceptibility and specific heat measurements on the Au-Ga-Ce 1/1 AC. The spin-glass (SG) state is found to be the ground state over the entire single-phase region, showing a robust nature of the SG state against both structural modifications. In addition, a gigantic specific heat (C/T) is commonly observed at low temperatures for all the compositions, which is consistently explained as a consequence of the spin-freezing phenomenon, not of a heavy Fermion behavior as reported elsewhere. Moreover, the origin of the SG state in the 1/1 Au-Ga-Ce AC is attributed to the existence of non-magnetic atom disorder in the Au/Ga mixing sites. Furthermore, a Kondo behavior is observed in the electrical resistivity at low temperatures, which is enhanced by increasing the Ce concentration, verifying that a Ce atom introduced at the cluster center behaves as a Kondo impurity for the first time.Comment: 8 pages, 4 figure

Unveiling exotic magnetic phase diagram of a non-Heisenberg quasicrystal approximant

A magnetic phase diagram of the non-Heisenberg Tsai-type 1/1 Au-Ga-Tb approximant crystal (AC) has been established across a wide electron-per-atom (e/a) range via magnetization and powder neutron diffraction measurements. The diagram revealed exotic ferromagnetic (FM) and antiferromagnetic (AFM) orders that originate from the unique local spin icosahedron common to icosahedral quasicrystals (iQCs) and ACs; The noncoplanar whirling AFM order is stabilized as the ground state at the e/a of 1.72 or less whereas a noncoplanar whirling FM order was found at the larger e/a of 1.80, with magnetic moments tangential to the Tb icosahedron in both cases. Moreover, the FM/AFM phase selection rule was unveiled in terms of the nearest neighbour (J1) and next nearest neighbour (J2) interactions by numerical calculations on a non-Heisenberg single icosahedron. The present findings will pave the way for understanding the intriguing magnetic orders of not only non-Heisenberg FM/AFM ACs but also non-Heisenberg FM/AFM iQCs, the latter of which are yet to be discovered

Thermal dependency of shell growth, microstructure, and stable isotopes in laboratory‐reared Scapharca broughtonii (Mollusca: Bivalvia)

We experimentally examined the growth, microstructure, and chemistry of shells of the bloody clam, Scapharca broughtonii (Mollusca: Bivalvia), reared at five temperatures (13, 17, 21, 25, and 29°C) with a constant pCO2 condition (∼450 μatm). In this species, the exterior side of the shell is characterized by a composite prismatic structure; on the interior side, it has a crossed lamellar structure on the interior surface. We previously found a negative correlation between temperature and the relative thickness of the composite prismatic structure in field‐collected specimens. In the reared specimens, the relationship curve between temperature and the growth increment of the composite prismatic structure was humped shaped, with a maximum at 17°C, which was compatible with the results obtained in the field‐collected specimens. In contrast, the thickness of the crossed lamellar structure was constant over the temperature range tested. These results suggest that the composite prismatic structure principally accounts for the thermal dependency of shell growth, and this inference was supported by the finding that shell growth rates were significantly correlated with the thickness of the composite prismatic structure. We also found a negative relationship between the rearing temperature and δ18O of the shell margin, in close quantitative agreement with previous reports. The findings presented here will contribute to the improved age determination of fossil and recent clams based on seasonal microstructural records

Thermal dependency of shell growth, microstructure, and stable isotopes in laboratory-reared Scapharca broughtonii (Mollusca: Bivalvia)

金沢大学国際基幹教育院 GS教育系We experimentally examined the growth, microstructure, and chemistry of shells of the bloody clam, Scapharca broughtonii (Mollusca: Bivalvia), reared at five temperatures (13, 17, 21, 25, and 29°C) with a constant pCO2 condition (∼450 μatm). In this species, the exterior side of the shell is characterized by a composite prismatic structure; on the interior side, it has a crossed lamellar structure on the interior surface. We previously found a negative correlation between temperature and the relative thickness of the composite prismatic structure in field-collected specimens. In the reared specimens, the relationship curve between temperature and the growth increment of the composite prismatic structure was humped shaped, with a maximum at 17°C, which was compatible with the results obtained in the field-collected specimens. In contrast, the thickness of the crossed lamellar structure was constant over the temperature range tested. These results suggest that the composite prismatic structure principally accounts for the thermal dependency of shell growth, and this inference was supported by the finding that shell growth rates were significantly correlated with the thickness of the composite prismatic structure. We also found a negative relationship between the rearing temperature and δ18O of the shell margin, in close quantitative agreement with previous reports. The findings presented here will contribute to the improved age determination of fossil and recent clams based on seasonal microstructural records. Key Points: Thermal plasticity of shell microstructural formation was examined Relative volume of composite prismatic structure was greatest at cooler temperature Growth rates were correlated with volume of composite prismatic structure © 2015. American Geophysical Union. All Rights Reserved

Clopidogrel Monotherapy After 1-Month Dual Antiplatelet Therapy in Percutaneous Coronary Intervention: From the STOPDAPT-2 Total Cohort

[Background:] The benefit of clopidogrel monotherapy after 1-month dual antiplatelet therapy (DAPT) compared with 12-month DAPT with aspirin and clopidogrel was demonstrated in the STOPDAPT-2 (Short and Optimal Duration of Dual Antiplatelet Therapy After Everolimus-Eluting Cobalt-Chromium Stent-2), but not in the STOPDAPT-2 acute coronary syndrome (ACS); however, both trials were underpowered based on the actual event rates. [Methods:] We obtained the prespecified pooled population of 5997 patients as the STOPDAPT-2 total cohort (STOPDAPT-2: N=3009/STOPDAPT-2 ACS: N=2988; ACS: N=4136/chronic coronary syndrome [CCS]: N=1861), comprising 2993 patients assigned to 1-month DAPT followed by clopidogrel monotherapy, and 3004 patients assigned to 12-month DAPT with aspirin and clopidogrel after percutaneous coronary intervention. The primary end point was the composite of cardiovascular (cardiovascular death, myocardial infarction, definite stent thrombosis, or any stroke) or bleeding (Thrombolysis in Myocardial Infarction major/minor) end points at 1 year. [Results:] One-month DAPT was noninferior to 12-month DAPT for the primary end point (2.84% versus 3.04%; hazard ratio [HR], 0.94 [95% CI, 0.70–1.27]; Pnoninferiority=0.001; Psuperiority=0.68). There was no significant risk-difference for the cardiovascular end point between the 1- and 12-month DAPT groups (2.40% versus 1.97%; HR, 1.24 [95% CI, 0.88–1.75]; Pnoninferiority=0.14; Psuperiority=0.23). There was a lower risk of the bleeding end point with 1-month DAPT relative to 12-month DAPT (0.50% versus 1.31%; HR, 0.38 [95% CI, 0.21–0.70]; Psuperiority=0.002). One-month DAPT relative to 12-month DAPT was associated with a lower risk for major bleeding regardless of ACS or CCS (ACS: HR, 0.46 [95% CI, 0.23–0.94]; P=0.03, and CCS: HR, 0.26 [95% CI, 0.09–0.79]; P=0.02; Pinteraction=0.40), while it was associated with a numerical increase in cardiovascular events in ACS patients, but not in CCS patients, although not statistically significant and without interaction (ACS: HR, 1.50 [95% CI, 0.99–2.27]; P=0.053, and CCS: HR, 0.74 [95% CI, 0.38–1.45]; P=0.39; Pinteraction=0.08). [Conclusions:] Clopidogrel monotherapy after 1-month DAPT compared with 12-month DAPT with aspirin and clopidogrel had a benefit in reducing major bleeding events without being associated with increase in cardiovascular events