135 research outputs found
A Reconstruction of Subtropical Western North Pacific SST Variability Back to 1578, Based on a Porites Coral Sr/Ca Record from the Northern Ryukyus, Japan
We present a seasonal reconstruction of sea surface temperature (SST) from 1578 to 2008, based on a Porites coral Sr/Ca record from the northern Ryukyus, within the Kuroshio southern recirculation gyre. Interannual SST anomalies are generally similar to 0.5 degrees C, making Sr/Ca-derived SST reconstructions a challenging task. Replicate measurements along adjacent coral growth axes, enabled by the laser ablation inductively coupled plasma mass spectrometry technique used here, give evidence of rather large uncertainties. Nonetheless, derived winter SST anomalies are significantly correlated with the Western Pacific atmospheric pattern which has a dominant influence on winter temperature in East Asia. Annual mean SSTs show interdecadal variations, notably cold intervals between 1670 and 1700 during the Maunder Minimum (MM) and between 1766 and 1788 characterized by a negative phase of the North Atlantic Oscillation. Cold summers in 1783 and 1784 coincide with the long-lasting Laki eruption that had a profound impact on the Northern Hemisphere climate, including the severe Tenmei famine in Japan. The decades between 1855 and 1900 are significantly cooler than the first half of the twentieth century, while those between 1700 and 1765, following the MM, are warmer than average. SST variability in the Ryukyus is only marginally influenced by the Pacific Decadal Oscillation, so that external forcing remains the main driver of low-frequency temperature changes. However, the close connection between the Kuroshio extension (KE) and its recirculation gyre suggests that decadal SST anomalies associated with the KE front also impact the Ryukyus, and there is a possible additional role for feedback of the Kuroshio-Oyashio variability to the large-scale atmosphere at decadal timescale.Part
of this research was supported from a
grant by JSPS KAKENHI (JP15KK0151
and JP17H01168) to Y. Y. Data used in
this paper are provided as supporting
information (Table S2)
Evidence of introgressive hybridization between the morphologically divergent land snails Ainohelix and Ezohelix
Hybridization between different taxa is likely to take place when adaptive morphological differences evolve more rapidly than reproductive isolation. When studying the phylogenetic relationship between two land snails of different nominal genera, Ainohelix editha and Ezohelix gainesi, from Hokkaido, Japan, using nuclear internal transcribed spacer and mitochondrial 16S ribosomal DNA, we found a marked incongruence in the topology between nuclear and mitochondrial phylogenies. Furthermore, no clear association was found between shell morphology (which defines the taxonomy) and nuclear or mitochondrial trees and morphology of reproductive system. These patterns are most likely explained by historical introgressive hybridization between A. editha and E. gainesi. Because the shell morphologies of the two species are quite distinct, even when they coexist, the implication is that natural selection is able to maintain (or has recreated) distinct morphologies in the face of gene flow. Future studies may be able to reveal the regions of the genome that maintain the morphological differences between these species
Operando analysis of graphite intercalation compounds with fluoride-containing polyatomic anions in aqueous solutions
The formation of graphite intercalation compounds (GICs) in aqueous solutions has attracted much attention, but reversibility in the formation/deformation of GICs is a challenging issue to construct highly safe rechargeable batteries. In this study, we used an operando analysis (X-ray diffraction and Raman spectroscopy) to discuss the feasibility of using fluoride-containing polyatomic anions in the formation of GICs in aqueous highly concentrated solutions. We found that the intercalation of anions containing a C₂F₅ moiety (such as [N(SO₂CF₃)(SO₂CF₂CF₃)]⁻ or [N(SO₂CF₂CF₃)₂]⁻) does not occur in the bulk of graphite, but only in the surface region. In addition, anions containing a CF₃ moiety show different behaviors: SO₃CF₃⁻ shows greater reversibility and larger stage-number than N(SO₂CF₃)₂⁻ in the formation of GICs. These results provide design guidelines for the reversible intercalation and de-intercalation of anions and their application as a cathode material in aqueous rechargeable batteries
Fractal Reconnection in Solar and Stellar Environments
Recent space based observations of the Sun revealed that magnetic
reconnection is ubiquitous in the solar atmosphere, ranging from small scale
reconnection (observed as nanoflares) to large scale one (observed as long
duration flares or giant arcades). Often the magnetic reconnection events are
associated with mass ejections or jets, which seem to be closely related to
multiple plasmoid ejections from fractal current sheet. The bursty radio and
hard X-ray emissions from flares also suggest the fractal reconnection and
associated particle acceleration. We shall discuss recent observations and
theories related to the plasmoid-induced-reconnection and the fractal
reconnection in solar flares, and their implication to reconnection physics and
particle acceleration. Recent findings of many superflares on solar type stars
that has extended the applicability of the fractal reconnection model of solar
flares to much a wider parameter space suitable for stellar flares are also
discussed.Comment: Invited chapter to appear in "Magnetic Reconnection: Concepts and
Applications", Springer-Verlag, W. D. Gonzalez and E. N. Parker, eds. (2016),
33 pages, 18 figure
The Japanese space gravitational wave antenna; DECIGO
DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future
Japanese space gravitational wave antenna. DECIGO is expected to open a new window of
observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing
various mysteries of the universe such as dark energy, formation mechanism of supermassive
black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of
three drag-free spacecraft, whose relative displacements are measured by a differential Fabry–
Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre-
DECIGO first and finally DECIGO in 2024
A Measurement of the Branching Fraction for the Inclusive B --> X(s) gamma Decays with the Belle Detector
We have measured the branching fraction of the inclusive radiative B meson
decay B --> X(s) gamma to be Br(B->X(s)gamma)=(3.36 +/- 0.53(stat) +/-
0.42(sys) +0.50-0.54(th)) x 10^{-4}.
The result is based on a sample of 6.07 x 10^6 BBbar events collected at the
Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric e^+e^-
storage ring.Comment: 14 pages, 6 Postsript figures, uses elsart.cl
Observation of Mixing-induced CP Violation in the Neutral B Meson System
This report describes an observation of mixing-induced CP violation and a
measurement of the CP violation parameter, sin(2phi_1), with the Belle detector
at the KEKB asymmetric e+e- collider. Using a data sample of 29.1 fb-1 recorded
on the Upsilon(4S) resonance that contains 31.3 million BBbar pairs, we
reconstruct decays of neutral B mesons to the following CP eigenstates: J/psi
K_S^0, psi(2S) K_S^0, chi_c1 K_S^0, eta_c K_S^0, J/psi K_L^0 and J/psi K^*0.
The flavor of the accompanying B meson is identified by combining information
from primary and secondary leptons, K+/- mesons, lambda baryons, slow and fast
pions. The proper-time interval between the two B meson decays is determined
from the distance between the two decay vertices measured with a silicon vertex
detector. The result sin(2phi_1) = 0.99 +/- 0.14(stat) +/- 0.06(syst) is
obtained by applying a maximum likelihood fit to the 1137 candidate events. We
conclude that there is large CP violation in the neutral B meson system. A zero
value for sin(2phi_1) is ruled out by more than six standard deviations.Comment: 25 pages, 16 figures, accepted for publication in Physical Review
Evidence of introgressive hybridization between the morphologically divergent land snails Ainohelix and Ezohelix
Hybridization between different taxa is likely to take place when adaptive morphological differences evolve more rapidly than reproductive isolation. When studying the phylogenetic relationship between two land snails of different nominal genera, Ainohelix editha and Ezohelix gainesi, from Hokkaido, Japan, using nuclear internal transcribed spacer and mitochondrial 16S ribosomal DNA, we found a marked incongruence in the topology between nuclear and mitochondrial phylogenies. Furthermore, no clear association was found between shell morphology (which defines the taxonomy) and nuclear or mitochondrial trees and morphology of reproductive system. These patterns are most likely explained by historical introgressive hybridization between A. editha and E. gainesi. Because the shell morphologies of the two species are quite distinct, even when they coexist, the implication is that natural selection is able to maintain (or has recreated) distinct morphologies in the face of gene flow. Future studies may be able to reveal the regions of the genome that maintain the morphological differences between these species
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