635 research outputs found
Southern Ocean Control of 2°C Global Warming in Climate Models
Global warming will soon reach the Paris Agreement targets of 1.5°C/2°C temperature increase above pre-industrial levels. Under a business-as-usual scenario, the time to reach these targets varies widely among climate models. Using Coupled Model Intercomparison Project Phase 5 and 6, we show that a 2°C global warming is determined by Southern Ocean (SO) state closely tied with a low-level cloud (LLC) amount feedback strength during reference (1861â1900) period; climate models with cold SO tend to accompany more low-level cloudiness and Antarctic sea ice concentration due to a strong LLC amount feedback. Consequently, initially cold SO models tend to simulate a fast global warming by absorbing more downward shortwave radiation compared to initially warm SO models because more LLC disappears due to a strong LLC amount feedback during the 2°C rise. Our results demonstrate that climate models that correctly simulate initial SO state can improve 2°C warming projections with reduced uncertainties.publishedVersio
Photoemission and x-ray absorption study of MgC_(1-x)Ni_3
We investigated electronic structure of MgC_(1-x)Ni_3 with photoemission and
x-ray absorption spectroscopy. Both results show that overall band structure is
in reasonable agreement with band structure calculations including the
existence of von Hove singularity (vHs)near E_F. However, we find that the
sharp vHs peak theoretically predicted near the E_F is substantially
suppressed. As for the Ni core level and absorption spectrum, there exist the
satellites of Ni 2p which have a little larger energy separation and reduced
intensity compared to the case of Ni-metal. These facts indicate that
correlation effects among Ni 3d electrons may be important to understand
various physical properties.Comment: 12 pages, 4 figure
Further investigations of linear trirhodium complexes: experimental and theoretical studies of Rh-3(dpa)(4)Cl-2 and Rh-3(dpa)(4)Cl-2 (BF4) dpa = bis(2-pyridyl)amido anion
The linear trirhodium compound, Rh-3(dpa)(4)Cl-2 (1), and its one-electron oxidation product, [Rh-3(dpa)(4)Cl-2]BF4 (2), have been synthesized and studied extensively. The magnetic measurement for compound 1 shows that it possesses one unpaired electron that is assigned to occupy the sigma(nb) orbital ((2)A(2)) by DFT calculations. Upon oxidation, a beta-spin electron of 1 is removed, that causes compound 2 to exhibit a triplet ground state. DFT calculations indicate that the two unpaired electrons of 2 occupy sigma(nb) and delta* orbitals (B-3(1)), which is supported by H-1 NMR spectrum. Unlike their isoelectronic analogues [Co-3(dpa)(4)Cl-2] (3) and [Co-3(dpa)(4)(Cl)(2)]BF4 (4), both compound 1 and 2 do not display the spin-crossover phenomenon. The reason may be attributed to the relative large energy gap between B-3(1) and open-shell singlet B-1(1) states
Resonance peak in underdoped cuprates
The magnetic susceptibility measured in neutron scattering experiments in
underdoped YBaCuO is interpreted based on the self-consistent
solution of the t-J model of a Cu-O plane. The calculations reproduce correctly
the frequency and momentum dependencies of the susceptibility and its variation
with doping and temperature in the normal and superconducting states. This
allows us to interpret the maximum in the frequency dependence -- the resonance
peak -- as a manifestation of the excitation branch of localized Cu spins and
to relate the frequency of the maximum to the size of the spin gap. The
low-frequency shoulder well resolved in the susceptibility of superconducting
crystals is connected with a pronounced maximum in the damping of the spin
excitations. This maximum is caused by intense quasiparticle peaks in the hole
spectral function for momenta near the Fermi surface and by the nesting.Comment: 9 pages, 6 figure
Physical properties of FeSeTe single crystals grown under different conditions
We report on structural, magnetic, conductivity, and thermodynamic studies of
FeSeTe single crystals grown by self-flux and Bridgman methods.
The samples were prepared from starting materials of different purity at
various temperatures and cooling rates. The lowest values of the susceptibility
in the normal state, the highest transition temperature of 14.5 K, and
the largest heat-capacity anomaly at were obtained for pure (oxygen-free)
samples. The critical current density of A/cm (at 2
K) achieved in pure samples is attributed to intrinsic inhomogeneity due to
disorder at the cation and anion sites. The impure samples show increased
up to A/cm due to additional pinning centers of
FeO. The upper critical field of kOe is estimated
from the resistivity study in magnetic fields parallel to the \emph{c}-axis.
The anisotropy of the upper critical field reaches a value at . Extremely low values of the residual Sommerfeld coefficient for pure
samples indicate a high volume fraction of the superconducting phase (up to
97%). The electronic contribution to the specific heat in the superconducting
state is well described within a single-band BCS model with a temperature
dependent gap K. A broad cusp-like anomaly in the electronic
specific heat of samples with suppressed bulk superconductivity is ascribed to
a splitting of the ground state of the interstitial Fe ions. This
contribution is fully suppressed in the ordered state in samples with bulk
superconductivity.Comment: 11 pages, 11 figures, 3 table
Manipulation of electronic structure via supporting ligands: a charge disproportionate model within the linear metal framework of asymmetric nickel string Ni-7(phdptrany)(4)Cl (PF6)
This paper describes the synthesis and physical properties of an uniquely asymmetric heptanickel string complex exhibiting a charge disproportionate model along the linear nickel framework
A CsI(Tl) Scintillating Crystal Detector for the Studies of Low Energy Neutrino Interactions
Scintillating crystal detector may offer some potential advantages in the
low-energy, low-background experiments. A 500 kg CsI(Tl) detector to be placed
near the core of Nuclear Power Station II in Taiwan is being constructed for
the studies of electron-neutrino scatterings and other keV-MeV range neutrino
interactions. The motivations of this detector approach, the physics to be
addressed, the basic experimental design, and the characteristic performance of
prototype modules are described. The expected background channels and their
experimental handles are discussed.Comment: 34 pages, 11 figures, submitted to Nucl. Instrum. Method
Evolutionary aspects of population structure for molecular and quantitative traits in the freshwater snail Radix balthica.
Detecting the action of selection in natural populations can be achieved using the QST-FST comparison that relies on the estimation of FST with neutral markers, and QST using quantitative traits potentially under selection. QST higher than FST suggests the action of directional selection and thus potential local adaptation. In this article, we apply the QST-FST comparison to four populations of the hermaphroditic freshwater snail Radix balthica located in a floodplain habitat. In contrast to most studies published so far, we did not detect evidence of directional selection for local optima for any of the traits we measured: QST calculated using three different methods was never higher than FST. A strong inbreeding depression was also detected, indicating that outcrossing is probably predominant over selfing in the studied populations. Our results suggest that in this floodplain habitat, local adaptation of R. balthica populations may be hindered by genetic drift, and possibly altered by uneven gene flow linked to flood frequency
Measurement of W Polarisation at LEP
The three different helicity states of W bosons produced in the reaction e+
e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W
decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to
measure the polarisation of W bosons, and its dependence on the W boson
production angle. The fraction of longitudinally polarised W bosons is measured
to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and
the second systematic, in agreement with the Standard Model expectation
Search for Anomalous Couplings in the Higgs Sector at LEP
Anomalous couplings of the Higgs boson are searched for through the processes
e^+ e^- -> H gamma, e^+ e^- -> e^+ e^- H and e^+ e^- -> HZ. The mass range 70
GeV < m_H < 190 GeV is explored using 602 pb^-1 of integrated luminosity
collected with the L3 detector at LEP at centre-of-mass energies
sqrt(s)=189-209 GeV. The Higgs decay channels H -> ffbar, H -> gamma gamma, H
-> Z\gamma and H -> WW^(*) are considered and no evidence is found for
anomalous Higgs production or decay. Limits on the anomalous couplings d, db,
Delta(g1z), Delta(kappa_gamma) and xi^2 are derived as well as limits on the H
-> gamma gamma and H -> Z gamma decay rates
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