11,005 research outputs found
Metallic characteristics in superlattices composed of insulators, NdMnO3/SrMnO3/LaMnO3
We report on the electronic properties of superlattices composed of three
different antiferromagnetic insulators, NdMnO3/SrMnO3/LaMnO3 grown on SrTiO3
substrates. Photoemission spectra obtained by tuning the x-ray energy at the Mn
2p -> 3d edge show a Fermi cut-off, indicating metallic behavior mainly
originating from Mn e_g electrons. Furthermore, the density of states near the
Fermi energy and the magnetization obey a similar temperature dependence,
suggesting a correlation between the spin and charge degrees of freedom at the
interfaces of these oxides
Pressure effects on the heavy-fermion antiferromagnet CeAuSb2
The f-electron compound CeAuSb2, which crystallizes in the ZrCuSi2-type
tetragonal structure, orders antiferromagnetically between 5 and 6.8 K, where
the antiferromagnetic transition temperature T_N depends on the occupancy of
the Au site. Here we report the electrical resistivity and heat capacity of a
high-quality crystal CeAuSb2 with T_N of 6.8 K, the highest for this compound.
The magnetic transition temperature is initially suppressed with pressure, but
is intercepted by a new magnetic state above 2.1 GPa. The new phase shows a
dome shape with pressure and coexists with another phase at pressures higher
than 4.7 GPa. The electrical resistivity shows a T^2 Fermi liquids behavior in
the complex magnetic state, and the residual resistivity and the T^2
resistivity coefficient increases with pressure, suggesting the possibility of
a magnetic quantum critical point at a higher pressure.Comment: 5 pages, 5 firure
Extensive spatiotemporal analyses of surface ozone and related meteorological variables in South Korea for the period 1999–2010
Spatiotemporal characteristics of surface ozone (O<sub>3</sub>) variations over
South Korea are investigated with consideration of meteorological factors
and timescales based on the Kolmogorov–Zurbenko filter (KZ filter), using
measurement data at 124 air quality monitoring sites and 72 weather stations
for the 12 yr period of 1999–2010. In general, O<sub>3</sub> levels at coastal
cities are high due to dynamic effects of the sea breeze while those at the
inland and Seoul Metropolitan Area (SMA) cities are low due to the NO<sub>x</sub>
titration by local precursor emissions. We examine the meteorological
influences on O<sub>3</sub> using a combined analysis of the KZ filter and linear
regressions between O<sub>3</sub> and meteorological variables. We decomposed
O<sub>3</sub> time series at each site into short-term, seasonal, and long-term
components by the KZ filter and regressed on meteorological variables.
Impact of temperature on the O<sub>3</sub> levels is significantly high in the
highly populated SMA and inland region, but low in the coastal region. In
particular, the probability of high O<sub>3</sub> occurrence doubles with
4 °C of temperature increase in the SMA during high O<sub>3</sub> months
(May–October). This implies that those regions will experience frequent
high O<sub>3</sub> events in a future warming climate. In terms of short-term
variation, the distribution of high O<sub>3</sub> probability classified by wind
direction shows the effect of both local precursor emissions and long-range
transport from China. In terms of long-term variation, the O<sub>3</sub>
concentrations have increased by +0.26 ppbv yr<sup>−1</sup> (parts per billion by volume) on nationwide
average, but their trends show large spatial variability. Singular value
decomposition analyses further reveal that the long-term temporal evolution
of O<sub>3</sub> is similar to that of nitrogen dioxide, although the spatial
distribution of their trends is different. This study will be helpful as a
reference for diagnostics and evaluation of regional- and local-scale
O<sub>3</sub> and climate simulations, and as a guide to appropriate O<sub>3</sub>
control policy in South Korea
Non-monotonic temperature dependent transport in graphene grown by Chemical Vapor Deposition
Temperature-dependent resistivity of graphene grown by chemical vapor
deposition (CVD) is investigated. We observe in low mobility CVD graphene
device a strong insulating behavior at low temperatures and a metallic behavior
at high temperatures manifesting a non-monotonic in the temperature dependent
resistivity.This feature is strongly affected by carrier density modulation. To
understand this anomalous temperature dependence, we introduce thermal
activation of charge carriers in electron-hole puddles induced by randomly
distributed charged impurities. Observed temperature evolution of resistivity
is then understood from the competition among thermal activation of charge
carriers, temperature-dependent screening and phonon scattering effects. Our
results imply that the transport property of transferred CVD-grown graphene is
strongly influenced by the details of the environmentComment: 7 pages, 3 figure
P01.20. The effect of WIN-34B on cartilage protection and regeneration by chondrogenesis from subchondral bone in vitro and in vivo
Effects of pressure on the ferromagnetic state of the CDW compound SmNiC2
We report the pressure response of charge-density-wave (CDW) and
ferromagnetic (FM) phases of the rare-earth intermetallic SmNiC2 up to 5.5 GPa.
The CDW transition temperature (T_{CDW}), which is reflected as a sharp
inflection in the electrical resistivity, is almost independent of pressure up
to 2.18 GPa but is strongly enhanced at higher pressures, increasing from 155.7
K at 2.2 GPa to 279.3 K at 5.5 GPa. Commensurate with the sharp increase in
T_{CDW}, the first-order FM phase transition, which decreases with applied
pressure, bifurcates into the upper (T_{M1}) and lower (T_c) phase transitions
and the lower transition changes its nature to second order above 2.18 GPa.
Enhancement both in the residual resistivity and the Fermi-liquid T^2
coefficient A near 3.8 GPa suggests abundant magnetic quantum fluctuations that
arise from the possible presence of a FM quantum critical point.Comment: 5 pages, 5 figure
The Dropping of In-Medium Hadron Mass in Holographic QCD
We study the baryon density dependence of the vector meson spectrum using the
D4/D6 system together with the compact D4 baryon vertex. We find that the
vector meson mass decreases almost linearly in density at low density for small
quark mass, but saturates to a finite non-zero value for large density. We also
compute the density dependence of the mass and the
velocity. We find that in medium, our model is consistent with the GMOR
relation up to a few times the normal nuclear density. We compare our hQCD
predictions with predictions made based on hidden local gauge theory that is
constructed to model QCD.Comment: 20 pages, 7 figure
Formation, Manipulation, and Elasticity Measurement of a Nanometric Column of Water Molecules
Nanometer-sized columns of condensed water molecules are created by an
atomic-resolution force microscope operated in ambient conditions. Unusual
stepwise decrease of the force gradient associated with the thin water bridge
in the tip-substrate gap is observed during its stretch, exhibiting regularity
in step heights (~0.5 N/m) and plateau lengths (~1 nm). Such "quantized"
elasticity is indicative of the atomic-scale stick-slip at the tip-water
interface. A thermodynamic-instability-induced rupture of the water meniscus
(5-nm long and 2.6-nm wide) is also found. This work opens a high-resolution
study of the structure and the interface dynamics of a nanometric aqueous
column.Comment: 4 pages, 3 figure
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