3,280 research outputs found
Influence of turbulent mixing and air circulation in the lower atmosphere on fetch areas of selected WMO Global Atmosphere Watch baseline air pollution stations.
The World Meteorological Organisation (WMO) established the Global Atmosphere Watch (GAW) Programme in 1989. The scientific goals of GAW relate to investigating the role of atmospheric chemistry in global climate change, and include: understanding the complex mechanisms with respect to natural and anthropogenic atmospheric change; and improving the understanding of interactions between the atmosphere, ocean, and biosphere.American Meteorological Society; Stockholm Universit
Electron-Spin Excitation Coupling in an Electron Doped Copper Oxide Superconductor
High-temperature (high-Tc) superconductivity in the copper oxides arises from
electron or hole doping of their antiferromagnetic (AF) insulating parent
compounds. The evolution of the AF phase with doping and its spatial
coexistence with superconductivity are governed by the nature of charge and
spin correlations and provide clues to the mechanism of high-Tc
superconductivity. Here we use a combined neutron scattering and scanning
tunneling spectroscopy (STS) to study the Tc evolution of electron-doped
superconducting Pr0.88LaCe0.12CuO4-delta obtained through the oxygen annealing
process. We find that spin excitations detected by neutron scattering have two
distinct modes that evolve with Tc in a remarkably similar fashion to the
electron tunneling modes in STS. These results demonstrate that
antiferromagnetism and superconductivity compete locally and coexist spatially
on nanometer length scales, and the dominant electron-boson coupling at low
energies originates from the electron-spin excitations.Comment: 30 pages, 12 figures, supplementary information include
Improving the Representation of Cross-Boundary Transport of Anthropogenic Pollution in East Asia Using Radon-222.
We report on 10 years of hourly atmospheric radon, CO, and SO2 observations at Gosan Station, Korea. An improved radon detector was installed during this period and performance of the detectors is compared. A technique is developed whereby the distribution of radon concentrations from a fetch region can be used to select air masses that have consistently been in direct contact with land-based emissions, and have been least diluted en route to the measurement site. Hourly radon concentrations are used to demonstrate and characterise contamination of remote-fetch pollution observations by local emissions at this key WMO GAW site, and a seasonally-varying 5-hour diurnal sampling window is proposed for
days on which diurnal cycles are evident to minimise these effects. The seasonal variability in mixing depth and
âbackgroundâ pollutant concentrations are characterised. Based on a subset of observations most representative of the
important regional fetch areas for this site, and least affected by local emissions, seasonal estimates of CO and SO2 in air
masses originating from South China, North China, Korea and Japan are compared across the decade of observations. 2016, © Taiwan Association for Aerosol Researc
Probing Shadowed Nuclear Sea with Massive Gauge Bosons in the Future Heavy-Ion Collisions
The production of the massive bosons and could provide an
excellent tool to study cold nuclear matter effects and the modifications of
nuclear parton distribution functions (nPDFs) relative to parton distribution
functions (PDFs) of a free proton in high energy nuclear reactions at the LHC
as well as in heavy-ion collisions (HIC) with much higher center-of mass
energies available in the future colliders. In this paper we calculate the
rapidity and transverse momentum distributions of the vector boson and their
nuclear modification factors in p+Pb collisions at TeV and in
Pb+Pb collisions at TeV in the framework of perturbative QCD
by utilizing three parametrization sets of nPDFs: EPS09, DSSZ and nCTEQ. It is
found that in heavy-ion collisions at such high colliding energies, both the
rapidity distribution and the transverse momentum spectrum of vector bosons are
considerably suppressed in wide kinematic regions with respect to p+p reactions
due to large nuclear shadowing effect. We demonstrate that in the massive
vector boson productions processes with sea quarks in the initial-state may
give more contributions than those with valence quarks in the initial-state,
therefore in future heavy-ion collisions the isospin effect is less pronounced
and the charge asymmetry of W boson will be reduced significantly as compared
to that at the LHC. Large difference between results with nCTEQ and results
with EPS09 and DSSZ is observed in nuclear modifications of both rapidity and
distributions of and in the future HIC.Comment: 13 pages, 21 figures, version accepted for publication in Eur. Phys.
J.
Characterization of Fine Particulate Matter and Associations between Particulate Chemical Constituents and Mortality in Seoul, Korea
Background: Numerous studies have linked fine particles [†2.5 ”m in aerodynamic diameter (PM2.5)] and health. Most studies focused on the total mass of the particles, although the chemical composition of the particles varies substantially. Which chemical components of fine particles that are the most harmful is not well understood, and research on the chemical composition of PM2.5 and the components that are the most harmful is particularly limited in Asia
Towards Efficient Integrated Perovskite/Organic Bulk Heterojunction Solar Cells: Interfacial Energetic Requirement to Reduce Charge Carrier Recombination Losses
Integrated perovskite/organic bulk heterojunction (BHJ) solar cells have the potential to enhance the efficiency of perovskite solar cells by a simple oneâstep deposition of an organic BHJ blend photoactive layer on top of the perovskite absorber. It is found that inverted structure integrated solar cells show significantly increased shortâcircuit current (Jsc) gained from the complementary absorption of the organic BHJ layer compared to the reference perovskiteâonly devices. However, this increase in Jsc is not directly reflected as an increase in power conversion efficiency of the devices due to a loss of fill factor. Herein, the origin of this efficiency loss is investigated. It is found that a significant energetic barrier (â250 meV) exists at the perovskite/organic BHJ interface. This interfacial barrier prevents efficient transport of photogenerated charge carriers (holes) from the BHJ layer to the perovskite layer, leading to charge accumulation at the perovskite/BHJ interface. Such accumulation is found to cause undesirable recombination of charge carriers, lowering surface photovoltage of the photoactive layers and device efficiency via fill factor loss. The results highlight a critical role of the interfacial energetics in such integrated cells and provide useful guidelines for photoactive materials (both perovskite and organic semiconductors) required for highâperformance devices
Asymmetric Origin for Gravitino Relic Density in the Hybrid Gravity-Gauge Mediated Supersymmetry Breaking
We propose the hybrid gravity-gauge mediated supersymmetry breaking where the
gravitino mass is about several GeV. The strong constraints on supersymmetry
viable parameter space from the CMS and ATLAS experiments at the LHC can be
relaxed due to the heavy colored supersymmetric particles, and it is consistent
with null results in the dark matter (DM) direct search experiments such as
XENON100. In particular, the possible maximal flavor and CP violations from the
relatively small gravity mediation may naturally account for the recent LHCb
anomaly. In addition, because the gravitino mass is around the asymmetric DM
mass, we propose the asymmetric origin of the gravitino relic density and solve
the cosmological coincident problem on the DM and baryon densities \Omega_{\rm
DM}:\Omega_{B}\approx 5:1. The gravitino relic density arises from asymmetric
metastable particle (AMP) late decay. However, we show that there is no AMP
candidate in the minimal supersymmetric Standard Model (SM) due to the robust
gaugino/Higgsino mediated wash-out effects. Interestingly, AMP can be realized
in the well motivated supersymmetric SMs with vector-like particles or
continuous U(1)_R symmetry. Especially, the lightest CP-even Higgs boson mass
can be lifted in the supersymmetric SMs with vector-like particles.Comment: RevTex4, 21 pages, 1 figure, minor corrections, JHEP versio
Flavor in Minimal Conformal Technicolor
We construct a complete, realistic, and natural UV completion of minimal
conformal technicolor that explains the origin of quark and lepton masses and
mixing angles. As in "bosonic technicolor", we embed conformal technicolor in a
supersymmetric theory, with supersymmetry broken at a high scale. The exchange
of heavy scalar doublets generates higher-dimension interactions between
technifermions and quarks and leptons that give rise to quark and lepton masses
at the TeV scale. Obtaining a sufficiently large top quark mass requires strong
dynamics at the supersymmetry breaking scale in both the top and technicolor
sectors. This is natural if the theory above the supersymmetry breaking also
has strong conformal dynamics. We present two models in which the strong top
dynamics is realized in different ways. In both models, constraints from
flavor-changing effects can be easily satisfied. The effective theory below the
supersymmetry breaking scale is minimal conformal technicolor with an
additional light technicolor gaugino. We argue that this light gaugino is a
general consequence of conformal technicolor embedded into a supersymmetric
theory. If the gaugino has mass below the TeV scale it will give rise to an
additional pseudo Nambu-Goldstone boson that is observable at the LHC.Comment: 37 pages; references adde
Melody, an ENU mutation in Caspase 3, alters the catalytic cysteine residue and causes sensorineural hearing loss in mice
Progeny from the Harwell N-ethyl-N-nitrosourea (ENU) recessive mutagenesis screen were assessed for auditory defects. A pedigree was identified with multiple progeny lacking response to a clickbox test. Auditory brainstem response (ABR) analysis showed that homozygous mutant mice were profoundly deaf and the line was named melody. We subsequently mapped this mutation to a 6-Mb region on chromosome 8 and identified a point mutation in melody that results in a C163S substitution in the catalytic site of Caspase 3, a cysteine protease involved in apoptosis. Melody fails to complement a null Caspase-3 mutant. Scanning electron microscopy (SEM) has revealed disorganised sensory hair cells and hair cell loss. Histological analysis of melody has shown degeneration of spiral ganglion cells in homozygote mice, with a gradient of severity from apical to basal turns. Melody heterozygotes also show evidence of loss of spiral ganglion neurons, suggesting that the C163S mutation may show dominant negative effects by binding and sequestering proteins at the active site. The melody line provides a new model for studying the role of Caspase 3 in deafness and a number of other pathways and systems
Inclusive double-quarkonium production at the Large Hadron Collider
Based on the nonrelativistic QCD (NRQCD) factorization formalism, we
investigate inclusive productions of two spin-triplet S-wave quarkonia
pp->2J/psi+X, 2Upsilon+X, and J/psi+Upsilon+X at the CERN Large Hadron
Collider. The total production rates integrated over the rapidity (y) and
transverse-momentum (p_T) ranges |y|<2.4 and p_T<50 GGeV are predicted to be
sigma[pp->2J/psi+X] = 22 (35) nb, sigma[pp->2Upsilon+X] = 24 (49) pb, and
sigma[pp->J/psi+Upsilon+X] = 7 (13) pb at the center-of-momentum energy sqrt{s}
= 7 (14) TeV. In order to provide predictions that can be useful in both small-
and large-p_T regions, we do not employ the fragmentation approximation and we
include the spin-triplet S-wave color-singlet and color-octet channels for each
quarkonium final state at leading order in the strong coupling. The p_T
distributions of pp->2J/psi+X and 2Upsilon+X in the low-p_T region are
dominated by the color-singlet contributions. At leading order in the strong
coupling, the color-singlet channel is absent for pp->J/psi+Upsilon+X.
Therefore, the process pp->J/psi+Upsilon+X may provide a useful probe to the
color-octet mechanism of NRQCD.Comment: 26 pages, 7 figures, 3 tables, version published in JHE
- âŠ