310 research outputs found
Impacts of the East Asian monsoon on lower tropospheric ozone over coastal South China
The impact of the East Asian monsoon (EAM) on climatology and interannual variability of
tropospheric ozone (O3) over the coastal South China was investigated by analyzing 11 years
of ozonesonde data over Hong Kong with the aid of Lagrangian dispersion modeling of carbon
monoxide and calculation of an EAM index. It was found that the seasonal cycle of O3 in the
lower troposphere is highly related to the EAM over the study region. Ozone enhancements in
the free troposphere are associated with the monsoon-induced transport of pollutants of
continental anthropogenic and biomass burning origins. Lower tropospheric O3 levels showed
high interannual variability, with an annual averaged amplitude up to 61% of averaged
concentrations in the boundary layer (0â1 km altitudes) and 49% below 3 km altitude. In
spring and autumn, the interannual variability in boundary layer O3 levels was predominately
influenced by the EAM intensity, with high O3 mixing ratios associated with northeasterly
circulation anomalies
Optical properties and radiative forcing of urban aerosols in Nanjing, China
AbstractContinuous measurements of atmospheric aerosols were made in Nanjing, a megacity in China, from 18 January to 18 April, 2011 (Phase 1) and from 22 April 2011 to 21 April 2012 (Phase 2). Aerosol characteristics, optical properties, and direct radiative forcing (DRF) were studied through interpretations of these measurements. We found that during Phase 1, mean PM2.5, black carbon (BC), and aerosol scattering coefficient (Bsp) in Nanjing were 76.1 ± 59.3 Όg mâ3, 4.1 ± 2.2 Όg mâ3, and 170.9 ± 105.8 M mâ1, respectively. High pollution episodes occurred during Spring and Lantern Festivals when hourly PM2.5 concentrations reached 440 Όg mâ3, possibly due to significant discharge of fireworks. Temporal variations of PM2.5, BC, and Bsp were similar to each other. It is estimated that inorganic scattering aerosols account for about 49 ± 8.6% of total aerosols while BC only accounted for 6.6 ± 2.9%, and nitrate was larger than sulfate. In Phase 2, optical properties of aerosols show great seasonality. High relative humidity (RH) in summer (June, July, August) likely attributed to large optical depth (AOD) and small Angstrom exponent (AE) of aerosols. Due to dust storms, AE of total aerosols was the smallest in spring (March, April, May). Annual mean 550-nm AOD and 675/440-nm AE were 0.6 ± 0.3 and 1.25 ± 0.29 for total aerosols, 0.04 ± 0.02 and 1.44 ± 0.50 for absorbing aerosols, 0.48 ± 0.29 and 1.64 ± 0.29 for fine aerosols, respectively. Annual single scattering albedo of aerosols ranged from 0.90 to 0.92. Real time wavelength-dependent surface albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to assess aerosol DRFs. Both total and absorbing aerosol DRFs had significant seasonal variations in Nanjing and they were the strongest in summer. Annual mean clear sky TOA DRF (including daytime and nighttime) of total and absorbing aerosols was about â6.9 and +4.5 W mâ2, respectively. Aerosol DRFs were found to be sensitive to surface albedo. Over brighter surfaces, solar radiation was more absorbed by absorbing aerosols and less scattered by scattering aerosols
Prospects of Scintillating Crystal Detector in Low-Energy Low-Background Experiments
Scintillating crystal detector offers potential advantages in low-energy
(keV-MeV range) low-background experiments for particle physics and
astrophysics. The merits are discussed using CsI(Tl) crystal as illustrations.
The various physics topics which can be pursued with this detector technology
are summarized. A conceptual design for a generic detector is presented.Comment: 20 pages, 1 tables, 7 figures, submitted to Astroparticle Physic
Alpha-decay branching ratios of near-threshold states in 19Ne and the astrophysical rate of 15O(alpha,gamma)19Ne
The 15O(alpha,gamma)19Ne reaction is one of two routes for breakout from the
hot CNO cycles into the rp process in accreting neutron stars. Its
astrophysical rate depends critically on the decay properties of excited states
in 19Ne lying just above the 15O + alpha threshold. We have measured the
alpha-decay branching ratios for these states using the p(21Ne,t)19Ne reaction
at 43 MeV/u. Combining our measurements with previous determinations of the
radiative widths of these states, we conclude that no significant breakout from
the hot CNO cycle into the rp process in novae is possible via
15O(alpha,gamma)19Ne, assuming current models accurately represent their
temperature and density conditions
On the Bohr inequality
The Bohr inequality, first introduced by Harald Bohr in 1914, deals with
finding the largest radius , , such that holds whenever in the unit disk
of the complex plane. The exact value of this largest radius,
known as the \emph{Bohr radius}, has been established to be This paper
surveys recent advances and generalizations on the Bohr inequality. It
discusses the Bohr radius for certain power series in as well as
for analytic functions from into particular domains. These domains
include the punctured unit disk, the exterior of the closed unit disk, and
concave wedge-domains. The analogous Bohr radius is also studied for harmonic
and starlike logharmonic mappings in The Bohr phenomenon which is
described in terms of the Euclidean distance is further investigated using the
spherical chordal metric and the hyperbolic metric. The exposition concludes
with a discussion on the -dimensional Bohr radius
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
Microlensing as a probe of the Galactic structure; 20 years of microlensing optical depth studies
Microlensing is now a very popular observational astronomical technique. The
investigations accessible through this effect range from the dark matter
problem to the search for extra-solar planets. In this review, the techniques
to search for microlensing effects and to determine optical depths through the
monitoring of large samples of stars will be described. The consequences of the
published results on the knowledge of the Milky-Way structure and its dark
matter component will be discussed. The difficulties and limitations of the
ongoing programs and the perspectives of the microlensing optical depth
technique as a probe of the Galaxy structure will also be detailed.Comment: Accepted for publication in General Relativity and Gravitation.
General Relativity and Gravitation in press (2010) 0
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
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