1,378 research outputs found
Penta-quark states with hidden charm and beauty
More and more hadron states are found to be difficult to be accommodated by
the quenched quark models which describe baryons as 3-quark states and mesons
as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon
field in hadrons should be an important excitation mechanism for hadron
spectroscopy. Our recent progress on the penta-quark states with hidden charm
and beauty is reviewed.Comment: Plenary talk at the 5th Asia-Pacific Conference on Few-Body Problems
in Physics 2011 (APFB2011), 22-26 Aug., 2011, Seoul, Kore
The rare top quark decays in the topcolor-assisted technicolor model
We consider the rare top quark decays in the framework of topcolor-assisted
technicolor (TC2) model. We find that the contributions of top-pions and
top-Higgs predicted by the TC2 model can enhance the SM branching ratios by as
much as 6-9 orders of magnitude. i.e., in the most case, the orders of
magnitude of branching ratios are , , . With the reasonable values of the
parameters in TC2 model, such rare top quark decays may be testable in the
future experiments. So, rare top quark decays provide us a unique way to test
TC2 model.Comment: 14 pages, 4 figure
Variability of organic and elemental carbon, water soluble organic carbon, and isotopes in Hong Kong
International audienceTo determine the levels and variations of carbonaceous aerosol in Hong Kong, PM2.5 and PM10 samples were collected by high volume (Hi-vol) samplers at three monitoring stations (representing middle-scale roadside, urban-, and regional-scale environments) during winter (November 2000 to February 2001) and summer (June 2001 to August 2001) periods. The highest concentrations of organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were found at the middle-scale roadside site with the lowest at the regional-scale site. The percentages of WSOC in total carbon at these sites were inversely correlated with their concentrations (i.e., the highest percentages of WSOC were observed at the regional-scale site). A high WSOC fraction may be associated with aged aerosol because of the secondary formation by photochemical oxidation of organic precursors of anthropogenic pollutants during transport. The annual average of isotope abundances (?13C) of OC and EC were ?26.9±0.5? and ?25.6±0.1?, respectively. There were no notable differences for seasonal distributions of carbon isotopic composition, consistent with motor vehicle emissions being the main source contributors of carbonaceous aerosol in Hong Kong. OC 13C abundances at the regional-scale site were higher than those at the middle-scale roadside and urban sites, consistent with secondary organic aerosols of biogenic origin
Multi-objective 3D topology optimization of next generation wireless data center network
As one of the next generation network technologies for data centers, wireless data center network has important research significance. Smart architecture optimization and management are very important for wireless data center network. With the ever-increasing demand of data center resources, there are more and more data servers deployed. However, traditional wired links among servers are expensive and inflexible. Benefited from the development of intelligent optimization and other techniques, high speed wireless topology for wireless data center network is studied. Through image processing, a radio propagation model is constructed based on a heat map. The line-of-sight issue and the interference problem are also discussed. By simultaneously considering objectives of coverage, propagation intensity and interference intensity as well as the constraint of connectivity, we formulate the topology optimization problem as a multi-objective optimization problem. To seek for solutions, we employ several state-of-the-art serial MOEAs as well as three parallel MOEAs. For the
grouping in distributed parallel algorithms, prior knowledge
is referred. Finally, experimental results demonstrate that,
the parallel MOEAs perform effectively in optimization results and efficiently in time consumption
Measurements of (p,pi ̄) Reactions Near Zero Degrees
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
The role of occupied d states in the relaxation of hot electrons in Au
We present first-principles calculations of electron-electron scattering
rates of low-energy electrons in Au. Our full band-structure calculations
indicate that a major contribution from occupied d states participating in the
screening of electron-electron interactions yields lifetimes of electrons in Au
with energies of above the Fermi level that are larger than
those of electrons in a free-electron gas by a factor of . This
prediction is in agreement with a recent experimental study of ultrafast
electron dynamics in Au(111) films (J. Cao {\it et al}, Phys. Rev. B {\bf 58},
10948 (1998)), where electron transport has been shown to play a minor role in
the measured lifetimes of hot electrons in this material.Comment: 4 pages, 2 figures, to appear in Phys. Rev.
OL-085 A candidate genes study for the association of host single nucleotide polymorphisms with liver cirrhosis risk in Chinese hepatitis B patients
Structure Formation, Melting, and the Optical Properties of Gold/DNA Nanocomposites: Effects of Relaxation Time
We present a model for structure formation, melting, and optical properties
of gold/DNA nanocomposites. These composites consist of a collection of gold
nanoparticles (of radius 50 nm or less) which are bound together by links made
up of DNA strands. In our structural model, the nanocomposite forms from a
series of Monte Carlo steps, each involving reaction-limited cluster-cluster
aggregation (RLCA) followed by dehybridization of the DNA links. These links
form with a probability which depends on temperature and particle
radius . The final structure depends on the number of monomers (i. e. gold
nanoparticles) , , and the relaxation time. At low temperature, the
model results in an RLCA cluster. But after a long enough relaxation time, the
nanocomposite reduces to a compact, non-fractal cluster. We calculate the
optical properties of the resulting aggregates using the Discrete Dipole
Approximation. Despite the restructuring, the melting transition (as seen in
the extinction coefficient at wavelength 520 nm) remains sharp, and the melting
temperature increases with increasing as found in our previous
percolation model. However, restructuring increases the corresponding link
fraction at melting to a value well above the percolation threshold. Our
calculated extinction cross section agrees qualitatively with experiments on
gold/DNA composites. It also shows a characteristic ``rebound effect,''
resulting from incomplete relaxation, which has also been seen in some
experiments. We discuss briefly how our results relate to a possible sol-gel
transition in these aggregates.Comment: 12 pages, 10 figure
Familial transmissability of early age at initial diagnosis in coronary heart disease (CHD):males only, and mediated by psychosocial/emotional distress?
The effect of the annealing temperature on the local distortion of LaCaMnO thin films
Mn -edge fluorescence data are presented for thin film samples (3000~\AA)
of Colossal Magnetoresistive (CMR) LaCaMnO: as-deposited,
and post-annealed at 1000 K and 1200 K. The local distortion is analyzed in
terms of three contributions: static, phonon, and an extra,
temperature-dependent, polaron term. The polaron distortion is very small for
the as-deposited sample and increases with the annealing temperature. In
contrast, the static distortion in the samples decreases with the annealing
temperature. Although the local structure of the as-deposited sample shows very
little temperature dependence, the change in resistivity with temperature is
the largest of these three thin film samples. The as-deposited sample also has
the highest magnetoresistance (MR), which indicates some other mechanism may
also contribute to the transport properties of CMR samples. We also discuss the
relationship between local distortion and the magnetization of the sample.Comment: 11 pages of Preprint format, 8 figures in one tar fil
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