753 research outputs found
Clustering properties of a generalised critical Euclidean network
Many real-world networks exhibit scale-free feature, have a small diameter
and a high clustering tendency. We have studied the properties of a growing
network, which has all these features, in which an incoming node is connected
to its th predecessor of degree with a link of length using a
probability proportional to . For , the
network is scale free at with the degree distribution and as in the Barab\'asi-Albert model (). We find a phase boundary in the plane along which
the network is scale-free. Interestingly, we find scale-free behaviour even for
for where the existence of a new universality class
is indicated from the behaviour of the degree distribution and the clustering
coefficients. The network has a small diameter in the entire scale-free region.
The clustering coefficients emulate the behaviour of most real networks for
increasing negative values of on the phase boundary.Comment: 4 pages REVTEX, 4 figure
Self Consistent Expansion for the Molecular Beam Epitaxy Equation
Motivated by a controversy over the correct results derived from the dynamic
renormalization group (DRG) analysis of the non linear molecular beam epitaxy
(MBE) equation, a self-consistent expansion (SCE) for the non linear MBE theory
is considered. The scaling exponents are obtained for spatially correlated
noise of the general form . I find a lower critical dimension , above, which the linear MBE solution appears. Below the
lower critical dimension a r-dependent strong-coupling solution is found. These
results help to resolve the controversy over the correct exponents that
describe non linear MBE, using a reliable method that proved itself in the past
by predicting reasonable results for the Kardar-Parisi-Zhang (KPZ) system,
where DRG failed to do so.Comment: 16 page
Self-similar disk packings as model spatial scale-free networks
The network of contacts in space-filling disk packings, such as the
Apollonian packing, are examined. These networks provide an interesting example
of spatial scale-free networks, where the topology reflects the broad
distribution of disk areas. A wide variety of topological and spatial
properties of these systems are characterized. Their potential as models for
networks of connected minima on energy landscapes is discussed.Comment: 13 pages, 12 figures; some bugs fixed and further discussion of
higher-dimensional packing
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A Study on the Tritium Behavior in the Rice Plant after a Short-Term Exposure of HTO
In many Asian countries including Korea, rice is a very important food crop. Its grain is consumed by humans and its straw is used to feed animals. In Korea, there are four CANDU type reactors that release relatively large amounts of tritium into the environment. Since 1997, KAERI (Korea Atomic Energy Research Institute) has carried out the experimental studies to obtain domestic data on various parameters concerning the direct contamination of plant. In this study, the behavior of tritium in the rice plant is predicted and compared with the measurement performed at KAERI. Using the conceptual model of the soil-plant-atmosphere tritiated water transport system which was suggested by Charles E. Murphy, tritium concentrations in the soil and in leaves to time were derived. If the effect of tritium concentration in the soil is considered, the tritium concentration in leaves is described as a double exponential model. On the other hand if the tritium concentration in the soil is disregarded, the tritium concentration in leaves is described by a single exponential term as other models (e.g. Belot's or STAR-H3 model). Also concentration of organically bound tritium in the seed is predicted and compared with measurements. The results can be used to predict the tritium concentration in the rice plant at a field around the site and the ingestion dose following the release of tritium to the environment
Quasistatic Scale-free Networks
A network is formed using the sites of an one-dimensional lattice in the
shape of a ring as nodes and each node with the initial degree .
links are then introduced to this network, each link starts from a distinct
node, the other end being connected to any other node with degree randomly
selected with an attachment probability proportional to . Tuning
the control parameter we observe a transition where the average degree
of the largest node changes its variation from to
at a specific transition point of . The network is scale-free i.e.,
the nodal degree distribution has a power law decay for .Comment: 4 pages, 5 figure
An air-stable DPP-thieno-TTF copolymer for single-material solar cell devices and field effect transistors
Following an approach developed in our group to incorporate tetrathiafulvalene (TTF) units into conjugated polymeric systems, we have studied a low band gap polymer incorporating TTF as a donor component. This polymer is based on a fused thieno-TTF unit that enables the direct incorporation of the TTF unit into the polymer, and a second comonomer based on the diketopyrrolopyrrole (DPP) molecule. These units represent a donor–acceptor copolymer system, p(DPP-TTF), showing strong absorption in the UV–visible region of the spectrum. An optimized p(DPP-TTF) polymer organic field effect transistor and a single material organic solar cell device showed excellent performance with a hole mobility of up to 5.3 × 10–2 cm2/(V s) and a power conversion efficiency (PCE) of 0.3%, respectively. Bulk heterojunction organic photovoltaic devices of p(DPP-TTF) blended with phenyl-C71-butyric acid methyl ester (PC71BM) exhibited a PCE of 1.8%
Search for a dark vector gauge boson decaying to using decays
We report a search for a dark vector gauge boson that couples to
quarks in the decay chain , . No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of in the mass range of 290 to 520 MeV/. This analysis is
based on a data sample of 976 fb collected by the Belle experiment at
the KEKB asymmetric-energy collider.Comment: 6 pages, 4 figure
Studies of charmed strange baryons in the final state at Belle
We report the discovery of , observed by its decay into
the final state , and present the first observation and evidence
of the decays of and into .
We also perform a combined analysis of the with the
and decay modes to measure
the ratios of branching fractions, masses and widths with improved accuracy. We
measure the ratios of branching fractions , , and , where the uncertainties are
statistical and systematic. The analysis is performed using a 980 fb
data sample collected with the Belle detector at the KEKB asymmetric-energy
collider.Comment: Submitted to PR
Search for decays to invisible final states at Belle
We report the result from the first search for decays to invisible
final states. The analysis is performed on a data sample of 924
collected at and near the and resonances with the
Belle detector at the KEKB asymmetric-energy collider. The
absolute branching fraction is determined using an inclusive sample,
obtained by fully reconstructing the rest of the particle system including the
other charmed particle. No significant signal yield is observed and an upper
limit of is set on the branching fraction of to
invisible final states at 90\% confidence level.Comment: 17 pages, 4 figures, submitted to PRD(RC
Measurement of via initial state radiation at Belle
The process (=1, 2) is studied via initial
state radiation using 980 fb of data at and around the
(=1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB
asymmetric-energy collider. No significant signal is observed except
from decays. Upper limits on the cross sections between
and are determined at the 90% credibility
level, which range from few pb to a few tens of pb. We also set upper limits on
the decay rate of the vector charmonium [), , and
] and charmoniumlike [, , and ] states
to .Comment: Accepted by PR
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