2,398 research outputs found
Scaling in the distribution of intertrade durations of Chinese stocks
The distribution of intertrade durations, defined as the waiting times
between two consecutive transactions, is investigated based upon the limit
order book data of 23 liquid Chinese stocks listed on the Shenzhen Stock
Exchange in the whole year 2003. A scaling pattern is observed in the
distributions of intertrade durations, where the empirical density functions of
the normalized intertrade durations of all 23 stocks collapse onto a single
curve. The scaling pattern is also observed in the intertrade duration
distributions for filled and partially filled trades and in the conditional
distributions. The ensemble distributions for all stocks are modeled by the
Weibull and the Tsallis -exponential distributions. Maximum likelihood
estimation shows that the Weibull distribution outperforms the -exponential
for not-too-large intertrade durations which account for more than 98.5% of the
data. Alternatively, nonlinear least-squares estimation selects the
-exponential as a better model, in which the optimization is conducted on
the distance between empirical and theoretical values of the logarithmic
probability densities. The distribution of intertrade durations is Weibull
followed by a power-law tail with an asymptotic tail exponent close to 3.Comment: 16 elsart pages including 3 eps figure
Poly[μ2-aqua-[μ2-1,1′-(butane-1,4-diyl)diimidazole]bis(μ4-naphthalene-1,4-dicarboxylato)dimanganese(II)]
In the title compound, [Mn2(C12H6O4)2(C10H14N4)(H2O)]n or [Mn2(1,4-ndc)2(L)(H2O)]n, where 1,4-ndc is naphthalene-1,4-dicarboxylate and L is 1,1′-(butane-1,4-diyl)diimidazole, the coordination polyhedron around each MnII atom is distorted octahedral. The water molecule and the L ligand are situated across a twofold rotation axis. The MnII atoms are bridged by 1,4-ndc and L ligands, forming a three-dimensional network. O—H⋯O hydrogen bonds are observed within the network
Poly[μ-aqua-[μ-1,1′-(butane-1,4-diyl)diimidazole]bis(μ4-naphthalene-1,4-dicarboxylato)dicadmium(II)]
In the title compound, [Cd2(C12H6O4)2(C10H14N4)(H2O)]n, the coordination polyhedron around each CdII ion is a distorted CdNO5 octahedron. The water O atom has site symmetry 2 and the complete 1,1′-(butane-1,4-diyl)diimidazole (L) ligand is generated by inversion. The naphthalene-1,4-dicarboxylate and L ligands bridge the metal centres, forming a three-dimensional framework, which is consolidated by O—H⋯O hydrogen bonds
A search for 95 GHz class I methanol masers in molecular outflows
We have observed a sample of 288 molecular outflow sources including 123
high-mass and 165 low-mass sources to search for class I methanol masers at 95
GHz transition and to investigate relationship between outflow characteristics
and class I methanol maser emission with the PMO-13.7m radio telescope. Our
survey detected 62 sources with 95 GHz methanol masers above 3
detection limit, which include 47 high-mass sources and 15 low-mass sources.
Therefore the detection rate is 38% for high-mass outflow sources and 9% for
low-mass outflow sources, suggesting that class I methanol maser is relatively
easily excited in high-mass sources. There are 37 newly detected 95 GHz
methanol masers (including 27 high-mass and 10 low-mass sources), 19 of which
are newly identified (i.e. first identification) class I methanol masers
(including 13 high-mass and 6 low-mass sources). Statistical analysis for the
distributions of maser detections with the outflow parameters reveals that the
maser detection efficiency increases with outflow properties (e.g. mass,
momentum, kinetic energy and mechanical luminosity of outflows etc.).
Systematic investigations of relationships between the intrinsic luminosity of
methanol maser and the outflow properties (including mass, momentum, kinetic
energy, bolometric luminosity and mass loss rate of central stellar sources)
indicate a positive correlations. This further supports that class I methanol
masers are collisionally pumped and associated with shocks, where outflows
interact with the surrounding ambient medium.Comment: 32 pages, 5 figures, accepted by Ap
Multi-epoch, multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A
We present the observational results of the Gamma-ray blazar, 3C 66A, at 2.3,
8.4, and 22 GHz at 4 epochs during 2004-05 with the VLBA. The resulting images
show an overall core-jet structure extending roughly to the south with two
intermediate breaks occurring in the region near the core. By model-fitting to
the visibility data, the northmost component, which is also the brightest, is
identified as the core according to its relatively flat spectrum and its
compactness. As combined with some previous results to investigate the proper
motions of the jet components, it is found the kinematics of 3C 66A is quite
complicated with components of inward and outward, subluminal and superluminal
motions all detected in the radio structure. The superluminal motions indicate
strong Doppler boosting exists in the jet. The apparent inward motions of the
innermost components last for at least 10 years and could not be caused by
new-born components. The possible reason could be non-stationarity of the core
due to opacity change.Comment: 24 pages, 4 figure
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