413 research outputs found
A Microscopic Mechanism for Muscle's Motion
The SIRM (Stochastic Inclined Rods Model) proposed by H. Matsuura and M.
Nakano can explain the muscle's motion perfectly, but the intermolecular
potential between myosin head and G-actin is too simple and only repulsive
potential is considered. In this paper we study the SIRM with different complex
potential and discuss the effect of the spring on the system. The calculation
results show that the spring, the effective radius of the G-actin and the
intermolecular potential play key roles in the motion. The sliding speed is
about calculated from the model which well agrees with
the experimental data.Comment: 9 pages, 6 figure
Tetrahedrally bonded ternary amorphous semiconductor alloys
The properties of tetrahedrally bonded ternary amorphous semiconductors a-CSiSn:H and a-CSiGe:H are reviewed with particular emphasis on the temperature dependence of dark conductivity and the coordination in random networks. It is shown here that the dark conductivity as a function of the temperature strongly depends on the carbon content and, more precisely, on the proportion of sp3 and sp2 sites in the carbon. Ternary alloys with different carbon contents are compared to binary alloys using the average coordination number. The ternary alloys have an average coordination number close to the optimal value predicted for amorphous covalent networks
Ab-Initio Calculation of Molecular Aggregation Effects: a Coumarin-343 Case Study
We present time-dependent density functional theory (TDDFT) calculations for
single and dimerized Coumarin-343 molecules in order to investigate the quantum
mechanical effects of chromophore aggregation in extended systems designed to
function as a new generation of sensors and light-harvesting devices. Using the
single-chromophore results, we describe the construction of effective
Hamiltonians to predict the excitonic properties of aggregate systems. We
compare the electronic coupling properties predicted by such effective
Hamiltonians to those obtained from TDDFT calculations of dimers, and to the
coupling predicted by the transition density cube (TDC) method. We determine
the accuracy of the dipole-dipole approximation and TDC with respect to the
separation distance and orientation of the dimers. In particular, we
investigate the effects of including Coulomb coupling terms ignored in the
typical tight-binding effective Hamiltonian. We also examine effects of orbital
relaxation which cannot be captured by either of these models
An Upper Bound on the Decay tau -> mu gamma from Belle
We have performed a search for the lepton-flavor-violating decay tau -> mu
gamma using a data sample of 86.3fb^{-1} accumulated by the Belle detector at
KEK. No evidence for a signal is seen, and we set an upper limit for the
branching fraction of B(tau -> mu gamma) < 3.1 x 10^{-7} at the 90% confidence
level.Comment: 6 pages, 4 figuresm, submitted to Phys. Rev. Let
Measurement of Time-Dependent CP-Violating Asymmetries in B0 --> phi Ks0, K+ K- Ks0, and eta' Ks0 Decays
We present an improved measurement of CP-violation parameters in B0 --> phi
Ks0, K+ K- Ks0, and eta' Ks0 decays based on a 140 fb-1 data sample collected
at the Upsilon(4S) resonance with the Belle detector at the KEKB
energy-asymmetric e+e- collider. One neutral B meson is fully reconstructed in
one of the specified decay channels, and the flavor of the accompanying B meson
is identified from its decay products. CP-violation parameters for each of the
three modes are obtained from the asymmetries in the distributions of the
proper-time intervals between the two B decays. We find that the observed CP
asymmetry in the B0 --> phi Ks0 decay differs from the standard model (SM)
expectation by 3.5 standard deviations, while the other cases are consistent
with the SM.Comment: 10 pages, 4 postscript figures, submitted to Physical Review Letters,
also contributed to the XXI International Symposium on Lepton and Photon
Interactions at High Energies, Aug 11-16, 2003, Fermilab, Illinois US
Measurements of the resonance properties
We report measurements of the properties of the and
resonances produced in continuum annihilation near
. The analysis is based on an data sample collected %at and 60 MeV below the
resonance with with the Belle detector at KEKB. We determine the masses to be
and . We observe the radiative decay mode
and the dipion decay mode , and determine their branching fractions. No corresponding
decays are observed for the state. These results are consistent
with the spin-parity assignments of for the and for
the .Comment: 5 pages, 6 figures; Added content, updated and paper submitted to PR
Observation of
We report the first observation of the flavor-changing neutral current decay
and an improved measurement of the decay , where represents an electron or a muon, with a data
sample of 140 fb accumulated at the resonance with the
Belle detector at KEKB. The results for the branching fractions are and
, where the first error is statistical, the second is systematic and
the third is from model dependence.Comment: 11 pages, 2 figures, submitted to PR
Observation of the DsJ(2317) and DsJ(2457) in B decays
We report the first observation of the B --> Dbar DsJ(2317) and B --> Dbar
DsJ(2457) decays based on 123.8 10^6 BBar events collected with the Belle
detector at KEKB. We observe the DsJ(2317) decay to Ds pi0 and DsJ(2457) decay
to the Ds* pi0 and Ds gamma final states. We also set 90% CL upper limits for
the decays DsJ(2317) --> Ds* gamma, DsJ(2457) --> Ds* gamma, DsJ(2457) --> Ds
pi0 and DsJ(2457) --> Ds pi+ pi-.Comment: 6 pages, 3 figures. A few minor corrections. Replaced by version
accepted to publication in Phys. Rev. Let
Evidence for B0->pi0pi0
We report evidence for the decay B0->pi0pi0. The analysis is based on a data
sample of 152million BBbar pairs collected at the Upsilon(4s) resonance with
the Belle detector at the KEKB e+e- storage ring. We find
25.6+9.3/-8.4(stat)+1.6/-1.4(syst) B0->pi0pi0 signal events with a significance
of 3.4 standard deviations. We measure the branching fraction to be
(1.7+-0.6(stat)+-0.2(syst))*10^{-6}.Comment: Submitted to PR
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