153 research outputs found
Estimation of Phonon Dispersion Relations Using Correlation Effects Among Thermal Displacements of Atoms
Neutron diffraction measurement of powder α-Fe sample at 295 K was carried out at the high resolution powder diffractometer installed at Japan Proton Accelerator Research Complex (J-PARC). Crystal parameters were determined from Rietveld analysis. The correlation effects among thermal displacements of atoms were estimated from a generalized equation based on the results of fomer diffuse scattering analysis. The force constants among atoms were obtained using an equation for transforming of the correlation effects to force constants. The force constants and the crystal structure of α-Fe were used to estimate the phonon dispersion relations, phonon density of states, and specific heat by computer simulation. The obtained force constants among first-nearest-neighboring atoms is 2.3 eV/Å2 at 295 K and the specific heat is 185 meV/K at 150 K. The calculated phonon dispersion relations and specific heat of α-Fe are similar to those obtained from inelastic neutron scattering and specific heat measurements, respectively. Received: 04 October 2014; Revised: 22 January 2015; Accepted: 30 March 201
Thermal denaturation of A-DNA
The DNA molecule can take various conformational forms. Investigations
focus mainly on the so-called ‘B-form’, schematically drawn in the famous
paper by Watson and Crick [1]. This is the usual form of DNA in a biological
environment and is the only form that is stable in an aqueous environment.
Other forms, however, can teach us much about DNA. They have the same
nucleotide base pairs for ‘building blocks’ as B-DNA, but with different
relative positions, and studying these forms gives insight into the interactions
between elements under conditions far from equilibrium in the B-form.
Studying the thermal denaturation is particularly interesting because it provides
a direct probe of those interactions which control the growth of the
fluctuations when the ‘melting’ temperature is approached. Here we report
such a study on the ‘A-form’ using calorimetry and neutron scattering. We
show that it can be carried further than a similar study on B-DNA, requiring
the improvement of thermodynamic models for DNA
Derivation of Inter-Atomic Force Constants of Cu2O From Diffuse Neutron Scattering Measurement
Neutron scattering intensity from Cu2O compound has been measured at 10 K and 295 K with High Resolution Powder Diffractometer at JRR-3 JAEA. The oscillatory diffuse scattering related to correlations among thermal displacements of atoms was observed at 295 K. The correlation parameters were determined from the observed diffuse scattering intensity at 10 and 295 K. The force constants between the neighboring atoms in Cu2O were estimated from the correlation parameters and compared to those of Ag2O.Received: 16 January 2013; Revised: 10 April 2013; Accepted: 15 April 201
Di-electron and two-photon widths in charmonium
The vector and pseudoscalar decay constants are calculated in the framework
of the Field Correlator Method. Di-electron widths:
keV, keV,
keV, in good agreement with experiment, are obtained with the same coupling,
, in QCD radiative corrections. We show that the larger
is needed to reach agreement with experiment for
keV, keV, keV, and
also for keV,
keV. Meanwhile even larger gives rise to good description of
keV, keV, and
provides correct ratio of the branching fractions: Comment: 8 pages, no figure
and transition form factor revisited
In light of recent experimental results, we revisit the dispersive analysis
of the decay amplitude and of the transition
form factor. Within the framework of the Khuri-Treiman equations, we show that
the Dalitz-plot parameters obtained with a once-subtracted
amplitude are in agreement with the latest experimental determination by
BESIII. Furthermore, we show that at low energies the transition
form factor obtained from our determination of the amplitude
is consistent with the data from MAMI and NA60 experiments
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