7 research outputs found
Multiple-charge transfer and trapping in DNA dimers
We investigate the charge transfer characteristics of one and two excess
charges in a DNA base-pair dimer using a model Hamiltonian approach. The
electron part comprises diagonal and off-diagonal Coulomb matrix elements such
a correlated hopping and the bond-bond interaction, which were recently
calculated by Starikov [E. B. Starikov, Phil. Mag. Lett. {\bf 83}, 699 (2003)]
for different DNA dimers. The electronic degrees of freedom are coupled to an
ohmic or a super-ohmic bath serving as dissipative environment. We employ the
numerical renormalization group method in the nuclear tunneling regime and
compare the results to Marcus theory for the thermal activation regime. For
realistic parameters, the rate that at least one charge is transferred from the
donor to the acceptor in the subspace of two excess electrons significantly
exceeds the rate in the single charge sector. Moreover, the dynamics is
strongly influenced by the Coulomb matrix elements. We find sequential and pair
transfer as well as a regime where both charges remain self-trapped. The
transfer rate reaches its maximum when the difference of the on-site and
inter-site Coulomb matrix element is equal to the reorganization energy which
is the case in a GC-GC dimer. Charge transfer is completely suppressed for two
excess electrons in AT-AT in an ohmic bath and replaced by damped coherent
electron-pair oscillations in a super-ohmic bath. A finite bond-bond
interaction alters the transfer rate: it increases as function of when
the effective Coulomb repulsion exceeds the reorganization energy (inverted
regime) and decreases for smaller Coulomb repulsion
Signatures of two-dimensionalisation of 3D turbulence in presence of rotation
A reason has been given for the inverse energy cascade in the
two-dimensionalised rapidly rotating 3D incompressible turbulence. For such
system, literature shows a possibility of the exponent of wavenumber in the
energy spectrum's relation to lie between -2 and -3. We argue the existence of
a more strict range of -2 to -7/3 for the exponent in the case of rapidly
rotating turbulence which is in accordance with the recent experiments. Also, a
rigorous derivation for the two point third order structure function has been
provided helping one to argue that even with slow rotation one gets, though
dominated, a spectrum with the exponent -2.87, thereby hinting at the
initiation of the two-dimensionalisation effect with rotation.Comment: An extended and typos-corrected version of the earlier submissio