719 research outputs found
Generalized wordlength patterns and strength
Xu and Wu (2001) defined the \emph{generalized wordlength pattern} of an arbitrary fractional factorial design (or orthogonal array) on
factors. They gave a coding-theoretic proof of the property that the design
has strength if and only if . The quantities are
defined in terms of characters of cyclic groups, and so one might seek a direct
character-theoretic proof of this result. We give such a proof, in which the
specific group structure (such as cyclicity) plays essentially no role.
Nonabelian groups can be used if the counting function of the design satisfies
one assumption, as illustrated by a couple of examples
Olaparib treatment for BRCA-mutant ovarian cancer with leptomeningeal disease
HIGHLIGHTS: Leptomeningeal disease occurs more commonly in BRCA-mutated ovarian cancer; A clinically significant dose of olaprib is able to penetrate the leptomeninges; Leptomeningeal metastases in a BRCA-mutated ovarian cancer responded to olaparib
Kondo effect in a one dimensional d-wave superconductor
We derive a solvable resonant-level type model, to describe an impurity spin
coupled to zero-energy bound states localized at the edge of a one dimensional
d-wave superconductor. This results in a two-channel Kondo effect with a quite
unusual low-temperature thermodynamics. For instance, the local impurity
susceptibility yields a finite maximum at zero temperature (but no
logarithmic-divergence) due to the splitting of the impurity in two Majorana
fermions. Moreover, we make comparisons with the Kondo effect occurring in a
two dimensional d-wave superconductor.Comment: 9 pages, final version; To be published in Europhysics Letter
The kink Casimir energy in a lattice sine-Gordon model
The Casimir energy of quantum fluctuations about the classical kink
configuration is computed numerically for a recently proposed lattice
sine-Gordon model. This energy depends periodically on the kink position and is
found to be approximately sinusoidal.Comment: 10 pages, 4 postscript figure
Theory of anomalous magnetic interference pattern in mesoscopic SNS Josephson junctions
The magnetic interference pattern in mesoscopic SNS Josephson junctions is
sensitive to the scattering in the normal part of the system. In this paper we
investigate it, generalizing Ishii's formula for current-phase dependence to
the case of normal scattering at NS boundaries in an SNS junction of finite
width. The resulting flattening of the first diffraction peak is consistent
with experimental data for S-2DEG-S mesoscopic junctions.Comment: 6 pages, 5 figures. Phys. Rev. B 68, 144514 (2003
Inhomogeneously doped two-leg ladder systems
A chemical potential difference between the legs of a two-leg ladder is found
to be harmful for Cooper pairing. The instability of superconductivity in such
systems is analyzed by compairing results of various analytical and numerical
methods. Within a strong coupling approach for the t-J model, supplemented by
exact numerical diagonalization, hole binding is found unstable beyond a
finite, critical chemical potential difference. The spinon-holon mean field
theory for the t-J model shows a clear reduction of the the BCS gaps upon
increasing the chemical potential difference leading to a breakdown of
superconductivity. Based on a renormalization group approach and Abelian
bosonization, the doping dependent phase diagram for the weakly interacting
Hubbard model with different chemical potentials was determined.Comment: Revtex4, 11 pages, 7 figure
Nonlocality in mesoscopic Josephson junctions with strip geometry
We study the current in a clean superconductor-normal-metal-superconductor
junction of length d and width w in the presence of an applied magnetic field
H. We show that both the geometrical pattern of the current density and the
critical current as a function of the total flux in the junction, depend on the
ratio of the Josephson vortex distance a_0 and the range r of the nonlocal
electrodynamics. In particular, the critical current has the periodicity of the
superconducting flux quantum only for r<a_0 and acquires, due to boundary
effects, the double (pseudo-) periodicity for strong nonlocality, r>a_0.
Comparing our results to recent experiments of Heida et al. [Phys. Rev. B 57,
R5618 (1998)] we find good agreement.Comment: 4 pages, 5 figures, to be published in the RC section of Phys. Rev.
Successive opening of the Fermi surface in doped N-leg Hubbard ladders
We study the effect of doping away from half-filling in weakly (but finitely)
interacting N-leg Hubbard ladders using renormalization group and bosonization
techniques. For a small on-site repulsion U, the N-leg Hubbard ladders are
equivalent to a N-band model, where at half-filling the Fermi velocities are
v_{1}=v_{N}<v_{2}=v_{N-1}<... We then obtain a hierarchy of energy-scales,
where the band pairs (j,N+1-j) are successively frozen out. The low-energy
Hamiltonian is then the sum of N/2 (or (N-1)/2 for N odd) two-leg ladder
Hamiltonians without gapless excitations (plus a single chain for N odd with
one gapless spin mode), similar to the N-leg Heisenberg spin-ladders. The
energy-scales lead to a hierarchy of gaps. Upon doping away from half-filling,
the holes enter first the band(s) with the smallest gap: For odd N, the holes
enter first the nonbonding band (N+1)/2 and the phase is a Luttinger liquid,
while for even N, the holes enter first the band pair (N/2,N/2+1) and the phase
is a Luther-Emery liquid, similar to numerical treatments of the t-J model,
i.e., at and close to half-filling, the phases of the Hubbard ladders for small
and large U are the same. For increasing doping, hole-pairs subsequently enter
at critical dopings the other band pairs (j,N+1-j) (accompanied by a diverging
compressibility): The Fermi surface is successively opened by doping, starting
near the wave vector (pi/2,pi/2). Explicit calculations are given for the cases
N=3,4.Comment: 10 pages, 4 figures, to be published in Phys. Rev.
Blinking statistics of a molecular beacon triggered by end-denaturation of DNA
We use a master equation approach based on the Poland-Scheraga free energy
for DNA denaturation to investigate the (un)zipping dynamics of a denaturation
wedge in a stretch of DNA, that is clamped at one end. In particular, we
quantify the blinking dynamics of a fluorophore-quencher pair mounted within
the denaturation wedge. We also study the behavioural changes in the presence
of proteins, that selectively bind to single-stranded DNA. We show that such a
setup could be well-suited as an easy-to-implement nanodevice for sensing
environmental conditions in small volumes.Comment: 14 pages, 5 figures, LaTeX, IOP style. Accepted to J Phys Cond Mat
special issue on diffusio
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